36hole rims, what happened?

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Brucey
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Re: 36hole rims, what happened?

Postby Brucey » 20 Jan 2016, 2:52pm

Bigdummysteve wrote:
Brucey wrote:I think that if you don't choose such a 'fashion driven' rim design, you can have as many 36h rims as you want. cheers


Not so much fashion, I'm building up a surly ECR which is designed around 3" tyres. I'm not convinced that a 35mm rim of which there are a few available will provide enough support.

These appear to be the only easily available wide 36 hole 29" rims http://www.unicycle.uk.com/29-kris-holm ... e-rim.html
Unless any one has anyone has any other suggestions.


OK, I see what you mean, I agree a low pressure 3" tyre won't be supported very well unless it is on a wide rim. I'm still wondering if it is a fashion driven rim though... :wink:

If you were using a 2" (or smaller) tyre, I'd argue that a 36h hub would be a better choice, strength/rim-selection wise.

The unicycle rim looks good but if push comes to shove and you are stuck with a 32h rim you could

- buy a new hubshell for your rohloff...? or
- build a 32h hub onto a 36h shell, using a multitude of different spoke lengths (not easy...ask me how I know.... :shock: )

cheers
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Bigdummysteve
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Re: 36hole rims, what happened?

Postby Bigdummysteve » 20 Jan 2016, 3:47pm

I have considered getting the Rohloff re-shelled, bet it's expensive.

Brucey
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Re: 36hole rims, what happened?

Postby Brucey » 20 Jan 2016, 5:03pm

well there is this

https://philwoodco.wordpress.com/2011/02/16/36-hole-phil-wood-hub-shell-for-rohloff-hub/

again not cheap I'm sure.

I note with interest that the design appears to favour a dishless wheel over a dished one, even if the flanges are very close together. I'm not sure this is a smart move if you are using a single-wall rim.

I guess buying a spare shell means you can get more bang for your rohloff buck; you could have the other shell built up into a wheel for use in a different bike as and when the whim takes you, requiring only that you swap the internals into the other shell.

cheers
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MartinC
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Re: 36hole rims, what happened?

Postby MartinC » 21 Jan 2016, 8:33am

Brucey wrote:.................. note with interest that the design appears to favour a dishless wheel over a dished one, even if the flanges are very close together........................


Slightly off topic but I've always wondered how this trade off works in practice. You can always reduce dish by moving the left flange inwards but it must reduce the lateral stability. Hope hubs which can take either a Shimano or Campagnolo cassette do this. It makes the spoke tensions more even but the left hand spoke angle isn't so good.

pwa
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Re: 36hole rims, what happened?

Postby pwa » 21 Jan 2016, 9:22am

I didn't realise Rohloff hubs came in a 36 hole form. They used to be available only in 32 hole. SJS don't seem to offer 36h, only 32h.

Brucey
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Re: 36hole rims, what happened?

Postby Brucey » 21 Jan 2016, 10:59am

MartinC wrote:
Brucey wrote:.................. note with interest that the design appears to favour a dishless wheel over a dished one, even if the flanges are very close together........................


Slightly off topic but I've always wondered how this trade off works in practice. You can always reduce dish by moving the left flange inwards but it must reduce the lateral stability. Hope hubs which can take either a Shimano or Campagnolo cassette do this. It makes the spoke tensions more even but the left hand spoke angle isn't so good.


I think it all depends how (torsionally) stiff the rim section is. If the stiffness is low (and/or the rim isn't straight to start with) the spoke tension is limited by the wheel self-tacoing (Euler buckling). I recently repaired a wheel with an SA hub brake in it and a (slightly bent) single-wall rim and I would have used more spoke tension in it if I could have done so. As it was the wheel was too close to taco-ing. If the tension is too low then the wheel will be laterally weak anyway.

So the answer may be that it can be OK with a rim that is stiff enough. There is a benefit in terms of the NDS spokes sharing the loads better and not being so prone to nipples backing out. However in the case of the Phil Wood hub I can't help but think that the larger flanges may increase the spoke angles at the rim which won't please everyone.

cheers
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wfbroddy
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Re: 36hole rims, what happened?

Postby wfbroddy » 22 Jan 2016, 8:41am

These make up a strong 29+ rim and are 36 hole
http://www.unicycle.uk.com/29-kris-holm ... e-rim.html

HTH

Samuel D
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Re: 36hole rims, what happened?

Postby Samuel D » 22 Jan 2016, 9:32am

Brucey wrote:If the tension is too low then the wheel will be laterally weak anyway.

