Insanity? -- 3 phase battery powered MOTORCYCLE!

Maybe he enjoys doing things in an unusual way. It's not a project I would want to help him with, though. Induction motors are not well-suited for propulsion because of the rather narrow speed range in which they develop much torque. DC motors or switched-reluctance motors are much better suited for variable-speed, have much better low-end torque , and they tend to be lighter weight for given HP.

Brushless DC motors are really polyphase machines, but they are not induction motors; they have either a permanent magnet field or a driven wound field. SR motors are also polyphase machines with *no* field. They pack a lot of power in a small, lightweight motor -- but torque ripple can be a problem. A guy I know developed SR motors and controls for a bus running in (I think) Taiwan. The Maytag Neptune washing machine originally used an SR motor, maybe it still does. Got rid of the transmission.

For the curious:

Batteries: a 105 amp-hour 12-volt deep cycle battery weighs about 50 lb, contains about 101 hp-minutes. At 7.5 HP this would be about

13 minutes of operation -- at 100% efficiency. Having all those conversion will reduce efficiency quite a lot. More importantly a 105 AH battery will NOT supply 466 amps, which is 7.5 HP at 12 volts. They're better suited to loads of up to 50 amps. He'd need 8 batteries (400 to 500 lb worth). Maybe a forklift battery..... hey, Ig, do you see any submarines in your surplus shopping adventures?

It's very simple: idea is to not use "half the batteries" at half power but to use all the batteries.

Traction motors had several windings which could be connected in series (for low speeds) or in parallel (for high speeds) depending on the application.

In a battery application with one winding you'd bank the batteries to be in series or parallel based upon need.

But that's mostly historical... all DC traction power applications now use "smart" electronics to drive AC motors (often 3 phase... sometimes more!).

Tim.

Iggy sez: "Maybe he BSed me and had other purposes in mind. Which is fine with me"

What is really scary is if he wasn't BS'ing you!

Bob (Hey! it didn't kill Ben Franklin) Swinney

Induction motors are bigger and heavier than the equivalent brushless motor with permanent magnets, and an inverter is much less efficient than rewinding the motor to whatever the battery voltage is.

Other than that...

My guess is that he may use the free motor for some bench testing, and then figure that it is not the motor to use. But what the hey, it was free and within driving range to pickup. I am sure he will learn something from this.

Dan

States the motors are brushless servo technology. Sounds like a brushless DC motor. Bottom line; the motor is running on DC, not AC.

They also appear to be use high tech magnets etc to pack 2.5HP into a small package.

A far cry from using an old Heavy industrial 7.5HP AC motor that will have a very limited speed range too.

I think anyone attempting to build an electric motorcycle by scrounging up parts won't get very far.

I own 4 electric scooters. The better ones use three 12volt batterys feeding a 36V DC motor. Surprisingly quick for a 350watt motor. The whole scooter weighs 65 lbs and will carry an adult very well. Very simple and works.

That's a PERFECT idea for those "lawn" thingies. I hate mowing and wear a mask nowadays.

And the answer to your question is an unqualified "YES!" That 7.5hp motor is what, 150# by itself? Let's see, if he pulls the 20kW generator trailer behind him...

One thing I'd like to ask you to do, though, is to videotape the reaction this guy has when he comes to pick up that monster. That oughta be PRICELESS!

Well put. :)

That's my thinking also.

A bicycle does not need 7.5 HP to e propelled on flat surface. A bicyclist develops perhaps 100 watts (on a lightweight bike, not a battery loaded monstter).

I have a few navigation pieces from Ohio class nuclear ballistic missile submarines, sitting in the shed next to my 6 chickens. No batteries though. :)

i

Like I said, he was a very pleasant guy. I wish him best.

i

I got it, thanks.

What I was thinking about, idly, was to make a 3 phase inverter. Can't see why it would be impossible.

i

I hate mowing too. I like tall grass, waist tall. It is beautiful and fun to play with and is a habitat for all kinds of cool animals.

ROTFLMAO

Um, maybe I misunderstand you, but he already picked up his motor.

I told him about my doubts, etc.

i

I am not so sure.

I bought two DC motors for next to nothing: a 90V 1 HP Leeson ($5), and a 180V 1.5 HP Dayton with controller ($20).

Add to it a few electronic relays, this and that, and I could quickly have a power unit built on a cart.

I am lousy at power transmission and building motorcycles, though.

Yes, that's what I would do as well.

i

"Our engineers were so obsessed with the details on the Segway HT that they designed the meshes in the gearbox to produce sound exactly two musical octaves apart--when the Segway HT moves, it makes music, not noise"

Uhh... this gear box makes too much noise. How can we make this sound like a benefit?

Mark

Mark

I submit that the engineer's design of the gearbox provided the sound that the salesman made into Music.

Jerry

Getting 90V DC would require some fairly expensive and heavy batteries.

180VDc would probably be insane. You will spend way more money on batteries than you saved on the motor. All the components have to work together and thats pretty tough to do with scrounged parts. You will spend so much time trying to make it work and still have a compromised product.

I have degrees in electrical engineering. I use to think I could design and build things cheaper than I could buy them. In college we would build our own audio amps, digital clocks etc. It was fun and educational, but not really cheap when you take into account the burned out parts that are part of the learning curve.

I use the same concepts for metalworking. I repair things and build what I cannot buy. I cannot build things for the same price they are available commercially.

My point here is simplicity. An electric motor with a chain drive to the rear wheel. An electric speed controller and some batteries. Very basic; leave the fancy electric vehicles to the pros with big bucks.

I'd be way more impressed if the two "notes" were a 5th apart.

But when you get to be a productive engineer, you can usually get free samples to burn out.

It will work just fine, as soon as he gets his Shipstone Batteries. Or the Mr. Fusion in the proper place on the bike.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Actually, you need to supply a 240 V VFD with about 340 - 360 V DC, which is the peak voltage of a 240 V line. You probably want to use a 240 V battery stack or a bidirectional voltage converter, as the VFD will pull energy back from the motor on deceleration. How the HELL you will pack all of that PLUS the 7.5 Hp motor into even a large motorcycle frame is beyond me. I've seen it done to a Ford Taurus station wagon, and there WAS enough room there. But a motorcycle? Better be miniaturized electronics and batteries!

Finally, is 7.5 Hp enough? I have my doubts.

Jon