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Best chassis for speed runs?

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Hey guys I was thinking of getting a modern Tamiya to build for speed runs. Any ideas what chassis would be best to start with that will allow tall speed run gearing? 

 It seems around me(Toronto) Tamiyas and parts are a little scarce. Mostly all I can find is TT02 kits. But then I need to upgrade shocks, driveshaft, turnbuckles...etc. And can this chassis accommodate tall gears? 

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Well, have I got the thread for you!

If you browse the results you'll see what chassis people are using to get their results.  In general the on-road TRF, TA, and FF chassis are at the top.  Many TB, TT, and buggy chassis suffer from enclosed gearboxes which limit your gearing choices.

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Are you looking for a pure onroad car or are you into doing speed runs with buggies as well?

 

At any rate, the TT02 and TT02B can be made to run stupid fast for sure. Lots of room for both motor and battery.

A TT02 with the correct hopups, such as GPM metal diffs, along with various other parts as well as a Hobbywing EzRun Max10 120SCT and a TP Power 3635 4D on 4S and you're looking at a very fast setup, if you can keep it on the ground that is.

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I would like to point out that even though the TT02 has an enclosed gearbox, 1 it can still fit a pretty big pinion and a 64 tooth spur, and 2, you don't need to use the gearbox cover plate anyway. I don't know about the TRF onroad cars, but my TRF 503 buggy is definitely not a good speed run candidate. It's a fierce track weapon, but useless as an actual speed run machine.

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Agree with @DK308 re the TT02 variants in a straight line - esp when carefully improved 

And I’ll bid a TRF 414M against pretty much anything this side of silly money on road 

Lots are quicker around a track btw - which is actually more fun / important 😬

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The basic recipe for a speedrun car is pretty simple. You want >6degrees caster in the front suspension, >2deg toe in at the rear suspension, belted or foam tyres, and shim everything in the suspension to remove slop. Run slightly stiffer springs and heavier shock oil than you would for on road racing. Spool/locked front diff.

Tt02 (non type s) suspension is kinda clunky out of the box as it is close to 0deg everything alignment which makes it very unstable at high speed. The open gear diffs make it spin like a top once it loses control. The advantage is that it is cheap so it's not the end of the world whe  you crash it, and some of tricks from the above recipe are easy to implement. At the very least you'll want some aftermarket 3degree toe rear hubs/uprights, lock block in the front diff, flip over the upper front suspension arms to get a bunch of caster, and a 5mm ID shim set. Get a tt02 kit that comes with CVA shocks and fill them with 1000cst oil (kit oil is 400cst which is too thin). Standard chrome springs are ok for starters but you might end up wanting slightly stiffer ones. 0deg camber and 0deg front toe is fine for speed runs so there is no need to turnbuckle mod everything as long as the plastic links don't have slop. No need the upgrade the propshaft unless you get a dud and it's unbalanced. Driveshafts should probably be replaced with metal universals when you get >100kmh. With those mods, you have a car that drives pretty straight by itself. The only thing left to do is add power and gear it properly.

The Tt02 is somewhat limited on gear ratios but you will be able to get a final drive ratio around 4.7 without modifying the gear cover. You need the spur gear adapter from the high speed gear set, yeah racing adjustable motor mount and aftermarket spur/pinion gears. If you mod the cover you can get down to an FDR around 3.

Even with an FDR of 4.7 you should still get well over 100kmh with an >8000kv motor on 2s or >5000kv on 3s.

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On 8/19/2019 at 12:27 PM, nbTMM said:

The basic recipe for a speedrun car is pretty simple. You want >6degrees caster in the front suspension, >2deg toe in at the rear suspension, belted or foam tyres, and shim everything in the suspension to remove slop. Run slightly stiffer springs and heavier shock oil than you would for on road racing. Spool/locked front diff.

