Red Lands Racing/Motive Engineering BITD build

[motive]

So what did that stock chassis and cage weigh? I forgot to weigh mine at that point you have yours in that picture. I would think 350-370

Getting warmer. I can't spill the beans with only 2 guesses.

 

[motive]

I like all the tech stuff because it is educational and it allows us non-engineer and fabricators an insight into the process.

OK, you asked for it. Lets get technical about the process. There is an order to go about when designing from the ground up. I say ground up but in reality we have to keep the factory main rails and the stock pivot points. That will effect the order somewhat because we don't have a complete blank page.

I have already talked about step 1 and that is the rules and no matter what you do from this point forward, it has to comply with the rules of your chosen class. After you have read and know the rules you want to design and plan from the outside in.

So the second step in designing a race car is to choose your tires. The suspension, steering, ride height, travel and just about everything else depend on the diameter and width of the tire. BITD rules let us use up to a 30" tire so that is what we are going to use. There has been some talk of upping that to 33" so I designed in some additional bump travel if that becomes the case. Until then, travel will be limited with bump stops to keep from dragging the bottom. You will also want to consider what type of tires you want to run. UTV specific or truck tires? A rounded profile will be less picky about camber. The squared off truck tire will work better the flatter the contact patch is kept. Without being able to change the inner pivot points, the only way to change the camber curve is by changing the spindles so you might not be able to dial in enough. If you can't get good camber characteristics you will have to run stiffer springs and sway bars to keep the chassis and consequently the tires more upright in a corner. As much as sway bars make a car feel better (doesn't roll as much) they do compromise traction at the other end. Weight vs. strength? You can begin to see how tires effect so much more in the quest for the perfect car and possibly reliability.

I would also mention that there is a large variation in tread designs. What type of terrain you are in is an important consideration. Take KOTH for instance. Do you want a tire that has a softer bite to be able to spin on hard surfaces or something that grabs and goes? the latter causing drive train shock when transitioning from sand to the rock. Desert trucks have gotten more aggressive on tread design with M/T tires becoming more common. Is that because power has grown? How does knowing that effect your decision for a UTV?

There is so much to think about with tires that when you come to a decision on what your needs are, you should pick the right tire, not just the ones you can get sponsored with. Although it would be nice if the tire we chose to run does pick us up.

Up next: Wheels.

 

[sand shark]

I guess the chassis weighs 380

 

[badassmav]

I'm so busy watching your build that I'm losing time on mine. I gathered from your offerings thus far, it appears that you are keeping the rear steer layout. I know the snout is pretty short on the XP, and it looks like it would require lengthening the front clip a bit to accommodate a front steer layout. At this time, Holtz over at Coastal is the only XP I saw out there who saw enough validity to convert.

What are your plans for the cv's, and how many degrees are you going to squeeze out of them? What kind of turning radius are you looking at?

From the teaser image you posted, it looks like your motion ratio for the shocks at one end is around .6. Why so high? I assume it is in an effort to minimize the overall weight of your UTE.(for the learners out there, motion ratio is simply the distance a shock strokes for every vertical inch of wheel travel. Referring to a motion ratio is similar to referring to a gear ratio. To say one has a "high" gear ratio, means that the ratio numbers are low, such as a 2.56:1, and vice versa. Our motion ratio is considered to be low at .82 or there abouts. A motion ratio of one (1) is achieved by mounting the shock directly on to of a straight axle so its vertical movement is exactly that of the axle to which it is mounted. It is the physical max, unless exotic linkage(s) like push rods and bell cranks are used, as are in F-1 or Indycar.)

I gathered that your team will be racing in the 2015 BITD series, in the 1900 pro UTV class. Any plans for SCORE next year? I'm not sure where we will be after the 1000. We are uncommitted as of yet. It would be a disappointment if we couldn't have your team to race against.

And lastly, I assume the car is being deigned using a CAD program such as Solid Works. I dabbled a bit with the program a couple of years back, but did not have the time to be comfortable with all of the features. How much of a designers job can a program like that perform? Can you give it all of the necessary dimensional extents like tire size, wheel travel, turning and scrub radius, desired Ackermann, inboard pivot locations, corner weights, mean wheel position, camber and caster values etc., as well as type of suspension such as unequal length a arms, trailing arm etc., and have it spit out drawings and assemblies? I guess that assumes it would perform its own motion studies. I'd imagine it would even produce files to have the tubing notching performed as well. I only use a basic 2d program (my old Plasma Cam software) that I've had for 15 years or so to identify hard dimensions for the sake of time. I also develop .DXF files from the same program for outside cutting of dimensionally sensitive parts. I'm not saying you have an advantage, or are less experienced because of your access to said type of program. I'm just jealous of the tool that others have and wish I had

 

[AReed]

Solidworks can do pretty much as much as you want it too based off of your skill.

