Print Page | Close Window

Bad Ideas

Printed From: Official Baja SAE Forums
Category: General
Forum Name: Design Discussion
Forum Description: Discuss Design, Tech, Cost, and related issues
URL: http://forums.bajasae.net/forum/forum_posts.asp?TID=507
Printed Date: Mar/28/2024 at 9:36am


Topic: Bad Ideas
Posted By: RonGeorge
Subject: Bad Ideas
Date Posted: Sep/27/2010 at 11:15pm
Flexible Ring Chain Tensioners

DO NOT attempt this method of tensioning for an off-road vehicle where the driven end is a 100 pound unsprung mass running on a heavy motorcycle chain. Its a quick trip to failure and like some of our team members say, it may make you want to punch babies. The tensioner is made up of a specially formulated polymer whose teeth are eaten up pretty quickly by the chain. It also falls out of place as the chain stretches with load/unload cycles frequented in mini baja.

The makers of this product, Renold, make a tiny comment in their brochure for self aggrandizement I suppose - "Roll-Rings have even been installed successfully on Quad bikes/buggies". We do not support this claim, after a season of bad experiences. I was pleased with its easy installation but that's all I can give it credit for. They do have nice videos of it running on printing and conveying machines, where I can see the reason for its reliability. Show me a pair of these ring tensioners in a baja car making it through a 4 hour endurance race on a motorcross track and I may change my views.




Feel free to contribute to expand on this knowledge of other failed ideas. Pics will be nice.



-------------
-Ron George
Systems Engineer (Cummins Turbo)



Replies:
Posted By: blue2kss
Date Posted: Sep/27/2010 at 11:58pm
Three years ago when our custom transmission case wasn't machined in time we had to revert to the stock case where the output shaft wasn't in line with the pivot of the swing arm anymore.  We had to run a makeshift tensioner to keep the chain tight throughout its travel.  Had to do it on the road and ended up using a hand clamp spring, skateboard wheel and other various bits of metal and welded it to the swing arm.  The damn thing worked like a charm.  Cant find any pics of it (ill try harder tomorrow) because it looked so hacked together and was hidden under the chain guard.  

-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: blue2kss
Date Posted: Sep/28/2010 at 12:03am
But as far as other ideas that dont work very well - wings (the concept was there and it did what it was supposed to very well, but would get hung up on trees something awful, and forget the water maneuverability or event with a breeze lol), push button electronic shift (mud made them useless at Auburn two years ago), epoxied gas tank posts to hold the gas tank in place in the quick removal system (just weld them), and air shift (leaks, and pit changes just add time, mud in the actuator, etc).

The paddle shift would have worked much better with simple push/pull cables and the right lever ratios




-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: ErikHardy
Date Posted: Sep/28/2010 at 12:49am
Dustin, the theory on the wing was to balance the car on jumps correct?


Posted By: blue2kss
Date Posted: Sep/28/2010 at 9:56pm
Originally posted by ErikHardy ErikHardy wrote:

Dustin, the theory on the wing was to balance the car on jumps correct?


Erik,

Yes, that was the point.  We nose dived over many of the motocross track jumps because we just don't go fast enough to hit them they way they were meant to be hit.  Even though I was a major proponent against the wing since its inception, one of my favorite memories was my first year on the team.  We pulled the car out at RIT and almost everyone was laughing, snickering etc.  But when we were getting the Mike Schmidt award they were playing a slide show of the race and there were pictures of us taking jumps that everyone else was rolling.  My favorite was us completely jumping over another car.  The wing made a 30 degree difference over the car without it at full speed, and gave us a 100 lb torque around the CG of the vehicle.  Hell, we even did a smoke test to see where exactly we needed to put it back there, and did a whole bunch of calcs to determine how big that sucker needed to be to get the down force that we wanted.  Ended up being 8 ft^2 and 33 lbs of force 3' back from the CG.  We benefited most from the wing at the RIT race out of all the races we ran it at.

There are other ways that you can get around the problem of course by slowing down the rebound in the shocks which we used to do, but then its not what we considered optimal around the rest of the track when much of our time was not spent in the air.  Its a trade off that we decided to try out (for a few races then I said no more) and we had mixed results.  In South Dakota our driver Kevin was absolutely flying and was a lap or two up, nailed the car on a tree in mid air and not only took out the wing but also severely bent one of the frame tube members.  Luckily the tech inspector didn't notice the frame and let us go on.  We made it all back up, but that wing cost us the endurance race win where I believe Queens came in first (don't quote me on that), and had the race been 100 yards longer that might have changed.


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: johnfar109
Date Posted: Sep/29/2010 at 12:04am
Originally posted by blue2kss blue2kss wrote:



We made it all back up, but that wing cost us the endurance race win where I believe Queens came in first (don't quote me on that), and had the race been 100 yards longer that might have changed.


RIT ended up wining that enduro. and you are right about the 100 yard part. in a 4 hr race we only won by 68.742 sec (Times from MYLaps.com) with Queens back 107.234 Sec from USF.  That race was a nail biter.

I was standing next to the Black flag area listening to the Race control radio. a Call went out form Jason that "the wing must be on the car". a lap or two later i hear Jason on the radio come on and say "well that wasin't what i was thinking but i guess it works." 30 seconds later i see the car go by with the wing on the roof held down with duck tape if i remember.

i Know for a fact if that race was one lap longer USF would have won. first because they where turning faster laps at that point. second our engine was out of oil .... to the point where brigs asked us to put oil in the engine to do the engine check. lastly because when i took the CVT cover off for post race inspection i dumped out the oil that was so-post to be in the engine out of the area around the CVT. a spacer had destroyed the crank seal.

USF kicked our butt a few weeks later at our home track and the wing had a lot to do with that.

It all comes back to one point the only "bad idea" is the idea that never gets tried. There is stuff that was run on everyone car that was in the "bad idea"  pile at one point. maybe we should call this "Things that didn't work out"


-------------
- John Farnach

RIT BAJA SAE

That Guy 04-09'

RIT 2010 Maneuverability Captain & Track Prep and Construction
RIT 2013, 2016, 2019 Electronic Scoring & Track Prep and Construction


Posted By: blue2kss
Date Posted: Sep/29/2010 at 12:51am
John,

I'm glad someone remembered that race.  Jason tried to give us a ton of sh*t afterward, but he did laugh and say that what we did was "ok" after some friendly debate.  I really wish I was there to hear exactly what he said though.  When we were putting it back on the car the only thing that our president at the time managed to bring from the pit area was duct tape and some monster AC zip ties.  Used almost the whole roll if i remember correctly

Oh man, good times


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: RonGeorge
Date Posted: Sep/29/2010 at 8:10am
The wing prevents roll?  Perhaps that's what the Segway needs. http://motorcycles.about.com/b/2010/09/29/segway-company-owner-dies-on-a-segway.htm - http://motorcycles.about.com/b/2010/09/29/segway-company-owner-dies-on-a-segway.htm



-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: collinskl1
Date Posted: Sep/29/2010 at 10:32am
This one has become a running joke with our team, because every year there is atleast one person that suggests it when the design discussion begins for floatation:
 
"Why don't we just fill the frame tubes with foam?"
 
Surely our team isn't the only one plagued by this stupidity...


-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Red_Beard
Date Posted: Sep/29/2010 at 11:34am
Originally posted by collinskl1 collinskl1 wrote:

This one has become a running joke with our team, because every year there is atleast one person that suggests it when the design discussion begins for floatation:
 
"Why don't we just fill the frame tubes with foam?"
 
