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alevand
human power expert

USA
3454 Posts

Posted - 06/23/2012 :  10:07:54  Show Profile  Visit alevand's Homepage  Reply with Quote
I am building a racing mule that has an unconventional drive and steering. It will be a streamliner. I have already poisoned myself with zinc fumes welding conduit. It will be a track bike, but could be ridden on the street, for TTs. The turning radius is big, it takes 2 1/2 lanes for a u-turn without a fairing. Wheel base is 53 inches. The rear wheel could be moved up 6 inches, but due to running clearances it would make the fairing 2 inches wider.

I made a narrow front hub from an old high flange hub, it's 2 1/4 inches wide. I tried radial spoke lacing, but this would lead to a failure down the road. I can make a cross 1 pattern with the same spoke length, this make a 30 degree tangent angle, reducing flange stress to 87% of the radial pattern. I will have to order longer butted spokes for a cross 2 pattern. This would give a 45 degree tangent.



The fairing will be shorter but wider than my previous Carps. This should improve drag and stability in cross winds. The fairing will be rather tall, though due to the upright seating posture. The upright seating posture is a compromise of seeing over the 700c front wheel, wheel base and running clearances. Seat height is 6 to 7 inches.

The steering is working and I have coasted down a small hill to 20 mph. The steering seems quite stable at this speed. At the end I was able to coast down to about 3 mph before putting my feet down (Fintstone brakes).


Mule in assembly fixture. Fixtire is 4 5inch metal studs welded into a square tube. Handlebars are welded to the fork, but are 2 inches to far forward.




DRIVE:

Sizing drive bearings:

Assume pedal force is 200 lbs, .5 inch overhang

1/4 in bolt would have 4000 psi shear.

bending stress 200*.5 = 100 inlbs

fb - Mc/I

I = pi d^4/64 = .0002

c = .125

fb = 100*.125/.0002= 65 ksi

5/16 bolt would have I=.00046, fb= 34 ksi.

Endurance level for steel is anout 70 ksi (socket head cap screw fty = 160ksi)

5/16 bolt should be OK if thread not in bearing.

I ordered 2 5/16 self lube bronze lined rod end bearings, nuts and bolts.

C:
Tony Levand

Edited by - alevand on 06/23/2012 11:33:53

warren
human power expert

USA
6444 Posts

Posted - 06/23/2012 :  11:47:09  Show Profile  Visit warren's Homepage  Reply with Quote
Hi Tony,

Looks like a space frame SWB dual 700C? I'll be interested to see how this turns out.

-Warren.
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alevand
human power expert

USA
3454 Posts

Posted - 06/23/2012 :  13:48:03  Show Profile  Visit alevand's Homepage  Reply with Quote
Yes, if I can keep my interest. It may end up a Rube Goldburg.

C:
Tony Levand
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