RC10Talk - The Net's Largest Vintage R/C Community

Jester_The_RC_Guy wrote:

Coelacanth wrote:If what the guys are suggesting is true, the problem isn't in the arms, it's in the gearbox. Even arms with zero toe-in will have toe-out when installed on a gearbox that normally adds toe-in, but is installed in reverse. You'd actually need arms that are toed-out just to get zero toe with a reversed gearbox. I can see what the guys are talking about, the rear wheels look like they have some toe-out. It'll drive either way but with zero toe or toe-out on the rear, I imagine the rear end will be rather twitchy and hard to get it to track straight.

a stock bandit has miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles and miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles of understeer. id take a twitchy bandit as about the same chance as getting hit by lighting and winning the lottery at the same time. but with the rpm arms a i said i only have about a half a degree of toe out, which would help things in all honesty. but oh my! the weight savings my bandit pre-mid motored was 4.05 lbs now it is 3.43 pounds! thats .62 lbs by itself by buying a shorty lipo and blasting chunks out of the chassis. add on an integy cf upper deck, and some misc. aluminum hardware and i can see this going into the 3.3's or 3.2's which may be heavy by normal buggy standards but this IS a bandit. the lightest bandit i have seen was jang's ultimate bandit at 2.13 pounds. but that WAS pretty much completely redone with a cf chassis, and graphite chassis, upper deck, and shock towers along with misc. other weight saving mods.

FACT: TRA 2750 (suspension arms, rear) have 3° of toe-in engineered into them (pg. 34, Toe-in, Assembly Manual /Tuning Guide, TRX-3)

FACT: RPM improves durability while retaining OEM suspension geometry:http://www.rpmrcproducts.com/shop/rear-a-arms/traxxas-bandit-rear-a-arms-black/

Do your homework. We know what we're talking about. You are wrong. I respect your time, effort, and mod skills as a fellow hobbyist but come on dude........

Mark

I edited my original post with a picture, here it is again:

so you JUST turn the gearbox around, the arm mounts stay put

trx 1-3 please refrain from telling me what i do and dont know.

Jester_The_RC_Guy wrote:trx 1-3 please refrain from telling me what i do and dont know.

I understand your frustration, but Mark is correct. You should just take it as constructive criticism because these guys know what they're talking about and are only trying to help you with your build.

I will also add that the trans cases do not have any toe built into them, but they do have 1.5 degrees of anti-squat. If you simply reverse the trans, you're gonna end up with positive toe and positive squat angles. In other words, the car is gonna handle like poop. Best solution IMO is to get the RPM trans cases. That way you can leave the arm mounts in the correct locations. Several problems solved for around $20.

Jester_The_RC_Guy wrote:

Coelacanth wrote:with zero toe or toe-out on the rear, I imagine the rear end will be rather twitchy and hard to get it to track straight.

a stock bandit has miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles and miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles of understeer. id take a twitchy bandit as about the same chance as getting hit by lighting and winning the lottery at the same time.

Weight savings are great but the more you lighten the chassis, the more you'll exacerbate the driving/handling issues, if any. You mention a degree or two of rear toe-out as being inconsequential; then why do all offroad cars have significant toe-in? The reason is to help the car to track properly in a straight line, without needing to correct the rear-end from fishtailing all over. Also, I don't think increasing rear-end twitchiness is the best way to correct understeer. You're just introducing one problem to counterbalance another problem, and I don't suppose the real-world handling will magically resolve itself that way. Better ways to resolve understeer could be to shorten the wheelbase, increase front track width and/or increase weight or downforce up front.

Now, if it's true the gearbox itself has no toe factored in, then you only have to worry about the arms and/or arm mounts. I'm not familiar with this car but physics principles are the same. Is it possible to reverse the arms and arm mounts on this car, so that you retain the same amount of rear toe-in with the gearbox reversed?

Maybe a different hub carrier with more negative toe would help?

RichieRich wrote:Maybe a different hub carrier with more negative toe would help?

I've never seen a hub carrier that would compensate for 6 degrees (from 3 positive to 3 negative). Regardless, the squat angle would still be a major issue.

i may well get the rpm trans case at some point, but i want to know what i'm working with before i do. it has been rainin 24/7 here in the sunshine state (irony much?) so i havent gotten a hope of running her yet

harry697 wrote:

Jester_The_RC_Guy wrote:trx 1-3 please refrain from telling me what i do and dont know.

I understand your frustration, but Mark is correct. You should just take it as constructive criticism because these guys know what they're talking about and are only trying to help you with your build.

