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OctoberSky View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OctoberSky Quote  Post ReplyReply Direct Link To This Post Topic: Suspension Design
    Posted: May/20/2009 at 9:42pm
I've read a lot on the forum about general wb, tracks, and cg, but I would like to start a thread on general design.  First question; I am considering running kickup (caster built into the arms/mounts) on next year's car.  Does anyone else have general parameters/ advice for doing this (angles, lengths, etc.)?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rob71zilla Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2009 at 9:48pm
We run 5 degrees of caster built into the frame.  the lower member where the bottom control arm mounts is angled up 5 degrees
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OctoberSky Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2009 at 9:59pm
thanks, we're think about the same for the front, do you guys just manual bend and eyeball it, or do you recommend a better method?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 12:15am
Our frame has about 7 degrees of built in caster in front, if i remember correctly. It was supposed to have 6 in the rear, but the bent tubes came out weird and it only ended up around 3.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FWBcut Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 4:32am
Are you talking about running caster or rake (I think thats the technical term, or atleast what we call it) where the a arms are not parrallel to the ground but angled? In 08 I ran i believe 6 degrees of caster and 14 degrees of rake. You have to look at what camber you want and decide on how much caster you need, and take steering effort into account. More caster= more effort.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 4:37am
I've never heard rake used for a car. On a bicycle/motorcycle its the fork angle. What are you referring to? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OctoberSky Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 12:01pm
Yeah, I had just assumed to have the rake be the same degree as our caster (we are comfortable with the current angle), but I can redesign front knuckles to acommodate a greater rake angle and still maintain about 6 degrees of caster.  From what it looks like choosing a rake angle is arbitrary, or am I not reading my literature closely enough...in the end I don't want to change our geometry or suspension too much, I just want to stop bending rod ends in the front suspension when we hit rocks and curbs at full speed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 12:09pm
Inclined front suspension is kind of like Ackermann as far as dirt suspension goes IMO.  Some people like it, some people hate it.  Some people have had good success with it and others have had good success with arms parallel to the ground.

Our current car has runs some front incline(rake, layback, etc...) and has had good success with it.  Some on the team hate it because it complicates designing of your geometry, fabbing of mounting points, etc...

I personally like it because it takes a little bit of the shock of bumps and jumps off of the mounting points and puts them in to the shock.  It is kind of a pain to fab though.

Like anything else, it has benefits and limitations.  If the goals you are trying to meet require that you do it, then do it.  Everything is a trade-off.  There is no one best system.


Edited by dillon_b12 - May/21/2009 at 1:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paasch Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 12:52pm
Originally posted by FWBcut FWBcut wrote:

Are you talking about running caster or rake (I think thats the technical term, or atleast what we call it) where the a arms are not parrallel to the ground but angled? In 08 I ran i believe 6 degrees of caster and 14 degrees of rake. You have to look at what camber you want and decide on how much caster you need, and take steering effort into account. More caster= more effort.

I'm with Joe on this one.  Caster is out at the wheel, rake (we call it layback) is the angle between the a-arm pickup points and the horizontal.  Layback helps the car over bumps at speed, because the wheel is moving back as it moves up over the bump.  Caster determines steering effort and camber gain due to steer.

We run a lot of layback in the OSU cars, around 18 degrees up front, and 11 degrees in the rear (back when we ran rear a-arms).  Our current drag link rear suspension gives the same effect, though the angle varies with wheel travel.   In the front, layback increases front end dive under braking, which is generally bad.  This can be compensated for by making the top a-arm layback a degree or two larger than the bottom, but this has other drawbacks.  In the rear, layback can be less than the front an achieve the same effect because of the tractive effort of the rear wheels.  Layback in the rear gives anti-squat under acceleration, but this is hardly an issue with 10 HP.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 2:14pm
we ran 15 degrees of rake/layback up front with nearly the same amount of caster... Horrible idea.  It was very hard to turn, but took the rough stuff quite well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mu Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 2:31pm
Originally posted by paasch paasch wrote:


In the front, layback increases front end dive under braking, which is generally bad.  This can be compensated for by making the top a-arm layback a degree or two larger than the bottom, but this has other drawbacks.  In the rear, layback can be less than the front an achieve the same effect because of the tractive effort of the rear wheels.  Layback in the rear gives anti-squat under acceleration, but this is hardly an issue with 10 HP.


