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ThunderDragonCy

Project RR-03Ra - Converting a TRF201 into a rally car

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Stripped the transmission down. No oil at all in the diff! Topped it up with 3000cst, and shimmed it as it was moving in the bearings. Whilst the transmission was off i also shimmed the rear arms as thry had developed quite a lot of play since i put the XB 4 deg toe in block on. Also replaced the final plastic pillow balls on the inner arm pivots with fresh steel ones spare from my TA06 build. Everything nice and tight! 

One thing i forgot to mention was that the kyosho diff has way less plunge on the outdrives than the tamiya one. My 42mm driveshafts were too long. I remember having the same issue on my DN01 now too. I had some old 39mm shafts from a ta01 that fitted so i got some nice steel ones to run with. They need quite careful packing as one popped out when i was dropping off a kerb. Ended up with an old shock o ring in each axle and a pink urethane diff packer cut in half in each of the diff outdrives. That hold them perfectly. 

Played a bit with the slipper clutch and all told it was super nice to drive. I added a medium preload clip to the front to lift it a couple of mm, and other than that this feels really good. The slipper really helps get off tight turns as it softens the motor punch as you come on throttle. Makes it really easy to drive and easy to do power oversteer! 

Now i am think i need to treat this to a brushless motor. 

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Did some powertrain chess this morning as i realised that with selling a few cars recently, a pretty much new 13.5 speed passion brushless system had ended up in my Comical Hornet! Did a quick swap. 

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Still running a tble02s, and there isn't much difference between this motor and the 27t racing motor i took out in terms of speed. The power delivery is smoother though, and being able to fine tune the braking is really useful with RWD.

Gave the handling a nice tweak too. It was rolling a lot at the rear and still spinning the inside rear a little on power out of tight turns. I had lowered the rear roll centre a lot running my previous setup searching for grip, so i decided to raise it again hoping to reduce roll and get the car to square up a little better. Pulled the spacers out from under the inner pivot balls and found them difference sizes. Doh! That's not going to help. 2.5mm left, 2.0 right. Took them both out and evened up the camber. Does exactly what i hoped, which is nice! Definitely an improvement in the handling and traction. And the same left or right now! 

I have ordered a smaller spur gear to make the most of the motor. Currently running 77/28 for a 7.15 final drive. I was running 72/27 on the same motor in my TRF201 with no trouble so there is plenty of headroom on gearing given the smaller touring car wheels. Gone for a 69t spur to give me 6.41 FDR. After that i think i start running out of space for bigger pinions under the spur cover. I did try my 34t pinion off my TA06 but it doesn't fit with the 77t spur. There isn't enough length of the motor slots to get it on there. Apparently the Associated B4/SC10 spur cover fits and allows bigger pinions so that's a last option if i feel i need taller gearing. 

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Got my 69t spur gear for the RR-03Ra to up the gearing, but found the 28t pinion won't reach even with the motor fully forward. Swiped the 34t off my TA06 and it goes on, so i'll use that to test a taller gear. It gives a pretty tall 5.28 FDR. In my hand waving earlier in the thread i thought 5.5 might be about right so this might be a bit tall. I run 4.4 in my 17.5 touring car so we will see. I do mainly run this on rough tarmac now so tall gearing would be ok up to a point. 

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14 minutes ago, Juls1 said:

How many sets of rear tires have you chewed up so far? 

1 since i built it. These ones are pretty done but still grip. The car has a lot of traction now i have sorted the shocks and diff, and i have the slipper clutch to soften the punch of the motor. Its really nice. 

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Are you using the Tamiya compound tires or China spec? The Tamiyas I found are very hard but fast wearing compound. Seem to be perfect for rubber tire drifting. 

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Ran the car for 20 mins today with the 34t pinion. It is really quite quick! Probably a bit too quick for my relatively narrow streets that i run on mostly. That said, both motor and ESC were barely warm and the battery was only down to 7.9V after a solid 20 minutes. 

However, the top speed really was a bit high and with only rear wheel braking, even being careful it's hard to keep it properly under control. I am going to get a smaller 31t pinion to give me a 5.8 gear which will hopefully get it nice. 

The higher speeds also highlighted a slightly bouncy, under damped rear end, so i will increase the oil weight from 400 to 600 and see how that goes too. 

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8 minutes ago, Juls1 said:

Are you using the Tamiya compound tires or China spec? The Tamiyas I found are very hard but fast wearing compound. Seem to be perfect for rubber tire drifting. 

Chinese on Tamiya wheels. It's horribly wasteful as they only seem to come on wheels which i don't need and nobody wanta to even cover my postage for, but now i have the handling sorted i am being kinder on the tyres. 

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I know it’s annoying most those cheapie tires come with wheels. Usually the wheels are crap anyway, and the wrong offset. 

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5 hours ago, Juls1 said:

I know it’s annoying most those cheapie tires come with wheels. Usually the wheels are crap anyway, and the wrong offset. 

Exactly. The latest set looked kinda cool, a bit like Rays GT-R wheels. They have some massive offset! Made the trqck about 10mm wider. They didn't even fit under the shell! 

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Final couple of bits and i think i am calling this done. Since i built it i have been holding the battery plate down with two screws and some spare damper discs. Today i got some TA05 battery screws so i can use body clips instead. This is the internal layout. Not the neatest, but everything is snug under the chopped Sand Viper shell chassis cover

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I also got the 31t pinion today. It definitely takes the edge off the top speed, but it does make the car easy to handle. After running a whole pack on the 34t last night i think i got used to the speed, so i might revisit this. Although one thing stopping me is that the TRF201 spur cover doesn't fit over a 34t pinion. I was pleasantly surprised today to find the 31t does, and i prefer the gears covered. 

