Folding Bikes - Small wheel building question

I think this group has the most experience with small wheels, so I ask it here.

Do we really need 32 or 36 spokes on the smaller wheels we ride? Doesn't the smaller diameter result in less stress on the spokes?

I'm thinking of building up my own 349 mm wheels, but am considering just using 18 or 16 spokes. I like the minimalist, cleaner look. Is that silly?

Much depends on rider weight, rim width, tire size and shape and the quality and tension of the build. The Moulton F frame and Mark III original standard on steel 349 rims is 28 hole. These have proven very durable for me on my 1965 Moulton Stowaway and 1974 Mark III.
I am a large person so you may be able to manage with fewer spokes if you are not a clydesdale. I have no experience to offer on reduced spoke numbers on 349 wheels.

As far as I can deduce from the theory, the spoke spacing at the rim is pertinent, at least to a first degree. So going by that, even 28h is plenty; a 24spoke 406 wheel is about equivalent to a 32spoke 700c wheel. So a 16-spoke 349 is eq. to a 32-spoke 700c wheel wrt spoke spacing at the rim.

I have a 16spoke on my Swift front and I have meted out harsh treatment to it but it soldiers on.

I say go for it. Especially with suspension, the wheels live easier.

You have the choice to skip every other hole on a 32h or 28h rim, but this may lead to every 2nd spoke laced to a hole drilled for the other side; or you can skip every other pair, which will not have that problem. In addition, the rim will tend to be straighter as spoke loads are balanced more. With widely spaced spoke the rim can assume a snake pattern.

I think this group has the most experience with small wheels, so I ask it here.

Do we really need 32 or 36 spokes on the smaller wheels we ride? Doesn't the smaller diameter result in less stress on the spokes?

I'm thinking of building up my own 349 mm wheels, but am considering just using 18 or 16 spokes. I like the minimalist, cleaner look. Is that silly? Lets assume that the supported weight is the same.

First lets look at spoke loading from the hub end.

The forces on individual spokes will depend on the number sharing the load. It does not matter what the wheel diameter is. From the point of view of strength, you could halve the number of spokes provided that each spoke is twice as strong.

If we now consider the rim loading.

The spokes also have a role in stabilizing the rim. If we look at it from rim strength alone, the first order factor would appear to be spacing so if you halve the rim diameter you could halve the number of spokes (Each spoke would still have to be twice as strong though)

If we consider deflection in the spoke

Assuming that each spoke has the same stress (force / cross-section) then the strain (Deflection / length) will be proportional to length. So if you have half as many short spokes that are each twice as strong and each carries twice the load, they will stretch half as much and you won't need as much preload to prevent movement at the ends of the spokes.

Deflection of the Rim should probably also be consdered but I'm too sleepy to think that through.



The bottom line appears to be that you can use fewer spokes on a smaller wheel but if you do, they each have to be stronger.

David

I ride with 16 on both my small wheeled bikes and have had no problems. Rims and hubs were both 32h and you do encounter certain issues when spoking if halving the spokes because of the way the holes on the hub are offset by half the distance between the holes. But they're good and solid and seem plenty strong enough for me, even if I'm only a diminutive fella. (5'5"; +/- 145 lbs)

Just thinking about this leads me to say that a smaller wheel will require less spokes. Extrapolate to extreme examples and think about it - say a 12 foot diameter wheel and a 12 inch diameter wheel, both with say 36 spokes. The tiny wheel will be almost solid spokes, while the giant wheel will have spokes very far apart and supporting a much larger structure that is getting much more torsional stress.

I think this group has the most experience with small wheels, so I ask it here.

Do we really need 32 or 36 spokes on the smaller wheels we ride? Doesn't the smaller diameter result in less stress on the spokes?

I'm thinking of building up my own 349 mm wheels, but am considering just using 18 or 16 spokes. I like the minimalist, cleaner look. Is that silly?

Hey SC,

I usually try to keep the spoke to rim size ratio the same. For instance, on the commuter I have a 36 spoke wheel on the rear. So when going to an ERTO 406 wheel, I would solve the following: x/406 = 36/622 to get x ~ 24. Of course, a constraint is the number of holes on hubs and/or rims. You can, obviously, do a 36-hole hub to a 36-hole rim, only using every other hole to get 18 for a 349 wheel.

The boss' Bike Friday has a 36 hole hub laced to a 24 hole rim. I recall that I posted some pictures in the past. I can take more and send them to you if you wish.

-IH

I've a fair amount of small wheel experience after 20+ years on recumbents.

Rarely do I use a full compliment of spokes. I've learned a few things along the way, usually by doing it wrong first.

