Ideas for a powered trailer.
 

As I was at work today, pulling a flat bed trailer, I got to thinking about what it would take to pull a trailer behind my electric car, my first thought was to plug in to the car and have a powered axle, then I got to thinking about the same idea only behind a gas car, of course at this point the batteries would be best as part of the trailer.
My thoughts for controls are along the same lines as the automatic brakes on some trailers, the hitch of the trailer extends and compresses and operates the brakes, a setup like this would work for throttle as well, only speed controllers can be programmed so instead of relying on mechanical dampening, the dampener and lag can be programmed in to off the shelf speed controllers, so a pull on the hitch will give the power source of the trailer a bit of throttle, a trailer like this could even be towed behind a bicycle if the throttle was sensitive enough, of course the braking is very important and with this type of set up could be easy because of regen braking with added mechanical braking for those times when you need to stop fast.
My first thought for building this is to build it off a golf cart, a two wheeled trailer could use just the rear end of the golf cart, for a bicycle a 4 wheeled trailer would be best because it wouldn't need to have tongue weight if it was set up like a wagon.
Big hold up is speed, my idea with a golf car would have a top speed of 30-40mph, weight should not be an issue because golf carts are designed to haul or people, so 600-800 pounds, plus the weight of the body, roof and the design of a golf cart having a low floor, that low floor being a weak point.
Another reference point is that Commuti-cars use a golf cart rear end and have a curb weight of 1,400 pounds or more plus the weight of cargo and two people, GEM Neighborhood electric vehicles come on a pickup version that can haul over half a ton with a total gross vehicle weight of 3,000 pounds fully loaded with people and cargo, again about 1,500 pounds of that is vehicle, so it seems to me that building a trailer that can power it's self for the most part, or assist at least and haul 1,000 pounds or more should be realistic, giving people with compact cars and light weight vehicles like bicycles, motorcycles and small electric cars a great deal of hauling capacity.

Pushing from behind, the trailer is going to try and push the lead vehicle sideways unless they are lined up perfectly.

With a wagon set up, you have 2 pivot points to worry about - the hitch and front axle pivot.

The railroad has been putting engines on the rear of trains, to reduce the amount of slack take-up, but I don't know how they manage the rear of the train being compressed and the front extended, slack wise, while topping hills and such. Trains do not have the steering issues a trailer would, (usually)! The Army Gamma-Goat, had a powered trailer driven by a driveshaft from the main unit.

I wouldn't think a trailer would get too squirrely unless one was applying lots of torque and/or on a low traction surface.

If the wagon was fwd perhaps it would behave similarly.

I don't want the trailer to push me, I want it to provide 95% of it's own forward propulsion, so you would feel some of the weight of the trailer behind you all the time but it would feel like a much lighter trailer then it is.
For example, I have a Burly brand bicycle trailer for behind my bicycle, it weights maybe 35-40 pounds, even with my 140 pound room mate in it it's not hard to tow on flat roads, but but that is about as much weight as I like to tow so say I want to haul lumber and tools behind my bike, or the idea of the larger trailer that could haul 1,000 pounds or more would work well for towing behind my civic vx as it's only rated to tow 1,000 pounds and any trailer has a bit of weight to it bringing the cargo weight down to 500 pounds or less.
The only time the trailer should push the lead vehicle is while it's braking, I would want a mechanical brake on the trailer along with the regen braking for this exact reason and with the programming of electric vehicle speed controllers the lag time you can program in should prevent the throttle from ramping up to quickly and running you over or pushing the vehicle side ways.

This seems to work.:)

http://www.mrsharkey.com/evgfx/push0.jpg

http://www.mrsharkey.com/pusher.htm

and this

http://www.jstraubel.com/EVpusher/pusher1.jpg

http://www.jstraubel.com/EVpusher/EVpusher.htm

yah, two wheel, one pivot point should work fine 99.99% of the time. well 100% of the time if you manage the EV power reserves so it is there also when you need it.

I wouldn't commute with it, but if I were going from city to city to show off my EV it would be about perfect.

