Yamaha Truly Unlimited UTV - Rustfish Racing 2921

tatum

Hans Solo - 2009 UTV Baja 500 & 1000 Winner - UTVU
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Well it's an interesting topic. These turbo motors with injectors and a good tune are making as much power as the ecotecs pushing class 10 cars around and we know those cars are fast. So without some limits I think you run the danger of someone just building basically a class 10 with a UTV engine and running wild. Keeping the diff, axles etc makes sense.

I just think the car counts are so high because basically anybody can buy one from a dealer (financing baby!), and with some reasonable garage skills and race parts put a decent car on the track. I think the number of people who are gonna spend class 10 (or more) type money on a UTV is much much smaller. I love the fact that UTV racing has exploded, hell I bought my first UTV just a couple months ago after seeing what they can do....it would be a shame to turn it into a class where you can't win a race if your car isn't $100k plus.

Anyway a friend got a few of these yamahas into the shop a few weeks ago and they are undergoing desert race surgery. It will be interesting to see what they come up with. Are there many yamahas racing desert and if so how are they doing? At first blush I'd wonder how stock size axles and cv joints would hold up with the geared trans.
The HP these new turbos are making are going to require more high dollar parts and fab to keep up with the top dogs IMO. There are quite a few teams with $ now and its only going to get faster.

As far as the Yamaha it think the jury is still out on the rear suspension design for desert and the front suspension pivot points are only about 6 inches apart.

If the 75k price for a RG built Arctic Cat is true and gets to race pro production it just might be a bargain. Unfortunately I didnt get to get in it at the 1k but everything about them screams pure race car. Thats what I love about this build and hope it kicks ass.
 
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kornfed

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Well it's an interesting topic. These turbo motors with injectors and a good tune are making as much power as the ecotecs pushing class 10 cars around and we know those cars are fast. So without some limits I think you run the danger of someone just building basically a class 10 with a UTV engine and running wild. Keeping the diff, axles etc makes sense.

I just think the car counts are so high because basically anybody can buy one from a dealer (financing baby!), and with some reasonable garage skills and race parts put a decent car on the track. I think the number of people who are gonna spend class 10 (or more) type money on a UTV is much much smaller. I love the fact that UTV racing has exploded, hell I bought my first UTV just a couple months ago after seeing what they can do....it would be a shame to turn it into a class where you can't win a race if your car isn't $100k plus.

Anyway a friend got a few of these yamahas into the shop a few weeks ago and they are undergoing desert race surgery. It will be interesting to see what they come up with. Are there many yamahas racing desert and if so how are they doing? At first blush I'd wonder how stock size axles and cv joints would hold up with the geared trans.
There are not a lot of Yamaha builds in desert. There are a few abs once in a blue moon they get one to top 20. They are very good at short course.

The main issue is the rear suspension. My opinion is that this was a terrible design. Hence this new design. As far as the stock cv and axles sizes, I don't think the Yamaha guys are breaking those much. We did dive research and they seem pretty tough, but cannot go across desert fast with the rear suspension.


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kornfed

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A few thoughts on steering geometry:

(this will take a few paragraphs, so bear with me. I promise it will be worth it in the end)

Your CAD guy was smart in designing around the OEM components. This is how building a car in a timely fashion is achieved. If you mandated a completely different and opposite steering layout, what would he have used as input for spindle geometry? Without successful past experience remodeling front spindles for front steer applications, he would be spending countless hours, and probably days using approximate figures for non existing hypothetical spindles. It surely would have stagnated the forward momentum of the design progress at that point. Like I said earlier, the decision to front steer our Maverick added 2-3 weeks extra build time.

As an eager young fabricator in the late 80's preparing to build my first race truck, I dove head over heels into reading everything I could get my hands on about race car engineering and suspension dynamics. No internet back then boys and girls. I'm talking libraries and mail order books. Big, fat boring books. When build time came, I carried over everything I could from what works in a road racing environment, and religiously applied those fundamentals into the truck I was building. I took rear steer F-250 camper special I beams and spindles, and forced them into complying to the front steer conversion I was performing, and still maintain proper steering characteristics. Enter Ackermann steering.

