spoke spacing.

need to increase number of spokes in 26" bike wheel.

plan is to fit a kids 10" wheelrim in middle with extra spokes in and use a bigger hub and double up number of spokes between that and outer rim.

what's best way to work out spacings?

thinking maybe a strip of card layed out flat and then work it out and tape it on for drilling?

all cos i told my boy it looked interesting idea when we were sorting out bike spares and he laid small wheel on bigger one.

Are you not fond of your boy, such that you want to kill him? It's a silly idea and I would strongly advise against it. There is no way that you could build a wheel strong enough using this scheme. Just leave it as "an interesting idea" .

i do actually love my boy.

and i resent the being accused of not doing so.

he wants to do it as an exercise in doing it neither me nor him are stupid enough to consider using it,

it is purely to see how it would be done and if it could be done,

Don't see how the spokes will pass through the smaller rim the dishing will mean the spokes pass the outside of the smaller rim rather than through it.

Just draw a simple triangle 13 high and the width of your hub flanges say 4" now draw a 1" wide line to represent the smaller rim 5" from the hub and the slope of the triangle won't pass through it.

Knowing a bit about building bikes, if the spokes go from the hub to the smaller rim, then from the smaller rim to the bigger one, you will almost certainly never get that to run true.

Building a strong and true wheel is all about triangulation of the spokes to hub, and a rear wheel is offset to allow for the cassette, I would say it would be almost impossible to get it to work, and you would spend a lot of time achieving something that won't work.

Wheel building is an art, that isn't easy to achieve, and I certainly wouldn't start this way.

Edited By David Standing 1 on 11/05/2018 17:02:38

i have built normal wheels but nothing like this.

plan is to use 2 sets of spokes smaller rim spoked. and then spoke from smaller rim outer as on a hub to rim of bigger rim

Back to the spacing. Yes a strip of paper works but you still have the problem of marking the right number of holes / spacing without ending up with a half a space at the end. It is the same as dividing for making unusual gears which you might be able to look up. A common method is to use a perforated strip, eg builders strip then cope with the diameter not fitting your wheel by packing with cardboard before marking.

So per my post then.

I don't believe you will get a rigid (triangulated) wheel built in this fashion, nor get it to run true, nor get it to run concentric.

Let us know how you get on, I am happy to be proved wrong.

David i highly suspect you are right.

my son is autistic and once gets idea in head it's sometimes better to let him run with it if possible.

so want to give it a go so he can satisfy his curiosity more than anything.

Mick

Ah, that's different, and I understand entirely why you want to give it a go.

Still going to be a lot of work though!

Mick

I can see now why you wanted to try it - and I had no intention of doubting that you love your son.

I've built a few wheels myself over the years and so know a little about them. As they are a highly-stressed and safety-critical item, it would be most unwise to risk his well-being by fitting a wheel that I believe would be fundamentally flawed in its integrity. Perhaps I phrased my comment badly, but I am deeply concerned that you are proposing something which you might regret if it goes - well, I suppose "pear-shaped" would be an adequate description.

My thought is that if built well it would work in theory, but there could be practical issues. The 'gotchas' are that using spokes of 1/2 length they will be many times stiffer and that may well make the wheel brittle and easily damaged, unless they are steeply angled and that the relatively narrow spacing of the small wheel's outside flanges that provide outer 'hub' may not give enough stability against side loads. The 'dishing' of spokes is absolutely critical to the wheel's strength.

Neil

i know nothing about wheels, but i like your curiosity, if you are not going to use it as a wheel would your son settle for a polished sold band between the inner rim and outer rim which could be customised in some way, just a thought

sorry shouldn't have fired off like i did.

can be over protective when comes to my kids.

and react first then think

it is being done as a can it be done project with him.

won't be used on a bike unless he puts it on one to see what it looks like but def not ridden.

know what you mean about wheels though had two done by cycle shop few years ago that bent on me so done my own ever since.

Edited By mick70 on 12/05/2018 09:17:55

Am i to understand that you will use the flange part of the rim of the smaller wheel to mount the spokes for the larger wheel? That would seem to be the only way it would work. Technically there would appear to be no problem doing it, as long as you can get the holes drilled in the correct locations. One issue will be the crossover of the spokes, assuming you are using crossed spokes for the outer rim and not radial. With the shorter spokes they will be stiffer and so you will probably find it hard to cross over more than once, so the outer rim will not be as rigid as one having two-cross or three-cross spokes. Also the rim of the inner wheel would not be as rigid as the hub of a normal wheel, so it will flex more leading to greater difficulty in tensioning the spokes and getting the outer wheel to run true.

Still, it would be possible and an interesting exercise for your son to pursue. Let us know how he gets on.