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Old 10-22-06, 02:23 PM   #1
ppc
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Shortening a spoke

Hello everybody,

Here's my problem : a friend of mine rides on a 20" wheeled recumbent. The rear wheel is strangely laced and uses custom-made spokes with a special lengths. He broke a spoke this week-end and wasn't able to get a replacement at the LBS. Unfortunately, he needs his bike to commute, and asked me if I knew how to make a replacement spoke in a hurry.

Since I don't have a thread rolling machine, I thought about shortening a standard spoke at the elbow end, then forge a new elbow and swaged end. Of course, that would require heating the spoke and therefore removing any heat treatment it might have received.

So my question is this: does anybody know exactly what kind of heat treatment spokes receive ? I assume the metal needs quenching then annealing and/or stress-relieving, but I don't know the exact tempering temperatures for stainless steel, and I don't know if this would work for cold-drawn steel, or even if spokes need any heat treatment at all.
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Old 10-22-06, 02:27 PM   #2
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No bike shops around you have a spoke cutting and threading machine? I'd check that first thing Monday. In the meantime though, true up the wheel best you can (you should be able to get it pretty straight despite a missing spoke unless it's a really low spoke count wheel.)
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Old 10-22-06, 02:36 PM   #3
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Quote:
Originally Posted by gwhunt23
No bike shops around you have a spoke cutting and threading machine? I'd check that first thing Monday.
That's what I told him to do yesterday. He went to all our LBSes in our area, a grand total of 3 in a 20 mile radius, but no luck. Bike shops around here aren't much good besides selling new bikes and doing simple repairs.

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Originally Posted by gwhunt23
In the meantime though, true up the wheel best you can (you should be able to get it pretty straight despite a missing spoke unless it's a really low spoke count wheel.)
I'm not too worried about the wheel, but he's not too light and his commute route is a nasty tooth-rattling paved road that makes Paris-Roubaix look like a walk in the park.
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Old 10-22-06, 02:38 PM   #4
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I might try this as an experiment, but I wouldn't send someone riding off on it and call it "repaired." Call around and see if you can't find a shop with a spoke cutter/threader. Also call all the shops that do a lot of BMX business, they're likely to have a lot more of the shorter spokes that 20" wheels take.
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Old 10-22-06, 02:39 PM   #5
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Also, post up where you are, you never know who's hiding under a rock near you.
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Old 10-22-06, 03:13 PM   #6
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I'd try wheelbuilder.com. If you need a goofy spoke he might have it or be able to make it. Once you add on the shipping, however, it isn't going to be cheap.
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Old 10-23-06, 04:31 PM   #7
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Here's a good temporary repair so your buddy can commute until you can get a correct-length spoke.

Get a spoke that's too long, and cut the elbow off. Figure out how long it needs to be, and make a Z bend where the new elbow should be. To do this, make one 90 deg bend a few MM from the length, then another right at the length. The "at length" bend is there to emulate the elbow itself, allowing the spoke to pass through the hub. The other bend emulates the flared end of a real spoke, keeping the elbow from slipping out. If you're having trouble visualizing what I'm talking about, go to a hobby shop that deals in R/C stuff and ask them about a Z bend. People use them to connect servos to other controls on R/C stuff all the time. They even sell special pliers to kink wire into the Z bend shape.

The best part about this sort of temporary spoke is that you can thread it in without disassembling the wheel at all. You can re-use the existing nipple without removing the tire, and you can simply wiggle the Z-bend into the hub. Here's a photo of what the Z bend should look like:

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Old 10-23-06, 06:06 PM   #8
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Maybe Phil Wood knows who has his spoke cutting machine in your area.

If you are going to cut the elbow off a spoke, I would not use a butted spoke. Perhaps obvious.
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Old 10-24-06, 10:44 AM   #9
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[QUOTE=SaabFan]Here's a good temporary repair so your buddy can commute until you can get a correct-length spoke.

Get a spoke that's too long, and cut the elbow off. Figure out how long it needs to be, and make a Z bend where the new elbow should be. To do this, make one 90 deg bend a few MM from the length, then another right at the length. The "at length" bend is there to emulate the elbow itself, allowing the spoke to pass through the hub. The other bend emulates the flared end of a real spoke, keeping the elbow from slipping out. If you're having trouble visualizing what I'm talking about, go to a hobby shop that deals in R/C stuff and ask them about a Z bend. People use them to connect servos to other controls on R/C stuff all the time. They even sell special pliers to kink wire into the Z bend shape.

The best part about this sort of temporary spoke is that you can thread it in without disassembling the wheel at all. You can re-use the existing nipple without removing the tire, and you can simply wiggle the Z-bend into the hub.[QUOTE]

Excellent suggestion. The Z-bend spoke modification was used as long ago as the mid-'70s by savvy BikeCentennial cross-country tourists, who often carried the modified spokes by shoving them into their handlebars, knowing that a few more bends wouldn't hurt. I've never heard of a Z-bend spoke failing at the hub.
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Old 10-24-06, 11:41 AM   #10
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The trick with a Z bend is getting it crisp enough. If you don't, it'll be sloppy enough to fatigue and break in no time flat. That's why the special pliers come in handy, they make a really nice, tight bend.
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Old 10-26-06, 11:33 PM   #11
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SABfan's response is obviously from a guy who has been around awhile. Nicely done, SABfan.

The bike essentially hangs from the rims rather than being lifted. So it is also quite possible to use a long spoke, thread it through the hub eyelit, and bend it around like a hook. It is a bit tricky to do this and get the length right, but it can be done.

I have done this and enjoyed thousands of miles out of the cobbed spoke without incident.
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Old 10-26-06, 11:45 PM   #12
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Go to store and buy a fiberfix kevlar spoke ~ $15.
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Old 10-27-06, 10:38 AM   #13
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See if you can find a small engineering work shop or a garage or friend with lotts of tool simlar that may have a small enough die to cut threads down a long spoke.
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Old 10-27-06, 11:08 AM   #14
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Hozan makes a threading tool for about $100 and you can cut the spokes with a dremel.

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