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Can This Seatpost Be Saved?

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Can This Seatpost Be Saved?

Old 08-27-21, 12:17 PM
  #1  
jdave5917
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Can This Seatpost Be Saved?

I realize there is nothing special about the post, but it is original to the bike (1987 Schwinn Tempo - second photo) so I'd prefer to keep them together. Wondering if there is a safe/durable method of reattaching the clamp assembly to the post. Both mating surfaces are clean and smooth so I assume it was just a friction/compression fit, but not sure. I've thought of epoxy but believe the mating surfaces would have to be scuffed first to give that a chance of working. An alternate approach that I've considered is to drill a hole (maybe 1/8") to insert a pin in and then smooth and peen the edges of the pin to prevent it from moving. I think(??) that should be a reliable (if inelegant) approach. I'm thinking that the primary sheer forces would in the vertical direction and counteracted by the saddle mount bottoming out at the opening of the tube, so a failure due to those forces seems unlikely. Just a home mechanic here with my own bike, so not the usual shop liability concerns. Regardless, I will likely let go of it sooner rather than later, so I don't want to knowingly put another rider at risk.
Thoughts/suggestions/methods that have worked for you?

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Old 08-27-21, 12:50 PM
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@jdave5917

Most/all here would be a hard NO on this I think.

That being said, imo the pin and peen may work short term but not with out a back stop of epoxy/JB weld and still be very tenuous at best.

AND, do not pass it on, period.
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Old 08-27-21, 12:58 PM
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Were the post particularly rare or hard to get, I might be willing to give repair a shot. But, since it is not, then in my mind it is not worth the effort to repair nor is it worth taking a chance with one's safety by riding it. But that is just an old man's opinion and we all know what Mrs. Me thinks of that!-(
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Old 08-27-21, 01:03 PM
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That's a failure mode I would never want to experience. I would replace, and if keeping it original has sentimental value, just keep it and reinstall if it ever becomes a wall hanger. But I'd never ride that post if repaired.
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Old 08-27-21, 01:06 PM
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If it was the seat post on the E Merckx hour bike yeah maybe. But with all due respect it's just a schwinn seat post that could get someone hurt. Off to the recycle bin.
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Old 08-27-21, 01:32 PM
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Itís a Laprade seat post. You can easily find another one and nobody but you will know it wasnít original to the bike. If the bike wasnít yours from new, then perhaps itís already been replaced a time or two.
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Old 08-27-21, 02:18 PM
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Find an identical seat post and install, make the original a wall hanger..
keep them together in case you ever sell or pass it on.

everyone is satisfied!!!
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Old 08-27-21, 02:31 PM
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.

.
Still looks tall enough for several bikes I've seen here with that coveted "french fit."
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Old 08-27-21, 02:35 PM
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I had a similar seatpost off a same era Super Sport that was pinned at that joint. It had cracked at the pin.
I cut it down and repinned it with a new pin. 2 years so far so good.
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Old 08-27-21, 02:48 PM
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that is like a mtb length post...
I would cut off 3-4 cm, bbrasive clean both parts, then use a metal filled epoxy, then drill and pin it.

Actually, I would just look for an American classic or similar, So Much Lighter... That is a boat anchor.
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Old 08-27-21, 03:10 PM
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2 Piece Seat Post Failure

NONONONO! UNSAFE AT ANY SPEED!

THINK OF WHAT'S AT RISK DOWN THERE!


The pressed in, swagged or pinned 2 piece style of seatpost construction was, is and always will be a "urine" poor design. Campy made some seatposts that way during their brief MTB misadventure - and they came apart that way too!

Seatposts are one of the most highly stressed parts of a bike! They support most of a rider's weight!

While I don't recall seeing one of those 2 piece alloy seatposts with a split or break at the top of the tube section, what I suspect happens is the constant pounding from road shock expands the top of the tube at the rear enough for the upper part to come loose.

Plastic reinforced carbon fiber seat posts are made that way too and from what I've seen, that's the most common place for failure.

My suggestion: recycle the pieces at separate times or places so that some nimrod doesn't find them and attempt a repair.

