Lace 32H rim with 36H hub motor

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420b   100 W

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Lace 32H rim with 36H hub motor

Post by 420b » Nov 21 2018 8:50pm

How would I go about lacing a 36H hub motor into a 32H rim? I need a way to calculate the spoke width. I have the ERD and flange diameter, but the grin spoke length calculator only takes a single spoke count. I understand that the tension would be spread out unevenly because the holes won’t match and I’d have to skip 4 holes on the hub. So should I just buy a set of spokes according to the grin calculator and add a few millimeters for safety?

420b   100 W

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Re: Lace 32H rim with 36H hub motor

Post by 420b » Nov 22 2018 7:48pm

Bump. The grin calculator mentions this scenario but doesn’t provide a solution. Still looking for help.

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Re: Lace 32H rim with 36H hub motor

Post by briangv99 » Nov 23 2018 12:23am

I've redrilled the spoke flange on a bafang bpm to be a paired 32h single cross. It was quite easy to do with just a ruler, a marker, a centre punch and hand drill.

All the spokes are the same length and had no problems truing or with spoke tension.
20181123_161432-1040x585.jpg

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Chalo   100 GW

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Re: Lace 32H rim with 36H hub motor

Post by Chalo » Nov 23 2018 1:12am

Was it easier than finding a 36 hole rim for the job?

I've done mixed patterns before (28h rim/36h hub, 48h rim/32h hub)-- but having done that, I would go to great lengths to find an appropriate rim. There are a lot of them out there, and they don't even have to be currently available if you only need one.

16h and 32h have got to be the easiest patterns to lay out yourself, though. I think you came up with the best solution for your problem, and now you can even switch to a 36h rim in the future if it suits you.
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briangv99   100 W

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Re: Lace 32H rim with 36H hub motor

Post by briangv99 » Nov 23 2018 4:07am

All things considered, yeah it was easier. I had the 32h rim and the only rims I could find at the time were well over $100 shipped compared to the rim I had on hand. Re-drilling the spoke flange only took about half an hour.

420b   100 W

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Re: Lace 32H rim with 36H hub motor

Post by 420b » Nov 23 2018 7:45pm

I might go with a new rim. Seems to be the easiest route. https://www.ebay.com/itm/NEW-Alexrims-F ... SwNMVaTvTb

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Re: Lace 32H rim with 36H hub motor

Post by Smoke » Nov 25 2018 12:39am

As a heavier than average cyclist, I've had regret after flat spotting 32 hole rims on potholes, I wish I had gone with 36 hole hubs and rims.

On a bike with a heavy hub and the ability to sustain high speeds when a human cyclist would slow down, I can't think of a good reason to not use all the spokes.

Just sayin'
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Re: Lace 32H rim with 36H hub motor

Post by 420b » Nov 25 2018 3:07am

Smoke wrote:
Nov 25 2018 12:39am
As a heavier than average cyclist, I've had regret after flat spotting 32 hole rims on potholes, I wish I had gone with 36 hole hubs and rims.

On a bike with a heavy hub and the ability to sustain high speeds when a human cyclist would slow down, I can't think of a good reason to not use all the spokes.

Just sayin'
Right but my reason is that I only have a 32h rim

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Re: Lace 32H rim with 36H hub motor

Post by Smoke » Nov 27 2018 2:47am

I'm saying that's not a good enough reason.
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1N4001   10 W

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Re: Lace 32H rim with 36H hub motor

Post by 1N4001 » Nov 27 2018 3:28am

I've experimented with this idea aswell. The reason being lack of availability of decent 36H rims. I'm sure the 50-kilowatt crowd will soon tell me to just use the same 23 lb rims they use, but that wasn't an option for me.


See the attachment. It certainly is possible. Red/blue are front spokes, magenta/cyan are the back ones. Skipped holes are marked green (front) and yellow (back). I've ensured that the skipped holes are evenly spaced.

The problem with this approach is that you get lots of different spoke angles at the rim, possibly requiring many different spoke lengths and making it harder to true the rim. Still doable tho.

