Posted: Fri May 13, 2011 11:31 am
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
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