A Series of Tubes: Xtracycle Long Tail with Stokemonkey Pedal Assist

 

 

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A Series of Tubes: Xtracycle Long Tail with Stokemonkey Pedal Assist

via Austin On Two Wheels by elliott on 10/12/09

"Bike building is a lot like the Internet. They both involve a series of tubes." Elliott McFadden,Violet Crown Cycles

In April during one of my first ventures to the Sunset Valley Farmer's Market with the Violet Crown Cycles tent, I met an individual who loved the look and functionality of my Ferguson city bikes but really wanted some form of electric bike. He initially asked me about a solar powered pedal assist option, but I indicated that I thought a drive train powered system would be much more efficient and economical.

We had an ongoing conversation over the next three months via the telephone and e-mail to narrow down the bicycle he wanted. Initially, he wanted a standard Ferguson bike with an internal hub and pedal assist. The first challenge we faced was combining the internal hub with a standard bicycle frame. There are pedal assist motors built into hubs, but they are currently always paired with a traditional external derailleur. Other systems use a secondary chain drive but require non-traditional frames to accommodate this system. After a bit of research, I recommended the Stokemonkey system produced by Clever Cycles, a Portland transportation cycling shop I visited last year.

The Stokemonkey was designed to work with Xtracycle compatible frames and Free Radical conversion kits. The customer was initially resistant to the long tail concept wanting as normal a looking bike as possible. I offered to build a custom rack on a long tail but suggested going with the Xtracycle platform as the company is always coming up with new accessories. This would give the customer a lot more flexibility to change the utility of his bike in the future (plus I'm a big fan of the Xtracycle.)

Once we settled on the drive train and long tail platform, it was down to the design. Fortunately, Xtracycle has made their design open source in the last year saving me much time in measuring everything out. Surly is the only company currently making a mass produced Xtracycle frame, the Big Dummy. I took a look at their design to see how they tackled the design issues, but ended up going my own way wanting a little more classically styled frame. My initial design involved a series of long double stays on the back, however one set of stays had to be replaced in the design with a single oversized tube to hold the heavy Stokemonkey motor and its brackets.

One odd bit from the Xtracycle design recommendations was the statement that horizontal drop outs in no way could be used with the design. Since I was going with an internal hub, this would be a bit of a problem meaning I'd have to put a chain tensioner on the bike. One of the reasons I like internal hubs is for the clean chain lines. I was using 26 inch wheels and since the design is meant to accommodate larger 700c wheels, there was plenty of room to put horizontal drop outs on this bike which I did.

I have to say I am quiet happy with the final results, but getting there was quiet a chore. I had estimated the build time would take about 50% longer than one of my normal bikes, but there was an awful lot going on with this bike and the build time on this bike took twice as long as estimated. Part of this was developing the system for building the rear of the frame. This was my first long tail frame, and I build my bikes without a jig (not that a conventional jig would have helped me.) My alignment table was just barely long enough for the frame which also became a little unwieldy to work with in my smallish workshop. I'm not in any hurry to start building tandems!

The customer opted for the midnight blue and had the chain guard, stem and fenders powder coated to match the frame. This yielded one of the better looking electric bike on the road (For some reason, the makers of e-bikes produce some of the ugliest bikes I've ever seen.) At first, I was a little nervous about installing the Stokemonkey system as this was my first e-bike. Luckily, the system is very straight forward with easy to understand instructions from the Clever Cycles site. Stokemonkey uses a second chain drive on the left side of the bike that engages when you turn the rev switch on the handle bars. The sensation is interesting, similar to that of a fixed gear bike. You feel the pedals continue to push even though you are no longer pressing the pedals. The entire red motor unit spins which is a little disconcerting at first, but the system itself is quiet and intuitive.

I let my wife take it for a spin around the block and she immediately started talking about getting rid of our car. She rides to work on an Xtracycle with my son on the back but has a hard time with the hills and longer trips. I think the Stokemonkey makes this more practical than standard e-bikes because it is paired with the Xtracycle platform meaning you can carry a weeks' worth of groceries and 1-2 children on the back. For those looking to go car free with children, I'd give the Stokemonkey/Xtracycle combo a serious look. As for myself, I will be adding both the Xtracycle frame and Stokemonkey to my Ferguson line options for those wanting more in transportation cycling utility.

 

 

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