 
On the front suspension for our vehicles we do just as you described.  The rake for our top A-arm is a few degrees greater than the rake of the lower A-arm.  We have been doing this for three years and have yet to encounter a problem with it.
 
On another note we need a way to distinguish between the two OSUs on the forum.  Threads get a little confusing when we're both commenting.
 
I think I might start refering to us as The OSU... Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maverick Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 8:23pm
Hi im searching for mini baja adams/car template for ADAMS 12.0..if anyone know how to download please specify or if u ve the template send it to this address karthickbruce@gmail.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kenneth.mandeville Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 8:29pm
Originally posted by mu mu wrote:

 
On the front suspension for our vehicles we do just as you described.  The rake for our top A-arm is a few degrees greater than the rake of the lower A-arm.  We have been doing this for three years and have yet to encounter a problem with it.
 
On another note we need a way to distinguish between the two OSUs on the forum.  Threads get a little confusing when we're both commenting.
 
I think I might start refering to us as The OSU... Wink

Does that just give you a caster gain through travel?  How does that benefit performance?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mu Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2009 at 11:05pm
Originally posted by kenneth.mandeville kenneth.mandeville wrote:


Does that just give you a caster gain through travel?  How does that benefit performance?


Just as Bob described above having two different rakes helps keep the front from diving under braking.  Yes, the caster angle would change but that hasn't been a problem for us so far.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2009 at 12:55am

In front we're running 15 degrees of caster and rake with zero antidive, but it works for our setup with the spool in the rear.  Steering effort is a little high, but completely manageable.  We're working on some new uprights that reduces trail some to help with the steering effort, but this year's setup is working pretty well.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2009 at 3:08pm
We run 15 degrees of "approach angle" (kick-up, lay-back, whatever) which corresponds to 15 degrees of caster at the upright. We do it mainly for ride comfort, secondly to combat camber change due to body roll in corners. I can't say whether or not it actually works, but that's the theory anyway. We also try to get as close as possible to 0" scrub radius to reduce steering wheel kick-back over rough stuff.

Our semi-trailing arms in the back also have an approach angle built in (though it naturally changes with ride height).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2009 at 4:07pm
I have no idea what to call inclined suspension, but usually "approach angle" refers to the angle between the front of the vehicle and the front of the tires. "Departure angle" is the same but for the rear of the car.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2009 at 4:39pm
It's just the internal reference we came up with when we started the team. We don't ever really discuss true approach or departure angles, so there's never much confusion. Plus, it rolls off the tongue easier than "angle referencing inner control arm pivot axis inclination relative to horizontal plane as seen in a side-view," dontcha think?

But rake is probably the most correct term, since increasing the rake angle of a Baja car and a motorcycle has the same effect.

Edited by karman1970 - May/22/2009 at 4:41pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OctoberSky Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2009 at 4:09pm
For those of you who are running more rake than your caster, do you "build back" the angle to your desired caster by messing with the suspension arm mounts or the knuckles.  From experience, it seems easier to do it with the suspension mounts but we've had a lot of trouble getting everything lined up just right
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Post Options Post Options   Thanks (0) Thanks(0)   Quote svijay27 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/18/2009 at 3:15pm
how well do u think trailing arms can perform??? i thought they may result in bump steer. .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/18/2009 at 4:22pm
For which application? Front or rear?

Several teams have made TTA (twin trailing arm) front suspensions over the years. Arizona State for 2008 is the most recent I know of. They work fine for dune buggies and lower class SCORE cars. I personally wanted to try one, but we never got around to it (built a prototype, but it never got to competition). It takes a while, but you can set 'em up for zero bump. You do reach a travel and approach angle limit, but ride quality is unsurpassed.

