Bad Ideas |
Post Reply | Page 12> |
Author | ||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
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) |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
Post Options
Thanks(0)
|
|
Dustin, the theory on the wing was to balance the car on jumps correct?
|
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
johnfar109
Organizer Joined: Jul/08/2009 Location: Rochester, NY Status: Offline Points: 143 |
Post Options
Thanks(0)
|
|
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 |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
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) |
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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. |
||
Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
Post Options
Thanks(0)
|
|
I've always been a proponent of filling the tires with helium or something like that |
||
SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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. |
||
Rob71zilla
Welding Master Joined: Feb/09/2009 Location: Utica, NY Status: Offline Points: 324 |
Post Options
Thanks(0)
|
|
We wanted to fill the frame with hydrogen last year
|
||
Robbie
Former Team Captain SUNY Institute of Technology Current Engineer for Remington Arms A Redline a day keeps the carbon away. |
||
Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
Post Options
Thanks(0)
|
|
We thought about that too |
||
SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
||
YonkersBaja
Bolt Sorter Joined: Oct/07/2009 Status: Offline Points: 27 |
Post Options
Thanks(0)
|
|
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?
|
||
Tantum
Bolt Sorter Joined: Jun/26/2010 Location: Rochester Status: Offline Points: 31 |
Post Options
Thanks(0)
|
|
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
|
||
Moreau
Bolt Sorter Joined: Feb/28/2010 Location: Baltimore Status: Offline Points: 7 |
Post Options
Thanks(0)
|
|
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 |
||
wishin4snow
Milling Master Joined: Aug/05/2009 Location: Williamsport PA Status: Offline Points: 52 |
Post Options
Thanks(0)
|
|
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" |
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
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) |
||
CLReedy21
Baja Godfather Joined: Nov/30/2008 Location: Marysville, OH Status: Offline Points: 736 |
Post Options
Thanks(0)
|
|
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." |
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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. |
||
Rob71zilla
Welding Master Joined: Feb/09/2009 Location: Utica, NY Status: Offline Points: 324 |
Post Options
Thanks(0)
|
|
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
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. |
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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. |
||
CobraCommander
Milling Master Joined: Feb/03/2010 Location: Ontario, Canada Status: Offline Points: 95 |
Post Options
Thanks(0)
|
|
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
|
||
dillon_b12
Baja Godfather Joined: Nov/15/2008 Status: Offline Points: 781 |
Post Options
Thanks(0)
|
|
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!".
|
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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. |
||
Pancho.
Bolt Sorter Joined: Sep/29/2010 Location: Altoona Pa Status: Offline Points: 5 |
Post Options
Thanks(0)
|
|
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. |
||
ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
Post Options
Thanks(0)
|
|
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.
|
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
@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) |
||
ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
Post Options
Thanks(0)
|
|
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.
|
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
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) |
||
JHrdy724
Bolt Sorter Joined: Oct/24/2008 Location: AUburn Status: Offline Points: 37 |
Post Options
Thanks(0)
|
|
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 |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
Sure is, and our spread sheet calculations were extensive with this...
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 |
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
AndyRIT
Organizer Joined: Nov/11/2008 Location: Sheboygan, WI Status: Offline Points: 193 |
Post Options
Thanks(0)
|
|
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 |
||
ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
Post Options
Thanks(0)
|
|
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.
|
||
blue2kss
Welding Master Joined: Dec/23/2008 Location: USF Status: Offline Points: 169 |
Post Options
Thanks(0)
|
|
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 |
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
@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) |
||
dillon_b12
Baja Godfather Joined: Nov/15/2008 Status: Offline Points: 781 |
Post Options
Thanks(0)
|
|
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.
|
||
Old Greg
Bolt Sorter Joined: Jun/24/2009 Location: Tampa, FL Status: Offline Points: 34 |
Post Options
Thanks(0)
|
|
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
|
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
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) |
||
dillon_b12
Baja Godfather Joined: Nov/15/2008 Status: Offline Points: 781 |
Post Options
Thanks(0)
|
|
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 |
||
Tantum
Bolt Sorter Joined: Jun/26/2010 Location: Rochester Status: Offline Points: 31 |
Post Options
Thanks(0)
|
|
" 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. "
|
||
~ Nick
|
||
collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
Post Options
Thanks(0)
|
|
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 |
||
Kyle Collins
Lipscomb University Alumni 2x Project Manager Nexteer Automotive Product Engineer, Electronic Power Steering ... and the 8th simple machine: a bigger hammer. |
||
Rob71zilla
Welding Master Joined: Feb/09/2009 Location: Utica, NY Status: Offline Points: 324 |
Post Options
Thanks(0)
|
|
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. |
||
RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
Post Options
Thanks(0)
|
|
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) |
||
dillon_b12
Baja Godfather Joined: Nov/15/2008 Status: Offline Points: 781 |
Post Options
Thanks(0)
|
|
johnfar109
Organizer Joined: Jul/08/2009 Location: Rochester, NY Status: Offline Points: 143 |
Post Options
Thanks(0)
|
|
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, 2019 Electronic Scoring & Track Prep and Construction |
||
asims
Welding Master Joined: Apr/07/2009 Location: Tucson Status: Offline Points: 184 |
Post Options
Thanks(0)
|
|
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. 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. 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 |
||
ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
Post Options
Thanks(0)
|
|
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.
|
||
Post Reply | Page 12> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |