Interest in rear wheel power (electric)

[bwilson4web]

Hi,

I've been following the Plug-In efforts in the Prius groups and had come to the conclusion that retro-fit to an vehicle not designed for it was a dead end. Without going into the details, the problem is the main traction battery won't take a trickle charge from another, plug-in pack. So this leads to a number of kludges that can work but fail under high power situations.

I'm leaning towards a powered, rear axle because it means the plug-in part, more precisely, the auxiliary electric motor and controls are independent of the existing hybrid vehicle. This allows excellent help in all speed ranges and allows a few simple hacks to integrate with the vehicle (KISS.) But first comes the requirement.

To help understand what I'm looking at, the following graph shows what I've found for my NHW11 Prius:


What I'd really like would be a nice 30 hp electric motor to handle sustained speeds up to 55 mph. But the off-the-shelf, 30 hp electric motors are pretty bulky leading to a fit problem. Going down to 20 hp provides a nice city range EV but I already have a Prius with EV mode under 42 (38 mph is more practical.) I've noticed some very nice, brushless RC model motors, Himax, $200/ea., 2200 W. that look promising, They weigh about 24 oz each and handle up to 80A each. This could handle neighborhood speeds but that would be it. Still, keeping the engine in minimum fuel burn mode while I navigate through the neighborhood would help. Any suggestions for small mass, electric motors, preferably brushless?

Gearing and interfacing to rear wheel drive becomes a little tricky but if I get a salvage rear end and some front wheels, it shouldn't be that much of a problem. I would simply 'blue print' the rear and then fit the motor using additional beam strengthening (probably a carbon fiber beam that attaches at the struts) and the problem can be solved. If there is a clearance problem, the spare tire well can be modified.

Sound interesting?

Bob Wilson

[MetroMPG]

Sounds very interesting. I'd love to see someone try it.

I take it you're familiar with Mike D's plug-in electric 5th wheel Honda Insight (first gen). I realize it's not the approach you're after, but the technology may be useful: He's using a compact, permanent magnet (15hp peak, I think) compact Etek motor. You could twin a pair of those.



.
.
.

Somewhat closer to your description is the not yet released Poulsen plug-in hybrid system: Home



That approach uses "pancake" permanent magnet motors attached to each of the rear wheels @ 72v nominal.

.
.
.

Lastly, I don't know if you've seen that Coyote X has just begun a project to convert his Metro convertible into a plug-in hybrid by driving one of the front axles via (again) a permanent magnet motor at 72 volts.

See: http://ecomodder.com/forum/showthrea...brid-5599.html

[MetroMPG]

The closest I've seen to the idea of integrating electric RWD to a FWD vehicle was a Ford Aspire that had one original rear wheel assembly removed, and a front wheel & axle installed in its place. The axle was then chain driven off a series DC motor/controller.

The project was abandoned - chain noise being one issue (he could have used a belt).

As well, he hadn't yet converted the brakes - I think he might have been testing the system with only front brakes working on the vehicle.

[shovel]

As long as we're in the half-bakery here, half-baking silly ideas...


Begin with a 4wd or AWD vehicle, let's say a Forester for purpose of discussion. Manual transmission Foresters do not have a "50/50" center differential so the front wheels are always directly driven, even if the rear driveshaft is removed entirely.

Remove the rear driveshaft, and fit a Tesla-style viscous adhesion air motor to the yoke in its place. Plumb the air motor into the engine exhaust with a transmission-linked bypass, so that there is negligible pressure when in neutral or reverse.

Now, you can also plumb an electric blower into the exhaust as well, between that bypass and the air motor. Clearly it would have to be a fairly large capacity one, but I've read that viscous adhesion devices can, in theory, see better than 90% efficiency so it wouldn't be too drastic. The electric blower would then supplement forward motion on battery power as well as the "recaptured" exhaust velocity - with relative simplicity and fault tolerance.

Pity no-one that I'm aware of mass produces viscous adhesion air motors - though similar devices are used as slurry pumps in mining.

[bwilson4web]

Originally Posted by MetroMPG

Sounds very interesting. I'd love to see someone try it.

I take it you're familiar with Mike D's . . . He's using a compact, permanent magnet (15hp peak, I think) compact Etek motor. You could twin a pair of those.

