Project Slow-Moving Metro

[MetroMPG]

Originally Posted by JQmile

Ok first question...given a weight of say, 1800 pounds, a frontal area of 20 sq ft, and a drag coefficient of .50, how much hp will it take to go down the road at say, 50mph? I used RBR Racing's aero calculator and came up with 12.6hp, but not sure how accurate it is.

https://www.rbracing-rsr.com/aerohpcalc.html

See also:

• Aerodynamic & rolling resistance, power & fuel consumption calculator

[redneck]

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Cool project...

There's plenty of room in that engine bay for a small 4cyl Kubota diesel.
Then lower it a little and you'll have a super cool fuel sipper that looks like this.







>

[JQmile]

Originally Posted by elhigh

I subbed this so hard. The old Nash Metro is one of my all time favorite cars, and one of the original economy cars. It is a thing of old school beauty.

Being so old school, there are lots of little aero mods to be made that will pull your power requirements down. Maybe not into the range of a single Etek (nice score finding an original B&S one, BTW), but any improvement is an improvement. I chance to know that the underside is about as smooth as the craters of the moon, for instance.

It's also nice that you have such an obviously old tiny car. Nobody will expect it to be fast. It is its own apologist.

You hit basically all the reasons for the build right there. The Metro is waaay different already, so might as well make it even more so. I'm thinking about getting a second Etek if I can find one as a spare or additional motor.

Originally Posted by MetroMPG

See also:

• Aerodynamic & rolling resistance, power & fuel consumption calculator

That's a cool one. It's crazy how much HP starts going up once you're past about 40-50mph.

I'm really liking the idea of trying two Etek's with a diesel generator now. Drive one day on electric, next day with the generator on to recharge the batteries when traffic isn't moving. Had that idea after commuting 40 miles in Los Angeles for about 2 years. Average drive was 1-2hrs one way depending on traffic. A lot of sitting.

What's the most I could put to the batteries to charge them amp-wise without them overheating? I know they have 48 volt alternators for power generating windmills and such that can put out up to 190 amps! Seems like a lot, with no electricity going out.

[JQmile]

Ok, the plan is getting a little more solid. I'm grabbing a second Etek and going to use two for the project. That means 12hp continuous, and 40hp peak at 48 volts. Going to mount the motors right to the rearend with a gear reduction, and then create a whole "regeneration rig" with a small 15-20hp engine and 48V alternator designed for windmills. Seems a lot more complex than just doing a small 20hp engine alone, but I think this setup will give a lot better city mileage, and better overall power than just a small gas or diesel engine alone. I'm also looking at having the motors be mounted on the ends of plates that look like traction bars, so the whole setup can be transferred from vehicle to vehicle with ease. Here's a few pics of the Etek, for those who've never seen one. They're incredibly powerful for how small they are. Only about 20lb.

[MetroMPG]

I'm somewhat familiar with DIY, lightweight, 48 volt electric cars.

Done the math to figure out what amperage you're talking to get 40 peak hp? It's way more than my controller could do.

[JQmile]

I have an Alltrax 400amp controller, but the Etek's only rated to 330amps, so I used that number. I've heard of people running them up to 480 amps and 96 volts (which would be about 63hp x 2 = 126hp) but I'd only expect them to last a few quarter mile passes at that load and speed. If you want to do the math, they make about 1.2 inch-pounds per amp (some list it as 1.14).

That Swift is cool.

[elhigh]

JQMile, I can't tell you just how enthused my wife is over your project. I'm completely serious, she saw your Metro and squee'd, then saw the motor and squee'd again.

I don't know how your project is playing at your house, but it's a winner in mine.

[JQmile]

Originally Posted by elhigh

JQMile, I can't tell you just how enthused my wife is over your project. I'm completely serious, she saw your Metro and squee'd, then saw the motor and squee'd again.

I don't know how your project is playing at your house, but it's a winner in mine.

Ha ha, my cat likes the project just fine, although my buddy still needs to check with the wife....hoping that goes well. If not, he has an old Army Jeep that would be a back up, although since the goal is to leave everything intact on the Metropolitan, I don't think she'll mind. First up will be building a test rig, and getting the driveshaft off of the Metro so I can get a sprocket attached to it. I looked at some pictures online, and I think it has a companion flange on it, so that should make things easier.

[JQmile]

Ok, we went a little past "hey, we should do this," and did some poking around the Metro and a little cleaning. Our first thought on looking at it, was "there's no way this will work, it's too low," but there was a surprising amount of room under there...kind of like the book The House of Leaves, which is about a house that's bigger on the inside than the out.

Anyways, looks like the batteries will fit nicely behind the front seat, the motor (which is still in storage, so I used a Cummins diesel crank pulley for sizing) looks like it will fit right by the rear axle with no clearance issues, and I am pretty sure a small generator will fit in the trunk. So far so good, now it's time to get the electrics up and running on a test stand