"Pusher" Trailer Design / Control Logic

[sendler2112]

A CVT motorcycle hitch hauler pusher with a CVT scooter would be very simple to rig up. With very little financial risk if it doesn't work out. The hitch hauler is $70. The used bike can be sold for what you paid for it. You would be out some kind of throttle control like a cable housing rig to run through the hatch. Or an RC transmitter and a servo.
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A PCX is a really nice machine. Every able bodied person on the planet should have one as a means of transportation in addition to their car basically. But it doesn't have enough top speed in it's gearing. Under a heavy load like that it might not break 55 mph since the CVT will wind down a bit. And it might overrev on the down hills. You will want to pick a bike that can have an automotive tire mounted on the rear to get better life.
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An NC700 with dual clutch auto trans would be deluxe. Dream come true pusher. Perfect power output for unlimited range. Highest BSFC moto engine ever made. By a long shot. And very clean with it's giant cat right off the head and O2 sensor. Auto trans. You could get good at popping the front sprocket off to tie the chain off of the rear if you were in an area that didn't need the bike running.
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But a single wheeled pusher won't work at all on snowy roads with slush down the center.
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http://www.northerntool.com/shop/tools/product_200409163_200409163?cm_mmc=Google-pla&utm_source=Google_PLA&utm_medium=Trailers%20%2B%20Towing%20%3E%20Motorcycle%20Hauling%20Accessories&utm_campaign=Ultra-Tow&utm_content=571648&gclid=Cj0KEQiAt9vEBRDQmPSow-q5gs8BEiQAaWSEDlL96IoM-X7wH90u63n9yRqmi-yebvOGrJGUQiBO5hYaAuFF8P8HAQ

 

[DuncanCunningham]

well, look who turned up outside my work on Thursday? He uses a pusher trailer to get him over those longer freeway distances. Doesnt have to rent another car but makes the trip by pushing his EV with this solution. He took me on a ride and this trailer gently keeps his car moving along at speeds above 56mph up to 70mph. He can use regen or hit the brakes to kill the coil and stop the pushing. He has a very simple setup.

He name is Hugh Glass. He is as nutty as I wish I was.

 

[jjeff]

Interesting, what is he pushing, not a Leaf for sure, is it an BEV?
Also did he have a ballpark figure to what MPG it would get running on pusher trailer power alone? it would be interesting to know and I know it would vary by vehicle weight among other things but maybe with a Leaf just 60-65 MPH going down the freeway.
Did he say if he had to add extra weight over the axle and lastly did he say what the vehicle tongue weight was?

 

[rmay635703]

The Imiev with a nearly identical pusher got 25-35mpg with an old VW driving.

That said there is a lot of efficiency left on the table even if you stick with a VW platform.

 

[DuncanCunningham]

My VW bug used to give me 33mpg but this guy has the throttle fully open and only uses it on the freeway. Ice motors usually have their highest efficiency at higher speed on fullish throttle and EVs best in town and speeds below 40 according to the smartest people who I try to learn from.

I think Hugh gets about 25mpg. If he tuned it up for full throttle only then he could get more out of it. It's a work in progress.

I'm happy to share his contact info, let me check with him first. His work on it is in the same kind of direction as the diagrams shared.

I have a VW bug that I could pull apart and make in to a pusher. I didn't think it was viable until he took me on a test drive.

 

[IssacZachary]

There are lots of people who have used VW air-cooled engines for pushers including J B Straubel, CTO of Tesla. (Makes me want to take apart my 1972 VW Beetle instead of selling the thing.) An engine of that size only needs a simple on/off/start control.

 

[VitaminJ]

I have a Subaru. It also gets 25mpg. I can use it to tow a trailer or carry dogs or big things.

 

[VitaminJ]

There are lots of people who have used VW air-cooled engines for pushers including J B Straubel, CTO of Tesla. (Makes me want to take apart my 1972 VW Beetle instead of selling the thing.) An engine of that size only needs a simple on/off/start control.

