Project View

New E-Life for Rental Tandem

Canada

330

Published: 2023-09-16

Tandem Bike

FH212/RH212

I bought a used Fiori tandem off a rental place for cheap, stripped it to the frame and rebuilt it into an e-tandem with an RH212 motor. E-tandems are great for harnessing regen power as there's the weight of two people but the wind resistance of one, while the RH212 is a big, torquey motor that allows for a lot of regen power. With these, I made a proportional regen system that operates right of the back brake lever.

Rebuilding Process

From what looked like a heavily-used rental tandem, the bike was stripped to the frame and resprayed to new.

Battered looking, well-used, but frame/fork and other bits were OK. — Original State

Couldn't resist putting the bits back together to see what it would look like. — Trial rebuild

I wanted torque sensing on this bike, but how would I do that for something with 2 people cycling? This proved to be one of the more challenging aspects of this project as you will see. — Torque Sensing Challenge

A few new coats and she's looking good! — Resprayed and ready

Rear wheel and cassette were well worn, so a new wheel was ordered from Grin, along with a new cassette. — Wear and Tear

Took the bike to pieces and sanded down the frame... — Stripped to bits

The E-bike Bits Go On

These are the go-faster ebike parts from Grin that I added.

52V 19Ah will take us over 100km of riding when charged full. — The Battery

The RH212 was powered by no less than a Phaserunner MT. — RH212/Phaserunner Combo

And of course, there is the trusty CA3 to manage all affairs on this bike. Note also the use of the 3 Position Switch (mounted upside down) for 3 preset settings. This proved to be really useful for the regen use, ironically. — Cycle Analyst 3

I decided to use an Erider torque sensor in the rear bottom bracket as this would measure the combined power of both riders going into the chainring. Unfortunately, the existing bottom bracket (an more importantly the crankset) was the splined type, so finding a left-side crankset (spider/arm) with a square taper was not easy. I ended up adapting a right-hand side spider/arm and re-tapping it with a heli-coil to make it left sided! With this, I re-installed the left side chain-rings from the original bike. — Erider Installation

A Grin Triple Bob was used to hold the large 52V 19AH battery onto the downtube of the frame firmly. — Triple Bob

The Unique E-Brake

Regen braking is particularly useful for e-tandems, because you have the weight of 2 people on it with the wind resistance of 1. If you have ever ridden a tandem downhill, you will know - it goes fast! With so much power to harness in braking, I have long dreamed of creating a proportional regen braking system that was somehow operated just like a regular brake lever. After some though on this, I came up with a simple idea, the result of which is one of the most linear and enjoyable (if enjoy a good brake in life) brakes on a bike I've ever experienced!

By making the brake lever push the throttle in this arrangement, I was able to activate proportional regen braking like my normal rear brake. — The Throttle/Ebrake Combo

Because the regular disc brake was set up to grab only at the end of the lever's travel, the only spring — Adding More Feel

So on top of saving on brake pads and having some really powerful stopping power (I've seen up to over 1kW), I have on hilly rides recovered up to a third of my assist power back, which is incredible! — Getting More Back!