Hub motor spokes

[bkwilless]

I need help. I bought a bike from High Powered cycles with a bmc 1000 watt (2500 peak) motor. The lacing has extreme angles like on a motorcycle similar to what I see on the stealth bomer bikes or even the pedego bikes. Anyway I weigh 280 lbs and the spokes keep breaking at the nipple/thread connection. I (well a guy at the local shop who is a mechanic for professionals competitors) completely respoked the wheel with 2.3/2.0 sapiam double butted and poly axle nipples to add some angle. They began breaking again at the same mileage as the first set.

What are my options? Thicker gauge and drill out the rim to accept a thicker nipple? A less sever lacing pattern? Both? Unfortunately I am not getting help from High powered other than them defending the way it was laced when I received it. They pointed out how they have done 500 + this way with no problems. I asked how many of those were guys weighed 280. NO reply!

P.S. I am looking for e-biker advise as my wheel lacer has no experience with e-bikes. Here on Crete no one has. Also he is out of town at some races.

 

[jondoh]

The local bike guy here in san jose does wizzers which are classic schwinn cruisers with gas motors. He can build a wheel using motorcycles spokes. Says the spoke and nipple will pierce the rim before breaking.

Look up bicycle express in san jose on william st. Ask for Chuck!

Thing is, you'll need to send the hub and rim to be measured up. Spokes will need to be cut to length-- and these thick spokes are a little expensive but since you need a stronger wheel...

 

[liveforphysics]

Gotta have a thin enough spoke to keep it under tension. If you've got a bicycle rim, it can't handle the tension needed to make a heavy gauge spoke function correctly. Motorcycle rims are fantastic with bicycle spokes. Bicycle rims are fantastic with bicycle spokes. Bicycle rims are a perpetual fail with motorcycle spokes.

If I were you, I would considder getting a motorcycle rim to lace your hub into with motorcycle spokes. This also gives you some fantastic tire options as well.

 

[John in CR]

I'd venture to guess that Crete has shops very experienced in mopeds and small motorcycles, and probably at a better price than bike shops. Get them to fix you up with a stronger overall wheel (spokes, rim, and tire). Remind them many times to be careful with the wiring harness and not to turn the axle much as part of that protection. Guys with no hub motor experience can mess up a hub motor's wiring harness in a heartbeat.

Good luck with it, and please be sure to let us know what worked out, because moped wheels and motorcycle wheels on hub motors are too few and far between around here. Mine came with moto rims and spokes stock, but I'd like to change my other hubbies over too.

John

 

[bkwilless]

Thanks for the advise so far. I plan to go to some moped shops and some machinist monday. These guys look promising http://www.thewheelmaster.com/MountGoats.htm ...but I would need to ship the wheel to them and they want $195. Though they are giving a lifetime gurantee.

 

[curious]

I agree with liveforphysics on this. You have to keep spokes under tension all the time to keep them from breaking. The spokes stretch and you need to periodically re-tighten them. How frequently - depends on spoke material/gauge. And it is a fine balance between rim strength and spoke elastic strength. Of course there is a brute force approach - using both oversized spokes and rims (motorcycle or ultra heavy duty BMX/downhill). BTW there has been a recent thread on custom motor hub spokes somewhere in this forum.

 

[RICK]

Check out the Sapim Polyax nipple. It has a rounded seat that can rotate up to 10 degrees (or so). This will relieve some of the angular misalignment. I got some from Harbor Bike in Michigan (took a couple of weeks for delivery). It does seem to help on my 9c/26 Sun Rinolyte wheel.

Motorcycle rims have a pressed ball shaped seat for the nipple, which rotate to much higher angles. Hard to do with aluminum rims I think. Maybe someone could make a nipple/eyelet combination for large hub e-bikes. Not a very big market though, so don't hold your breath..

 

[ebikes-sf]

I serviced a few bikes for local customers purchased from hp-cycles and noticed that they use cross 2 spoke pattern on their 26" wheels. Also, noticed their wheel builds are not very high quality. Cross 2 is ok for 700c rims but on 26" it causes too much angle at the nipple. I suggest relacing with cross 1 pattern and higher quality rim. Quality build is also very important. True wheel doesn't necesseraly suggest a quality wheel build.

After a couple of years of lacing BMC motors I found Velocity Cliffhanger rim with Wheelsmith DH13 spokes and cross 1 pattern to be very sturdy. I use one on my daily commuter Surly Big Dummy cargo bike with BMC V2. I often ride with my wife and a dog on the back, over 300 lbs excluding weight of steel cargo frame, batteries etc...

 

[FMB42]

I agree with John in CR's motorcycle rim/spoke comments. The vast majority of rims used in most hub motor assemblies were never designed for use with large diameter hub motors (and the spoke angle problems they cause).

 

[bkwilless]

So I had it laced with a one cross pattern. Prior it would bread at arround 170 kilometers. There is no evidence of any impending break and I have gone 250 kilometers.

Thanks for the advise.

 

[johnrobholmes]

Once cross really is the best bet, and don't go above 13ga with normal mtb rims! Your wheel should last quite a bit longer now.

 

[CX]

Could you guys show me what you motorcycle rim looks on your motor?

 

[johnrobholmes]

This is one example, I have done many similar builds with alloy and steel rims alike. Most of them are 16" (20" bmx compatible) and 17" rims.

 

[ebikes-sf]

Nice wheel!

I really like Wheelsmith DH13 spokes, they're 13ga at the shoulder, and 14ga on threaded end. I haven't seen one brake yet on wheels I built with BMC hubs. Sapim also makes similar very good quality 13/14ga spokes.

 

[johnrobholmes]

You wanna know where WS gets their butted spokes? :lol:

 

[itselectric]

You wanna know where WS gets their butted spokes? :lol:

where? Sapim?

 

[johnrobholmes]

I can not confirm this for sure, but there are striking similarities between many of the wheelsmith butted and fancy drawn spokes and the capabilities of the sapim factory.

 

[ebikes-sf]

After my spoke supplier forgot to ship my order again, I finally decided to get my own Phil Wood spoke cutting machine with 15 to 12 gauge thread rollers, so hard to find 13/14, 13 and 12 ga spokes will no longer be an issue, I'm excited. Anyways, in process I learned that Phil Wood spokes, marked with PHIL, are actually Sapim spokes. So may be Wheelsmitth does the same?

 

[johnrobholmes]

So that is probably why Phil Wood just bought all the 56tpi 12ga nipples out from under me :lol:


You will probably break your 56tpi die set trying to do 12ga. They just aren't rigid enough on the edges, and the thread profiles break off with use at higher pressures needed for the larger diameter spoke.

 

[bkwilless]

I used the Wheelsmith DH13 spokes and they broke. It is really because of my weight. 290 lbs. The one lace patern has given me no grief. I don't even know what spokes the guys used. He said they were dutch but my greek is a bit borken anyway.

 

[johnrobholmes]

Probably your weight combined with the nipple insertion angle. At this point you can go with 12ga and see if it helps, but I have a feeling it will still happen but just at a longer time period.

The ultimate solution would be a motorcycle style rim with angled holes. You would have to have disc brakes. A 17" rim and 2.25 tire would be close to 24" high.