Jump to content

Recommended Posts

Hi all

Have checked hi and low to make sure no ones posted on here bout this yet as it must be something real stupid but cant see anything.

A month a go I bought a lunchbox kit. Chuffed to bits built it the same day and was up and running. The truck run great for 3-4 outings but for some reason now the gearbox doesnt turn the wheels? When I first built it, it was to the exact spec in the manual and worked, I have stripped it back and rebuilt back to the manual spec but it doesnt turn the wheels anymore?

Every single tooth is still present and the motor turns the biggest cog but it doesnt power the wheels. Its really really odd as it seems that when the diff turns one wheel its also allowed to freewheel while the other wheel runs. By hand slowly it works but wont power the axels when there is any pressure AT ALL!

Please please can anyone shed light on this as apart from buying a new gearbox now Im stumped :)

Many thanks

Share this post


Link to post
Share on other sites

Are the crosspins in the axles? Have you melted a plastic bush. For the $12 it costs for bearings, worth fitting them.

Other than that, all I can suggest is pull it down, lay the parts out, take a photo, post it here. Then reassemble following the manual carefully. There must be something you overlooked. The lunchbox gearbox is very strong with bearings fitted.

Share this post


Link to post
Share on other sites

Hi

Pulled it apart again and layed out everything for you to see. I did notice before I pulled it apart that there is play in both axels in and out of the gearbox, should there be?

Have checked all cogs and teeth under magnifying glass no sign of damage whatsoever. Cross pins are in the axels but havent even bothered with the wheels yet. If I hold the white gear through the motor opening just slightly the axels still turn. Have put it all back together with new plastic bearings (have ordered a set of steel ones tho) but still no joy.

post-30038-1242860323.jpg

Share this post


Link to post
Share on other sites

There will be a bit of side to side play in the axles, I think it lessons when you fit the metal bearings, but you can buy shims to take that play up,

Sorry cant help with your drive problem.

E2A:

If I hold the white gear through the motor opening just slightly the axels still turn

Is that both axles or just one?

Share this post


Link to post
Share on other sites

I see missing from your photograph a small steel pin that goes through the centre of the diff and into a recess in the end of each axle. This is what the diff pivots on.

With weight on the wheels and power on the motor the diff will not be engaged by the mainshaft gear without this metal pin.

Compare to the manual, Page 7, Step 8, Part BC6.

Share this post


Link to post
Share on other sites

I think TA Mark has the answer.

I note in your pic that the hex on the inner end of the right-hand axle isn't engaged in the diff gear - I'm not sure if you noticed this or overlooked it. If you assemble without the pin, the hex might not engage the gear and you will have no drive.

If you have installed the pin and it still doesn't work, then remove the motor and check that the pinion is still tightened on the shaft - sometimes the grub screws come loose and you lose all drive.

Share this post


Link to post
Share on other sites

i had a hornet that was a bit wobbly but worked without the pin (which i discovered was missing after opening it up), but i think the problem is that the diff output gear is no on the hex bit on the axle on the right?

Share this post


Link to post
Share on other sites

Thanks guys for being so helpful, the pin is definately there sorry you cant see it and nope, still doesnt work. I can spin both axels in opposite direction at the same time thats right isnt it?

Quote "If you have installed the pin and it still doesn't work, then remove the motor and check that the pinion is still tightened on the shaft - sometimes the grub screws come loose and you lose all drive."

Its funny you say this because the first time it died I took it apart and found the tiny allen grub screw in the garbox, but........ I fixed the brass gear back onto the motor spindle with a bit locksafe, held it in m fingers and tested the motor. Its definately not spinning now but the gearbox still has this problem ;)

Ive checked the hex heads on the shafts and theyre tight.

The gearbox seems to feel completely normal but as soon as you put any strain on it there is slippage, I suppose Im gonna have to buy new gears, just cant understand it, theyre meant to be tough!

Share this post


Link to post
Share on other sites

Without putting anything inside the gearcase, assemble the diff in you hands. Hold both axles solid and try to turn the centre diff gear. Will it spin? It shouldn't if you have both axles held solid.

If that works. put the gears in 1 side of the gearbox and repeat, this time trying to spin the spur gear with both axles held solid.

There is nothing wrong with any of the gears from the photo you posted. Only thing I cannot see in that photo is the BC6 shaft. And it's the only thing that will cause what you describe unless one of the gearcasings has a shaft locator torn out of it.

I've had mine running for more than a year with much use, fitted with an extremely powerful motor. So powerful infact that it will do a standing backflip. Nothing has ever broken or worn in the gearbox.

Share this post


Link to post
Share on other sites
Hi

Pulled it apart again and layed out everything for you to see. I did notice before I pulled it apart that there is play in both axels in and out of the gearbox, should there be?

Have checked all cogs and teeth under magnifying glass no sign of damage whatsoever. Cross pins are in the axels but havent even bothered with the wheels yet. If I hold the white gear through the motor opening just slightly the axels still turn. Have put it all back together with new plastic bearings (have ordered a set of steel ones tho) but still no joy.

post-30038-1242860323.jpg

this might sound silly but are the drive pins in for the wheel,

if so make sure the set screw for the motor is on the flat when you tighten it.

skip

Share this post


Link to post
Share on other sites
this might sound silly but are the drive pins in for the wheel
Hi

Cross pins are in the axels but havent even bothered with the wheels yet

Share this post


Link to post
Share on other sites
Without putting anything inside the gearcase, assemble the diff in you hands. Hold both axles solid and try to turn the centre diff gear. Will it spin? It shouldn't if you have both axles held solid.

If that works. put the gears in 1 side of the gearbox and repeat, this time trying to spin the spur gear with both axles held solid.

This is where things get a bit sketchy. The first step works great then I put it all in one side and I can (fiddly but...) get it to do the same thing with both axels solid on diff the spur gear turns great and vice versa. The main problem is when the case is screwed back together from this point on there is play in both axels probably slightly more in the left.

Now, if I turn the left axel with the bit of play loose, the right axel doesnt turn, if I put pressure on it towards the diff the right axel still doesnt turn, in either case I can also hold the spur gear stationary with my finger.

HOWEVER!!! Now without holding the left axel any more......

If I turn the right axel with the bit of play loose, the left axel doesnt turn, and I can also hold the spur gear stationary with my finger BUT if I put pressure on the right axel towards the diff the left axel now turns in the same direction AND I can't hold the spur gear stationary with my finger.

Now Im aware of it I can even feel the right gear coming of the diff if I slacken the play. Does this mean a bearing is knackered, will the steel ones Ive got coming fix it do you think?

Share this post


Link to post
Share on other sites

When you say it "slips," does it make any noise, like a clicking or popping sound? Or does it just start slipping smoothly like a car with a worn-out clutch?

Share this post


Link to post
Share on other sites

How far does that little BC7 spacer ring on the axle push inside of the plastic bush? If it's does that could be it too. That one side isn't engaging the large bevel gear and you would loose all drive.

A set of bearings will solve that. I won't run without bearings (meaning bushings instead). Bushings will wear both the bushing and the shaft they are fitted to. When you do upgrade to bearings you then find they are a loose fit on the shaft. I made this mistake with my first ever kit and then never again, always had a set ready to go as the a new kit was built.

Share this post


Link to post
Share on other sites

Hi Guys

Its been a while but I thought Id give u an update. Although all gears looked faultless they were slipping because the spacer just wasnt big enough! Somehow the gears had been wrecked in the first week of use! Since got a new gearbox and everything is running fine, also now running a 19T motor with ball bearings and she's flying!

Thanks for the help

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...