Cassette cogs in Shimano IGH & spacers

[crg]

Feel free to correct if needed.

Hubs: Nexus SG-8R36 & Alfine SG-S501

IGH cogs (Shimano, Sturmey Archer) are 3mm thick at the base.
These cogs are held in place by the snap ring.

To get desired ratio, plan on using 8-and 9-speed cassette cogs after grinding away 6 splines and shaping the remaining 3.

8-speed cogs are 1.85mm thick.
9-speed cogs are 1.78mm thick.

How thick should spacers be for the snap ring to hold the cog in place?
Obviously, it is 1.15mm and 1.22mm but spacers of that thickness are unavailable.

Do the spacers need splines?
What did you use?
What do you recommend?

[Jupestar]

I'm not sure i would do this, i think the adjusted splines would not be strong enough, mashing the cog splines, hopefully before damaging the IGH. I've mashed a IGH sprocket onto a hub before and it not easy to get it off.

Have you checked the ID of the cassette cog and the IGH cog match?

In terms of spacers ~ 0.5mm your into tolerances, and just test and see what would work, worst maybe you need to grind down.

I'd try and have splines on the spacers as once clamped with the lock ring should help discourage damage to the spines, but doubt it will help that much as unlike a cassette its not going to have the torgue to spread the load.

Out of interest what cog are you trying to use? there is range of IGH sizes available, and once you go outside these sizes, you can start to have problems with the chain interferring with the cassette joint. the wider 3mm cogs will hold the chain better. Although using a RD style tensioner can help both these.

[alexnharvey]

Why are you doing this? Do you need a tooth count that is not easily obtained?

[crg]

3-speed chainring up front.
I will not be pedaling out of the saddle or mashing, just spinning.

Shooting for a ratio of 1.3 wrt smallest chainring. Live in a hilly area.
Have IGH cogs of the following sizes: 16, 18, 19, 20, 21, 22.
Hubs are out of warranty.
Will need a few cogs between 17 and 30 depending on size of small chainring.
17, 23, 26 & 30

[alexnharvey]

Shimano recommend a ratio around 1.8. 32/22 gives 1.4, not far off your aim of 1.3? Also, why would you need a few cassette cogs, you know there are gears inside it too?

You've already got a good range of proper IGH cogs, so wouldn't it be easier to just buy a slightly smaller chainring, e.g. 28 or 30T? Looks to be about £10-12 on ebay for a 28T?

http://www.gear-calculator.com/?GR=SHA8 ... H&DV=teeth

I think you'll find grinding the splines could be quite difficult. They're both hard and hard to get tools at. I wanted to grind them all off so I could use the cog on a disc mount for fixed gear. I've since quit on this idea and buy lightly used velosolo disc cogs from ebay instead, an example of the rule "don't make what you can buy".

Some past discussion that you may have already seen here viewtopic.php?p=1520789

[crg]

Hard to disagree with what you say.
I know Shimano recommends around 1.8 or 1.9.
My hubs are out of warranty, though unused.

Mashing or out of the saddle at 1.9 probably loads the IGH more than spinning at 1.3

Have a knee issue.

38t chainring needs 30t cog for 1.3

If CNC files are available, can probably machine cogs with 3mm base.

Any entrepreneurs in the forum?

[alexnharvey]

I expect bike punx, a company who cnc chainrings and cogs could make you one easily enough. However, since they already make custom chainrings I remain bewildered as to why you wouldn't simply buy one of them instead? Are you stuck with the 38t?

https://www.ebay.co.uk/itm/234604082763?

or

https://www.ebay.co.uk/itm/353743467061

[crg]

Stuck with 38T chainrings since I bought a bunch of them, in a couple of BCDs. Too expensive to change now.

Btw, can the teeth of 1/8" cogs be ground to fit 3/32” chains?
24T 1/8" cogs are available.

[alexnharvey]

Easier to just run a 1/8 chain in this situation, unless you have a mill or a lathe to skim the cog. 1/8 chain will run happily on a 3/32 chainring.

[crg]

Stuck with 38T chainrings since I bought a bunch of them, in a couple of BCDs. Too expensive to change now.

Btw, can the teeth of 1/8" cogs be ground to fit 3/32” chains?
24T 1/8" cogs are available.

Standardized on 38t chainrings and 22t cogs since they are the smallest chainring and the largest cog that fit the Hebie chainglider.

Also stocked 3/32" chains but easier to remedy.

Out of curiosity, is it a simple grinding of the teeth by 1/64" on either side or does it taper from the base of the teeth to the tip?

[alexnharvey]

Most cogs have slight chamfer or bevel on the thickness near the tip to ensure the chain meshes. Shouldn't matter too much if the chainline is fairly straight but it helps us there is some misalignment.

[rjb]

I've done this on a Sturmey 3 speed hub. Fitted a cassette sprocket, It's easy to grind off 6 of the splines and shape the remaining 3. I used a crescent shaped file. No damage to the driver when I came to remove it. The spring snap ring doesn't need an exact dimension, there's some tolerance to ensure the sprocket is retained. Cassette sprocket spacers are the same size diameter as the driver.
There's more information on Sheldon Brown's website.

[crg]

Easier to just run a 1/8 chain in this situation, unless you have a mill or a lathe to skim the cog. 1/8 chain will run happily on a 3/32 chainring.

Will a 1/8" chain fit in a front derailleur and shift on a 3-ring crankset?

[rjb]

Sheldon's link here. https://www.sheldonbrown.com/internal-gears.html#hybrid

[crg]

Sheldon's link here. https://www.sheldonbrown.com/internal-gears.html#hybrid

Quite useful. Thanks.