Spokes for rear wheel folding bike.

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Brucey
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Re: Spokes for rear wheel folding bike.

Postby Brucey » 8 Jan 2021, 2:14pm

Mick F wrote:Just a question regarding interlacing or not on 20" (406) wheels.

It won't be long, and I'll need to replace the rims on my Moulton TSR. …….replaced a couple on the rear where they broke at the nipple......

When I next build them up, should I interlace or not??


If you are re-rimming (using the extant spokes) then keep them as they are, provided the rate/consequence of breakage is acceptable to you.

If you are using new spokes and want them not to break, you presumably need better angles into the nipples and/or better setting/stress-relief. You may find it easier to set/stress-relieve each (short) spoke if the crossings are unbraced, since they can be done individually, whereas with short spokes they tend to act as a pair when the crossings are braced, and are less easy to handle.

BTW if you are worried about nipples unscrewing themselves then some kind of soft threadlock will usually do the job. However this won't stop you from riding around on a wheel where all the spokes are too slack, which if it happens, is a pretty bad thing.

cheers
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iandusud
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Re: Spokes for rear wheel folding bike.

Postby iandusud » 8 Jan 2021, 2:20pm

fausto99 wrote:As far as I'm concerned, it looks better and feels stronger. I think radial spoked wheels will always "wind up" to some degree and I don't like the idea of that, even though I used to have an AM7 with radial spoking on the front and that felt OK. IMO, you don't want any "wind up" on the rear drive side or with disc brakes so radial there is a no-no.


I don't see any problem with radial spoking on a front wheel where there's no torque delivered from the hub to rim (unless with disc brakes). However longer spokes will give more compliance, as will DB spokes, which will give a less harsh ride and give the wheel an easier time IMO. Of course this a moot point on a Moulton front wheel with its suspension. The point you make about "wind up on the drive side" is an interesting one. Surely the torque is delivered from the hub to the rim from both the drive side and the non drive side.

iandusud
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Re: Spokes for rear wheel folding bike.

Postby iandusud » 8 Jan 2021, 2:24pm

Brucey wrote:it is probably fair to say that the suspension gives moulton wheels an easier time of it than many others of that size/configuration. 28 spoke moulton wheels -if built well- seem more than up to the job.

cheers

That is a very fair point re suspension. Moulton wheels are very rigid.

Brucey
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Re: Spokes for rear wheel folding bike.

Postby Brucey » 8 Jan 2021, 3:31pm

Needless to say you can build small wheels with DB spokes and these should confer exactly the same kind of benefits as in larger wheels. However the extent of such benefits become reduced along with the wheel size. So there may not be as much 'stretch' as you would like, whether the spokes are PG or DB, and the weight savings of DB spokes are similarly reduced vs PG ones in small wheels.

So in a full size wheel the wheel can be a better wheel and substantially lighter in weight when DB spokes are used, but fewer/much shorter spokes in smaller wheels mean that any benefit arising from the use of DB spokes is rarely as much as half that in larger wheels. Balanced against this is that getting hold of short DB spokes (of a quality which is worth having, anyway) is less easy and more expensive than longer DB spokes.

My MO is to cut and thread spokes for small wheels, which means PG or SB ones are the ones I usually use.

cheers
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fausto99
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Re: Spokes for rear wheel folding bike.

Postby fausto99 » 9 Jan 2021, 10:09pm

iandusud wrote:...The point you make about "wind up on the drive side" is an interesting one. Surely the torque is delivered from the hub to the rim from both the drive side and the non drive side.

Well, no matter how good the hub material is, there is no such thing as infinite stiffness, so the non-drive side will never get the full force from the other side. i.e. the drive side will be doing the bulk of the torque transmission.

Brucey
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Re: Spokes for rear wheel folding bike.

Postby Brucey » 10 Jan 2021, 1:21am

IIRC Brandt calculated the stiffness of 3x36 DB spoking vs a Campag LF hubshell and the %age torque would be expected to be shared about 75:25 in that case. However that is about as torsionally flexy a hubshell (vs standard spoking) as you can imagine, having large flanges built near-tangent vs a skinny centre barrel. To my mind this means two things;

1) the torque will be shared more evenly than that with similarly (tangent or near-tangent) spoked flanges in most other cases (because pretty much any other hub design you can imagine is liable to be more torsionally stiff than that vs tangent spoking), and

2) the torque split is liable to be almost completely one-sided if the spoking has very low torsional stiffness on one side.

The torsional stiffness of spoking is (I believe) likely to be asymptotic to zero, as full radial (rather than slightly angled) spoking is approached. So if you have one flange tangent spoked and the other flange radial spoked, the torsional stiffness of the radial spoking is always going to be 'very small' by comparison with the torsional stiffness of the hub barrel and/or the tangent spoking, so regardless of which side of the hub is tangent spoked, that will be taking pretty much all the torsional loads (*).

There have been commercially built wheels where the DS rear spokes have been set radial, and the NDS spokes set tangent, so all the torsional loads pass through the hub barrel. The wheels are presumably built like this because the bracing angle of the spokes is slightly improved this way. I suspect that it works best if the hubshell is torsionally stiff; however it doesn't have to be "infinitely stiff" for the tangent spoked flange to take nearly all the load, just much stiffer than radial spoking, i.e. more than zero; hardly a big challenge. Ironically the Campag 'HiLo' hub would benefit from this spoking pattern, but the hub itself is not very stiff in torsion and I have never seen one built this way. It seems not to have been in the minds of those who advocated this hub design, anyway.

[* said the radial spoked flange to the tangent spoked flange; "are you winding me up?".

A: "Yes, always".

Now, where's my coat...?...]
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iandusud
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Re: Spokes for rear wheel folding bike.

Postby iandusud » 10 Jan 2021, 7:42am

fausto99 wrote:
iandusud wrote:...The point you make about "wind up on the drive side" is an interesting one. Surely the torque is delivered from the hub to the rim from both the drive side and the non drive side.

Well, no matter how good the hub material is, there is no such thing as infinite stiffness, so the non-drive side will never get the full force from the other side. i.e. the drive side will be doing the bulk of the torque transmission.

Whilst I totally agree that no hub hub is infinitely stiff I find it hard to believe that the DS of a small flange hub will be doing the bulk of the torque transmission, although I'm happy to be proved wrong.

iandusud
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Re: Spokes for rear wheel folding bike.

Postby iandusud » 10 Jan 2021, 7:47am

Brucey wrote:1) the torque will be shared more evenly than that with similarly (tangent or near-tangent) spoked flanges in most other cases (because pretty much any other hub design you can imagine is liable to be more torsionally stiff than that vs tangent spoking), and

2) the torque split is liable to be almost completely one-sided if the spoking has very low torsional stiffness on one side.

This I think is reasonable and is a good argument for not building rear wheels with radial spoking on either side IMO. Having said that the radial spokes on the
NDS side of a 17" Moulton wheel do very little other than stabilise the rim laterally.

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Mick F
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Re: Spokes for rear wheel folding bike.

Postby Mick F » 10 Jan 2021, 1:34pm

This has got me interested in spoke patterning for my 406 Moulton wheels when I renew the rims.

Front wheel is 28h SPV8 hub dynamo.
Can this take radial spoking with 406 CR18 rims?

What about radial spoking on the NDS with the rear hub, a SA 3sp CS-RF3?
Mick F. Cornwall

grufty
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Re: Spokes for rear wheel folding bike.

Postby grufty » 10 Jan 2021, 1:48pm

Mick F, SJS do radial spoking on a rear wheel NDS for Brompton, so presumably it should work for Moultons?

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531colin
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Re: Spokes for rear wheel folding bike.

Postby 531colin » 10 Jan 2021, 3:42pm

Not all hub manufacturers "allow" radial spoking; ie it will invalidate your warranty.

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Mick F
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Re: Spokes for rear wheel folding bike.

Postby Mick F » 11 Jan 2021, 11:03am

531colin wrote:Not all hub manufacturers "allow" radial spoking; ie it will invalidate your warranty.
I'm aware of that, but I've not found anything written down about alu SA 3sp hubs or the SP dyno hub.

Any clues?

They're both 2x at the moment.
Mick F. Cornwall

iandusud
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Re: Spokes for rear wheel folding bike.

Postby iandusud » 11 Jan 2021, 11:14am

Mick F wrote:This has got me interested in spoke patterning for my 406 Moulton wheels when I renew the rims.

Front wheel is 28h SPV8 hub dynamo.
Can this take radial spoking with 406 CR18 rims?

What about radial spoking on the NDS with the rear hub, a SA 3sp CS-RF3?


Out of interest where did you get your SP 28h 100mm OLN hub? I'm thinking about building up a dynohub wheel for my Moulton but the only 28h dynohubs I can find are Son, which are too expensive for my taste. I can find SP 28h in 74mm OLN for Bromptons but not 100mm.

thanks, Ian

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Mick F
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Re: Spokes for rear wheel folding bike.

Postby Mick F » 11 Jan 2021, 11:18am

My SP came from Spa.
https://www.spacycles.co.uk/m20b0s133p4 ... YNAMO-PV-8
Comes in 24, 28, 32 and 36h.
Mick F. Cornwall

Brucey
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Re: Spokes for rear wheel folding bike.

Postby Brucey » 11 Jan 2021, 11:18am

28h here

https://spacycles.co.uk/m20b0s133p4336/SP-DYNAMO-PV-8

you can of course build a 28h rim radial onto a 32h or 36h hub, if you want.

cheers
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