Taper Lock Question

[Paul Fairlamb]

John,

Looking at this issue first from the 16.5mm setting of the sprocket, 0.5mm shaft movement is equivalent to 16.5mm +/- 0.25mm, nothing in terms of sprocket position for the tracks.

However in terms of bearings this is enormous and you need to ensure that the gear wheel inside the housing does not foul the housing or hull side so location is very important!
I presume you have two bearings on the drive shaft; these should locate the shaft without any noticeable lateral movement. Your 0.5mm movement must be caused by the bearings moving either on the shaft or bearing housing.

There are two solutions; the quick and simple way or the proper way.

Quick and Simple
Use Loctite bearing lock on the bearing housing and on the shaft to locate the bearings, adjusting the shaft correctly before the Loctite sets.

Proper Way
On my Comet, with similar lateral movement, I first located the position of the drive wheel within the housing using a thin shim (cut from a poly bag) to give a clearance between the drive wheel and bearing outer race & bearing housing. This was cut with a shaft diameter hole and an outer dimension equal to the bearing inner race. I then placed spacing washers between the taper bush and outer bearing inner race. The spacing washer thicknesses were chosen to give the correct hull to sprocket clearance. It is a bit of a balancing act at first as you have to guess the movement of the sprocket on the taper bush as it is tightened up. Keep a moderate pressure between the taper bush and gear wheel to eliminate lateral movement as you tighten up the taper bush.

Now, when all is assembled, the bearings are located positively on the shaft and in the housing by the taper bush and gear wheel gripping and locating the bearings.

Hope this helps.
Paul

[John Fitzsimons]

Thanks Paul,
I had not used anything to bond the bearings to the shaft hence the lateral movement. I have since found a post from mark stating that they need to be secured to the shaft with a high strength ratainer. This I now understand is bearing lock. Simplest method seems easy enough but how strong is the adhesive? I will try to source some.
I will also try to work out you alternative. I'm not an engineer so I have to get my head around it.

Thanks for the help,
John

[yves mouton]

Hello John,

I use loctite nr 648, thats for cylinders ,axles, bearings
regards Yves

[Paul Fairlamb]

John

You only need to worry about the strength of the Loctite when you try to get it apart!! Just make sure that the surfaces are clean.

Like Loctite adhesive it only goes off when air is excluded so you have plenty of applying time but not much time when all is assembled; so make sure everything is ready before you start assembling.

Happy tank building

Paul