Diesel electric truck in progress. Any thoughts?
 

I recently had a CAT motor fall into my lap (thankfully not literally), as well as an old Chevy 3500 chassis cab. I was watching the History Channel one night and saw a special on trains, and I got the idea to build a truck that ran like a train or an oil rig: a diesel motor running at a constant speed to produce electricity via generator to power elctronic motors. I have a few friends that are electrical engineers, mechanical engineers, and motor sports and robotics majors, and when I ran the idea by them, the were quite enthusiastic. When we were in high school, we started a club to compete in a super mileage contest. The car we built 3 years ago recently made 6800 MPG in a practice run in California with a Briggs and Stratton 3.5 hp lawn mower engine. So this idea was a novel high school runion for us.

If my friend's math was to be believed, I could theoretically get between 80 and 200 MPG (we measured fuel comsumption at 1,300 rpm and assumed an astronomical GVW of 9,000 lbs traveling at a constant 30 MPH with no wind.) Basically the only thing we couldn't measure was the drag co-efficient, hence the wide range in the estimate. The next step is deciding how to go about powering the wheels, either by one motor at each wheel or a central motor and a more conventional drievline. When we get some more solid ideas as to this, I'll post back with a more accurate estimate of FE.

Any thoughts would be appreciated.

It probably costs an arm and a leg but you should look into this:

https://www.pmlflightlink.com/news_volvo.html

https://www.pmlflightlink.com/archive/news_mini.html

https://www.pmlflightlink.com/motors/hipa_drive.html

That, sir, is exactly what I'm trying to do. Depending on how reliable the system is, I've been thinking of using this as my new snow plow truck. Electronic motors have the potential for nearly unlimited horse power, and with no brake pads or rotors to change? Sign me up. I'll keep everyone informed on our progress.

Cute avatar. :)

Electric motors have the potential for huge torque, not horsepower. They have that torque at 0rpm, great for a plow truck if you're willing to totally change the way you plow from the normal usage of momentum and speed to a slow push. It might take a little longer but it definitely has the potential to do a nicer job and less damage.

If I understand the concept correctly, the energy savings in the onboard-generator electric vehicle are a result of the ICE running at its most efficient speed/load combination at all times (storing the extra energy in batteries when it's not needed) and regenerative braking. I suspect that the engine you have is too big to do that efficiently without a HUGE amount of batteries and major fast-charging system costs. With a large engine you'd need to run it for a short time to charge lots of batteries and then kill it. With a smaller engine you could run it longer and have fewer batteries.

Having to accelerate all that weight would use a lot of energy.

You still have to have brake pads and rotors, regenerative braking isn't enough alone.

You can approximate the drag coefficient with a formula or calculator that is posted in some of the aero threads here. You do an experiment where you coast on level land in neutral for a set amount of distance and measure the amount of speed you lost. You feed that number, along with weight and maybe a couple others, into the formula/calc and get your drag.

resistance calc...
https://metrompg.com/tool-aero-rr.htm

Plugging numbers into that of 9000lbs, .01 rolling resistance (snow tires, possibly closer to .015, BFG LongTrail TA would be .008 ish though) 0.6 drag coefficient, (approx CD of a HMMV) and engine efficiency of 50% puts it at about 56mpg at 30mph.

I think keeping it simple would be a good idea. Just do a normal electric conversion (a manual transmission, an adapter plate, and a series-wound DC motor), minus the batteries and controller. You didn't say what sort of CAT you have, but you'll want to convert it to a 3-phase genset. Add a 3-phase rectifier and connect it to your motor. Then just rip out the genset's voltage controller and make your own, which will be your throttle (in conjunction with the engine speed control).

That would be a huge project, but it's doable and the truck would go. Then you can add batteries and another motor (inline-- electric racers sometimes do this). If you want regenerative braking, get an AC motor and controller, if not just use another DC motor.

Use the same system as one of those all hydraulic drive zero turn lawn mowers. Oc course that giant of an engine wouldnt have much work to do.

Motor-generator-battery-motor-wheel. While each component is fairly efficient the compounding of the ineffeciencies is substantail.

regards
gary

I have no problem throwing a camper shell on and dedicating the bed to batteries and capacitors. Run the motor for startup and to recharge only, with an onboard computer to make it automatic. My friends and have the skills we need. Now comes the question of whethpr not it's economically feasable and practical. Doesn't the government give away money to people for this?

Building an electric truck (such as those of alke) is not a simple task. Try to take a look at this link https://www.howtoelectriccar.com

I'll point out that the Chevy Volt is already doing it. It is always electrically driven. When its battery reaches some pre-determined discharge state, its on-board generator starts up to charge the battery, which in turn drives the motor and the car.

Railroad locomotives use the system, which can be thought of as either an electric locomotive with an on-board generating plant or as a diesel locomotive with an electric transmission. For locomotives, weight is a distinct advantage because tractive effort is a function of weight on the driving wheels times the friction coeficient of the steel wheels on the steel rails. By the way, the engines do not run at constant speed, except for the unit providing "house power" on passenger trains. Older locomotives use series-wound motors in the wheel trucks. Newer ones are starting to use AC motors and variable frequency inverters.

For plowing snow, zero speed isn't going to work. The limit is not power, but traction on the drive wheels. Any V-8 with an automatic transmission and 4WD can provide plenty of power. Even front-end loaders use speed and momentum, because otherwise they just spin their drive wheels.

The military experimented with electric drive decades ago. If each wheel uses an AC motor, and the motors are fed with AC, wheel spin is limited because the motors are pretty much synchronous with the incoming AC frequency.

Our WWII submarines also used the system, except they didn't have computers. Their engines drove generators. The generators could charge the batteries, or drive the electric motors which turned the sub's propellers. Underwater, the batteries drove the motors.