Lay-mans alert:
So, Ackermann steering was discovered in the 17th century for the purpose of helping horse drawn carriages corner with less resistance, and therefore, less fatigue to the horse (I told you, it's nothing that hasn't been done before!). Ackermann steering, quite simply is the ability of the inside tire during a cornering maneuver to steer at a sharper angle than does the outside tire. This is desirable because it is following a tighter circle than the outside tire is, therefore must turn at a sharper angle to avoid the friction caused by tire "scrubbing".

Anyhow, I remember watching the truck I built as it was being pushed through contingency at its first big SCORE event. Just a few trucks ahead of him was another new class 8 "hi-tech" build that used the same I-beam/spindle combination that I did (copycat!), except when converting his spindles to front steer (by converting, I mean just switching assignments for each spindle, The driver side spindle is rotated 180 degrees and used on the passenger side of the vehicle, and vice-versa. Then, wala! Instant front steer), he left the steering knuckles in the stock location, essentially introducing the reverse effect of Ackermann into his steering geometry. Suffice it to say that while we were able to push our truck around the corner, they could not do the same. They had to start it up and drive it around the corner. Between their front tires scrubbing, and the rear tires squealing due running a solid rear axle (spool), the resistance to turning was ferocious.
Then, the next day while watching both trucks entering into Osbornes Wash, it all became crystal clear to me why I spent the time to do it right. As our trucks front tires grabbed hold, and as though on rails, guided the vehicle effortlessly around the corner, while when the other truck negotiated the same corner, the front end immediately "pushed" hard to the outside of the turn, slowing the truck down considerably while the rear tires shot rooster tails high into the air as they struggles to push the lazy front end through the corner.

Fast forward 25 years, and I'm watching RG negotiating a kink in an otherwise endless straight pole line road in Baja. Now, these last 3 paragraphs are not narcissistic-ally added in an effort to toot my own horn, but rather to share a very poignant revelation that occurred to me at that very moment, which was this:
Perhaps pure Ackermann steering geometry in today's race cars is not the best or smartest design criteria. What I saw was a truck pivoting around the outside front tire as it crisply changed direction at over 90MPH. I thought maybe that due to weight transfer, and the higher slip angles the outside tire sees over the inside tire during a high speed turn, just maybe modern race vehicles, because of their vastly increased average speeds would be better off with "anti-Ackermann" steering. The modern off road racer is light and fast, and rarely is seen at low speeds "plowing" through a turn. Conversely, they are usually observed powering through lower speed corners at opposite lock, hard on the gas.

So, to Ackermann, or not to Ackermann. That is the question I ask. How say you Todd and Haans?
It's certainly a hard point to argue against, because when you think about it, the outside tire has more influence during a high speed turn as it is more heavily weighted than the inside one. It will consequently will see higher slip angles, so could benefit from turning a bit sharper by design, than the inside tire.

So Dave, for the sake of your thread, and input to it, possibly phase 1 will benefit from true Ackermann, while phase 2 with its more wide open motor and resultant higher speeds, will not.
Wow ok I just learned a lot there. And the idea that Ackerman at lower power would be tuned differently than a higher powered car that can generate oversteer through throttle. Mind blown. We will discuss for phase 2... Damn. Good stuff...


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zambo

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A few thoughts on steering geometry:
.
I'm not a car designer but over the years I've talked and thought about ackerman a few times. I think that ackerman still is important in a desert race car. You certainly don't want reverse ackerman like that truck with the flipped knuckles you described.

The thing that determines the need for ackerman and how much isn't the speed of the vehicle but the angle of the turns. The flat track guys don't need a whole bunch because all of their turns are long sweepers. The angle of the inside tire is barely different than the outside tire. Of course in desert we have high speed roads and sweepers but there are tons and tons of tight, twisty trails. These tight trails are where UTVs really shine. It would be a mistake IMO to do anything to a UTV that gives up its advantage in the tight stuff because you want it to go faster on wide open stuff, and that's not limited to just ackerman design. Anybody who has been in a desert car and had the front end plow on a tight trail knows the frustration. Getting the car to stick to the ground is a huge consideration and it quickly becomes unstuck when a tire starts plowing instead of rolling.

