What size is my seat post??????????

[The History Man]

HI, rebuilding/restoring a 1953 Arnstrong and need a new seat post. The problem is that I can't be sure of the size of the old one as it varies as it's been crushed.. I make it a consistent 27.2 when rotated up by the seat bracket fixing and about 27 ish further down. What should i go for?

Thanks THM

viewtopic.php?f=23&t=259880

 

[GuyWood]

See if a LBS has a cheapy in each size you could try sticking down the seat stay?

 

[The History Man]

Nice idea.

Would 0.2 be too much for the clamp to cope with if i bought a 27.0 and it should be 27.2

 

[keithglos]

I sold a number of really special Armstrongs in the mid 50's, silver brazed, nervex pro etc., built by Bill Gameson when Dave Duffield was running it. These were all butted tubing, so 27.2. The earlier Moth models, some were produced with butted tubing, so difficult to tell. if the seat post is small you can risk splitting the tube when tightened, downwards from the back of the lug. Depending on the requirements of the build you can possibly shim it if the post is too small.

 

[The History Man]

I sold a number of really special Armstrongs in the mid 50's, silver brazed, nervex pro etc., built by Bill Gameson when Dave Duffield was running it. These were all butted tubing, so 27.2. The earlier Moth models, some were produced with butted tubing, so difficult to tell. if the seat post is small you can risk splitting the tube when tightened, downwards from the back of the lug. Depending on the requirements of the build you can possibly shim it if the post is too small.

Hi and thanks, Did you look at my pics? Is there anything I can look at or provide to narrow it down? (forgive the terrible pun)

 

[keithglos]

I missed the other thread, but recognised the parts immediately. If the parts are original I would see it slightly later. I used the earlier Benelux (bendylux)gears in 1950 with their not too good handlebar controls and could always change both at once off the saddle up hill. By a bit of bending I could make then do 6 speed. Also adjustment by bending helped to get the extreme gears. Wet weather would get to them a bit, and could be damaged by hitting the road, but the accuracy of gear change was far superior to the early Campagnolo GS.
Weinmann Alesa alloy 27 x 1 1/4 rims were the standard for general use at 18 ounces each, but always had a problem with the near vertical spokes on the gear side.
I used to get frames with Nervex crowns like the chrome one in the picture, and built to spec for the same price, sliver brazed as well. Mostly they made standard Moth frames, which yours looks like.
Keith

 

[The History Man]

I missed the other thread, but recognised the parts immediately. If the parts are original I would see it slightly later. I used the earlier Benelux (bendylux)gears in 1950 with their not too good handlebar controls and could always change both at once off the saddle up hill. By a bit of bending I could make then do 6 speed. Also adjustment by bending helped to get the extreme gears. Wet weather would get to them a bit, and could be damaged by hitting the road, but the accuracy of gear change was far superior to the early Campagnolo GS.
Weinmann Alesa alloy 27 x 1 1/4 rims were the standard for general use at 18 ounces each, but always had a problem with the near vertical spokes on the gear side.
I used to get frames with Nervex crowns like the chrome one in the picture, and built to spec for the same price, sliver brazed as well. Mostly they made standard Moth frames, which yours looks like.
Keith

So based on your assessment re Moth, 27.2?

Much appreciated

 

[keithglos]

Butted 531 was usually 20 / 23 g in those days, equivalent to 27.2 mm
The 20G would be probably be up 6 to 8 inches from the bottom bracket.

 

[The History Man]

I'm sorry could you translate that into idiot? thanks

I think you mean that I have at least 12 inches of 27.2 seat tube ?

 

[keithglos]

I am still in imperial measurements. The seat tube is 1 1/8 inches outside diameter, less the thickness of 23 gauge twice, allow for the clearance and it should equal 27.2mm. I could look through my books to convert 23G to metric. Approximately 28.575mm outside, tube thickness x 2 is 1.27 mm, leaves approx 0.1mm clearance.
I hope it fits after this.
And I hope the 531 transfer is correct.
Keith