[eddie m]

I pulled a spoke through the rim this week. I'd like to rebuild the wheel but I can't find a paired spoke rim to use. I'm thinking of replacing it with an equal spaced rim.
What I want to do is lace one side conventional 2 cross, and lace the other side with unequal length spokes, either 1 or 2 cross. I'm confident I can build a stable wheel, but I'm not sure how to go about calculating the spoke lengths. I don't want to write my own spoke length calculator. I'm hoping to find a calculator I can modify, or maybe I'll just lay it out on paper and and do it graphically. (I'm an old engineer, so I know how to do drawing.)
Any other ideas?

em

 

[Marc]

Call the manufacturer and source an (overpriced) replacement. The hubs you have are designed for paired spoking...and using a standard rim may or may not result in you meeting the pavement at high speed in a most painful and spectacular manner.

 

[eddie m]

My first choice was an exact replacement rim, but I can't find one at any price.
I'm not worried about the reliability of the thing. An equally spaced wheel is stronger than a paired spoke wheel, all else equal. You can build a 24 spoke wheels with a 32 hole hub and it will work fine. I'm just looking for an easy way to compute spoke lengths. The first problem is too accurately measure the offset of the paired spokes. Then it's just a lot of calculating, which I hope someone as already done and wants to share.
Maybe the best solution is to build it with the old drive side spokes, then lace the other side radially with shortened the non-drive spokes

em

 

[4slomo]

You can use a spoke calculator to figure out lengths at various crossings. So if you want to have the leading spokes x1, plug in that and calculate lengths. Likewise with trailing spokes x2.

I pulled a spoke through the rim this week. I'd like to rebuild the wheel but I can't find a paired spoke rim to use. I'm thinking of replacing it with an equal spaced rim.
What I want to do is lace one side conventional 2 cross, and lace the other side with unequal length spokes, either 1 or 2 cross. I'm confident I can build a stable wheel, but I'm not sure how to go about calculating the spoke lengths. I don't want to write my own spoke length calculator. I'm hoping to find a calculator I can modify, or maybe I'll just lay it out on paper and and do it graphically. (I'm an old engineer, so I know how to do drawing.)
Any other ideas?

em

 

[eddie m]

You can use a spoke calculator to figure out lengths at various crossings. So if you want to have the leading spokes x1, plug in that and calculate lengths. Likewise with trailing spokes x2.

That's not the issue. My hub is drilled for paired spokes, so the holes are not offset from left to right. Maybe if I can find a spoke calculator that accepts fractional crosses I can calculate the lengths I need by using 1.5 and 0.5 crosses.
I'm tempted to just lay this all out on a drawing board, but that will have to wait until January.

em

 

[Andreas_Illesch]

I'm tempted to just lay this all out on a drawing board, but that will have to wait until January.

No CAD software around for an old engineer?
I get all my spoke lenghts from there.

 

[eddie m]

No CAD software around for an old engineer?
I get all my spoke lenghts from there.

I haven't had any use for CAD in a long time.

You and I have different definitioins for "old". When I was in school, CAD was new but we stil used a lot of paper.

em, PE

 

[Mr Evil]

...Maybe if I can find a spoke calculator that accepts fractional crosses...

Spocalc can do that.

 

[Andreas_Illesch]

I haven't had any use for CAD in a long time.

You and I have different definitioins for "old". When I was in school, CAD was new but we stil used a lot of paper.

em, PE

If you don't find a suitable spoke calculator you can give me the specs and I draw it for you if you like.

 

[eddie m]

If you don't find a suitable spoke calculator you can give me the specs and I draw it for you if you like.

Thank you. That' s very generous.
I think I can use spocalc with fractional crosses. The next step is to estimate the torque across the hub caused by the assymetric lacing. The hub section is about 5/8 of an inch, so I don't want to leave a lot of static torque there.
I've already bought a replacement wheel, so this is going to be a winter project. It's a little of a fool's project because it's a heavy hub, and I want to do it on the cheap, which means cutting down the old spokes, which are also too heavy for the wheel I want.

em

 

[gjk]

Hi, I am considering the same project. I have a Bont Race lite hub circa 2008. It has straight pull non drive side spokes that must be laced radially. My calculations indicate I can lace the drive side 2X with constant spoke length. 2X will allow the spokes to pull outward from the dual spoke slots. I also found spoke calc would calculate fractional patterns. My LBS is willing to swap out spokes I buy from stock if I miscalculate. Have you finished your calculations and build? I would very much like to compare notes and experience.

