How to properly mount the driving wheel on a bottle dynamo

[MsMellie]

Hello everyone,

My bicycle is an ancient Victoria and it has a Desmos bottle dynamo. This dynamo and I are often at war and I was messing around with it and had to take off the driving wheel when cleaning something. Now, the driving wheel is like a cap. It sits on a nut that is screwed onto the dynamo's axle (idk if that the right word for it) and it has a nut above it that holds it from slipping off. This is how it used to be but I can't seem to put it back properly. If I tighten either of the nuts the wheel can't even move and if I leave them loose it spins, unscrews the top nut and just flies off. I can't get pictures right now, might add later, but is there any advice anyone can get me? Really mad I messed this up and I need the thing.

Thanks a lot in advance and sorry if that sounded like rambling!

[Jdsk]

The photos will help!

If I tighten either of the nuts the wheel can't even move and if I leave them loose it spins, unscrews the top nut and just flies off.

I'm not sure if the problems occur when you reassemble the dynamo and try to spin it, or only when you flip it so that it engages with the bike's wheel... ?

Jonathan

[MsMellie]

It occurs when I try to reassemble it and engage it.

[Jdsk]

If you reassemble it and don't engage it with the wheel does it spin happily?

Thanks

Jonathan

[MsMellie]

Nope, it doesn't. When I spin the driving wheel it spins for a second and then blocks, as if it is clamped by the two nuts holding it. If I try to spin it in the wrong direction it screws itself and the nut above it right off the dynamo. I have no clue how I managed to mess it up.

[Jdsk]

Thanks.

I'd like to see a photo of the components laid out next to each other, and especially any washers and spacers.

Any more information on the model or a serial number, please?

Jonathan

[MsMellie]

Okay, I can get some photos but it might take time 'cause I don't have a phone or a camera that I can transfer from quickly. As for the model, it is a Desmos dynamo, made in Germany. When I get the photos I'll check if there's any info on the model or on the power/voltage.

Thank you for your help and quick replies

[tatanab]

Slacken top nut. Screw the drive wheel down by hand as far as it will go, then slacken off half a turn. Grip the drive wheel tightly with something like molegrips or pliers and then tighten the top nut hard onto the drive wheel. If it is still too tight, then loosen off and slacken the drive wheel a little more.

The whole thing is just like a nut plus a locknut. I do not know the Desmo brand specifically.

[MsMellie]

Thanks, I will try that ASAP! Will let you know what happened.

[Paulatic]

Did you have a spring under the wheel when you took it apart?

[MsMellie]

No, no spring. Just a nut and a thin washer under it.

[Carlton green]

I’m not familiar with your particular dynamo but make observations and comment from my own experiences.

My Union bottle dynamo caps have a screw thread running through them and are held in place with a locknut (the ‘nuts’ lock against each other). Occasionally I will remove the drive wheel for cleaning and to add a bit of light oil (not three in one) to the shaft. On replacement I put (screw) the pulley on and do so with it the correct way up. I screw it down to finger tight and then back off say 1/2 a turn, then I firmly hold the pulley and secure the lock nut against it.

Perhaps your drive pulley does not have a thread and is somehow keyed to the shaft. If so then maybe it’s being replaced upside down or you’ve lost a spacing washer.

I hope that that’s a help.

[MsMellie]

That does seem reasonable. I wrote all of your suggestions down and will try them out when I go down to the garage.

[MsMellie]

Hey everyone, checking in to let you know its fixed! Driving wheel is on nice and normal and everything works. I followed instructions that you all gave me to the letter so thank you! Learned a new thing today. On the side not, I misread my dynamo info (my bad, it is scratched off mostly). It is a DAIMON No 833/6V/3W Made in Germany. It looks a lot like this fella on eBay: https://www.ebay.de/itm/284805803859?ha ... SwlWZiYuq0

[Jdsk]

Well done.

Great advice.

Jonathan