Dynohub Difficulties
 

Now that school's out and I've got some time to pick up on the 1951 Raleigh Clubman project I started back in September, I'm puzzled by the GH6 Dynohub. Two questions for the learned:

1. Now, in that thread, Cudak and Sciencemonster both said that the magnet should cause "surprisingly little drag." Well, that doesn't seem to be the case -- the drag is quite strong. It takes quite a bit of strength to turn, and the wheel will immediately stop spinning if I stop turning it by hand. I thought it might be the bearings, but I've taken the thing apart according to the SA manual, and the bearings, cones, and cups look great. The major friction is between the magnet and the armature. What could be causing this? Could it be missing a spacer or something? I haven't separated the magnet from the armature, so I don't know whether the Magnet Spacing Ring or the Patent Number Disc are intact. Is there a way to lubricate the magnet/armature?

2. The manual I've been able to find shows a diagram for the 1952+ dynohub, but gives directions for the slightly different pre-1952 dynohub. Does anyone know where I could find a diagram for the earlier model? Going by the written directions, it appears that a "shim washer" might be missing -- but I have no idea what that shim washer might look like, or how wide it would be,etc. This might be related to problem #1. Any ideas?

Thanks a lot,
Brian

Hey, I want updated photos! Best I could find was here, which is... well, tantalizing! Lovely bike, at any rate.

When you turn a dynohub axle by hand, it feels terrible. That's normal. There is increased resistance as the magnet and coil come together, but the energy lost in that moment is almost immediately returned with a push as they separate again. Are you sure this isn't what you're experiencing?

But you say the wheel stops immediately when spun. Really immediately? If so, that's definitely a problem, more of a problem than I can help you with. I saw a NOS dynohub magnet and keeper for sale on ebay a few months ago, kinda wish I'd bought it.

Are you feeling 'friction' between parts, or the resistance caused by the magnet?

A dynahub will _never_ spin free - it's got a big heavy magnet in it, sticking to the armature. In the end, since the magnet both pushes AND pulls as it spins, the 'net' drag is very little. Once you get spinning, it evens out.

If you are talking about about friction - a scrapping type friction, then that is something different.

Which is it?

I had the same problem, plenty of oil in the hub, but not wanting to turn well. I broke it down, and packed the axle bearings with grease, shot some WD-40 onto the magnet-armature area, reassembled and added oil, problem solved. I feel it was grease on the axle bearings, as the bearings were covered with oil. Now it will spin like all get out!

What does it feel like when you ride it? My GH6 has a pretty heavy drag when you are just spinning it by hand and stops pretty fast when you stop spinning it. It isn't noticeable at all when I am riding it.

Mine arrived the same way-- had some corrosion/rust where the armature and the magnet met, along with a lot of dried up old grease. I cleaned it up as best I could and added some lithium grease, with a little motor oil mixed in (to get the grease to flow into the small spots). It helped. I also replaced all the bearings. This combination brought the hub back to life and made it a decent rider. I built it into a Westrick rim with stainless spokes.

Once built the wheel should spin freely, but there will be just a hint of drag to it still. They're never totally frictionless, though properly tuned they have little friction.

Turning by hand is deceptive. You should reach the point when turning by hand where the operation turns smoothly (smoothly being the key). I would describe the feel of turning by hand as "smooth hesitation". What you don't want is to turn it and feel "grinding" or hear grinding. But turning by hand, you needn't have it so that it turns as freely as a normal, plain hub. The idea is to minimize the friction as best you can, and to ensure there is not "grinding" going on.

When it's built up, the hub spins pretty smooth - but when you just have the hub in hand, it doesn't turn easy at all. Or at least, that's what I found with the four hubs I've built up. The magnet has a lot of grab.

Hey, thanks, guys. This at least gives me the courage to ride on it and see how it goes. So, in consensus, it's OK (and even a good idea) to put some kind of oil/lubricant on the magnet? This one is very clean -- it shows no sign that ever had any kind of oil outside the bearing cups.

One more question, for those who have pre-'52 GH6es: on this one, both cone locknuts are thick (about 3/8" thick) chromed nuts, exactly the same as the axle locknuts (instead of the thin, flat ones in the diagram for the post-'52 model). Was that the way they were built?

I don't remember exactly what was on mine, but I know it did not match the diagram either. I have a 51.

I rebuilt a '64 and it felt like the cones were tight and the bearings were binding, so much so that i took it to my LBS to have him check it out before I destroyed it. The confirmation was that I was feeling the magnet and coil, It's been on the bike for over a year now, I don't even notice it's there.