Originally Posted by
KC8QVO
In some cases, not all, there are holes that allow you to see wall thicknesses. These holes are used to for pressure equalization when welding. If you cap off both ends of a tube or pipe, when you go to weld the last cap the pressure change between inside the pipe/tube and outside will deform the weld bead/pool. I did exactly this a couple weeks ago - capped off tubes. They were real small (3/8" OD, around 1/4" ID) and I "spot welded" around the tubes to build up the material to close the ends. The weld pushed out - I assume from the hot tube causing the air inside to heat up and expand as I welded = higher pressure inside than outside until the part cooled.
In any event, holes in parts will alleviate the pressure differential. So if there are holes in the tubes, especially - you can find the wall thickness from that hole.
On my Disk Trucker I noticed the rear dropouts had holes that opened up inside the stays. This wouldn't give you the stay tube thickness, as the hole is in the dropout, but is an example of such a hole existing.
The vent holes in the tubing won’t let you measure the thickness of the tubing. How are you going to measure it?
Originally Posted by
saddlesores
superpowers required? now that's just silly.
we're not talkin' 'bout metal foundries or boiler making plants y'know. these are common shops you'll find in the hundreds in modest sized cities, in the dozens in small towns, and shirley at least one in a village of more than 500 inmates.
ya walks into a local shop that specializes in thin-wall steel tubing, you marvel at the 10-meter long floor-to-ceiling display of available tubing stock, you mosey into the back and chat with the workers who spend years.......10 hours a day, 30 days a month, cutting and shaping and welding thin steel tubes into all sorts of household and shop items.
what? you think they've never seen a bicycle before? you think they're not clever enough to remove the seatpost to check the wall thickness of the seattube?
jinkies! i'll bet you a steaming hot bowl of dog-noodle soup the average worker could dink the frame with his fingernail and estimate within a couple hundredths of a millymeter the tubing wall thickness.
You are missing the point. Most people…both the bike rider and a welder doing the repair…are unaware of how thin steel bicycle tubing is. People who are going to get a bike repaired in the middle of nowhere aren’t going to have a shop that specializes in thin tube, even if the bike owner knew that the bike
uses thin tubing. The most common type of welding is going to be on those boiler parts (or tractor parts or car parts etc.) The welders doing the welding are going to be used to thicker parts and proceed accordingly
unless the bicycle owner warns them first or they have prior knowledge of bicycles. If the welder isn’t warned, they are likely to treat the bike as if it were a piece of pipe with 1/4” (6mm) wall. The broken tube is more likely to end up as a pile of rust than repaired.