How do I make a trike electric?

[zjrog]

Just a thought, even though my wife is doing well on her trike, we were dealt another health issue for her.



She has had issues with her right hip for years, but it has been getting a lot worse lately. Doctors aren't sure if she has a fracture in the socket, or a tumor. So she is on crutches for 4 weeks and will have new xrays and a MRI to see... Fun huh? So went digging in the medical supply store (my basement) for crutches.

So, how hard would an electric setup be to add to a trike? What do I need, what can I fab? I would like to see if I can setup something with a chain and sprocket to drive the axle, but not be a hindrance when pedaling. When we got the trike and I put it together, we added the optional 3 speed hub and coaster brake. I can get another adapter to use a single speed freewheel on the shaft (since I didn't use the included freewheel), so that leaves mating a motor and power controller. Ideas, thoughts, opinions?

(Yes, we ride with helmets, I had her turn around and come back to the truck for the pics...)

I will add, that until her strength and endurance get better, we ride on a flat stretch of road where lots of cyclists go and very limited vehicular traffic. She has done well (since she almost died of double pneumonia in April), keeps a good pace and speed, and has added distance weekly... We have been pleasantly surprised by the encouragement of most riders with very very few snobs (roadies, you know who you are!).

[Ryland]

what is your budget? what kind of speed?

[Christ]

Front hub motor FTW. If that's not cost effective (~$300 for a kit on eBay), then a freewheeling motor in line w/ the axle chain and a couple batteries in the basket on the back. Don't forget you need at least 45* tooth engagement for a good bite on the chain.

[NiHaoMike]

500w or so DC motor attached to rear axle with a simple PWM controller using a relay to switch to regen mode. Normally, the positive side of the motor would connect to the positive supply and the negative side to the PWM, but engage regen and the positive side reconnects to the PWM and the negative side to ground. http://techno-fandom.org/~hobbit/cars/boost-hack/

A high side MOSFET can provide for synchronous rectification and regen without a relay, but there isn't much to gain from synchronous rectification and a regen relay would likely be simpler and cheaper.

[zjrog]

I'm thinking I can add a second sprocket to the rear axle, which would be a freewheel. So I don't think there would be much regenerative charging.

Budget, less than $100. Batteries aren't a real issue, I might be able to get some freebie recycle turn-ins.

Speed, 10 MPH or less. Would like a range of 15 miles, but less isn't bad. I just want the thing to get up hills around town here, and with it freewheeling when pedaling, be almost transparent (minus the battery weight...).

I'll get and post a pic or two of the rear axle and drive stuff later.

[Bicycle Bob]

[QUOTE=Christ;127324]Front hub motor

I second that suggestion.

[NiHaoMike]

Originally Posted by zjrog

I'm thinking I can add a second sprocket to the rear axle, which would be a freewheel. So I don't think there would be much regenerative charging.

Budget, less than $100. Batteries aren't a real issue, I might be able to get some freebie recycle turn-ins.

Speed, 10 MPH or less. Would like a range of 15 miles, but less isn't bad. I just want the thing to get up hills around town here, and with it freewheeling when pedaling, be almost transparent (minus the battery weight...).

I'll get and post a pic or two of the rear axle and drive stuff later.

Use a 500w or so motor geared for high torque, so it tops out at 15MPH or so. You'll get plenty of regen going down the hills, especially with the motor geared for torque. Like you said, it should neither accelerate nor regen by default, but just freewheel. That's easy since all it needs to do is leave the PWM off. You'll have a potentiometer to adjust PWM power (amount of acceleration or regen) and a switch to select between acceleration and regen. (As unusual as that sounds, someone on a hybrid bike site actually uses that "sign magnitude" setup daily. A more usual center position for freewheel is actually more complex to design for a brush type motor, but merely a software setting for brushless DC.)

[Christopher Jordan]

Originally Posted by zjrog

Speed, 10 MPH or less. Would like a range of 15 miles, but less isn't bad.

Just my opinion- those old design diamond frame trikes are unsafe disasters at all speeds. I had an old Huffy in the mid 1970s and at 2 mph it threw me off hitting a driveway and I fell a long way then rolled into a busy street.

Undaunted; the next day it wouldn't stay on the ground around a corner- tipped, went over- bloodied up badly. That was at 5 mph. Granted- about 10 to 20 pounds of battery would have helped, it would not help my grip or balance problem. Bye bye diamond frame trike.

My solution was to be low, but that is not for everybody. I have a hub motorised trike and an EV microcar 3-wheeler- both are a little bit faster than 10 mph (legally in CA.: 20/50 mph) I would never EVER try that on a diamond frame trike!

[NiHaoMike]

Converting it to a recumbent should greatly improve stability.

[MadisonMPG]

In all honesty, should she be riding a bicycle? With that health rep sheet I would be afraid to get out of the house.