His was a water-cooled, fuel injected VW engine FYI (that still only got 25mpg)

 

[DuncanCunningham]

I have a Subaru. It also gets 25mpg. I can use it to tow a trailer or carry dogs or big things.

big things like an EV. The things to consider are. You don't need to license it. No registration. No tax. No insurance. Only the gasoline. Or get a BMW rex, which I'd love to do.

 

[VitaminJ]

Where I live you indeed do need to register and insure a trailer, and pay tax. And I park the Subaru next to the house for 9/10 of the year, no gas cost then, incredibly reduced maintenance cost (same as trailer would need), and it's far more useful when I do use it. Insuring it for 5 years costs less than the cost of building a pusher trailer and it's far safer and more convenient.

 

[DuncanCunningham]

Where I live you indeed do need to register and insure a trailer, and pay tax. And I park the Subaru next to the house for 9/10 of the year, no gas cost then, incredibly reduced maintenance cost (same as trailer would need), and it's far more useful when I do use it. Insuring it for 5 years costs less than the cost of building a pusher trailer and it's far safer and more convenient.

sorry for you.

I guess you don't need a pusher trailer then.

 

[evtinker]

I built a pusher trailer for my homebuilt Civic conversion. It was made from the front end of a 1990 Civic. It worked, the concept was functional, but in the end I only used it a few times. The limitations of the conversion and the improvised nature of the pusher meant I never was really comfortable taking it on a long trip. The longest drives could now be completed by my Leaf on one charge. I have what is left of it, but it is destined for the scrap heap. It really was more of a proof of concept rather than a fully functional solution. I never tried to use it with my Leaf.

I think if I were to do another one, I would try to make it look like and function as a utility trailer. Maybe something like a 4x6 trailer with the say a 300-400 CC water cooled ATV engine mounted out of sight under the bed driving the wheels. I think the controls could be pretty simple, maybe set up so the trailer supplied almost all the power and the Leaf on cruise control would make up the rest.

The Leaf is so nice to drive on the highway that the idea of being able to take it on a road trip would be awesome. I suppose if I had more time I might try building another pusher, but the house remodel has my hands full.

If you are curious about the pusher, it is listed in the EV Photo Album at:

http://www.evalbum.com/753

 

[IssacZachary]

There are lots of people who have used VW air-cooled engines for pushers including J B Straubel, CTO of Tesla. (Makes me want to take apart my 1972 VW Beetle instead of selling the thing.) An engine of that size only needs a simple on/off/start control.

His was a water-cooled, fuel injected VW engine FYI (that still only got 25mpg)

From what I understand he did both. Once with an air-cooled VW engine and once with a water-cooled VW engine.

Reference:
JB's Home Page

(Returning to the original topic)
Here are some clutch pros and cons:

• Any automotive engine/transaxle arrangement is designed for the driver to shift into neutral and let off the clutch when engine power isn't needed for any extended period of time.
  • However, if the clutch is depressed and the engine shut off this would eliminate throw-out and thrust bearing wear, although there still would be pilot bearing wear and possible clutch friction, although some designs, such as the transverse VW transaxles with the clutch push-rod running through the entire length of the main shaft, might have other problems if only the clutch were used to keep the engine disengaged.
• All automatic and some manual transaxles require the engine to be running in order to pump lubrication throughout the transaxle. But most manual transaxles do not. This gives you three options.
  1. Never be able to turn off the pusher engine
  2. Have to use a manual transmission
  3. Or invent some sort of auxiliary lubrication pump that doesn't need the engine to be on for it to lubricate the transaxle.
• Having many gears isn't necessary since the electric vehicle can do all the acceleration with the pusher engine supplying cruising power only.
  • Unless you need your engine to provide acceleration or hill climbing capabilities or to push over a very large range of speeds.
• If you don't need several gears, the other gears can be removed from the transaxle, or the whole setup can be replaced by a simple chain drive.
• On a chain drive a centrifugal clutch could be used, but wouldn't give you the control characteristics needed for controlling a pusher trailer. It would likely latch on and keep turning the engine at highway speeds and not be much different than just a direct drive without a clutch.
• A direct drive could be a viable option. It's simple and would provide some engine braking anytime you turn off the pusher engine. It would also not require any starter since the engine would start with the acceleration caused by the electric vehicle
• Another simple idea is a sprag clutch. There are sprag clutches that can handle the torque and speed of a 30kW pusher engine and are designed for a very long life. The main disadvantage with a sprag clutch is that there aren't any bolt on sprag clutches desiged to fit an engine, be it small or large. You'd have to do some machining to get it to work.

