# Adapting Trailer to be have an Electric Assist Axle



## electro wrks (Mar 5, 2012)

Can you reference the ones in Europe?


----------



## Korishan (8 mo ago)

electro wrks said:


> Can you reference the ones in Europe?


This is one that I found. There were a few others








Dethleffs puts a new spin on towing with an electric camping trailer that nearly drives itself


Last year, Dethleffs shook up the motorhome world when it debuted the E.Home concept, an all-electric motorhome covered in solar panels. At that very same Düsseldorf show, it revealed the curvy, lightweight Coco caravan concept. Fast-forward a year, and Dethleffs has smashed those two concepts…




newatlas.com












Thor pushes forward with self-propelled electric camping trailer


The groundbreaking Dethleffs E.Home Coco camping trailer has taken another big step toward reality. Parent company Thor Industries and German automotive supplier ZF Friedrichshafen are teaming up to clear the hurdles that stand in the way of a viable production trailer that uses electric motive…




newatlas.com






https://cleantechnica.com/2021/08/10/dethleff-introduces-the-e-home-caravan-a-self-powered-camping-trailer/



I know these are all the same company. So maybe it's something relatively new and this one company is making this move. A few weeks ago I did a search and I had found some others as well. Maybe they weren't German, but another country that was making them. As one of them was a full RV trailer, not one of these camper trailers.


----------



## 94Tracker (Jan 17, 2011)

I think there will be high demand for this, however it's so new it will be expensive. The liability issues that would come from a DIY version are scary for me. Can you imagine if the trailer pushed itself into a crash? I really want this for my camper and other trailers but the tech to make it work safely wow.


----------



## remy_martian (Feb 4, 2019)

This topic has been discussed on this forum already fairly recently.

Please do a search to further that discussion vs scattering the topic all over the forum, making it difficult for those in future to land on ONE topic vs dozens. 

Assuming, of course, they do a search first like they are supposed to.


----------



## Korishan (8 mo ago)

remy_martian said:


> This topic has been discussed on this forum already fairly recently.
> 
> Please do a search to further that discussion vs scattering the topic all over the forum, making it difficult for those in future to land on ONE topic vs dozens.
> 
> Assuming, of course, they do a search first like they are supposed to.


I only found 1 post about a vehicle electric trailer assist. The other posts listed electric brakes, electric plugs, or for a bike. If the OP's of those threads used some obscure title for their post instead of a descriptive one, that kinda makes it difficult for others to search for the topic as well.

And that one thread only barely discussed it, and from 2011. Unless i'm not using the right keywords to find the results. If keywords to help me out could be given, I'd be more than glad to look at other threads. But as I mentioned, I'm just starting out and I am unaware of all the terminology. For instance, I didn't know that a mid-shaft electric motor was called a "P4 Hybrid". I know this now so I can look for those threads.


----------



## kennybobby (Aug 10, 2012)

From the article:
"The most critical part of the eTrailer design is the electronic sensor and control system that keeps the trailer operating at the same speed as the tow vehicle, cutting the tow load without negatively affecting the safety, ride or handling."

Sounds like an interesting research project, not sure if it's ready for prime time or diy though.

From the picture it shows the motor inboard of the wheel and brake, clever design.


----------



## remy_martian (Feb 4, 2019)

Korishan said:


> I only found 1 post about a vehicle electric trailer assist. The other posts listed electric brakes, electric plugs, or for a bike. If the OP's of those threads used some obscure title for their post instead of a descriptive one, that kinda makes it difficult for others to search for the topic as well.
> 
> And that one thread only barely discussed it, and from 2011. Unless i'm not using the right keywords to find the results. If keywords to help me out could be given, I'd be more than glad to look at other threads. But as I mentioned, I'm just starting out and I am unaware of all the terminology. For instance, I didn't know that a mid-shaft electric motor was called a "P4 Hybrid". I know this now so I can look for those threads.


Only one? I found 24 pages in a search:









Trailer full of batteries?


I'am new to this forum, and to ev's, and I probably have a dumb question. Would it be practical to pull your battery packs behind your ev on a utility trailer? I was thinking by using two trailers (one being on charge while the other is in use) you could use one trailer for day driving and the...




www.diyelectriccar.com













Re: [EVDL] Range Extending Trailers


Re: [EVDL] Range Extending Trailers Hi Dennis, (Subject changed to reflect the content) I've been seriously thinking about the hybrid idea. There's a guy up in San Jose that had (had?) a Porsche 944 that had a range-extender trailer. I didn't look too hard at the idea then, but now that I...




www.diyelectriccar.com













Electric pusher trailer


Greetings: I'm think of doing a pusher trailer for my first project. I have a 1967 Ford truck that weighs around 4000lbs that it would push. I have $4000 to do the project and I already have the trailer. So, I would need all the electrical stuff plus a drive axle (thinking of a 9in ford)...




www.diyelectriccar.com













Car trailer which pushes the car.


