aaronmichael

Another wheel building question here. I'll try to make this short and sweet.


I'm a manager at a LBS and I had a customer bring in an electric bicycle wheel to me the other week to rebuild it because the rim was damaged. It was originally laced with a 2x pattern and I assumed this was because of the size of the hub limited it from being laced 3x (because why else would it not be laced in a 3x pattern?). Anyway, I had to learn how to lace 2x and the end result gave me spokes that were too long and I'm going to have to rebuild it again.


Just today I had another customer bring me a 20" Promax wheel and would like to have it laced to a NuVinci hub that also has a very large flange diameter, but not as wide as the Bafang motor in the other wheel. My question is, will I be able to lace the Promax/NuVinci wheel with a 3x pattern or will the spokes overlap too much with this options. Any advice or feedback always appreciated, thank you!

fietsbob

36 hole Could go 3 cross . 4 cross 1st cross is the nearest spoke on the other side of the hub flange passes by headed to the opposite side of the rim..

Rohloff recommends 2 cross 32 hole* , but just 1 cross with a 406 20" rim.. * key spoke on left flange has to clear the casing separation bolt circle to use 3 cross.
My Bike Friday has a large 36 hole IGH. but uses a 24 hole rim, and skips every 3rd hole , cross number one is just over the hub flange.
Brompton uses a 2 cross.. 28 hole hub & rim. ,, similar.. these are 349 16" wheel rims..

aaronmichael

Both of these builds are 36H hub with a matching 36H rim. Why only 1 cross with a 20" rim? I always though the integrity of the build goes down with each less cross that happens. I could have misunderstood from the beginning though. If I can, I've always just gone with 3x for my builds.

fietsbob

Ask Rohloff, not me.. I'm just quoting the Manual .. & how the wheel was built by Bike Friday company ..
they are 100mm spoke hole diameter , 60 mm apart .. ..






....

car knocker

3 cross will make the spokes enter the nipples at a acute angle and can result in them breaking there. With 2 cross lacing the spokes enter much straighter.

sweeks

It would be pretty hard to build a cross-3 wheel with a 20" rim and a large diameter hub. Here's a cross-2 wheel I built with a 406 rim and an Alfine-11 hub... it was hard enough!

Cross-2 lacing ieth Alfine-11 hub and 406 rim

aaronmichael

The trouble would be the angle of the spokes on that small of a wheel if it was laced 3x? What spoke length did you end up using for that wheel build in the photograph? What (or whose) method of 2x lacing did you use? Thanks for the input.

JohnDThompson 

On hubs with very large flanges and rims with relatively small radius, you will find that large-count cross patterns will result in either the nipple exiting the rim at an unacceptable angle that would exacerbate nipple failure, and/or the spokes will lie across the hub flange and interfere with adjacent spokes. Exactly how many crosses will work depends on the actual hub flange and rim radius being used.

sweeks

The spoke length was determined using an on-line spoke-length calculator; I don't remember the length but it's not transferable to another wheel unless the hub and rim are *identical*. The calculator (there are several on line, and as far as I can tell they all give comparable results, I used more than one) has worked for me every time I've used it (them), and I've built all of about 6 wheels!
The method I use is Roger Musson's excellent (and inexpensive!) book on WHEELBUILDING.

EDIT: I don't remember if Musson specifically addresses "cross-2" lacing, but it's not hard to figure out if the spokes are the right length... which they should be if you've inputted all the necessary data correctly.

HillRider

A 700c rim used with a 32H "small flange" hub makes the spokes almost exactly tangential to the hub flange when laced 3X. As the hub flanges get bigger, the spokes become angled too far inside of tangential if 3X lacing is done. Going to 2X lacing with a large flange hub allows the spokes to remain tangential.

aaronmichael

Thanks to everyone for the feedback. Looks like I'll be lacing that Promax / NuVinci build with the 2x pattern. Just confused on why my spokes ended up being too long (3-4mm) on that first electric wheel build that I posted a photo of. I used an online spoke calculator and made measurements of the hub using a pair of digital calipers. However, this was my first time doing a 2x (using Musson's method) wheel and it was very difficult to measure though because of how large the flanges are. I'll double check all my measurements and the lacing pattern.

It sounds like there's no real scientific way to check whether a 3x will work on any particular hub/rim combination. Just have to use my best judgement based on the flange diameter and ERD of the wheel.

