Tamiya M03 Mini Rebuild
Over the past few weeks, the performance of the mini has been somewhat poor. I felt a rebuild was in order…
I thought about what had changed: lipos, motor, UJs, servo, bits and bobs.
The motor was good, great even last time I used it, so I wasn’t convinced it was that (despite the smoke last night – just comm-drop overexuberance…), the UJs concerned me a little – they were different to my previous ones.
I took the front end suspension off, and there was some binding on the front shafts, the bearings seemed fine, but I think they were a little over-shimmed, a little too tight, so I took all the shims out, now nice and loose.
The gearbox came apart, nothing too untoward. The bearings got cleaned, the gears were in good condition, so they got cleaned too.
The ball diff was a bit notchy, so that was stripped and cleaned. I love the thrust race in the optional ball diff, it’s huge, way bigger than any I’ve seen in a touring car, or even in a 1/10th off roader…
I rebuilt it, and it was nice and smooth once more.
The critical point came when it came to putting it back together, I put the two gearbox halves together and spun the box, and it span really nice. I put some screws in, span it again, and oh, no, it wasn’t as free… Clearly the clamping forces of the screws was causing some binding.
I backed off some screws, and it helped a little but not a lot. I took out everything again, and cleaned out all the bearing seats to make sure everything had maximum ‘room’, and, I cleaned out the hex on the ball diff cover, to make sure the diff was as ‘narrow’ as possible. I also tried the diff in the opposite way around.
Put the gearbox halves back together, and even without screws it felt better, screws went in, and I only had to back them off maybe half a turn or so to get the gearbox running as free as without any screws in it.
What you’ve got to remember here is that a second per lap on the track is gained in tenths of a second, that gummy gearbox might have been worth 2 or 3 tenths…
I put the front suspension back on, and found a couple of binding arms, so freed them off with a drill bit here and there. Nice free suspension arms again.
I put the driveshafts back into the diff output cups and secured everything, and it span okay, but not brilliant, then I tried spinning it at full suspension compression, and bingo, the problem became clear. It was very tight indeed, hardly spinning at all.
The driveshafts were pressing on the rubber o-rings inside the diff output cups, causing binding as the suspension was compressed. I took them out, and the difference was HUGE. The gearbox now spins and spins at any point on the suspension travel.
My suspicions about the UJs possibly causing issue were confirmed. They are obvisouly slightly different in size or tolerance than the non-rebuildable ones I was using previously. O-rings in the drive cups (as per the instruction manual build) were too much, not giving them enough room.
I’m now very pleased, I feel the transmission is the best I can get it, it’s certainly never been as free running before.
It’s important to note here, that none of that tuning was done by spending money, it was just by careful attention to detail, making sure everything was clean, and checking for good operation every step of the way.
Next up, I’ve coca-cola dunked my motors for 2 minutes at 3v. I’m going to put the same motor back in, just to confirm that it was the gearbox build, rather than the motor.
I look forward to the next opportunity to compare the mini against some others…
B-Final Benny…
Same result last night at DMCRC as last week, 1st in the M03 Mini B. How very annoying! I’m quicker than that! Really! I am!
The speed of my car was visibly off, my Midnight Fettling clearly didn’t work, or maybe I chose the wrong motor. I think I need to try another motor, again.
Or, perhaps my speedo is lacking pace, I’m using an old MTroniks Viper RV11, not particularly well known for their race pedigree…
I also found my front hubs were badly shimmed after fitting the new UJs, which seem to be a bit tighter than the other set I had in. But I’m also suspecting that my ball diff needs a rebuild, and maybe some bearings in the gearbox might be a bit tired…
I think a strip down and poke about is due.
Radio Control Car Price Rises
I learned from my local hobby store (Reality Racing) yesterday, about the latest increases in UK prices for Radio Control Cars…
For example, the HPI E-Savage RRP is now £324.99! That’s a huge increase from £249.99. And a massive amount more than I paid when it was in his sale just after Christmas!
The weakness of Sterling is really hitting the hobby in the UK at the moment, so much is more expensive, as pretty much everything we use is made outside of these shores. It’s impacting how people are racing too, often choosing slower classes to save ongoing maintenance and tyre costs. I personally am planning only a limited number of touring car race meetings through the year, probably a local club championship, and a regional champtionship.
The majority of my week in week out racing will continue to be with the Tamiya Mini, which is cheap and cheerful. And of course I’ll continue bashing with my E-Savage, which is great, as I can get my RC fix without having to wait for a race day.
HPI E-Savage Shock Rebuild
I rebuilt my shocks, mainly because the stock shock seals don’t work, and also I wanted to shorten them a little to reduce the suspension travel and lower the truck to improve handling.
8 shocks took quite a while, but they’re done now. Not pefect, there’s some air in them, but they’re fine for bashing with. I have a pet hate of building shocks and waiting for the air to come out of them, I keep meaning to get a shock pump!
Video (long) showing how I rebuilt them:
Alloy Servo Horn
Following on from my post about breaking my E-Savage steering, I’ve got hold of an Integy Alloy Servo Horn.
It’s pretty big, bit the main thing about it is that it’s split, and clamps on tightly to the servo output with two screws. No more stripped horns…
E-Savage Bashing
For the first time since I got it, I came back from a bit of bashing without anything broken, it was all working just as perfectly as when I took it out.
So all the hard work rebuilding shocks, fixing steering, fitting new bumpers, rewiring it, upgrading to 14cells was all worthwhile, it was a blast.
Nothing to do on it (except perhaps a UBEC replacement…) apart from use it until I want to upgrade to brushless. Oh, I do need to look at the mounting for the two extra cells, but apart from that.
Smokin’
I wrote a post earlier about the virtues of UBECs.
But, I shalln’t publish it as I’ve just fried mine the 2nd time I turned it on…
It worked on 12 cells, but poof, smoke, smell, broken on 14 cells…
It’s supposed to handle 15 cells, I’ve asked for a refund from the HK ebayer…
Sandbagger…
I embarrassingly won the mini B final last night at DMCRC. I was off the pace in qualifying, and I’m blaming LiPo, I’m sure in a Tamiya M03 they are slower than a decent set of NiMhs.
And I’ve got decent NiMh stick packs anyway, so sorry, it’s been nice, but LiPo in mini aint for me, I need to be in the A dammit!
An in-car video of the B final filmed with a camstick.
HPI E-Savage Waterproofing
Following a very wet bashing day the other day, and cleaning it off with the garden hose I thought I should waterproof it a bit.
Posted a video showing what I did.
Schoolboy Error…
If you’re gonna mess about with motors at midnight, remember to test them afterwards…
I put my car down on the line for my first heat tonight, and it went backwards…
Turns out I’d soldered the wires on backwards. And they were too short to just swap the connectors over… Had to borrow a soldering iron and redo it…
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