An important piece recently fell off of my bicycle, and I’ve been trying to find a replacement. Unfortunately, it’s far from standard: The bicycle folds in half, and the missing piece is part of the hinge assembly. I can’t even find it from the manufacturer, since they apparently varied the design of this bike a great many times, and even if they did have the right one, they don’t sell parts in any unit smaller than the entire hinge assembly, for a price higher than I’d like to pay.
But on the other hand, it’s a simple enough piece that it seems like I ought to be able to find it somewhere. It’s a hollow cylinder (like a very small pipe), 11.3 mm long, 7.2 mm outside diameter, and 4.8 mm inside diameter. It would be under significant shear strain, and so would almost certainly have to be made from hardened steel. And… that’s about it (I’d also need to get a new bolt to hold it in place, but those are standard enough that I’m not worried about it). I’ve found similar-looking products labeled as “bolt spacers”, but none of them are hardened.
Is there any place which would have something like that off-the-shelf? Alternately, is there any place which would be willing and able to custom-make one? I have plenty of contacts with the local high school career technical program, but unfortunately they don’t have a machine shop.
9/32 inch would indeed be fairly close to the outside diameter I need, but I’m not seeing any listed in that size on that page? And would stainless steel or regular steel (or even brass) be better?
Sorry, I was looking at the length, which does have 9/32.
I don’t see an OD available in that size.
You could buy the next size up, and chuck in in a drill (or lathe) and turn it down to the correct size.
Stainless would probably be slightly stronger, but they are not available in all sizes.
Steel would be better than brass. They are probably cheap enough that if one started to fatigue, you could have a spare on hand.
Are both the ID and OD critical? If you need to hold both to really close tolerances, a machine shop will work. It will also be costly.
Is the old one available for use as a pattern?
You may luck out and find that it is actually a common tubing size, so al that is needed is to cut off a tiny chunk.
If both the ID and OD need to be machined to perfectly round and smooth, the mfg’s hinge may be the best bet.
Or you could scrounge ebay for a bike good for parts…
The OD is an “at most” figure, since it has to fit into an existing hole, and the hardness of the surrounding material is beyond the practical capability of any tool I have access to.
The ID is just to accommodate the bolt that holds it in place. The bolt only needs to be able to hold its own weight and that of the cylinder, so if it’s not quite right, I could probably improvise something.
A perfectly circular cross-section isn’t necessary, just that it fit in a circular hole of that size. Though of course, a circle would give the most strength for that constraint.
The original part is not available: If it were, I’d just put it back in (it looks likely that the bolt came loose and it fell out, not that it broke). It could have fallen out anywhere on two kilometers of road, and though I did look for it, I wasn’t surprised to not find it. All dimensions are determined from the remaining enclosure.
Those roll pins look like they might work. Their wall thickness is greater than what I’m looking for, but again, that’s something that might be improvised around.
I would look at www.smallparts.com.au, if you can find the part name then you should be able to locate something similar locally,alternatively some 3/16 brass pipe might be suitable.
You might be able to find a shoulder bolt of the correct size. It’s like an ordinary bolt except it’s not threaded for a measured portion directly below the head. You’ll need to match the OD of the tube you are replacing, but there’s no ID to be concerned with, and the exact length of the unthreaded part could be longer than you need and the excess taken up with washers. It would replace the bolt and tube combination with just the bolt and it will be made of hardened steel, usually stainless.
Thanks everyone, I’ve already gotten an offer (actually two) to custom-make it, which is going to be a heck of a lot easier than finding something stock that matches all three dimensions. All of you let me know if you need help any time in the future!