 

[IssacZachary]

Of course if you design the pusher transaxle with an existing engine/transaxle setup you can have a two-wheeled trailer. But if you do a chain drive you either will have to make a one-wheeled trailer or add some sort of a differential. Here are a few that I have found:

http://www.northerntool.com/shop/tools/product_35768_35768

http://www.cyclexchange.net/Honda Trike Page.htm

http://www.rpmgearboxes.com/

 

[IssacZachary]

Further, assume this motor [...] is NOT a diesel (LPG, CNG, or gasoline).

I must disagree. Why not consider a diesel engine? The pros and cons of using a diesel engine would be that it would be more expensive to build and more difficult to keep emissions low, but diesel engines can be made to get the same emissions, be more efficient, require less maintenance and be more reliable than other types of engines. If you don't have any emissions equipment on an engine (e.g. small non-road use air-cooled engine) a diesel engine might actually get better overall emissions than a gasoline engine.

I think any engine or motor could be used for a pusher trailer. But yes, I agree that if you're putting an engine on an electric vehicle, it would be best to try to meet the emissions requirements that vehicle would have had to meet had it been a fuel powered vehicle, as well as try to keep it as efficient as possible and keep the costs low.

• Internal combustion engine
  • Fuel type
    • Gasoline/petrol
    • Propane
    • Methane
    • Diesel
    • Wood gas
    • Etc.
  • Configuration
    • 4 stroke
    • 2 stroke
    • Atkins cycle
    • Miller cycle
    • Wankel
    • Gas turbine

• Heat engine
  • Configurations
    • Stirling
      • Alpha
      • Beta
    • Steam
      • Single/double acting
      • Simple
      • Uniflow
      • Compound (double, triple, quadruple)
      • Turbine
      • Rotary
  • Heat source
    • Fuel
    • Nuclear
• Liquid nitrogen motors
  • Stirling
  • Air motor
• Electric pusher trailer
  • Secondary (rechargeable) battery
  • Primary (non-rechargeable) battery
  • Fuel cell

Obviously each engine/motor type has its own advantages and disadvantages, and that's not the objective of this thread. But the type and power of such engine/motor will change the logic control that can and needs to be used.

 

[JRay3]

OMG, I don’t visit forums often anymore, but when I do, I’m always amazed by the overwrought angst and more time spent on armchair engineering that it would’ve taken to actually build and then iterate something!
I’m building my 3rd pusher trailer right now, because they do indeed work so well, and have been collaborating with the aforementioned Hugh and Mr Sharkey for many years. My first pusher was the resurrection of JB Straubel’s red Beetle butt, till I blew up the engine on a 102 degree day. That trailer is now in the Historic EV Foundation collection in Kingman AZ.

The second pusher was built around that black wishbone subframe from a Type 3 VW which Tony posted above. It is lighter in weight, has a useful cargo deck on top, plus load bars to carry a rooftop tent and makes a fine camping trailer, enabling my I-MiEV to climb high into the mountains.
https://karmanneclectric.blogspot.com/2018/12/even-rangy-ier.html?m=1

The current effort adds aesthetics and aero that others lacked, plus weathertight storage.
I give you, the Headless Ghia!
http://karmanneclectric.blogspot.com/2022/11/getting-rangy-yet-again-with-some-style.html?m=1

So many points above to address, but I’ll try to do so briefly.