Keep in mind also that even if a car is flat tracking around a turn, steering in the opposite direction while the back end is controlled with power, the outside tire is still going around a bigger radius than the inside tire. Ackerman still helps because either way you turn the wheel the front tires still toe out a little. Another option is to deliberately put a little toe out bump steer into the design, so that when you go around a turn and the outside tire gets weighted, it toes out a little. That way when you steer, the tire never wants to go the opposite way you're pulling on the wheel. Imagine if it toed in at bump, then when you turn the tire would toe in and you'd have to relax the wheel, then the car would straighten and you'd have to steer more, etc. Not what you want.

Maybe none of that is right but just an opinion for folks to consider.
 
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badassmav

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Don't get too caught up on front steer geometry and ackermann right now. I'm just a big proponent of it because I saw real world results of its effects. Too much ackermann at speeds can work against itself, causing both front tires to lose traction as they fight to be the dominant steer tire. As you said, the Cad guy said it was addressed, and is fine. IMO, the jury is still out as to what is and what isn't practical to carry over from road racing geometry. You are in the unique position to explore this a bit. Being that you are re-inventing your build in the near future, you can try a little more of this, or a little less of that and see how it affects the handling. I would certainly fab up some front steer spindles with different parameters. Then you can test them against the rear steer set up and see if it really is worth the effort and disciplines it put you through.

Although your car is probably already designed, I'll touch on other front end geometry consideration. Your front handling characteristics are equally influenced by other criteria like caster gain and steering axis inclination. Roll centers and roll moments, blah blah blah.... Static alignment settings are huge as well. When choosing wheel offsets in the front, be sure to consider the steering inclination angle on your spindles, and how when combined with the backspacing on your wheels can create an excessive scrub radius. This condition can also cause the front wheels to break loose while steering through a turn. I like to build in a little scrub, as it gives the driver feedback on whats happening via the steering wheel. I try to keep the scrub radius under 1/2". I'm sure your CAD guy has already considered much, if not all of these criteria, which is probably one of the reasons for keeping the stock front spindles in the beginning, as he can factor in all these settings up front while on the computer.

This is exciting shit you are doing here. Lotta people viewing what your doing, and not participating in the thread. I'd be curious as to who is quietly watching (probably a few waiting for me to put my foot in my mouth. Haha!) The last time I remember an open, publicized engineered build thread was when Ryan Laidlaw and the Uta-hee-ans built their car. Oh, one more question; Are your driving skills at the same level you're hoping your car will be at? No offense, but I haven't been following racing much lately other than Badass Johnny and his truck efforts, and Marc's DNF streak. (Didn't Need to Fire me). (Ouch!).
 

kornfed

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Don't get too caught up on front steer geometry and ackermann right now. I'm just a big proponent of it because I saw real world results of its effects. Too much ackermann at speeds can work against itself, causing both front tires to lose traction as they fight to be the dominant steer tire. As you said, the Cad guy said it was addressed, and is fine. IMO, the jury is still out as to what is and what isn't practical to carry over from road racing geometry. You are in the unique position to explore this a bit. Being that you are re-inventing your build in the near future, you can try a little more of this, or a little less of that and see how it affects the handling. I would certainly fab up some front steer spindles with different parameters. Then you can test them against the rear steer set up and see if it really is worth the effort and disciplines it put you through.

Although your car is probably already designed, I'll touch on other front end geometry consideration. Your front handling characteristics are equally influenced by other criteria like caster gain and steering axis inclination. Roll centers and roll moments, blah blah blah.... Static alignment settings are huge as well. When choosing wheel offsets in the front, be sure to consider the steering inclination angle on your spindles, and how when combined with the backspacing on your wheels can create an excessive scrub radius. This condition can also cause the front wheels to break loose while steering through a turn. I like to build in a little scrub, as it gives the driver feedback on whats happening via the steering wheel. I try to keep the scrub radius under 1/2". I'm sure your CAD guy has already considered much, if not all of these criteria, which is probably one of the reasons for keeping the stock front spindles in the beginning, as he can factor in all these settings up front while on the computer.

This is exciting shit you are doing here. Lotta people viewing what your doing, and not participating in the thread. I'd be curious as to who is quietly watching (probably a few waiting for me to put my foot in my mouth. Haha!) The last time I remember an open, publicized engineered build thread was when Ryan Laidlaw and the Uta-hee-ans built their car. Oh, one more question; Are your driving skills at the same level you're hoping your car will be at? No offense, but I haven't been following racing much lately other than Badass Johnny and his truck efforts, and Marc's DNF streak. (Didn't Need to Fire me). (Ouch!).
Ha that is a funny question. My skills will not keep up with this car. I am solid in the Rustfish 1992, but cannot drive to this level yet. Kent Pfeiffer however is a different story. He has 14 or 15 SCORE wins and even more in BITD... He can drive to the limit. He has wins in class 1 and class 10 and bikes.

