Human Electric Trike Thesis

Design of an electrically assisted human powered trike

Visited Runabout Cycles

Posted by Bob Dold on Monday, June 19, 2006 8:19 PM

Today I made a visit to Runabout Cycles in Florence MA (Northampton) and spoke with Josh Kerson , the founder of the electric trike company. Josh mentioned he has been working on the human electric hybrid idea for about 5 years, has made several prototypes, and is currently in limited production of their  electrically assisted trike.

Production Runabout cycle:

Josh had two assembled trikes on hand, the prototype fully suspended unit that weighed in around 250#, and the new production model that weighed about half of the prototype. The production unit did away with the rear suspension to save weight and used  a 7 pound PMG 080 motor instead of the 25 pound eTek motor on the prototype. The production unit also looked to have smaller tubing that the ultra beefy prototype unit. I took a quick ride in the orange production unit in the parking lot and was very impressed with the smooth steering and quiet electric drive system. The unit I rode had a 19:1 gear reduction through a 2 stage chain reduction drive system with a freewheel to allow coasting and pedaling when the electric power is not used. Josh mentioned the gear reduction was necessary to get the high efficiency out of the PMG 080 motor, the prototype unit used a single stage gear reduction with the slower, more powerful, eTek motor.

Prototype Runabout cycle:

Josh indicated he designed the steering linkage to allow more precise control at higher speeds by increasing the steering handle throw in relation to the wheel movement. Compared to my Sun EZ-TAD’s rather twitchy steering, the Runabout cycle’s design was much easier to control at speed. The stock production unit is designed to top out at 20 MPH to comply with federal law for assisted bikes, although Josh mentioned the motor is capable of more. The design goal was to have enough power to cruise up hills at 20 MPH, something that can bring a lot of electric bikes to a halt. The prototype unit Josh was riding had been ridden all the way to the top of Mt. Washington, demonstrating the hill climbing capabilities of the trike.

Josh was very helpful in explaining the current market for human electric hybrids – because of their electric motors they are a little too complicated for a bike dealer to sell and service, eliminating a possible retail outlet for the bikes. Because of the pedals and electric drive they are not a natural sell for a motorcycle or automotive dealer. The best outlet for the trikes appear to be a network of electric bike dealers that currently stand at about 50 strong nationwide.  Josh mentioned he was hoping to market the Runabout cycle with a few of these retailers who will already have some experience dealing with the electric drive train. He mentioned that most commercial eBikes and conversion kits were designed for light flatland use – top speeds of about 15 MPH and max motor power of about 750 watts.

The standard runabout cycle comes with two 30 amp-hour 12V  lead acid batteries, which are good for about  40 miles range and 500 discharge cycles. The cycle comes with a "Drain Brain" which tracks the electrical usage, speed, miles traveled, and acts as sort of a ‘gas’ gauge for the batteries. Runabout is also a distributor for lithium -ion batteries which give the same capacity at half the weight and are good for 1700 cycles. Lithium-ion batteries give a relatively constant output until they are drained – unlike lead acid which slowly reduce output as they discharge. The cycle can be upgraded to lithium-ion for about $1000 more than the base cycle’s $4700 price. In addition to the trikes, Runabout also does custom electric conversions for bikes, Josh showed a couple of conversions using powered cranks with e PMG motor and lithium-ion batteries.

Recumbent conversion:

Josh spent about an hour discussing the trike and his company and was very helpful in answering questions and providing lots of detail on his trikes and the thought that went into them. He offered to answer any questions I might have in the future and even offered to have me take a longer test ride when I get a chance.

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