 

[eddie m]

Hi, I am considering the same project. I have a Bont Race lite hub circa 2008. It has straight pull non drive side spokes that must be laced radially. My calculations indicate I can lace the drive side 2X with constant spoke length. 2X will allow the spokes to pull outward from the dual spoke slots. I also found spoke calc would calculate fractional patterns. My LBS is willing to swap out spokes I buy from stock if I miscalculate. Have you finished your calculations and build? I would very much like to compare notes and experience.

I changed the requirements for this project. I decided the hub wasn't worth saving if I had to buy a new rim and spokes, so I decided to build it with the broken rim. I'll reverse the rim so that all the drive side spokes have solid connections, and either reinforce the cracked spoke hole or drill a new hole in the rim or just use 27 spokes. If I drill a new hole at least one spoke will be in the right place.
I don't have much hope for this wheel, but maybe I'll have a spare wheel that will last a couple of hundred miles if I ever break another wheel again. If not, at least I'll learn something.

em

 

[looigi]

I haven't had any use for CAD in a long time...

Must it be CAD? What about a little trig and a calculator? Heck, even a slide rule? Excel works too.

 

[eddie m]

Must it be CAD? What about a little trig and a calculator? Heck, even a slide rule? Excel works too.

Someone else brought up CAD, which would work fine but is not part of my skill set. A simple spoke calculater doesn't work because I'm trying to lace up a pattern that no one would do if they weren't pathologically cheap. The simplest answer for me would be to draw it out in 2 dimensions at full scale, then adjust the lengths to account for the flange offset. The adjustments I would need to make to a spoke length calculator would be more difficult than drawing the whole thing. But now I've decided just to build it up with just 27 spokes and see if I can get a usable wheel to keep as a spare.

em

 

[eddie m]

I finally got back to this. I think I've got a usable wheel now.
The original failure was a drive side spoke that pulled through the rim. I removed the paired non-drive side spoke and laced the drive side to the undamaged hole. Then I went to the pair of spokes adjacent to the failed pair and swapped the drive side spoke to the non-drive side hole, and vice versa. That minimizes the lateral bending moments to make the wheel easier to true with a missing spoke. I trued it to 50 thousands radial and lateral, which is not very good, but it's usable. The tension seems pretty good, and it has good lateral stiffness.
Obviously, this is not a perfect wheel, but I'm confident I can ride it safely. All the spokes are in undamaged grommets, and the maximum span between spokes is only about 20% more than original, and about the same as the span in the 24 spoke front wheel, which has the same rim section. It has a little too much hop, but I can't take that out without increasing the lateral runout, and this wheel needs to go in a very narrow frame.
The only purpose for doing this was to have a spare wheel so that I don't need to go a week or two if I break another wheel, but I won't call it a success until I test ride.

em

 

[samh]

I finally got back to this. I think I've got a usable wheel now.
The original failure was a drive side spoke that pulled through the rim. I

What causes this? Too hi tension? Do you know if Campy G3 wheels can be "trued"? I wouldn't go through this trouble, you can buy/build cheap old school wheel.

 

[eddie m]

What causes this? Too hi tension? Do you know if Campy G3 wheels can be "trued"? I wouldn't go through this trouble, you can buy/build cheap old school wheel.

It looks like a fatigue failure of the rim at one of the drive side spoke holes. I would have expected fatigue at the non-drive side, but that's not what happened. I don't know the cause. Probably the attachment points just aren't strong enough. The wheel only had maybe 5000 or 10000 miles on it. I assume Campy wheels can be trued, but you probably need a $$$$ Campy tool for it.
This was more an experiment than anything else. I like doing stuff that takes my mind off my work for a few minutes. I hope I never need to use this wheel, but I'll keep it as a spare if the replacement wheel ever breaks. I'm definitely not afraid to ride it. It should be almost as strong as ever, as strong as the matching front wheel, and only a little more flexible than before the failure. OTOH I'm probably going to start seeing fatigue cracks all over that rim if I ride it much.

em