|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
cheap seatpost replacement options - 20.5mm
Picked up a clunker 10speed for small commutes. Since it cost $10, don' want to invest much at all in it or put anything on it that woul attract attention. The seatpost is, as usual, the limiting factor being about 8" long It's the style the seatpost clamp (bolted to the seat chassis (n rails)) bolts onto a still straight tube. This straight tube is 20.5m (13/16) outter diameter at the frame and gets slightly larger (t 22.0mm) to attach to the clamp, and has no bends. Wall thickness i roughly 1.6mm. What's a typical cheap replacement or solution in this situation? ie raw pipe lengths. Rust resistance isn't an issue. I could even weld pipe to bring the seat to where I need it. Future adjustability isn' an issue. 'Was thinking that a galvanized conduit or gas pipe might be a adequate replacement, and I could shim the smaller size to fit it t the seatpost bolt. Intermediate Metal Conduit (IMC) is available in O 20.7mm thickness 1.8mm. But, what method is used to determine if this is safe/adequate? Wha formula might be used that gives minimum wall thickness (for a give material) as a function of material type, exposed seatpost length, an outter diameter? Searching for cheap seatpost replacements before, I never foun anything less than around $10 at normal retail price. Nashbar becam the exception with their sale recently on house brand items where the sold their posts in various diameters at around $6. But 20.5mm seems a oddball size. I also have curiosity in doing this in the future i trying to restore these clunker bikes for small distance commuters Seatpost length often seems to be the limiting factor for talle people. Would also be interested in hearing other things you guys do to take clunker commuter bike and improve it, without investing much ($20 is lot), and without making it look more attractive. The idea behind thi "class" of bike is to have something that can be stolen or locking i up remotely for infrequent use -- jasong |
Ads |
#2
|
|||
|
|||
cheap seatpost replacement options - 20.5mm
I like your thinking here.
The fact that you are concerned about the strength of "galvanized conduit or gas pipe as an adequate replacement" makes a lot of sense but this material is, in fact, a good idea for what you are trying to do. The limiting factors are that the rider is not extremely heavy, or using an extremely long post. Sometimes I have found electrical conduit that will fit a seat tube but it has a much thinner wall than gas or water pipe and is only suitable for a short seatpost. Lewis. ***************** |
#3
|
|||
|
|||
cheap seatpost replacement options - 20.5mm
wrote in message oups.com... I like your thinking here. The fact that you are concerned about the strength of "galvanized conduit or gas pipe as an adequate replacement" makes a lot of sense but this material is, in fact, a good idea for what you are trying to do. The limiting factors are that the rider is not extremely heavy, or using an extremely long post. Sometimes I have found electrical conduit that will fit a seat tube but it has a much thinner wall than gas or water pipe and is only suitable for a short seatpost. Lewis. I like your thinking?? Compromise your safety for a lousy 10 dollar seems not so smart to me. You want to go safe? Take a solid rod and make in fit on a lathe. It will be on the heavy side though.. Lou |
#4
|
|||
|
|||
cheap seatpost replacement options - 20.5mm
Lou Holtman Wrote: wrote in message I like your thinking?? Compromise your safety for a lousy 10 dolla seems not so smart to me. You want to go safe? Take a solid rod and make i fit on a lathe. It will be on the heavy side though.. Lou, you may have missed the part of my post asking for a means fo determining how to do this safely. It wasn't implied that a arbitrarily tough item be stuck in the hole and secured and wishfu thinking maintained during the rides. Though I think that this could b assumed for the constrained case of a very small post extension (whic won't be the case for me, I need some 30cm sticking out of the frame which was what the poster had suggested. Shear forces on something tha small, to result in destructive failure, would be very difficult t reproduce in the context. Not even the idea of turning a solid rod down to this diameter is convincing enough argument to be safe. Maybe the post that came wit the bike isn't safe. The intent was to motivate the stress/strain equations tha manufacturers rely on to spec these parts out, placing severa variables in a function and seeing what wall thickness pops out. I'v got a post pending the frameforum as well -- jasong |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Autofaq now on faster server | Simon Brooke | UK | 216 | April 1st 05 10:09 AM |
Spoke Prep - cheap replacement | Joshua Lee | Techniques | 41 | December 12th 04 09:21 PM |
How best to improve a cheap bike? | Pyromancer | UK | 11 | May 21st 04 02:56 PM |
Cheap 28.6 x 350 Seatpost Wanted | John Latter | UK | 12 | April 18th 04 03:50 PM |
OAKLEY M-FRAME REPLACEMENT LENS - CHEAP!! | haddawad | Marketplace | 0 | February 20th 04 04:51 PM |