Lunchbox transmission/ diff issues

[WillyChang 1814]

18 works with motor going direct onto gearbox. 10 is a long pinion and needs the offset plastic blob motor mount. Adjustable mount is for maybe 16-19 pinion, your motor bolts to mount then mount bolts to gearbox. Do not complicate confusion by adding adjustable mount... 

 

Have you tried flipping that diff gear (with the 3 spider bevels)?

Diff should spin smooth & unrestricted, that diff gear might be offset enough to hit the counter spurgear if installed wrong direction.

 

Don't install motor, just stick your finger inside the cavity and stop the spurgear (spur = what's driven by pinion) from moving. Then spin the axles/tyres to see how diff turns... should see full differential action there, tyres rotate opposite directions. 

 

If you've done some crazy high jump landings, you might've bent the axle shafts. If gearbox is hanging up at certain point/s in its rotation, check all shafts to see if they're straight. Check plastic casing for cracks or collapsed shaft mount points.

Assuming you've got full bearings, check that none have seized or collapsed.

Sometimes it's possible to to tighten wheel nuts too much and it jams against the gearbox case.

Other than that, hornet gearbox is as bulletproof as they get.

 

 

[Jonnythefox87 61]

The diff works fine, there’s no visible damage to the gears and when I reach in to stop the spur gear the differential works smoothly with both wheels spinning freely in opposite directions

i know this gearbox is simple and as solid as they come, which leads me to think it has to be the motor.

im so frustrated cos I just wanna drive the thing, I only installed the 5th shock a week ago and haven’t been able to try it yet. 
 

I think I’m going to take it all to an rc hobby shop to see if they can sort it out for me. Everyone on here have been so patient and helpful but I’m sure I speak for everyone when I say it will be easier for someone to actually have it in their hands to look at and play around with

[a.w.k. 665]

Have you tried the 540 with the 18t pinion ?

Edit

OK, you said you did it.....when you look on the green part of the armature, is there any damage ?

[KEV THE REV 2319]

Last thought . Have a look at the gearbox at the point where the motor inserts . Is there any damage (crushing / splits) around this area due to overtightening of motor bolts ( not saying you have overtightened , but it's a possibility) and also check the other side where the bolts insert as any distortion of the motor seating could pinch the pinion onto the counter gear

Try installing the motor into the gearbox and insert bolts so they just do up but do not apply any real pressure to the bolts , then see if the wheels can be rotated by hand both at the same time to simulate driving and see if that has made any difference

[Jonnythefox87 61]

4 hours ago, a.w.k. said:

Have you tried the 540 with the 18t pinion ?

The 540 silver can works fine with 18T , so it has to be the motor......

[a.w.k. 665]

Then i would suggest that you drive a screw carefully into the brushless motor until it stops and measure how far it goes in, then insert the screws with gearbox cover into the gearbox and measure how far they protrude.

The screws should protrude at least 2mm less than they go into the motor.

[Jonnythefox87 61]

43 minutes ago, a.w.k. said:

Then i would suggest that you drive a screw carefully into the brushless motor until it stops and measure how far it goes in, then insert the screws with gearbox cover into the gearbox and measure how far they protrude.

The screws should protrude at least 2mm less than they go into the motor.

I’ve already effectively tried shortening the mounting screws but using some washers and that didn’t work

[WillyChang 1814]

Motor screws only need to penetrate 3-5mm MAX!! into motor can.

Measure projection at the motor plate, not by screwing into motor can. You'll be bound to hit something vital, winding or magnet. 

[Jonnythefox87 61]

9 hours ago, WillyChang said:

Motor screws only need to penetrate 3-5mm MAX!! into motor can.

Measure projection at the motor plate, not by screwing into motor can. You'll be bound to hit something vital, winding or magnet. 

Tested on the gearbox like you said and the motor screws would penetrate 10mm into the motor! Would you say that’s what’s damaged it? And if so how easy is it to repair?

sorry my mistake forgot the motor cover, with the cover on it’s 5mm/6mm

[KEV THE REV 2319]

The stock LB motor and pinion bolts to the motor mount first using 6mm screws then the whole thing bolts to the long screws using the captive nuts in the motor mount , the long stock bolts won't touch the motor with cover on . You said that both motors with pinion on rotated freely out of the gearbox. In theory motors are not damaged , run power to them to check . Did you check gearbox motor mount points for split damage / Crushing ?  as I said before .