 

[badassmav]

Solidworks can do pretty much as much as you want it too based off of your skill.

So, with your relocated rear diff kit, were you able to develop a drawing of the rear frame and the rear diff in the stock location, then tell the program where you wanted the new diff location to be, and that you wanted the mounting method to be a steel box, and it was able to come up with a drawing for the box that you are using, complete with proper clearances, mounting holes, material type and thickness, and flat panel layout? If not, could it have if you gave it all of the pertinent data? I assume Solid Works is a 3 dimensional, interactive application, meaning that it will not design a part that will interfere with adjacent or en route components.

 

[motive]

got a few minutes to I'll answer your questions Reid before heading out for some family time.

We are actually converting to front steer for the one of the same reasons you did. I desire the realastate on the lower arm to mount a shock. I thought you would have deducted that from the teaser. I am kind of allusive though.

The shock motion ratio is just a few clicks short of hitting .6. It is still far better than if we were trying to use the stock shock in a long travel application. There is a specific reason that I am not useing an even longer shock mounted out further but I can't reveal that yet.

I do use solidwork. I have been for about 4 years now and still consider myself a novice. Most of the stuff I have done up till this project has be machined parts so some of the features for motion, sheet metal, ect I am learning as I go. Eric is the solidworks master though. I does make designing tube work very effective. Like we have been discussing in your thread, it makes it easy to bring tubes to a true node and the associated cope required. You can even create a paper template the wrap around a tube to know where to cut.

Solidworks or any other CAD program will not give the any answers if you don't know how to put in the right information. What is nice about solidworks is that you can create things with references. For example, in the shock layout I posted above, the two circles represent the extended and compressed length of the shock. The centers are referenced to be coincidental to the lower A arm, equal distances from the pivot. I also wanted to make the shock 85* from the A arm at full bump. The center point of the line at the top that connects both circles is references to the center line of the car. And its endpoints to touch both circles. Solid works did the math to give an answer of where along the lower A arm the shock mount should be as well as the upper shock mount. Only 3 dimensions were needed to boil down millions of options to the only solution that would work with the desired wheel travel: both shock lengths and 85*. Everything else is a reference that allows things to move around. Equal length, midpoint, tangent, parallel, perpendicular, ect. You can do the same thing with 3 dimensional parts as well but that was not needed in this case.

I don't want to discourage anyone from thinking they have to use a CAD program to design a race car. All it is is another tools. Its a tool that can make things very easy if you know how to use it. If you don't know how to use it, don't think you have to learn how. Your time would probably be better off using the old fashion C.A.D. system. "Cardboard Aided Design!"
And just because something cool can be drawn in solidworks, doesn't mean it can be manufactured.

 

[motive]

So, with your relocated rear diff kit, were you able to develop a drawing of the rear frame and the rear diff in the stock location, then tell the program where you wanted the new diff location to be, and that you wanted the mounting method to be a steel box, and it was able to come up with a drawing for the box that you are using, complete with proper clearances, mounting holes, material type and thickness, and flat panel layout? If not, could it have if you gave it all of the pertinent data? I assume Solid Works is a 3 dimensional, interactive application, meaning that it will not design a part that will interfere with adjacent or en route components.

If solidworks could do all that, we wouldn't need engineers anymore! If you want to see what it can and can't do, I would spend some time on youtube or solidworks site. There are several videos that can very easily show its capabilities.

 

[AReed]

^ Yeah pretty much what he said. We digitize everything first so we really don't have to input much data off a tape measure, just convert some stuff over from the arm. Makes life so much easier.

 

[badassmav]

The Polaris frame, although possibly a better design, is a fatso!
Here's the weight of the 2014 Maverick Max 4-seater, bare frame, as delivered from the manufacturer. It's a nice weight to be at if you didn't have to cut it all off and start over.

 

[motive]

Is that with the factory cage bolted on? Because if it is, it is almost exactly 100 lbs lighter.

 

[badassmav]

Is that with the factory cage bolted on? Because if it is, it is almost exactly 100 lbs lighter.

The frame is raw, and as delivered from the factory. It was weighed (on borrowed scales) as shown.

