Non-standard spoke issues and purchase

[Geoff.D]

I'm in the middle of adding a motor to my front wheel. The motor came with a 26" rim, but I want to match it with 700c. So, I stripped out the spokes, and am about to order a new set. But, I've never built a wheel before, so (at the moment) all my knowledge is through what I read (mostly on these forums, but elsewhere, too).

The stripped out spokes appear to be 2.3mm (13 gauge), but the rim is drilled for 2.0mm (14 gauge). I have three questions -

1. I read that many front electric hubs use a single butted 13/14 gauge spoke, and this is the optimal choice for the strength/flexibility relationship. Any comments on this?
2. I notice that the elbow length on my stripped out spoke is greater than the elbow length on some old spokes I have knocking around (14 gauge, I think). But, I've practised using 3 of the on-line spoke length calculators (discussed by Brucey in December) and they make no mention of this measurement. I realise it isn't a variable in the spoke length calculation, but I do need to get it right when I order. How do I specify this length?
3. Do you have any recommendations as to suppliers, bearing in mind that I'm looking for (possibly) non-standard spokes with 13/14 single butted and a longer elbow?

I posted this initially in the Electric Bike forum, but it's a technical question that bridges both.
Many thanks, in anticipation.
Geoff

[Brucey]

the J-bend length is most certainly a variable to be concerned with but it usually isn't specified. I would suggest that the fit of the spokes in the hub is improved using spoke washers where necessary.

You can have a choice of using

- cut down and rethreaded 13/14g single butted spokes, or
- PG 13G spokes with slim-bodied converter nipples in a rim drilled for 14g or
- a rim that is drilled for 13G spokes

The options are roughly in order of suitability for increasing severity of duty.

With a front wheel motor, I would counsel caution; not every fork is strong enough to withstand a motor flapping around on the end of it, or indeed reliably withstand the torque reaction of the motor. On the latter point there are a lot of pretty crappy (dangerous) motors out there.

BTW building a wheel isn't difficult but building a good wheel with a motor in it is. IME it is quite normal for motor wheels built only averagely well to pretty well fall apart after a relatively short period of use.

cheers

[catsnapper]

Hi Geoff,

Justin at http://www.ebikes.ca have an online e-bike spoke calculator http://www.ebikes.ca/tools/spoke-calc.html that enables a wider range of calculations. It might look a bit too complex at first look, but it has been well thought out and works well.
I've built many e-wheels using standard 2.0 mm and 2.3 (or 2.35!) mm spokes,but Sapim Strong 2.0/2.3 are the ideal choice.

Catsnapper

[Geoff.D]

With a front wheel motor, I would counsel caution; not every fork is strong enough to withstand a motor flapping around on the end of it, or indeed reliably withstand the torque reaction of the motor. On the latter point there are a lot of pretty crappy (dangerous) motors out there.


cheers

Thanks for your response, Brucey. I note all your suggestions. With regard to your caution about the strength of the fork, you may recall that I posted about this issue at the back end of the year and you expressed that concern at that time. I took it on board and feel that I've come up with a solution. It may be of interest to you from an engineering point of view.

I decided that I'd go with a fork from a modern hybrid bike - chunky steel, with a welded crown. I discussed it with a neighbour, who is an engineer for one of the F! racing teams that has an HQ in my area. He felt that the weakest point in the structure was the bolt hole that sits between the fork welds onto the steerer tube. He happens to also restore old motorcycles as a hobby, building fuel tanks from scratch and other fabrications. He took the fork and fabricated a plate across the front of the crown, welding from fork to fork and across the top, shaping it to fit whilst hot. He shaped it under the crown, and welded it there, too. He did the same at the back, integrating a mudguard bolt. The two "plates" become effectively a single shroud around the crown.

He's very skilled and the finished article is extremely neat. It was waiting for me when I got back from Scotland at the beginning of the week. I haven't caught up with him yet, because he's away. But, with his permission, I'll post photos.

By the way, I was in London before Xmas. There were plenty of front hub driven bikes and conversions. It did seem to me that a 1" steerer tube is not uncommon.

[Geoff.D]

Hi Geoff,

Justin at http://www.ebikes.ca have an online e-bike spoke calculator http://www.ebikes.ca/tools/spoke-calc.html that enables a wider range of calculations. It might look a bit too complex at first look, but it has been well thought out and works well.
I've built many e-wheels using standard 2.0 mm and 2.3 (or 2.35!) mm spokes,but Sapim Strong 2.0/2.3 are the ideal choice.

Catsnapper

Thanks for this, Catsnapper. I'd read that Sapim 13/14 were the good ones. I'm reassured by your experience.
On a quick trawl, I'd only come across an American stockist. I need to explore some more. (Edit:- found some UK suppliers - problem solved)


(PS Have you snapped any cats recently? In my house it's the cat that does the snapping!)

[catsnapper]

Hi Geoff,

If you have a problem getting Sapim Strong spokes I've got some in stock (also 2.3mm plain DT Swiss). Length doesn't matter as I have a Morizumi cutting and threading machine. Takes a few days from here in Spain to the UK.

PS: The catsnapper name was dedicated to a favourite tiny, stray cat who adopted us. Long legs, large mouth, she spat and snapped at any other animal whatever size or shape!

Catsnapper

[Brucey]

FWIW I can get Sapim Strongs cut and threaded locally using a Phil Wood machine, if you draw a blank elsewhere.

cheers

[Geoff.D]

FWIW I can get Sapim Strongs cut and threaded locally using a Phil Wood machine, if you draw a blank elsewhere.

cheers

Nice offer. Thanks.