Friday, November 13, 2009

Yuba rear hub: final technical detritus

The Yuba rear hub is done and this post has been a long time coming. It is brought to you by a good beer and a spare Friday night between baby-related carpentry projects. So here's the rear hub setup in all its glory, a Halo SpinDoctor Pro DH hub with 14mm axle adapters. By the numbers:

48 spokes
4 sealed cartridge bearings
10mm hollow chromoly axle
30-point engagement, 3-pawl chromoly freehub
9-speed cassette

Yuba Rear Hub Final 2.JPG

Yuba Rear Hub Final 3.JPG

A few words are in order about fitting this part. First: BTI (the distributor for Halo parts stateside) finally has the part numbers for the axle adapters straightened out, thanks to my badgering. You should be able to walk into your local bike shop and order this hub and the adapter and gets the right parts. I received two sets of 14mm adapters for a front hub before I got the correct part. It didn't help that I ordered from a mail-order place in an attempt to save some cash so I had to do all that crap by phone.

Part of me hates to do this because I worked in bike shops for most of a decade and I know what they go through, but I need to call this place out. you need to work on your resolution skills. These guys run a real brick-and-mortar shop specializing in hardcore dirt jumping, DH racing, and BMX. I'm sure that if you walk in with a busted part, you'll leave with exactly the overkill solution you were hoping for. However, here's a few tips for your mail-order business:

Call back when you say you'll call back.
Only say you have a part in hand when you actually do.
Don't send the same wrong part out twice, it suggests you don't know what you sell.
Don't take phone orders if you have no system to track phone orders.
Pick up your phone during your posted business hours.

Anyway, about the hub.

It's loud. Not quite Chris King angry-bee-sound loud, but loud enough that it reminds you that you could be pedaling instead of coasting. I like this. I try to make every other part of my bikes silent, so the freewheel and the tire noise are the bike's voice. This is a big bike, and it's okay for it to have loud voice.

The engagement is fast. 30 engagement points is more than standard and it's nice to be able to put the pedals where you want them to start up a hill from a stoplight with a 100lb load.

The axle is hollow. I know, right? It's supposed to be a DH hub and they make a design decision that can only be justified for its weight savings. WTF?

It's strong anyway. Maybe a solid axle wouldn't help? I'm a chemist, not a mechanical engineer, but I might buy some hand-waving argument that it doesn't really matter that much beacause of the relative cross-sectional area and the surface tensile-str... blah blah blah. I've put 350lbs+ on it (me and Katie plus some cargo) for decent stretches and it's fine. I also tried to bring home a 14" band saw with it, but 250lbs on one side and nothing on the other just made the bike unrideable. I got every thing strapped on and laid the bike down a couple times trying to get started, but the whole bike is fine.

It's wider than the Yuba rear spacing. The Yuba is 130mm, the hub is 135mm. You'll need to stretch the frame to get it to fit. Luckily the Yuba has big-ass H-racks such that you can lean the bike over, stand on one H-rack, and pull up on the other (lift with your legs, not with your back) to get enough spread to fit in the hub.

It is much more nicely made than the Yuba frame. As anyone who's put together a Yuba from box will know, that's not saying too much. These frames are built like tanks and ride like Cadillacs, but examples of precision manufacturing they ain't. The assembly instructions include hammering the H-racks into place! I had to take a file to the rear dropouts to get the 14mm axles to fit into the frame. Most of what I took off was paint, but a little steel was removed as well. I enjoy free-hand metalwork, but others might care more. Incidentally, more filing around the rear dérailleur was needed to allow proper clearance for the spring tension adjustment screw. This can be seen in the second photo above. Most of what I took off there was steel. The chunk of sheet steel that is the right rear dropout isn't cut to close enough tolerances to allow for a standard Shimano LX dérailleur without some filing.

I really like this hub. It does its job, it's simple, it's familiar technology, and it's compatible with whatever industry-standard parts you want to use it with. Also, it has 14mm dropout adapters, even if I'm the only person in the world who cares. Seriously, what frame with 135mm rear spacing also has 14mm dropouts? Luckily for me (and anyone else who wants to run a standard 9-speed drivetrain on a Yuba) they made it anyway.

Recently A Long Walk to Green posted a long-term review of his NuVinci CVT hub. I think if I'd read that before I built the bike I would've gone that route even though it involves modifying the frame for use with a 10mm axle by brazing spacers into the dropouts. I considered it at the time, and even tried to get an answer from the manufacturer on the hub's load rating. I didn't get an answer back for weeks and by that time I'd already built the bike, but they said they'd never tested it for load. Seems to work for him, though.

I'm happy to have the Halo hub, it's a good part. It's a viable option for custom Yuba-builders who want to run a modern geared drivetrain, and fits the dropouts without frame modification.

1 comment:

Justin said...

Nice. I forgot you worked at a bike shop for a long time. When do you plan on taking build commissions? :)