As for rear suspension, LOTS of teams run trailing arms. We prefer the semi-trailing arm, as it offers slightly better suspension geometry. But a simple 100% trailing arm works fine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jun/18/2009 at 8:48pm
Originally posted by karman1970 karman1970 wrote:

Several teams have made TTA (twin trailing arm) front suspensions over the years. Arizona State for 2008 is the most recent I know of.


*ahem*  University of Arizona.  ASU is a dirty word around here.



This car was our first (and so far only) attempt at using front trailing arms.  They have their benefits, but its very easy to overlook details that will make for poor performance.  This car had its own issues just in the fact that its freaking huge, which made it difficult to make a strong enough trailing arm.  In a lighter weight car, it might work okay, but we weren't impressed enough to do it again.



To be fair, I have to hand it to ASU, they were very pleasant at Wisconsin and we both helped each other out.


Edited by asims - Jun/18/2009 at 8:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LSantora Quote  Post ReplyReply Direct Link To This Post Posted: Jun/18/2009 at 10:47pm
SBM car runs 12 deg. of rake in the front which also sets the front caster (effectively 12 deg).  Steering effort has not been a problem;  I used more caster to get more camber change when steering the wheels.  This allowed for a more parallel SLA configuration.  A lot of camber gain designed into the FVSA geometry usually just results in excess negative camber when the car heaves or lands off a jump.

Also, for a given tire size, the car with some front end rake will be able to take on a larger bump, rock, etc. than the car with no rake.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote svijay27 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 7:01am
thanx guys,
but i made a small mistake. .
we are so used to our semi-trailing arm on last year's vehicle that we call them trailing arms. .  
the front trailing arms look pretty cool though.. .

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Post Options Post Options   Thanks (0) Thanks(0)   Quote svijay27 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 7:06am
and the Arizona vehicle has got pretty long trailing arms which really mean you can get really good travel but what about the strength of the tubes used?? they'd ve to be pretty strong too. . larger moment right?? 

or am i being too pessimistic??

did u go in for thicker tubes or something or did the FEA come along just as well .??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote svijay27 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 7:17am
n i also saw this rocker arm suspension used by WWU sometime back. . they even won the Polaris design award for that. . but any idea how it fared on the track??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 10:32am
Sorry, Andrew. I had a 50/50 shot at getting it right.

Our prototype used aluminum box tube (we also used aluminum box tube for our A-arm car that year). Seemed to us that box tube is inherently better than round tube for the trailing arm application since the directions of the bending forces (primarily side loading) are well known and the box cross-section is stiffer than a round cross-section in those directions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 12:41pm
I was told this story from my mechanics of materials teacher:
Some time ago, engineers were designing a tube like structure to keep a lake out of a bridge pylon site (so they were working on the lake bottom).  They found that they could use I beams to make up the structure, which would be cheaper than what they had used before.  Then there was an accident in which the structure failed and let the lake fill up the dry site.  Apperantly the engineers had failed to consider the failure modes of the I beam which while stronger in one direction was not in another, and the water pressure found the weakest side.

So really make sure that you can say that the forces are "well known".  The nice thing about tubes is that they have a consistent failure mode, with boxes, you have a chance of twisting modes and others which may be associated with collapse of the side of the box.  Assumptions kill baja cars.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2009 at 2:47pm
Don't I know it! As the old saying goes, "Assumption is the mother of all f***-ups."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DrewT Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2009 at 10:12pm
Originally posted by svijay27 svijay27 wrote:

n i also saw this rocker arm suspension used by WWU sometime back. . they even won the Polaris design award for that. . but any idea how it fared on the track??
 