You would have to spend a certain amount of time at your destination before it made sense to use it on regular trips, vs a non-electric hiway car that gets better hiway mileage. Do the math.

Those are nice pusher trailers but they can't be used for hauling anything, I'd like something that would work for hauling 4'x8'sheets of ply wood and lumber, or a half ton of dirt and I don't want to own, license, insure and store a pickup truck.

It is hard to imagine dedicated batteries on the trailer (expense). How often you use it becomes a factor (vs something you put together for a couple Benjamins that you limp around with on occasion).

How often it gets used depends on how well it works, I tend to barrow a truck once a month or so to haul stuff, a number of my neighbors have talked about buying trucks that would sit most of the time for those odd times that they have to haul stuff as well, so what is the cost of buying a truck? you can get something that is in rough shape for $1,500 and are going to spend alot of time and money keeping it on the road.
For my self I would do this because I already have the set of batteries and a spare commuti-car rear/drive axle that is good for moving 1,800 pounds down the road at 40mph when installed in an electric car and at a higher voltage should be good for 55mph, of course a SepEx motor would work much much better.
So for me it shouldn't cost more then $600 in parts and of course the time taken away from other projects and if I didn't have use of a truck that only costs me putting gas in it when I use it, I would be in a bigger hurry to build this, but I think it's a good solid idea that could work for people who are keeping a pickup truck and spending hundreds a year to license and insure it just so they can haul something heavy every few months, or if you look at why people spend $10,000 on a truck they often say that it is so they only have to own one vehicle even tho they only use it for hauling a few times a year, at that point the fuel savings alone would pay for a trailer like this.

One thing "nice" about having a little used gasser sitting around is, at most you suffer the loss of some gas fumes from extended sitting around, whereas lead acid batteries tend to go bad after so many years whether they got used a lot or not.

True, but I've also made a bit of money repairing friends trucks because they sat for a few weeks found that they wouldn't start, stop or were no longer safe to drive, because gas vehicles don't like sitting either, so why not have a trailer and share it so it gets used, the savings in not having a 2nd vehicle licensed and insured would more then pay for a new set of batteries every 5 years and it could end up costing less then buying a cheap small truck.

Shared anything would result in less down time.

I fear I'm going to have to replace the battery pack on my electric bicycle prematurely simply because it sat around so long before I got it; it sits all winter now that I have it; and I don't use it daily. So then the cost/mile equation sux even more vs ICE.

FLA batteries have a fairly intensive maintenance routine, charge level, water quality and level, corrosion, cables, and even more so when sitting idle and in cold climates. Might be a good application for Super-capacitors, charge up quick when you need to go to Home Depot, regen brake assist, light weight.

Having grown up in an off grid how with lead acid batteries, having two electric cars with lead acid batteries and working at a job where I take care of the electric fork lift with lead acid batteries, it's a few minutes per year of topping off the water and looking at the connections, same thing you have to do with the battery on a gas vehicle, more so with a gas vehicle that tends to sit for weeks or months at a time.
I also checked with my parents, who's truck is one of two that I barrow when I need to haul heavy stuff, they spend a total of $275 a year just on licensing and insuring and another $100-200 (documented by my accountant mother) on home oil changes, exhaust repairs and other basic up keep on a vehicle that gets less then 2,000 miles of use per year and is used by 5 of us, plus the folks we help out with moving and other tasks.

Super Capacitors would be nice, but plugging in to a 220v 40amp plug for half an hour or more, running at full draw would be required to charge.
But keeping the batteries topped off and happy is a requirement, this could be done either with a small solar panel or by leaving it plugged in to a maintenance charger.

What is preventing you from taking the idea of a pusher trailer and designing one that can be used to haul cargo??

I too live off grid, 15 + years and managed to get 10 fairly good years, out of one set of L-16's, with less than great mantenance, and poor conditions, just an open shed. They got snow and rain on them, cold to 12 degrees and hot to 105. They did need the cables removed and cleaned yearly, water monthly.

