Dynamo help please.......

[Grarea]

OK, so, I have decided to give a dynamo hub a try. Thanks for all the input in the other thread.
(I can't decide if I am happy or not that my old lights have given up.)

I have read through a bunch of pros and cons on them vs battery lights and I like the pros.
I am also less bothered by the cons.

It really is a tight call.
I keep swinging back one way then the next.
Main issue is cost.
Both the relatively low total cost of a dynamo system and the surprisingly high cost of battery lights when you don't want to get squished by a vehicle.

Well, what has swung it is the fact that I have never tried a dynamo set up. They seem pretty good these days.
Well, I say swung me, I am not positive, but I am slightly leaning that way.

So, I generally think(And have been proven right enough times) 'buy cheap, buy twice.'
Also the residual value of a better 'thing' is generally better.

However, I have no money.
But I need lights.
I prefer to think long term.

So, looking at things, I need to decide on the hub, the rim and then the lights. (The following is a bunch of thoughts)
Buy separate and get built or buy ready made? (The former might be tricky as I only have two wheels (With and without an engine) although I am sure I could strap it to something for transport) I have never built a wheel.
New or second hand?
Where to buy?
If I was going battery lights, I would be thinking two on the back, one flashing, one solidly on.
So, we can switch them on and off then can we? So, they have capacitors. So, can i switch the dynamo off and leave the lights on when I go uphill to help me out?
I want 26", disc brake and 6 bolt.
Rims, I don't know much about. I have had Mavics and never had problems with them. (Ideally I would like black )
I would like them to be able to take a bit of light off road (A bit more than gravel tracks) and a few heavy pot holes.

Anything else?




So, hub first:
It seems to me that they are all 6v and 3 watts output.
So, that all seems to be a standard now.
I assume then, that it is all about resistance?

I kind of need all the help I can get with this, I have enough slowing me down
So, how do I pick a hub without trying them all out?
Does this make some sense?
https://www.cyclingabout.com/dynamo-hub ... b-testing/
Or will i not notice any difference?

The SP PD-8 / Shimano DH3n80 / Alfine etc etc etc
Are the cheap shimano ones just cheap?

[meic]

A hell of a lot to answer there.

It seems to me that they are all 6v and 3 watts output.

No they are just starting to make lower power ones now, so when find an XT which is cheaper and less drag than you were expecting, check you have not accidentally come across one of them instead.

If you are going to leave this dynamo on your bike for all of your riding pay more attention to the lights-off drag figure, the SON was noticeably better than the Shimano on that point.

Some dynamo reviews from a man with his own opinions here.
https://swhs.home.xs4all.nl/fiets/tests ... ano_dh3n80

An out of date report from SON which predates the new Taiwanese SPs, in German but the graphs are useful for comparing Shimano and SON.
http://www.nabendynamo.de/service/pdf/ar_09-10_2010.pdf

[crossy]

Hi I've just bought a Dynamo wheel from Decathlon for £35 posted I'm using it most days with lights and also play around with charging external battery, gps and phone not all at the same time but it does well. I use an Axa 70 lux USB I charge my gadget from that and run a busch muller rear light that has a stand light on it so it stays on when I stop.

[[XAP]Bob]

So, hub first:
It seems to me that they are all 6v and 3 watts output.
So, that all seems to be a standard now.
I assume then, that it is all about resistance?

I kind of need all the help I can get with this, I have enough slowing me down
So, how do I pick a hub without trying them all out?
Does this make some sense?
https://www.cyclingabout.com/dynamo-hub ... b-testing/
Or will i not notice any difference?

The SP PD-8 / Shimano DH3n80 / Alfine etc etc etc
Are the cheap shimano ones just cheap?

There is one additional way to go in two phases - get the lights, and run them on existing batteries - I've used a PP3 quite effectively.

The differences are well discussed around the forum...
viewtopic.php?f=5&t=69317&hilit=dynamo

Brucey has a number of rather good threads on the topic.

[mjr]

Buy separate and get built or buy ready made? (The former might be tricky as I only have two wheels (With and without an engine) although I am sure I could strap it to something for transport) I have never built a wheel.

I've done both, but buying ready-made is much faster and slightly cheaper at the cost of restricted wheel choice. Eventually when the rim or spokes wear out, you'll probably have to get it built into a wheel anyway.

So, we can switch them on and off then can we? So, they have capacitors. So, can i switch the dynamo off and leave the lights on when I go uphill to help me out?

Yes, you can switch them off if either your front light has a switch on it (and you're happy to reach it) or you wire a handlebar switch into the circuit (I use a Lucas-style dipping switch with nothing on the dipped part). It'll keep the lights on a while, but it'll be a parking/stopped light which is usually rather dimmer than full power - but you might not need that except on the steepest hills.

Anything else?

Enough wire to reach the back light, maybe. That surprised me first time, but maybe it was just a bad choice of back light on my part. I've used medium-weight 2-core speaker wire on recent rewiring jobs, which IIRC is completely OTT for the power carried but very easy to work with. Cable ties and tape to, er, tie and tape the cable to the bike somewhere (mostly along the back brake cable outer if you have such a thing).