1- the original subject; Control. It’ll be binary, engine ON or OFF with fixed throttle somewhere close to wide open. JB had developed a stepper motor control for the throttle that corroded away, then I abandoned my fancy control pendant in favor of a simple cigarette lighter plug-in for ignition coil power (which also releases the fuel shutoff solenoid, providing full engine braking). Clutch action was previously accomplished with a linear actuator, which was slow, clunky and vulnerable to water intrusion from all the road spray. This time I plan to use a vacuum-actuated cylinder to pull in the clutch, with plan B being Hugh’s method of an airbrake bellows from a truck (with compressed air tank replenished at truck stops or via a 12V compressor).

2- Brakes. None needed on a lightweight trailer with strong engine braking, tow vehicle regen, and the tow vehicle friction brakes. Being an EV with strong regen, this offers that rare opportunity to polish the rust-pitting off my rotors!

3- Power and Efficiency: 200% of original power is just right for an I-MiEV, per the following experience: https://myimiev.com/forum/viewtopic.php?p=23137&sid=16b51f8c0001981797e46623cd624290#p23137
MPG of a through-the-road hybrid setup will nEVer be optimal, especially with an obsolete engine. I never saw better than 25 mpg in continuous pushing, but using most of a battery charge for the unpushed beginning and end of a journey really raises those numbers. For instance, if I drive 20 miles to the highway in EV mode, push for 100 miles at 25 mpg, and then switch back to silent running for the final 20 miles, that’s 140 miles on 4 gallons for 35 mpg, plus about 14 kWh from the grid. Sure, I could do that in a 40 kWh LEAF, but it’s still better than most gassers, and not bad for an EV rated at 62 miles of range when I last actually spent real money on the thing, 11 years and 140,000 miles ago…

4- Stability and driving dynamics. EVen JB’s dragass bug butt only weighed 460 lb, so notta lotta tail to wag that dog, but EVen after I shortened the tongue to the minimum length that would still allow 90 degree turns without bumper contact (useful for backing into charging stations), the trailer nEVer fishtailed, tried to jackknife, or made the tow vehicle feel less stable, whether pushing or unpowered. Believe it or not, highway driving with up to 49 kW pushing on your trailer ball is smoother than without. (The I-MiEV short wheelbase tends to hobby-horse over concrete highways, and the pusher greatly reduced that). I tried sEVeral throttle configurations, and EVentually locked in a setting that balanced at zero EV battery amps while cruising at 65 mph on level ground. Higher speed or going uphill would require a bit of discharge, and downhills plus “downshifting” to E or B mode would pour in the regen. I could drive all day with no net change in SOC if desired, but of course usually preferred to hit the final destination around 20%, having shut down the pusher about 35 miles before the finish line if charging would be available.
Traction on such a lightweight pusher was no issue either, with the tranny locked into 4th gear and only employed at highway speeds.

5- Wear and Tear. Gotta laugh at comments like “hitches are designed for pulling, not pushing”. The steel doesn’t care, and the receiver is just as strong either way. Try to find a hitch or car that crumpled because the driver braked too hard! Nevertheless, regular inspections and greasing of the hitch coupler are in order. Hugh uses a Bulldog collar-lock coupler to eliminate the concern over a worn locking tab, but I haven’t. Road spray and grit will completely coat all trailer components, so weatherproofing is paramount. Lastly, the pusher is only used for a small percentage of annual miles driven, though it can eliminate the urge to keep an extra Subaru on hand!

6-Sacrilege. No, I didn’t butcher a beautiful Karmann Ghia for this project, I rescued one from the scrap heap, like JB and Sharkey did with their Beetle and Rabbit pushers. Just as any critic of classic EV conversions is full of hot air, I’d challenge the critics to put up, or shut up.

-Jay Donnaway
President, Seattle EV Association