Ben Nelson's Electro-Metro Build thread

[MetroMPG]

Fifty bucks! I heartily approve.

[frodus]

Originally Posted by bennelson

I spent $50 on it.

It is about as big a motor as would fit in a Metro. It does turn freely. I put a 12 volt emergency jump starter pack on it with a little spare battery cable from the motorcycle connecting two of the four power connectors on the motor. It made the motor spin.

I like the idea of some sort of regenerative braking. I will have to contact some other EVers and see what would be needed to make that work. It's a really interesting idea.

I have not had this motor open yet. I will need to de-grease it and pull the end off to take a look at the brushes and everything.

I know a lot of these old forklifts were highly abused, but were very well built.

The main problem is that I can't even lift this thing. It must be 150 lbs easy.
I should be able to roll it around my garage and take some bolts out of it.

I am really busy this next week, I may not get to work on this motor for a while - too many other projects going on right now!

well, it looks like a series motor, and you can't get regen out of it with the controllers out there. The issue is, you have to reverse the field current... you can do it with sepex motors because they have field terminals on the controller that handle the reversing. You can't do that on a series motor. Maybe look around to see if people have worked on getting regen out of a series motor... but I haven't found anything yet.

[WaxyChicken]

DO IT DO IT DO IT!!!

That one looks comparable in size to the one I've gotten.
(compare here:http://ecomodder.com/forum/showpost....1&postcount=23)

It's big, bidirectional, and it runs. Can you find a tag on it for KW or Volts?

is there a brand on it? I found out from the salvage yard that most people are looking for the CROWN brand motors because they seem to be more durable than any other brand.
(i had a crown an didn't know it because the word was written funny and one letter was rubbed off. look for it with this logo font.

Also - they'll give you a free exploded parts manual via e-mail)
By the way - when you try and weigh it - don't be surprised if it's over 240lbs and warps your bathroom scale.

[MetroMPG]

Originally Posted by frodus

well, it looks like a series motor, and you can't get regen out of it with the controllers out there.

Apparently there are controllers that do series regen, eg. see the Zapi referred to on this page:

http://www.evconvert.com/eve/ev-schematic

But I was suggesting Ben could use the tailshaft and a modified alternator to do rudimentary regen rather than the motor controller. That idea comes up once in a while on the EVDL.

[bennelson]

I have already weighed some strange items with the bathroom scale.

I decided against it with this motor.

Last time I was weighing motors with the bathroom scale, I got an e-mail from my wife asking if I had seen the scale lately.

It was eerie that she seemed to know that I was up to no good with it.

[bennelson]

Hey Metro,

A while back, you mentioned the idea of using a 36/72V parallel/series setup in my Metro.

If I understand correctly, a Citicar uses several contactors to connect and disconnect the various batteries so that all are used at the same time, but sends differing amounts of voltage (12/24/48) to the motor, thus different speeds.

What if I used a 36 volt pwm controller (Cheap! as there are a zillion of them for golf carts) and then had a contactor set to disconnect the controller and instead connect all the batteries in series. A reversing contactor might be able to do both at the same time, right? A reversing contactor disconnects one set of power, then connects a different set of power cables (break before make) Do I have that right?

The controller would be used for smooth and easy speed control and accelleration. Then for top speed (72V) the contactor would flip. There would no longer be any speed control, but this would be used for cruising only. That contactor could be set with a momentary-on switch so that as soon as you want to stop "cruise mode" you just release it. It could be some sort of hand switch or lever, or a button under the gas pedal that is only closed when you have the "pedal to the metal". I guess it might be best to have a manual control, so that power could be let off thru the controller before kicking over to 72V. Having full voltage running through the controller, then doing a hard disconnect from it, doesn't sound healthy for the controller.

Does this seem like a reasonable idea for a cheap experimenters way of not having to buy a 72 Volt or more controller? It would also allow max amps at 72 volts, would that help with hill climbing?

This setup would also mean my battery pack could be charged by a 36V charger (which I already have). One monsterous forklift charger (which I would have to see about lowering the output on!) and one little tiny 36V smart charger. I could always get a nicer 36V charger later, and it would still be fairly inexpensive.

Would I be getting into arcing issues with the contactor? Is there some other way anyone can think of to help keep my budget down / have fun / DIYerself mentality while still making this a very safe and drivable car?

[MetroMPG]

Originally Posted by bennelson

If I understand correctly, a Citicar uses several contactors to connect and disconnect the various batteries so that all are used at the same time, but sends differing amounts of voltage (12/24/48) to the motor, thus different speeds.

You are almost correct, sir. The first step is 24v through a fat resistor, then straight 24v, then 48.

What if I used a 36 volt pwm controller (Cheap! as there are a zillion of them for golf carts) and then had a contactor set to disconnect the controller and instead connect all the batteries in series. A reversing contactor might be able to do both at the same time, right?

What would happen, is you would be vaulted to revered status among all the cheap.. I mean budget.. EV builders out there.

It's slightly more complex than that however. My limited understanding of the issue is that when you switch BACK from 72v to 36v, there needs to be something to:

1) prevent the contactor from arcing if you're under load when you open it (I think this is done with a big resistor in parallel with the contactor); and,

2) prevent "back EMF" (high voltage in the motor that exists briefly upon disconnecting the power) from flowing backward and hitting the controller, thus frying it.

Having full voltage running through the controller, then doing a hard disconnect from it, doesn't sound healthy for the controller.

I'm not certain about this part, but it seems to make sense.

Does this seem like a reasonable idea for a cheap experimenters way of not having to buy a 72 Volt or more controller?

Definitely. THE Yoda of the EVDL has recommended this approach, but nobody has done it yet, as far as I know.

It would also allow max amps at 72 volts, would that help with hill climbing?

Absolutely, compared to 36v.

Do eeeet!

[MetroMPG]

PS - the answers to the technical questions about doing a PWM 36/72v setup will be found on the EVDL. Or perhaps at DIYelectriccar.com - not sure it has the same level of Yoda-ness yet.

[bennelson]

I got the drum brake end off the big forklift motor.

After removing the brake, I could see that the shaft going through the brake drum is threaded on the end with a castellated nut, and after that it IS SPLINED!

The splines are the same as on the main drive shaft end.
That means that perhaps I can use the brake drum cover part with the splined hole on the main end of the motor and use it as a base for a coupler.

It may even be possible to use it as a base to attach the flywheel and then keep the clutch in the system.

The downside is the brushes are terribly worn, and the commutator doesn't look great.

Once I get the motor further apart, I can get a better look at it, clean it up some more, and make sure it's the way I want to go.

I hooked up my 12V jump starter and made it spin, but I could see a little bit of arcing at one of the brushes.

One thing about the hydraulic pump motor is that it is in new condition (totally rebuilt) and has awesome brushes!!! Too bad it has such a lame connection.

[MetroMPG]

Don't forget if you bolt the flywheel on, you'll be adding a thrust load to the motor shaft with the clutch engaged. It may not be designed for that (you might have to design in some bearings to deal with it).

You could also probably pretty easily machine the splines off and then use a regular taperlock style hub/coupler.

And you know... if you could engineer some way to use that lame "slot" style pump shaft (some kind of stub shaft held in place with a support bearing?), you'd be even more famouser than you are now. Everybody else doing a budget conversion who ends up with one of those motors would be in your debt.

Have you asked Guru Husted for his advice yet? I haven't checked DIYelectriccar.com for a while.