It's officially underway... 1986 Mazda RX7 EV project!

[BigMouse]

As of today, my EV project is officially underway. I purchased a 1986 Mazda RX7 with a bad motor in it. More details and pictures to come. I'm hoping to turn this thread into the next Forkenswift style documentary of the process.

For those thirsty for pictures, here are some before and after pictures of my motor after a rebuild:
Before:

After:

[omgwtfbyobbq]

Is it just me, or is that one big motor?

[BigMouse]

Originally Posted by omgwtfbyobbq

Is it just me, or is that one big motor?

12" dia by 13" long. Dual output shafts. It's a Baker forklift drive motor. Brushes have been advanced 10 degrees. According to my dial indicating torque wrench, it produces 25 ft lbs of torque at 12v, 0rpm. Don't have an ammeter (yet) to measure current though. Either way, it should be MORE than capable of propelling my RX7 with 120-140v worth of NiCad cells behind it. I hope having a bigger motor doesn't effect economy the same way having a bigger gas engine does.

Quick reference:
Goals for my EV:
30+ Mile range minimum (70 or more hopefully)
65+MPH continuous speed
On-board 110v charger.
Minimum cost.

[omgwtfbyobbq]

It may, but it won't have the same magnitude. There may be a ~10-20% difference between efficiency, motor size, and average power needed, but it's not like gasoline engines where efficiency can drop by a factor of 2-6 depending on gearing and displacement. I'm curious, if you're trying to minimize costs, why did you go with NiCad batteries?

[Bill in Houston]

Ya, that's a biggie... Super cool! I hope it all goes great for you!

[SVOboy]

Sweet project! I hope you keep us updated step by step!

[BigMouse]

Originally Posted by omgwtfbyobbq

I'm curious, if you're trying to minimize costs, why did you go with NiCad batteries?

I'm getting the NiCad cells for free from the airline I work at. They are "unservicable" cells, which means that they're no longer fit for use on aircraft, but so far all (11) of them seem to be just fine for my purposes.



Each cell is 1.4v and 40AH. It will take me quite a while, but I'm planning on collecting about 100 of them. Of course, I don't plan on stopping when I get to 100. Gotta have spares and room for upgrades of course ;-)

Also, a picture of the car, just to keep things moving:

[SVOboy]

Free batteries, nice! What's the cd on that car?

[bbgobie]

Holy! 1.4V each! That's a lot of wiring batman!!

[TomO]

Pretty cool project there! With my new business of working on golf carts this summer, I think I might have to score a motor and controller and related parts for a future EV project of my own.

[MetroMPG]

Neat-o. Was the motor free too? Where'd you get it? Who did the rebuild & what was done?

Looking forward to watching the progress.

[BigMouse]

Originally Posted by SVOboy

Free batteries, nice! What's the cd on that car?

No idea on the Cd of this car. It's pretty sleek though ;-)

[BigMouse]

Originally Posted by MetroMPG

Neat-o. Was the motor free too? Where'd you get it? Who did the rebuild & what was done?

Looking forward to watching the progress.

Nope, got the motor for $200 (I'll post a table with my costs so far and a running total as I spend more on it). Got it from a forklift wrecker. I rebuilt it myself with new bearings and a 10 degree brush advancement. The comm and brushes are still fine, so I didn't touch those. Media blasted and repainted the case with polyurethane enamel (light gray).

[MnFocus]

Sweet deal all around! Always loved that body style of the RX7,EV power makes it better still. Definitely keep updates coming .

[omgwtfbyobbq]

Originally Posted by BigMouse

I'm getting the NiCad cells for free from the airline I work at. They are "unservicable" cells, which means that they're no longer fit for use on aircraft, but so far all (11) of them seem to be just fine for my purposes.

You scored free SAFT NiCDs?
I H8 you so much right now....

[skewbe]

FYI, cartest lists the CD as .31 for a 1986 rx7, it didn't have a frontal area figure.

[BigMouse]

Originally Posted by skewbe

FYI, cartest lists the CD as .31 for a 1986 rx7, it didn't have a frontal area figure.

Is that good? What is cartest? Any use for an EV?

[omgwtfbyobbq]

Mayfield has the same .31 figure w/ a reference area of 1.784 square meters.

[MetroMPG]

Very resourceful.

Our forklift guy said: "$500 for the motor (if we remove it for you) or $500 for the whole forklift, your choice."

I'm glad we took the whole thing, seeing as the traction motor ended up being too fat (girth wise) to use with our transaxle. You won't have that issue with RWD though.

[MetroMPG]

Do you have the bumper for the car?

[MetroMPG]

Say... what do the specs say on your motor tag?

At first glance, it appears to be very similar to the torque monster we have. (Had - it's sold, but the guy hasn't come to get it yet.)



The main difference appears to be the big internal fan on our drive end, so it's a bit longer overall @ 15.5 inches (not counting shaft). You might have to set up forced air cooling (depending on what kind of range/amps you're going to be dealing with.

Did you get a coupler with it? Are you going to mod something to work with the square shaft, or get a round shaft pressed in?

