Going from 36 to 72 spokes on hub motor wheels

I'm done with replacing spokes on rear hub motors.
It seems like whatever I do, the spokes do break or come loose ultimately.
Belleville washers are nice but introduce their fair share of issues.
For my next build I consider a 36h setup hacked to 72h.
Anyone done hub flange and rim hole drilling?
My guess is I sould be best served by cruiser rims.
All your experience is welcome.

The rims you have had problems with, where they Chinese made or your own builds?

I built my own wheel and have done over 6600 miles on it. Broken one spoke, within the first month, and that is it.

36 spokes are plenty even for a powerful bike. I run a 5304 in a 26 inch Mavic downhill rim, at 84 volts, up to 140 amp at acceleration, with a Lyen 18 FET controller.


If you cant't get a 36 spoke wheel to work, you will only end up with more problems with 72 spokes.
Just rebuild your hub on to a decent rim ( Mavic EX321 or similar) with good quality spokes, keep them tight and you will have no issues.

Build the wheel, stress it, by hand, re tension, ride for 20 meters, check again. ride for 100 meters, check again. Do a kilometre or so, check again..and keep checking every couple of km for the first ride..go out and ride 10 or 20 k..checking all the time.
Then check every day for the first week or so..then monthly..then when ever you think of it.

I have nto checked mine in over 1000miles now, and I know if i do, I will need to do nothing to it.

Once the wheel settles down and the nipples 'bind' up to the spokes the wheel is set. only then need to check if you hit something and think you may have damaged the wheel

http://singletrackworld.com/forum/topic/mavic-ex321-on-hope-xc-hub-front-wheel
http://www.mtbr.com/cat/tires-and-wheels/rim/mavic/en-321-disc/prd_352662_139crx.aspx


http://www.roseversand.com/article/mavic-mtb-rim-26-ex-721-157932/aid:157934

okay, I already use quality Rigida Andra rims and the rims do well, it's the spokes that give.
it appears to me that spokes break from excessive tension rather than lack thereof. so i never tighten them too much. perhaps the way forces are distributed over a bump cause greater tension on the bump-opposing spoke group that could be prevented by higher overall spoke tension, I dunno. Sure I do something wrong, it's hard to detect though. Perhaps a 700c wheel at 30-40mph on partially bad roads and battery in the rear is not going to last anyway.

Well rim looks OK.
Where did you get your spokes from/

I used Newsomsportec and they sell good quality spokes, but John Holmes from here on the forum is good too, and he has helped lots of people here on the forum out with spokes, but I have not used John yet. I will for my next build though
I would say that spokes break from un even tension rather than overall excessive tension.

As a wheel and its spokes 'bed in' some are going to get looser, some tighter. There for the tighter ones take more of the load..and then break.
The first few rides and the first few weeks and months are the critical time, where you need to be checking them all the time.

I suppose 72 hole is an idea, but if you have a small hub, then those drillings are going to be close together, and then the risk is breakage of the flange...then you really are screwed. At least rim and spokes are easier to fix than a broken hub flange

What thickness spokes did you use? maybe go up a size?...or down a size. There is an argument that thinner spokes are some how better. Do not remember what the argument is for them, but I do remember it being mentioned

I used 12 gauge stainless from http://www.newsonsportec.com/ and had o issues with them at all...apart from them forgetting to send the nipples in the first order!!

miuan said:

I'm done with replacing spokes on rear hub motors.
It seems like whatever I do, the spokes do break or come loose ultimately.

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Spoke breakage is a result of poor quality spokes or poor build technique. Spoke loosening is a result of poor build technique or too light and flexible a rim for the load.

Belleville washers are nice but introduce their fair share of issues.
For my next build I consider a 36h setup hacked to 72h.
Anyone done hub flange and rim hole drilling?
My guess is I sould be best served by cruiser rims.
All your experience is welcome.

Click to expand...

I have drilled 32 hole hubs for 48 spokes and 24 & 36 hole hubs for 72 spokes, and I have successfully built wheels with them. I don't think you should do it.

Here's a 32 hole Rohloff gearhub on my bike, which I have drilled for a total of 56 holes, 8 of which are unused original holes that I plugged with small screws:


More spokes probably won't help the issues you have identified. If you use the same kinds of components you have been using so far, breakage will still happen, and spoke loosening will be more frequent with twice as many spokes.

Cruiser rims are usually single-walled and made more for generous width than for strength or stiffness. They won't help you. 72 hole rims are rare, and don't come in high quality versions. If you only double the number of holes in the hub flange, they won't alternate or stagger anymore, so crossed spoke patterns won't work right.

Hub motor wheels that come pre-assembled from China are notorious for their poor materials and low quality construction. It's no surprise that they cause problems.

Rather than getting sidetracked on some folly, first try doing the job right. Use a sturdy, high quality double walled rim like the Alex DM24 or Velocity Psycho, and build it up carefully with 2.0mm spokes made by DT Swiss, Sapim, or Wheelsmith. Make sure all the spokes have at least 100kgf of tension by measuring with a tensiometer. Make sure to stress-relieve the spokes by one of the proven methods (squeezing parallel pairs, prying crossed pairs, or loading the axle on a special fixture). Use cross-1 lacing to get the best results from a hub motor.