Surely our team isn't the only one plagued by this stupidity...


I've always been a proponent of filling the tires with helium or something like thatLOL


-------------
SDSM&T 09-10 Team Lead
2nd & 9th Baja West

Project Engineer
Matrix Service - Bellingham, WA


Posted By: collinskl1
Date Posted: Sep/29/2010 at 12:10pm
There's always some import fanboy at the first meeting that asks if we can turbo the motor too.

-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Rob71zilla
Date Posted: Sep/29/2010 at 12:31pm
We wanted to fill the frame with hydrogen last year Thumbs Up

-------------
Robbie
Former Team Captain
SUNY Institute of Technology
Current Engineer for Remington Arms

A Redline a day keeps the carbon away.


Posted By: Red_Beard
Date Posted: Sep/29/2010 at 4:24pm
Originally posted by Rob71zilla Rob71zilla wrote:

We wanted to fill the frame with hydrogen last year Thumbs Up


We thought about that tooClap


-------------
SDSM&T 09-10 Team Lead
2nd & 9th Baja West

Project Engineer
Matrix Service - Bellingham, WA


Posted By: YonkersBaja
Date Posted: Sep/29/2010 at 5:04pm
Did anyone get the, "can we put nitrous on that bad boy" question? We keep on getting that and then when we make them read the rulebook, they come back with the idea of making one of the frame members into a nitrous tank so it is "hidden"................................................really?


Posted By: Tantum
Date Posted: Sep/29/2010 at 5:33pm
Yes, we get that too.

"Let's put a 3" tube at the bottom of the firewall so we can hide nitrous in there"

Yeah, sounds great, until you land wrong on a big rock and the driver gets cannoned from the car from the giant explosion under his ass.


-------------
~ Nick


Posted By: Moreau
Date Posted: Sep/29/2010 at 6:08pm
Yeah, turbos and nitrous, and why we won't get away with either are pretty much the first meeting's topics of discussion.

Back to the idea of "bad ideas that have been implemented," try severe reverse ackermann and a 30/70 F/R weight distribution.  With a driver.  Don't ask.  We're trying to forget.

Also, a successful bad idea: staggered front/rear trackwidths.  Great way to increase roll stiffness in the rear to an absurd degree (and can help a spool handle really damn well), good enough for a 62 second first run at SC (curse you rod ends!!).  But once you add ruts to the road surface...  just think of what happens when the front and rear wheels try to align despite a 3" stagger when you're already on 3 wheels turning.  I think JHU was the only team to nearly flip over on maneuverability (of all things) at RIT on our second run.



-------------
Hopkins Baja
Johns Hopkins University
Chemical and Biomolecular Engineering 2012


Posted By: wishin4snow
Date Posted: Sep/29/2010 at 8:18pm
I love reading the ideas people give at some of the first meetings. I can totally relate. This sounds like a topic of discussion all on its own.

-------------
-Kevin
Pennsylvania College of Technology

"Hold 'er dubya"


Posted By: RonGeorge
Date Posted: Sep/29/2010 at 9:48pm
I remember a conversation with a student before June. When I initially talked to him about the RIT water competition and how we should have flotation foam to be rendered amphibious, he rejected the entire idea of strapping foam on the car. His solution instead was for the driver dive into the water at full speed with the car so as to try and skim the surface of the water with the wheels so we could cross the pond (like how the snow mobiles do it). He said we would be able to do that inspite of me repeatedly telling him that our 10HP motor pushing along a 600 pound vehicle will barely manage anything like the stunt he was describing so happily. He kept saying "try it...try it... you guys should do that... try it....".  He never joined the Baja team. 

-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: CLReedy21
Date Posted: Sep/30/2010 at 7:02am
Originally posted by YonkersBaja YonkersBaja wrote:

Did anyone get the, "can we put nitrous on that bad boy" question? We keep on getting that and then when we make them read the rulebook, they come back with the idea of making one of the frame members into a nitrous tank so it is "hidden"................................................really?


4 years ago we had a Briggs Tech jokingly suggest we do just that...as he was teching our engine :)

My favorite question the I love fielding at the public events is "How deep of water will that thing float in?" or "What are them orange boxes on the sides up there at the front?"


-------------
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."


Posted By: collinskl1
Date Posted: Sep/30/2010 at 7:58am
Originally posted by CLReedy21 CLReedy21 wrote:



My favorite question the I love fielding at the public events is "How deep of water will that thing float in?"
 
Trying to explain that to people has caused me so much grief.  I tell them that it's like a boat you can drive.  Then they re-ask the question, and I generally respond with how deep of water will your fishing boat float in? 
 
They walk away scratching their heads everytime.


-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Rob71zilla
Date Posted: Sep/30/2010 at 10:14am
Our Wisconsin car used a steering setup from a sport quad.  It was a direct connection between the tie rods and the steering column.  That alone was a bad idea but even worse was how we mounted it.  The piece that the tie rods connect to was mounted backwards so that when we turned the wheel to the left, the wheels turned right Censored 
 
We had absolutly 0 testing on that car and we realized the problem during final assembly which was the afternoon before we had to leave.  It goes without saying that it made for a long night, but we were able to fabricate a new steering set up and made it to competition.


-------------
Robbie
Former Team Captain
SUNY Institute of Technology
Current Engineer for Remington Arms

A Redline a day keeps the carbon away.


Posted By: collinskl1
Date Posted: Sep/30/2010 at 10:15am
Originally posted by wishin4snow wishin4snow wrote:

I love reading the ideas people give at some of the first meetings. I can totally relate. This sounds like a topic of discussion all on its own.
 
new thread in the lounge:
 
http://forums.bajasae.net/forum/topic510_post5954.html#5954 - http://forums.bajasae.net/forum/topic510_post5954.html#5954


-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: CobraCommander
Date Posted: Sep/30/2010 at 11:52am
How about running a manual and a differential... and bury them in the frame somewhere so that its only possible to remove them engine ->trans->diff... Major PITA to work on and super heavy we're estimating that we'll lose a good chunk of weight off the driveline by switching to a cvt and double reduction gearbox...
 
Also since our school has a woodworking program really illustrates the different construction techniques required for different materials... They always want to solve every problem with a increasingly larger hammer... Not that there isn't a time and a place for it...


-------------
COBRA Team Captain


Posted By: dillon_b12
Date Posted: Sep/30/2010 at 12:56pm
We were outside the shop trying to get one of the cars to start one day when a random student walked by and explained that he "...worked on these things all the time, believe it or not."  and that the way to fix it was "You gotta bore out that carburetor!".


Posted By: collinskl1
Date Posted: Sep/30/2010 at 1:21pm
Originally posted by CobraCommander CobraCommander wrote:

How about running a manual and a differential... and bury them in the frame somewhere so that its only possible to remove them engine ->trans->diff... Major PITA to work on and super heavy we're estimating that we'll lose a good chunk of weight off the driveline by switching to a cvt and double reduction gearbox...
 
 
That reminds me of our past transmission design.  It was 2 quarter inch plates spaced about 5 inches apart with frame tube.  It located steel bearing housings, shafts, sprockets, chain, as well as doubling as our engine mount... so to work on it or remove it, we had to take the engine off and then drop the box.  Or we could try to take the entire package out as one... but that only weighed 80 or 90ish pounds...  and it had to come out the top of the car.