I will also add that the trans cases do not have any toe built into them, but they do have 1.5 degrees of anti-squat. If you simply reverse the trans, you're gonna end up with positive toe and positive squat angles. In other words, the car is gonna handle like poop. Best solution IMO is to get the RPM trans cases. That way you can leave the arm mounts in the correct locations. Several problems solved for around $20.

i do agree and normally i would take it as just that, but i didnt quite care for how he worded it.

Coelacanth wrote:

Jester_The_RC_Guy wrote:

Coelacanth wrote:with zero toe or toe-out on the rear, I imagine the rear end will be rather twitchy and hard to get it to track straight.

a stock bandit has miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles and miiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiles of understeer. id take a twitchy bandit as about the same chance as getting hit by lighting and winning the lottery at the same time.

Weight savings are great but the more you lighten the chassis, the more you'll exacerbate the driving/handling issues, if any. You mention a degree or two of rear toe-out as being inconsequential; then why do all offroad cars have significant toe-in? The reason is to help the car to track properly in a straight line, without needing to correct the rear-end from fishtailing all over. Also, I don't think increasing rear-end twitchiness is the best way to correct understeer. You're just introducing one problem to counterbalance another problem, and I don't suppose the real-world handling will magically resolve itself that way. Better ways to resolve understeer could be to shorten the wheelbase, increase front track width and/or increase weight or downforce up front.

Now, if it's true the gearbox itself has no toe factored in, then you only have to worry about the arms and/or arm mounts. I'm not familiar with this car but physics principles are the same. Is it possible to reverse the arms and arm mounts on this car, so that you retain the same amount of rear toe-in with the gearbox reversed?

as i have sad many times now, the rpm arms decreased the toe majorly, at most it was 1 degree now vs the stock 3 degree arms. and with my 4600kv motor the diff is far to loose to allow any form of drifting/fishtailing and this entire mod was made for the purpose for putting some weight up front, and it did a bloody good job at it. so you said i need to add weight to the front, when thats the point of the mod and with the stock gearbox the arm mounts are part of the gearbox so no, you cant

harry697 wrote:

RichieRich wrote:Maybe a different hub carrier with more negative toe would help?

I've never seen a hub carrier that would compensate for 6 degrees (from 3 positive to 3 negative). Regardless, the squat angle would still be a major issue.

it does not have 3 degrees of toe any more, it has closer to one degree. but to answer richierich's question yes there are hubs that will add toe

J_T_R_G,

I would like to take this opportunity to publicly apologize for taking a dump on/in your thread. I am a detail oriented guy, and in my attempt to ensure accurate information sharing, I came across as a complete Ballchinian (one who may occasionally have metaphorical balls on their chin). Your Bandit project is pretty cool. In fact, I wouldn't mind hot-lapping it for a few packs.

Respectfully,

Mark

TRX-1-3 wrote:I would like to take this opportunity to publicly apologize for taking a dump on/in your thread. I am a detail oriented guy, and in my attempt to ensure accurate information sharing, I came across as a complete Ballchinian (one who may occasionally have metaphorical balls on their chin). Your Bandit project is pretty cool. In fact, I wouldn't mind hot-lapping it for a few packs.

Mark, I don't think you should feel the need to apologize. Like Jester, I love coming up with new ideas for existing cars and re-engineering them. If I posted a mod that you or anyone else thought might need revising, I'd hope it would be brought to my attention. I'd want to know if there was something I'd overlooked or there was a better way to execute the mods.

Mr. ED wrote: Probably a good idea to get the right again too.

woops missed a word : I meant to write: " Probably a good idea to get the right anti-squat again too."

By the way I was toying with another mid-motored traxxas not long ago and moved the shocktower right over the center of the diff. Unfortunately that stilll didn't suffice to have the shocks near vertical in front of the arms.
So now it's either back to drilling extra holes on the back of the arms or maybe other arms or extra spacers between the shocktower and shockmounts. And I really don't like the first or last idea much, so if anybody has an idea on arms that could work, please?

TRX-1-3 wrote:J_T_R_G,

I would like to take this opportunity to publicly apologize for taking a dump on/in your thread. I am a detail oriented guy, and in my attempt to ensure accurate information sharing, I came across as a complete Ballchinian (one who may occasionally have metaphorical balls on their chin). Your Bandit project is pretty cool. In fact, I wouldn't mind hot-lapping it for a few packs.

Respectfully,

Mark

i understand, and your are not the only one who has taken a dump on this topic especially on traxxas forum *cough* monkeypirate *cough* i accept lets just forgive and forget