[Racing Geek]

I was wondering if anyone has seen a 2 piece sprocket on a bike. I'm talking about sprockets that split down the middle so you don't have to remove the wheel to change sprockets. Like gokart sprockets. I've got something in mind and it would be a hell of a lot more convenient to just change a sprocket instead of taking tons of shit apart. I'm mostly worried about the power capacity of a setup like this. I can split them myself super easy and accurately.

 

[shinyribs]

There's so many teeth engaged at one time that I don't imagine strength issues being an huge factor. On steel that is. Not sure about doing this on an aluminum gear.

I would think the smallness of a front sprocket might not be well suited for this, but out back, I don't see why not.

 

[sebwiers]

I think the "strength" concern would be more of a "precision and wear" concern. If the bolt up is even slightly sloppy, the 4 teeth on either side of the 'seam' in the sprocket would not have the same spacing between them as the rest, which could throw off the contact position for quite a few of the other teeth that engage after that one. Not the end of the word, but (as with running a new chain on a worn sprocket) it could wear out the chain rather fast.

I'd guess this isn't an issue for go carts partly because they run very heavy chain compared to power, and partly because they don't see much milage. Then again, maybe its just not an issue, or stops being an issue once the chain "seats" to whatever slight irregularity the bolted up ring has.

I say go for it, but keep a close eye on chain stretch.

If you just want two different ratios that are easy to switch between, maybe you could do something equivalent to a dingle cog? That is, side by side sprockets front and back, such that both combos (inner and outer) use the same chain, but different ratios? Could easily go +2/-2, maybe more. Not sure if that's really practical on a motorcycle though.

 

[piester]

the key to keeping it working well isnt so much aligning it. its the gaps where the sprocket was cut. you would most likely have to cut it in the valley where the roller rides. the problem there is the roller is going to want to push between the cuts since when you cut it you will leave a gap there since it will remove material. so you would need to remove the LEAST amount of material possible. also id imagine you would want the same amount of nuts holding each half on so a 6 bolt sprocket carrier would be needed which is nice since the srad generation rear wheel uses 6 and it comes in 5.5 and 6 inch rear. so you could at least test this theory out. i have a 5.5 and a 6 inch rear wheel but only one carrier. i would be willing to mail you a steel sprocket of mine if you want to cut it in half and i could see how it does on the 7/10 haha. zach once cut a quarter in half so it looked like 2 quarters. he used some wire thing. maybe talk to him about cutting with that

 

[sebwiers]

zach once cut a quarter in half so it looked like 2 quarters. he used some wire thing. maybe talk to him about cutting with that

Sounds like

. Its possible to do as a home setup, but very uncommon outside high precision industrial apps.

I think it would be good to do a two piece 'cover plate' for the two piece sprocket. Drill them both (clamped together) before cutting either, and align them with pins (some welded to sprocket, some to plate). The make the cuts in the sprocket and plate at 90 deg to each other. That way the kerf cut won't throw off the tooth spacing, and you have more then just the bolts that hold the (half part) of the sprocket keeping it from shifting under load.

 

[jerryatrophy]

Just machine a couple rings to bolt it back together that way you'll maintain the tooth pattern with minimal deflection.

 

[Racing Geek]

I think the "strength" concern would be more of a "precision and wear" concern. If the bolt up is even slightly sloppy, the 4 teeth on either side of the 'seam' in the sprocket would not have the same spacing between them as the rest, which could throw off the contact position for quite a few of the other teeth that engage after that one. Not the end of the word, but (as with running a new chain on a worn sprocket) it could wear out the chain rather fast.

I'd guess this isn't an issue for go carts partly because they run very heavy chain compared to power, and partly because they don't see much milage. Then again, maybe its just not an issue, or stops being an issue once the chain "seats" to whatever slight irregularity the bolted up ring has.

I say go for it, but keep a close eye on chain stretch.

If you just want two different ratios that are easy to switch between, maybe you could do something equivalent to a dingle cog? That is, side by side sprockets front and back, such that both combos (inner and outer) use the same chain, but different ratios? Could easily go +2/-2, maybe more. Not sure if that's really practical on a motorcycle though.

A dingle cog won't work for me. I want/need to keep the chain run as narrow as possible.

the key to keeping it working well isnt so much aligning it. its the gaps where the sprocket was cut. you would most likely have to cut it in the valley where the roller rides. the problem there is the roller is going to want to push between the cuts since when you cut it you will leave a gap there since it will remove material. so you would need to remove the LEAST amount of material possible. also id imagine you would want the same amount of nuts holding each half on so a 6 bolt sprocket carrier would be needed which is nice since the srad generation rear wheel uses 6 and it comes in 5.5 and 6 inch rear. so you could at least test this theory out. i have a 5.5 and a 6 inch rear wheel but only one carrier. i would be willing to mail you a steel sprocket of mine if you want to cut it in half and i could see how it does on the 7/10 haha. zach once cut a quarter in half so it looked like 2 quarters. he used some wire thing. maybe talk to him about cutting with that

I would also be using "some wire thing." We've got 2 machines at work. That's where I was thinking I would cut it. I also figured a 6 bolt sprocket would be needed. No motorcycle wheels or cush drives to deal with. LSD units and custom housings instead.

