Innovative attempts to create rear toe-in or kick-up in RC?

[TokyoProf]

Have any of you tried to create rear toe-in for your old-school RC buggies? This might be apply to old-school Tamiya 4wd buggies or other makes.
When I was a kid, I always thought my buggy could never win because of this one missing feature...and spent time imagining how I could create rear toe-in my Vanquish, Egress, etc. I wonder if this ever bothered you or motivated you to do craft something to address it. Kick-up was another thing that I blamed my Tamiya's for being a failure on the race track lol.

[juicedcoupe]

The plastic is so soft on Tamiya cars that you should be able to heat the carriers with a hair dryer and tweak them.

Anymore, just have someone 3D print new ones at whatever angle you want.

[1300GT]

Funny how this topic came up right now.
This is the link to my SG Coyote improvement thread. Have a look at page two to see how I went about adding toe in and anti-squat to the rear and kick up on the front.
https://www.rc10talk.com/viewtopic.php?f=33&t=47182

[Saito]

Considering the cars you brought up, the Vanquish and Egress, I had similar questions in my youth. The Avante was supposed to be this highly adjustable car but in reality the effectiveness of those adjustments is questionable. Adapting Avante rear trailing arms to the Vanquish/Egress could provide a little adjustment. Shortening the longitudinal trailing arm section would only alter wheelbase as the transverse arm pivots at both ends. The transverse arm could be lengthened to give some rear toe but not by much before the rear driveshafts would lose engagement and pop out.

At the front, as you are probably aware, there is zero kickup on those cars. The alloy uprights do give 10 degrees of caster though (according to the mechanical drawing that was present on the vintage replacement part packaging). Much of what early TRF did was Jamie Booth's car involved trying to impart kickup to the frontend using custom inner mounts hung off the stock mounting locations. This is not really feasible on the re-release models since Tamiya revised the ball diffs and their outdrive cup engouement design.

The lack of kickup and ackerman angle in the front of those cars in addition to the tremendous scrub radius added up to a "nervous" handling buggy regardless. Tamiya tried to reduce this tendency by attempting to tighten up the steering with the Egress's ballraced rack and running narrower front tires up front, but the core design flaws remain. Jamie Booth's car was an attempt too remedy these flaws in competition while retaining the chassis/drivetrain. Eventually this all led to the much more conventional (and pedestrian) Top Force.

[TokyoProf]

Considering the cars you brought up, the Vanquish and Egress, I had similar questions in my youth. The Avante was supposed to be this highly adjustable car but in reality the effectiveness of those adjustments is questionable. Adapting Avante rear trailing arms to the Vanquish/Egress could provide a little adjustment. Shortening the longitudinal trailing arm section would only alter wheelbase as the transverse arm pivots at both ends. The transverse arm could be lengthened to give some rear toe but not by much before the rear driveshafts would lose engagement and pop out.

At the front, as you are probably aware, there is zero kickup on those cars. The alloy uprights do give 10 degrees of caster though (according to the mechanical drawing that was present on the vintage replacement part packaging). Much of what early TRF did was Jamie Booth's car involved trying to impart kickup to the frontend using custom inner mounts hung off the stock mounting locations. This is not really feasible on the re-release models since Tamiya revised the ball diffs and their outdrive cup engouement design.

The lack of kickup and ackerman angle in the front of those cars in addition to the tremendous scrub radius added up to a "nervous" handling buggy regardless. Tamiya tried to reduce this tendency by attempting to tighten up the steering with the Egress's ballraced rack and running narrower front tires up front, but the core design flaws remain. Jamie Booth's car was an attempt too remedy these flaws in competition while retaining the chassis/drivetrain. Eventually this all led to the much more conventional (and pedestrian) Top Force.

Hey Saito, I had to read your response a couple of times (because your mechanical vocabulary is very advanced). Thank you. I thought that if I was willing to make additional chassis holes on the rear suspension mount next to the motor and the battery stay (holes made further to the front of the chassis) that the entire triangular trailing arm could be moved forward for rear toe-in effect. The wheelbase would be slightly shorter and the driveshafts would not pop out. The rear trailing arm / triangular arm would just move forward inward and frontward on the chassis.

Your thoughts on the front being the bigger issue with regard to handling might be true. I was hoping that someone would 3D print a poor man's Jamie Booth modification to the front end. The TRF mods to the Egress made the car win the I main at the IFMAR worlds. I thought that was cool and a big achievement for Tamiya . I always wanted to know how a reengineered Egress would drive like.

[Saito]

I was thinking that too. Keeping the original plastic, fixed trailing arm arrangement of the Egress would just require additional holes drilled to add some rear toe.

It would great to see some 3D printed (metal preferably) Booth-style front arm mounts but these would cause issue when used on the re-release cars. The re-re ball diff outdrives have very shallow engagement with the diff. Instead of a shaft coming off the back of the outdrive cup and going into the diff like the originals, the re-re outdrive cups rely on two short "tangs" or drive dogs to couple it to the diff housings. Only a foam "diff sponge" inserted into the drivecup pushed on by the dogbone/driveshaft end keeps them in place. Tamiya gets away with this because the arm's inner pivot point is uniquely dead in line with the driveshaft. Once the arm's inner pivot points are altered (as the Booth mod would do) moving the driveshaft out of line with the pivot points imparts sideloads which can cause the assembly to pop out.