Myself I ended up having custom Carbon rims with 36 holes made. With extra Carbon and closed rim bed they're much tougher than alloy rims while still being lighter.
Attachments
rim-experiment.png

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Chalo   100 GW

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Re: Lace 32H rim with 36H hub motor

Post by Chalo » Nov 27 2018 12:47pm

1N4001 wrote:
Nov 27 2018 3:28am
Myself I ended up having custom Carbon rims with 36 holes made. With extra Carbon and closed rim bed they're much tougher than alloy rims while still being lighter.
That sounds cheap and convenient and easy to replace when damaged. Is there some kind of proprietary solution for connecting spokes, since the rim bed is closed?

Let's go back to something the OP said:
I had the 32h rim and the only rims I could find at the time were well over $100 shipped compared to the rim I had on hand.
So how much did you pay for your custom plastic rims, so we can make an informed comparison? My most relevant point of comparison is the 42mm wide, 36 hole double walled rim that I've used most often for pedicab hub motor builds at the bike shop. $40 retail.
Image

There are lots of good 36 hole rims available. If you're are hung up on here-today, gone-tomorrow trendy features, I can see how you'd maybe find selection somewhat lacking. But you don't have to tolerate parts incompatibility or disproportionate expense.
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Re: Lace 32H rim with 36H hub motor

Post by 1N4001 » Nov 27 2018 1:25pm

Chalo wrote:
Nov 27 2018 12:47pm
1N4001 wrote:
Nov 27 2018 3:28am
Myself I ended up having custom Carbon rims with 36 holes made. With extra Carbon and closed rim bed they're much tougher than alloy rims while still being lighter.
That sounds cheap and convenient and easy to replace when damaged. Is there some kind of proprietary solution for connecting spokes, since the rim bed is closed?
You're partially correct. It costs more than alloy rims, but Chinese Carbon can be had for reasonable prices. Don't be fooled, the quality is excellent. I got mine from Light Bicycle, they have a fairly good reputation among MTB riders, and they'll do customizations such as 36 holes or weird spoke hole angles for larger hubs. They'll even lace your motor for a small fee if you ship it to them.

Expect to pay around 200 USD per rim. That's expensive, but not insanely so.

As for lacing these rims, you have to insert the spoke nipples through the valve hole and guide them into position with a magnet. It's not as bad as it sounds. By not having holes in the rim bed you eliminate one of the main weak points of most rims, and you can run tubed or tubeless without needing any rim tape.

They can be had with regular drilled rim beds aswell if you prefer that.

Of course if weight is not a factor, then there is little point in considering Carbon.

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Re: Lace 32H rim with 36H hub motor

Post by 999zip999 » Nov 27 2018 2:01pm

Buy a 36h hole rim and make it ez and strong. Strength . K.I.S.S

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Chalo   100 GW

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Re: Lace 32H rim with 36H hub motor

Post by Chalo » Nov 27 2018 4:12pm

1N4001 wrote:
Nov 27 2018 1:25pm
You're partially correct. It costs more than alloy rims, but Chinese Carbon can be had for reasonable prices. [...]
Expect to pay around 200 USD per rim. That's expensive, but not insanely so.
It's a lot less than I expected. All the carbon rims in my distributors' catalogs have MSRPs of $450 and up.

I think you'd have to be using a very, very light hub motor before a few ounces of weight difference between a carbon rim and an aluminum rim becomes a significant part of the overall picture. If that's what floats your boat, I recommend using 14-17ga spokes as well. They're light, but they also increase wheel reliability compared to thicker spokes. They work effectively at modest tension levels that won't risk damaging laminated composite rims.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

420b   100 W

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Re: Lace 32H rim with 36H hub motor

Post by 420b » Dec 03 2018 2:07am

I haven’t made any progress. Does anyone know the proper way to measure this out?

Smoke   1 W

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Re: Lace 32H rim with 36H hub motor

Post by Smoke » Dec 04 2018 11:19pm

There are several spoke calculators the can do 36 hole rims, so get a 36 hole rim and lace it up.
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