The FSAE-inspired rear suspension you're talking about got used on Viking 39 and Viking 41 from WWU.  It performed very well, but had some durability issues, mostly because it had no bump-compliance angle/rake angle to it and used rod ends everywhere for pivots.  That year's team got very good at replacing broken rod ends.  Also on V41, the rear cross-member the shocks mount to has been replaced a couple times, and is still bending even though its made of 4130 .120 wall square tubing with reinforcing gussets.  Everytime the car gets run, we take bets on which will let go first, a rod end on the rear suspension, or a polaris hub/wheel bearing on the front end.  Still, its a fast car when its running, V41 was 11th overall in 2006 West, and the competition planning committee will be using V41 for one of the test vehicles to set up the dynamic and endurance courses this year at Western Washington.  We use pure trailing arms in the rear now for our more current cars, they have been much more durable, and are easier to tune for power-on oversteer to make our spooled cars turn.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mu Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2009 at 10:25pm
Originally posted by DrewT DrewT wrote:



Everytime the car gets run, we take bets on which will let go first, a rod end on the rear suspension, or a polaris hub/wheel bearing on the front end.



We use polaris uprights on our front suspension and we've also had a lot of problems.  The bearings fail and seize onto the spindle forcing us to throw the whole thing away.  Anyone else with similar experiences?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p.lewis Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 12:22am
So, some of us use Milliken's Race Car Vehicle Dynamics book, but are there any suspension dynamics references that are appropriate for our off-road audience? Something like the Carrol Smiths books that can fall somewhere between abstract theory and a Haynes manual? You know, just the right amount of intellectual challenge, but motivated by practical uses. Don't get me wrong, RCVD is a great book, but it doesn't say anything about why specific suspension traits would be good for off-road.

I've seen a lot of baja buggy and sandrail books that don't really have a sustantial enough engineering dietary value to make them part of a well-balanced design research meal, and they normally dissapoint me. I've been reading SAE papers and those have been nice, but by no means comprehensive.

Anybody here go to a school with a vehicle dynamics course that uses a text like something I'm trying to describe?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 12:26am
Andy, it sounds like it is time for you guys to get away from Polaris uprights.  Have you done research on ATV forums about the issue you are having?  It may be an issue even on the ATV that your uprights come off of.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 12:59am
Originally posted by p.lewis p.lewis wrote:

So, some of us use Milliken's Race Car Vehicle Dynamics book, but are there any suspension dynamics references that are appropriate for our off-road audience? Something like the Carrol Smiths books that can fall somewhere between abstract theory and a Haynes manual? You know, just the right amount of intellectual challenge, but motivated by practical uses. Don't get me wrong, RCVD is a great book, but it doesn't say anything about why specific suspension traits would be good for off-road.

I've seen a lot of baja buggy and sandrail books that don't really have a sustantial enough engineering dietary value to make them part of a well-balanced design research meal, and they normally dissapoint me. I've been reading SAE papers and those have been nice, but by no means comprehensive.

Anybody here go to a school with a vehicle dynamics course that uses a text like something I'm trying to describe?


I am in a constant search for something like this and have yet to find it.

One of the few things that I have found specifically referencing off-road suspension(not really engineering article):
http://www.rorty-design.com/content/Ed_McCannick.htm

I think one of the big problems with designing Baja SAE suspension is not that there are no references for off-road suspension design but that there are no off-road vehicles similar to ours.  We have the pleasure of not only being off-road but having 0 power to work with as well.  Even if you did find a nice engineering paper about ATV or UTV suspension design, how much of it would really transfer over to Baja?

Production Mini-buggys (Redline Revolt, Protodie Protolite, etc...) are relatively similar to Baja cars in that they are all off-road vehicles built for enthusiasts.  However, they all have gobs of power.  I bet if you dropped power on these vehicles to match the power to weight ratio of a Baja car they wouldn't handle nearly as well as they do.  They also are usually just driven in the woods, or on tracks, or dunes.  Baja makes you build a car that can do pull, rock crawl, mud bog, etc...and it is no easy task to build a vehicle that can do all of those well.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote OctoberSky Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 1:42am
It is by no means as comprehensive as RCVD or at all related to off-road racing (though there are a few references), but the main book I have used is How to Make Your Car Handle by Fred Puhn.  If you comb through it properly, you can pull together a nice excel sheet that will give you all the important numbers on your car's handling.  The book is simple, practical, and will give you some important information.  It doesn't account for some things, but it is close enough for Baja.