I want a car trailer as small as possible but which to be equipped with an electric motor and to push the car.




www.diyelectriccar.com


----------



## brian_ (Feb 7, 2017)

kennybobby said:


> From the article:
> "The most critical part of the eTrailer design is the electronic sensor and control system that keeps the trailer operating at the same speed as the tow vehicle, cutting the tow load without negatively affecting the safety, ride or handling."


Of course the trailer operates at the same speed as the tow vehicle - they're attached. What they meant (or would have meant if they knew what they were talking about) is that the system needs to provide the trailer's share of the required driving force, keeping the pulling force of the tow vehicle on the trailer minimal (but still positive, for stability).

That's from the second NewAtlas article. NewAtlas material is entirely taken from other sources, usually amateurishly paraphrased, and is notorious for technical questionable content; however, in this case the stupidity originates in the Thor press release.


----------



## brian_ (Feb 7, 2017)

kennybobby said:


> From the picture it shows the motor inboard of the wheel and brake, clever design.


This setup in the E.Home Coco is nicely packaged, although unfortunately it has high unsprung mass due to the positions of the motors (much of the way out to the hubs on the trailing arms). The E.Home Caravan chassis in the CleanTechnica article shows a more conventional inboard drive unit with only half of the axle shafts as unsprung mass; this was probably an earlier design using available components.

Whatever the location, a powered trailer should have separate motors for left and right sides so that the trailer can be maneuvered at walking speed into or out of a parking spot without a tow vehicle attached, steering by differential wheel speed.


----------



## Korishan (8 mo ago)

brian_ said:


> the system needs to provide the trailer's share of the required driving force, keeping the pulling force of the tow vehicle on the trailer minimal (but still positive, for stability).


Exactly! Definitely what I was thinking in the designing. I was kinda thinking <50% power. Effectively making my 3500-4000lb trailer about 2000lbs being pulled. At least to start off with and see how things ride.



brian_ said:


> a powered trailer should have separate motors for left and right sides so that the trailer can be maneuvered at walking speed into or out of a parking spot without a tow vehicle attached, steering by differential wheel speed.


I really liked this idea from the German built trailer. Being able to move the trailer w/o needing to be hooked up to the truck. Would make moving it to a parking space and hooking up a lot easier of a task, for sure.


----------



## remy_martian (Feb 4, 2019)

Just remember that Brian is a flatlander 😂 and things will get really interesting in a hurry with that 50% push going down an 8% grade...


----------



## Electric Land Cruiser (Dec 30, 2020)

Using a typical trailer brake controller's output to control the trailer's regen braking should be trivial in a project like this.

Getting the trailer to harmoniously follow a car and accelerate, deceleration in unison without pushing or pulling or doing anything dangerous is just a matter of tuning the PID loop of your trailer controller. I would think it could work the same as those self-propelled vacuum cleaners that can reverse direction and follow your hand movements effortlessly.

Nothing off the shelf. All DIY. Lots of people come to this forum looking for a shopping list of things to buy and bolt on, but the reality is you have to design, test, and build your own.

A few years back I built a system of someone else's design that uses a Roboteq controller to move a motor back and forth along a track to passively follow another object below it using a potentiometer on a string. It worked really well.


----------



## Korishan (8 mo ago)

Electric Land Cruiser said:


> Using a typical trailer brake controller's output to control the trailer's regen braking should be trivial in a project like this.
> 
> Getting the trailer to harmoniously follow a car and accelerate, deceleration in unison without pushing or pulling or doing anything dangerous is just a matter of tuning the PID loop of your trailer controller. I would think it could work the same as those self-propelled vacuum cleaners that can reverse direction and follow your hand movements effortlessly.
> 
> Nothing off the shelf. All DIY. Lots of people come to this forum looking for a shopping list of things to buy and bolt on, but the reality is you have to design, test, and build your own.


Yeah, not looking for the off the shelf bolt on. I already tried looking for some of that availability and that's how I found the German/Aussie sites. I didn't see anything really locally for this project. Still looking up information about the items needed.

I was thinking along the same lines with the regen braking. More current being ran to the back causes the regen to engage more. Pretty proportional from there.

Just going electric assist on the trailer only (and not including the hybrid addon in my other thread) would drastically increase the amount of fuel saved. I was looking at both options to see which one would probably be more economical and logical. I think this system with the trailer would be the best overall.


----------



## remy_martian (Feb 4, 2019)

Licensing your contraption for road use will be interesting as it'll no longer be a trailer, but a motor vehicle...


----------



## Korishan (8 mo ago)

remy_martian said:


> Licensing your contraption for road use will be interesting as it'll no longer be a trailer, but a motor vehicle...


It'll be interesting, indeed. Will see what happens when that comes to pass.

Considering the amount of "crap" that is on the road now, might not be an issue, tbh. We have idiots here that drive with trucks having the front bumper 4ft in the air, rear bumper barely 2ft off the ground, and police do nothing to them. And that's definitely illegal considering they can't see in front of their trucks.


----------



## OR-Carl (Oct 6, 2018)

Korishan said:


> Just going electric assist on the trailer only (and not including the hybrid addon in my other thread) would drastically increase the amount of fuel saved. I was looking at both options to see which one would probably be more economical and logical.


