thomson layback seatpost damaging seat tube?

I'm just wondering about the possibility of layback seatpost offered by thomson to cause frame cracking.

here is an offset seatpost and forces applied to the post and frame when a rider is sitting on the saddle:
offset part here is a cantilever and the momentum (green arrow) caused by the force (orange arrow) is trying to break the seatpost in the bent point


and here comes the layback seatpost:
green arrow shows the momentum which is much lower. red mark is on the side of seatpost being stretched and blue - pressed.



the position of the momentum and stretching force which appears here must somehow affect the frame.
i mean the momentum in offset seatpost affects more the point - trying to break it + is high enough so the critical stretching forces affect the upper part of the seatpost having less impast on the insertion area.

Whereas in layback version the seatpost is being bent less and the momentum in the point of bend is smaller - the frame takes it.

Before some lads start taking piss.
I'm not bored at work, just thinking if the laybacks are safe...

I've publised the question here not at irish DH because this is the place where grown ups are and some clever minds too

The seat post will only damage your frame if you do not have enough inserted in the frame. The thing you have to be careful about is that some frames where the seattube extends more than 40mm or so above the top tube without some sort of brace. If this us the case you need to make sure with the seatpost at it's max mark that the end of of the seatpost is inserted past or at least level with the bottom of the top tube. This will stop the post trying to tear off the top of your seat tube

Have to agree with Al there..

The only time I've seen a seatpost break a frame is when its up way too high..

I wouldn't worry about the Thomson layback seatpost Luka... if they were causing frames to break then we would have heard about it a long time ago..

i ride this bike with the MAX mark where the blue line is, regarding to what you said above are you suggesting i should be having it lower (orange line)?



EDIT: sorry, my mistake: the end of the seatpost should be at the orange line or deeper

thank you Al, thank you Gerry

Luka I think the important thing is that the bottom of the seatpost is below the brace on the frame ie. below the yellow line on the photo above. If it is you shouldn't have a problem.

is this a windup ?

It is way below indeed. Thank you. And i think Gerry is right that we'd here about layback versions if they were causing any damage.
I still think the layback design "pulls" the top tube backwards more than offset. As long as it's safe for the fame, it's ok.

Cheers

oh no, i'm not allowed telling jokes on this forum.

just technical question in technical section of a mountainbiking forum.

OMG...This is by far the geekiest post I've seen in here, I hope you have prepared yourself for some serious abuse!

go on, hit me

Even I'm shocked Luka, shocked, bewildered and a bit hungry.

Oh I don't know about that! I know for a fact that one of the senior club (and committee) members broke a frame because he only inserted the seat post a couple of inches into the seat tube of his scandium race bike!

where did it all go wrong for me ?

where did it all go wrong for me ?

when you joined "LinkedIn" !