Limitless Short wheelbase limitless

[Overkill]

Parts started showing up over the last few days and I could use some input for a few things I can't decide. The goal is to gain some performance out of my race Typhon by dropping the cg and adding limitless aero, even though my instincts (as a mechanical engineer) tell me the wings won't make a tangible difference at low speeds. The biggest area the car struggles is front end grip and really needs less caster.

Current setup:
-TLRT Typhon
-Limitless shocks and HR towers. 27lb/in springs and 8 hole tapered pistons.
-hobbywing xr8 g2s and 1900kv motor
-powerhobby 54/100 grippers
-diffs: 5k/5k/3k
-track: smooth asphalt parking lot that's pretty small.

New parts:
-king hobby carbon fiber chassis
-limitless aero
-proline axis body
-EMP spool
-GRP xm2 slicks

The plan is to use the Typhon chassis as a drill template to move the rear end to a 328mm wheelbase. I'm pretty sure I'll center the drivetrain but I can't make up my mind on the rest of the layout
-spool forward or rearward
-motor forward or rearward
-i kind of want to do saddle pack batteries but I already have normal 4sHV batteries.
-any ideas to decrease the caster beyond the minimum adjustment?

 

[Dan B.]

The caster can be mitigated to a point by moving the inner upper arm spacers to the opposite side.
If speed running, center the mount, and reverse it so the motor is front mounted. Thanks to @K-BASH for that tip, it made a world of difference in stability.
And just curious, but if you want a 328mm chassis why not just start with your Typhon chassis, or Scorched equivalent?
Also, don’t reduce caster too much. At speed, it won’t track as well. If you’re concerned about too much caster influencing turn-in and responsiveness I get it, but then saw you would be running a spool. That suggests a dedicated speed runner? If so, caster is your friend. If it’s a street basher or a track racer, then you’d want to run a center diff and not a spool.
And then I noticed you’re going to run a Pro-Line Axis body? So this will be a buggy? Now I’m a little confused as to the direction of your build. What will you be doing with it?

 

[K-BASH]

I've built a few,tried many different setups..here's my current an best to date..move all weight foward for best handling for speed..I helped my buddy mitch build this car an basically how I'd mine

 

[Overkill]

The caster can be mitigated to a point by moving the inner upper arm spacers to the opposite side.
If speed running, center the mount, and reverse it so the motor is front mounted. Thanks to @K-BASH for that tip, it made a world of difference in stability.
And just curious, but if you want a 328mm chassis why not just start with your Typhon chassis, or Scorched equivalent?
Also, don’t reduce caster too much. At speed, it won’t track as well. If you’re concerned about too much caster influencing turn-in and responsiveness I get it, but then saw you would be running a spool. That suggests a dedicated speed runner? If so, caster is your friend. If it’s a street basher or a track racer, then you’d want to run a center diff and not a spool.
And then I noticed you’re going to run a Pro-Line Axis body? So this will be a buggy? Now I’m a little confused as to the direction of your build. What will you be doing with it?

I guess I left out some details. Local hobby shop does 1/10 touring car racing in their parking lot and does a courtesy 1/8 buggy class. The buggy class is open except for wheelbase. The lot is tiny so short(er) wheelbase is your friend. See the picture.
The purpose of starting with a limitless chassis and not a buggy based chassis is to have the proper pickup points for the wings/diffuser and lower cg for everything mounted in the middle.
For caster, I already have it adjusted to minimum but it still stands the tires up on the corners which is probably the main contribution to the lacking mid corner grip in the front and wearing out the inside of the tires. It's not camber wear bc the static camber is zero degrees

 

[Dan B.]

.For caster, I already have it adjusted to minimum but it still stands the tires up on the corners which is probably the main contribution to the lacking mid corner grip in the front and wearing out the inside of the tires. It's not camber wear bc the static camber is zero degrees

Caster has no bearing at all in terms of “standing the tires up on the corners.“ It’s merely the measure of trail (included angle) of the steering knuckle. If your tires are on edge, it’s a camber issue. How are you measuring?