[Jonnythefox87 61]

Some new developments on this .... I had ordered the identical 13.5T motor for my blitzer beetle about a month ago as I was pleased with it in my lunchbox. Tried mounting the new motor with the 18T pinion and the same problem- pinion/spur slip and click at slow speed and when the you stop the wheels once they’re spinning. 
 

is it time to just buy some new diff and spur gear and see if that solves the issue?

there is no damaging to the gear casing, my closest rc hobby shop will charge £25 just to try and diagnose the problem 

[WillyChang 1814]

Buy a Hornet or Midnight Pumpkin or Montego Rally or anything else with same gearbox  having a second unit helps diagnosis.

But seriously theses things are bulletproof, I've run out of ideas what could've gone wrong. Used to have a boneyard boxful of these trannies because they've all outlasted the rest of the chassis they powered.

[KEV THE REV 2319]

5 hours ago, Jonnythefox87 said:

Some new developments on this .... I had ordered the identical 13.5T motor for my blitzer beetle about a month ago as I was pleased with it in my lunchbox. Tried mounting the new motor with the 18T pinion and the same problem- pinion/spur slip and click at slow speed and when the you stop the wheels once they’re spinning. 
 

is it time to just buy some new diff and spur gear and see if that solves the issue?

there is no damaging to the gear casing, my closest rc hobby shop will charge £25 just to try and diagnose the problem 

I'm also tapped out  . You can buy the parts to rebuild a new gearbox for £25 or there abouts.  The original axle shafts shouldn't be a problem to reuse either. 

Not quite tapped out yet  . If the diff rotates by hand and the motors with pinions rotate by hand ( smooth with power applied out of gearbox ? ) then it is simply a meshing issue somewhere .When you hold the rear wheels together and rotate them the whole internal gear sets should move together including the counter gear , no need to put your finger in it .  I guess there are no siezed or crushed bearings etc , shafts out of line or internal housing damage ?.

[Busdriver 6209]

If you want anothr pair of eyes to look at it let me know. I'm away from Thurday-Sunday but happy to meet up and have a look?

[KEV THE REV 2319]

3 hours ago, Busdriver said:

If you want anothr pair of eyes to look at it let me know. I'm away from Thurday-Sunday but happy to meet up and have a look?

Hands on is the way I think

[Jonnythefox87 61]

18 minutes ago, KEV THE REV said:

Hands on is the way I think

Yes I think so

@kevtherev thanks for all your help though

[KEV THE REV 2319]

Don't forget to let us know the outcome when you meet up with busdriver

[Jonnythefox87 61]

9 minutes ago, KEV THE REV said:

Don't forget to let us know the outcome when you meet up with busdriver

Oh I will.... as long as it’s nothing embarrassing 😟

[KEV THE REV 2319]

Especially if it's embarrasing !   . No - seriously , would just like to scratch the itch now - hope it works out

[Busdriver 6209]

No pressure then

[KEV THE REV 2319]

As they say , 2 heads are better than 1

[Jonnythefox87 61]

many thanks to @Busdriver for taking a look at the conundrum that is my lunchbox’s gearbox. Nothing untoward going on with the gearbox, as most of us know it’s a simple design with little that can go wrong. It would appear there’s some sort of characteristic with this motor where there’s this click for the first few turns. It will be interesting to see if the same clicking occurs in my blitzer beetle which will have the identical motor installed

[KEV THE REV 2319]

Could be that your hearing the sticky grease on the gears compress and dispurse as the teeth mesh ?

[Jonnythefox87 61]

No it’s definitely the teeth of the spur and pinion gear. I’m going to run it a few times and see what happens, if gears are getting damaged then I have a spare set ready to replace but there’s no damage or stripped gears at the moment. I’m going to solder up the new motor and put it in my blitzer, will be interesting to see if it makes the same sound in that car

[WillyChang 1814]

Are you using a SENSORLESS brushless motor?

Do you mean COGGING? It's like a misfire at slow speeds.

Its normal with sensorless.

Worse when you overgearing, so motor spends more time at low revs.

 

You can try reduce it sometimes by swapping wire positions. Sensorless doesn't care what positions the 3 wires go to, so swap each one to the next terminal.

If the motor starts going the other direction, swap 2 of the 3 wires & it'll correct.

Certain wire combinations get more cogging than others, worth trying.