[Brucey]

less than £20 for a hub

https://www.sjscycles.co.uk/dynamos/shimano-dh3d37qr-6v-30w-quick-release-centre-lock-disc-dynamo-front-hub-silver-36-hole/

which you will need to use a converter with if you want to use a non-centrelock disc.

lights-on drag is much of a muchness across many generators but lights-off drag varies with hub model. The best SON models measure ~1W and the shimano ones vary from ~1.5W to ~3W depending on model and who is doing the measuring. I suspect that some of the drag and the variations in same are down to tight seals in new hubs; in ad-hoc run down tests some shimano hubs have performed very well and 1-2W would be my estimate of the typical drag.

To put it into perspective this amount of drag is a tiny fraction of the drag from the tyres and will have an insignificant effect on speed. You could induce more drag than this by having one tyre 5psi soft.

A good value lightweight generator is the SP-PD-8 (or PV-8 for rim brakes) which is £65 or £60 depending on model, from Spa cycles

cheers

[meic]

So, can i switch the dynamo off and leave the lights on when I go uphill to help me out?

When you are going uphill, you are also going very slowly and at that speed the drag from the dynamo is heading towards zero and being well and truly undetectable alongside the effort of climbing.
More of a worry that the dynamo is no longer providing any electricity to keep the capacitors from running flat if the hill goes on for too long.

[Grarea]

Excellent stuff, cheers for this guys.

A hell of a lot to answer there.

And a hell of a lot of info back at me in super quick time.
I have zero experience with these and I don't know what I don't know, so I thought I would splurt everything out.
Glad I did actually, some great stuff straight back.

Hi I've just bought a Dynamo wheel from Decathlon for £35 posted I'm using it most days with lights and also play around with charging external battery, gps and phone not all at the same time but it does well. I use an Axa 70 lux USB I charge my gadget from that and run a busch muller rear light that has a stand light on it so it stays on when I stop.

Wow, really? That really is cheap. What one was it?
Do you notice the drag?
Sounds like it does the job. Any negatives that you have found?
I didn't find anything that low.
I guess it is likely to have a shorter life span than the others.

[crossy]

Hi still on Decathlon website it is a Shimano dh-3n30. My thought is I'm a slow rider anyway so if I'm a bit slower it won't make any difference to me. I kept the old wheel so if needed be I can refit that. The bike is a Raven Thorn so heavyish any way. I can't comment on how long it will last. I think I had the hub before on another bike and that lasted me for 1000's of miles.

[Paulatic]

I quite agree if you buy cheap you buy twice. If money is a problem I think I would buy buy cheap on the dynamo. Don't worry about the drag up hills as said elsewhere it really isn't noticeable. It might only give you 2or 3 yrs by which point you can upgrade. Also you can put your old wheel back in for the summer if you don't need lights.
Buy decent lights now and you'll fit them and never need to touch them again. I thoroughly recommend the B&M rear light with standby. Gives a lovely wide appearance so all that's needed. Comes with long enough wires to get to the front too.
Front there's plenty to choose from which aren't too dear at all.

[Grarea]

Chuckle.

I am so glad I asked.

That cheap hub/wheel has thrown a spanner in the works.
(I am also slow, but I am inclined to think more like I need all the help that I can get )

Also "save money on the hub......" that was another curve ball, I wasn't expecting that.

Buy the lights now and the hub later ....

All great thoughts.

Sounds like I am less likely to notice the difference than I thought.
...... although at the teeny weeny energy I output ........

I did consider keeping and swapping my old rim.... or actually, I have another old rim brake rim out there .....
But anyway, yes, I reckon best to get one premade.
Also, yes, I reckon keep the current one.

Right, time to look at some links and ponder stuff.

[PeterBL]

less than £20 for a hub

https://www.sjscycles.co.uk/dynamos/shimano-dh3d37qr-6v-30w-quick-release-centre-lock-disc-dynamo-front-hub-silver-36-hole/

which you will need to use a converter with if you want to use a non-centrelock disc.

Wow, great price for a disc dynohub!

[gaz]

Or will i not notice any difference?

Last year I finally dipped my toe into the dynohub waters, Shimano DH-3N31.

Riding on a smooth flat road with the lights off, can I tell the difference between the lights off and my previous non-dynamo hub, no. So much so that I have left the dynamo hub on the bike throughout the summer months when it's not needed.

Riding on a smooth flat road with the lights off, I can feel the additional drag if I switch them on. It's not much, but it's there. However it's somewhat of a ridculous test, I only feel the additional drag because I have just added it. In practice I don't notice the difference between riding the bike to work with the lights off and riding it back home with them on.

[[XAP]Bob]

Given the almost ridiculously low cost of the lights and hubs...

I'd splash out - you're just not going to save much by running a battery rear, or a bottle/battery over a hub (that's the questionable one).
Get the best front light you can afford, get a rear light with some width to it, get a £35 wheel...
If it had disc fittings I'd be sorely tempted to get one, and resell my (as yet unbuilt) hub...

[hamster]

I took the plunge a couple of years ago for my tourer, Shimano XT with Axa Luxx 70 lamp.
Overall I'm very pleased with it - I opted to build the wheel up myself onto an existing barely-worn rim.

The only time I miss the powerful Fluxient battery light I use off-road is downhill in unlit lanes.
The only thing I would do differently is to lace the front wheel 2x instead of 3x as the spoke angles off the rim don't look that clever.
USB charging is a bit hit and miss - the USB connector into my phone is a bit tetchy and jumps out. Nowadays I use the dyno to charge a battery pack, which is then used for phones etc. It's a little less efficient, buy my stupid phone insists on waking itself up every time the charge is interrupted, such as at junctions. It then consumes extra power that can result in a net zero re-charging result.

Do it! You won't regret it.