 

[Overkill]

Caster has no bearing at all in terms of “standing the tires up on the corners.“ It’s merely the measure of trail (included angle) of the steering knuckle. If your tires are on edge, it’s a camber issue. How are you measuring?

At full lock. The more caster, the more the tire flops over vs rotating on the contact patch if the steering axis is closer to vertical. I've tried positive camber to get the contact patch mid corner and it was great and the traction was there but in a straight line the front end didn't hook and was all over the place.

 

[Dan B.]

At full lock. The more caster, the more the tire flops over vs rotating on the contact patch if the steering axis is closer to vertical. I've tried positive camber to get the contact patch mid corner and it was great and the traction was there but in a straight line the front end didn't hook and was all over the place.

View attachment 305279

Gotcha. I was still thinking only in terms of straight line speed running. If you already changed around the shims up top on the upper a-arm, then I’m not aware of anything else you could do to reduce the caster any more. Unless the TLR has some other tuning options in regard to caster? Maybe somehow change the geometry of the upper arm? It doesn’t seem like you could do much with the lower arms because of their relationship with the bulkhead, shocks, shock tower, etc.
What about narrowing/grinding a few mm off the inner arm where the hinge pin goes through to allow you to move the arm further back and increase the number of spacers or use a bushing at that point for adjustment? Just spitballing.

 

[Overkill]

So the ebay special chassis gave me a headache right out of the gate. The holes for the steering post screws were 2mm too close together and I had to drill them out. Not convinced it's going to work yet but lesson learned, listen to my instincts on no name (king hobby) parts and stick with the known companies. With those being my reference holes and oversized it took some extra care to align the typhon chassis but I got it straight. Holes are drilled. I'll fire up the angle grinder in the next couple days when the kids aren't asleep upstairs, cut the back off and see how well the front and rear line up when they're installed.

 

[Overkill]

Got the rear end cut off and ground to match the profile so the diffuser mounts up. Front and rear end are back on. Next is drilling for the motor/spool mount holes and grinding the relief for the spur. Also the scorched top deck finally showed up so I can cut that down once the center is mounted. Starting to look like a car again

 

[SrC]

Caster has no bearing at all in terms of “standing the tires up on the corners.“ It’s merely the measure of trail (included angle) of the steering knuckle. If your tires are on edge, it’s a camber issue. How are you measuring?

The TLRT Typhon has adjustable caster scrub angle positioning with the pIlls as well to some degree. Same with Front Camber. And roll center. Chassis roll Center will also counter the Negative Caster angle if you do it correctly. A rotating chassis will benefit with some Neg caster while running and under G force loads. When driving it. On the bench sitting there, this is not obvious to the naked eye. Tires just appear to drive on its edges when Steering is lock to lock.
Many overlook this completely, never even reading the TLRT Manual and opening the bag of Various mounting Pills.

 

[Overkill]

It's close to being done. Just needs the sides of the chassis cut off, Esc calibrated and programmed and paint. I was fighting the urge to change to a spare MMX8S and 1717 I had but lost that battle with myself. Also changed to a 170sbl I had because the castle esc cant run the spektrum at 8.4v. I shortened all the spacers on the scorched brace so the pieces could sit flat on top of each other and get screwed together.

The TLRT Typhon has adjustable caster scrub angle positioning with the pIlls as well to some degree. Same with Front Camber. And roll center. Chassis roll Center will also counter the Negative Caster angle if you do it correctly. A rotating chassis will benefit with some Neg caster while running and under G force loads. When driving it. On the bench sitting there, this is not obvious to the naked eye. Tires just appear to drive on its edges when Steering is lock to lock.
Many overlook this completely, never even reading the TLRT Manual and opening the bag of Various mounting Pills.

I don't have pills on the top arm because the limitless tower only gives the one position. Playing on the bench I tried the max kickup on the lower pills for active caster and it didn't make a difference when I cycled the suspension. When I ran it off-road changes to the pills made a huge difference but I think the short wheel travel makes them less effective. Roll center is the only thing they have much of an effect on now.

 

[Overkill]

Wild idea was f1 flow-vis inspired "crashed through some cans of paint and kept going." For it being a first attempt I think I'm ok with how it turned out, for now. Also still has the film on it.