Official Baja SAE Forums Homepage
Forum Home Forum Home > General > Design Discussion
  New Posts New Posts RSS Feed - Bad Ideas
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Bad Ideas

 Post Reply Post Reply Page  12>
Author
Message
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post Topic: Bad Ideas
    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)
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
ErikHardy View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Apr/12/2010
Location: Hood, Flint, MI
Status: Offline
Points: 939
Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2010 at 12:49am
Dustin, the theory on the wing was to balance the car on jumps correct?
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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.


Edited by blue2kss - Sep/28/2010 at 9:59pm
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development
Back to Top
johnfar109 View Drop Down
Organizer
Organizer
Avatar

Joined: Jul/08/2009
Location: Rochester, NY
Status: Offline
Points: 141
Post Options Post Options   Thanks (0) Thanks(0)   Quote johnfar109 Quote  Post ReplyReply Direct Link To This Post 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 Electronic Scoring & Track Prep and Construction
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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



Edited by RonGeorge - Sep/29/2010 at 8:12am
-Ron George
Systems Engineer (Cummins Turbo)
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Red_Beard View Drop Down
Organizer
Organizer


Joined: May/14/2009
Location: Bellingham, WA
Status: Offline
Points: 269
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Rob71zilla View Drop Down
Welding Master
Welding Master
Avatar

Joined: Feb/09/2009
Location: Utica, NY
Status: Offline
Points: 324
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rob71zilla Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Red_Beard View Drop Down
Organizer
Organizer


Joined: May/14/2009
Location: Bellingham, WA
Status: Offline
Points: 269
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
YonkersBaja View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Oct/07/2009
Status: Offline
Points: 27
Post Options Post Options   Thanks (0) Thanks(0)   Quote YonkersBaja Quote  Post ReplyReply Direct Link To This Post 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?
Back to Top
Tantum View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jun/26/2010
Location: Rochester
Status: Offline
Points: 31
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tantum Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
Moreau View Drop Down
Bolt Sorter
Bolt Sorter


Joined: Feb/28/2010
Location: Baltimore
Status: Offline
Points: 7
Post Options Post Options   Thanks (0) Thanks(0)   Quote Moreau Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
wishin4snow View Drop Down
Milling Master
Milling Master
Avatar

Joined: Aug/05/2009
Location: Williamsport PA
Status: Offline
Points: 52
Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post 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"
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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. 

Edited by RonGeorge - Sep/29/2010 at 9:49pm
-Ron George
Systems Engineer (Cummins Turbo)
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post 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."
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Rob71zilla View Drop Down
Welding Master
Welding Master
Avatar

Joined: Feb/09/2009
Location: Utica, NY
Status: Offline
Points: 324
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rob71zilla Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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:
 
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.
Back to Top
CobraCommander View Drop Down
Milling Master
Milling Master


Joined: Feb/03/2010
Location: Ontario, Canada
Status: Offline
Points: 95
Post Options Post Options   Thanks (0) Thanks(0)   Quote CobraCommander Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post 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!".
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Pancho. View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/29/2010
Location: Altoona Pa
Status: Offline
Points: 5
Post Options Post Options   Thanks (0) Thanks(0)   Quote Pancho. Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
ErikHardy View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Apr/12/2010
Location: Hood, Flint, MI
Status: Offline
Points: 939
Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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)
Back to Top
ErikHardy View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Apr/12/2010
Location: Hood, Flint, MI
Status: Offline
Points: 939
Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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)
Back to Top
JHrdy724 View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Oct/24/2008
Location: AUburn
Status: Offline
Points: 37
Post Options Post Options   Thanks (0) Thanks(0)   Quote JHrdy724 Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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.)




































Edited by blue2kss - Oct/05/2010 at 10:29pm
Dustin Bride
University of South Florida SAE Alumni/Consultant
Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
AndyRIT View Drop Down
Organizer
Organizer


Joined: Nov/11/2008
Location: Sheboygan, WI
Status: Offline
Points: 193
Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post 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)

 


Edited by AndyRIT - Oct/05/2010 at 11:02pm
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
Back to Top
ErikHardy View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Apr/12/2010
Location: Hood, Flint, MI
Status: Offline
Points: 939
Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
blue2kss View Drop Down
Welding Master
Welding Master
Avatar

Joined: Dec/23/2008
Location: USF
Status: Offline
Points: 169
Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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)
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Old Greg View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jun/24/2009
Location: Tampa, FL
Status: Offline
Points: 34
Post Options Post Options   Thanks (0) Thanks(0)   Quote Old Greg Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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.


Edited by RonGeorge - Oct/06/2010 at 1:54am
-Ron George
Systems Engineer (Cummins Turbo)
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/06/2010 at 2:06am
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.

Edited by dillon_b12 - Oct/06/2010 at 2:08am
Back to Top
Tantum View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Jun/26/2010
Location: Rochester
Status: Offline
Points: 31
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tantum Quote  Post ReplyReply Direct Link To This Post 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
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
Rob71zilla View Drop Down
Welding Master
Welding Master
Avatar

Joined: Feb/09/2009
Location: Utica, NY
Status: Offline
Points: 324
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rob71zilla Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
RonGeorge View Drop Down
Welding Master
Welding Master


Joined: Apr/17/2010
Location: Indiana
Status: Offline
Points: 286
Post Options Post Options   Thanks (0) Thanks(0)   Quote RonGeorge Quote  Post ReplyReply Direct Link To This Post 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)
Back to Top
dillon_b12 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/15/2008
Status: Offline
Points: 781
Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/06/2010 at 12:18pm
Back to Top
johnfar109 View Drop Down
Organizer
Organizer
Avatar

Joined: Jul/08/2009
Location: Rochester, NY
Status: Offline
Points: 141
Post Options Post Options   Thanks (0) Thanks(0)   Quote johnfar109 Quote  Post ReplyReply Direct Link To This Post 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


Edited by johnfar109 - Oct/07/2010 at 10:33am
- John Farnach

RIT BAJA SAE

That Guy 04-09'

RIT 2010 Maneuverability Captain & Track Prep and Construction
RIT 2013, 2016 Electronic Scoring & Track Prep and Construction
Back to Top
asims View Drop Down
Welding Master
Welding Master
Avatar

Joined: Apr/07/2009
Location: Tucson
Status: Offline
Points: 184
Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post 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.


Edited by asims - Oct/06/2010 at 5:21pm
Andrew Sims
University of Arizona
Back to Top
ErikHardy View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Apr/12/2010
Location: Hood, Flint, MI
Status: Offline
Points: 939
Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post 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.
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.047 seconds.