-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Pancho.
Date Posted: Sep/30/2010 at 1:42pm
Originally posted by YonkersBaja YonkersBaja wrote:

Did anyone get the, "can we put nitrous on that bad boy" question? We keep on getting that and then when we make them read the rulebook, they come back with the idea of making one of the frame members into a nitrous tank so it is "hidden"................................................really?
 
New members usually bring up the nitrous question but it sounds more like this.
"Can we put NOS on it??!?!?!?!"


-------------
Spenser Karns
Penn State Altoona Motorsports
One Does Not simply walk into mordor.


Posted By: ErikHardy
Date Posted: Oct/01/2010 at 9:04pm
Originally posted by blue2kss blue2kss wrote:

Originally posted by ErikHardy ErikHardy wrote:

Dustin, the theory on the wing was to balance the car on jumps correct?


Erik,

Yes, that was the point.  We nose dived over many of the motocross track jumps because we just don't go fast enough to hit them they way they were meant to be hit.  Even though I was a major proponent against the wing since its inception, one of my favorite memories was my first year on the team.  We pulled the car out at RIT and almost everyone was laughing, snickering etc.  But when we were getting the Mike Schmidt award they were playing a slide show of the race and there were pictures of us taking jumps that everyone else was rolling.  My favorite was us completely jumping over another car.  The wing made a 30 degree difference over the car without it at full speed, and gave us a 100 lb torque around the CG of the vehicle.  Hell, we even did a smoke test to see where exactly we needed to put it back there, and did a whole bunch of calcs to determine how big that sucker needed to be to get the down force that we wanted.  Ended up being 8 ft^2 and 33 lbs of force 3' back from the CG.  We benefited most from the wing at the RIT race out of all the races we ran it at.

 
Dustin,
Any pictures of the smoke test? If not, any surprises by the firewall or anything else of the matter?
I'm not an aero guy to say the least but I must admit I am surprised how much the wing helped at such low speeds in the air.


Posted By: RonGeorge
Date Posted: Oct/01/2010 at 10:08pm
@ErikHardy & @Dustin

Flight in the air (or lack of) is strongly related of angle of attack of the wings, surface area of the wings, density of air and velocity.

I too am very suspicious of the TRUE usability of wings in a baja car that is dragging around a puny lawnmover motor that rarely manages its top speed potential in an endurance event. More importantly, fluid flow is affected by what it has to encounter. Air is a fluid. If you get a turbulent mess of air above your firewall, or roof, will it do anything appreciable when it meets the wings? I suspect you can achieve the same "downforce" in better ways. Put a 200 lb driver in the car. Are you scared your car will break with a heavier driver? Than why design it in the first place? Do we expect the fictitious "weekend recreationalist" to be always sub 150 pounds? Interesting nevertheless that these wings were made in the first place. The tradeoff was that it broke when it hit a tree. Thats not sensible design.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: ErikHardy
Date Posted: Oct/01/2010 at 11:01pm
Ron, I'm not sure what your last few sentences are about but I'm fairly certain it has to do with nothing that was brought up. I would expect that a heavier driver would hardly affect the balance of the vehicle while upon takeoff and in flight.


Posted By: RonGeorge
Date Posted: Oct/01/2010 at 11:36pm
Originally posted by ErikHardy ErikHardy wrote:

Ron, I'm not sure what your last few sentences are about but I'm fairly certain it has to do with nothing that was brought up. I would expect that a heavier driver would hardly affect the balance of the vehicle while upon takeoff and in flight.


The weight and "downforce" comment was meant to be tongue in cheek.  But anyway, weight in the car and how its distributed longitudinally on a car must have an effect on how the car behaves in the air, along with your control of the car's pitch through throttle and braking. If you build an rc car out of brake lines and put a lead ball more towards the front of the car, observe how the car pitches. The wing IMO, even if observed to work somehow, seems to be a bad band-aid to a problem you could have fixed on the drawing board.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: JHrdy724
Date Posted: Oct/04/2010 at 4:31pm
Originally posted by RonGeorge RonGeorge wrote:



The weight and "downforce" comment was meant to be tongue in cheek.  But anyway, weight in the car and how its distributed longitudinally on a car must have an effect on how the car behaves in the air, along with your control of the car's pitch through throttle and braking.

changing the weight longitudinally to account for poor pitching on jumps does soothe some of the nose dive pain, but it comes at a cost in the maneuverability on the ground.  Do you want to design for your cars flight dynamics or ground control?  how often is the car even in the air?  its definitely something that is a balance issue like so many other baja issues, but sometimes a "bandaid"  to help one aspect is much more than it seems in another respect


-------------
There are three easy ways of losing money - racing is the quickest, women the most pleasant, and farming the most certain.
Lord Amherst


Posted By: blue2kss
Date Posted: Oct/05/2010 at 10:16pm
Originally posted by RonGeorge RonGeorge wrote:

Originally posted by ErikHardy ErikHardy wrote:

Ron, I'm not sure what your last few sentences are about but I'm fairly certain it has to do with nothing that was brought up. I would expect that a heavier driver would hardly affect the balance of the vehicle while upon takeoff and in flight.


The weight and "downforce" comment was meant to be tongue in cheek.  But anyway, weight in the car and how its distributed longitudinally on a car must have an effect on how the car behaves in the air, along with your control of the car's pitch through throttle and braking. If you build an rc car out of brake lines and put a lead ball more towards the front of the car, observe how the car pitches. The wing IMO, even if observed to work somehow, seems to be a bad band-aid to a problem you could have fixed on the drawing board.



Ron,

It certainly wasn't a band-aid to something that was poorly designed.  I take it you didn't read my comment earlier about how we used to manage the pitch during jumping...the wing concept was talked about for years before we put it into practice.  The year the wing was introduced we were sitting there in the shop and said hey, why not give it a try (if anything else itll give us some design changes for polaris since we did very well the previous year).  We knew the risks involved of sticking something with that much real estate on it where it would need to be to make a difference (ie breaking the damn thing off) and we still went for it.  Was it a success?  Depends on who you ask from our team still to this day who was there at the time, we will give you mixed reviews on it (I personally don't like it, but for the sake of debate ill let you know exactly how well it worked for what it was supposed to do).  The wing did a phenomenal job for what it was designed for, but there were certainly trade offs.  The typical USF concept of the 5 or 6 speed gearbox with swing arm always worked well.  The trade off of slowing your rebound down in the rear dampers to make up for pitch and heave was something we were tired of doing and added this change.  Of course distributing the weight on the car was an option, but we had the CG in what we considered the best location that we could manage to get it, the weight was down to what we wanted, and the wheel scales told us we had things pretty well ironed out.  This exact car won the Mike Schmidt award with the wing on for two races (wasn't done with testing at Ocala to run it there).

Attached are some pictures of the testing of the wing so everyone can see what difference it did make when it was still in one piece... no more nose or front wheel landings (after looking through my pictures that I still managed to salvage, I'm missing a lot of the car without the wing on these jumps, so you all will just have to deal with it.  The first two are taken from the design report for that year.)




































-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: blue2kss
Date Posted: Oct/05/2010 at 10:42pm
Originally posted by RonGeorge RonGeorge wrote:

@ErikHardy & @Dustin

Flight in the air (or lack of) is strongly related of angle of attack of the wings, surface area of the wings, density of air and velocity.


Sure is, and our spread sheet calculations were extensive with this...