If you want economical and logical, then reduce the trailer weight from 4000lbs to 2000lbs. Or better yet, take the Prius, and bring a tent !

How drastic exactly do you think the fuel savings are going to be? Pulling any trailer is going to incur extra aero drag, so your actual mileage improvement will depend on speed. As an exercise, run through the numbers: how many miles are you going to pull this thing, how much MPG improvement will that cause, and how long is it going to take to pay back the ten or twenty thousand it will take to build?

Here is a good calculator:


https://www.carmax.com/research/mpg-calculator


At 5$ per gallon, driving 10,000 miles and going from 15mpg to 18mpg will save you $556! I suggest finding another justification beyond the merely pecuniary, as these projects rarely if ever save money.

I also live in a hilly place, and have had a vehicle pushed around by a trailer. Going down a slope with a turn and then loosing traction on the tow vehicle is scary as shit without the trailer trying to keep on going. I am sure that the controls to make this safe are not rocket science, but it is also not something to trifle with.


----------



## floydr (Jun 21, 2021)

I believe that Korishan drives his truck and trailer for work.
Later floyd


----------



## OR-Carl (Oct 6, 2018)

Yeah, just saw the whole other thread with better numbers to use as examples, etc. Seems like it has already been done to death over there: Hybrid systems will not save money. Moving the hybrid system to the trailer will not only not save money, it will also be adding extra danger.


----------



## brian_ (Feb 7, 2017)

Korishan said:


> Exactly! Definitely what I was thinking in the designing. I was kinda thinking <50% power. Effectively making my 3500-4000lb trailer about 2000lbs being pulled. At least to start off with and see how things ride.


 Of course the trailer will be power-limited under some circumstances; for instance, when you climb a 6% grade (typical of our mountain passes) at highway speed (anything under 80 km/h or 50 mph is stuck in the slow lane with the tractor-trailer rigs) even 50% of the power needed would be more than you're likely to make available in the trailer, so it will just do what it can. Under braking I would want to go for as high a fraction of the appropriate retarding force as possible, coordinated with the trailer brakes to make up the right total.

Control design would be an interesting. The articles don't mention what sensors would be used.

The most obvious (and least likely) is a force transducer in the towing coupling, so the trailer motor(s) can provide whatever power is needed to keep the pulling force low (and provide regenerative braking to keep pushing of the tow vehicle low); this is similar to "surge" or "over-run" braking used in some trailers.
Acceleration could easily be used (as it is for electric trailer brakes, as Electric Land Cruiser suggested), since acceleration and the (known) trailer mass implies the required force (for speeding up, braking, climbing grades, and containing speed descending grades), but that ignores aero and rolling drag so it wouldn't do anything at steady speed. Acceleration-based trailer braking normally acts only when the tow vehicle brake pedal is pushed, but in this application regenerative braking should be enabled without tow vehicle braking to control speed and recovery energy at steady speed on grade descents.
Drag could be estimated from speed and appropriate power applied.
If dependence on a specific tow vehicle is acceptable, tow vehicle power and braking could be monitored, and trailer power proportional to that could be used.
Obviously no even moderately intelligent design would apply power when the tow vehicle is trying to brake; any reasonable design would assist the trailer's brakes both for better braking performance and for regenerative energy recovery.


----------



## brian_ (Feb 7, 2017)

Korishan said:


> I really liked this idea from the German built trailer. Being able to move the trailer w/o needing to be hooked up to the truck. Would make moving it to a parking space and hooking up a lot easier of a task, for sure.


It's just a bonus, rather than a likely reason to build a powered trailer, but it's a useful enough idea that in Europe there are many "caravan mover" systems available. They usually press a powered roller against the tire tread (of one tire on each side of the trailer), and are only usable at very low speed. I have only seen one North American supplier: purpleline 

There are also powered dollies that move a trailer by the tongue, but they are limited by traction with a very small fraction of the trailer weight on them, and they're inconvenient to take on a trip (they're normally left at the storage location, so they are not available to help at a campsite).


----------



## remy_martian (Feb 4, 2019)

As @OR-Carl said, there's nothing more scary, than a trailer pushing you on a curve...even in good traction. Even with 4 wheel stabilized steering.


----------



## brian_ (Feb 7, 2017)

Just a reminder - with even a kindergarten level of competence, the powered trailer would never under any circumstances use power to push on the tow vehicle, using any of the control methods (any trailer pushes on the tow vehicle to some extent under braking). 

Pusher trailers have been built (typically to make a bad gas-electric hybrid out of an EV and some terrible engine-driven setup on a trailer), but they're a horrible idea, and they're not what this discussion is about.


----------



## OR-Carl (Oct 6, 2018)

Haha, yeah, it sounds like a pretty complicated and scary way to spend money to me, but to each their own! 😀


----------



## Korishan (8 mo ago)

brian_ said:


> Pusher trailers ... not what this discussion is about.


