Replaced tension block with idler sprocket on 44" snowthrower

[cheesegrader 433]

I've had a bunch of problems with the chain setup on my 79361 two-stage snowthrower.

The original tension block finally split last year.  Threw the chain.  Part no longer available.

I made some replacement blocks out of UHMW polyethylene.  That worked fine under low loads,

but in deep or heavy snow, the load was enough to cause the chain to dig through the block at about an inch per hour of use.

I had to retension the chain for every use.  Too soft for the amount of snow that I deal with.

I thought about using corian countertop scraps, but never was a fan of dragging the chain across some hunk of scrap as a means of tension.

I think this shoud have been designed with an idler sprocket.  Roller chain is meant to take load on the ROLLERS, not on the side walls!

So I finally did the deed, and I learned a few things.

 

The sprocket is a 17tooth, #40 with a sealed bearing with a 1/2" hole.  2.98 inches diameter.  This is important!

I didn't know if this would work, and wanted to be able to convert back if necessary.  

There isn't enough room to get a 1/2" hole on the tensioner bracket between the two that already exist, so I drilled out the top hole to 1/2"

This turned out to be lucky.  The lower hole would never have allowed the sprocket to fit, and would have required lengthening the chain.

A 2 1/2" Grade 8 bolt, 1/2" diameter just fits, requiring one grade 8 nut between the sprocket bearing and the bracket to line up with the rest of the sprockets.

 

The drive sprocket is in the foregroud, the idler (new and shiny silver, slightly thicker) is underneath,

and the impeller sprocket iis to the left.  There is only 1/4" clearance between the teeth!

I considered a longer chain, but clearance with the right side wall is even less!

 

 

 

 

Best as I can see, there is less than 3 1/2 " of room for the idler, making the 2.98" 17 tooth choice a tight one.

Maybe this is why Wheel Horse went another way.  

So far, this has solved the problem, and I don't think it will wear out.

I'm a little worried about changing to a new, tighter chain one day.

I would go with a smaller 15 tooth sprocket if I did it over again, but the 17 tooth is the smallest I could get at FleetFarm

 

[Red-Bovine 289]

Great idea. I haven't looked at that block in a while on our 44" blower. This post reminds me I should. Our blower is 20 years old now and may need some extra attention. Thanks for sharing.

 

Red