You can find 1 piece SR Laprade seatposts on eBay all of the time. Hone or sand the inside of the seat tube to remove any burrs - put something down the tube to keep gunk from getting into the BB.

Lastly, coat the bottom of the seatpost and top of the seat tube with a glob of grease to avoid "HELP! MY SEATPOST IS STUCK!".



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Old 08-27-21, 05:16 PM
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Originally Posted by SurferRosa View Post
.

.
Still looks tall enough for several bikes I've seen here with that coveted "french fit."
Best reply so far!. Funny...But thought provoking.. Looking for the hacksaw.
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Old 08-27-21, 05:23 PM
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I'd be much more worried about keeping my seatpost original to my body than the Schwinn's
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Old 08-27-21, 06:34 PM
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I'll offer an alternate perspective. My Griffon has an interesting seatpost, a Campy Record with a titanium shaft:



Bob Freeman takes trashed Campy seatposts, chops off the shaft at a certain point, turns the remainder down and epoxies a new titanium shaft to the stub. I don't know how long the stub is or how tight the fit is without the glue, but I trust Bob to do the right thing. (He's made quite a few of these, with — as far as I know — no problems.) Strava tells me I have about 1500 miles on the bike, and thus the seatpost. I am out of town for the weekend, but can make some measurements next week. If your shaft was an interference fit, I rather suspect that it can be epoxied back together.
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Old 08-27-21, 07:21 PM
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Originally Posted by smontanaro View Post
I'll offer an alternate perspective. My Griffon has an interesting seatpost, a Campy Record with a titanium shaft:



Bob Freeman takes trashed Campy seatposts, chops off the shaft at a certain point, turns the remainder down and epoxies a new titanium shaft to the stub. I don't know how long the stub is or how tight the fit is without the glue, but I trust Bob to do the right thing. (He's made quite a few of these, with ó as far as I know ó no problems.) Strava tells me I have about 1500 miles on the bike, and thus the seatpost. I am out of town for the weekend, but can make some measurements next week. If your shaft was an interference fit, I rather suspect that it can be epoxied back together.
Some impressive handiwork right there!
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Old 08-27-21, 08:02 PM
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Originally Posted by smontanaro View Post
I'll offer an alternate perspective. My Griffon has an interesting seatpost, a Campy Record with a titanium shaft:



Bob Freeman takes trashed Campy seatposts, chops off the shaft at a certain point, turns the remainder down and epoxies a new titanium shaft to the stub. I don't know how long the stub is or how tight the fit is without the glue, but I trust Bob to do the right thing. (He's made quite a few of these, with ó as far as I know ó no problems.) Strava tells me I have about 1500 miles on the bike, and thus the seatpost. I am out of town for the weekend, but can make some measurements next week. If your shaft was an interference fit, I rather suspect that it can be epoxied back together.
Yeah, wow, I want to make one now!
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Old 08-27-21, 09:09 PM
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Originally Posted by verktyg View Post
NONONONO! UNSAFE AT ANY SPEED!

THINK OF WHAT'S AT RISK DOWN THERE!


The pressed in, swagged or pinned 2 piece style of seatpost construction was, is and always will be a "urine" poor design. Campy made some seatposts that way during their brief MTB misadventure - and they came apart that way too!

Seatposts are one of the most highly stressed parts of a bike! They support most of a rider's weight!

While I don't recall seeing one of those 2 piece alloy seatposts with a split or break at the top of the tube section, what I suspect happens is the constant pounding from road shock expands the top of the tube at the rear enough for the upper part to come loose.

Plastic reinforced carbon fiber seat posts are made that way too and from what I've seen, that's the most common place for failure.

My suggestion: recycle the pieces at separate times or places so that some nimrod doesn't find them and attempt a repair.

You can find 1 piece SR Laprade seatposts on eBay all of the time. Hone or sand the inside of the seat tube to remove any burrs - put something down the tube to keep gunk from getting into the BB.