Why is that? My understanding was that spoke tension didn’t affect lateral stiffness, though perhaps you mean something else by ‘weak’ here.

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CREPELLO
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Re: 36hole rims, what happened?

Postby CREPELLO » 22 Jan 2016, 10:52am

Cut your losses and sell the 36H hub and buy a 32H hub, giving you the choice you require. You should regain most of your investment as it's an unused hub. There should be plenty of folks here that would buy your hub to build into a conventional 36H touring wheel.

pwa
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Re: 36hole rims, what happened?

Postby pwa » 22 Jan 2016, 11:12am

CREPELLO wrote:Cut your losses and sell the 36H hub and buy a 32H hub, giving you the choice you require. You should regain most of your investment as it's an unused hub. There should be plenty of folks here that would buy your hub to build into a conventional 36H touring wheel.


36h must be quite rare, but I would guess that swapping would incur significant financial loss with such an expensive item.

Brucey
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Re: 36hole rims, what happened?

Postby Brucey » 22 Jan 2016, 11:17am

Samuel D wrote:
Brucey wrote:If the tension is too low then the wheel will be laterally weak anyway.
<br abp="709">Why is that? My understanding was that spoke tension didn’t affect lateral stiffness, though perhaps you mean something else by ‘weak’ here.


I think spoke tension may affect lateral stiffness, because when the rim is deflected, it isn't just the spokes that are stretching; the rim bends too, and the rim is effectively supported (both radially and laterally) by the spoke tension elsewhere in the wheel. If the rim can bend easily, and the spokes are not very tight, the rim can deflect (sideways and inwards) without much increase in spoke tension elsewhere in the wheel.

When the spoke tension is too low, the rim sees much higher bending loads than normal (I've often seen rims in slack wheels fatigue in bending...) and the net work required to buckle the wheel (i.e. bend the rim) permanently is a fair bit less, thus up to a point the wheel is certainly 'weaker' with slacker spokes.

These things are somewhat less easy to see with many modern rims, but with older, more flexible rim designs, it is clearer what is going on.

cheers
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PH
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Re: 36hole rims, what happened?

Postby PH » 22 Jan 2016, 11:27am

CREPELLO wrote:Cut your losses and sell the 36H hub and buy a 32H hub, giving you the choice you require. You should regain most of your investment as it's an unused hub. There should be plenty of folks here that would buy your hub to build into a conventional 36H touring wheel.


Or find someone who wants a swap, I think the shells swap quite easily, though it needs to be the same finish.

Bigdummysteve
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Re: 36hole rims, what happened?

Postby Bigdummysteve » 22 Jan 2016, 7:06pm

wfbroddy wrote:These make up a strong 29+ rim and are 36 hole
http://www.unicycle.uk.com/29-kris-holm ... e-rim.html

HTH


Thanks for the input, do you have any experience of these rims? I think they are going to be the easiest option, swapping hub shells seems likely to be too expensive. As for swapping my hub or selling it my hub has 3000+miles on it now and in run in nicely,I've looked after it changing the oil etc so I'm keen to keep it. Thanks for all the suggestions, I think the unicycle rims look like the best option.
If your buying a rohloff 32 hole looks like the best option, given the life span of a rohloff and the possibility of taking it between different bikes it might give you more options in the future.

wfbroddy
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Re: 36hole rims, what happened?

Postby wfbroddy » 22 Jan 2016, 7:12pm

Yes I used them to build up a set of wheels on a Alfine8 hub for my..... ECR :o)

They built up well have been strong so far, they are a touch heavier than most other rims but that isn't an issue for me and have been bullet proof, used the ECR off and on road, an since they are a bit narrower than the Rabbit Hole rims a stock ECR come with, I think they give a better profile to 29+ tyres both Knards and Chronicles

Bigdummysteve
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Re: 36hole rims, what happened?

Postby Bigdummysteve » 22 Jan 2016, 7:33pm

wfbroddy wrote:Yes I used them to build up a set of wheels on a Alfine8 hub for my..... ECR :o)

They built up well have been strong so far, they are a touch heavier than most other rims but that isn't an issue for me and have been bullet proof, used the ECR off and on road, an since they are a bit narrower than the Rabbit Hole rims a stock ECR come with, I think they give a better profile to 29+ tyres both Knards and Chronicles


Thanks for the reply, I'm building up an ECR and will be running chronicles, out of interest have you run smaller tyres on the ECR? I know the bb height is quiet low, it was one if the plus points for me. I heard all sorts of dire warnings I suspect from people who have never ridden this frame, the main alternative tyre for me would be a big apple at 2.3" for road use. I suspect a big apple would make a nice road tyre on these rims?