I'll get some running video when i can grab a gopro from work. It really does move nicely. 

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This has been a bit of a poor relation the last couple of months as i have played with my other/new on road cars. I ran it on the indoor astro at tamiya junkies the other week and it was fun, but it was a bit tricky to dtive in places. I put stiffer front springs on as the super soft TRF201 brown springs seemed to make it hook a little, and it was running quite low. It's also a bit bouncy at the rear. I got it out this morning and checked the ride heights and the front was low, about 10mm. No wonder the bodyshell was scraping the floor on hard turns! The rear as running around 16mm which is what i was originally aiming for. 

To stiffen it up a little and even it out i put TRF501 yellow fronts on and moved the shock end inboard to the centre hole on the arms to lift up the front end. I fitted the DF03 gold front springs at the rear, which are about 20% stiffer than the TRF501 yellows they replaced. This kept the 15-16mm rear ride height with no preload. The front ended up at 14mm with about 5-6mm droop both ends. 

Gave a spin in the street and it felt more planted, and i had to drop the bodyshell down at the front 1 hole to get the stance right again. 

The steering is still very quick off centre and but the steering arms were very swept back. This does something to the qckermqn but i am not sure what! All my other on road cars have straight arms rather than swept back. I also noticed the outer rear wheel seemed to almost have positive camber under cornering and when i checked there is almost no camber gain. All things i am learning from my other on road cars. 

So, i moved the camber link ball to the inboard position on the uprights and shortened the links for more camber gain. Here is the shorter link and the gold spring

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I also moved the steering balls on the knuckles to the inboard position to flatten the arms somewhat. 

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I have a further option of the rearward mount on the steering wiper, but that requires some disassembly. 

Running it again there is a definite improvement. The steering it more calm and linear off centre and the rear end is a little more planted on acceleration. 

Final little thing was a couple of weeks ago. A lexan spur cover for an associated B4. The tamiya cover went on the parts bin 201 i built to sell.

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This is a little bigger than the tamiya part, but fits well enough and has room for a way bigger pinion should you so wish. Looks cool too! 

 

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The Kyosho oil diff leaked all its oil out again, and i know there is a small demand for a gear diff transmission for the TRF201X, so i did some measuring and CAD the other week and did a transmission for the wider TA06 gear diff, as used in the mid motor TRFs. I did a trial fit today

Tamiya TRF201X TA06 Gear Diff Transmission by CTE RC on Shapeways

All fits nicely, spins freely, so that's good. First time i have used PA12 since the price came down to just above versatile plastic. I think i will use this for transmissions from now on. It's harder and the bearing bore and hole tolerances seem much better. 

Unfortunately the chassis fit up was less successful. The wider diff case doesn't fit past the lugs at the front of part J2. I tried removing a bit of material with a stanley knife, and it helped, but i think it needs pulling off the car and dremmel, and i can't ne bothered with that today! If i can get it fitted i will run it then offer it for sale on shapeways. 

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So trial fit didn't go so well! Definitely won't go in. Not quite sure what I've done wrong because the profile is the same as the original. I've checked on printouts and back to back. I hacked the chassis back with a dremmel in a couple of places and still didn't go. I can only think that in a couple of critical places it's just a little bit too wide/big. The TA06 is considerably wider than the original ball diff, after all. I've done a revised designed with as much material taken out as I dare, checked it again on printouts, and ordered. Hopefully this one will go in. Really want to get this working so people runnig Zahhaks and TRF201s can have this decent gear diff option. The ball diffs are a pain in the *******, and the Kyosho diff I fitted to mine by dremelling out the gearcase is very leaky.

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45 minutes ago, ThunderDragonCy said:

So trial fit didn't go so well! Definitely won't go in. Not quite sure what I've done wrong because the profile is the same as the original. I've checked on printouts and back to back. I hacked the chassis back with a dremmel in a couple of places and still didn't go. I can only think that in a couple of critical places it's just a little bit too wide/big. The TA06 is considerably wider than the original ball diff, after all. I've done a revised designed with as much material taken out as I dare, checked it again on printouts, and ordered. Hopefully this one will go in. Really want to get this working so people runnig Zahhaks and TRF201s can have this decent gear diff option. The ball diffs are a pain in the *******, and the Kyosho diff I fitted to mine by dremelling out the gearcase is very leaky.

I’ve just started running my zahhak but don’t have much confidence in the ball diff (or my ability to set and maintain it) so much that I’ve got an entire 201 set up for when it goes...

I found your DN-01 thread to be excellent and really helpful when choosing hop ups and building so interested in how the gear diff mods develop

Greg

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Holy thread resurrection batman! I finally found the part I needed to get this running again. 

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I robbed the blue BB34 part to complete a bitsa trf201 I sold about 3 years ago. Haven't been able to use this since. Resolved to get one made and first person I asked had a spare to sell me. Result! 

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Now all I have to do is find the bumper and RS200 shell that are somewhere and I can run this again. 

 

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Aaaaaand running! 

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Still runs pretty nice. Forgot the rear shocks were a bit too bouncy, but otherwise good. Just running a TNLE02S and torque tuned motor. Might swap in a spare 1060 as I can't find my lipo alarms. 

Popped some 2 hole (from 2 hole) pistons in the rear shovks and 400cst oil. See if that's any better. 

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Ran this at the track today and it was just lovely! Proper meditative, metronmic laps this morning. So nice! Missed this little thing. ESC fritzed out this afternoon, but i have a spare 1060 that will get thrown in. Glad to have this back.

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