Exactly! I don't want a pusher trailer. Never mentioned that was what I wanted to build. It was an electric "assist" trailer, effectively reducing the towing weight on the pulling vehicle.

As far as the controller goes, start off the basic sensors/switches would be, only apply axle power when the towing vehicle throttle is greater than X% and engine load is higher than Y%. There could probably be another sensor that detects that angle so that if the angle is <180* (basically it's starting to go down a hill), then power is cut is reduced. The more the angle, the more power reduction.
If the tower is in reverse, then no extra power is applied (unless used in emergency conditions where it is manually engaged, for example helping to assist getting unstuck out of a mud hole)
If the tower is applying brakes, then using the brake controllers sensors to know how much to regen braking to apply. This could be sensed by basically detecting the current flow and adjusting based on that. I have a Tekonsha controller that shows the current being applied. Obviously this would only work on inertia controllers, not the time based ones.

At this point in the venture, this project is just theoretical. Weighing out he pros/cons of such a system, what would be needed to build such a system. How much benefit it could give if done right.

Considering there are other countries that have such a system in place built "from the factory" tells me that it is a possible and viable option. It's just that the US is slow to incorporate such a system. Which doesn't surprise me the least, considering there are a lot of idiot drivers in the US.


----------



## brian_ (Feb 7, 2017)

Korishan said:


> Considering there are other countries that have such a system in place built "from the factory" tells me that it is a possible and viable option. It's just that the US is slow to incorporate such a system. Which doesn't surprise me the least, considering there are a lot of idiot drivers in the US.


I believe that the display units in Europe are just proposals, not production items. Still, if it makes it to production it will be in Europe first.

Although I won't challenge the allegation about drivers, the real difference between the western European and North American markets is cost - trailers here are generally considered to be minimum-cost things. People here who spend thousands of dollars for wheel and tire upgrades on their SUV or pickup truck are not willing to spend anything for better trailer running gear, leading to the ridiculous combination of enormous high-performance tires on alloy wheels with huge disk brakes on the tow vehicle, and tiny tires of 50-year-old design on steel wheels and crude suspension and drum brakes on the trailer... even though the trailer axles carry more load and of course are going at the same speed on the same road as the tow vehicle.


----------



## remy_martian (Feb 4, 2019)

Most tiny-weens don't upgrade the brakes with their 38 inch tires, so you get the ridiculous, unstoppable, combo of what looks like a ten inch diameter rotor sitting inside a $2,000 wheel and tire. It's the look that matters, damn the sheet metal rub and only being able to drive in a straight line with the stopping distance (and acceleration, because the gears are usually not changed in the diff either...just add a "chip" to the engine) of a freight train. Now - attach a trailer to that abomination.


----------



## Korishan (8 mo ago)

Well, no worries on this build. I have stock rims/tires. I'm not into that jack the truck up you need a ladder to get in or make the headlights become airplane landing lights. Makes the truck useless.


----------



## remy_martian (Feb 4, 2019)

There won't be a build. What you're dreaming of requires a fairly large engineering and qualification team. But, it's ok to do neuron curls.


----------



## Spyderrock (Oct 26, 2018)

Korishan said:


> It'll be interesting, indeed. Will see what happens when that comes to pass.
> 
> Considering the amount of "crap" that is on the road now, might not be an issue, tbh. We have idiots here that drive with trucks having the front bumper 4ft in the air, rear bumper barely 2ft off the ground, and police do nothing to them. And that's definitely illegal considering they can't see in front of their trucks.


So you're planning on putting this contraption on the road with no licensing or permits? I hope they have nice prisons where you are because that's likely where you'll be heading when things go wrong and you kill or severely harm someone(s). 
We have traffic laws and prisons for a reason. Let's see where the 4 foot high bumper guy lands when his bumper decapitates someone.
Here in Colorado we also have people that put all sorts of crap on the road. Enforcement is also lax. That is until something happens. That's when courts, lawyers($$$$), losing your license and prisons enter in. And do you think you're insurance company going to cover you in a contraption like that? Go ahead ruin your life if you like. But please consider the rest if us on the road.


----------



## remy_martian (Feb 4, 2019)

I feel the same way about this millennial driverless cars nonesense.


----------



## brian_ (Feb 7, 2017)

Spyderrock said:


> So you're planning on putting this contraption on the road with no licensing or permits? I hope they have nice prisons where you are because that's likely where you'll be heading...


Exactly the same thing could be said about most DIY electric car conversions, so you might want to watch what you wish for.


----------



## remy_martian (Feb 4, 2019)

I guess you've never had the excitement of a trailer unhitching on the highway (twice) and whipping and busting safety chains (that one time I wasn't driving).

Crossed over the median, across two oncoming lanes, stopped by the highway fence. Luckily nobody in those oncoming lanes.

Now, imagine it with 200HP gone wild.

An EV poses nowhere near the threat to anyone on the road. Nothing even close to a rogue trailer. On top of that, a rogue powered trailer.

But, fortunately, it's a complicated paper tiger that will never see the light of day.