Lastly, coat the bottom of the seatpost and top of the seat tube with a glob of grease to avoid "HELP! MY SEATPOST IS STUCK!".



dedhed repechage Are you guys looking to compete for the Darwin Award? "HEY! WATCH THIS!"...

verktyg
I did recí buy an alternative.
it is an interesting failure, I have seen the Campagnolo / titanium hybrids before, a reasonably sound approach with the correct adhesive.
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Old 08-27-21, 09:56 PM
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Iíve seen this seat post more than any other. They are a dime a dozen (seems like they are on every mid range Japanese bike from the 80s) and very cheaply had. I couldnít imagine bothering to attempt a repair and riding it, especially if Iím sure Iíll be moving the bike along to someone else soon enough.
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Old 08-27-21, 09:57 PM
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Know anyone that TIG welds aluminum? Easy fix.
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Old 08-27-21, 10:34 PM
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there's a lot of criticism....or was...that a steer tube for a fork that is/was either too short or busted couldn't safely be repaired/spliced. it can. the seat post could be too in much the same manner. and, it'd be safe. thing is you'll see the repair on the post whereas with the fork (that i've seen) you can't. not only is the repair hidden by submersion in the frame, but it's steel. in the video i've seen, it's shown how that was done. i doubt it could be done so nicely with aluminum, though. moreover, the fork i refer to is rare. that post is not....sentiment or not.
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Old 08-28-21, 07:40 PM
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If you really want to save it, instead of pinning it consider drill and tapping and installing a couple 5mm button head screws fore and aft, epoxy the joint and the threads too, that should hold it.

Here is a titanium replacement sleeve I press-fit and bonded to a Dura Ace seat post 15-20 years ago. it's held, although this is no longer my prime ride.
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Old 08-29-21, 01:48 AM
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Welding Cast luminum To Wrought Aluminum

Originally Posted by canopus View Post
Know anyone that TIG welds aluminum? Easy fix.
It can be done, but....

Wrought aluminum alloy 6061 is the metal most commonly used on non-cast bicycle parts. It's produced to have a very low amount of impurities thus providing uniform strength and a quality finish.

Cast aluminum alloy 356 and A356 is the most common alloy for cast parts. Large pieces like automotive castings are frequently produced using sand casting processes. Smaller or more precise parts are made with pressure casting equipment. Those parts are cast to reduce or eliminate most machining thus reducing manufacturing costs. The cast alloys were never formulated to be welded.

The Japanese euphemistically called this "melt forging" !!!

6061 and 356/A356 alloys have similar properties and chemical make up but wrought 6061 is generally about 10%-15% stronger.

Cast aluminum products can be made of high quality "virgin" metal but they can also contain lots of impurities which cause what could be described as microscopic bubbles in the metal. These impurities are what can make cast aluminum difficult to weld.

At 400į most aluminum looses it's heat treated strength. The metal on both sides of the weld in the HAZ (Heat Affected Zone) loose it's original heat treated strength.

Link to a 12+ minute video demonstrating welding cast aluminum. Worth watching if you are interested in learning the why's - skip to 1:27:


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Old 08-29-21, 04:32 AM
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Originally Posted by verktyg View Post
Link to a 12+ minute video demonstrating welding cast aluminum. Worth watching if you are interested in learning the why's - skip to 1:27:

https://www.youtube.com/watch?v=zvHq2YCfMp4

verktyg

"HEY! WATCH THIS!" The cry of aspiring Darwin Award Candidates!
Thanks for the video link. Will definitely watch.

As for Darwin Award candidate lingo, I believe the current term of art is, "Hold my beer..."
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Old 08-29-21, 10:58 AM
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Why even consider risking a grotesque, medieval-style impalement over an easily replaced bicycle part?

Chinese boy impaled on his seat tube after freak accident

BMX rider impaled by bike airlifted to safety in California

Although, if you google 'impaled by bicycle', it's far more common for handlebars and brake levers to be catastrophically inserted into humans.

Teen Gets 'Inverted' Scrotum and 'Degloved' Penis After Being Impaled on Bike Handlebars
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Old 08-29-21, 06:40 PM
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Vlad

Originally Posted by Vintage_Cyclist View Post
Why even considaer risking a grotesque, medieval-style impalement over an easily replaced bicycle part?

Chinese boy impaled on his seat tube after freak accident

BMX rider impaled by bike airlifted to safety in California


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