P.O.S. Carbon fiber seat base

[m_extreme_uni]

After a recent trials spree, i have done the not-yet-done, broken the not-yet-broken, famed Carbon fibre miyata base.



This based was correctly drilled, had carefully filed holes, and was good untill it broke, in two different places.

Te first place was right at the back, on the left (at first) near the back of the seat post. The next place was in front of the seat post attachement.

This really sucks, since theses arent cheap pieces of unicycling gear.

I am very disapointed with this product. I thought it was the only option for a strong seat, and now it's broken.

I think it is possible for this seat to be a defect, but unlikely.

-Ryan AtkinsPictures

[U-Turn]

When and how did you notice that it was broken?

[m_extreme_uni]

about 2 weeks ago, there was a slight line in the back of the base, and it still felt solid, so i kept riding, it looked like nothing, and the front showed no sign of breaking.

-Ryan

[Darren]

Ryan

I hear you came in second place at the
Test of Metal trials competition !!!
Awesome job.

Roger at uni.com.uk is a decent guy. I'm sure he will help you out with the seat base.
Maybe you should get a prize for being the first to crack one.

See ya,
Darren

[muni_guy]

Ryan,

You animal!

Unfortunately there is no such thing as un unbreakable product, everything gives with time and use. I'd have to say that the carbon fibre base is still the strongest option out of the products that currently exist. To design a stronger base would probably result in a higher cost. Perhaps in a few years we may see aerogel seat bases.

Carl

[jagur]

OH MY GAWD!

no Reeder handle either,amazing.

[gauss]

Nice work! I was looking at the pictures trying to figure out why it failed. You may be able to increase the failure load of the seat if you put a thin rubber shim between the seat and the top of the seat post base. Something near 40-50 on the shore A scale. When testing composites we often have to do this sort of thing as the test fixture is much much stiffer than the composite. Because the part of the seat post that clamps to the seat is so much stiffer than the seat it takes all the load right up to the edge of the steel plate. Then all the load transfers suddenly to the seat base. The rubber makes the transition more gradual. You would only need a few millimeters. I don't know if this would impart a squishy unconnected feel to the uni (probably no more than an airseat), but it is worth a try (mess with the rubber hardness and thickness. www.mcmaster.com is a great source for rubber sheets. We cut them to shape with a water jet, but tin snips should cut it well. Another option is to perforate the steel plate so that the stiffness of the plate is reduced to closer of that of the carbon fiber composite. Just a few suggestions that I would try. They may or may not work. It sucks when expensive things break.
-gauss

[m_extreme_uni]

Could i use any household items for that type of thing? maybe an innertube?

Or could i buy some of that rubber stuff from a hardware store?

Could i possible use neoprene from a wetsuit?

I like this idea

-Ryan

[U-Turn]

I imagine a couple of thicknesses of DH tube would work, what do you think Gauss?

But it looks to me as though the seat failed at the lower lip and then the failure travelled up to the adapter. The lower lip is where all the seat flex stress would be; is it not? Perhaps the seat winding needs a few layers of fibers over the lower lip that go in a different direction.

[jagur]

Gauss's idea sounds like a good one.

kinda like the plastic base plates that go inbetween the board and the trucks on a skateboard.they are also known as riser pads.

[m_extreme_uni]

To add to this tale of unicycling woe, in the same ride, i really badly bent my seatpost, and also bent my left profile (the one i haven't yet bent) so, now i've bent both

This extreme unicycling is a messy / expensive business

-Ryan

[paco]

You animal!

Nice work!

I love the fact that we're applauding Ryan for breaking something on his unicycle. I understand, though. I felt so good when I broke my first crank arm.

[SEMPER_UNI]

Ouch!

alright, to adress everything thusfar mentioned...

the rubber pad to disperse the stresses caused by the stiff plate mounted to the seatbase would work well to pad the Carbon fiber. another good way to reduct the likelyhood of something like this happening would be to grind or file the sharper edges of your mounting bracket.
i took my seat apart within days of first building it and noticed that the plate at the top of my seatpost had scratched or cut the bottom of my seat base. i know that this will eventually lead to failure, buti just have to deal with that, but i rounded off the edges that created the scratch and i think things will be fine for a while anyway.

as far as the crack starting on the edge, or lip... my seat base was very rough around its edges, not very well manufactured in my opinion... i took a disk sander and smoothed out the lips all around the seat base. with a few different peices of sand paper i was able to create a smooth uniform edges all the way aournd.
the jagged edges as they were created alot of little stress risers, or places where all the stress in the seat was focused. never thought about it causeing failure, but it makes sense.

my biggest comlaint about the "carbon fiber" seat base is that it appears to actually be a fiberglass core with a layer of vacumed molded CF on the bottom, and a horribly hand layed layer on top.
where the edges ar ground and where the holed are drilled and filed, you can easily see that the middle is a white-ish color...

for the money i was expecting real carbon fiber all the way through, not a peice of plastic with two layers!

if these bases were the same thickness they are now but 100 percent CF, they would be far stiffer and probably more durable.

Ryan, sorry about the bending. hope you've got a good job this summer. that thing i promissed you will be on it's way very soon, i've got one for jeff too. sorry about the wait. later

On Wed, 25 Jun 2003 22:17:46 -0500, muni_guy
<muni_guy.pm281@timelimit.unicyclist.com> wrote:

>Perhaps in a few years we may see aerogel seat bases.

I've come across aerogel professionally while doing some research.
Aerogel is very very light (can go down to 0.003 times the density of
water), it is strong for its weight but it is weak for its volume. It
doesn't look like a good seat base material.

Klaas Bil - Newsgroup Addict
--
"No two crotches are alike. If they are, I don't want to know about it. - John Foss, on seat comfort."

[johnfoss]

Originally posted by jagur
OH MY GAWD!

no Reeder handle either,amazing.

Yes, someone had to be the first to break one. Bummer. But judging from a cursory glance at the photos, it doesn't look like the carbon was thin or anything like that. More likely you just used it real hard.

I wonder if a Reeder handle or similar would have helped? The break at the front was probably the result of millions of hops. The handle may have moved the stresses on the seat to a different area, making it last longer. Or they may have concentrated the forces, making the seat fail earlier.

Your next possible step is to look into the frame-attached handles being made by Carol Dingemans. Look for a thread by Max on the subject. This takes the stress off the seat (at least as applies to the front) and moves it to the frame. Probably cheaper and easier to replace, too.

(added later) That is, unless your breakage is the result of seated landing on big drops. Ouch. Probably not, because you might have mentioned something like that. Try not to land on the seat! But whatever you're doing, it's clearly out there at the far end of 'extreme' territory!