Anyone have a brand new sprocket that can be 3D scanned?

[Doosh]

Honestly, no, because the stock front sprocket is a needlessly complicated affair that's going to be expensive to manufacture compared to an ordinary front sprocket design and offer nominal advantage, even for the street rider.

Early next year I'll pull the trigger on a minimum order of 100pc of a race sprocket design that compensates for the 1190rx chain offset (vs. the 1125) and move on with those. It will be a very good solution for what you are trying to do -- keep your bikes on the road. And even after I mark them up to help pay for the carrying cost of ordering roughly 95pc more than I need, probably cost less than 1/3rd per unit what you are proposing.

The OEM piece is such a one-off design. When made in quantity, they still managed to retail for $150 a pop instead of the $20 a typical front sprocket sold for! It's going to be a real PITA to make. It's only advantage is not needing a crazy broach to cut the drive splines that's apparently unique to the 1125/1190 motor.

[yamatr3]

On the rear wheels, the WSB's had JB Power Magtan wheels. I have not seen any pics of the PVM's. Does anyone have a pic? The Magtan's look like they have a cush set up on them.

[Doosh]

On the rear wheels, the WSB's had JB Power Magtan wheels. I have not seen any pics of the PVM's. Does anyone have a pic? The Magtan's look like they have a cush set up on them.

This is correct to my knowledge. I believe the PVMs were used in AMA.

This one is in hero livery, but has the PVM:

[M1Combat]

Ahhh... so you'll be selling sprockets. It all makes sense now. I was wondering why you were railing so hard against anyone trying to find a solution to keep a cush drive... Seemed really odd to me until just now.


So if you're unwilling to help find a solution to keep the cush drive (which is what this thread is about) would you mind not trying to derail the thread so you can sell non-cush sprockets? Thank you kindly.

I assure you if we don't find a solution I'll happily buy some sprockets from you... but in the mean time I'd rather try to find a way to keep it.



Soooo....


Back on topic.


I'm thinking that the idea of milling the sprocket off and adding splines that will then accept a different sprocket might be a worth approach. The issue becomes finding a sprocket that mates to a much larger spline and finding a way to secure it. I suppose adding threads and a spline might work and then secure the replacement sprocket with a nut but I don't know how much room we have to work with on the trans side of the sprocket. Doesn't look like much but I haven't actually removed the front sprocket to take a real look at the situation yet.

Obviously having a shop mill the original sprocket, cut splines and then add threads wouldn't be cheap :)... but maybe cheaper than not having a cush. Maybe...

[M1Combat]

You say there's a cush in the clutch though??? Like an actual cush or what? Lemme go take a look...


Hmmm.... Not exactly seeing a cush drive in the clutch. At least not one that I can identify via the parts manual...


Are you just referring to the clutch allowing smooth gear shifts like clutches tend to do? Is that what you mean?

What about clutchless shifting? Wheel hop? Curb Jumping? Pot-holes?

[yamatr3]

This is correct to my knowledge. I believe the PVMs were used in AMA.

This one is in hero livery, but has the PVM:

I just e-mailed PVM to see if you could special order a wheel. It looks like the they might have a cush too. I also texted the guy that bought Larry Pegram's race bikes to see what rear wheels he has.

[Mike]

M1 -

Don't think you can cut splines on a modified, stock cush drive. No room for the cutter to run out without cutting into the hub itself, which you wouldn't want to do.
BUT...machining the center out of the stock cush drive, cutting splines into the I.D. of the now...just a cush drive "hub", finding a sprocket would be much easier to have machined, because you can make a "splined sleeve" of whatever diameter suits a good diameter for making off the shelf sprockets work. And done right, it should be plenty strong enough.

I'd buy into a design like that.
Original cush drive hub, a splined sleeve, and a modified off the shelf sprocket. The only problem "might" be the hardness of the off the shelf sprocket. There's always EDM (Electrical Discharge Machining) machining for hard materials..!

Mike

[Doosh]

Ahhh... so you'll be selling sprockets. It all makes sense now. I was wondering why you were railing so hard against anyone trying to find a solution to keep a cush drive... Seemed really odd to me until just now.

