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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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