There will be no shortness of talent when this car is on the course.

Getting the car to the course is another matter indeed... Few pictures from the weekend. Long way to go and STILL NO SHOCKS....!!!! Ugh...



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badassmav

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It looks like it still needs to be wired and plumbed. Do you have the axle/cv/stub axle/hub assy's yet?
In looking at the front lower a arms, it appears that the outside portion of the axle runs in front of the boxed section of the lower arm. Is that correct? It also appears that at ride height, the bottom ball joint position will be trailing the top ball joint position, incurring a negative static caster setting. Am I seeing that right?
I still say if you don't address the mounting plate vulnerability at the end of the rear trailing arms where the wheel bearing plate bolts to the arm, the joint will fail far before its time. Most likely a crack will develop at the heat affected zone of the weld on the bottom/lower section where the bearing receiver plate welds onto the rear face of the trailing arm. Those cracks that develop right at the root of the weld are common place if there is any undercutting of the weld where the parent material and filler rod meet. I assume you used normalized 4130 to fabricate the trailing arm. Is the weldment stress relieved?
Also wondering why the lower rear shock bolt orientation on the trailing arm is not positioned parallel to the pivot axis of the arm to which they are mounted. Although it is a trailing arm, the shocks should be mounted similar to an a-arm layout to avoid binding, and the top shock mount should be plumbed leaning towards the center of the 2 trailing arm pivots.. It just looks like the shock bottom bearing will be close to binding at 22" of wheel travel. There will certainly be a learning curve in regards to the rear the trailing arm conversion.
 

kornfed

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We have everything except for the shocks and the fuel cell. Kind of important elements. The axle does come ahead a bit on the front, but not a lot. The comment was don't hit rocks. Also it would take a pretty tall rock to get there.

The other items are addressed by the limiting of the front travel. What you are seeing here is past the point of droop.

On the rear yes it is braced and chromoly end to end the welds are double layered and aligned with the arm. I have seen it move, but we don't have the shocks so we cannot do the final mounting for the brackets.

Frustrating to have it this close and not be able to do the final design and Fab until we get the parts. Hope we don't have to redo the rear top mounts. Frustrating but what can you do...


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badassmav

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I didn't notice in any of the pics that the upper rear shock mounts were done. Good for you. I'm going to do my best to make it out to the Laughlin event. Its been awhile since I wore my spy glasses, and things are a changin'!
If in the 11th hour you need help wrapping up whatever, let me know. I'm only 2 hours south of you (assuming the car is in Costa Mesa). Will work for Guinness!
 

kornfed

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I didn't notice in any of the pics that the upper rear shock mounts were done. Good for you. I'm going to do my best to make it out to the Laughlin event. Its been awhile since I wore my spy glasses, and things are a changin'!
If in the 11th hour you need help wrapping up whatever, let me know. I'm only 2 hours south of you (assuming the car is in Costa Mesa). Will work for Guinness!
Ha nice. We will probably be wrenching on it in line at contingency... ;-)


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badassmav

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When we made the switch to polaris, we left from san diego for the Parker race 3 hours before the green flag. Marc was flying towards parker at 100 mph, while I was in the trailer wrenching on the car. We contacted Cory from the road and he had one of his guys meet us as we pulled into the s/F area to tech the car. miss the start by 15 minutes, but we're allowed to join the race. If I make it there, I'll search you out and help in anyway I can. I'll pm you my cell.
 
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motive

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I'm behind on reading all the latest at UTVUG. Its exciting to come back from awhile and see a build such as yours. Everything is looking top notch.

