Saturday, November 8, 2014

Heavy Duty Wheels

Bill Mould wheels.

Brass washers concaved to keep the spokes centered

Building a new heavy duty wheel

I ended up with a cheap crappy 2 inch wide (1.4” I.D.) motorcycle rim from; The rim walls are bent inward at the seam it could never be used for rim brakes
The tire was not as thick as the front tire, but better than a bicycle tire. Two inches wide off the rim, turned out to be 2.25” on the wide rim and 23.25” O.D.

I would have been better off just buying a better bicycle rim and tire (Hookworm). But at least the spokes I used are fantastic, Sapim 13 gauge at the hub, swagged down to 14g for the rest of the length. And the damn calculator I used gave me 1mm longer than it should have been on the gear side; which made it impossible to tighten them as much as I wanted.

I used brass washers on half of the left side spokes because they were a bit loose in the holes, note the concave effect that keeps them centered in the holes.

If your frame can fit a 2.75” tire you should be able to use a 2.25” tire. Best to build your own frame to fit 3.5” tires, or use a 16” tire that is 20.25” O.D.

And if there is room you could build a wheel with symmetrically tightened spokes. As I did years ago for a trike.

two inch moped tire on motorcycle rim

spoke head with washer inside motorcycle rim

Parts for Hubs

You can get a nice strong hub for a very reasonable price, but a year later, you will need new bearing cones. And Shimono, for one has stopped selling stock cones that fit the hub I was suckered into buying. The SLX 675 that I just built into a wheel.

So Now I have to start looking for a 135mm wide cartridge bearing hub. I am really pissed off. Most of the new 12mm thick axle hubs are 142mm wide; I don't think I can adjust my frame to fit one, with out a lot of out sourced labor. All the more reason to build a cargo bike frame that can hold the new wide hubs and 3.5” wide moped tires.

The bicycle industry is controlled by the racing industry by way of capitalism.

This is what happens when the tip is too wide

If you can find a drive hub that has a larger flange on the right sprocket side, all the spokes will be able to be tensioned the same, making a stronger wheel. And if you can expand your frame for a 142mm or wider hub, the wheel would be even stronger and 12mm or thicker through axles would be much stronger, but a different way of attaching a B.O.B. trailer maybe needed.

Making the left side larger on a derailleur wheel would exacerbate the tension disparity, not equalize it.

There are companies that do it. The reason it's not more common is that the difference has to be pretty radical (i.e. a way more expensive shell to produce) before the tension disparity is affected much, and at the same time, it doesn't take much difference at all before lacing the hub gets difficult using conventional j-bend spokes.

Beware the Velocity ATB free hub cassette body for the

velocity hubs are very expensive!

197mm wide snow/sand bike hub for super stringth

Thru-Axle hubs

The Phil Wood's MTB, DT Swiss 540 Tandem, the White Industries MI6 Disc Rear MTB Hub and the Chris King tandem, are possibly the only hubs built strong enough for a really heavy cycle-truck. Unfortunately they are very expensive.

The VeloOrange Grand Cru hub uses an aluminum axle of all the insane things. Don't use it for a cargo bike!

Buy several sets of bearings. I don't trust the bicycle industry; they could stop making parts for their equipment at any time.

For a bike that will hold around 600 to 800 lbs on two wheels, a 20mm thru axle is best even if you don't have more than one gear on the hub but you may need to build a new frame to use a much wider hub for an even stronger wheel; like a 197mm sand-snow bike hub.

This LaserDisc hubs have poor a reputation for falling apart.

And the 3 bearings look too small,

yet possibly more water tight than others.

Laserdisc pawls on the freehub cassette body

12mm solid mild steel axle fits through a sleeve.

The bicycle industry makes some very strong aluminum rims, if you are willing to pay $100 or more for them. But I think it better to spend the money on a better hub. And you may have a hard time finding a good rim for a 24” wheel.

But whatever you do, remember that there is no substitute for a well-built wheel. Watch this video and read the information on his site.

Up until the early 1980's typical wheels had 32 spokes front & 40 rear, standard for British bikes, 36 front and rear for other countries. For a really heavy cycle-truck 48 spokes is not unreasonable even with the best box wall rim.

When the spokes are farther apart on the rim, it is necessary to use a heavier rim to compensate. Symmetrically dished wheels are stronger because on a typical drive wheel the hub is designed to have only around 60% of the spoke tension on the left side as there is on the right side.

Wheel building

Best way to build a super strong wheel

It maybe counterintuitive to use thinner spokes, but it works

Wheels remain reliable and trouble-free only to the degree that their spokes stay tight when loaded. The largest loads on wheels (weight, bumps, and torque) all have the effect of dynamically reducing tension in some spokes. For example, when you apply weight to a bike's axle, the rim flexes inward a small amount above the contact patch, and the spokes in that area are reduced in tension.

For a spoke to stay tight when the wheel is being loaded, it must already be stretched enough elastically to follow the rim's flex without becoming slack. The thinner the spoke, the greater the stretch at any given tension.