Originally posted by RonGeorge RonGeorge wrote:

I too am very suspicious of the TRUE usability of wings in a baja car that is dragging around a puny lawnmover motor that rarely manages its top speed potential in an endurance event. More importantly, fluid flow is affected by what it has to encounter. Air is a fluid. If you get a turbulent mess of air above your firewall, or roof, will it do anything appreciable when it meets the wings? I suspect you can achieve the same "downforce" in better ways. Put a 200 lb driver in the car. Are you scared your car will break with a heavier driver? Than why design it in the first place? Do we expect the fictitious "weekend recreationalist" to be always sub 150 pounds? Interesting nevertheless that these wings were made in the first place. The tradeoff was that it broke when it hit a tree. Thats not sensible design.


The wing wasn't designed to be functional at only top speed...Im not even going to bother with the added weight comment, doesnt even contribute anything to the conversation. 

And as far as hitting a tree, yes it broke (and our roll hoop took an enormous beating too.  We were literally going mid twenties when he hit it).  Does this not make it sensible?  Debatable... Our suspension arms aren't made to smack a tree over a certain speed (low) and that's because we need to stay outta the trees.  Sometimes sh*t happens and you end up there, agreed.  I could design a tank that could survive a full blast hit with a redwood tree, but there lies the design trade off of weight vs. strength.  Would I recommend a team run a wing?  Nope, not after what we figured out, but half the team of that year would disagree with me still to this day




-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: blue2kss
Date Posted: Oct/05/2010 at 10:52pm
Originally posted by ErikHardy ErikHardy wrote:


Dustin,
Any pictures of the smoke test? If not, any surprises by the firewall or anything else of the matter?
I'm not an aero guy to say the least but I must admit I am surprised how much the wing helped at such low speeds in the air.


Erik,

I couldn't find any pictures of our smoke test, sorry.  The wing had to be that size amongst the other things that Ron pointed out to work at the low speeds we operate in. 


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: AndyRIT
Date Posted: Oct/05/2010 at 11:00pm

I think the wing was a great idea for a certain tracks, where it could be effectively used (such as RIT, Washougal and other fast, moto cross style tracks)  But at the same time a bad Idea for others (TTU track, SDSM and anyothers where there were low trees and a good chance of a roll)

 


-------------
RIT Baja SAE Alumni 04'-09'
RIT Baja Team Manager 06'-08'
2010 RIT Track builder
2011 CAT/IL Comp Team Leader
2012 Wis vol
2013 RIT Track Builder
Diesel Calibration Engineer-Kohler Engines


Posted By: ErikHardy
Date Posted: Oct/05/2010 at 11:04pm
Dustin,
Thanks for posting these, I am truly impressed. The wing was before my time in Baja so I missed out on the live running of the car. For having a SOLE purpose from keeping the car from nose diving, it sure appears it did its job and did it well.


Posted By: blue2kss
Date Posted: Oct/05/2010 at 11:49pm
Originally posted by AndyRIT AndyRIT wrote:

I think the wing was a great idea for a certain tracks, where it could be effectively used (such as RIT, Washougal and other fast, moto cross style tracks)  But at the same time a bad Idea for others (TTU track, SDSM and anyothers where there were low trees and a good chance of a roll)

 



Andy,

I totally agree.  Its just that it was most of our first years on that team and we didn't know what many of the tracks were like.  And unfortunately, you don't always get to see the endurance track before you can decide whether or not to run something like that.  We tried a removable system thing that would pass tech but didn't have time.  It was a fun project and idea that ended up not being the best thing for our type of racing.  Lesson learned...


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: RonGeorge
Date Posted: Oct/06/2010 at 12:39am
@Dustin,

Interesting , thanks for the reply. I can get a scale of the things by seeing it in the pictures provided. That wing is way over the proportions that I imagined it to be. To be clear, these images don't prove to me that in general, wings do effectively what they are theorized to do in a slow moving car. But if it worked for you, good. If you did something drastic to improve the safety of the drive for your driver, all the better.

Keep in mind that if you had avoided making a nose heavy vehicle in the first place, you wouldn't need a wing.  If you still couldn't avoid that situation, skillful drivers might have been able to correct that lingering problem by chopping the throttle in the air through precise timing. Few drivers are really talented to take a machine they're given to the extremes.

It just reinforces the idea in my mind that in general, wings are a bad idea. If everyday you'd be out in an open desert where you'd have no obstructions to worry about, maybe. But this is purported to be an off-road recreational car and as a designer, your goal is to make a sensible vehicle that has balanced performance on all terrain conditions at slow speeds of 30-35 mph. The added weight, possibility of increased drag at slow speeds on level ground (aerodynamics is not a a very intuitive branch of study)  , lack of maneuverability in a track with overgrowth and the ability to collect things and add further weight, such as a huge pile of snow in winter, tell me that tradeoffs are more than one or two advantages.

If this nose heavy phenomena happens to us in testing, we'll just have to try the wings.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: dillon_b12
Date Posted: Oct/06/2010 at 1:07am
Ron,

You are making an awful lot of assumptions about this particular USF car.  How do you know it was nose heavy?  Data from Alabama shows that our car was around a 45/55 weight distribution, and it didn't fly well.  Furthermore, the same data shows that there wasn't a single car at that competition that was over a 48/52 split w/ driver.  Unless you are defining nose-heavy in a different way, there wasn't one nose-heavy car there and they definitely didn't all fly well.

Case Western showed up with a car at Midnight Mayhem 2008 that could jump well, but they said it had somewhere around a 30/70 split, and it did a wheelie every time they let out the clutch on one of the hills.

USF has had some of the most talented drivers in the Baja SAE series.  If they could have corrected their jumping issues through a change in driving style, they would have.  IIRC, USF has a designated driver that does NOTHING but drive the car.  I could be wrong about that, but the fact remains that their drivers are highly trained.

IMO, there are a variety of factors that work against a Baja car when it comes to jumping well. Lack of power, weight distribution, spring rates, compression damping, rebound damping, course construction, and lack of driver training to name a few.  I don't think we can look at every Baja car that doesn't fly well and say it's just nose-heavy.


Posted By: Old Greg
Date Posted: Oct/06/2010 at 1:40am
Originally posted by dillon_b12 dillon_b12 wrote:

IIRC, USF has a designated driver that does NOTHING but drive the car.  I could be wrong about that, but the fact remains that their drivers are highly trained.


As much as Kevin is the Stig's knobbly-tired cousin, he wasn't a ringer. 

Well, maybe a little bit in SC. ;)


-------------
USF SAE


Posted By: RonGeorge
Date Posted: Oct/06/2010 at 1:41am
Originally posted by dillon_b12 dillon_b12 wrote:

Ron,

You are making an awful lot of assumptions about this particular USF car.  How do you know it was nose heavy?  Data from Alabama shows that our car was around a 45/55 weight distribution, and it didn't fly well.  Furthermore, the same data shows that there wasn't a single car at that competition that was over a 48/52 split w/ driver.  Unless you are defining nose-heavy in a different way, there wasn't one nose-heavy car there and they definitely didn't all fly well.


To see this data would be nice.

I define nose heavy not only by the longitudinal weight bias, but the general phenomenon of tipping front down in the air. When you say "jumping nose heavy", anyone can picture it.

