Sprocket - TrackFrame Clearence OC-3

[Jethrow]

Can someone tell me what would cause the sprocket to hit the trackframe?  I was comming down a small hill made a left turn an heard a crunch.  After that I couldn't go forward or reverse.  The sprocket was riding up on the track rail and just touching the track frame.

I loosened the track and used a pry bar to wedge the track back under the sprocket and hobbled off to the barn.  After tightening the track to about 1 1/2" drop, the sprocket is still about 1/8" from touching the track frame.  Sprocket and pins are 80-90%.

Also the machine wants to drift left even though both tracks have the same tension.  Does adjusting the tension on the trackframe spring have anything to do with the sprocket clearence or adjusting for drift?  Any crime in cutting back the trackframe near the sprocket about 3/4" to prevent this from happening again.

Jethrow

[Robert Barbour]

I would think the sprocket mounting nuts are loose or the studs are broken, either way not good. Take the support bracket off and have a look!

[Paul Bianchi]

The inner and outer track support brackets on my 49 HG-68 were so severely worn that it wore into one of the three bolt holes that held the inner dust plate on.  From what I recall, my sprocket would also hit the track frame every once and a while.  I replaced my inner and outer track support brackets, Zimmerman's carries them.  The inner stud (trunnion) on my final drive was badly worn as well.  That had to be built up with weld and then re-ground for the track frame support to fit over it.  I think I have about 1/2" of clearance now.

[Jethrow]

Hey Paul,

You may be on to something.  When I took apart the final drives there were shims in the track hangers.  The shims were blocking a channel machined around the track hanger from the grease fitting.  Didn't make sense to me so I left them out.  They were no thicker than a beer can so I can't beleive they would make that much of a difference.  The track hangers fit tight on the trunions, bolts were replaced with Grade 8 bolts, torqued down and in good condition.  Somehow, the track frame is pivoting around the trunion for the sprocket to hit the track frame.

Looking at the side view pics of Cplwill's machine, I notice he has about the same clearance that I seeing.

Jethrow

[oliverchris]

If someone uses HG track frames on an OC3, the wheel channels need to be cut or ground out a bit to avoid rubbing.
I have an OC3 with HG tracks frames and while it worked OK without modification, but Zimmermans re-shaped them to make them better...this is perhaps more important for the front idlers than the rear sprockets, but it is something to bear in mind.