To add to what Reid has said about front steer, ackerman, and bump steer. Yes you can design a rear steer with no bump steer at a certain steering angle only! Usually straight ahead but like Reid commented that when you add the steering arm angle for ackerman, caster changes if you have anti-dive and every other factor you will find it near impossible to eliminate bump steer if the wheels are turned at any significant angle. This is an issue often overlooked by designers including us CAD junkies that can use a computer to spit out the ideal rack end/tie rod locations for any particular point of suspension travel/steering angle. The truth is that is pretty much impossible on a front steer setup as well with a single plane steering motion. But due to longer tie rod lengths and better angles, bump steer can be minimized to the point it is negligible. However there are more than one TT designer out there that has incorporated dual axis steering motion to eliminate ALL bump steer at any possible suspension/steering angle. There is also some recently uploaded video of a new car from a highly touted designer/builder that has very visible amounts of bump steer with the car traveling in a straight line through the woops.

I think at the end of the day there can be a lot of "ideals" missing on a design that can be overcome if not even noticed by a talented driver. The human brain is a super computer that can compensate for an infinite amount of variables. Funny thing is some drivers will be able to tell if a clicker is moved just one click or tire PSI is off by just 1 and other drivers will be unable to tell if drastic changes are made. Really the ultimate design is one that feels good in the drivers hands and he feels confident to push his own abilities to the edge.
 

Rynomx785

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I'm behind on reading all the latest at UTVUG. Its exciting to come back from awhile and see a build such as yours. Everything is looking top notch.

To add to what Reid has said about front steer, ackerman, and bump steer. Yes you can design a rear steer with no bump steer at a certain steering angle only! Usually straight ahead but like Reid commented that when you add the steering arm angle for ackerman, caster changes if you have anti-dive and every other factor you will find it near impossible to eliminate bump steer if the wheels are turned at any significant angle. This is an issue often overlooked by designers including us CAD junkies that can use a computer to spit out the ideal rack end/tie rod locations for any particular point of suspension travel/steering angle. The truth is that is pretty much impossible on a front steer setup as well with a single plane steering motion. But due to longer tie rod lengths and better angles, bump steer can be minimized to the point it is negligible. However there are more than one TT designer out there that has incorporated dual axis steering motion to eliminate ALL bump steer at any possible suspension/steering angle. There is also some recently uploaded video of a new car from a highly touted designer/builder that has very visible amounts of bump steer with the car traveling in a straight line through the woops.

I think at the end of the day there can be a lot of "ideals" missing on a design that can be overcome if not even noticed by a talented driver. The human brain is a super computer that can compensate for an infinite amount of variables. Funny thing is some drivers will be able to tell if a clicker is moved just one click or tire PSI is off by just 1 and other drivers will be unable to tell if drastic changes are made. Really the ultimate design is one that feels good in the drivers hands and he feels confident to push his own abilities to the edge.
Can you elaborate on single plane steering motion vs dual axis steering motion?

This all very interesting and I am trying to keep my head above water. lol
 

kornfed

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A few more pictures from this weekend... I have no idea what this means, but if you have questions, I can ask Will. Will stated that these measurements are from the steering arm that is on plane with the spindle center line.

This shows the castor and bulkhead angles are dead on...

IMG_0900.JPG IMG_0901.JPG IMG_0902.JPG
 

motive

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Can you elaborate on single plane steering motion vs dual axis steering motion?

This all very interesting and I am trying to keep my head above water. lol

A traditional steering rack rather it be an end load, center load, or one with a bump steer bracket such as the Redlands or Scanlon car only moves in one plane. In and out, from side to side. It gives a lineal movement equal on both sides. If steering is locked dead straight you can use a computer, trial and error, and ratios of steering arm height to ball joint locations to get very near 0 bump steer with this set up. In fact there is usually more than one location that will accomplish 0 bump steer or vary close to it. The problem is when steering lock is applied the tie rod end at the spindle moves in an arc, thus at different distances that what is applied at the rack. This will create bump steer. The trick is to use the longest possible tie rods and the one of the possible inner tie rod locations that minimize bump steer in a turn. This is one of the huge benefits of a front steer set up. Longer tie rods via a narrow inner location of the tie rod and a further outer tie rod location via a steering arm that outside the KPI for positive auckerman.

Duel axis steering can be accomplished many ways but most common would be some sort of swing set steering. This can be moved by a lineal motion of a rack or piston or by the rotary motion of a steering box. What is important is that the inner tie rod location needs to travel in an ark. Without the use of a parametric CAD program like Solidworks is would be extremely hard to find a steering axis that corresponds perfectly at any suspension/steering location.