IF what you write is true, then this has piqued my interest more. The next bit of data I will be interested in looking for these misbehaving cars is their rear suspension spring values, orientation of the springs, length of jumps where this happened and the general shapes of the curves. This could be the rear end pogo-stick effect happening due to suspension compression on short, steep jumps. Some drivers may even let off the throttle right after the jump (due to nervousness, traffic ahead and so on), and the sudden change of engine rotational inertia in the rear might also play a role. More weight on the rear shocks means more stored energy, yes? So that coupled with progressive rate springs means --- booom! Perhaps track designers, wary of this unwanted side effect of short steep jumps, could design for a longer downslope on the exit side such that the nose heavy cars land on a downslope? In reality, probably no one is going to do this, and so things still depend a lot on driver skill and understanding of the physics of driving and the machine they're driving.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: dillon_b12
Date Posted: Oct/06/2010 at 2:06am
http://forums.bajasae.net/forum/alabama-vehicle-characteristics_topic178.html?KW= - Alabama Vehicle Data

I've heard of playing with the throttle on RC cars during jumps to get them to level out in flight. If this happens in a Baja car is hard to say. From what I've heard, it's not the engine's rotational inertia that does it. It's the tires rotational inertia. Nitro burning RC cars have ridiculous power to weight ratios allowing them to be able to spin those tires up fast and rotate the car mid-flight.

Some drivers definitely do let off the throttle after the initial jump. Even if it is possible to get the car to rotate by mashing the throttle mid-jump, landing the car at WOT is going to give you a whole new set of problems where the only things that are flying are the bits and pieces of your exploded driveline.


Posted By: Tantum
Date Posted: Oct/06/2010 at 3:15am
" Even if it is possible to get the car to rotate by mashing the throttle mid-jump, landing the car at WOT is going to give you a whole new set of problems where the only things that are flying are the bits and pieces of your exploded driveline. "


LOL


-------------
~ Nick


Posted By: collinskl1
Date Posted: Oct/06/2010 at 8:46am

Because of this, I used to tell people before they drove our cars that if they landed on the throttle they were never driving our cars again...  We always landed nose down, and I attribute it to the lack of speed off the jump, this pogo effect on the rear suspension, and general jump shape not being suited for baja cars...  Not to mention that if you're in the air you're not going faster.

The wing helped USF jump.  Their cars are great.  Their drivers are great.  Bummer about the all fsae deal this year, but I'm sure they're going to bring a lot of knowledge back from the asphalt world and who knows, maybe they'll run full aero Shocked

-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Rob71zilla
Date Posted: Oct/06/2010 at 8:56am
Ron, what's your baja experience?  If you have ever built one of these cars or been to a competition you would know that 90% of these cars nose dive off the jumps.  It's pretty much just something we deal with...

-------------
Robbie
Former Team Captain
SUNY Institute of Technology
Current Engineer for Remington Arms

A Redline a day keeps the carbon away.


Posted By: RonGeorge
Date Posted: Oct/06/2010 at 10:33am
This has to start with the the drawing board so all your dimensions are ideal would be step 1 to cure noseheaviness. A short wheelbase but not drastically short would help. Get the front to rear wt distribution in the ideal range as well.

Step 2 would be to adjust the spring, compression and rebound settings on the reservoir and test on your track until noseheaviness is neutralized. This is what I can tell you generally. Specifically, its hard to tell which way to tune because even I'm somewhere on the steep slope of the learning curve with suspension tuning. In general, short length steep jumps are a contributer. Check this very good example out :






If the track were to be such that the distance along the slope is much greater, the suspension could handle that. I strongly believe it is rapid compression that leads to pogo-sticking.

Check out UB's track outside their machine shop, which has a gradual slope to it. No evidence it is a contributer to front end pitching.



Step 3 - Obviously, no one is going to make a track like you want them to. So like I wrote before, a lot of the in-air dynamics of the car also is in the hands of the driver and his/her skill.

At this moment, I dont choose to believe that the wing by itself is doing anything much. To do a study on whether it did anything significant at these low speeds, we would have to test with the same driver, on the same track, with the same car and suspension settings. Did USF test the car without wings but with smaller wheels, after adjusting the suspension for short steep jumps? For all we care, it could just be the weight in the rear that is balancing the car out. How do I know?


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: dillon_b12
Date Posted: Oct/06/2010 at 12:18pm
Ron, see this thread.

http://forums.bajasae.net/forum/tuning-for-jumps_topic18.html - http://forums.bajasae.net/forum/tuning-for-jumps_topic18.html




Posted By: johnfar109
Date Posted: Oct/06/2010 at 1:35pm
Just an FYI the BU car that jumps well in that video Had an 18 hp Briggs V-twin engine with straight pipes in it (Youtube caption: "Baja SAE car jumping the hill on campus with an 18 hp Briggs V-twin engine with straight pipes.")

Like stated early most cars would jump better with More power


-------------
- John Farnach

RIT BAJA SAE

That Guy 04-09'

RIT 2010 Maneuverability Captain & Track Prep and Construction
RIT 2013, 2016, 2019 Electronic Scoring & Track Prep and Construction


Posted By: asims
Date Posted: Oct/06/2010 at 5:17pm
Originally posted by dillon_b12 dillon_b12 wrote:

I've heard of playing with the throttle on RC cars during jumps to get them to level out in flight. If this happens in a Baja car is hard to say. From what I've heard, it's not the engine's rotational inertia that does it. It's the tires rotational inertia. Nitro burning RC cars have ridiculous power to weight ratios allowing them to be able to spin those tires up fast and rotate the car mid-flight.


I had an electric RC car with enough power to make the car do a complete backflip off a jump if I gunned it.  You could also slam it in reverse and do a front flip with a big enough jump.  Thats the nice thing about electric - instant reverse. LOL  This effect is also something that can be done on dirtbikes.

Like you said, it depends greatly on the power to weight ratio and how quickly the engine will throttle up.  We built a plywood ramp that was ~2 feet tall and ~8 feet long.  At full speed we could do about a 25-30 foot jump across level pavement, getting maybe 3-4 feet in the air.  If you're curious, we measured the length of the jump by where the pavement got gouged by the front end. Shocked

In our attempts to adjust flight attitude, gunning the throttle had minimal effect.  These cars just don't have the power or quick throttle response to do it.  This car also had about a 35/65 F/R weight distribution.  I could see the lightest cars with a well tuned CVT maybe getting a marginal effect this way, but I doubt it would be enough to compensate for the usually significant nose-down attitude we get.


-------------
Andrew Sims
University of Arizona


Posted By: ErikHardy
Date Posted: Oct/06/2010 at 7:06pm

The tiny power to weight ratios on these cars are (I believe) the biggest contributor to the heavy nose while attempting to jump. Ignoring weight transfer, shocks, aero etc, the moment the front wheels leave the ground, the motor has to have enough torque to keep the vehicle from diving.

Air control in a baja car by the driver in the air - There isn't any. With the relatively tiny jumps we hit with these cars, there isn't enough flight time to make a difference, even if we had gobbs of power to work with. I'm willing to bet if we found a big enough jump (lets just say off a cliff for giggles) that the car would nose dive all the way down no matter how fast you got the motor going.


Posted By: adrive7
Date Posted: Oct/06/2010 at 8:17pm
My avatar picture is evidence of an early adventure in jumping baja cars freshman year. Here's a bigger version which I submit as evidence that you can indeed control a baja car in midair; note the completely locked rear wheels:


(Yes, that's the seatbelt hanging out the bottom. No, I wasn't buckled in. Yes, this is stupid. No, I don't know why I didn't feel like buckling up. Luckily, I didn't roll)

Now, we never see jumps this big at competition. You can see what I was hitting better in this picture:



6 foot ramp on cinder blocks, on top of a curb, followed by about a 2-3 foot drop off. The car only survived a few of these. You might notice that the fire extinguisher isn't in the second picture. It flew off when I hit the ground and went spraying across the parking lot. I think we blew up both CVs when this one landed. 

