Seatpost Design Discussion for Engineers

[Johan Bornman]

http://cozybeehive.blogspot.com/2009/03/thomson-elite-seatpost-failure.html

 

 

This is a nice look at how a particular seatpost was designed and eventually failed in contradiction to its design parameters.

 

 

[Wyatt Earp]

 

 

I will add my 1 c worth to this topic.

 

I have been riding and installing Thomson posts for around 7 years now and I have NEVER, and I repeat NEVER seen that type of failure on a Thomson seatpost.

 

There must be something fishy that has happened to that post.

 

Do we have proof that he , the user is telling the truth ?Summit Cycles2009-04-17 00:13:25

[Dirtbreath]

Summit, apart from launching your now predictable responses to anything Johan posts what do you think could have caused this failure? Overtightening of the bolts? Some impact that took a while to propogate?

[kennyg]

It looks like a material problem...

But we know, the design, manufacture, testing loop.  I have done some detailed QC work. Maybe Thompson needs to pull there aging data, on the material

[AndreZA]

I still think it is one of the nicest piece of cycling equipment ever produced. I think this kind of stuff happens. Just think back a few weeks when everybody panicked when a broken KCNC stem was shown. It's like that insurance ad on the radio where the guy crashed his tractor because the steering bolt was missing due to the assembler in Germany watching football.

 

 

 

I think the guy on that blog should join the Hub and have his nic as "Thomson Sucks".

[Roders]

I would hazzard a guess and say the saddle clamping arrangement was welded to the tube. The welded area should go through an anealing process after welding to relieve any stresses. In any production process things can slip and this seat post probably slipped through without being annealed, can happen!!

[AndreZA]

I would hazzard a guess and say the saddle clamping arrangement was welded to the tube.

 

 

 

Thomson posts and stems are machined from a single piece of alu. There is no welding, gluing or bonding of any sorts involved.

[Wyatt Earp]

Dirt Breff (as Nancy calls it)

 

I have edited, hope you are glad, I simply cannot understand why there has to be a skepticism towards ALL manufacturers (hope that clears it up)

 

I wish I could give you an honest opinion however none of us are qualified enough to give an opinion unless we have the actual post in our hands and do various tests around the actual product.

 

Unless this gets done, I believe that every opinion is simply speculative.

 

 

 

I do however think that this particular rider must have had a crash or two or several and that could have weakened the post in that area, not cleaning his bike and inspecting it properly, he might not have seen a small crack that might have developed, from crashing (my opinion of course and just my speculation)

 

 

 

Jagwil said it could be the material, I feel that the post in question should go to Thomson for an analysis.

 

 

 

As Mampara said as well, this kind of stuff happens, should we accept it, if it was poor manufacture.

 

My answer is no, but this is not something we see on a Thomson post everyday so it's out of the norm for Thomson which casts a shadow of doubt as to what "MIGHT" have happened.

 

 

 

Just out of interest, I am going to guess that the second post in the picture is a Masterpiece, I would love to know the weight, size, type of bike and riding style of the owner regarding said post.

 

 

 

 

[turtlek]

could it be that the rider had crashed before and made an impact crack due to the crash being out of the line of suggested use of the bike (for example free riding on an XC bike) and when he went to the coffee shop afterwards and the bike fell the damage that was done earlier became known and hence the pictures you are seeing now??

[splat]

Before there is wide spread panic - how may broken Thomson seatposts are there in the world vs how many have been sold?

[turtlek]

Before there is wide spread panic - how may broken Thomson seatposts are there in the world vs how many have been sold?

 

 

 

probably the same amount of broken carbon bikes and broken wheelsets you cant say that a manufacturer is bad because 10percent of thier manufactured products are bad apples when 90percent are all still in perfect working order

[gummibear]

I have just ordered one of these so i will have to see how it holds up.

I don't  see how that post can break and he doesn't mention about any other parts that broke or bent.

 

[Bos]

Dirt Breff (as Nancy calls it)
I have edited' date=' hope you are glad, I simply cannot understand why there has to be a skepticism towards ALL manufacturers (hope that clears it up)
I wish I could give you an honest opinion however none of us are qualified enough to give an opinion unless we have the actual post in our hands and do various tests around the actual product.
Unless this gets done, I believe that every opinion is simply speculative.

I do however think that this particular rider must have had a crash or two or several and that could have weakened the post in that area, not cleaning his bike and inspecting it properly, he might not have seen a small crack that might have developed, from crashing (my opinion of course and just my speculation)

Jagwil said it could be the material, I feel that the post in question should go to Thomson for an analysis.

As Mampara said as well, this kind of stuff happens, should we accept it, if it was poor manufacture.
My answer is no, but this is not something we see on a Thomson post everyday so it's out of the norm for Thomson which casts a shadow of doubt as to what "MIGHT" have happened.

Just out of interest, I am going to guess that the second post in the picture is a Masterpiece, I would love to know the weight, size, type of bike and riding style of the owner regarding said post.

[/quote']

 

Im With you.. I dont think this one faliure must put Years and Years of superior products In a bad light..

 

There Is actually a whole lot of reasons for this Starting the moment this product left the Manufacturing facility...

 

 

[Wyatt Earp]

Dirt Breath

 

 

 

You grilled me, but I have posted for a reason.

 

I cannot see the purpose of a topic like this besides that it will cause some doubt in the minds of some folks.

 

If you would like to, give me a call and we can talk Thomson.

 

I will gladly also post pics of a Masterpiece and an Elite to show the differences if you all would like that.

 

Windblown

 

You don't have anything to worry about, I have never had a single Thomson failure in my hands.

 

Splat you mak a valid point and I made mention to this in an earlier posting.

[SwissVan]

 

 

 

 

 

Chances are the seat was the first contact point and the force could have been quite substantial especialy if the surface was a hard one like concrete. 

 

After 4 years I dont think the guy can complain, who knows what other stress the ear has been exposed to in this time.

 

Proof that sh*t does happen.

 

 

[Wyatt Earp]

Sorry Okes, I just noticed that the Masterpiece is gone, so I can't post a pic, I apologise.