Bicycle Mechanics - Homemade offset 38 tooth rear cog
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05-26-11, 12:03 PM
Here is a 38 tooth rear cog I made out of a chainring it is offset and works as it's own spacer. I also took out the 1mm spacer between the cassette so it sets 3.56 mm closer to the spokes than normal there has been no problem with the derailer hitting the spokes. Offseting the cog allows me build dishless wheels. http://share.ovi.com/media/currentresident.bicycle/currentresident.10282
05-26-11, 12:09 PM
What do you mean by "dishless"? If you still have the rest of the cassete on the freehub then your wheel still needs to be dished pretty much exactly as normal. The only thing you gained was being able to remove one spacer worth of dishing. That's hardly enough to make the drive side and non drive side spokes equal for dishing angle.
And for those of us that worry about such things you likely don't have room any more for a spoke protector.
05-27-11, 10:21 AM
They are indeed dishless http://share.ovi.com/media/currentresident.bicycle/currentresident.10058 I started using 7 cogs with 8 cog spacing then went to 8 cogs with 9 cog spacing. I have built a dishless 9 cog with 10 cog spacing but prefer the reparable 9 cog chains.
05-27-11, 12:00 PM
I'm with BCRider on this one. You need to explain how you've achieved a dishless wheel. Did you significantly increase the spacing of your rear triangle? Shaving off a couple millimeters of the Freehub body barely changes anything. What you've done is roughly equivalent to replacing an 8/9/10 speed body with a 7 speed body.
If the wheel is truly dishless the hub flanges will be the same distance from the dropouts on both sides.
The 38T cog is cool though. What rear derailer are you running that will handle it?
Woohoo! Someone with tinkering skills.....
Oh, and what was the BCD on the chainring you modified??
What's that, 160mm OLD or something?
And dude - never heard of an OCR?
...Here we go:
araya vp20 rim dt 14 guage spokes 12 14 16 18 21 24 28 34 sram cogs with 9 cog spacing alivio hub 20000 miles 135.25 mm old
How the hell?
Oh, and this thing?
I think this is a Erickson ninth cog gizmo used on some santana tandems. I differs from a standard shimano adjuster that has a screw. If you know be sure to comment.
That's a standard Shimano adjuster, as found on the drive side of my 8spd 600 bike.
05-28-11, 09:22 AM
The derailer is a shimano megarange. http://share.ovi.com/media/currentresident.bicycle/currentresident.10073 I have been able to scavange a sealed bearing dura ace pulley and a sealed bearing XTR pulley for it. This derailer will handle a 52 tooth rear however the maximum jump is a 10 tooth gap. When you get rid of the dish it places more stress on the axle so you need to use a disk brake hub. The Shimano spline brake hubs move the bearing out 5mm and weigh the same as the regular hubs. The Shimano 6 bolt brake hubs and the threaded brake tandem hubs move the bearing out 10 mm.
You know....I ran across all your photos and tinkerings like a year ago.....atleast. Always intrigued me. I found this photo looking for ideas on quads and homemade chainrings. As well, I was searching for 38t cogs and ideas for that. Funny you should post all of this now. I'd love to pick your brain, if you're willing....????:D
05-28-11, 12:49 PM
This wheel is not dishless... but it has less dish.
This is a dishless 8 speed set up... the hub spacing is 165mm and is designed to run multiple blocks... or a drag brake if it was installed on a tandem.
05-29-11, 09:10 AM
The reason I'm building offset cogs is when I went from regular DT spokes to DT alpine spokes http://share.ovi.com/media/currentresident.bicycle/currentresident.10049 the largest cog rubbed against the spokes. Also I had to move the smallest cog closer to the dropout this makes it harder to shift to this cog and makes the chain skip under a hard pull. I did not invent this custom builder Ron Boi was welding cogs together to move them closer to the centerline in the 70's later Tom Ritchey built an offset 33 tooth cog for his 2 by 9 system and Santana used this cog and shifted over it using an Erickson 9th cog gizmo. Shimano started offseting cogs on their 10 cog systems. The best system would be to build a 2 cog spider perhaps a 30 40 pair for the rear with a built in spacer with the spacer 3.95 to 4.34 mm thick it would not damage an aluminium cassette.
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