To further make these magical no bump steer locations and steering axises complicated, when you have anti-dive (increasing castor) designed in, such a polaris incorporates, your spindle rotates along the castor axis as the suspension cycles. So now the height of the steering arm does not travel in a lineal relation to the wheel motion!

I do not know what the builder is trying to show with the pictures and the digital level. The angle of the top of the steering arm means nothing. It might be canted on purpose to make sure the tie rod has enough movement in a particular direction. If he is trying to show castor, that is not the way to measure it. And castor does not need to correspond to the angle of the bulkhead. What would be more interesting to show is the angle of the upper a arm axis vs. the angle of the lower a arm axis!
 
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kornfed

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Will said someone in the peanut gallery would say that is not how to measure. His response is as follows...

The Castor and Bulkhead angle is spot on. That is what he is showing. Also as for the way he is measuring it. He has the spindle on line with the steering arm so he can measure this way.

Also it is in the computer this way as well. He got the numbers to the specs in the design. Not easy to do with actual metal.

Anyway, will post updates as we go...


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zambo

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Like motive, I too have no idea what he's trying to show with those two pictures of the level. That ain't caster. Ok back to the peanut gallery.
 

badassmav

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I understand Ryans confusion regarding the bulkhead angles. I consider a bulkhead to mean the same thing as a firewall. Typically a somewhat vertical plane that separates the driver compartment from the front end of the vehicle. Since positive caster is the result of the upper ball joint being positioned behind the lower ball joint (as viewed from a side elevation) at static ride height, and is measured by the angle an interconnecting line joining both ball joints leans backwards and away from a vertical plane, any bulkhead reference is irrelevant to whether or not caster is present.

It sure appears that there is near zero caster, and possibly even a bit of negative static caster at the time the pics were shot. In order for there to be anti dive, the pivot axis of the upper arm cannot be parallel to the pivot axis of the lower arm (again, as viewed from a side elevation), but rather it must angle down towards the rear of the car so that when the a arms bump, the lower mounted ball joint travels vertically, while the upper mounted ball joint pivots slightly rearward, increasing the caster angle as the front end dives, in order to fight against the nose diving, hence the term "anti-dive". The way it combats nose dive is by resisting vertical movement of the wheel by directing the top of the wheel to move backwards towards bump while the lower joint moves only vertically. To visualize this, just picture the top a arm pivoting on a vertical plane instead of a horizontal one. In this very hypothetical example, the suspension would be in "lock out" mode, and would be impossible to bump at all, as the upper a arm's pivot axis opposes the lower a arm's pivot axis.

Camburg ran a good example of a dual axis steering pivot on the 7200 truck Marc raced 10 years or so ago. A center steer Howe rack linked to 2 symmetrical idler arms that shared the same pivot axis as the spindles (as viewed from a front and side elevation), and mimicked the pivot length of the steering knuckle on the spindles. When the wheels were turned, and the steering knuckle rotated to the side and back, the inner tie rod joint did the same. I was strong, simple, effective, and easy to build. It was badass.

Hey Dave, how many times has Will referred to us as "effen armchair engineers", stating "That's why I stay off of those stupid things". Haha! Please don't take it personally. Ryan summed it up well when he said, "the ultimate design is one that feels good in the drivers hands". Due to an infinite amount of variables off roaders face, there is no perfect (or right) design. From body roll, to tire coefficients, to g loading of the shocks, it all depends on the balls, or blindness I guess, of the racer as to the predicament one may find him or her self facing. I remember talking to Lance from Kuster way back when he was building some massive shocks for the truck we built. He figured out our spring rates based on a factor of 5 g's at full bump. That's as much as a Formula One driver will ever see during a race!

For what it's worth, your car , and the efforts of you guys to upturn every stone, is rarely attempted in this class, AND is yet to be met with much success (with the exception of Holtz's builds. He's not afraid to convert steering and load carrying arm assignment to the front of his cars, but overall, he doesn't dive in near as deep as you and Motive have.) Who am I to talk. The car I built was the heaviest and slowest car out there....................(ahem, to ever win a championship!)
 

Rynomx785

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Thank you for both for taking the time to explain that.

How much anti-dive is built into a RZR? I haven't payed attention much prior to this but the arms seem to be pretty close to parallel.
 

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