Electric car conversion: Project ForkenSwift

[MetroMPG]

Someone asks again when the car will be on the road...

I don't want to predict, because it'll just end up taking longer. (Originally, I said first electric powered drive in September, and we can see how that went.)

The biggest technical hurdle left to solve is fabricating a motor mount. Not a big deal. (I'm hoping to try out stick welding on that task.)

Theoretically, inside 2 or 3 weeks we could have the electric drivetrain in, so we could hook jumper cables between a couple of batteries and the motor, and off we go! Does that count?

As for licenced and being driven legally, 2 or 3 months is more realistic. Just in time for the dead of winter for our heater-less EV!

[MetroMPG]

SW skools me on the basics (I need it)...

Originally Posted by SW

I think that does count. It's the current thing to do.

I don't think jumper cables have enough surface area in contact with the battery cables to handle the current you'd need (even in a test). The clips will probably heat up, and may even burn them at the contact points (you might be shocked to find the battery terminals burned as well), but I may be wrong. Don't let this impede your progress, just keep an eye on it. I read about many EV builders who regularly check and tighten their battery terminal connections because of the effects the high current has on them. One of the advantages of going with higher voltage is lower current:

Volts * Amps = Watts (Watts law)

But you may not be able to change the top voltage your motor/controller can take, so don't get too wired about it.

The other potential problem is the voltage drop across the jumper clips in proportion to the current:

Ohms * Amps = Volts (Ohms law)

So you want to minimize the ohms (unit of resistance) wherever you can: thick cable, heavy duty terminal connections, high surface area connections to your controller, fuse(s), motor, kill switch (eventually), etc. Try to have as little 'etc.' as possible.

[MetroMPG]

As a matter of fact, we already smoked a set of jumper cables. Didn't ruin them, but they sure got warm when we jury-rigged a string of boat batteries to turn the forklift around on the driveway and get it part-way into the garage.

I too have read about the hazards of loose connections. You've no doubt also seen the current "lead" story on evconvert.com

Here's a question: can you go too thick with cabling, etc? Is too much of a good thing a bad thing in that regard?

[MetroMPG]

More good info from SW:

No I hadn't seen the new evconvert article yet (I check it almost daily), thanks for letting me know.

Non-superconducting wires all have some finite amount of resistance and so will cause some amount of voltage drop across them (proportional to current). This loss of wattage amounts to loss as heat. Note that this wattage doesn't need much voltage when the current is high (ex. 1.88V * 400A = 752W or more than 1 hp).

Somewhere there exists well proven recommendations for the guage wire for a given current. As for voltage, thickness of wire is irrelevant, but thickness of insulation is, but you'll not likely exceed the wires' voltage ratings.

There's no electrical reason not to go too thick with your cables, but at some point it adds too much weight and expense (for both cables and connections). Copper is heavy and I don't recommend aluminum wires. Very heavy cables may also be more diffucult to work with.

[MetroMPG]

Back to concerns about the strength/weakness of the custom coupler....

The thinnest diameter shaft in the chain isn't the tranny input shaft, it's the splined shaft welded on the end of the Lovejoy coupler that slots into the motor. Its neck is only about 2/3 the diameter of the input shaft. Compare (click = zoom):





Still, if the transmission shaft is 100% over-engineered, then we should be OK with 66% over-engineering

Actually I'm pretty sure shaft strength isn't linear with diameter, so the over-engineering probably doesn't scale like that.

[MetroMPG]

This evening: Wiring harness disconnected (there's something oddly gruesome looking about it disconnected - brain stem-ish); motor & tranny mount bolts loosened; shifter & rods removed; heater hoses & vacuum tubes cut/removed.

Wheels back on, car lowered. Ready for towing to Ivan's garage for actual ICE-ectomy.

[MetroMPG]

[MetroMPG]

SW liked the technique!

Wow, out through the bottom? I haven't seen that since the old beetles.

I once took an engine out using an old swingset and a come-along, another with a chain over some garage rafters with the come-along, and a couple with a shop crane. The most memorable was the MGB engine I took out with another guy by looping a chain across some head bolts and sticking a long log through the chain. We lifted each end of the log up, and hurled the block up and over the radiator support and down into the dirt (I only wanted the the engine for the crankshaft).

[MetroMPG]

Various people debate the out the top vs. out the bottom technique:

It's how most shops remove engines...for Hondas anyhow.

Most front wheel drives engine/transmisions go out the bottom.

This would fail a police examination immediately in Australia.

Huh. I definiately had to 'lift' the Passat engine to do the waterpump.

All things considered, it probably is as easy to lift a metro off the motor than to remove the hood and lift out the engine.

[MetroMPG]

The Metro drivetrain could have come out the top or the bottom. It only came out the way it did because we had the right tool for the job: Ivan happens to have a manual pallet lift rated for the weight. (If we'd had a swing-set it might have come out the top!)

Next step: re-install the transmission with the trans mounts, axles & shift linkage from the red 4-cyl. car - same transmission casing in both cars, but the 4-cyl mounts offset the transmission about 3 inches more to the left of the engine compartment. That'll leave us more room for the electric motor (which is slightly longer than the 3-cyl engine block, but not quite as long as the 4-cyl block).

Then we need to fabricate an engine mount for the e-motor.