I suppose I can submit this set of pictures as a "Bad Idea"

As for the wing, there's no doubt in my mind that it would be effective. USF even posted before and after pictures of the same jump showing the improvement in flight characteristics. Whether it's worth doing is another question.

Finally, while letting off the gas mid-air is going to change your attitude, failure to let off the gas is going to wreck your drivetrain. As previous posters have mentioned, if you land a jump at WOT you get a chewing out. 


-------------
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com


Posted By: ErikHardy
Date Posted: Oct/06/2010 at 9:36pm
Joe,
I should have been more clear on the air control. I was reffering to possibility of bring the front end up by increasing the rpms of the whee
m…
ls.


Posted By: adrive7
Date Posted: Oct/06/2010 at 9:39pm
Yeah, I know. These cars dont really have much power to do that. Ideally, you would blip the gas on the jump to squat the rear end, too. But we don't have power for that either. 

I'm just saying, you can do the opposite. Slam on the brakes and you'll rotate forward.


-------------
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com


Posted By: Pedro UFPBaja
Date Posted: Oct/07/2010 at 1:23am

stupid stunts with the old car.
Result: pilot with neck ache for 1 week


Posted By: CobraCommander
Date Posted: Oct/07/2010 at 8:25am

If you look at the divot where he hits you can see that there is quite the hole... I think they rolled this car over a dozen times in a row like this... Don't really know why, before my time... Proof that it was an overbuilt monster though...

-------------
COBRA Team Captain


Posted By: RonGeorge
Date Posted: Oct/07/2010 at 5:56pm
Originally posted by ErikHardy ErikHardy wrote:

The tiny power to weight ratios on these cars are (I believe) the biggest contributor to the heavy nose while attempting to jump. Ignoring weight transfer, shocks, aero etc, the moment the front wheels leave the ground, the motor has to have enough torque to keep the vehicle from diving.



This argument is flawed. I don't think you can ignore weight transfer or the shocks in this scenario, or in any scenario. The mechanics of the jump in a mini baja car has it that when you throttle up before the jump in preparation, weight is transferred to the rear of the vehicle - to the axle and the wheels - principally through the suspension. For an isolated bump like a linear ramp or a haversine ramp profile (whose grade is incidentally more steep than a linear ramp of the same height elevation), the suspension compression very quickly and rebounds before the jump leading to pitch. Even Polaris ATV owners complain about this from time to time, but they don't fix wings as a solution. If from your experience, throttle or braking in the air is not doing enough to correct the pitchover, there must be something that could be done to the suspension geometry and settings to overcome the problem.

@Dustin , would you mind sharing any closeup pics of your suspension setup of the winged car?


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: dillon_b12
Date Posted: Oct/07/2010 at 6:50pm
Originally posted by RonGeorge RonGeorge wrote:

  The suspension compression very quickly and rebounds before the jump leading to pitch. Even Polaris ATV owners complain about this from time to time, but they don't fix wings as a solution. If from your experience, throttle or braking in the air is not doing enough to correct the pitchover, there must be something that could be done to the suspension geometry and settings to overcome the problem.

@Dustin , would you mind sharing any closeup pics of your suspension setup of the winged car?



Originally posted by blue2kss blue2kss wrote:

  There are other ways that you can get around the problem of course by slowing down the rebound in the shocks which we used to do, but then its not what we considered optimal around the rest of the track when much of our time was not spent in the air.  Its a trade off that we decided to try out (for a few races then I said no more) and we had mixed results.



Posted By: CLReedy21
Date Posted: Oct/07/2010 at 6:52pm
As far as flips go, I just can't seem to learn my (quite painful) lesson.









-------------
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."


Posted By: ErikHardy
Date Posted: Oct/07/2010 at 7:30pm
Originally posted by RonGeorge RonGeorge wrote:


This argument is flawed. I don't think you can ignore weight transfer or the shocks in this scenario, or in any scenario. The mechanics of the jump in a mini baja car has it that when you throttle up before the jump in preparation, weight is transferred to the rear of the vehicle - to the axle and the wheels - principally through the suspension. For an isolated bump like a linear ramp or a haversine ramp profile (whose grade is incidentally more steep than a linear ramp of the same height elevation), the suspension compression very quickly and rebounds before the jump leading to pitch. Even Polaris ATV owners complain about this from time to time, but they don't fix wings as a solution. If from your experience, throttle or braking in the air is not doing enough to correct the pitchover, there must be something that could be done to the suspension geometry and settings to overcome the problem.
Ok, don't ignore weight transfer.
The weight transfer from flicking the throttle on a governed 10hp briggs woun't do anything on these cars. There must be something to counteract the front wheels from pitching forward and these motors just dont have enough guts to do it. Until these cars have bigger motors they will always nose dive.
 
The weight transfer (constant throttle) from hitting the face of the jump depends on the transition from the ground to the jump. If its some homemade wood ramps that are 3ft tall x 6ft long and have a linear slope, the nose will be reaching for the ground in a hurry. Most motocross tracks have long jump faces with smooth transitions (exponential slope) and for good reason. These types of jumps will allow the car to be in a steady state while keeping the nose high. Most baja cars can get away with jumping these due to the initial state of the car being nose high and slowing rotating downward, and hopefully landing reasonably so the nose doesnt dig into the ground.
 
Some band-aids for this problem - shock settings as mentioned before, wing (insert USF here) Keeping the wheels as far forward of the nose as possible allowing the wheels to hit first, not the frame. In the end, the front end will always be pitching forward. Try finding a single picture or video where the slope between the front and rear wheels is greater than the slope of the jump.


Posted By: blue2kss
Date Posted: Oct/07/2010 at 8:52pm
Originally posted by RonGeorge RonGeorge wrote:



@Dustin , would you mind sharing any closeup pics of your suspension setup of the winged car?


The rear is just the same good ol' USF swing arm design.  We have since been able to take an additional 4-6 lbs out of it.  The front was nothing special that year, stock Polaris uprights, heavy heat treated 1" .065" lowers and 1" .035" uppers (complete overkill) with a sh*t ton of rod end sticking out probably due to a royal F UP, I dont remember why we had so freaking much rod end levered out there like that.  The car is sitting very high in the last picture (wanted to run Elka shocks, but got screwed by them and had to run the Works which were not the right length), but when the motor and driver were in it it had 9" of ground clearance on a good day.  This was a serious low rider that handled like a dream




















-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: RonGeorge
Date Posted: Oct/07/2010 at 9:25pm
Originally posted by ErikHardy ErikHardy wrote:

Ok, don't ignore weight transfer.
The weight transfer from flicking the throttle on a governed 10hp briggs won't do anything on these cars. There must be something to counteract the front wheels from pitching forward and these motors just dont have enough guts to do it. Until these cars have bigger motors they will always nose dive.
 
I know where you're going with this, infact I completely agree that the power to weight on these cars are minimal. Even a featherweight of 350 lbs producing 10 HP theoretical has (10/350) = .028 HP/lb. All I was trying to get at is that if the engine is connected to a pair of 23-25" wheels that are unloaded in the air and at the slow speeds of flight, sudden changes in wheel rotational inertia could play a role in controlling car attitude.

In the end, extra weight on the shocks is extra weight. When you wrote "weight transfer won't do anything" I raised an eyebrow.

In Alabama, USF had :

Wheelbase = 66.6"
42%, 58% front and rear weight distribution respectively
Weight  417 lbs
COG Height = 20" (assumed)

Calculated - Their CG is located 38.5" from the front wheel center.

