cyberbellum said:*
Agreed. I was thinking of drilling down low, directly into the hub
body where the lockring is. Don't know if there is much metal there,
though. The bearings are in the way. Also, I wouldn't want to do
this with a nice hub and sprocket.
The only function of the lockring is to keep the cog from unscrewing,
but the shallow threading makes that quite difficult without huge
axial forces. The screws wouldn't need to be very big because they
would be very efficient at keeping the cog from unscrewing.
Dave, have you tried red locktite? Seems extreme but then again so is
a mechanically-inspired fall from a giraffe. *
On the wheel with less-expensive components (Suzue basic, Sem sprocket,
Surly lockring), I used red loctite on both sprocket and lockring. I
got up on the giraffe and stopped the wheel in place against the porch,
and bounced on the front pedal to tighten the sprocket. Then I put on
the lockring and stood on the wrench (about 200 ft-pounds) to tighten it
(risky but I was careful). This approach seems to have worked because
we tested it and the rider has used it for months now.
On the second wheel with more expensive components (Suzue ProMax hub,
EAI sprocket, and Surly lockring) I used grease on the sprocket and red
loctite on the lockring. I used basically the same approach to tighten
things. We have slippage.
The easy conclusion to come to is "Duh - use red loctite on both and
you're all set; not only that but you don't need to use more expensive
components". However, that really doesn't address the basic design
considerations:
1. Have a strong hub where the axle will not bend under vigorous use.
The 3/8" axle is not sufficient.
2. Be able to change sprockets at will with a minimum amount of fuss.
The red loctite and risky tightening procedure are not acceptable for a
good solution.
3. Be able to service the wheel (i.e., change spokes, even rebuild the
wheel) like a normal hub. This eliminates the use of red loctite,
welding, and similar approaches.
4. Have a high-reliability, secure connection. A solution that depends
on loctite isn't a solution, it's a patch. More like using advanced
chewing gum.
5. Make use of high-quality components to ensure a smooth, non-binding
pedal action. We're ok there with the track solution; everyone that has
tried either wheel has commented on how extremely smooth it is.
So a stock Torker or similar basically handles only 4. The track hub
solution handles 5, and marginally 4, but nothing else. unisk8r's
solution handles 2, 4, and 5. The standard Sem solution handles 4 and 5
(based on one I just delivered). I am working on a solution that
handles 1, 2, 3, 4, and 5, but I'm not free to discuss it yet.
The other nice thing about unisk8r's solution is that it allows one
easily to match the top and bottom gears, since they are drawn from the
same parts pool. It is also easy to "gear down" the unicycle. The
disadvantage of that is that they are drawn from the same parts pool, so
it would be harder to "gear up" the unicycle. The wheel seen in my
photo uses the smallest possible chainwheel on top with the largest
possible track sprocket on the bottom, which achieves very close to 1:1.
From there it is easy to gear up, but not possible to gear down.
I have had requests to gear up, but none to gear down. However,
unicycling is quite dynamic these days. Exciting, isn't it?
--
U-Turn - Member of Generation XO
Weep in the dojo... laugh on the battlefield.
'29er Tire Study' (http://u-turn.unicyclist.com/29erTireStudy/)
'Strongest Coker Wheel in the World'
(http://www.unicyclist.com/gallery/albup39)
'New York Unicycle Club' (http://www.newyorkunicycle.com)
-- Dave Stockton
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