crown design

[creighton]

I was going to post this on FNL.. but I feel I should show the design here instead.. I need a gut check concerning the design and am asking you fine folks to offer thoughts if you feel so inclined.

I will share the thoughts I have later, but for now I feel that I am thinking too much about it.

The crown is designed for 25.4mm round blades .9/1.3 wall and 25.4mm threadless steerer. I plan to use a SON20 disk compatable dyno. Cut from 1" 1018 plate. This crown is for a Chicago style winter bike I am designing. If it turns out to be a faulty design then I will start over... not proud here!

Thank you for your time,

CWN

[creighton]

Bent tubes mean strait gauge CroMo.. .035" wall for front triangle. Wishbone SS, bent deda CS's.


"he ain't heavy, he's my brother"

[marten]

I think you'll have a major stress transition at the forkleg-crown junction, beginning at the rear corner. I'd make the tang a lot longer and friendlier, and use a large shaped plug inside to stiffen the tube.

[mjbabcock]

If you CNC'd the thing lets see what it takes one to fail and lets see how it fails.

That being said, I might try to radius a few of those corners to avoid stress risers.

Also...D. Kirk has done a bunch of destructive testing in a past life and would be a particularly good person to ask.

[creighton]

plates plus coping.. gonna do some final fitting (file coping) once the steerer is in. The plates are a bit sloppy right now because I did not allow for spring back.. just wanted to rail them out to see if the plates would work. gonna make some new dies to dial the press forming. Just working to get it right and minimize the stress lines as best I can.

CW

[Clockwork]

Really impressive! Do you have any pics of the machining?

Thanks, Joel

[marten]

plates plus coping.. gonna do some final fitting (file coping) once the steerer is in. The plates are a bit sloppy right now because I did not allow for spring back.. just wanted to rail them out to see if the plates would work. gonna make some new dies to dial the press forming. Just working to get it right and minimize the stress lines as best I can.

CW

That's a lot of progress in a short time!