A 12ga spoke is about 2.7mm in diameter. A 14ga spoke is about 2.0mm in diameter. So the 12ga spoke has about 1.8 times as much cross-sectional area, and requires 1.8 times as much tension on it to exhibit the same amount of elastic stretch. Thing is, bicycle rims can only withstand so much tension before the holes pucker or crack. So it's the rim and not the spokes that limit how much spoke tension you can use. 14ga spokes are already capable of being tightened to the limits of bicycle rims. Same goes for 14-15ga double butted spokes.

Using 12ga spokes on bicycle rims means their limited amount of stretch makes them go slack at about 55% of the weight or dynamic load that would slacken a 14ga spoke tightened to the same static tension. When spokes go slack periodically, their nipples unscrew and they chafe the holes in the hub and rim.

This is a chronic problem with hub motors used on pedicabs. Pedicabs carry a lot of weight-- up to a ton or more these days-- and being trikes, they strongly side load their wheels whenever they change direction. Most hub motors come with 12ga spokes, and these never stay tight when used on a working pedicab. Wheels come out of true, and wobbly unsupported rims become bent, and rim holes crack under the stress. When I rebuild these wheels, I make a few changes that radically increase their reliability. I use bigger, stiffer rims. I increase spoke bracing angle as much as I can, by lacing spokes all outside the hub flanges and by lacing across to the opposite side of the rim if the holes are staggered. And I use 14ga spokes, 14-15ga swagged spokes. These wheels are much more reliable with much less maintenance than any pedicab wheels featuring 12ga spokes.
Heavy duty wheel with 14-15guage spokes

If you use motorcycle rims, those are thick and heavy enough to withstand very high spoke tension. And they're stiffer, so they flex less in response to any given force placed on them. So it's fine to use thick spokes, as long as they are kept suitably tight. That's why they're drilled for fat spokes. Your hubs may or may not cope with elevated spoke tension or with being drilled out for thicker spokes. Their flanges can break or pull through.

This wheel has the qualities that will allow it to carry lots of weight and brake torque for how much the wheel weighs: massive double walled 20" aluminum rim, highly tangential spoke lacing, and 14ga stainless steel spokes. This wheel weighs only 1.3kg without a tire installed. I know from experience that it would work for an overloaded pedicab or cargo bike.

Use only a drop of oil at each nipple. A thread locking compound like Spoke Prep, linseed oil, or purple Loctite will prevent the nipples from unscrewing when the spokes go slack, but it does nothing to prevent the loss of spoke structural support for the rim under such circumstances. With the right configuration for the job (strong and stiff enough rim, thin enough spokes), spokes don't go slack and thus the nipples don't need to be stuck in place.

Best deal on top quality 14-15ga spokes in unusual lengths is Dan's Competition. They also offer 14-17ga spokes, which are useful for the left sides of dished rear wheels.

Just remember that there is NO aspect of wheel building more important than the balancing of spoke tension. The majority of wheels are under tensioned, even new wheels on good quality bikes. If the spoke tension is not carefully balanced out, you will not be able to apply as much weight without undesirable effects.

4 cross pattern should be avoided unless you have 32 spokes. More spokes will end up crossing under the first spoke head. 

Use a four-sided spoke wrench!

effective rim diameter 

I set all three of these calculators for the same wheel:


This one calculates more data,

but it is a bitch to use for off set rim holes.

12 gauge spokes:

For a motorized bike use 13 gauge single butted Sapim stainless steel spokes (never use eBay spokes) and with a motorcycle rim. Unless you can get an expensive downhill racer boxed wall bicycle rim that really is as strong as one made for high powered vehicles.

Never use the abysmal quality spokes found on most kits. They just aren't strong enough or made of materials with the right properties to even be called spokes. As an example, the last wheel I had to re-spoke was laced with cheap 12g, along with several good quality but thinner 14g spokes. I cut the 12g spokes it with a pair of 6 inch wire cutters and they snipped through with one hand rather quickly. when I got to the thinner but good quality 14g spokes, I had to use both hands and bare down hard on the cutters, to cut through them. They were more than twice as strong.

For belt drives think about Kevlar threads in the belt.

4 cross spoke pattern

You can go too big on spoke size, bigger is not always better. The more tensile stretch on a spoke the lower the chance of the spokes coming loose and the wheels integrity will remain intact for longer . If you fit spokes that are too large the tension needed to stretch them may not be achieved resulting in a wheel that will come loose far sooner. And broken spokes occur when there are some loose ones as the load becomes unevenly shared among the remaining tight ones and constant loading and unloading of the spokes cause fatigue failure.

If using a alloy bicycle hub with a motorcycle rim do not use thicker than 12 gauge spokes unless they are swagged; wrongly known as “butted”. And using a 4 cross pattern (3 cross on 20” wheels) changes the direction the spoke applies stress to the hub flange and allows greater spoke tension with less outward "pull" on the flanges.

13ga laced into a normal MTB rim with no drilling, and slide nice and tight into standard hubs. These are good choices for people building cargo bikes, and bikes that will have gross weights over 350lbs loaded. But 12ga maybe better for 600lbs. Possibly 11ga on the drive wheel, for heavier vehicles, or for use with powerful motors and hard acceleration.

for motorcycle wide flange hubs

this was the best, but I don't think they make them any longer.

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