Two-bolt seatpost designs

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Samuel D
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Two-bolt seatpost designs

Postby Samuel D » 24 Apr 2018, 11:54am

I’ve been looking at photos of classic Campagnolo Record seatposts with the two-bolt design. The 1044 and others with the same basic design. Somehow I’ve never had the chance to study one of these in the wild.

The key to this design appears to be that the bottom jaw of the rail clamp is free to pivot about its middle in the pitch orientation (like a see-saw). The bolts screw into freely rotating collars to accommodate the changing angle of the lower jaw without subjecting the bolts to bending moments.

Consequently, it looks like the pitch of the saddle can be super-precisely regulated by tightening one bolt and loosening the other by the same amount. Alternatively, loosening one bolt only – either one – should allow the saddle to slide to and fro on its rails, after which the bolt can be re-tightened by the same amount to exactly retain the saddle’s original pitch angle.

This is brilliant! Why aren’t all seatposts made like this?

For that matter, are any seatposts made like this today? I can’t tell from photos whether the Nitto S83 and S84 operate on a similar but upside-down principle.

Brucey
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Re: Two-bolt seatpost designs

Postby Brucey » 24 Apr 2018, 12:21pm

appearances are not deceptive, that is how they work and it is a pretty good scheme. I have used this design (in preference to almost every other) for decades. These days I am less hard on equipment and these seat pins are difficult to get hold of so I have relented somewhat but I got as far as making my own 350mm length version of this seat pin for a MTB...

First versions appeared in the 1950s

Image

The only thing is that some versions of the campag design use forged aluminium parts for the clamps and these are not proof against the great british weather; they corrode so badly they can even split 'along the grain' as it were. The models that use steel parts are far more reliable. The downside of this is that the weight is more, obviously, and the steel parts can go rusty.

SR made a copy of this design and despite using aluminium for the clamps they don't corrode as easily as the campag parts do. I think they used a less strong but more corrosion resistant grade. There is also a Sugino version using this kind of design, and a Zeus model too.

You would be amazed at how many people squirrel these seat pins away and manage to lose one or both of the lower rail supports, or manage to fit the front upper clamp at the rear and vice versa (they are different). This is a first generation SR seat pin

Image

with the aluminum lower clamps and non-standard 'cylinder nuts'. The upper clamps are fitted the wrong way round.

In the Campag design the bolts are M7 x 1 threaded. In various copies they are usually not, but for most purposes M6 x 1 bolts seem adequate, despite M7 being ~40% stronger in tension (for the same grade bolt).

A downside of this seat pin design is that adjustment is difficult. Campag used to make a special spanner to work the bolts with, and even then it was still awkward. My tip is that if you need to change the saddle angle, just back the rear bolt out until everything is very loose, then turn the front bolt with your fingers to make the adjustment, then retighten the rear bolt. A flex-headed ratchet spanner makes this a doddle.

Another tip is that if you cut a slot in the bottom of the rear bolt, once loosened even a little it can then be backed out in seconds using a screwdriver.

The clamps and bolt heads stick up quite a long way which means that some saddles are not a good fit; the hull can in some instances contact the bolt heads when it flexes.

By modern standards these old campag seat pins are rather short and only fit right if you use frames with horizontal top tubes that are sized as per road bike frame sizing prior to the mid 1980s. Loony collectors have of course driven the prices through the roof in recent years; it wasn't that long ago that you could go to a bike jumble and expect to find these for £5 to £10 depending on condition. These days you are more likely to find them on e-bay with a price tag ~x5 or more as high...

Nice article on the early versions here

http://www.classiclightweights.co.uk/components/campag-seatpin-comp.html

more photos here

http://www.classicrendezvous.com/Italy/Campagnolo/campag_seatposts.htm

some for sale here

http://hilarystone.com/seatposts270268.html



cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Samuel D
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Re: Two-bolt seatpost designs

Postby Samuel D » 24 Apr 2018, 1:10pm

Nice links, Brucey.

I can’t get over how clever many of the original Campagnolo components were. The concepts were highly creative and the engineering grunt-work (implementation of the ideas) has stood the test of time with few failures. That company was in a league of its own, a bit like Shimano in its glory days of the late 80s and 90s.

I can see that accessing the bolt heads would be difficult, the difficulty varying with the saddle and setback. Your technique for adjusting the harder-to-reach bolt with your fingers sounds sensible.

Other than that, this clamp design seems outright superior to all others I’ve used. Surely every cyclist has suffered the nuisance of trying to make small adjustments to saddle tilt or trying to adjust setback and accidentally changing the tilt. This design eliminates the vagueness and frustration.

The third photo of the Nitto S83 on SJS Cycles suggests – with our certain knowledge that the lower jaw must pivot – that its clamp does indeed have the benefits of the Campagnolo design without the access problem. Tempting! I might need the S84 for setback, but it’s steel and very expensive.

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foxyrider
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Re: Two-bolt seatpost designs

Postby foxyrider » 24 Apr 2018, 4:12pm

I at least did have, the Campy spanner! Not sure where it is now mind.
I have a reverse version (ie ak heads underneath) on my best and folding touring bikes, not Campag but a Ti concoction that has seen, in one case, over a decade of trouble free riding without so much as a blemish. The micro adjustment certainly does make setting saddles very easy.
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

Randy_Butternubs
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Re: Two-bolt seatpost designs

Postby Randy_Butternubs » 24 Apr 2018, 4:25pm

I have a Deda Elementi RS01 seatpost that works in a similar way. Adjustment is done with allen keys from beneath.

Image

Instead of the screws threading into rotating collars, the top clamp angle is kept the same but they are rounded where they meet the saddle rails to allow for the different angles. The bottom clamp is not on a pivot but is free floating in its channel.

Angle adjustment is very fine but it does have a couple of downsides:

- Because the top clamps are rounded where they bear on the saddle rails they will exert greater pressure for a given clamping force. If I were using carbon rails I would be a bit concerned about crushing them. Actually, I'm a bit concerned even with steel rails. Saddle clamps generally have proven to be the thing most likely to come loose on a bicycle for me unless I do them up really tight.

- Installing/removing the saddle is a little awkward with the two independant top clamps spinning around. The bottom clamp also likes to be awkward.

- When you tighten the top clamps down they tend to rotate a bit since they aren't attached together. This means they tend to clamp down a bit skewed and quickly loosen up during riding. You need to give them a good wiggling as you tighten them down, then do a check/re-tighten after a mile or two. This problem is partly due to the small contact area due to the rounding on the top clamps.

The Campy design looks like it avoids all these negatives except for the fact that you need a spanner to adjust it. It also looks vastly more expensive.
Last edited by Randy_Butternubs on 24 Apr 2018, 4:54pm, edited 1 time in total.

Samuel D
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Re: Two-bolt seatpost designs

Postby Samuel D » 24 Apr 2018, 4:45pm

I note that those three downsides of the Deda would not be present with the Nitto S83.

Randy_Butternubs
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Re: Two-bolt seatpost designs

Postby Randy_Butternubs » 24 Apr 2018, 4:52pm

Samuel D wrote:I note that those three downsides of the Deda would not be present with the Nitto S83.


Yes! I was almost going to add that having rotating collars in the top clamps rather than at the bottom would give the best of both and it looks like that's exactly what they've done. It does cost two or three times as much as the Deda post but I'm pretty tempted.
Last edited by Randy_Butternubs on 24 Apr 2018, 4:58pm, edited 1 time in total.

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fausto99
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Re: Two-bolt seatpost designs

Postby fausto99 » 24 Apr 2018, 4:54pm

I bought this one, 3 or 4 years ago.
Image
It allows me to have the saddle further forward because my thighs are relatively short. It is very easy to adjust the up/down nose attitude.
I can't remember the make though and I haven't found the receipt so far...

ANTONISH
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Re: Two-bolt seatpost designs

Postby ANTONISH » 26 Apr 2018, 8:32am

I have three of these original campag seat posts.
I've had one of them since the early sixties. I've never found anything better - certainly not the single bolt so called "micro adjust " type.
As I've been using cut out saddles for some years access for adjustment isn't a problem.

Samuel D
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Re: Two-bolt seatpost designs

Postby Samuel D » 26 Apr 2018, 9:16am

Even if there is an access problem with some saddles, I’d gladly accept that in return for the precise, sure adjustment offered by this design. Adjusting the saddle is an infrequent job, but it is frustrating with most clamps because setting the tilt angle cannot be precisely set on the first go. It’s often a case of loosening the bolt(s), giving the saddle a thwack to break the stiction, fiddling again, tightening up the bolt(s) while watching the saddle angle change, trying again, etc.

I was planning to get Planet X’s Holdsworth Gran Sport seatpost for its setback, but when they finally got that in stock again a couple of weeks ago, they raised the price to €38. That annoyed me and anyway the clamp design has the usual problems.

After measuring photographs in Photoshop, I estimate the Nitto S83 would give me 7–8 mm more setback than my Ritchey Classic 2-bolt seatpost. That may be enough for me.

Brucey
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Re: Two-bolt seatpost designs

Postby Brucey » 26 Apr 2018, 11:49am

I agree that we owe Campagnolo a lot because they pioneered a lot of good designs and provided a benchmark for others to aim at in many cases. I note that the super record seat pin uses a plain wedge arrangement and that has been copied into the many hockey-stick designs that are on the market today. The flaw (for racing) in this design is that should the saddle come loose, you cannot continue; the saddle moves around uncontrollably. By contrast serrated ones give some warning of looseness before they slip, enough that the usual (for racing) bolt-checking should pick it up. Thus the plain wedge suits touring better than racing and the serrated design suits racing better than touring, arguably.

Concerning other two bolt designs;

- I have seen them with bolts as small as M5 (using Gr 14.9 bolts! :shock: :shock: ) in an attempt to save weight. These are not always reliable....

