Found this picture when googling cush sprockets, and was thinking about trying to fab something similar for my 630. http://www.minnovationracing.co.uk/product-details.aspx?id=152
There are a few issues that you'll likely run into -The short distance between the sprocket centering tabs on the hub and the sprocket bolts will limit the size of your rubber spacers unless you build a 2-piece sprocket with the cush spacers on a second bolt pattern (see below) -If you go one-piece, you would wear out the sprocket and/or hub from the sprocket rotating on the hub. The Kush sprocket had the outer tooth ring on ball bearings. You'll need a bearing in there somewhere to carry the chain tension load to the axle without trying to flatten the cush spacers. -The high torque of our motors would likely disintegrate whatever material you use for a cush in short order. I managed to destroy the inserts in two Kush sprockets in less than 1000 miles each, and those have more cush bearing surface than you would get with bolt spacers. If you look at a real cush hub, you see that there is a ton of bearing surface that you won't squeeze into a sprocket, and the cushes still wear out eventually. I guess my point is that you could build it, and it will probably work for a little while, like the Kush sprockets, but it just won't hold up.
Similar setup from Manley, but still with a small bore. I suppose you could adapt something similar with a custom hub, but at that point you might as well lace in a RAD hub...
All valid points RDTCU, but as they say, "nothing ventured, nothing gained" so I gave it a go anyway. I started out by drilling the 8mm bolt holes in my new steel sprocket out to 16mm. You cant go any bigger without getting too close to the edge of the sprocket. Then I bought some red polyurethane suspension bushes with an 8mm bore, and turned them down to 16.5mm diameter on the lathe. Then I used a hacksaw to cut the spinning bush while still on the lathe to end up with two polyurethane cush dampers from each bush. I fitted a damper into each 16mm hole, inserted a stainless 8mm bolt with a large washer and bolted it all together. I gave the sprocket and hub a thin coat of grease around the bolt holes. The question is, how tight to do up the nuts on the back of the sprocket bolts? Too tight and the sprocket won't move on the hub, and too loose, well that doesn't bear thinking about! I used nyloc nuts so hopefully they won't undo. I'm planning to shoot some close up video of the hub as I drop the clutch to see if the sprocket moves and how much. This should give me an idea of a correct torque setting for the bolts. I've also made six 16mm x 5mm x 8mm aluminium spacers to fit in place of the polyurethane dampers if they crap themselves. These can be fitted one at a time without removing the wheel or sprocket. It'll be interesting to see how they work out.
Are the bolts fully threaded, or do they have a shank through the bushing and hub? If not, you're going to chew up the bushings (and then your hub) in short order. If they ARE fully threaded, stop right now until you can get some shank bolts. Even if it is a full shank bolt, It's going to try to twist out of the hub because of the torque from the sprocket. That's always a problem with bolts/pins in shear without the stability of a countersink and/or sufficient torque. Also, how much swing arm clearance do you have? Best case, it works for a while. Worst case, the hub gets buggered. Good luck, let us know how it goes.
What I believe you're missing- which is part of the key here- are the small inserts that sit within the inner diameter of your bushings (see pic of the one in the link you originally posted, and you'll see the metal inserts that the bolts pass through.) Those allow one to tighten the bolts (holding the sprocket to the hub) properly, and should eliminate the concern of the flex (of those sprocket bolts) from torque that will ruin the hub (i.e.- since they're tight against the metal insert structural rigidity has been provided.) So, in an ideal world, your measurements Must be very precise to minimize, as much as possible (which means to ideally cancel out) any possibility of play once properly torqued. So the inner sleeve (inside of the bushing) would be precisely the thickness of the sprocket, and your cush bushings thicker by the slightest hair, so that you press them neatly into the holes upon proper torque, behind the washers. Now, all that said (and please do not misunderstand for I applaud your interest/effort), I can't help but feel this will not work. As RTDCU has said it may, for a bit, but not for the long haul. First, the cush inserts had better be Very tough/hearty and, second, I can't help but feel as though the "leverage" on what is a very limited load surface will not work out favorably. But who knows- if you address the inner sleeve thing so you can properly torque the bolts, and thoroughly/precisely address the containment of the bushings, you may have some success.
That's a lotta cabbage, though, for a sprocket (in my world.) Sure- it could be argued that it'll pay for itself a few times over when you think of the cost of replacing the counter shaft (or related internals) that take the abuse of not having a real cush system. Hard to say though, with so many unknowns (the biggest variable being does this sprocket do all that it says it'll do and is it enough to thwart or postpone excessive wear. If my 630 was younger and of significantly less mileage (and I was weighing this option) I'd probably lean towards the 300 being better spent towards doing a true cush hub.
From ADV rider: KayDubbya said: ↑ What's your expected timing for additional sizes of sprockets? I have a 2011 Husqvarna TE630 which desperately needs this product, but your listed sprocket sizes don't match. (156/136). Click to expand...At the moment we don't offer for that generation Husky as we were unsure of the demand, it is something we could look into if there were enough interest. Looks like if there was a group buy organized it might fly!
I'm certainly down for that. I guess the challenge would be agreeing on which size (number of teeth) sprocket to settle on. FWIW I'd start with the stock sprocket size and see if there's enought interest on that basis.
