Cassette cogs in Shimano IGH & spacers

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crg
Posts: 99
Joined: 11 Oct 2021, 10:33am

Re: Cassette cogs in Shimano IGH & spacers

Post by crg »

Why are splines rounded for IGH cogs and rectangular for cassette cogs?
crg
Posts: 99
Joined: 11 Oct 2021, 10:33am

Re: Cassette cogs in Shimano IGH & spacers

Post by crg »

Revisiting this topic.

Found a guy with CNC setup. He is willing to try but has no idea how to specify the splines in IGH cogs. I don't either.

Can the shape of the splines in IGH cogs be characterized or specified in geometric terms? Perhaps an equation?
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Cassette cogs in Shimano IGH & spacers

Post by rjb »

I would hazard a guess that the splines are 1/2 round so should be straightforward to write a CNC program. If not quite exact then dressing with a file should produce a good fit. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
crg
Posts: 99
Joined: 11 Oct 2021, 10:33am

Re: Cassette cogs in Shimano IGH & spacers

Post by crg »

rjb wrote: 10 Jan 2023, 2:11pm I would hazard a guess that the splines are 1/2 round so should be straightforward to write a CNC program. If not quite exact then dressing with a file should produce a good fit. :wink:
It does look like a segment of a circle. Not sure how close to a 1/2 round.
Does anyone have tools with sufficient accuracy to measure this spline? Here are the parameters of interest.

Image

Curious. What would you use to measure something like this & how?
Last edited by crg on 10 Jan 2023, 4:43pm, edited 1 time in total.
Jdsk
Posts: 24642
Joined: 5 Mar 2019, 5:42pm

Re: Cassette cogs in Shimano IGH & spacers

Post by Jdsk »

Please could someone add a photo.

Thanks

Jonathan
PT1029
Posts: 1744
Joined: 16 Apr 2012, 9:20pm

Re: Cassette cogs in Shimano IGH & spacers

Post by PT1029 »

I assume for IHG splines you mean the 3 splines for the cog. These have long been standard on Sturmey Archer and other hub gears, so using the existing standard would make sense. Shimano IHGs have been around for longer than we probably think (1950s/60s?), so they would have gone with the current (SA) design. Now Shimano are big enough to creat any standard they see fit (as we all know.....!)
Cassette splines were designed from scratch (no pre existing equivalent design existed), so they could start with a blank sheet.
Jdsk
Posts: 24642
Joined: 5 Mar 2019, 5:42pm

Re: Cassette cogs in Shimano IGH & spacers

Post by Jdsk »

This sort of thing? That's a CS-S500.

Jonathan

Image
jb
Posts: 1782
Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: Cassette cogs in Shimano IGH & spacers

Post by jb »

Try the back end of a set of drill bits over the spline until you get one that's close, Probably a common imperial size if it goes back to SA.
Then measure from the the top of the spline to the bore at the opposite side with some Vernier callipers. Then measure the bore diameter or the splined shaft it is going to fit on. That will allow you to draw it out full scale then sit the sprocket on top of it and see if its close. Even better if you've got CAD soft wear and a printer.
I don't think they are a particularly precision fit.
Cheers
J Bro
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