If you really want accurate numbers (my final calculated numbers for total weight transfer was within 20 lbs of the basic theoretical calc.) don't be surprised if you find yourself with your car's front/rear suspension detached and sitting on a piece of aluminum round while you try to figure out the other end's roll stiffness using an angle finder and box of lead blocks on a 6-foot lever applying a torque around the CG!  Not to mention weighing physical and/or CAD parts to figure out unsprung weight, etc.  It's definitely worth the work though.

Basically my suspension is designed to minimize front weight transfer and increase rear weight transfer so we can continue oversteering but without a swaybar; the Puhn book helped me to design for that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DrewT Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 3:00am
Originally posted by mu mu wrote:

Originally posted by DrewT DrewT wrote:



Everytime the car gets run, we take bets on which will let go first, a rod end on the rear suspension, or a polaris hub/wheel bearing on the front end.



We use polaris uprights on our front suspension and we've also had a lot of problems.  The bearings fail and seize onto the spindle forcing us to throw the whole thing away.  Anyone else with similar experiences?
 
Yep, that's exactly what we've had problems with on the older cars we used the Polaris hubs on.  The all-time worst example being a pair of front wheel bearings going bad with the car still on the back of our transporter truck on the way to South Dakota.  They were brand new polaris hubs that went on the car days before loading up and leaving; literally no run-time on them.  When we took the car off the truck at the hotel, all the ball bearings were falling out of the hubs and the wheels flopping around loose.  We build our own front uprights now with Timken tapered roller bearings on a live axle, no more problems.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 9:27am
Sounds like you got bearings from the same batch we did. Polaris received a batch of bad bearings in 2007 which were missing balls, causing them to fall apart. They were only used as spares by Polaris, but thats what they send the Baja teams.

We had the same issue at Rochester. We finished up dynamic events, and thought we were good to go for enduro, but a quick check of the car revealed a wiggly wheel, so we pulled it off to find the hub bearings had exploded. Same story on the other side. One of our guys was an intern with Polaris, so he asked around and found out about this bad batch. They knew about it, but the bad bearings were only spares, so they didn't do anything about it.

Anyway, we found a team with some Honda bearings which dropped in, and didn't have any problems after that. Subsequent failures were all with Polaris bearings.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LSantora Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 4:37pm
I have to agree with you guys... You have to use a little of RCVD, Gillespie, Smith, Puhn, etc.  I have yet to find a good off road vehicle dynamics book myself.  Because of this reason, I would argue that our (BAJA) suspension design is more difficult than FSAE.  We have roughly 3 times the suspension travel, inconsistent terrain, unknown terrain for that matter, making all the RCVD style calculations good to get an idea... but not very realistic for what we do. 

One has to wonder though, with all our experiance... will the first comprehensive book on off road vehicle dynamics be written by a baja alumni?  Or better yet, a compilation of papers from all of us on different topics in suspension design?  Futhermore... I think we all make great cadidates to be suspension engineers for some BIG DOLLAR trohpy truck teams that run BAJA 1000.  By the way, when is SAE going to bring in some guys that build trucks for BAJA 1000 to be design judges; it would be nice to see their perspective vs the same corporate "production" engineers from polaris and the like...

Ok I'm off my soapbox...

-Lou
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 5:16pm
Originally posted by LSantora LSantora wrote:

I have to agree with you guys... You have to use a little of RCVD, Gillespie, Smith, Puhn, etc.  I have yet to find a good off road vehicle dynamics book myself.  Because of this reason, I would argue that our (BAJA) suspension design is more difficult than FSAE.  We have roughly 3 times the suspension travel, inconsistent terrain, unknown terrain for that matter, making all the RCVD style calculations good to get an idea... but not very realistic for what we do. 