A pusher trailer works well with an electric car because you can use regen braking to slow the trailer down and from your electric car more or less drive just throttle the trailer.
If you tried to use a pusher trailer behind a gasoline car I think you would spend alot of time ridding the brakes and trying to run two throttles because the pusher would be moving it's own weight, the weight of the cargo and the weight of the lead vehicle.
The idea of an electric self powered trailer is that you can have the throttle as part of a telescopic hitch and instead of needing a hand throttle inside the vehicle allowing you to focus on driving and making sure that your load is staying secure, also with electronic throttles you can program in the lag time that would take away any jerky-ness and going down hills or coming to a stop would kick in regen braking.
Also an electric trailer would cut your gasoline use, allowing a 50mpg car to still get 50mpg while hauling a ton of dirt.

the VW pusher works well, ive seen it in person at the solwest show in john day Oregon a few years back.

granted one year he learnd the hard way, about head repair. he was redoing the head all week end do to a coolent leak:eek: he had a temp gauge but he did'int know the fluid was low.....:(

he called it his weekend engine repair class
Oregon Solwest Renewable Energy Resources and Fairs home


his set up has one BIG draw back......hes using a auto trans :( it does not have a locking converter, or a tall top gear.....

Why not get a utility trailer with a 4'x8' deck with removeable wood sides(like I have) and mount some kind of generator unit between the deck and the hitch?
I think I will have to pay $10 of $15 per year for my trailer (had it for less than a year so I am not sure) if it wasn't a one time fee.
That little area is usually just wasted space any way, some people put tool boxes there and that is about it (me).
It would be real easy to wire in remote controles to your car to start the generator and apply power as needed, such as when the batteries start to get low or you have a big hill to get over. The cheapest way to get the most power out of a generator for charging big high power battery banks while under load is a varrac and rectifier array.
Sounds like you could use the remote power of a generator at job sites too.
I would try to avoid battery banks that could end up sitting around and not being used on a very regular basis as much as possible.

The three factors that affect a car's towing capacity are power, braking and weight. Power and braking you can handle on the trailer end, but weight (specifically, the frame and mounting points for the hitch) would probably be an issue. Even if you perfectly balanced the trailer to have little or no tongue weight, a too-heavy trailer might still tear off the rear of the car if the weight shifts.

How much weight are you thinking about hauling, and are you talking about the Commutacar specifically? Does it even have a solid metal mounting point?

As for a pusher trailer, maybe one of those truck-bed trailers? Keep the differential and mount the motor and batteries underneath the bed. It already has brakes and running gear, and those things are always running around, so the cops won't give it a second look (unlike, say, the rear of a Beetle hitched to your car.)

I'd be hard-pressed to think of any vehicle less suitable to pull a trailer than a CommutaCar, so can only say- go for it! I've countered similar doubts in adding a 2" receiver hitch to my electric Karmann Ghia, with the intention of first pulling a genset for range extension, and then a pusher trailer. Of course, everything else on the car was beefed up first, and I'd much rather having more power (or regen) on tap at all times rather than leave it sitting on the trailer 95% of the time... updates soon at the karmanneclectric blogspot. However, I do think that your idea of balanced trailer assist has merit, in that an AC drive could be combined with a surge brake assembly on the trailer tongue, such that the (former) master cylinger piston constantly signals the motor to assist or regen automatically, keeping whatever amount of drag on the tongue that is dialed in via a balancing spring. Some e-bikes do this with pressure sensors, I think in the pedals...

Awesome. If I ever had a travel trailer, I'd figure out how to rig up an alternator or generator head to the trailer brake controller to recharge the house batteries while decelerating. Why waste it?

If and when I do end up building this (I'm not finding any electric golf carts for less then $1,000 right now) I would like it to be a 4 wheeled trailer so non of the trailer weight is on the hitch, this way I could tow it behind any vehicle including a bicycle or my commuti-car, the commuti-car has solid mounting points to the aluminum roll cage that the bumper shocks are mounted to, I have a tow bar for towing this car behind another vehicle that mount on to those points and a trailer hitch could attach the same way only in the rear.
for towing a trailer like this behind a bicycle the sensitivity of the controls would need to be adjusted so it doesn't push you over, but I've hauled adults with my child hauling trailer without issue and a bicycle is going to be going much slower then a car.
At that point, with a 4 wheeled trailer, the big worry would be that the steering is tight and maintained so that you don't have it fish tailing.

