Bent KH Frame

[SkierAlex]

I've got a 20" KH frame. I've been using it with a double bolt clamp, a shim (27.2-25.4) and a qu-ax reinforced seatpost (yes I got the diet kit from municycle.com :P).

Anyway when I got the frame the slit at the top of the frame (so it can tighten around the seatpost) was only about 1mm wide. I widened it with a hacksaw so the seatpost would actually stay in place. I have to do the clamp up pretty tight to stop the seatpost from twisting. I think the shim means it twists easier. I only tightened it enough so that it would hold firmly around the seatpost and the shim but it's bent the tubing on the frame inwards to the front and to one side. When I look down my seatpost down the frame it's very noticable that the frame makes the seatpost a different angle to what it should both forwards and to the side. I've got a straight edge and put it up against the frame and it's easy to tell that it's bent where the seatpost clamp attaches. So far this frame has been a pain in the arse. The KH frame's light, but I kinda wish I just kepy my nimbus frame now have to fiddle round with the camera.

So what should I do? I know I probably can't bend it back. It's not like it's a major issue having it slightly bent but I don't really want a bent KH frame forever. I'm not going to bend a steel seatpost in the opposite direction because steel seatposts are so damn heavy it'd be lighter to use an alloy seatpost and a nimbus frame.

BTW I can upload pictures if anyone wants to see how it's bent or whatever but I'd rather not.

Thanks

[jamessd]

Pictures would be interesting. How is the bent seatclamp area going to affect your riding at all?

[SkierAlex]

Originally Posted by jamessd

Pictures would be interesting. How is the bent seatclamp area going to affect your riding at all?

It won't affect it much. It probably won't affect it at all. But I'm a perfectionist. Everything has on my uni has got to be perfect :P. I have all the bolts done up the exact same tightness, the seat exactly straight, etc etc.

Basically it justs means that when I ride, the unicycle is slightly lop sided. The seat isn't directly above everything else. It probably doesn't matter but it still annoys me lol.

[Brian O.]

why not add a slice of a soda can or something to the shim so its wider and the frame doesnt have to bend in to grasp the post?

[mornish]

the problem wasn't that the slit wasn't wide enough, it was that the shim wasn't thick enough.

Widening it probably is why it is bent.

[Brian O.]

Originally Posted by mornish

the problem wasn't that the slit wasn't wide enough, it was that the shim wasn't thick enough.

Widening it probably is why it is bent.

Exactly, which is why I suggest he adds to the the shim to make it wider.

[mornish]

Originally Posted by Brian O.

Exactly, which is why I suggest he adds to the the shim to make it wider.

yes, that would help.

[1-wheeled-grape]

Yeah I reckon the shim will help. Try it and see.
Other wise a picture or two could help.

[Brian O.]

Originally Posted by 1-wheeled-grape

Yeah I reckon the shim will help. Try it and see.
Other wise a picture or two could help.

Theres no need for a picture, we know exactly whats happening. Hes trying to get the frame to clamp onto a post which is too small (even with the provided shim) and since he widened the opening its weaker and now bending inwards until it contacts the post. What he needs to do is increase the diameter of the post by adding onto the shim which a slice or two of thin metal from something such as a soda (pop?) can.

The frame wasn't a pain in the ass to begin with, you made it one unfortunately.

[1-wheeled-grape]

Originally Posted by Brian O.

Theres no need for a picture, we know exactly whats happening. Hes trying to get the frame to clamp onto a post which is too small (even with the provided shim) and since he widened the opening its weaker and now bending inwards until it contacts the post. What he needs to do is increase the diameter of the post by adding onto the shim which a slice or two of thin metal from something such as a soda (pop?) can.

The frame wasn't a pain in the ass to begin with, you made it one unfortunately.

Oh yeah got you, Sorry I got a little confused there that's all.

[feel the light]

The trouble is you are using a to small seat post with to small shims.

It would have been better to buy a KH post, but oh well.

Using the shims, you could have wrapped metal tape around the post, until it would fit tight.

I wish I knew what to say now. I would be tempted to buy a steel KH post, and pound it in, bending the metal back to stock position. I'm not sure if that is the right thing to do. Maybe it will crack.

If you do go that way, use a long steel KH post, and cut it as long as possible. You want to have as much overlap as possible between the post and frame. That will go a long way to reducing the stress on the weakened part of the frame.

I have never heard of a KH frame breaking at the clamp, I hope you don't become the first.

As I am sure you realize, this is not a fault of the frame. You should have used the right post.

[SkierAlex]

K, thanks. I'll try add a piece of can or something.

But the slit wasn't wide enough at the start. I even tried a 27.2mm seatpost in the frame at the start and it would twist easily when done up tight. The shim and seatpost are slightly thinner than a 27.2mm seatpost, but loads of other people use the municycle.com "diet set" with no problems I think. And the shim and post should fit, it's made to. But it didn't.

[skrobo]

Originally Posted by SkierAlex

K, thanks. I'll try add a piece of can or something.

But the slit wasn't wide enough at the start. I even tried a 27.2mm seatpost in the frame at the start and it would twist easily when done up tight. The shim and seatpost are slightly thinner than a 27.2mm seatpost, but loads of other people use the municycle.com "diet set" with no problems I think. And the shim and post should fit, it's made to. But it didn't.

are you sure you don't have a peice of crap seatclamp?

[SkierAlex]

Originally Posted by skrobo

are you sure you don't have a peice of crap seatclamp?

It's not that. Anyway even with a crap seatclamp it will stop tightening once it's tight around the post. For some reason the post + shim doesn't quite fit the frame. It should.

[feel the light]

I can see one of the slits you are talking about, in the rear of the frame, through the gap in my stock clamp. My post is tight, and the slit and clamp both have about 2 mm space left. The post fits snugly in the frame, even without using the clamp.

It would be helpful if you had a caliper, something is off on your setup. I somehow doubt your frame tubing size would be off that much, but I can't think of a better way to be sure then by measuring the parts.