AN INTERESTING KANSAS HPV

From the editor: Having a special interest in homebuilt HPVs -- not that there's anything wrong with manufactured ones -- when I saw Eric Farnsworth's "for sale" ad for his "unique front wheel drive recumbent" in Recumbent Cyclist News, I e-mailed him seeking information for an article. He was nice enough to write the following (slightly edited) and also e-mail photos and the drawing of his hub. Eric lives in Lawrence, Kansas.

Thanks for your interest and attention to the RCN classifieds. Don't worry about not being interested in actually buying the bike, I realized that most people wouldn't be, and it only required one buyer. Which I found, so all ended happily. The bike is chain driven, using a live axle hub with the bottom bracket incorporated and coaxial with the wheel -- if that means anything the way I've said it. Surely in the HPV world, you have had ample opportunity to mull the advantages of a front-wheel-drive-vehicle, while trying to minimize (or ignore) the disadvantages.

I had been wondering for a while how to do something like this. The obvious simple solution is to do a direct drive, using a unicycle wheel. Of course you only have one very low gear, or one very high bike.

My second thought was to do some kind of internal gearing, but no matter how hard I tried, I couldn't come up with a way to modify an old 3- speed hub, and I don't have the machining resources to build one from scratch.

So that left me with the standard deraileur gearing. If you follow the drawing and photo, it should make sense. Both wheels are 700c (27-inch.)

I had to make my own axle, which is not that hard to do if you don't mind using old cotter-type cranks. Just start with 5/8-inch ground rod and grind flats in the appropriate places for the crank pins. Since this is a live axle, you'll need bearings between it and the frame. These are the outer bearings on the drawing.

What I did on the bike, but didn't draw, is run a chain from the crank chainring to an intermediate hub, which then drives another chain that turns the hub, for a total of 12 speeds. On my drawing, I've only just shown the thread where the gear cluster mounts. So now you will have your hub moving at a different speed than your live axle, and you will need another pair of bearings between the hub and axle.

Coincidentally, you will end up with a fairly heavy fork with all kinds of stuff hanging off of it, and some prickly chain line issues. But I couldn't think of another way to do a multiple speed front-wheel-drive, since I'd rejected the rear-wheel-steering option early on. Having built a rear-wheel-steering trike, I've found that they're a real problem.

The bike doesn't/didn't have more than 12 speeds because of chain line issues. The short distances and tight spaces prevented me from using the full range of either deraileur. There was even a certain combination that caused the two chains to interfere with each other - unsurprisingly.

Of course this design could be used on either an upright bike or recumbent, but I decided to make mine a recumbent for the obvious reason that chain length and handling is much more of an issue with a recumbent, so more of an advantage is to be had with front-wheel-drive. There is a photo of an upright trike using this same system (as far as I could tell from the photo) on www.velomobiling.net . Look in the ice racing gallery. I think it's in the one from 2005. I am working on a cargo trike very much like that right now.

But there were plenty of other handling problems to deal with. I don't know what experience you've had riding wacky geometry bikes, but surely you know that recumbents are a bit more of a challenge to ride than uprights. The same is true for bikes with long fork rake angles, and especially true for front-wheel-drive bikes. This bike combined all three. So it was exciting to ride, at least partly because it is so low to the ground.

I think I had it up to about 25 mph or so. Which felt plenty fast, certainly for this bike which was kind of heavy and clunky, but it was fun to ride once you got used to it.

The FWD cargo trike I'm building now will have one chain on each side of the front wheel, using a bottom bracket as the intermediate axle; with some custom made parts for mounting gear clusters on the square taper spindle. Hopefully, this should help untangle the chains.