- The design seen above in Fausto's picture has the advantage of simplicity but suffers from poor execution in some cases (using materials that bend/crack too easily) and commonly you cannot get a normal allen key (let alone a multitool) onto the front bolt, because it is angled to the seat pin. This means adjusting as per my suggestion for the campag NR/GS design, even though both bolts appear to be accessible. If the front bolt does not have a knurled head or binds this is still awkward. I have known folks carry a ball-ended key or one that has been cut very short after the 90 degree bend so that they can adjust such seat pins.

- it is difficult to design a (straight) two-bolt pin with an accessible front bolt that has a decent amount of layback; the top clamp needs to be a funny shape to do this, and that makes the design weak/heavy/liable to foul the saddle hull. One design that has some merit is to have (at the front of the seat pin) a captive thumbwheel nut on the front bolt (which is otherwise well- hidden in line with the seat pin). Having loosened the more accessible rear bolt, the front thumbwheel is used to adjust the tilt before the rear is retightened. This is quite a good design but it still doesn't permit much layback.

BTW one seat pin design that I think is underrated is one that was first made by simplex and then (later) copied by SR. In this there are two short M8 coach bolts that clamp the saddle rails sideways, in clamps that adjust on a quadrant, i.e. the fronts are pivoted and the bolts slide in (shorter than-) quadrant slots.

Image

The saddle can usually only be adjusted using a 13mm (IIRC) open ended spanner. The special nuts have captive washers that work a bit like Belleville washers. This design is infinitely adjustable and very strong. I have only ever seen it used on fairly short seat pins though. I have often thought that (esp if the nuts are reduced in width slightly) a very slim bi-hex spanner, made from pressed steel, would do as something to carry when touring. I've never actually seen this design loosen in service, though.

cheers
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amediasatex
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Re: Two-bolt seatpost designs

Postby amediasatex » 26 Apr 2018, 12:10pm

Brucey wrote:BTW one seat pin design that I think is underrated is one that was first made by simplex and then (later) copied by SR.


I'm a big fan of those SR P3 (and the various other Raleigh etc. branded versions) posts when used on old horizontal TT frames that don't need loads of post sticking out.

The clamps are very reliable IME and although fiddly to adjust the first time they stay put and do offer plenty of adjustment. They also have a bout 30mm of setback which makes them useful for fitting Brooks/Other leather saddles to frames with slightly steeper seat tubes.

I've never actually seen this design loosen in service, though.


Unless my memory is failing me there is a slight angle on the outer face of the post and inner face of the clamps that means any downward loads in service on the saddle rails will actually act to 'wedge' the clamp even tighter, so unless the nuts were not at all tight to begin with the clamp is highly unlikely to ever loosen in service.

The new version of the Velo Orange Grand Cru/Holdsworth post, the one with this clamp:

Image

is nowhere near as easy to adjust (nor as strong) as the old version with this clamp:

Image

The new version also suffers in that the setback actually varies as you adjust the angle which means you may not get as much setback as you hoped, the old one was much better in every regard :?

I've got one of the Nitto S84 lugged posts and apart from weighing as much as a small moon it's a very good post, easy to adjust and secure.

There are some very good modern posts out there, but lots more that look like they're going to be good, but then fail in execution on one tiny aspect which makes them either a faff or weaker than they could be...

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fausto99
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Re: Two-bolt seatpost designs

Postby fausto99 » 26 Apr 2018, 12:47pm

fausto99 wrote:I can't remember the make though and I haven't found the receipt so far...


I think I've found it, a Gub 27.2mm Seat Post - Silver CNC : https://www.santafixie.co.uk/gub-seatpo ... JefvD_BwE# The name GUB still doesn't ring a bell, but maybe they bought out the original company. I knew I hadn't paid silly money for it. ~£15 is about right for a seatpost in my book.
It is very easily adjusted with a bog standard "L" shaped allen key (without the little bag in the way, of course).

Brucey
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Re: Two-bolt seatpost designs

Postby Brucey » 26 Apr 2018, 4:21pm

amediasatex wrote: ....Unless my memory is failing me there is a slight angle on the outer face of the post and inner face of the clamps that means any downward loads in service on the saddle rails will actually act to 'wedge' the clamp even tighter, so unless the nuts were not at all tight to begin with the clamp is highly unlikely to ever loosen in service....


just brandished my verniers at one and I couldn't find any trace of a wedge shape. Maybe they are not all the same.

cheers
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amediasatex
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Re: Two-bolt seatpost designs

Postby amediasatex » 26 Apr 2018, 4:29pm

Brucey wrote:
amediasatex wrote:just brandished my verniers at one and I couldn't find any trace of a wedge shape. Maybe they are not all the same.

cheers


Could be there are different versions... of course It's entirely possible I am mis-remembering or have confused them with another post of similar design :lol:

I'll try and remember to check when I get home as I'm curious now...