Always use and skip spoke holes at the rim in pairs
skip 2-use 2-skip 2-use 2
or
skip 2-use 4-skip 2-use 4
or
skip 4-use 2-skip 4-use 2

Use the lightest spokes and stiffest rims possible. Spokes don't break because of too much load, they fatigue from going through loose-tight-loose-tight cycles. It's almost impossible to keep a 14g short spoke so tight it will always be stretched when you are skipping holes.

Heres a few of mine, all 406.

24 spokes on 36h rim and hub. I gave up getting the lacing right with 24, so I laced up all 36 spokes, X2 and then took out 12.
http://www.bikesmithdesign.com/temp/24spoke-rear.jpg

16 spoke X1 gives a very nice looking wheel
http://www.bikesmithdesign.com/Paul/16x1wheel.jpg


This one used a Velocity AeroHEAD, about 2/3 the weight of an AeroHEAT. Has thousands of miles on it with no maintenance.
http://mnhpva.org/Meetings/Apr_02/MSStuff.jpg

Early on I built a racing recumbent wheel with 12 spokes on a light Sun M13 rim. Spokes were 14 Ga and I used every 3rd hole. It lasted through 2 seasons, but because I couldn't put much tension into the spokes I had to re-true it often.

We have 18 radial on the from of our Moulton without any trouble.

Another option is to use spokes long enough for a crossing pattern, but only put the trailing spokes on one side and the leading spokes on the other. Builds a fine long lasting wheel.

I've a fair amount of small wheel experience after 20+ years on recumbents.

Rarely do I use a full compliment of spokes. I've learned a few things along the way, usually by doing it wrong first.

Always use and skip spoke holes at the rim in pairs
skip 2-use 2-skip 2-use 2
or
skip 2-use 4-skip 2-use 4
or
skip 4-use 2-skip 4-use 2

Use the lightest spokes and stiffest rims possible. Spokes don't break because of too much load, they fatigue from going through loose-tight-loose-tight cycles. It's almost impossible to keep a 14g short spoke so tight it will always be stretched when you are skipping holes.

Heres a few of mine, all 406.

24 spokes on 36h rim and hub. I gave up getting the lacing right with 24, so I laced up all 36 spokes, X2 and then took out 12.
http://www.bikesmithdesign.com/temp/24spoke-rear.jpg

16 spoke X1 gives a very nice looking wheel
http://www.bikesmithdesign.com/Paul/16x1wheel.jpg


This one used a Velocity AeroHEAD, about 2/3 the weight of an AeroHEAT. Has thousands of miles on it with no maintenance.
http://mnhpva.org/Meetings/Apr_02/MSStuff.jpg

Early on I built a racing recumbent wheel with 12 spokes on a light Sun M13 rim. Spokes were 14 Ga and I used every 3rd hole. It lasted through 2 seasons, but because I couldn't put much tension into the spokes I had to re-true it often.

We have 18 radial on the from of our Moulton without any trouble.

Another option is to use spokes long enough for a crossing pattern, but only put the trailing spokes on one side and the leading spokes on the other. Builds a fine long lasting wheel.

Now, THAT's what I'm talking about. Nice looking wheels! Thanks for the encouragement. I think I'll go for it.

http://lh6.google.com/geofgee/Rp7U5-a87bI/AAAAAAAAAHo/3132xcPYDiU/s400/front%20wheel%2024H.JPG

Here is the 24 hole rim and 36 hole hub I discussed earlier.

I've a fair amount of small wheel experience after 20+ years on recumbents.

Rarely do I use a full compliment of spokes. I've learned a few things along the way, usually by doing it wrong first.

Always use and skip spoke holes at the rim in pairs
skip 2-use 2-skip 2-use 2
or
skip 2-use 4-skip 2-use 4
or
skip 4-use 2-skip 4-use 2

Use the lightest spokes and stiffest rims possible. Spokes don't break because of too much load, they fatigue from going through loose-tight-loose-tight cycles. It's almost impossible to keep a 14g short spoke so tight it will always be stretched when you are skipping holes.

Heres a few of mine, all 406

....

Another option is to use spokes long enough for a crossing pattern, but only put the trailing spokes on one side and the leading spokes on the other. Builds a fine long lasting wheel.

Quite interesting. Thanks for the post.

Can't send any of the pics of my wheels b/c I'm away, but you can always just pick up 355s from Black Dog. Not sure what kinds of hubs he has available, but those wheels are built with 36 hole hubs laced 24 spokes to 24 hole Alex rims. The rims are about the same weight as the Aeroheat, and in my very limited experience, seemed to be built better (no blip at the seam at all). The advantage of this approach is that the rims won't have extra holes in them. But make sure you like Schwalbe tires or you'll be ordering from Japan!