That said, some of the stuff I've seen here being done with steering shafts and brake masters is really scary stuff....but the same kind of people would likely pull the same stunts putting in a big block ICE, so it's not EV per se.

It's all fun and games until the lawyers are arguing.


----------



## electro wrks (Mar 5, 2012)

brian_ said:


> Just a reminder - with even a kindergarten level of competence, the powered trailer would never under any circumstances use power to push on the tow vehicle, using any of the control methods (any trailer pushes on the tow vehicle to some extent under braking).
> 
> Pusher trailers have been built (typically to make a bad gas-electric hybrid out of an EV and some terrible engine-driven setup on a trailer), but they're a horrible idea, and they're not what this discussion is about.


I've seen this done. And, it does seem to work better than what the uninformed and unimaginative mind might believe. Is it practical? It will be interesting to see what people come up with.


----------



## remy_martian (Feb 4, 2019)

Show your work. 

"I've seen this done" doesn't provide any useful information to the forum and is a statement of no use other than comparing pee pees.

You've seen it done 🤦‍♂️ 

Let's see it.


----------



## Korishan (8 mo ago)

Wow, I come here asking for help, ideas, suggestions, etc. Instead, all i see is bashing, slamming, short of name calling, and being demeaning. Only 2 ppl have actually provided some helpful information pertaining to what this thread was posted for. Brian_ posted useful and positive information and backed up that information with valid data. With that information I made a course correction.

As far as a rogue trailer on the loose!?! What?! How in the world could that happen if the trailer is disconnected from truck and controller is disconnected?? It would act just like any other trailer that's been disconnected with the emergency braking system engaging locking up the wheels. And yes, I have had a trailer come loose from my truck. It was a rental and the locking mechanism failed and the tongue bounced off the ball. Fortunately I was only doing about 30mph when it happened, but still scary enough when your backend starts getting tugged back and forth.

If I would of known the majority of the replies were going to be haters how just want to see other people fail, I would of never posted. Grow up people and be adults.

I am completely open to thoughtful and meaningful replies. Ones that have examples, explanations, suggestions, or data for the reason for or against my proposed idea. Just replying with crap replies and bashing is not help anyone. No me, not anyone else in the future who has the same idea. The majority of the replies in this thread have become trash and will not really help any newbies come to a better understanding of why or why not it is a good idea or a bad idea.


----------



## remy_martian (Feb 4, 2019)

Go for it. The hurdles are huge. Be the lone wolf that shows 'em....instead of an engineering team, you'll pul it off yourself. Great.

So when will we see it working?


----------



## remy_martian (Feb 4, 2019)

How can it happen? You tell us how it can vs cannot. It's not all happy happy when it comes to mapping out holes in any engineering effort. How will it fail vs "it can't".

Trailers are connected by an umbilical. Snap the hitch ball off and it's still connected electrically. Sensor says trailer weight is too light when it comes off the ball on a curve...brakes are biased accordingly, but with no reaction force provided by the ball, trailer tongue becomes a 200HP scythe. Then your controller and truck get disconnected.

You have to think of how it will fail. Not how it won't.


----------



## MattsAwesomeStuff (Aug 10, 2017)

Korishan said:


> Instead, all i see is bashing, slamming, short of name calling, and being demeaning.


Ehn, very little of that. Most of what I've seen here is skepticism and warnings.

If many people are skeptical and giving you warnings, perhaps you should take that to mean "This is not a great idea, and if I'm going to move forward, I have to solve this stuff."

Your project, like most DIY EVs, like most car projects, is a bad idea. You want to save money, but probably won't. You came in with some gross 10:1 misunderstandings of cost, and correcting for those hasn't changed your mind. You're generally failing to make a convincing argument that this is a worthwhile, cost effective project.

That said, the biggest reason to undertake any car project is "Because I want to." And that's really all the justification you need. If it's fun and interesting, then go nuts.

Yeah, you probably couldn't sell this project, it's not nearly safe enough to trust in the hands of a random consumer. But, odds of both hitch failure, and chain failure, and then some runaway EV situation is... nearly zero. Have a deadman's tether on the cable and who cares.

If you want to just because you want to, then go ahead. I doubt 10% of car projects of any kind ever get finished, and yet, we all endure. So, go for it if you want to. Just don't expect much in the end. And document it along the way so that, good or bad, other get to learn from it.


----------



## Korishan (8 mo ago)

There is a big difference between "skepticism" and bashing. I understand quite well that I am not an engineer. I also understand that my viewpoint could be misaligned. As I stated earlier, only 1 person actually took the time to explain some of the technical issues with logical reasoning. Pretty much everyone else has been calling foul saying it's illegal, or you'll kill someone, or stop measuring pee pees, or you're going to go jail, etc, etc. Yes, this is considered bashing as it does zero to add to the constructive nature of the information.

How does any of that help anyone?

I am not designing this project as a money maker to sell to others. This project is for "me". No one else. This is not a project that hasn't been done before, because it has been done, in other countries, by companies. It's even being adopted here for big rigs. So it's not something that is dangerous and going to kill people.