Hey, do you use a CMM like Alex does to measure the chassis? I feel like I'm chiseling wheels out of a chunk of granite over here! People wonder how come it takes so many hours for me to maintain and prep the Monster Mav (typically 70-80 hrs/week, and up to 100+ hours on weeks prior to a race). I attribute it to me being an old man, I guess. I have become obsessive compulsive in my latter years, so redundancy must play a role as well. But when I see well outfitted shops like Alex's, well let's just say ithat it makes my Wooly Mammoth-tusked body hammer tied to a stick seem kind of archaic. Mac Gyver aint' got nothing on me! Besides the basic powered hand tools (i.e. drill motors, air grinders, etc.), I only have a few powered machines to get me to through the day. A 12" disc sander, a hydraulic tube bender, a 14" chopsaw, and a 15 ton (manual) H frame press. Oh, and some pretty sore and callused hands! I'll add a pic for your amusement.

Well, gotta' go. I need to finish roughing out this wheel.

 

[motive]

I'm not sure what the weight of the polaris frame is without the cage as yours was weighed. The polaris does have some decent ladders to it but they have to go and put all the bolted together sections in it. Unless they are shipping the frame pieces from one plant to another, I don't understand why they would do this. its got to cost more to have all those bolt together bungs. None of them fight tight enough together either to call it a solid joint.

Alex, you are just cheating with that digitizer arm! Tape measure, my big 3 foot caliper, and a digital angle gauge got us though all the measurements we needed. The thing is you can measure down to the .001 all you want, but if what you are measuring was manufactured to .100 tolerances, you are just wasting your time.

Got in a couple hours on the computer and finished up the trailing arm. Just have a few details left to change on the front arm and it will be ready to send off to the laser. Simple, lightweight, strong, and overcomes one of the biggest weaknesses of the stock design. A problem that is only made worse with LT kits.

Think this will work?

 

[NIKAL]

I'm not sure what the weight of the polaris frame is without the cage as yours was weighed. The polaris does have some decent ladders to it but they have to go and put all the bolted together sections in it. Unless they are shipping the frame pieces from one plant to another, I don't understand why they would do this. its got to cost more to have all those bolt together bungs. None of them fight tight enough together either to call it a solid joint.

Alex, you are just cheating with that digitizer arm! Tape measure, my big 3 foot caliper, and a digital angle gauge got us though all the measurements we needed. The thing is you can measure down to the .001 all you want, but if what you are measuring was manufactured to .100 tolerances, you are just wasting your time.

Got in a couple hours on the computer and finished up the trailing arm. Just have a few details left to change on the front arm and it will be ready to send off to the laser. Simple, lightweight, strong, and overcomes one of the biggest weaknesses of the stock design. A problem that is only made worse with LT kits.

Think this will work?

I'm looking forward to seeing this work!

 

[AReed]

Looks good

 

[badassmav]

I'm not sure what the weight of the polaris frame is without the cage as yours was weighed. The polaris does have some decent ladders to it but they have to go and put all the bolted together sections in it. Unless they are shipping the frame pieces from one plant to another, I don't understand why they would do this. its got to cost more to have all those bolt together bungs. None of them fight tight enough together either to call it a solid joint.

Alex, you are just cheating with that digitizer arm! Tape measure, my big 3 foot caliper, and a digital angle gauge got us though all the measurements we needed. The thing is you can measure down to the .001 all you want, but if what you are measuring was manufactured to .100 tolerances, you are just wasting your time.

Got in a couple hours on the computer and finished up the trailing arm. Just have a few details left to change on the front arm and it will be ready to send off to the laser. Simple, lightweight, strong, and overcomes one of the biggest weaknesses of the stock design. A problem that is only made worse with LT kits.

Think this will work?

Zane, in the model shown here, I don't see room for a coil spring to mount on the shock. I know you are not going to run a single stage spring below the reservoir tube, and there is no body above the reservoir to accept the hardware for a spring either. In hopes of designing our next car with external bypass shocks as you have illustrated, I had tried to get approval from Cory to run the coil spring separate from the shock, via a linkage system. His response was that I had to keep the coil-over shock concept intact. Before investing too much time here, I'd run it by Cory for approval. He told us a resounding NO! I'm not too familiar with Polaris, but it looks like you moved the shock back a bit for a more desirable motion ratio. If so, kudos to you. I don't understand (other than to save weight) why the Polaris teams short stroke their shocks. I also agree on how you moved the lower shock position further outboard to reduce the moment that the OEM location introduces into the trailing arm. As your design I'm sure tells you, the load on the rear transverse links will be much lower as a result.