At this point this project is more of a big dream then anything else, mostly due to time and money, but I plan to keep my eyes open for good deals on the parts I'd need, or if anyone else wants to take on a project like this I'd be more then happy to give input.

Many years ago there were tractor-trailers used on the west coast that had pusher engines (gas usually) mounted on the trailers to help push the rigs up grades. In the east, modified pick-up trucks were used to help push the rigs up the grades. Both were fraught with problems in that sometimes the pushing was going on at the same time stopping was being attempted.

Twin engine motor-graders had the same sorts of issues.

That said, work out the controls and it should work just fine. The pushing was never the problem-- the problem was in controlling the pusher. Those old rigs used lots of cables that rusted, got stuck or broke. Modern electronics could eliminate those concerns.

Me, I'm wishing I could afford to replace the rear wheels on my Tercel with hub motors and a few batteries.

When I figure came up with an idea like this years ago, I thought I was going to have to make all of the controls mechanical and figure out ways to dampen and fine tune them, then I started reading about the programming in solid state speed controllers and all of those issues are solved in the controller settings so by having the trailer powered while you are trying to brake and so on will be taken care of because the braking and the power are all controlled by the same device, the speed controller, there will of course be a manual over ride brake that will cut power to the wheels for when you want to come to a complete solid stop.

Trailer Towing
 

Ryland:

A comment if I may, regarding the inter-vehicle control process.

Presuming that the trailer propulsion can be controlled electronically, an accelerometer can be used to determine the push/pull differential between the tow vehicle and the trailer.

I designed a microcontroller application that uses a three axis (X, Y & Z) accelerometer, in conjunction with a tow vehicle master cylinder’s pressure transducer for our 5th wheel trailer.

As a result and within reasonable towing speeds, the trailer provides its own braking such that its braking rate equals the tow vehicle’s braking.

The microcontroller code can be edited to provide desired relative braking rates and timing.

You may want to consider such a methodology to control the trailer assisting power and also to match its braking rate with the tow vehicle.

Regards,

Bob425

I know! Ride in the trailer and drive it from there! :p

Various prototypes:
http://foolery.typepad.com/photos/un.../donkeycar.jpg
The four-wheel version:
http://www.cybersalt.org/images/funn...arbackfire.jpg

Bob Wilson

In The Interest Of Safety
 

You probably already know this but as a lot of people don't understand braking I thought I'd add:

A common misconception is that the trailer brakes need to apply before the brakes on the towing vehicle. Brakes should work from front to back, steering first, rear wheels on vehicle second and trailer brakes last. Of course, this all takes place in less than a second.

The most common causes of jackknifes are applying the trailer brakes first, only or too much.

Vehicles designed for towing are set us so that this is automatic. Of course, some drivers circumvent this by the use of what is commonly called a trolly brake. The trolly brake only works the trailer axles.

The real reason for the trolly brake is to test the trailer brakes when coupling to the trailer. Many companies spec their trucks (power units) without trolley brakes because many drivers don't understand the real purpose of the trolley brake and cause jackknives they could have avoided with less effort.

I actually just saw one the other day for 500, but it needed batteries. Sucks you're so far away!

here's my suggestion -
use a 7 way trailer connecting harness from your 'towing' vehicle, and put in a standard trailer brake controller. Use the output from the brakelight switch to interrupt the power from the pushing motor, and then use the standard electric trailer brakes to do most of your braking. This would also allow you to keep the pushing motor off for maneuvers where it coming on would be unsafe by riding the brakes.

use a second TBC turned the other way to increase or decrease the power from the trailer motor - TBC's have variable output on them, are based off a pendulum, and should be very receptive to changes in acceleration. It's also helpful that nearly all of them have a manual activation switch, use that if your towing vehicle just doesn't have enough "go" to start moving.

Use the "reverse lights" pin on the 7 way connector for your trailer power signal connector - There's hardly any vehicles in north america with reverse lights on the trailer