Say this 417 lb car with a 200 lb driver was moving along at 15 mph, at 7 HP. Longitudinal acceleration is then about 13.5 ft/sec^2. The weight transfer to the rear shocks as a result of this acceleration is almost 36 extra lbs.  And this is due to a flat track.

With an incline of 3' tall by 6' feet long ramp, there's a rise angle of 26 degrees. Due to this grade, there is an additional quick weight transfer that varies as a cosine of the angle, which in USF's case equates to 56 lbs. Thats the weight of an additional 10 HP B&S engine handed back to you by physics.

As for the rest of what you wrote, I agree.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: blue2kss
Date Posted: Oct/07/2010 at 10:05pm
Originally posted by RonGeorge RonGeorge wrote:

@Dustin,

Interesting , thanks for the reply. I can get a scale of the things by seeing it in the pictures provided. That wing is way over the proportions that I imagined it to be. To be clear, these images don't prove to me that in general, wings do effectively what they are theorized to do in a slow moving car. But if it worked for you, good. If you did something drastic to improve the safety of the drive for your driver, all the better.


The wing had to have the angle of attack, width and length in order to be effective at the low speeds.  If that and the pictures dont convince you that it works, well I don't know what to tell you then. 



Originally posted by RonGeorge RonGeorge wrote:


Keep in mind that if you had avoided making a nose heavy vehicle in the first place, you wouldn't need a wing.  If you still couldn't avoid that situation, skillful drivers might have been able to correct that lingering problem by chopping the throttle in the air through precise timing. Few drivers are really talented to take a machine they're given to the extremes.


I don't know what you mean by nose heavy, you have tried to explain what you meant in other posts but due to the low speeds that we travel, the short wheelbase that we have, and the courses that we typically run on meant for speeds twice of what we hit them at the nose pitch is going to happen.  Kevin (our driver for three years) was one of the best drivers I have ever had the experience of working with and trust me, if there was something else to be had outta that car he would have found it before race time.  You can ask any team who has been around for a bit about Kevin and they all know he is the off-road version of the Stig.  Dont ever bother trying to race him on a mountain bike either, he is even more of a machine there.  And Kevin was our transmission and drive train guru, so he did work on the cars quite a bit.  He wasn't just a designated driver.




Originally posted by RonGeorge RonGeorge wrote:


It just reinforces the idea in my mind that in general, wings are a bad idea. If everyday you'd be out in an open desert where you'd have no obstructions to worry about, maybe. But this is purported to be an off-road recreational car and as a designer, your goal is to make a sensible vehicle that has balanced performance on all terrain conditions at slow speeds of 30-35 mph. The added weight, possibility of increased drag at slow speeds on level ground (aerodynamics is not a a very intuitive branch of study)  , lack of maneuverability in a track with overgrowth and the ability to collect things and add further weight, such as a huge pile of snow in winter, tell me that tradeoffs are more than one or two advantages.

If this nose heavy phenomena happens to us in testing, we'll just have to try the wings.


As far as a bad idea, that's why I put it in this thread.  You can make it work great at certain tracks.  If I ever raced Baja again and we were going to RIT I would even give it a second thought because of how well it works at the moto-cross tracks.  The wing weighed 2 lbs, and the frame probably at most 6.  It would collect mud like a SOB though, so your argument about the added weight is valid.  But snow I wasn't worried about, this is a summer race season.  As far as the increased drag, it tamed the oversteer to almost a perfect balance as it turned out, wasn't planned that way.  Just trying to ride a bicycle and holding the wing or just running with it you can easily feel how it can generate the 33 lbs of down force.


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: RonGeorge
Date Posted: Oct/07/2010 at 11:02pm
Hmm. So if this is to be expected on all baja cars as you guys write, then I guess we'll all have to deal with it by moving the front wheels forward, tuning out the suspension and taking those jumps sensibly. The following video of a car nose diving is not too good for safety. That rear suspension compresses on that incline in less than 7 hundredths of a second too.



Incidentally, I searched on youtube for nose diving phenomenon and many powerful buggies and cars are doing it as well. The idea that more horsepower will help cure this problem is a solid myth. As for the wing cure, I won't believe it until I see more data and see tests done myself. 






-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: blue2kss
Date Posted: Oct/07/2010 at 11:06pm
Originally posted by RonGeorge RonGeorge wrote:

Hmm.







Ha ha, that is USF flipping in 2005 or 2006 with our driver Tim.  Haven't seen that video in years.  He won that suspension and traction event on the next run





-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: RonGeorge
Date Posted: Oct/08/2010 at 12:01am
Boy what a coincidence. 

-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: RonGeorge
Date Posted: Oct/10/2010 at 12:06am
I looked at OSU's jumps and comparatively, their nose pitch rate isn't as high as the ones to many other videos I saw. The video is here : http://groups.engr.oregonstate.edu/SAE/Baja/ - http://groups.engr.oregonstate.edu/SAE/Baja/


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: njgedr
Date Posted: Oct/10/2010 at 12:38pm
The way to tell if a freshman has any idea what he is talking about is to ask him to fetch a left handed screwdriver. Nothing is more amusing than watching him stumble around the shop asking people for a left handed screwdriver. That usually puts an end to the stupid suggestions, like turbos, and nitrous. For some reason every kid who has ever changed the oil on his civic thinks he knows everything about baja.

-------------
Rowan Baja 2009-2012
Auburn 09
Peoria 11
Epreuve Du Norde 12
Auburn 12
Wisconsin 12

Mubea Development Engineer


Posted By: Tony Rivera
Date Posted: Oct/12/2010 at 12:33am
This is a video from our 09 car that went to Wisconsin

http://www.youtube.com/watch?v=10XI_LHXxx4

The car had a 30/70 front/rear weight distribution, and flew great. It also under-steered so bad that we couldn't turn the car with our foot on the gas.
As you watch the video, from 1:30 - 3:30, you can notice the flight characteristics, handling characteristics, and the cars general tendency to roll over backwards



-------------
Tony Rivera

Arizona State University
Team Captain 2009-2010

Local Motors Vehicle Systems Engineer


Posted By: ErikHardy
Date Posted: Oct/12/2010 at 9:22pm
Originally posted by RonGeorge RonGeorge wrote:

Incidentally, I searched on youtube for nose diving phenomenon and many powerful buggies and cars are doing it as well. The idea that more horsepower will help cure this problem is a solid myth. As for the wing cure, I won't believe it until I see more data and see tests done myself. 

Ron, it is by no means a myth. I will give you a little background of myself so you understand where I am coming from. I have spent the last 11 years racing motocross, jumping things that I should not have been, which includes landing on my lid from way too high up due to improper control in the air and on the face of the jump. The major component of what happens in the air is largely determined by the throttle control and weight transfer of the combined system (vehicle & driver) on the jump face.
 
For example: I have plenty of power at my finger tips to have the front end due whatever I want to on the face. If thats not enough, I can manuever my body to kick up the front as well if needed. Together, they allow for complete control of the bike in the air.
 
Trophy truck - These incredibly awesome machines have upwards of 800hp with damn near instant throttle response. Its typical for these trucks to jump 100ft on the average short circuit track. The drivers have no problem controlling the vehicles in air.  Now replace their awesome V8 power with a civic motor and what would you expect to happen when they hit a jump? See any baja SAE vehicle for a result.
 
If you still dont believe in any of this, nothing is stopping you from slapping in a well tuned snowmobile motor into an old car, well besides a hospital bill but thats not my point.
 


