MUni frame design, feedback request

A few months ago I posted some questions on here about the MUni frame design project that I was about to undertake, asking people what they thought were important considerations and issues involved. The response was very helpful to me. Now I have come to the end of the project, and I would be very grateful for some feedback regarding my frame, eg. what you like about it, dislike about it, what improvements you would suggest etc. I really need this information to be able to properly evaluate the project.

The pictures are here:

(Thanks Mark for hosting them.)

A major part of my design is the bearing casings, which I have redesigned to be able to accomodate a quick-release mechanism. As you can see from the pictures, there is a major problem with them at the moment, in that they have a tendency to swing outwards. This could be rectified with some sort of locking mechanism. If it was solved, do you think the casings are an improvement on main-cap type casings, particularly for XC type MUni?

I have used a sloping crown similar to the one on the 04 KH frames, and drilled-out sheet aluminium legs to reduce frame width to a minimum.

So, what do you think?

looks good to me. I’m curious if you get any knee interference. Any plans to paint it?

As far as the tendency to swing outwards what if you put a tounge and groove on the bearing holders, it looks like they slide down to release the wheel, if that is correct you should be able to machine out a groove on removable part and do the oppisite on the frame. I’m not saying I know how to actually do this to a boxed frame like that but its just an idea.

Looks like alot of work to get it together, good job


How heavy is it? I realize that it is aluminum, and that you’ve drilled it out a lot. But it still has a very heavy look to it.

It looks like a good idea, but I don’t know how it could be made to work. It looks like it would put sheer stress on the bolt, rather than tensional stress, which is much better for a bolt. It also looks kinda bulky, and that you wouldn’t be able to clamp the bearings tight enough.

Good work though!


How did you connect the seat post tube to the crown?

I didn’t see a picture.

Lots of hard work!


Thanks for the replies.

The yang:- The frame is quite narrow overall due to the aluminium sheet legs, so knee interference should not be any more of a problem than on any other square crowned frame. Certainly less than the Nimbus 2.

As for painting it, I personally quite like the plain machined finish. What do you all think to painting it? Anodising?

Checkernuts:- Some sort of tongue and groove joint would probably be a solution to the swinging problem, although it may be difficult to make it strong enough. Can anyone who knows about this sort of thing comment?

One on One:- It is a bit on the heavy side, although I havn’t actually weighed it yet. I’ll do that today. It is certainly a bit heavier than the Nimbus.

Loosejello:- The bearings can be clamped tight enough if I use shims to pack them in more. The stress on the bolt is potentially another problem, although I think it would take some heavy abuse to actually snap it.

Teachndad:- The seat tube arrangement is a result of not having the equipment or know-how to make it the normal way. I’ve welded a solid aluminium cylinder to the crown, that is the same thickness as a seat post. Then cut a seat tube off an old frame and clamped it to the cylinder with pinch bolts. This limits the amount the seat can be adjusted and adds weight, but as I say, it’s just because I was unable to weld a tube straight onto the crown.

Thanks again for the response. Does anyone else have any suggestions?

Woops, reread thread and posts, great idea, bad reading

Sorry, I just don’t see any advantage.

To being able to remove the wheel in seconds, like for flat fixing in a race? that’s an awesome advantage.

Re: MUni frame design, feedback request

Cool frame. Very burly looking! I’m sure it is much lighter than it looks, like the early Scott Bridgeman frames.

That’s a big if. If they stay where they’re supposed to, and the bolts don’t break, it’s a definite improvement (discarding cost-to-manufacture and possible weight issues). If this can’t be resolved, it doesn’t qualify as an improvement.

Unfortunately I can’t see the mechanism enough to offer any suggestions. Yes, it looks like the bolt will be the weak point after the swing is corrected.

For riders who are into Trials or pedal/crank grabs, you will want the bottom of your bearing holders to be steel, or protected by steel.

I think the winning solution in that area will be to make something like a sideways, hinged seat clamp. Make sure the quick-release lever closes toward the rear, and perhaps even folds flush with the bearing holder, requiring a tool to pry it open when needed. Nobody likes catching a stick or something in their quick release!

That’s “sheet” aluminum? A very thick sheet! It looks like plenty of material to be strong and relatively rigid, but in a brute-force kind of way, not a structural one. The frame on my Wilder is an awful lot more complicated to make, but it’s probably much stiffer, at a lower weight. A hollow box is generally stronger than a solid piece of stock. This is the lesson of Schwinn frames. Heavy hunks of steel, but very twisty.

But it looks cool. I would be concerned with the corners though. Unlike a wider frame made of tubing, yours has hard edges! If it were up to me, I’d anodize it. I like the way that looks.

It’s not that much quicker compared to four simple bolts. The only advantage is you wouldn’t have to get it properly torqued, but that’s not that much different.

Main cap bolts are extremely fiddly compared to quick releases. It’s not “that” hard to unscrew a bolt on a bicycle front wheel, but no bike costing over $100 ships without a quick-release anymore.

However, Jim Roberts’ design looks more solid than this one.