I broke a seat post.

http://www.ebay.com/itm/New-ITM-Forg...-/181343516543

It's lasted several years, and wasn't especially expensive or light, but
I'm not a heavy rider and don't expect to break such things.

It is a fairly crap design, in my opinion. The post is an Al tube with
a thin layer of CFRP. That in itself isn't so much in issue. Heck, the
plastic coating helps prevent corrosion and welding in a steel frame.

The bad part is that the seat clamp is a forged and machined part, and
only inserts into the tube with a plug about an inch long, and held with
glue.

The tube split down the back and opened enough to let the seat rotate.

It is now retired.

--
JS

tubes are made from flat sheets then welded into tubes with a seam ...

amazing. mine break of under the saddle holder.

Once bit...there's a spare on hand at uhuhuh 24.7869 mm

On Thursday, April 3, 2014 9:57:05 PM UTC-4, x wrote:
tubes are made from flat sheets then welded into tubes with a seam ...
Snipped

Not if the tube is drawn when being formed.

Cheers

On 4/3/2014 9:57 PM, DATAKOLL MARINE RESEARCH wrote:
tubes are made from flat sheets then welded into tubes with a seam ...

Most aluminum tubes are instead formed by extrusion. There's no welding
involved, unless you count the location within the die, where the hot
but solid material flows around the "spider" supports.

--
- Frank Krygowski

Seamless Metal tubing used in bicycle frames can be manufactured in two different ways: *Seamless tubing begins as a solid round bar, which is heated to a workable temperature, then pierced by a mandrel. It goes through a series of rolling operations to bring the diameter and wall thickness to the desired sizes.
*Seamed tubing begins as a strip of flat sheet metal, which is curled into a tubular shape, then the edges are welded together. After this, the seamed tubing may also go through various rolling steps. Seamed tubing is cheaper, but weaker than seamless tubing. Generally, all better-quality bicycle frames are made from seamless tubing.

Allen/Brown/Harris

On Friday, April 4, 2014 3:38:42 AM UTC+2, James wrote:
http://www.ebay.com/itm/New-ITM-Forg...-/181343516543



It's lasted several years, and wasn't especially expensive or light, but

I'm not a heavy rider and don't expect to break such things.



It is a fairly crap design, in my opinion. The post is an Al tube with

a thin layer of CFRP. That in itself isn't so much in issue. Heck, the

plastic coating helps prevent corrosion and welding in a steel frame.



The bad part is that the seat clamp is a forged and machined part, and

only inserts into the tube with a plug about an inch long, and held with

glue.

That is why I like my Thomson posts.

Lou

On 4/3/2014 8:57
PM, DATAKOLL MARINE RESEARCH wrote:
tubes are made from flat sheets then welded into tubes with a seam ...

amazing. mine break of under the saddle holder.

Once bit...there's a spare on hand at uhuhuh 24.7869 mm


Tubes and pipes may be seamless or seamed:

http://www.tubecon.co.za/en/technica...i/tube-vs-pipe

Plenty of examples both ways.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 4/3/2014 6:38 PM, James wrote:
http://www.ebay.com/itm/New-ITM-Forg...-/181343516543


It's lasted several years, and wasn't especially expensive or light, but
I'm not a heavy rider and don't expect to break such things.

It is a fairly crap design, in my opinion. The post is an Al tube with
a thin layer of CFRP.

The CFRP is just a conformal coating to make the aluminum seat post
appear to be a carbon fiber seat post. But neither aluminum or carbon
fiber is a great material for seat posts. Check
http://www.rivbike.com/Saddles-Seat-Posts-s/48.htm?searching=Y&sort=2&cat=48&show=12&page=1
for some good replacements.

Another CF seatpost recall that was in my inbox today, even though it
happened last year:
http://www.bicycleretailer.com/north-america/2013/08/08/giant-recalls-200-bikes-due-seatposts

On 4/4/2014 9:13 AM, AMuzi wrote:
On 4/3/2014 8:57
PM, DATAKOLL MARINE RESEARCH wrote:
tubes are made from flat sheets then welded into tubes with a seam ...

amazing. mine break of under the saddle holder.

Once bit...there's a spare on hand at uhuhuh 24.7869 mm


Tubes and pipes may be seamless or seamed:

http://www.tubecon.co.za/en/technica...i/tube-vs-pipe

Plenty of examples both ways.


But, AFAIK, not in aluminum. Aluminum is outstandingly suited to
extrusion, and while it's possible that some aluminum tubes of ordinary
size are made by welding aluminum strip, I've never seen a single
example. Extrusion allows the conversion of a (say) 8" diameter x 24"
billet of aluminum into a seamless tube, using only one step. Something
very unusual would be needed to justify doing it any other way.

Aluminum extrusion (specifically, direct hot extrusion) is an important
industry in my area. In fact, one of my uncles was an extrusion
diemaker. When I taught a manufacturing processes course, I was able to
get several extrusion dies and matching product samples to use as
in-class examples.

Final bit of trivia: Back when Bike Nashbar was a local company (before
it was sold to Performance) the closest neighbor to Nashbar's
headquarters was one of our area's largest aluminum extrusion firms.

--
- Frank Krygowski

I remember Kalloy posts with a weld down the side....J's tube split where ?

but Kalloy isn't going that way http://kalloyuno.com/ muh muh muh more aerospace

quick search only reveals woe

https://www.google.com/#q=welded+sea...tubing&spell=1

Plucked a pipe frame from the dumpster maybe 15 years ago ditched by a evacuating retiree...HEAVY Dude ! and worser dead balance DEAD !

I gotta go n grind down those new CR bolts....