I call this a HEAT/SCH
ssist bike T
His 'full' name is Woodrow Prime. He goes by 'Woody'.
Here he is in shopping cart mode.
Power is from a 450 watt Currie geared motor controlled by an I-zip I500 scooter controller overvolted from 24v to 36v.
The power transmission is through a typical 5 speed gear cluster from an old 10 speed bike which is shifted with an old drill off of it's own NiCd power pack. Limit switches and diodes were added to the drill to make a home brew linear actuator.
It's controlled with a rocker switch under the left brake lever.
At the top of this photo is the hitch safety strap and wiring harness made from and old mother board power connector.
The long gray plastic box is the main battery, a 36v 10ah(?) lithium(unknown exact chemistry) borrowed from a Tres Terra Europa.
The trailer is a modified Burley and total weight is around 46lbs. I added a telescoping caster to the front for shopping cart mode.
Set up as it is, it's not technically a 5 speed. Spacers I had to add for the derailleur were not long enough and now it's just about impossible to get into 1st gear... although it really isn't needed. I shortened the trailer as much as I dared and now the 'chain path' suffers badly from cross chaining in 2nd gear. This could be eliminated with a geared hub or by moving the motor in and out as the shifting occurs. I might try the later if I can figure out some kind of dovetail mount for the motor.
I tried to keep the cost down for this build so I tried to use junk I already had lying around.
The motor was $45 plus shipping (along with other items) from http://www.allelectronics.com
The motor is now sold out.
The trailer was $40
The scooter was $30
Other misc. items brought the total cost, as best as I recall, to somewhere around $210 excluding the Europa's battery.Specifications
I don't have too many miles on it so specs are limited.
'Wheel off the ground' WOT showed 30.9 mph in 5th gear.
I've got about 20 miles on the trailer so far and the fastest speed I've seen with it pushing me and no pedaling was 26 mph on a slight downhill.
Woody held up fairly well in those 20 miles. A solder joint on one of the linear actuator's diodes came lose on one trip but you can still open the trailer up and turn the 'screw' by hand to get it into a different gear if need be.
One trip hauled around 35lbs. of groceries. The trip to the store is uphill and the loaded portion is all downhill. I've seen 35 mph downhill and the trailer trailed just fine.
I'm a fair weather rider and I doubt Woody will see much use till the Spring thaw arrives.Changes/improvements
I'd like to shorten the trailer's width and length but it does work as is and will clear a 2' 8" door.
As mentioned earlier, a geared hub or enabling the motor to move as it's shifted.
The Currie geared motor does make it whine but it's not horrible. I've read many of the Currie posts about grease and oil... I'm thinking of trying a belt drive modification.
This longer version of this story was originally published on fieldlines.com (http://www.fieldlines.com/story/2009/11/10/16828/297
) and linked to ES by spinningmagnets under the post "Revisiting a Push Trailer"... thanks again spin, your linking the story made me decide to join ES and post the story here.
Comments and/or questions welcome,