Just machine a couple rings to bolt it back together that way you'll maintain the tooth pattern with minimal deflection.

Not sure what you mean by rings. Eatabullet suggested I cut a locking shape into the sprockets instead od just straight across. Seems like a good idea.

 

[sebwiers]

I think he meant basically the same thing I was saying; something that bridges the gap between the two halves and keeps them in alignment with more precision & strength than just the 3 bolts you would have on each half-sprocket bolted to your 6 bolt hub.

I could also see building the two halves in such a way that they overlap a bit, and each are engaged on 4 bolts (fully on 2, partly on 2). Not possible if you just cut a stock sprocket down though.

 

[jerryatrophy]

Take the sprocket. Machine a ring that runs around the diameter just below the chain run on the teeth. Drill thru the sprocket and ring in 6 places. Mark it for refrence. Then split the sprocket. Then bolt the two sprocket halves to the ring and then the sprocket to the wheel. Or adjust the ring size to accommodate the multiple sprockets u plan on using. The ring will be solid and you'd have to remove the axle to get it off but you could swap sprockets to the ring either way. Does that make sense?
How big of a difference in sprockets are you intending to use?

Edit: not really sure how go kart sprockets are secured so I hope im thinking about this right.

 

[noobster]

interesting idea, but i can remove the rear wheel on both my bikes in around 10 minutes.

 

[Racing Geek]

interesting idea, but i can remove the rear wheel on both my bikes in around 10 minutes.

Good for you?

Take the sprocket. Machine a ring that runs around the diameter just below the chain run on the teeth. Drill thru the sprocket and ring in 6 places. Mark it for refrence. Then split the sprocket. Then bolt the two sprocket halves to the ring and then the sprocket to the wheel. Or adjust the ring size to accommodate the multiple sprockets u plan on using. The ring will be solid and you'd have to remove the axle to get it off but you could swap sprockets to the ring either way. Does that make sense?
How big of a difference in sprockets are you intending to use?

Edit: not really sure how go kart sprockets are secured so I hope im thinking about this right.

Not sure how that would be any different then just splitting the sprocket and bolting it straight onto the LSD housing. I can see how having a flange for the sprocket to sit on would keep it from closing the gap where it was cut but what about it spreading?

 

[jerryatrophy]

After looking into it I think I see what your talking about. The kart sprocket bolts to the diff housing pretty much close to the teeth anyway. I'd just mill a slot between the halves of the sprocket to insert a "t" type spacer that you can secure with a couple countersunk screws. Would take up the gap preventing flex of sprocket halves either opening and closing.
Are we on the same page now?

 

[Jackstand Johnny]

What about some kind of keyway or pins that keep the two sprockets locked into place with one another. Is that at all possible? Like cutting a couple square holes in the sprockets and using a small piece of keystock in wach one to keep them from coming out of alignment from one another?

 

[Racing Geek]

Yeah the best thing I could come up with is something similar to that. Ream the bolt holes to 14mm and ream a 14mm hole in the LSD housing so the dowels locate everything exactly where it has to be. Key here is that the dowels have a 10mm ID so I can still bolt through those holes to hold the sprocket on.

 

[shinyribs]

Take the sprocket. Machine a ring that runs around the diameter just below the chain run on the teeth. Drill thru the sprocket and ring in 6 places. Mark it for refrence. Then split the sprocket. Then bolt the two sprocket halves to the ring and then the sprocket to the wheel. Or adjust the ring size to accommodate the multiple sprockets u plan on using. The ring will be solid and you'd have to remove the axle to get it off but you could swap sprockets to the ring either way. Does that make sense?
How big of a difference in sprockets are you intending to use?

Edit: not really sure how go kart sprockets are secured so I hope im thinking about this right.

Not real sure that would work with two different sprockets of different O.D.'s. Otherwise, it sounds swell.

 

[a_morti]

Like this?
https://www.supersproxusa.com/

 

[Racing Geek]

No, you still need to remove the axle with those sprockets.

 

[shinyribs]

I google image'd "split ring gears" and came up with this: http://www.quick-fab.com/new_page_14.htm

What I had in mind when Jerry was talking about dowels.

 

[Racing Geek]

Oh that's neat! Although I'm not sure how I could cut the sprocket like that with the machines at work.

 

[a_morti]

Not sure it's worth the effort. Almost certainly no commercial market for it. Race teams won't have an issue removing the wheel as much as it takes and regular joes don't change sprockets that often.

You can usually change a sprocket without removing anything else on a sssa.

Might be a bit over complicated but you could have an alloy centre for lightness then a two-part gear from steel similar to a supersprox sprocket

Edit: it was tldr but I read it and realise its not for a bike sprocket. Ignore the above unless its somehow useful