Broken CF seat base

[Spencer_Hochberg]

@muzzle

This thread has shifted topic, larl. Anyways, people who use “stiff stick” or similar, have you noticed stress being transferred from the seat to the frame?

This is obviously going to happen from this sort of reinforcment, although the effect could vary. When Cody snapped his torker cx frame for instance, that can hardly be blamed on the seatpost, because torker don’t have the best reputation as far as frame build quality goes.

My worry would be that doing this to a cheap seatpost to reinforce a cheap seatbase could, in the long run, destroy an expensive (in comparison) KH frame.

I won’t be doing this type of reinforcment any time soon, and regardless of whether I like the design or not, I would rather shell out $140NZ for a new CF base when I manage to break one than to pay $250NZ for a new frame.

Cody rides a very high seat so there was a lot of post still under the reinforcement. So instead of doing damage to the seat it was all on the seat post and he bent it right under where the reinforcement is welded. So I think it is very possible to damage a frame especially with a 27.2 post. The one that I am thinking of that Cody bent was a 25.4 so the bigger post would be stronger and more force would go to the frame. I would definitely not use it on an aluminum frame.

[muzzle]

@Spencer Hochberg

I would definitely not use it on an aluminum frame.

They would probably be mostly fine in a Nimbus II trials frame tho, has anyone ever broken one of those things (other than a rusted through or neglected one)?

[Evan_Byrne]

Reinforment post and koxx or nimbus/yuni frame would be your best bet.

[john_childs]

@muzzle

My worry would be that doing this to a cheap seatpost to reinforce a cheap seatbase could, in the long run, destroy an expensive (in comparison) KH frame.

Why would it put more force on the frame compared to a stiff CF seat? Both would transfer a similar moment force to the frame if you landed hard on the nose of the saddle. The CF might have more flex and give to absorb some of the force, but it’s a similar force transmitted nonetheless.

The important bit is to have enough seatpost inserted in the frame so you don’t damage the upper clamping area part of the frame. The KH frames have a short neck so if you raise the seat too high you can easily end up with too little seatpost in the frame and damage the frame that way.

One thing you might do with the “stiff stick” style of reinforcement would be to put some rubber or some sort of elastomer between the stiff stick and the nose of the saddle. That would give the saddle some more give and lessen the amount of force transfered to the frame.

[muzzle]

@john_childs

Why would it put more force on the frame compared to a stiff CF seat? Both would transfer a similar moment force to the frame if you landed hard on the nose of the saddle. The CF might have more flex and give to absorb some of the force, but it’s a similar force transmitted nonetheless.

Yeah, thats logical too

[Unicaw89]

@Spencer Hochberg

Cody rides a very high seat so there was a lot of post still under the reinforcement. So instead of doing damage to the seat it was all on the seat post and he bent it right under where the reinforcement is welded. So I think it is very possible to damage a frame especially with a 27.2 post. The one that I am thinking of that Cody bent was a 25.4 so the bigger post would be stronger and more force would go to the frame. I would definitely not use it on an aluminum frame.

Heheh, I have tried to make reinforcments on alu posts…ended pretty messy lol, they just dont seem to help at all. But as pence said it did take the stress off of the brackets that I kept bending and of fthe seat base, but it put it all dead center of my seat post causeing mt to “bannana” many steel posts…

[john_childs]

@Unicaw89

Heheh, I have tried to make reinforcments on alu posts…ended pretty messy lol, they just dont seem to help at all. But as pence said it did take the stress off of the brackets that I kept bending and of fthe seat base, but it put it all dead center of my seat post causeing mt to “bannana” many steel posts…

Could the banana seatposts be caused by the heat from the welding weakening the steel seatpost in that area rather than the forces of the saddle being transfered through the stiff stick?

[ivan]

@muzzle

WOW! We don’t even have that many in our entire country, well as far as I know anyways.

+1

I’m probably the only one who’s got an ordinary Kris Holm saddle on the whole island.