One has to wonder though, with all our experiance... will the first comprehensive book on off road vehicle dynamics be written by a baja alumni?  Or better yet, a compilation of papers from all of us on different topics in suspension design?  Futhermore... I think we all make great cadidates to be suspension engineers for some BIG DOLLAR trohpy truck teams that run BAJA 1000.  By the way, when is SAE going to bring in some guys that build trucks for BAJA 1000 to be design judges; it would be nice to see their perspective vs the same corporate "production" engineers from polaris and the like...

Ok I'm off my soapbox...

-Lou


I would be pretty cool to get some guys from MillenWorks or Robby Gordon, or BFG, or Goodyear out to our comps...  That would definitely raise the bar!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mu Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 6:24pm
Originally posted by LSantora LSantora wrote:

I have to agree with you guys... You have to use a little of RCVD, Gillespie, Smith, Puhn, etc.  I have yet to find a good off road vehicle dynamics book myself.  Because of this reason, I would argue that our (BAJA) suspension design is more difficult than FSAE.  We have roughly 3 times the suspension travel, inconsistent terrain, unknown terrain for that matter, making all the RCVD style calculations good to get an idea... but not very realistic for what we do. 

One has to wonder though, with all our experiance... will the first comprehensive book on off road vehicle dynamics be written by a baja alumni?  Or better yet, a compilation of papers from all of us on different topics in suspension design?  Futhermore... I think we all make great cadidates to be suspension engineers for some BIG DOLLAR trohpy truck teams that run BAJA 1000.  By the way, when is SAE going to bring in some guys that build trucks for BAJA 1000 to be design judges; it would be nice to see their perspective vs the same corporate "production" engineers from polaris and the like...

Ok I'm off my soapbox...

-Lou
 
Hell, we have about ten times the suspension travel of our formula team.
 
I would love to see a good book on offroad vehicle dynamics.  It would be cool if a bunch of alumni could get together one day and put something together because right now I think a lot of designs are based off of personal experience, guessing and a lot of common sense.
 
This is one of the reasons I keep advocating the idea of a wiki.  It would be great if we could get all of our ideas and experience in one location.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LSantora Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 6:29pm
I think thats a great idea.  Did any of you guys attend the BAJA/FSAE Seminar at Rutgers?  I thought it was EXCELLENT, and SAE needs to do more of that.  Milliken was there, as well as a guy from Joe Gibbs racing.  Furthermore, something like this would be good for Baja alumni to get together as well and discuss some of these suspension ideas.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 7:44pm
Originally posted by mu mu wrote:

It would be cool if a bunch of alumni could get together one day and put something together


I was thinking the same sort of thing the other day!  I think it would have to be slightly more organized and restricted than a wiki, but I like the idea of a collaborative online resource.

I also think it would be really cool if a group of alumni would write a full-on book.


Edited by asims - Oct/19/2009 at 7:45pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mikez Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2009 at 8:49pm
I've also felt that we (as a community) all have some very specific and very valuable knowledge and experience, and that something promoting knowledge transfer (e.g.- wiki, or something similar) would be a great idea.

We are currently looking into what options we have for this and will open a discussion/poll very soon to ask you guys' input on the best path forward.

Thanks for the ideas and support, and (if you have not already) make sure to post and discuss them at the suggestions thread so that we don't lose track of them.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rob71zilla Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2009 at 8:58am
Originally posted by LSantora LSantora wrote:

I think thats a great idea.  Did any of you guys attend the BAJA/FSAE Seminar at Rutgers?  I thought it was EXCELLENT, and SAE needs to do more of that.  Milliken was there, as well as a guy from Joe Gibbs racing.  Furthermore, something like this would be good for Baja alumni to get together as well and discuss some of these suspension ideas.
 