Dan Burkhart 

The largest hub I have built into a 20" wheel was a Rohloff, and I went 1x with that one. Mind you, that was 32 hole, not 36, so that makes a bit of difference.The flanges on the Nuvinci are somewhat larger than the Rohloff, so I'm thinking 1x would be appropriate even with 36 holes.

fietsbob

Perhaps your spoke length calculation was off, by being too long by that 3~4 mm?

davidad

On a 20" rim with a large flange hub the 2 cross may make it easier to true. A friend had a 20 on a Sturmey archer front drum brake hub that was difficult to spoke and get the wrench on the nipples to true.

madpogue 

Is there a significant difference in the ERD between the damaged rim and the new one? Single vs. double wall? Or the new rim has a deeper channel? That would call for re-calculating spoke length.

dabac

It’s probably possible to calculate when one spoke overlaps another at the hub. But there is no definite go/no go-number for spoke angle at the nipple. What works for one mileage may not work for another.

IPassGas

I had much spoke breakage at nipples for a Rohloff laced 2x into 559/36 (*hitty) rim. I changed to Ryde Andra rims and used Sapim Polyax (or if you like DT prohead) nipples. The nipple/spoke line is now perfectly straight. The Andra rims have angular drillings especially suited for large hubs. The polyax nipples allow a greater nipple angle at rim. I used Freespoke to calculate spoke length and carefully measured ERD. I prefer Freespoke because it also gives radial and lateral spoke angles at the rim...very handy. For my build, it gave a total angle of 11 deg at rim with 8 deg radial. The Andra radial drilling is at an angle of 8 deg. The new wheels (on a tandem) have been great. I should have built these at the start, but "experts" said otherwise.

For 20", I would think only 1X will work, otherwise spoke angle leaving nipple will be bad (e.g. sweeks pic in this thread shows bad angles).

Bill Kapaun

IF you want to deal with the trigonometry....... (I don't and I was quite good at it 50 years ago)
Maybe dig out a piece of cardboard, compass, protractor..... and do a 1/4-1/2 size mock up?

The only "rule" I know is N/9 is your max number of crosses, where N = spoke count. Larger diameter hubs can trump that rule.

Jeff Wills

Exactly. The spokes are going to be very short and the wheel will be symmetrical so it's going to be very strong no matte what. 2-cross or even 1-cross (not interlaced) will be just fine,

aaronmichael

Thanks to everyone for their input. Sounds like I shouldn't be hesitant on using a 1x or 2x pattern for the wheel build if that's what it comes down to. This has given me lots to think about and research, thanks!

Dan Burkhart 

Yup. I have built several 1x wheels with hub motors etc, and never interlace. You can go all heads in or heads out.

aaronmichael

Anyone have a good reference for how to lace 1x if that's the way I end up going?

vane171

The wheels in pictures look like motorcycle wheels. The fat, almost rod-like looking spokes and lacing pattern remind me of what I had on my first 50cc motorcycle when I was fifteen years old. If all fails, you might want to send the customer to a motorcycle shop

Anyway, are eBikes still bikes? I mean, just because it somewhat looks like one, is it a one? Is 'moped' a bicycle, or a motorcycle? You know that kind of propelling device maybe still used in Europe? It has a motorcycle engine but you also need to pedal like on a bicycle, especially uphill when the little engine can't do it anymore... Do we live in interesting times.

Jeff Wills

Uh... use a calculator like Spocalc which gives you the lengths for 1X (and everything else). Put the spokes on the hub, cross adjacent spokes, insert nipples, go on the next pair of spokes, pretty soon you're done!

https://www.sheldonbrown.com/rinard/spocalc.htm

Bike Gremlin

I use this spoke length calculator:
https://www.wheelpro.co.uk/spokecalc/

It gives info when there is overlap (and how much spoke head overlap there is).
With hubs that have very large flange diameter, paired with rims smaller than "28 inches", another concern regarding the max. number of crosses is the angle at which the spokes enter the rim.
Sapim HM nipple washers can help with that, on some rims, allowing for the nipple to be set at an angle, more "naturally" (they will affect the spoke length calculation - measure rim ERD with them installed).

So it does boil down to a bit of trial and error: lace, see if the spokes are too bent at the rim, then try with one cross fewer (and shorter spokes). I aim for the highest number of crossings achievable, since it does make a stronger wheel (all else being equal, properly built, no too much spoke head overlap, and with no severe angle at the spoke rim entry).
Writing the measurements down helps for the future builds.