Drilling a 18h rim for 2:1 pattern (18DS : 9 NDS)

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HillRPete
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by HillRPete

I have a spare 18h alu tubular rim, that could be used for some experimentation. The thinking is to use it as a rear wheel, with a 2:1 spoke pattern (2 cross DS, radial NDS).

Common 2:1 hole counts are 16:8 for BHS hubs, and 14:7 by Fulcrum/Campy.

What I would like to do is drilling an extra hole between each other, so I'd end up with 18:9 spokes. I'm planning to use a 36h hub, and skip every second hole on the NDS.

Could anyone weigh in on this approach, are there any obvious problems?

roca rule
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by roca rule

why not get a 24h hub standard 12ds 12nds and use every other hole so you end with 12ds and 6nds. i am no expert but i would say "don't do it foo" (in a mexican gansgter accent) 18h might be pushing it unless you are a 110lb jockey.

by Weenie


rruff
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by rruff

I'm not foreseeing a problem. Lace the DS just like you would a 36h wheel. Drill 9 holes (skipping every other DS rim hole) and make sure your NDS pattern is symmetrical over those holes.

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Adrien
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by Adrien

wassertreter wrote:I have a spare 18h alu tubular rim, that could be used for some experimentation. The thinking is to use it as a rear wheel, with a 2:1 spoke pattern (2 cross DS, radial NDS).

Common 2:1 hole counts are 16:8 for BHS hubs, and 14:7 by Fulcrum/Campy.

What I would like to do is drilling an extra hole between each other, so I'd end up with 18:9 spokes. I'm planning to use a 36h hub, and skip every second hole on the NDS.

Could anyone weigh in on this approach, are there any obvious problems?


I highly advise against lacing a standard hub with so many holes into a 2 to 1 triplet rear wheel.
Because there are a lot of holes drilled into the flange, there is very few material left.
Lacing this flange with half the spokes will cause the flange to break because the spokes will be twice as tensioned as they normally are. That is OK as long as the hub is drilled specially for this. That is not OK with a normal hub, especially with so many holes.
If you want anyway to give it a try, do not lace radially the non drive side flange. The failure would happen very quickly.
You would better have to cross the spokes 1x. But even with a crossed pattern, I'm sure the hub will break soon or late.

rruff
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by rruff

Adrien wrote:You would better have to cross the spokes 1x. But even with a crossed pattern, I'm sure the hub will break soon or late.


It would probably be ok with 1x... the spokes have twice the tension they normally would, but there are half as many also... and the flange stress is much reduced with a nearly tangential spoke orientation (vs radial). Think of the extra holes as "drillium".

BUT... you can't do 1x with 9 spokes. I didn't notice that earlier. He might be able to figure out some funky cross pattern that is torsionally neutral, but he'll have to play with that one himself.

Roeboe
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by Roeboe

rruff wrote:
Adrien wrote:You would better have to cross the spokes 1x. But even with a crossed pattern, I'm sure the hub will break soon or late.


It would probably be ok with 1x... the spokes have twice the tension they normally would, but there are half as many also... and the flange stress is much reduced with a nearly tangential spoke orientation (vs radial). Think of the extra holes as "drillium".

BUT... you can't do 1x with 9 spokes. I didn't notice that earlier. He might be able to figure out some funky cross pattern that is torsionally neutral, but he'll have to play with that one himself.


I questioned myself before, isn't it possible to get hubs with custom drillings?

rruff
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by rruff

Roeboe wrote:I questioned myself before, isn't it possible to get hubs with custom drillings?


Just have 9 evenly spaced NDS holes? Might be possible for Alchemy or White Industries. But neither of those have the flange spacing that would make triplet ideal... nor any normal hub for that matter. Not sure what you are trying to achieve. If you have the parts and just what to try something different, then that is fine, but if you are going to the trouble and expense of getting custom parts built, it doesn't make sense.

HillRPete
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by HillRPete

Thanks everyone so far.

There is one more thing I should probably bring up: drilling angle. The 18h are obviously drilled slanted slightly to the DS/NDS alternatingly. If I drill the "intermediate" holes for the NDS spokes I end up with one of the 2 DS holes for each group facing NDS.

Like so:

old drilling pattern, hole slant:
ds --- nds --- ds --- nds --- ds --- nds --- ...

new pattern, new holes in capitals:
ds - NDS - nds --- ds - NDS - nds --- ds - NDS - nds --- ...

I'm planning to use the "ds" slanted holes for the "pulling" spokes then the "NDS" ones for the radial nds, and the leftover "nds" facing ones for the "non pulling" spokes on the drive side. Will I get away with that?

rruff
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by rruff

This is looking worse all the time. You should use a center drilled rim for triplet.

HillRPete
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by HillRPete

Yeah I was afraid it'd end up like this. Guess I'll look around for a Velocity Pro Elite based rear wheel to somewhat match my existing front.

Or any recommendations for other tub rims around 30mm out there? Silver preferred, and Shimano compatible (no vintage Shamal, alas).

aerogurl
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by aerogurl

Pro-Elites are readily available through Velocity in a few drillings.
http://store.velocityusa.com/products/c ... 65.93784.0
Mavic CXP30s are still around NOS but make sure you get the eyelets with them.
EAI Arrow (also labeled Wheelsmith Accelerator and Araya Super Aero SA30) are available through EAI NOS, but $$$.
http://www.euroasiaimports.com/productc ... p13912.htm
or 16/20h only for less $$$
http://www.benscycle.net/index.php?main ... _1821_1824

by Weenie


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