TOPIC:

After assembling my re-re Bruiser transmission I noticed it seems to have a good bit of internal rotational fiction. Is the normal? It seems to shift through the gears fine when I move the shifter shaft, but it seems "rough" when rotating the output shaft(s). It appears to be very different from the original from what I see.

Saito wrote:

After assembling my re-re Bruiser transmission I noticed it seems to have a good bit of internal rotational fiction. Is the normal? It seems to shift through the gears fine when I move the shifter shaft, but it seems "rough" when rotating the output shaft(s). It appears to be very different from the original from what I see.

Just how far along in building the transmission are you?

I tried twiddling the output shafts at various points, this is what I can remember:

1 - gearbox built & fixed in 2nd gear, but motor not fitted: gearbox smooth but a little difficult to turn

2 - as above but with motor fitted - even more difficult to turn, but once the motor was turning too, not so bad. Did feel a little notchy as the motor spindle passed the magnets though, + some gear noise. I also ran the motor at this point (fixed in 2nd gear) - the gearbox was a bit noisy at first, but settled down within a few seconds. I didn't try try shifting gears at this point.

3 - completely fitted with all shafts & wheels fitted - pushing the truck along the bench met with a lot of resistance, then the motor starts turning & it's ok ... though there was a hint of clackiness.


4 - running the thing - quite a bit of gear noise especially in low & 2nd, top is a lot quieter.



I did spend a lot of time taking the main shaft apart & rebuilding it until I got the shimming "right" - there's no mention of what the correct endfloat is, so I just kept putting shims in until there was no end float, and no resistance on any of the rotating parts.

looking back at my Bruiser build thread,

I wrote:

There was a _really_ helpful note in the manual - "Use shims (BC 16 (0.5mm), BA19 (0.3mm)) for clearance adjustment"... well, duh! I know shims can be used to adjust the end float, but what is it _supposed_ to be?

I reckoned there was about 1mm extra float once the shaft was together, so put an extra 0.3mm shim between the two plastic gears & two more 0.6mm shims between the 1150 bearing in the 22T gear & the circlip on the "left" end - so now there's no extra float anywhere on the shaft & everything still turns freely ... it feels right but I have no idea if it's correct

Might be worth looking at?






A question for you though - if you've got the drivetrain fitted - how floppy is your front shaft? (oo-er missus! )

Mine feels very loose in both the front diff housing and especially in the gearbox - almost as though I'd missed a bearing out

Mine is all assembled but without the motor installed. I too kept spinning it at various times during assembly. It never felt very smooth. I kept hoping as I built it up, and began supporting the shafts from both ends, it would smooth out but it still feels very notchy. I can hardly turn the rear output by hand without the aid of pliers or something. I can spin the spur gear with my finger easily enough (though I still feel the notchiness there too). I guess I'm going to pull it appart and fiddle with the shims. Your right. Tamiya is really vauge about the clearances they're trying to achieve. As far as the front output at the gearbox goes, mine is floppy too. Its not nearly as well supported as the main rear output.

Saito wrote:

Mine is all assembled but without the motor installed. I too kept spinning it at various times during assembly. It never felt very smooth. I kept hoping as I built it up, and began supporting the shafts from both ends, it would smooth out but it still feels very notchy. I can hardly turn the rear output by hand without the aid of pliers or something. I can spin the spur gear with my finger easily enough (though I still feel the notchiness there too). I guess I'm going to pull it appart and fiddle with the shims. Your right. Tamiya is really vauge about the clearances they're trying to achieve. As far as the front output at the gearbox goes, mine is floppy too. Its not nearly as well supported as the main rear output.

That does sound a bit tight in there ... I'm not sure shimming will help with that, but maybe taking it apart will - if you spot something wrong, like a bearing not seated correctly, or something.

I'm glad to hear yours is floppy too - I thought I'd done something wrong

Thanks. I will investigate further. The terminology in my post sure sounded er, odd lol . Oh, I forgot to ask, does the Bruiser have an aluminum pinion and if so, what pitch is it? It feels like aluminum and looks like Tamiya 48 "metric" pitch but I'm not sure.

My tamiya store lists the 0.6 Metric's as Pinion replacement

I don't know anything about the re-re Bruiser gearbox except it's a planetary type... but what I DO know (Having scratch engineered a planetary gearbox for an old Hilux, plus from having numerous battery drill 'boxes to bits) is that this type of gearbox has a lot of friction due to the large reduction ratio in only a couple of stages (Lots of moving parts bearing on each other at high speed). They tend to get hot during use, everything needs to be spotlessly clean when assembling (The tiniest bit of dust/grit/flash will make them rough/notchy). It's also best to lubricate them sparingly & with only thin lubricant, as greases will make the situation worse. Theory says it should loosen & smooth up with use, but you'd be wise to have it apart to check there's not actually something wrong or some rubbish in there

Perhaps the planetary design makes it tough to turn the output shaft and easier to spin the spur end. I have the box appart for re-shimming and so far so good. Thanks for all the help.

Yes, definately - there's always less force (Torque) required when 'gearing down' than when 'gearing up', it's kinda the whole point! Planetary gears tend to have more friction involved because the gears are running on an inside diameter rather than the normal outside diameter, if that makes sense. The internal gears are also usually relatively small, run at high speed, & run on plain shafts with no low-friction bearings, which really doesn't help. Having said that, the gearing down gives you more torque, which makes frictional losses less important

Bingo. The toughness turning the outputs was indeed the effect of gear reduction in "reverse". I shimmed up the mainshaft and most of the roughness disaapeared too.