Tt02 (non type s) suspension is kinda clunky out of the box as it is close to 0deg everything alignment which makes it very unstable at high speed. The open gear diffs make it spin like a top once it loses control. The advantage is that it is cheap so it's not the end of the world whe  you crash it, and some of tricks from the above recipe are easy to implement. At the very least you'll want some aftermarket 3degree toe rear hubs/uprights, lock block in the front diff, flip over the upper front suspension arms to get a bunch of caster, and a 5mm ID shim set. Get a tt02 kit that comes with CVA shocks and fill them with 1000cst oil (kit oil is 400cst which is too thin). Standard chrome springs are ok for starters but you might end up wanting slightly stiffer ones. 0deg camber and 0deg front toe is fine for speed runs so there is no need to turnbuckle mod everything as long as the plastic links don't have slop. No need the upgrade the propshaft unless you get a dud and it's unbalanced. Driveshafts should probably be replaced with metal universals when you get >100kmh. With those mods, you have a car that drives pretty straight by itself. The only thing left to do is add power and gear it properly.

The Tt02 is somewhat limited on gear ratios but you will be able to get a final drive ratio around 4.7 without modifying the gear cover. You need the spur gear adapter from the high speed gear set, yeah racing adjustable motor mount and aftermarket spur/pinion gears. If you mod the cover you can get down to an FDR around 3.

Even with an FDR of 4.7 you should still get well over 100kmh with an >8000kv motor on 2s or >5000kv on 3s.

 

Wow! Thanks for all the advice guys! Especially nbTMM! Great advice for Tamiya 100mph setups.

   Well I actually did manage to scavenge up about half of this info on my own scouring Youtube and forums and I already decided on a TT02 chassis. And I already ordered a few parts like the Tamiya high speed gear and adaptor and Yeah racing adjustable motor mount. The later seems to be as hard as hens teeth to find in Canada and North America as it's sold out pretty well everywhere. So I'm waiting on some parts from RCmart.

 Some really good tricks posted about flipping the front arms to add a caster...nice.

 So I'm going to get the parts together and see where it goes. If I can create one of these little speed beasts I will be sure to add the videos to my youtube channel. Hopefully not too much carnage along the way...hahaha.

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So I picked up a TT02RR chassis kit, a Yeah Racing adjustable motor mount and a 60T spur and 35T pinion and have been busy building in any spare time I can scare up. This is my progress so far. Running a 3900KV Surpass motor and RCharlance 120amp esc.

 

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Nice. If you're fighting stability try putting the standard upper front suspension arms in, but flipped upside down, which brings the upper suspension ball joint rearwards by a fair bit. That gives you a whole lot of caster in your front suspension which will make the steering self-centre strongly. Ideally you'll want to space up the tie rod ball joints on the hubs, because caster tilts the hub backwards and lowers the tie rod ball joint - you want to raise the ball back up to the height it was previously so you don't introduce bump-steer (wheel turns when suspension compresses/droops) due to the tie rods pointing downwards at an extreme angle. I use brass standoffs (like computer motherboards mount on), but you can also just get balls with a longer thread and add spacers/washers.

TT02RRfront upper arms can't be flipped upside down without cutting some plastic away which makes them very weak and break (as I found out...). The inability to adjust camber is no big consequence for speed running, especially if only at the front as 0deg camber at the front and a little negative camber at the rear will give you handling that tends towards understeer rather than oversteer.

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20 hours ago, nbTMM said:

Nice. If you're fighting stability try putting the standard upper front suspension arms in, but flipped upside down, which brings the upper suspension ball joint rearwards by a fair bit. That gives you a whole lot of caster in your front suspension which will make the steering self-centre strongly. Ideally you'll want to space up the tie rod ball joints on the hubs, because caster tilts the hub backwards and lowers the tie rod ball joint - you want to raise the ball back up to the height it was previously so you don't introduce bump-steer (wheel turns when suspension compresses/droops) due to the tie rods pointing downwards at an extreme angle. I use brass standoffs (like computer motherboards mount on), but you can also just get balls with a longer thread and add spacers/washers.

TT02RRfront upper arms can't be flipped upside down without cutting some plastic away which makes them very weak and break (as I found out...). The inability to adjust camber is no big consequence for speed running, especially if only at the front as 0deg camber at the front and a little negative camber at the rear will give you handling that tends towards understeer rather than oversteer.

That's some great advice. Thanks brother. I was reading what you posted on flipping the front upper arms before and this clears it up for me. I'm a newb to modern RC and speed runs and Lipo's for that matter. I quit the hobby sometime around 1994 and now back for a year and a half. I'm all up to speed with Lipo's and brushless systems now and loving modern RC. I also have a Traxxas Slash that I'm building for speed runs and I have a bunch of Arrma's too. But I still love Tamiya...like my first love...hahaha. That's why I'm building this TT02. I love Tamiya's and this car was a pleasure to build...even with my young kids bouncing off the walls and my wife on my case for spending so much time building.....hahahaha.

