Hub dynamos for 20" wheel

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AM7
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Re: Hub dynamos for 20" wheel

Post by AM7 »

NUKe wrote:does the Moulton have narrow hubs ? This will determin which ones 70mm or 100 mm.


Some of the New Series Moulton's take 74mm OLN front hubs, but the AM, APB and TSR models are all 100mm.
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Mick F
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Re: Hub dynamos for 20" wheel

Post by Mick F »

Yep.
100mm front.

The rear was a compromise on my TSR, as it was 132mm.
Means a squeeze for a QR and a 130mm rear hub, or a stretch for a QR and a 135mm hub.

I squashed mine to 130mm as it was what I wanted for any hub. It took a good deal of engineering, but I squashed it perfectly and symmetrically. That 2mm was the best 2mm that I've done. :D
Mick F. Cornwall
alexnharvey
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Re: Hub dynamos for 20" wheel

Post by alexnharvey »

Bumping this old thread with a similar question

I have a shimano xt 6v 3w dynamo that is intended for larger wheels. Marked 646-716mm. I'm thinking of building it into a 406 rim and also considering if it would be better to use one of the 1.5 or 2.4w Shimano hubs, or a 3w one that is marked as suitable for a smaller wheel?

On lacing. The bike has disc mounts so I'd like to lace it accordingly although they won't be used initially. I was thinking of 2x, single butted 13/14g spokes as I can't get double butted spokes in that length. The spoke holes are quite small though so might have to go with 14g plain.
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RickH
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Re: Hub dynamos for 20" wheel

Post by RickH »

alexnharvey wrote:On lacing. The bike has disc mounts so I'd like to lace it accordingly although they won't be used initially. I was thinking of 2x, single butted 13/14g spokes as I can't get double butted spokes in that length. The spoke holes are quite small though so might have to go with 14g plain.

I've got a Circe Helios tandem with an Alfine 36 spoke rear hub (I don't know off the top of my head how the flange size compares to a dyno hub) & disc brakes on 406 rims. It has been fine laced 1x as supplied despite the extra strains of being the rear of a tandem that gets ridden off road quite a bit. I did toy with switching to 2x but decided that the spoke angles would increase bending at the nipples so decided to stick with what I knew was working OK.
Former member of the Cult of the Polystyrene Head Carbuncle.
Brucey
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Re: Hub dynamos for 20" wheel

Post by Brucey »

-1x for a disc brake front wheel is pushing it a bit. 13-14g is overkill for spokes so I'd use 14g (or even 15g on a rim-braked wheel) unless there is some compelling reason not to.


If you use your extant hub with a small rim you will get some combination of more drag/more power at lower speed.

Really the only good reason for not using x3 spoking is the angle of the spoke as it comes into the nipple/rim, vs. the capacity of the nipple to swivel in that particular rim, so this is really a question about wheelbuilding and/or the type of rim that you use, I'd say.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
alexnharvey
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Re: Hub dynamos for 20" wheel

Post by alexnharvey »

Thanks both. It is for a Circe Helios tandem. Mine is also laced 1x on the original wheels. After previous discussions I was thinking of using the Andra 40 rim that Brucey has recommended before for its hole drilling. Is that sufficient to allow 3x?
I might go for 14/15g single butted. Iirc even 3x didn't quite get me to sufficient length for double butted spokes.
Brucey
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Re: Hub dynamos for 20" wheel

Post by Brucey »

ah, it is for a tandem? And you are thinking of using an Andra 40 rim?

Then PG 14 or SB 13/14 or PG 13 would be appropriate.

In any event you will need large diameter nipples, either 13G nipples for 13G spokes, or rim13/spoke14 converter nipples, because the rim is drilled for 13G spokes.

The whole reason for that rim's existence (with its angle drilling) is so that you can build x2 or x3 onto reasonable sized hubs, for load carrying bikes.

I would suggest that you get your hands on the rim before choosing the spokes.

FWIW Sapim make 'race' DB spokes down to 135mm. Finding a stockist for them is a different matter though.

cheers
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rjb
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Re: Hub dynamos for 20" wheel

Post by rjb »

In case anyones interested here's a link to my 20" wheel with a sturmey dynohub.
viewtopic.php?t=95614
Looking at the date it's been almost 4 years without a problem. :D
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
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