....the "new" Velo Orange layback seatpost?

[reohn2]

........I will have a play with my post and report back in a few days.

[531colin]

OK, I have had a look at my Planet X seatpost.
Bearing in mind this is based on a sample of ONE "original" Velo Orange Grand Cru and ONE Planet X Holdsworth seatpost, and my tools are old and un-calibrated, and my eyesight is not what it was, here are my findings.....
Both posts measure close to 27.2mm by my Vernier gauge. It is a vernier, not a modern digital, so it is open to interpretation and my dodgy eyesight.
Both posts appear to be in the region of 27.19mm, I didn't find them significantly different in size, and I didn't find significant variation measuring in different places or different planes.
The original VO post is a reasonable fit in my Spa Ti bike. With the clamp undone, there is a touch of rocking, but its not a "fit" like a prick in a bucket, and it doesn't creak or creep down. The Planet X Holdsworth seatpost fitted similarly. I don't have the manufacturer's spec. for the seat tube (shimmed from 31.8 )
I greased the cradle bolt threads, and tightened them to 5nm, and I can't feel or see the saddle move.

So, I don't know whats going on!

[Brucey]

I've not had a chance to examine one of these seat pins in person, so what stops the saddle from tilting, exactly?

- serrations?
-wedging action? (as per hockey stick)
- friction?

If 'friction' only then not only do the surfaces have to be bone dry and scrupulously clean, but they also have to fit one another very well. If the bolts are overtightened (even once) this is unlikely to remain the case, even if it was so to start with. Obviously if the bolts are not tight enough, the thing will slip, and once it has slipped, it may carry on slipping if the friction is dependant on the surface finish in any way.

BTW re bikepacker's situation;

1) if you want to demonstrate that the seat pin is the wrong size, it is easy enough to measure it using a micrometer or a set of verniers, higher up where you have not modified it? You shouldn't be having to argue about this point any more than you should be struggling to get the thing into the frame in the first place.

2) 'tightening the bolts to the right amount' is a meaningless statement. The test at least should have been done with a specified torque setting/bolt lubrication condition. If there is no torque setting recommended by the manufacturer, that is cause for criticism.

3) Apologies if this is b-obvious, but that a 27.2mm reamer starts in your frame means very little. Reamers are almost invariably tapered. [If they were not, you would never be able to start them in the hole that you are trying to make the correct size]. The hole is only the correct size once the parallel-sided (i.e. upper) part of the reamer has gone as far down in the frame as the bottom of the seat pin will go. Even then if the reamer is worn, or not as described, the hole still won't be the right size. Again this can be checked easily enough.

4) Historically very many bike manufacturers have routinely fitted seat pins that are 0.1 or 0.2mm undersize vs the tube size (because it spares them having to ream the frame...). Also not all seat pins are the size they say they are, either; they are usually undersize if anything, and one that is better made might not go into a frame that has been used with the wrong sort previously.

Anyone who 'understands engineering' would know all these things and would perhaps have been able to advise you better; it may well be that the seat pin you bought was not correctly sized and has a defective clamp, but I can see how there would be room for doubt in the mind of your seat pin supplier, especially if no-one else has made similar complaints.

cheers

[531colin]

Friction.

Top of the "hockey stick.......



Underside of the cradle......



Cradle on the hockey stick......



and from below.....



Underneath the hockey stick there is a concave area



These serrations seat there, but are they cosmetic or functional?



Photos are here (page 3) if you want them bigger.....https://www.flickr.com/photos/52358536@N06/albums/72157624571269648/page3

Photos of it all assembled here....http://www.planetx.co.uk/i/q/SPHOGS/holdsworth-gran-sport-seatpost

I will bung it on a bike and give it a ride

[bikepacker]

Brucey, thank you for that lengthy assessment but I am at a loss to know to who it was aimed. Having built my first bike 64 years ago at the age of 8 there an element of teaching your grandmother to suck eggs, if it was aimed at me.

[Brucey]

Brucey, thank you for that lengthy assessment but I am at a loss to know to who it was aimed.

at anyone in the same situation really; you may well have legitimate gripe but if I were going to have a go at the supplier of a part, I'd try to offer something other than what might be (from their point of view) potentially circumstantial evidence. A set of £10 digital verniers would offer a more compelling argument, for example. I'd probably not have started grinding the seat pin away, either, because as soon as you have done that it makes it difficult to argue for an exchange or refund.