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Almost there guys. Pretty much completed and ready for a test run. I will be trying to dial in the front end suspension later. The springs are pretty stiff...going to try them and go from there. Tires are stock but I have a set of belted and another foam set.

 I also got a 3s lipo that fits the cars battery compartment.  Going to test her out and let you guys know how it went.😀

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Well...Im a little bummed out. I took the TT02 for a blast and although it seemed fast it only did 41mph.

And boy is this car twitchy. Im using a spectrum radio with SR415 receiver that I thought had AVC but the manual keeps mentioning a different receiver when they mention AVC. And to make matters worse the manual is a little vague with regard to the AVC.

Im pretty new to modern radios with all the adjustments. I did find a setting called exponential. Apparently it makes the radio act slow for the first part of servo travel so at high speed a small movement on the radio wheel wont cause you to make it lose control with overcorrection.

Funny thing is my Boomerang at 35mph is way easier to control. I cant keep this thing straight! And I crashed it into a curb and snapped my rear axle.😣

So does anyone know if the SR415 Spectrum receiver has AVC? How can I get it to go straight?

EDIT

Ok so even after specifically asking the hobby shop for a radio with AVC they gave me this one: Spektrum DX5C with SR415 reciever (NO AVC!). And.....I'm mad. I should have known there was no AVC when I was running it but anticipation(and being impatient to see how fast it runs) got the best of me. 

But....I have an add on inline gyro which I now installed and it works and I have the exponential turned up so she should be more stable now. Now I just need to scare up an axle to replace the broken one. Well... live and learn. The hobby is about learning and luckily I didn't totally grenade my car 😂

So....round two will be coming up. I have taller gears on the way 🙄 going to put in 47/52 if I can get the pinion to fit. Now with the gyro and taller gears I should get better numbers. Hoping at least for 60mph.😢🤞  I just don't know how Stew Mac has got one of these TT02's going over 100mph....

 

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I’d say the 100mph goal you’ll need much more voltage and potentially higher power motor esc combo. Something intended for short course with a 5660 can and a 4500-6000kv motor on at least 3s if not 4s.

i don’t know what these other people used but it all comes down to voltage x rpm at the end of the day. 

Consider borrowing a setup station if you don’t have one to make sure the car is actually straight. If one corner is out by 1 degree the whole car will be a ******* to drive. 

Juls

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13 hours ago, Juls1 said:

I’d say the 100mph goal you’ll need much more voltage and potentially higher power motor esc combo. Something intended for short course with a 5660 can and a 4500-6000kv motor on at least 3s if not 4s.

i don’t know what these other people used but it all comes down to voltage x rpm at the end of the day. 

Consider borrowing a setup station if you don’t have one to make sure the car is actually straight. If one corner is out by 1 degree the whole car will be a ******* to drive. 

Juls

Agreed on the voltage x RPM but all the speed guys use low KV motors and very tall gearing. 

For my Boomerang which I managed to get to 49MPH I used a high 5900kv motor because you cant go tall on the pinion because of the gearbox. And tell me this...why is my Boomerang straight as an arrow without a gyro? It's like night and day between the Boomerang (a buggy for dirt) and my TT02 (built low for the street) I'm baffled...

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On 9/9/2019 at 12:40 PM, Juls1 said:

i don’t know what these other people used but it all comes down to voltage x rpm at the end of the day. 

Consider borrowing a setup station if you don’t have one to make sure the car is actually straight. If one corner is out by 1 degree the whole car will be a ******* to drive. 

Juls

Thats some great advice!

I suspect that your tyres are ballooning.  I would invest in some foams and you definitely don’t need AVC :lol:  

From a quick look at your electroincs I'd say thats a 70Mph car but your battery is not up to the job at hand.  You want something that can surge 300amps and sustain 200!   

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Thank you sir. I have watched some of your speed runs on youtube....very impressive. 

I do have a set of foams I will put on. I have a gyro I installed to see if it helps. Also going to try installing stock front upper arms flipped as nbTMM suggested. Will need to source another battery but this one fits in to stock location.

At any rate you guys are top notch. Much appreciation on the advice.

Do you guys think I need a Cap Pack? And where can I get one?

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