Sorry for all the questions.

[BigMouse]

Originally Posted by MetroMPG

Say... what do the specs say on your motor tag?

Did you get a coupler with it? Are you going to mod something to work with the square shaft, or get a round shaft pressed in?

Sorry for all the questions.

No, no bumper for the car yet.

I've got the couplers (both sides) for the motor, but I'll likely end up machining the motor side one down to mount my flywheel to it.

The motor dataplate lists it as an A-9044-Y4, no specs on it though.

[jwxr7]

Nice score on those batteries . I had an 87' rx-7, it handled nice, I've always liked that body style. Good luck

[MetroMPG]

Originally Posted by BigMouse

to mount my flywheel to it.

I'm still on the fence about whether or not I'd retain the flywheel if I had to do this over again. I'm getting used to driving the car clutchless (including downshifting, which was a bit of a problem before I figured out the right technique).

The motor dataplate lists it as an A-9044-Y4, no specs on it though.

I take it you saw the info I posted from EVDL motor guru Jim Husted, on forkenswift.com:

I've never seen that motor [... edit - the forkenswift motor...] but know it's cousin the Baker 9044-Y4. From what I can see the only diference is the Y4 had 3 wires per slot and had more comm bars than your armature, which makes your rated for a higher voltage being the Y4 was rated at just 36 volts OEM. The Y4's were a good harty motor and that might make a really great medium voltage race motor if you EVer decide to make your mark on NEDRA 8^)

http://forkenswift.com/baker-12-in-motor.html

[BigMouse]

Originally Posted by MetroMPG

I take it you saw the info I posted from EVDL motor guru Jim Husted, on forkenswift.com

Yup. I actually met Jim last weekend. Talked with him quite a bit about my motor and EV motors in general. Very helpful guy indeed.

[MetroMPG]

Was that at the NEDRA event? Did you buy a raffle ticket?

[BigMouse]

Originally Posted by MetroMPG

Was that at the NEDRA event? Did you buy a raffle ticket?

No, it was at the Saturday morning car show thing the morning after the first night's races. I didn't actually make it to any of the races :-(

[MetroMPG]

FYI...

Originally Posted by BigMouse

Nope, wasn't me. I haven't joined that list yet. I can't stand the old style mailing lists where everything gets forwarded to everybody. An online forum like this one is much preferred for me.

The admin of the listserv is trying out a web forum style "archive": http://www.evdl.org/archive/

You can reply to posts using your browser, but you have to be registered on the old-fashioned mailing list for them to go through. (You can then set your listserv prefs to "suspend" so you don't actually get all the email.)

Details: http://www.nabble.com/New-EVDL-Archi...html#a12099227

[BigMouse]

Got the gas engine out of the RX7 yesterday. Currently trying to figure out how to mate the pressure plate to the output shaft of my motor. I'm planning on using the coupler that came with it (square drive lovejoy coupler). The stock RX7 pressure plate doesn't have a flat mating face, it has a bore. Not to mention a massive integral counterweight. I figure my options are to either take the stock pressure plate to a machine shop and have them cut the hell out of it to make it flat on the back side, remove the counterweight, take some un-needed material off of it, and balance it to neutral. That sounds expensive.

I'm also playing with the idea of making my own pressure plate from a flat 3/8" piece of steel. Would already be flat on both sides, would be much lighter (even with some stiffeners welded onto the backside), and I could have that balanced when I'm done. Just curious if the kind of steel I'd get from a steel yard would hold up to the wear ant tear of being used as a friction surface for a clutch.

Oh well. I'll be removing (or attempting to remove) the stock pressure plate tonight and I'll see what my options are with a little more clarity.

On another note, work on my homebrew controller is coming along nicely. Waiting for some P-channel MOSFETs to arrive so that I can couple one with my existing N-channel MOSFET to build a push-pull amplifier for output to the IGBTs. It seems that the IGBT's 'latch' in either the on or off state. This means that the gate requires V+ to turn the C-E on, and a V-(but GND works) to turn it off. Luckily, the PWM output of the chip alternates between +5v and GND for it's cycle, so this should work well to drive the MOSFETs, which then drive the IGBTs. More experimentation to be done, but experiments with a small magnetic radioshack motor show promising results. Since the IGBT's high current/voltage portion is insulated from the gate, It shouldn't matter whether I'm running a CPU fan or my monster 12" motor to the PWM controller. If all goes well, I'll be into the controller for less than $75 in parts.

My total investment is quicky approaching $700 though, and I've still got a fair amount of additional spending to do (welding cable, copper bus-bar for batteries, 1000a shunt, misc parts for the RX7 to make it road-worthy), so I doubt I'll hit my sub $1000 goal. We'll see though.

[BigMouse]

Here's my PWM motor control as it looked on the breadboard:


I've tested it on my 12" motor and it works, but unfortunately I burned out a couple of my IGBT's by using them without a snubber capacitor. It works fine with the little motor though. I've got some capacitors and a heatsink on the way, so another high-current test will take place at that point.