Frame A has the seat tube coming down and welded between two short pieces of tubing.
Two options here include (1) just welding the seat tube alone between the crown pieces
Or (2), placing the seat tube in a sleeve and then welding it all together. The diagram shows the sleeve as an option. I think you call this a gusset.
Frame B: The diagram shows a one piece of tubing for the crown and then welding the seat tube to the top of the crown piece. That was one option (1) for this frame design. The other option (2) is to drill into the crown tube through the top and the bottom and insert the seat tube into this hole and then weld. The diagram doesn’t show drilling through, just welding to the top.
Frame C: This is similar to the KH crown, but no longer in consideration.
The frame will be mated to a 24 x 3.0 Gazz and a Suzue Hub. I am not going to buy a profile hub to use, as my normal drops are not anticipated to be any larger than 18” to 24”. I think that
height falls into the tolerances of a suzue hub. I way 160 lbs.
You will probably have to angle in ( \ / ) the fork blades in a 3.0 tyre/Suzue hub set up, that’s what we did for my Monty wheel with a Suzue hub. I would also suggest angling the ends of of the cross tube to reduce catching on the legs. I think you can see that in my pics.
I’m certain Paul just connected the seat tube directly to the cross tube. Drilling into the cross tube will probably weaken the set-up more than strengthen it. This set up has been working swell for me.
The “B” design appears to have the most structural integrity as long as it is butt-welded onto the crown tube rather than boring the crown tube. Dustin already mentioned this.
The “C” design will tend to warp when each of the three welds is done. It will also tend to flex in use if it is not thick (read “heavy”) enough.
The “A” design seems unneccessarily complex. Material is cut away reducing strength and then more material is added to try to get it back.
Is all of the tubing oval? Having all of the wall thicknesses the same is a plus.
The “B” design could also warp at the center during welding (causing the
bearing holders to separate). Welding the ends of the horizontal piece of
the crown closed should add more rigidity to the crown.
> I need your opinions on crown designs for my Muni frame.
Design A looks like the strongest one. When hand-building your own, why go
with anything less than the strongest one? If you want lightness, get the
Wilder frame. If your point is to do it yourself, make it a sturdy one.
I think that part of a unicycle fork, aside from one-footing issues, can
best borrow from the long experience of the bike industry on fork design.
What works there should work best on a unicycle as well. If building out of
straight steel tubing, a lugged design would probably be best. If you had
the lugs. I guess those are the hard part…
Consider also planning-in your seat post. That is, find the seat post you want to use, and design your frame (seat tube diameter at least) around that. This will help eliminate at least one nasty surprise. Remember that you may be wanting to shorten that seatpost when you choose it.
As far as wall thickness, here’s an idea – find a good frame that uses the same diameter and material and use the same thickness that it does.
option “c” [similar to KH crown] is the way I have gone with my 26X3 frame design and so far it has held up very well - no obvious flex, warping or cracks [despite “learner-level” tig work]. Setting up the jig was straight-forward and pretty easy to get into the nooks and crannys…
The diference from the “kh” is that the gusset is in the “middle” of the crown - I did this to give the seat tube the full benifit of the gusset.
In my mind the gusset acts as “tension-member” and gives the whole crown area a lightness and “non-bicycle fork” look that I enjoy. If you imagine the seat-tube slamming downwards you can see how the gusset will “stretch” against the force and stop the crown’s flat plate from bending out of shape…
That’s the theory and considering i’m a little over 240lbs - it seems to be fact - so far anyway.
In my planning stages the things I kept reminding myself was:
*don’t overengineer this is not a bke fork [very different forces acting on it]
*find a simple solution that “feels right”
[I have yet to post full pictres of my new machine - i will soon]
I assume you are using round there.