And Remy, I've already mentioned how to keep it from doing damage. Trailers already are designed with a dead man switch. My trailer has one. Has onboard battery and a trigger relay to lock up the wheels if it comes disconnected from the vehicle. Safety features were never going to be not worked out or thought out.
To address the 'trailer weight sensor', that is not something that'd be a physical weight gauge coupled between the ball and tongue. I already mentioned that it would be based off the engine load and throttle position. If there are sensors that would need to be incorporated, then great. I'm not opposed to that. But putting one on the ball and tongue is not feasible, or even safe. I already reconned that quite some time ago for the reasons you mentioned. And where did you get 200HP from?? Is this some guess as to how much power is needed to move the trailer? Or some random you number you just guessed at?

All Remy has provided was nay saying results and any of the links they did post had nothing to do with this project. From the first post onward has been insulting and downgrading. Not very helpful.

And just like there are plenty of EV swap kits available to convert an ICE vehicle to an EV, "this" is the kind of thing I was looking for. Not necessarily that I would 100% build everything myself. If there's a kit available, or even one that could be modified, that'd be fine. This whole territory is new to me. Otherwise I would never have posted a thread here as I wouldn't need to get some outside help or recommendations.

Not a very good welcome for a newbie to the forum, that's for sure. First posting and I get roasted because I don't know the topic and I'm asking for help. Way to go.


----------



## remy_martian (Feb 4, 2019)

"At this point in the *venture*, this project is *just theoretical*. Weighing out [t]he *pros/cons* of such a system, what would be needed to build such a system."

You've clearly only wanted to hear the pros with what you just posted. That's not weighing anything. That's no design review (I've worked in places where engineers came out of design reviews crying). It's merely the analog of one fat snowflake kid on a teeter-totter.

Yes, I think a 6000 lb trailer would need around 200hp, which I think is a better guess than your number. Yes, it'll need around 100HP just to hold speed down a hill, let alone slow for a curve. Yeah, it's a guess - I'm not going to spend a hundred hours of unpaid engineering time on "just theoretical". Even if I did, this design would then require PE approval - I seriously doubt you'd find a PE that would sign it off so you can apply to DMV for a road permit. You didn't even look into the regulatory restrictions in your state before going any further.

If you're looking for a spoonfeeding or being tutored here, I have yet to see a project or member here that got it. Everyone is expected to do their own heavy lifting. Even the young lady converting her grampa's T4.

That said, as an EE, I'm looking forward to seeing you pull this off. The circuit board design with multiple redundancy and fully failsafe hardware software and communications, the realtime control algorithms and RTOS, the tens of thousands of lines of software, the 100's of MHz failsafe processors designs, EMC EMI and EMS testing (a CB radio can make it go nuts, for example), the patent applications to protect that huge R&D spend, the documentation and testing protocols that gets approval from a PE and from state and federal authorities to operate such a contraption on an American road. It would need around $50M in VC seed money by Silicon Valley comps. This is not a Youtube Arduino project, nor is it a simple mod of a trailer brake controller.

Cuz, "all ya gotta do is..."

Go for it. Good luck. You have Brian as your buddy and he's one of the sharp ones here.


----------



## Korishan (8 mo ago)

remy_martian said:


> You've clearly only wanted to hear the pros with what you just posted. That's not weighing anything.


Negative ghost rider. I have heard the negatives. But there's a difference between slamming someone for their ideas, and helping them understand why it may be a bad idea.



remy_martian said:


> it'll need around 100HP just to hold speed down a hill


Why would there be _any_ power while going down hill?!?! That is definitely a stupid option, imho. Going down hill is either coasting or regen braking (if that system was implemented, in _any_ design, not just this current idea)



remy_martian said:


> If you're looking for a spoonfeeding or being tutored here


I'm not asking to be spoonfed. Never once asked for that, or even remotely. I asked for ideas and suggestions and possibly because this is a new area of work for me (this particular type of application) if certain key words for searching would be beneficial. Such as: "Might want to check out Such-n-such's builds" or "You'll want to look up what is called a such-n-such"



remy_martian said:


> I have yet to see a project or member here that got it


No one!?!? Not 1 single person!?!? I find that hard believe. Unless you yourself have only been sitting on the forum posting bashing comments without actually reading and participating. I'm sure there are some people on this forum who have actually started, processed, and completed DIY builds. Probably even well over 100, considering this size of users on this forum. Why are you such a hater?



remy_martian said:


> That said, as an EE, I'm looking forward to seeing you pull this off.


Oh goodie! An EE, who doesn't show anything for their work, except to downgrade others for not being as knowledgeable as they are! Now I see what your true colors are. Appreciate it.

It would be a whole lot more productive and informative to go with something like: "Hey, the reasons this is a bad idea is because....." and then list the reasons why it's bad idea. Instead, you just continually take the proverbial bat to the back of my head, like that's going to actually teach me anything. As Brian stated some logical reasons why it was a bad idea to use hub motors. I appreciate that (and no, not in this thread, but in some of his others, as, you know, I do read other posts from members. Especially those that are _actually_ helpful).