Read the instructions on Sheldon Brown's page before you get started. Or you can pay an experienced, capable wheel builder to do the job for you.

I don't think you'll need to use anything special or unusual to have trouble-free wheels.

Chalo

That Rigida Andra rim looks more than adequate. But you must use enough tension! The load on a wheel is carried by the tension in the spokes. If you don't use enough, they go slack and problems result. That rim should support 125kgf or more of tension per spoke with no difficulty at all.

When you ride under normal circumstances, the weight of the bike on the wheel's axle takes tension away from the spokes underneath. It does not add much tension to the spokes above. By using low tension, you are making a wheel that doesn't distribute forces around the wheel correctly.

Spokes usually break not from overload, but from metal fatigue. Fatigue cracking starts if you forget to stress relieve.

If you don't fully understand what makes a good wheel, just do it the way that successful and proven wheel builders do-- with quality parts, plenty of spoke tension, and good build technique.

NeilP said:

What thickness spokes did you use? maybe go up a size?...or down a size. There is an argument that thinner spokes are some how better. Do not remember what the argument is for them, but I do remember it being mentioned

Click to expand...

Spokes maintain tension (as the rim flexes under load) by retracting elastically like springs. That's why they have to be thin to work right. Too thick a spoke goes slack when the rim is loaded, because it isn't stretched enough to retract and maintain tension on the rim. That in turn makes the nipples unscrew if they are not glued in place.

14 gauge (2.0mm) spokes are in balance with the stiffness and strength of sturdy bicycle rims. To get good results from thicker spokes, you have to use extra-heavy rims like those on a motorcycle so you can turn up the tension much higher.

Neil, you might be interested to know that tensioned wire wheels were invented in 1808 not for bicycles, but for early aircraft. They weren't used on bicycles until more than 40 years after that.

Did not know that..you learn something new every day.

I used 2.6 mm spokes 12 gauge, but I would not go thicker, the 14 gauge 2mm will do just fine as Chalo says

The problem with drilling rims is the valve hole is in the way. You could drill just one side the side with the most broken spokes. HiE has done the most weird drillings look for these on the web. Santana built some 16 32 wheels with Phil Wood hubs and custom drilled super champion rims I have been unable to find a photo. These are a pain to build you will need to use trig to get a ball park spoke length and don't expect it to work the first time. If you try to put a 16 32 drilled hub with a 48 hole rim some of the spokes will be bent too much at the nipple and will result in spoke breakage at the nipple it is possible you will need to find a rim that does not have directionally drilled spoke holes . If the spokes on the side with extra drilled holes are not the same tension this will result in a broken flange. So your best bet is to drill both sides and order 72 hole rims. http://speeddream.com/ this guy may drill rims for you. The second best is to order custom drilled 54 hole rims. Campagnolo builds wheels with double the spokes on one side study these to see how it is done. I have been building dishless wheels and have never broken a spoke in 80000 touring miles. Details here http://www.zerodish.wordpress.com and here http://wheelfanatyk.blogspot.com/2010/10/for-spoke-nerds-only.html

Chalo said:

By using low tension, you are making a wheel that doesn't distribute forces around the wheel correctly.
Spokes usually break not from overload, but from metal fatigue. Fatigue cracking starts if you forget to stress relieve.

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This is probably my case. Too loose spokes (usually caused by uneven dishing) and lack of stress relieve.

miuan said:

This is probably my case. Too loose spokes (usually caused by uneven dishing) and lack of stress relieve.

Click to expand...

Many rear hub motors are just terrible in the amount of offset they require in the laced wheel. When I was first looking at Crystalyte motors years ago, it was obvious just from the dimensional diagrams that the right side spokes would be almost completely flat, and thus they'd have to bear several times as much tension as those on the left (which would be almost slack). After some time trying to figure out a tolerable remedy, I just bought a front hub version. Except for using a rim with a huge built-in offset, like the offset version of the Large Marge, there is no way to correct a rear hub that has almost no bracing angle on the right side.

Crystalyte corrected this flaw in later versions by moving the flanges off towards the ride side of the hub. That still makes for a relatively weak wheel, because the flanges are spaced too closely together so that they'll be compatible with small diameter wheels, but it's much better than the options I had available to me in the early 2000s.

What you can do to help make your existing hub work better is lace all the right side spokes on the outside of the flange, all the left side ones on the inside of the flange, and try to get them as tight as you can manage. Washers underneath the spoke heads may make the spoke elbows fit better on a thin steel flange, and help keep them from breaking there.

Chalo would like to see a pic of your great great grandfathers 1808 aircraft with spoke rims. Must be all in the family.

999zip999 said:

Chalo would like to see a pic of your great great grandfathers 1808 aircraft with spoke rims. Must be all in the family.

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Here are a couple of photos from the Wikipedia article on George Cayley.

A replica of Cayley's glider:


Another replica: