Friday, February 10, 2012

Andrew's recumbent tandem

Hey Folks,

I 've ridden the new tandem enough to commit to the powder coaters.

I'm convinced the 2WD system is better for us than a linked timing-chain RWD like our previous tandems. Bron the stoker is much happier being in control of her cadence & I don't feel like I'm pulling her legs around. The jiggling from out-of-synch pedaling is novel but not a problem. It will get better as we pedal smoother. I have not noticed any pedal-steering tendencies & the bike is quite manageable even in granny-gear (19 gear-inches). FWD bikes draw some criticism for their potential to lose control when the front wheel slips (on gravel for instance). Under our 140kg weight I don't think it will be a problem & seems to be an advantage when piloting solo.

The limits of steering due to the twist-chain FWD set up are not an issue when riding, even in a U-turn. It is a small pain when we use a tight rail-crossing chicane on our commute. The short sections of chain-tube are crucial when using a mudguard & or fat tires - the chain will rub OK on a bare tire but it snags on the edge of the mudguard. The tubes make this a non-issue although they do lay against the mudguard when using the inner-most cassette rings. Under this condition some chain-noise is transmitted to the mudguard.

Despite the stronger frame & more efficient drive-train the bike is not order-of-magnitude faster like I hoped. It is noticeably easier to push but we don't seem to go much faster yet, maybe we'll get fitter with the resumption of our regular commuting. The stiffer frame makes the bike noticeably steadier going fast downhill. I think I did a better job with the steering geometry on this bike; it's lighter to steer - maybe the offset in the forks contributes here. I didn't calculate rake & trail, there doesn't really seem to be hard & fast rules as far as I can see.

The SRAM dual drive hubs are great, 27 gears each & all under our right hands. They are great for the 20" wheels, I'd have to use big (expensive) chain-rings if I used a regular front derailleur set-up. The just-as-expensive Dual Drives look neater & are nicer to use & maintain.

The other big improvement is the BB7 disc brakes, they are amazing especially compared to the V-brakes we had on the previous tandem. I went for the 203mm discs in case we decide to tour with this bike.

Hopefully I'll spend more time enjoying the ride on this bike rather than trying to work out how to improve the design.

Cheers, Andrew

Tradewinds Tandem combines a long wheelbase and short wheelbase recumbent together to form a speedy and comfortable vehicle for two. The Tradewinds Tandem frame is light and strong, and because the tandem is powered by two human engines, it offers many advantages over a single rider bicycle. Add to this the laid back aerodynamic seating position, and you have the formula for a very fast and efficient human powered vehicle.

The under seat steering is extremely comfortable as it places your hands in a naturally relaxed position, yet gives you confident control over the steering. The bottom brackets are placed lower than the seat, so you are pedaling in a relaxed position without having your feet obstruct the view. Because of the short wheelbase front configuration, the overall wheelbase of the tandem is quite short, allowing for easy maneuvering and responsive handling on urban streets. The Tradewinds is a bicycle for two, but it is completely rideable by only one, if for some reason the you have to fly solo.

Because the Tradewinds uses commonly available bicycle parts and some steel tubing, it can be built in a few days using minimal tools. Even if this is your first attempt at creating a custom cycle, you will have no problem following along since the steps are detailed along the way with 120 pictures and illustrations. You can also change the design to suit you own needs. The simple frame geometry is easy to modify. The cost of the completed tandem is not much more than the cost of a department store bicycle, if you decide to purchase new parts to complete the

Take a look at our Builder's Gallery to see other TradeWinds examples, including many creative modifications to the plan. Our international builders community ranges from students to retired engineers, but they all have one thing in common - the desire to build their own stuff!