Thanks! This helps and I just found the web site:

Thunderstruck Motors - Description of page goes here. Short sentence that is keyword rich.

8 cont 18 pk hp - 38 lbs (owch!)

But I do like their specifications. A pair would give enough peak power to briefly handle higher speeds. Also the 8" OD is a challenge. However, located next to the strut fitting. Space is tight!

Originally Posted by MetroMPG

. . .
Somewhat closer to your description is the not yet released Poulsen plug-in hybrid system: . . .

That approach uses "pancake" permanent magnet motors attached to each of the rear wheels @ 72v nominal.

I'm more interested in their motor source but it is another, very practical approach. Combined with the rear wheel covers, it looks almost practical. But the press release I saw indicated they aren't quite in business yet.

Thanks! This is the type of information I was seeking. I like the "Et-RT" motors but I would add 80 lbs to the rear axle and in a space that is already constrained. A carbon-fiber beam might do the trick, essentially replacing the whole rear wheel assembly. At least there is enough engineering data I can do some sketches.

FYI, I am interested in for my NHW11, 2003 Prius:

That photo is from my work on Prius 4-wheel alignment using shims.

Thanks,
Bob Wilson

[MetroMPG]

Originally Posted by shovel

Begin with a 4wd or AWD vehicle ...
Remove the rear driveshaft...

It's funny - the idea of using an AWD or 4WD vehicle as a platform for a parallel hybrid conversion comes up all the time, but I've yet to see anyone actually do it.

But I have seen people make DIY hybrids using:

• a 5th wheel
• chain-driven rear wheel axle added to FWD car
• chain-driven FWD axle (coming soon)
• motor inline in a RWD driveshaft

[Coyote X]

an oddball idea I had but never did anything with was make a spacer that fit on the outside of the wheel with the lug nuts holding it in place. On the spacer put a sprocket of whatever size you wanted. In front of the tire drill a hole in the body and stick the motor shaft out the side of the car. There you go, an easy way to drive a back tire that will only look strange if you don't build a cover for it.

Lots of advantages to a setup like that. Easy maintenance and doesn't take much room up. Just a bit of the back seat at most. Still easy to maintain and repair the car. And if something breaks the worst needed is to use the lug wrench and take the sprocket and spacer off the rim. You would not even have to jack the car up to do it.

I figure since oddball ideas are being tossed out I might as well toss some of mine out there. Maybe someone might want to use it

[shovel]

Originally Posted by Coyote X

an oddball idea I had but never did anything with was make a spacer that fit on the outside of the wheel with the lug nuts holding it in place. On the spacer put a sprocket of whatever size you wanted. In front of the tire drill a hole in the body and stick the motor shaft out the side of the car. There you go, an easy way to drive a back tire that will only look strange if you don't build a cover for it.

Lots of advantages to a setup like that. Easy maintenance and doesn't take much room up. Just a bit of the back seat at most. Still easy to maintain and repair the car. And if something breaks the worst needed is to use the lug wrench and take the sprocket and spacer off the rim. You would not even have to jack the car up to do it.

I figure since oddball ideas are being tossed out I might as well toss some of mine out there. Maybe someone might want to use it

Oddly enough this does have some merit, but would definitely need a means of taking up slack when the suspension cycles... and fast. That idler sprocket would have to be under significant tension (to keep up with suspension rate) and would cost efficiency, despite being on the "slack side" of the chain.

You would probably also want to start with a vehicle that has a live rear axle (not driven, but rigid side-to-side as opposed to multilink - think Sciroccos) so that the wheel doesn't have much movement in/out as it moves up and down its suspension range of motion.

[MetroMPG]

Originally Posted by Coyote X

an oddball idea I had but never did anything with was make a spacer that fit on the outside of the wheel with the lug nuts holding it in place. On the spacer put a sprocket of whatever size you wanted. In front of the tire drill a hole in the body and stick the motor shaft out the side of the car. There you go, an easy way to drive a back tire that will only look strange if you don't build a cover for it.

Ignore the fact that the car is promoted as a perpetual motion device .

[tasdrouille]

Darin, this sure looks like the easiest and most flexible way to go I've seen yet.