 

[motive]

Haha. Got you. We are not running an external bypass. Rules state one shock only. It was the only shock model i had at the time so I just though it in there. We will be running a longer shock as the stock lengths are way too short. Its kind of crazy that the LT kits are trying to get 20"+ travel out of a sub 10" shock.

Your powers of observation are incredible! After tires and belts, the number one thing that seems to fail on the RZR are the rear radius rods. We have all seen countless pictures of bent upper rods. This is due to the leverage the dog leg in the trailing arm. All the LT kits are about 4" wider which put even more leverage. When the shock bottoms, it tries to pivot the trailing arm about the lower shock mount. The aftermarket companies have found a market for stronger radius rods but it doesn't address the root cause of the failures. In extreme cases where the radius rods are built strong enough to withstand the forces, the mounts rip out as Sims found out at V2R.

I design the shock mount to be perfectly inline with the tire and the trailing arm mount.

 

[badassmav]

Haha. Got you. We are not running an external bypass. Rules state one shock only. It was the only shock model i had at the time so I just though it in there. We will be running a longer shock as the stock lengths are way too short. Its kind of crazy that the LT kits are trying to get 20"+ travel out of a sub 10" shock.

Your powers of observation are incredible! After tires and belts, the number one thing that seems to fail on the RZR are the rear radius rods. We have all seen countless pictures of bent upper rods. This is due to the leverage the dog leg in the trailing arm. All the LT kits are about 4" wider which put even more leverage. When the shock bottoms, it tries to pivot the trailing arm about the lower shock mount. The aftermarket companies have found a market for stronger radius rods but it doesn't address the root cause of the failures. In extreme cases where the radius rods are built strong enough to withstand the forces, the mounts rip out as Sims found out at V2R.

I design the shock mount to be perfectly inline with the tire and the trailing arm mount.

Yeah, you can call me Captain Obvious, 'cause this stuff is like a giant red flag when I view it.

 

[UTVUGJake]

Thrilled at the level of discourse going on! I will jump into this thread a little more tonight when I'm on my leisure forum time. Just wanted to say keep it up, I haven't had nearly enough chances to discuss vehicle dynamics in an off-road context.

 

[badassmav]

Haha. Got you. We are not running an external bypass. Rules state one shock only. It was the only shock model i had at the time so I just though it in there. We will be running a longer shock as the stock lengths are way too short. Its kind of crazy that the LT kits are trying to get 20"+ travel out of a sub 10" shock.

Your powers of observation are incredible! After tires and belts, the number one thing that seems to fail on the RZR are the rear radius rods. We have all seen countless pictures of bent upper rods. This is due to the leverage the dog leg in the trailing arm. All the LT kits are about 4" wider which put even more leverage. When the shock bottoms, it tries to pivot the trailing arm about the lower shock mount. The aftermarket companies have found a market for stronger radius rods but it doesn't address the root cause of the failures. In extreme cases where the radius rods are built strong enough to withstand the forces, the mounts rip out as Sims found out at V2R.

I design the shock mount to be perfectly inline with the tire and the trailing arm mount.

I read a post here not too long ago from a member who has high clearance radius rods on his Polaris, and couldn't figure out why after every aggressive ride, the toe in his rear tires would change. Big Jim nailed his response when he suggested that the lower, high clearance rod was being "pulled"out.

Exactly, Cognito man! The way the shock mount is not inline with the loaded axis of the trailing arm introduces what engineers refer to as a "moment". In lay-mans terms, it is a twisting or bending load. The wheel is supported by the spring, which is not directly inline with the tire contact patch and the front pivot point of the trailing arm, so the trailing arm wants to twist. The radius rods are what is stopping the twist from occurring. The lower radius rod sees tension loads, while the upper rod sees compression loads. The bends put into the lower arm by the manufacturer are being "pulled" out, in essence increasing the length of said arm with every impact that exceeds the stiffness of the arms design.

I've seen 2 wise mfgs. offering radius rod kits for the Polaris (not saying that if a kit is not of this configuration that it is improper, wrong or bad). One kit had simply a larger diameter bar than the other to accept the increased loads from its mounting location (i.e. top or bottom), and another who welded theirs from plates, forming a "boxed" section. It is obvious that they are aware of chassis loading, and have adapted their products to address said issue.