Having built my first bike 64 years ago at the age of 8 there an element of teaching your grandmother to suck eggs, if it was aimed at me.

I learn new stuff every day, and I hope it never gets to be any different to that.

cheers

[Brucey]

Friction......

thanks for that... I think I can see how the thing is meant to work.

If there were any grease on any of the bearing faces (apart from the bolt perhaps) I can see how the thing might slip. I'm not sure the 'teeth' on the bottom plate will do much...?

I assume that the bolts are high tensile M6 x 1.0 threaded bolts; chrome plated (rather than stainless steel?). If so, the maximum torque setting is likely in the range of 5 to 8 Nm. Does either the Holdsworth or VO seat pin come with instructions on this point?

cheers

[bikepacker]

A set of £10 digital verniers would offer a more compelling argument, for example. I'd probably not have started grinding the seat pin away, either, because as soon as you have done that it makes it difficult to argue for an exchange or refund.

cheers

I did check them with verniers and they it was oversize but it didn't matter as I was also shortening the post I was happy to grind it to size. On what your assumption is based regarding 'arguing for an exchange or refund' I am not sure. Because I have not requested either.

[531colin]

Friction......

thanks for that... I think I can see how the thing is meant to work.

If there were any grease on any of the bearing faces (apart from the bolt perhaps) I can see how the thing might slip. I'm not sure the 'teeth' on the bottom plate will do much...?

I assume that the bolts are high tensile M6 x 1.0 threaded bolts; chrome plated (rather than stainless steel?). If so, the maximum torque setting is likely in the range of 5 to 8 Nm. Does either the Holdsworth or VO seat pin come with instructions on this point?

cheers

No instructions at all with the Planet X post.
I don't remember any with the Original Mk 1 Velo Orange post either, but I've slept since then.......

[Brucey]

I did check them with verniers and they it was oversize but it didn't matter as I was also shortening the post...

it occurs to me that if you wanted to convince your supplier that his seat pins are sometimes oversize, you could perhaps send them the (presumably still oversize) offcut...?

cheers

[531colin]

Been for a short ride with a bit of roughstuff, nothing to report. I'll leave it on.
Out of interest, I fitted it just doing the bolts up "as tight as I normally would" and then put the torque wrench on them, they came out between 7 and 8 nm.
I can't see how the extravagant toothy bits on the underneath bit would stop it slipping....if its going to slip, there will be some lost motion between the saddle (cradle) and the underneath bit.

[bikepacker]

I assume that the bolts are high tensile M6 x 1.0 threaded bolts; chrome plated (rather than stainless steel?). If so, the maximum torque setting is likely in the range of 5 to 8 Nm. Does either the Holdsworth or VO seat pin come with instructions on this point?

cheers

Without conducting a full metallurgy test I cannot swear to the composition of the metal but being non-magnetic there is a reason to believe they are stainless steel.

[bikepacker]

I did check them with verniers and they it was oversize but it didn't matter as I was also shortening the post...

it occurs to me that if you wanted to convince your supplier that his seat pins are sometimes oversize, you could perhaps send them the (presumably still oversize) offcut...?

cheers

Not my place to convince them I only pointed out the fact to them.

[Brucey]

I assume that the bolts are high tensile M6 x 1.0 threaded bolts; chrome plated (rather than stainless steel?). If so, the maximum torque setting is likely in the range of 5 to 8 Nm. Does either the Holdsworth or VO seat pin come with instructions on this point?

cheers

Without conducting a full metallurgy test I cannot swear to the composition of the metal but being non-magnetic there is a reason to believe they are stainless steel.

fair point. I guess if they were titanium they'd say so....

If they are stainless (with no strength grade marked) then it is quite possible that 8Nm is a bit ambitious.

cheers

[531colin]

When I test ride (Spa) prototype bikes, I always put one of my own saddles on, so I have my spare saddle currently attached to this "Planet X" seatpost.
Current score is.....
tried it on my own bike.....OK
2 prototypes....OK
Each bike, I have set up seat height, angle and layback critically. I haven't had any slipping. Setting angle and layback with this pattern post is a bit of a faff, because when you undo the 2 bolts the saddle is on the move both fore and aft and relative to the horizontal. The original Velo Orange post is a conventional design where the 2 adjustments are almost completely separate, so in that regard the old post is better.
However, most people don't do this very often, so on that basis I find this post OK for the money.....its difficult to find long layback seatposts at the Planet X price.