As our 300 lb. team has gotten stronger, we've been doing ever more ambitious rides. This summer we had in mind to take the tandem up into the mountains. We have Avid 7 V-brakes, and they've always been fine, even loaded touring, in ordinary rolling terrain. But I wasn't comfortable taking precious Stoker down 4000' descents with just the rims. Plus they do wear out and that's expensive, too.
Our sport rear wheel has a Chris King hub, and they don't come threaded, so I built a second rear wheel. I bought a used Arai drum brake on ebay and married it to a White Industries 36H hub with a Deep V rim and 14-15 DT spokes. I control it with a Shimano 8-speed bar end shifter mounted to the right captain's bar, and set to friction mode.
Yes, the wheel is heavy. Our kitchen scale says just a little under 5 lbs. with cassette, tire, tube, and skewer, whereas my sport wheel weighs 3 lbs. 3 oz. on the same scale, same condition.
We've done two rides in Mt. Rainier National Park with the new wheel. The Park roads are not steep at all, only 4%-6% grades, but the descents are long. The brake worked perfectly. The best thing is that it's butter smooth. I can't tell it's on, other than the bike goes slower. That does great things for stoker confidence, because I don't have to be constantly on and off the brakes.
I set it for the highest speed I feel like attaining, in this case 35-40 mph, and then use the V-brakes normally for the corners. On the Park roads, we were fast enough that cars didn't show up behind us, and controlled enough to steer around the bad stuff. Stoker loves the brake. I think we could ride just fine with only the rim brakes in that terrain, but I prefer the drag brake and will run it in the future for those sorts of rides, and for any loaded touring.