Jesus, **** no. I'm not trying to sell you sprockets. I'm trying to illustrate the problem with the front-cush design.

Here's how this plays out:

If EBR comes back or liquidates, we both buy up enough sprocket inventory to last us how long we think we will keep the bike. Let's say that's 8 fronts for me, and maybe 4 for you. I'm paying $20-$30 for the race sprocket, you are paying $150 a pop for the OEM. We are both happy. For both of us, this is the best possible outcome.

If this issue lingers on, and we are both forced to paddock the bikes, now we have a choice.

I will do this order of 100pc to make it worth while for this sprocket guy to tool up to make race-style sprockets. It's a custom broach mainly, about $1200, and all the other tooling required is completely ordinary sprocket manufacturing stuff. So, I'll cough up $2,000 - $3,000 up front for this initial run, and I will resell the sprockets I don't need to racers and said sprocket company will also sell individual pieces to anyone who calls and orders. Probably around $40 a pop to buy direct from them, given the limited runs, but still, a good solution now available for EVERYONE to keep these bikes spinning wheels. Case closed.

You will chase this cush problem. First of all, you don't need some 3D scanner or anything that complicated to reverse engineer the part. It's a sprocket with a back plate and drive spokes. It's not complicated -- it's just big and expensive. To make one, find any competent machinist, hand them one, and say "make me another". Its relatively straightforward machine work.

Keep in mind, NO ONE is tooled up to make these. Everything is going to be a one-off because it's unlike any sprocket out there.

The machinist is going to have to start with, what, half-a-foot of 4-inch round for this thing? (it's not in front of me to measure). On the cush side, you have a ton of material removal work to do, so that's going to take a couple of hours. And, on the drive side it's an ordinary sprocket -- mostly. I doubt a typical sprocket grinder can deal with the integrated backplate, so you are going to be milling the teeth, which to get any durability in the part means you are probably cutting this from 4140 and then heat treating it to service hardness. There's another couple of hours.

Now, for this sprocket, you are 3-4 hours of machine time and probably $50 of raw materials in, and you still need to source that needle bearing that goes in the center of this thing!

I'll be stunned if you can get a part off the machine for less than $400. I just had some of these sprocket retaining cups turned, and 4 of them was $350 plus materials. Making parts for bikes NEVER makes out. Never. It's always better to buy mass produce, but because of the small numbers here we can't really place a big enough order to make a cast-and-machine operation worthwhile, which would be a good solution to this part. So you are looking at a material removal approach, and because it's such an oddball part you don't really get any of the advantages of it being an ordinary "sprocket" and something an ordinary machine shop is tooled up to make easily.

That's your problem.

The other proposal that's been kicked around is an ordinary sprocket that happens to have the right hole pattern to fasten the drive spokes that fit into the cush. I'm not an ME, but I would have significant concerns regarding the shear load on those fasteners, plus you still have to find a hollow-bore sprocket you can mill out to allow the drive crank to pass through.

You could, however, start with a part and machine-to-finish. For example:

http://www.mcmaster.com/#6793k171/=10g69uv

Take this thing, machine .063 off the drive teeth (ANSI50 -> 520 chain), and then machine the bore to accept drive spokes. I still think you are going to have a shear load problem and ultimately send a piece of 4013 flying into your boot, but it's a solution that won't cost as much.

[Doosh]

I just e-mailed PVM to see if you could special order a wheel. It looks like the they might have a cush too. I also texted the guy that bought Larry Pegram's race bikes to see what rear wheels he has.

You can order a PVM with or without integrated cush. Even with a cush and in Aluminum, they are lighter than OEM wheels. I've owned one before, they are very, very, trick.

[Doosh]

You say there's a cush in the clutch though??? Like an actual cush or what? Lemme go take a look...
Hmmm.... Not exactly seeing a cush drive in the clutch. At least not one that I can identify via the parts manual...

Part number CG2501.1B6.

Behind the clutch basket is a set of main drive springs.