carrying charge from hub dynamo

General cycling advice ( NOT technical ! )
User avatar
simonineaston
Posts: 8003
Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

carrying charge from hub dynamo

Post by simonineaston »

As my new build begins to take shape, another decade-long bugbear (not exactly sure what one of them is...) may be addressed, to wit how to pass the charge from the dynamo in the front hub to the bits that need it. I see a tempting hole at the base of both fork legs. At the same time, my mind turns to the way that car electrical systems used the chassis as the ground - do they still do that? As most cars are now effectively computer-controlled, they must need high-quality electrical stability... any comments, you sparky-type people?
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: carrying charge from hub dynamo

Post by Jdsk »

Yes, cars still use the body as earth/ return. There is some non-conductive gluing where there would have been welding, and a lot more digital stuff and a fair bit of multiplexing, but there's also lots of simple traditional analogue circuitry.

Jonathan

PS: Most (if not all) electric-only vehicles have a traditional low-voltage battery and circuitry in addition to the main drive system.
Last edited by Jdsk on 5 Aug 2020, 5:49pm, edited 1 time in total.
User avatar
simonineaston
Posts: 8003
Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

Re: carrying charge from hub dynamo

Post by simonineaston »

I guess I'm thinking out loud really, but I was wondering if there is any advantage to using the cycle frame as ground and I guess the answer is a loud NO for the simple reason that whatever you connect will have to be supplied by at least one wire, so it makes no sense to use the frame as ground 'cos you might just as well use a pair of wires as one.
Never-the-less I would like to get rid of the traditonal wire "wrap" of the fork leg, just for once, by passing the wire up inside...
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
User avatar
Mick F
Spambuster
Posts: 56359
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: carrying charge from hub dynamo

Post by Mick F »

On here about it before and was given advice.

Providing you have a breather-hole top and bottom of the fork leg .....................

Pass a double loop of thin fishing wire down from from the top hole to the bottom hole by the dropout.
It won't come out, but with a piece of wire or a pick, pull the loop out.
Thread a bit of thin string through the loop and pull the fishing line out and the string will come through the top.
This means you then have a string right through the fork leg.

Connect a nice long length of your preferred electrical twin-core to the string, and pull it through.

This works a treat, I promise ................. but you need breather holes top and bottom of the fork leg.
Mick F. Cornwall
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: carrying charge from hub dynamo

Post by rjb »

I use my frame as part of the circuit on my dynamo equipped bikes so i can manage with a single wire to the lights. My lighting is often diy and i have never had any problems with the arrangement. You will have to earth the lights so have to ensure correct polarity if you have led lighting which is polarity sensitive. :wink:
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
User avatar
simonineaston
Posts: 8003
Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

Re: carrying charge from hub dynamo

Post by simonineaston »

a single wire to the lights
So what would you say are the advantages of the single wire? I can see that a single wire is potentially thinner, and therefore fit in smaller holes, but I can also see that a thin wire is more at risk of damage...
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
User avatar
Mick F
Spambuster
Posts: 56359
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: carrying charge from hub dynamo

Post by Mick F »

No advantage of a single wire.

If you use one, the earth return has to be fitted onto bare metal at either end.
No bare metal on my bikes thank you very much! :shock:
Mick F. Cornwall
User avatar
simonineaston
Posts: 8003
Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

Re: carrying charge from hub dynamo

Post by simonineaston »

Mick F wrote:No advantage of a single wire. If you use one, the earth return has to be fitted onto bare metal at either end.
No bare metal on my bikes thank you very much! :shock:
That's rather what I thought - there's not supposed to be any bare metal on mine, either - except for the patches where Pashley's cheapo powder coating has flaked off! :roll: Thank goodness for my ancient tin of Hammerite!
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: carrying charge from hub dynamo

Post by Jdsk »

Threaded bosses?

Jonathan
User avatar
simonineaston
Posts: 8003
Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

Re: carrying charge from hub dynamo

Post by simonineaston »

Threaded bosses?
Yeah but - aren't they full of bolt?
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: carrying charge from hub dynamo

Post by rjb »

Theres lots of places on a bike which are not painted. Alloy racks, bolts which attach brakes are useful sources for a front light fitting. And has been stated most threaded bosses will earth via the attachment bolt. :wink:
If you check for continuity using a multimeter it may surprise you. :wink:
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
tatanab
Posts: 5033
Joined: 8 Feb 2007, 12:37pm

Re: carrying charge from hub dynamo

Post by tatanab »

The disadvantage of using the frame for the return current is that if you are running a front wheel dynamo or a fork mounted light with a rear dynamo then the return path is through that nice greasy, dirty headset. Possibility of problems. For example of how bad this can be in automobiles - just look at the number of old cars where the rear lights go off when the brake lights come on or the indicators are set. This is due to dirty connections to the car for the return. Of course, using the frame for the return has served generations of cyclists perfectly adequately, but I would not consider it ideal.
Jdsk
Posts: 24639
Joined: 5 Mar 2019, 5:42pm

Re: carrying charge from hub dynamo

Post by Jdsk »

simonineaston wrote:
Threaded bosses?

Yeah but - aren't they full of bolt?

I don't use the frame as a conductor, but if I did... ring terminals?

Jonathan
scottg
Posts: 1218
Joined: 10 Jan 2008, 8:44pm
Location: Highland Heights Kentucky,, USA

Re: carrying charge from hub dynamo

Post by scottg »

backnotes wrote:https://www.peterwhitecycles.com/schmidt-sl.php


Way too easy, not the CTC way. :)
+++++++++++++++++++++++++
Deutsche Luftschiffahrts-AG
+++++++++++++++++++++++++
Post Reply