I'm just a new comer to this forum, so I don't expect my viewpoint to change yours at all. I don't expect it. In fact, I expect the opposite. You'll continue to be the arrogant person that you are. I can't stand people like that. You have a degree/education in a field, and you feel that entitles you to thrash it around and feel superior to others, because they don't know as much as you do, and you feel that they don't deserve to know your knowledge. So you just reply with "It won't work. Don't do it. Give up. That's a stupid idea. You're going to get someone killed."

I also expect that you'll keep on replying with more antics after this one. Doesn't phase me one bit. Go right ahead.


----------



## OR-Carl (Oct 6, 2018)

Korishan said:


> "Hey, the reasons this is a bad idea is because....."


The main reason this plan is a bad idea is that the stated goal was to save money, and there is no way that it is going to. 

If the new goal is to burn a pile of money and get an interesting one-of-a-kind trailer, then the reason THAT plan is bad is that doing so safely is going to likely be beyond your current abilities. If you are really dedicated to this plan, you could probably learn all the skills, do several test-projects, and eventually nail it. Do you have a decade and a hundred grand to fritter away? You are blazing new trail here; people are not holding back the "Might want to check out Such-n-such's builds" or "You'll want to look up what is called a such-n-such" Those things simply do not exist. 

Anyway, the reason people are razzing you is because you are letting them. If you show up asking simple questions, some people will give you advice, others will tease you. Welcome to the internet. If you start getting all defensive and demanding better advice from them, they are going to just tease you more. Its sort of a catch-22, because the fact that you are asking for advice means you dont know much, and the fact that you are dismissing the advice means that you dont even know what you dont know. So do some reading. A project like this will likely need 50 to 100 hours of reading just to get you up to speed on the basics. That should reveal to you what questions you need to be asking, and hopefully will also lead you over to DIYelectricTrailers or wherever all those secret trailer projets are being discussed. I still think you are going to be breaking new ground, but I have never really looked. You are going to have to learn to teach yourself a lot of new skills, the "help" you have gotten so far is pretty much what you should expect from asking for help on an online forum. Anyway, good luck, youre going to need it.


----------



## remy_martian (Feb 4, 2019)

Show anything for my "Work"? I consult at $650 an hour. For this, need a $100,000 retainer plus equity in the venture plus a full dive in showing how you will raise the $50M in seed money that's needed to hire the team and pay for development. I like the idea, but ideas are a dime a dozen and you are way out of your wheelhouse in pulling this off. That's all assuming you want advice worth more than you're paying for it now, cuz I'm here for fun and to help the humble and willing, not to work, and would be someone to run it that knows what they're doing.

That said, I'm booked for three years, so you'll have to wait if we agree to move forward. I don't enrich B Ark people for slave wages anymore by doing their strategic/business plans...retired from that a decade ago. I expect battery densities to improve over the next 3-5 years, so an electric plane conversion will likely mean I'm completely booked.

And, yes my dear...regen requires absorbing motor horsepower.


----------



## brian_ (Feb 7, 2017)

Korishan said:


> Why would there be _any_ power while going down hill?!?! That is definitely a stupid option, imho. Going down hill is either coasting or regen braking (if that system was implemented, in _any_ design, not just this current idea)


That power would be for regenerative braking for grade descent control. I wouldn't build an electric power-assist trailer without including that, because it would be valuable (both for energy recovery and for more effective and stable descent control than depending on tow vehicle engine braking), but it wouldn't be necessary to handle the maximum power possible.

For an example, a 2000 kg trailer descending a 6% grade would need 
6% * 2000 kg * ~10 m/s2 * = 1200 N
of retarding force. Rolling and aero drag provides most of that.
At 100 km/h (28 m/s) that's about 34 kW... so much less than that to contain speed given rolling and aero drag.

You can do all of this in "US Customary Units" if you want to make it harder - the result is the same (less than 46 hp).

I think a reasonable approach might be to size for maximum usable regen power in likely scenarios (keeping in mind that speed would probably be lower on steeper grade), and accept that power limit for acceleration and grade climbing. The motors shown in the RV manufacturer's proposals are roughly compatible with this sizing.


----------



## Korishan (8 mo ago)

brian_ said:


> You can do all of this in "US Customary Units" if you want to make it harder


haha Yeah, I was already going to do the conversion afterwards. I really wish the US would get rid of Imperial and go back to Metric. Would make things soooo much easier in many fields.



brian_ said:


> That power would be for regenerative braking for grade descent control


Ok, yeah, that makes sense. When I was stating "Why would there be any power while going down hill?", I was referring to additive/assistive power, not in the regen braking aspect. I completely agree with that sentiment. This is true as when going down a hill, the e-brake controller applies more power to the brakes if you press the pedal than if it was level terrain. So this makes good sense to do



brian_ said:


> I think a reasonable approach might be to size for maximum usable regen power in likely scenarios (keeping in mind that speed would probably be lower on steeper grade), and accept that power limit for acceleration and grade climbing. The motors shown in the RV manufacturer's proposals are roughly compatible with this sizing.