[enahs]

If you want to make your own seat you could go with a CF/kevlar hybrid material. http://www.shopmaninc.com/hybrids.html

[CKCrowe]

I JUST GOT MY CF SEAT TODAY!!!
My dad was wondering what kind of bit, if any special kind he should use to drill it?
would rubber patches work well inbetween the CF seat and the bolts on it?
Then any other stuff I should do to it to make it last as long as possible.

[mornish]

@CKCrowe

I JUST GOT MY CF SEAT TODAY!!!
My dad was wondering what kind of bit, if any special kind he should use to drill it?
would rubber patches work well inbetween the CF seat and the bolts on it?
Then any other stuff I should do to it to make it last as long as possible.

yeah, little slips of rubber (like from an old tube) would work well to put inbetween the seatpost and the base.

I dont know about special bits, but if you have a square file that would be better than a triangle one.

[CKCrowe]

K, Ive used to square chizzle that my had, My dad drilled the holes. Everything is going really well with it, i put the rubber part on the base (bottom of the seat where the nuts screw on:D ?)
So is that all, should last a long time?
Oh and when i took my other seat apart it was broken:(
at least that wont hopefully be happening agian.

[Brian_O]

@CKCrowe

at least that wont hopefully be happening agian.

Hopefully.

[muzzle]

@muzzle

My worry would be that doing this to a cheap seatpost to reinforce a cheap seatbase could, in the long run, destroy an expensive (in comparison) KH frame.

I won’t be doing this type of reinforcment any time soon, and regardless of whether I like the design or not, I would rather shell out $140NZ for a new CF base when I manage to break one than to pay $250NZ for a new frame.

It may be fair to note, that I managed to snap my KH '06 frame last year too… Was riding with a modified classic saddle and cromo seatpost at the time.

[siafirede]

You have some really bad luck with equipment!

I think it is just the unicycle gods trying to level out the playing field for everyone else. You were crazy good at street/trials last year when I was over in Auckland.

Where did the frame snap by the way?

[UniDudeDX]

@CKCrowe

K, Ive used to square chizzle that my had, My dad drilled the holes. Everything is going really well with it, i put the rubber part on the base (bottom of the seat where the nuts screw on:D ?)
So is that all, should last a long time?
Oh and when i took my other seat apart it was broken:(
at least that wont hopefully be happening agian.

HOW LONG DID IT TAKE YOU TO DRILL AND FILE OUT THE HOLES???

[Nimbusnut]

I don’t have a CF base (yet) so I may be way out of bounds, but would it be better to not have clean 90 degree corners in the holes but round them slightly and then knock the corners off the bolts enough for a clean fit? Feel free to tell me to shut up because this is a guess, but it seems like eliminating the clean sharp angles may lessen the possibility of small running cracks forming. Maybe even changing the orientation of the squares by 90 degrees or having each pair 90 degrees off both front and rear.

[UniDudeDX]

@Nimbusnut

I don’t have a CF base (yet) so I may be way out of bounds, but would it be better to not have clean 90 degree corners in the holes but round them slightly and then knock the corners off the bolts enough for a clean fit? Feel free to tell me to shut up because this is a guess, but it seems like eliminating the clean sharp angles may lessen the possibility of small running cracks forming. Maybe even changing the orientation of the squares by 90 degrees or having each pair 90 degrees off both front and rear.

no cause when you try to tightent the bolts…its just gonna spin…

[unicycledood]

Not if you do it right. Thats sort of what I’ve done.

I didn’t exactly do it on purpose the first time but the bolt fit nicely so I did the rest accordingly.

[muzzle]

@Nimbusnut

I don’t have a CF base (yet) so I may be way out of bounds, but would it be better to not have clean 90 degree corners in the holes but round them slightly and then knock the corners off the bolts enough for a clean fit? Feel free to tell me to shut up because this is a guess, but it seems like eliminating the clean sharp angles may lessen the possibility of small running cracks forming. Maybe even changing the orientation of the squares by 90 degrees or having each pair 90 degrees off both front and rear.

I think that is a great idea. I will most likely do this when I get CF base #2.
It seems like that might prevent it from snapping so easily this time.