Electric fifth wheel (DIY through the road parallel hybrid) - Fuel Economy, Hypermiling, EcoModding News and Forum

friedlbug · 02-26-2008, 07:57 PM

Well, it's a bit ambitious for a second post, but I thought I'd get down to what got me here in the first place - an electric pusher for my Yaris - not to drive as an EV but to get it moving and beat enertia. What I'm thinking is that a very simple pusher could be made that would connect to a hidden hitch with square tube, come to a hinge, and an extension of square tube would extend from the hinge to a wheel (motorcycle, mountain bike, not sure yet). A spring in some configuration would hold the wheel down. The next part depends on the force needed to get the yaris moving - either a permanent magnet motor (perhaps a power steering motor), or a truck starter would directly drive the wheel. A battery will be kept in the trunk and completely separated from the car electrical system. If a permanent magnet motor is used, I hope it to regen the battery will the car is running. If a starter is used, I'll depend on it's solenoid to keep it from being turned while not engaged. I'm not sure about the recharging in that scenario. It might just require a deep cycle battery and a charger.

Problems up front:

Stir in the numbers - I'm going to have to determine what forces are involved and how fast the car is to get moving before shifting into gear and using gas.

The Yaris is under warranty - the whole works comes right off and leaves no trace excpt for the hitch. Problem is, Toyota "doesn't recommend" towing with the Yaris in the US. They even "don't recommend" using a hitch-mounted bike carrier. The exact same car in Canada can tow with Toyota's blessing, and they even sell a hitch for it.

So, I'd check with my dealership and see if they'll hold me not being able to use a hitch-mounted bike rack (or something).

Daox · 02-26-2008, 08:02 PM

If your doing a lot of city driving I can see this possibly being useful. However, if you do mostly highway I don't see anywhere near the gains.

Do you do your own fabrication?

Also, your going to need a lot more than one 12v battery to make any sort of dent in your mileage.

friedlbug · 02-26-2008, 08:40 PM

Yeah, the more I look at it, I'd lurch forward and still have to accelerate almost as much. Plus, it wouldn't be PennDOT legal. Back to lurking for now.

MetroMPG · 02-26-2008, 10:03 PM

This is an idea I keep dreaming about as well. Realistically, I have enough on my plate that I probably won't ever do it, but it's fun exercising the synapses...

Have you seen Mike D's e-5th wheel on his Insight? (I'm assuming so).

He started out with a child's bike frame/wheel and an old wheelchair motor, if I recall correctly. Though he's since upgraded to an Etek PM motor and a beefier scooter type wheel/tire.

I missed out on a used 24/36v 400A golf cart controller on eBay today that would have been ideal for testing something like this. It went for 30 bucks. (DRAT!)

MetroMPG · 02-26-2008, 10:05 PM

I should have added: whether or not this will be practical or useful all depends on how you define your goals.

It probably won't ever pay for itself in fuel savings, since you'll be wearing out batteries while saving a very small amount of fuel.

MD2000 · 02-27-2008, 06:14 PM

I initially was thinking of using the 5th wheel to do gas off acceleration, but even the e-tek motor, with a 4:1 reduction,and 200A draw, the acceleration was slower than I was comfortable with. In normal traffic I tend to accelerate with the gas, then turn off the engine and cruise with the 5th wheel, if the traffic speed is less than mu 30 mph EV max. My record is 42 miles on a full charge with an average speed of 26 MPH, on a deserted secondary highway.

Also check out Hybrid adapter:
http://peswiki.com/index.php/Hybrid_Adapter

This concept could turn any car into a hybrid.

MetroMPG · 02-27-2008, 07:07 PM

Welcome to the forum, Mike!

I can't tell you how many people I've shown your e-5th wheel.

Quote:

Originally Posted by MD2000

I initially was thinking of using the 5th wheel to do gas off acceleration, but even the e-tek motor, with a 4:1 reduction,and 200A draw, the acceleration was slower than I was comfortable with.

I'd be curious to know if you measured your acceleration time, say 0-30. I imagine it's a bit better than what we ended up with in the ForkenSwift, which has similar specs: 2100 lbs, 48v, 225A Curtis controller. I'll have to go look it up...

Here it is: 0-50 km/h (31 mph) took 36 seconds, fresh off the charger, in warm weather (happy batteries).

It's significantly slower in winter temps. Having said that, I try to choose my route to avoid holding people up, and I'll pull over and wait for traffic to clear if I think a line is going to form behind me (e.g. heading up a grade from a standstill).

In over 750+ km of use, nobody's ever honked at me, and only once has someone "roared" around me in a no-passing area (which says as much about where I live as my efforts not to hold people up.)

MD2000 · 02-27-2008, 07:31 PM

The issue is available torque, and traction.
The scooter tire is basically a slick (it was free).I have about 140 lbs of down force on the wheel. If I am on sand or gravel, the e-wheel is like a great pitching machine for stones,

so I tend not to use it if someone is behind me.

On my 42 mile test run, I did not run the gas engine except for an occasional 10-30 seconds to replenish the power brake vacuum. (need a small vac pump).

Acceleration on flat or down sloping starts was reasonable, and probably a bit faster than your 36 seconds, but it was painfully slow, and waste lots of amps to try and accelerate up a grade from a stop. If the drive had a 2-3 speed tranny it would probably have no problems, but my fixed 4:1 and my heavy Insight (extra 400 lbs of batteries and e-wheel), are just a bit much for the little e-tek.
Once moving, with the low rolling resistance tires, pumped up to 45 PSI, I was very impressed with the e-wheels ability to climb hills. A hill that I would have had to downshift to climb with the gas engine only dropped my speed from 30MPH to 24MPH.

If they come up with a higher power Nuvinc drive:
http://www.fallbrooktech.com/NuVinci.asp
I would consider using one in the e-wheel.
I just acquired a Honda Insight IMA motor, which may find it self replacing the e-tek sometime later this year.
http://www.99mpg.com/workshops/mikessaturdayhybri/

Too many projects not enough time or money.

basjoos · 02-27-2008, 08:25 PM

I've thought about building a complete stand-alone EV propulsion system (batteries, controller, and motor) onto a small flatbed trailer that I could hitch up behind my car and whose electric motor would power the trailer's wheels. It could be charged up at home (or on the road by regenerative braking) and would propel my car in low to moderate speed city and suburban driving. I would control it wirelessly via an R/C controller and actuator, so there would be no dedicated EV wiring in the car and I could hook it up to any of my cars that had a trailer hitch (the trailer would just have the usual tail/brake lights connector on it). It'd be a way to get EV capacity without having to build a dedicated EV vehicle.

friedlbug · 02-27-2008, 10:39 PM

I had originally planned to use a starter motor on my existing elctrical system and just swap the battery to some thing larger. My only purpose was to get the car moving and beat inertia. I firgured the initial push would be similar to the normal duty cycle of a large starter, and thus run on a normal 12v system. I toyed with theidea of a flywheel type gear/sprocket on one of the four wheels, and ultimately considered the fifth wheel idea. I guess it all depends on how much accelerating from a stop affects gas milage for someone who already hypermiles.