Most of my travels are relatively flat or with low grades. I think there's only a few hills that are about 6*. Two bridges _might_ be, but not sure. They are pretty steep. The truck will downshift a gear even without a load (I know this isn't much of a baseline, but on most hills the Hemi with the 8-speed tranny barely downshifts when driving without a load. I primarily drive with cruise control with unhitched so it's pretty consistent when and where it would do so)


----------



## 94Tracker (Jan 17, 2011)

Korishan said:


> And Remy, I've already mentioned how to keep it from doing damage. Trailers already are designed with a dead man switch. My trailer has one. Has onboard battery and a trigger relay to lock up the wheels if it comes disconnected from the vehicle. Safety features were never going to be not worked out or thought out.


Just for clarification the "deadman" breakaway switch only activates after the chains have broken. It is a simple switch that when activated applies full power directly to the brakes. No relays or fuses involved. RV trailers running 12v indoors and any other trailer with 12v power when not connected to tow vehicle use the rv or deep cycle battery to power them.
However any other trailer (enclosed cargo car hauler etc) uses a small dry lead acid battery. These just sit there until until they are dead as they do not connect to the charging system. So check the voltage on these and replace when below 12.5 volts.

As to the build, Ebikes can use torque sensing to determine how much power to apply. From my readings about the trailer versions it I think the wheels apply some power if they sense rotation to the point of counteracting the wind and weight drag. Coasting cuts the power and brake application creates regen. Unfortunately I don't remember where I read this. 
The trailer's hubs would have to have rotation sensors (abs sensors). This is a very complex build. The simplest way likely is adapting an existing hybrid drivetrain, but there probably isn't enough load capacity that way. Toyota Rav4 and Highlander use electric rear axles to assist the front wheel drive and make them all wheel drive.


----------



## brian_ (Feb 7, 2017)

94Tracker said:


> Just for clarification the "deadman" breakaway switch only activates after the chains have broken. It is a simple switch that when activated applies full power directly to the brakes. No relays or fuses involved.


The ideal is to trip the breakaway switch when the electrical cable between tow vehicle and trailer disconnects, but the requirement is to trip when the trailer is physically disconnected from the tow vehicle, and if the safety chains have broke the breakaway switch will have tripped.

There is an equivalent in air brakes used on trucks: there is a service brake air line (air pressure is supplied to apply the brakes), but there is also a parking/emergency brake air line which provides air pressure to keep a spring from applying the brakes, so if the parking/emergency line stops supplying air pressure (due to disconnection when unhitched, or disconnection if the trailer separates in travel, or if the driver hits the parking/emergency brake control) the springs apply the trailer's brakes. Thinking through the possible scenarios is just part of good design, whether the system is braking or driving.



94Tracker said:


> RV trailers running 12v indoors and any other trailer with 12v power when not connected to tow vehicle use the rv or deep cycle battery to power them.
> However any other trailer (enclosed cargo car hauler etc) uses a small dry lead acid battery. These just sit there until until they are dead as they do not connect to the charging system. So check the voltage on these and replace when below 12.5 volts.


While this is generally true, breakaway battery chargers are routinely available to keep the breakaway battery charged in a trailer which does not have other uses for the onboard battery. This illustrates that there are levels of sophistication even in common trailer systems; a relatively high level of sophistication would be appropriate for a trailer with drive assistance.


----------



## remy_martian (Feb 4, 2019)

Reluctor-wheel ABS sensors don't have the resolution needed for this application.

And, yes, loss of traction on one wheel of the trailer or tow vehicle has to be sensed and compensated.


----------



## brian_ (Feb 7, 2017)

94Tracker said:


> The simplest way likely is adapting an existing hybrid drivetrain, but there probably isn't enough load capacity that way. Toyota Rav4 and Highlander use electric rear axles to assist the front wheel drive and make them all wheel drive.


Yes - while they're not the only examples of an electric-only drive axle in a hybrid vehicle, they're the most common. They have enough power capability for the mild boost desired here (at least in the most powerful version found in the Highlander Hybrid), but they're not used continuously and don't have enough cooling capacity to do that. They would work for regenerative braking and brief acceleration and grade-climbing boosts.


----------



## brian_ (Feb 7, 2017)

94Tracker said:


> As to the build, Ebikes can use torque sensing to determine how much power to apply. From my readings about the trailer versions it I think the wheels apply some power if they sense rotation to the point of counteracting the wind and weight drag.


Torque sensing makes sense for an electrically assisted bike because what is being sensed is pedaling effort; the trailer equivalent would be communicating with the tow vehicle powertrain, but directly sensing pulling force between the hitch and trailer tongue would be more straightforward and not dependent on the tow vehicle. As mentioned earlier, surge or overrun braking systems do this mechanically for braking control.

The aero and rolling drag can be estimated based on just speed. With wind speed and direction changes it will be a rough approximation, but that might be a good enough for a mild assist.


----------