Posted By: RonGeorge
Date Posted: Oct/12/2010 at 10:15pm
Erik,

Alright, when lacking horsepower like in our case, I think we can only rely on the suspension so if I'm thinking about this right, adjusting the rebound so its more on the front than the rear should ensure some amount of compensation for nose diving. Other than that, the incline of the track is something you cannot control. Nevertheless, I saw some videos of Baja trucks and sand dune buggies doing the same thing. In the following videos, there's plenty of horsepower, as opposed to our baja cars.

Here's one. If I'll take a shot in the dark, I think he had too much rebound on his rear shocks :




And this :







-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: CobraCommander
Date Posted: Oct/12/2010 at 10:40pm
Showing examples of bad driving doesn't make this any more clear... I would consider both those to be the fault of the driver and not necessarily the suspension system or vehicle as a whole.

If the course was pre-run as most desert races are... The the first driver should have been prepaired for the crest and slowed due to the following incline... That is a horrible place to become airborne because the prospect of landing smoothly past the downslope is nil.

The second driver should have burred his foot into the floorboards once clearing the first crest at the start of the video, gaining enough speed to clear the depression past the second. For all you know that car could have been limited in its ability to do that because of the engines horsepower.

So to bring this back on topic of BAD IDEAS: Not enough seat time to know how your vehicle behaves out on the track... I know my school is guilty of this and we are working to correct it this year and get driving as soon as this years vehicle gets built.


-------------
COBRA Team Captain


Posted By: RonGeorge
Date Posted: Oct/12/2010 at 11:25pm
Hilarious. So I'm not the only one making wild speculations about drivers. :) Oh, do me a favor. Check out Luke Whelan's standings in the 2009 Tasmania Off-road races. http://www.cams.com.au/en/Common/%7E/media/Files/Sport/Regulations/2009%20Tas%20Off%20Road%20State%20Sporting%20Regs.ashx - http://www.cams.com.au/en/Common/~/media/Files/Sport/Regulations/2009%20Tas%20Off%20Road%20State%20Sporting%20Regs.ashx


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: RonGeorge
Date Posted: Oct/12/2010 at 11:46pm
Originally posted by CobraCommander CobraCommander wrote:

Showing examples of bad driving doesn't make this any more clear... I would consider both those to be the fault of the driver and not necessarily the suspension system or vehicle as a whole.

If the course was pre-run as most desert races are... The the first driver should have been prepaired for the crest and slowed due to the following incline... That is a horrible place to become airborne because the prospect of landing smoothly past the downslope is nil.

The second driver should have burred his foot into the floorboards once clearing the first crest at the start of the video, gaining enough speed to clear the depression past the second. For all you know that car could have been limited in its ability to do that because of the engines horsepower.

So to bring this back on topic of BAD IDEAS: Not enough seat time to know how your vehicle behaves out on the track... I know my school is guilty of this and we are working to correct it this year and get driving as soon as this years vehicle gets built.


I don't know about accusing Luke Whelan of poor preparation. What I know is that his buggy that you saw in the video has a 5.9 L V8 engine on it.


-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: collinskl1
Date Posted: Oct/13/2010 at 9:34am
Originally posted by CobraCommander CobraCommander wrote:


So to bring this back on topic of BAD IDEAS: Not enough seat time to know how your vehicle behaves out on the track... I know my school is guilty of this and we are working to correct it this year and get driving as soon as this years vehicle gets built.
 
Thank you!  We need a thread to argue jump characteristics... oh wait, there already is one. 
 
Along the lines of not enough seat/testing time, we used a friction slip clutch in our chain box a couple years ago, but since we didn't have time to get it set up all the way, we tightened it down all the way so it couldn't slip at all.  This effectively gave us a 15 pound flywheelish sprocket in our drivetrain that did nothing.


-------------
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.


Posted By: Tantum
Date Posted: Oct/13/2010 at 10:13am
Originally posted by RonGeorge RonGeorge wrote:

Erik,

Alright, when lacking horsepower like in our case, I think we can only rely on the suspension so if I'm thinking about this right, adjusting the rebound so its more on the front than the rear should ensure some amount of compensation for nose diving. Other than that, the incline of the track is something you cannot control. Nevertheless, I saw some videos of Baja trucks and sand dune buggies doing the same thing. In the following videos, there's plenty of horsepower, as opposed to our baja cars.

Here's one. If I'll take a shot in the dark, I think he had too much rebound on his rear shocks :

*Video*

And this :

*Video*





If Luke Whelan wants to stop being so TIPPY, maybe he should buy a wing from USF.


-------------
~ Nick


Posted By: blue2kss
Date Posted: Oct/13/2010 at 10:53pm
Originally posted by Tantum Tantum wrote:



If Luke Whelan wants to stop being so TIPPY, maybe he should buy a wing from USF.


I'm sure my guys will sell him one cheap!  We still had a few laying around after I left lol


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: Akron 1998 to 2004
Date Posted: Jan/21/2011 at 12:21pm

I don't know how any one could look at the pictures of the winged USF car jumping and think it's still a bad idea to use aerodynamics to stabilize a Baja car’s trajectory in flight.  Clearly it worked great.  There should be a dozen copy cats or at least a few teams that give it a try over the summer.

I can think of 2 major draw backs:

1.      1. All the stupid comments from people you have to deal with constantly would be more than enough for most people to rip the dang thing off.

2.      2. You can’t have 50 lbs of down force at 20 mph without making a considerable amount of drag.  The advantage in a jump lasts 1 second.  The constant drag on the car in continuous.

Assume the wing made 10 lbs of drag force on the car constantly.  At 20 mph it takes 0.5 HP just to drag the wing around the track for no reason.  That is a massive amount of HP for one of these cars.  But when you take into account how much energy is obliterated each and every time you slam on the brakes for a jump, it could be worth it.

It’s a brilliant idea for the problem.  Of course my opinion is affected by the fact that I thought of doing this in 2004 and I'm about 95% confident I discussed the idea in detail with a few USF guys at competition (2005 West as a spectator).  I just about pissed myself laughing when I started getting e-mails from people about the winged USF Baja car.  It worked exactly the way I had envisioned it.  It’s freaking pornographic for me to watch this car in flight.



Posted By: RonGeorge
Date Posted: Jan/21/2011 at 2:30pm
Yes, how you make the wings matters a lot. For example, you can make a wing with a dish shape without putting a deep air foiling it and it will create much higher drag. In essence, give a wing design to someone who doesn't know much and he will 'spoil" the spoiler for you guaranteed. In the hands of someone experienced, it may help the car but you still can't discount the extra engineering time for a wing. 

-------------
-Ron George
Systems Engineer (Cummins Turbo)


Posted By: blue2kss
Date Posted: Jan/21/2011 at 10:58pm
Originally posted by RonGeorge RonGeorge wrote:

Yes, how you make the wings matters a lot. For example, you can make a wing with a dish shape without putting a deep air foiling it and it will create much higher drag. In essence, give a wing design to someone who doesn't know much and he will 'spoil" the spoiler for you guaranteed. In the hands of someone experienced, it may help the car but you still can't discount the extra engineering time for a wing. 


I agree here.  The time and effort spent trying to get a decent design in and building the systems IMO wasn't worth it.  The drag can be a big issue as we are limited to a low speed underpowered drive train but it was worth a shot and it certainly has its advantages too.  Whether or not the team decides its worth it is up to their design goals for the year.


-------------
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development


Posted By: frinesi2
Date Posted: Jan/26/2011 at 11:28pm
So I guess the next step is an air brake?



Print Page | Close Window