New KF build problem
 

I have just finished building a KF but when I ran it up it didn't sound right and after investigation I have found that the shaft with the spur on it moves side to side about 1mm with the bearings also moving in the housing. It also wobbles a little which obviously makes the pinion spur mesh inconsistent. The shaft with the front pulley on it also has a similar amount of lateral movement. Am I missing something obvious here? Double checked the manual and it's assembled correctly.

I this the sound more comes from the rear end. Push the arms up to around level and see if the noise is gone. I know my car makes noise but it's gone when I life the arms to running height. I think it's just the dog bone rubbing

Sounds normal to me, there is some play.

I had similar on mine and was reassured all was well. tried different bearings, no improvement. I ended up reducing the amount of play by removing the crush spacer from the layshaft (that sits between the 2 housings) and tightening the nut with the side gear on very carefully to ensure it didn't bind. I used a couple of washers between the side gear and nut after some trial and error and this took most of the slop away and resulted in much better/uniform gear mesh.

I wasn't sure if the problem was the crush space being too large, the chassis holes weren't quite right or if it was the housings that were not tight enough. I suspect that there are tolerances on all the parts and if you are unfortunate enough that you combine parts that are on the upper end of the tolerance scale, you can get issues like this.

I've had less of a problem with the LG chassis TBH but YMMV.

HTH

Crush spacer is to long, shorten it, that is what I did.

Thanks for your thoughts gents.

When you initially apply the throttle it looks / sounds horrible as it appears that the pinion is trying to spit the spur gear out of mesh & I didn't want to strip the spur. Once it is all moving it is fine it's just the initial start up that appears to be the issue & trying to get the correct pinion/spur mesh

Are you sure the motor wires are connected correctly? Sounds like the time I had B and C connected incorrectly.

Regards,
Jim.

I had exactly the same issue when I built my KF

I contacted Tom Cockerill and he suggested putting some threadlock on the outside of the bearings before inserting them into the housing

This cured the problem instantly

Yep they are correct Jim, you can see the gears trying to spit themselves apart on start up

Thought about this but was a little worried about getting them out when they need replacing.

Think a measure up & see if the spacer needs shortening will be the way to go but blooming frustrating having to take it apart againg having only just finished putting it together.

I've done what DCM said and thread locking the other of the bearing. I used just normal tamiya blue thread lock, when I need to take the bearings out a little heat from a hair dryer just to soften the thread lock and they pop out fine.

-Jeremy.

Sorted! Took a little off the spacer and all is now good as far a lateral movement goes although still a bit more wobble than I would of expected for new but seems to work fine. Thanks for your input chaps

I had a bit of runout on the spur when first assembled too but it hasn't caused any problems in months of running so I wouldn't worry too much about that.

Wingers

Wobbly KF bearings
 

Considering the excellent general engineering quality of Schumacher's current range of cars, I too was very disappointed with the bearing 'lack of fit' in the KF transmission bulkheads.
I also suspect the other cars using similar parts exhibit the same problem and it is probably down to a simple tolerance decimal place error in the design!
If left as manufactured it makes correct gear meshing impossible and would probably result in the ultimate shedding a few spur gear teeth and a very inefficient transmission too.
My solution is as some have quoted here, thin cyano carefully applied to avoid contaminating the bearings, yes difficult to remove the bearings but not impossible should you need to, I fitted the optional ceramic bearings which should last for quite a while anyway.
Have any of you passed your observations onto the Schumacher engineering team? I am!

You don't need to use glue, Loctite make a Bearing liquid for just such circumstances!!

As for tolerances, I am sure said spacer is outsourced and some have come through oversize and I am sure you wouldn't want the cost of another member of staff attached to kits so they can sit there with a calliper checking ALL parts. Yes, it is an issue but let's not make a mountain out of a mole hill now.

makes it impossible? bold claim!, I ran my kf all last season on the kit bearings and spur and never had one problem, and its built out of the box!

Few things as this is just getting silly...

- Lateral play of 1mm has next to no affect on mesh. (Both of my cars have this as they have never had a spur gear strip or anything untoward)

- 1mm of mis-alignment will have next to no affect on efficiency. Most pinions will take up this amount easily.

:p