When was this and what was talked about?  I never heard anything about it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p.lewis Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2009 at 6:30pm

The seminar at Rutgers was February 28, this past winter. Here's the info from the email invitation I got (sent from Diane McGuire to registered student section SAE members -- I think)

FEATURED SPEAKERS:
Steve Fox                    Chief Design Judge, Formula Student Germany; Design Judge- Formula SAE® Michigan; Design Event Captain- Formula SAE® Virginia
Doug Milliken             Co-author, Race Car Vehicle Dynamics; Formula SAE® Design Judge
Dan Olson                   Racecar Engineer, Joe Gibbs Racing; former Penn State Formula SAE® team member
Michael Royce            Chair- Formula SAE® Rules Committee, Chief Technical Inspector- Formula SAE®
Seann Bradley             Sales Engineer, Lincoln Electric Co.; Chair, American Welding Society New Jersey Section

AGENDA (subject to change):
9:30 AM:         Check in at ARC Auditorium (Room 103).
10:00 AM:       Michael Royce:  SAE Collegiate Design Series™ safety
10:30 AM:       Steve Fox:  Those Who Cannot Remember the Past are Condemned to Repeat It.  Also, an insider's perspective of what design judges are looking for, the most common design pitfalls and how to avoid them.
12:00 PM:       Lunch
Concurrent session - Formula SAE® 
1:00 PM:         Michael Royce:  Formula SAE® Design Competition Overview, Formula SAE® Technical Inspection and 2009 Rules Changes
Concurrent session - Baja SAE® 
1:00 PM:         Seann Bradley: Overview of Lincoln Electric Motorsports welding program, technical explanation of GMAW & GTAW welding & static demo of GTAW welding techniques.
Combined Group
2:30 PM:         Doug Milliken:  Data for Vehicle Dynamics Modeling – measuring and interpreting tire data and chassis/suspension data.
4:00 PM:         Dan Olson:  Modern Racing Technology, Visualization Techniques (FLIR, High Speed Filming, Dartfish), and Optimization Software (Optistruct).
4:45 PM:         Dan Olson:  Physical Testing for Durability and Performance, Load Frame Testing, & Specialized Rigs for System Testing.
5:30 PM:         Michael Royce:  Closing remarks
5:35 PM:         Informal Q&A session
It would be nice if they put this material on the internet for us.
 
I noticed on SAE.org that there are some documents in the References section of the Baja SAE section for a "Collegiate Road Show" seminar put on in 2006. Link:
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonparker9 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/23/2009 at 6:10pm
We also did a few cars with rocker arms or bellcranks from 05 through 07.


This car won the Polaris Suspension Design Award in Dayton in 05


Pull rods front and rear, the main drawback on this car was the rear bellcranks limited ground clearance



This one has the same front suspension as the picture above and is still running strong to this day, we've bent a few push rods and broken a couple of bolts, but overall its a really reliable suspension.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ukraine Train Quote  Post ReplyReply Direct Link To This Post Posted: Nov/07/2009 at 9:40am
What do you guys think of this? I'm drawing up a buggy as a side project and I've been going back and forth on how to set up the front suspension. I guesstimated the location of the CG but I think it's close enough for now.

I think I've settled on a small amount of layback and then also tilted the upper control arm a little for a small amount of antidive.




Here was my first shot at it and I actually had prodive.



And the old standby with no layback.



Edited by Ukraine Train - Nov/07/2009 at 9:43am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Karan Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2009 at 7:37am
Can someone please tell what kind of joints does one go for in a semi trailing arm suspension for the the rear at the chassis-arm joint and also at the upright..
we're stuck between rod end or hinged joint with bushings... 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote charles ulaval Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2009 at 10:05am
we used rod ends for our semi-trailing arm car back in 2007. I guess it is the easiest way to go...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shocker Racer Quote  Post ReplyReply Direct Link To This Post Posted: Dec/01/2009 at 1:25pm

Last year we ran parallel or zero degrees, with a slight kickback in caster. It worked really well but by adding in a little bit of layback we are hoping to reduce a little bit of stress in ball joint shanks.   This year we are running around 7 degrees of layback angle and then another couple degrees of caster. 

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