I just called my LBS looking to buy a Nexus generator hub, and apparently the 36-hole model has been discontinued. They have the old, high-drag model in 36h, but the new one is now 32 only.

This is for a tandem that gets used for commuting, grocery-getting, and maybe touring someday, so it seems like 36 spokes is a minimum. The Schmidt dynohub comes in a 36 (or 40) hole version, but it's prohibitively expensive ($250 vs $90 for the marginally less-efficient Nexus).

Does anyone know where I might be able to get my hands on one?

The Sturmey XFDD drum brake and hub generator comes in a 36 hole version. Running a dual cable brake lever on your tandem should give you a nice increase in braking power, plus the power you're looking for from the generator.

How does the Sturmey hub stack up in terms of weight and efficiency? We do ride this bike longish distances and I don't want too much drag from the hub slowing us down. The extra braking power would be nice, though.

The older Nexus NX-30 also comes in a 36-hole version, but I'm steering clear of it because of the poor efficiency and high drag even when the light is turned off.

Peter White Cycles has the 36h version DH-3N71 hub.
So does Harris Cyclery. Harris Cyclery is just down the road from you in West Newton.

Harris is the LBS I mentioned in the first post. They have the 36-hole hub on their website, but it's not in stock and they can't get any more.

I'll try calling Peter White, though. Maybe he has one left in stock.

If he doesn't, let me check with my LBS and see what they've got. I might be able to pick one up and ship it to you, if necessary.

I know your wanting a hub dynamo and they are nice but you might consider a bottle or BB type dynamo. There is a little more drag from these types when being used but the drag is not very much more and when disengaged there is no drag at all. If you commuted several hours every night a hub dynamo would be a worthwhile investment and I would not quibble about the price of a Schmidt. With Just an occasional use of the dynamo a bottle or BB type would do you fine. Considering it's going on a tandem you can use touring tires with bottle dynamo sidewall tracks molded in the rubber so sidewall damage from the dynamo wheel would not be a problem.

The Sturmey is supposed to be using the same Sanyo internals as the modern Shimano dynohubs, so it should have comparable efficiency. Given that it also has a drum brake, it weighs about 300g more, or nothing you should notice on a tandem.

Peter White doesn't have them either, but he said he hopes to have more soon. He didn't really elaborate on whether or not they're still in production (the guy is quite terse on the phone). So I may wait and see if he gets more in.

Since he lives in Boston, I wouldn't suggest a friction driven dynamo. Between the rain and snow, I think there would be a lot of slippage issues.

I just checked in with Peter White again. They were able to find some of the 36-hole Nexus hubs and should have them in a couple weeks. But it sounds like the hubs have been discontinued, so I don't know if they'll be able to get any more.

If anyone else is in the market, now's your chance. I placed my order already.

Cool! Glad that he was able to locate one for you.

I'm holding out until I've saved up for a SON28B for my Cross Check.

How about the SRAM i-Light? It's as effective as the Shinamo and the SON when on, but a bit less when off. It's available for 36H too, has many brake options, and usually as expensive or less expensive as Shimano's.

I'd completely forgotten about the i-Light. But it seems to have pretty high drag with the light turned off (almost as much as when it's turned on, in the numbers I found). Not a big deal for commuting, but on long rides those extra few watts probably add up.

It has indeed as much drag when off, but if you're like me and you always have it on because of the tunnels and such, it shouldn't really bother.

Sram just launched some extra hubs, so I-lights are available at loony prices right now (sadly, with $$ shipping). The new one (ILight D7) is lighter. The UN-71 has just been replaced, so that might explain some of the supply problems. Check out ebay.de and type in Nabendynamo if you want to see what you are missing

Yeah, for commuting it's probably not a big deal -- on my single commuter bike I don't really notice a difference whether the light is on or off. But our tandem is kind of a do-everything bike (because tandems are too expensive to have more than one), and we use it for long rides on the weekends, too. So I think it's worth a little extra money for the reduced drag.

Of course the Schmidt hubs are the best as far as drag, but that's more than a little extra money, so I'm glad I found a Nexus.