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10-21-2022, 05:19 PM
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#81
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Rivet Master 
1988 32' Excella
Robbinsville
, New Jersey
Join Date: May 2012
Posts: 3,164
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Quote:
Originally Posted by hairyclive
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Towing a vehicle with 4 wheels near the corners and well under 5% tongue weight and the front tires passively steering is already very popular and done at speeds over 70mph. Just check in with the motor home folks that have toads.
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10-21-2022, 06:08 PM
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#82
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Site Team
1994 25' Excella
Waukesha
, Wisconsin
Join Date: Sep 2020
Posts: 5,576
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Quote:
Originally Posted by Wazbro
Towing a vehicle with 4 wheels near the corners and well under 5% tongue weight and the front tires passively steering is already very popular and done at speeds over 70mph. Just check in with the motor home folks that have toads.
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Have you ever tried to back up a trailer configured like that? I did it on the farm pulling hay wagons. Not for the feint of heart.
I strongly suspect that travel trailers will largely keep their current form factor for the most part, even with the transition to E-trailers.
And yes, the e-trailers can self park but it will still be quite common to have need to back up the combination rig while hitched up.
__________________
Richard
11018
1994 Excella 25 Follow the build on Gertie!
1999 Suburban LS 2500 w/7.4L V8
1974 GMC 4108a - Custom Coach Land Cruiser (Sold)
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10-21-2022, 06:39 PM
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#83
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Rivet Master
Currently Looking...
Vancouver
, British Columbia
Join Date: Oct 2012
Posts: 4,592
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Quote:
Originally Posted by richard5933
Show us a model which shows that a trailer can be stable at 75-80mph on a downhill run with only 5% tongue weight.
On a 30-ft, nearly 10,000-lb trailer that would be only 500 lbs, and the length of the trailer is going to play into the equation as much as the weight and where it's placed. In order to have as much weight low and centered over the axles as you are talking about, the rest of the trailer would have to go on a serious diet.
Not saying that the batteries won't help stabilize things, but I don't see them as being the panacea you're describing where all previous models are suddenly thrown out the design room window.
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I think the hypothetical problem is probably worse than you describe. Recall that this is to deal with the situation where all the electronics have failed. You will have no trailer brakes, no stability control system, no abs, no power assist on the TV brakes, and if the shift to electronic steering continues, limited steering. You are probably going over 80 mph by this point, and your airbags are non functional as well.
Seriously, I don’t tow at 80 mph, and all these systems have redundancy. And I wouldn’t use the word panacea.
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10-21-2022, 06:51 PM
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#84
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Rivet Master
1988 32' Excella
Robbinsville
, New Jersey
Join Date: May 2012
Posts: 3,164
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Quote:
Originally Posted by richard5933
Have you ever tried to back up a trailer configured like that? I did it on the farm pulling hay wagons. Not for the feint of heart.
I strongly suspect that travel trailers will largely keep their current form factor for the most part, even with the transition to E-trailers.
And yes, the e-trailers can self park but it will still be quite common to have need to back up the combination rig while hitched up.
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I know it's quite difficult to backup, I was just commenting that hairyclive was talking about inventing tech that already exists and works with very low tongue weight. Obviously no tech is perfect.
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10-21-2022, 07:02 PM
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#85
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Site Team
1994 25' Excella
Waukesha
, Wisconsin
Join Date: Sep 2020
Posts: 5,576
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Quote:
Originally Posted by jcl
I think the hypothetical problem is probably worse than you describe. Recall that this is to deal with the situation where all the electronics have failed. You will have no trailer brakes, no stability control system, no abs, no power assist on the TV brakes, and if the shift to electronic steering continues, limited steering. You are probably going over 80 mph by this point, and your airbags are non functional as well.
Seriously, I don’t tow at 80 mph, and all these systems have redundancy. And I wouldn’t use the word panacea.
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All this hypothetical discussion is great, but I really believe that for the foreseeable future any EV tow vehicles are going to be towing traditional trailers 99.9% of the time. I don't believe there is even one EV-enabled trailer on the market yet.
This is why it seems that the initial discussion of how to property set the trailer's brake controller to maximize safety AND regen seems more relevant at this time, at least to me.
__________________
Richard
11018
1994 Excella 25 Follow the build on Gertie!
1999 Suburban LS 2500 w/7.4L V8
1974 GMC 4108a - Custom Coach Land Cruiser (Sold)
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10-21-2022, 07:14 PM
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#86
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Rivet Master
Currently Looking...
Vancouver
, British Columbia
Join Date: Oct 2012
Posts: 4,592
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Quote:
Originally Posted by hairyclive
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Yes, the e stream, or a similar development trailer, is the model I was thinking of.
While it would allow towing with lower TV hp, power isn’t the practical limit, it is range.
I agree with using a strain gauge in the coupler, for longitudinal sensing related to towing and braking. An electronic version of the classic mechanical trailer surge brake control. With these sensors, a smart interface between the TV and trailer would not be required. The hitch ball would be the interface, ensuring compatibility with a wide range of tow vehicles.
I wouldn’t use steering on the trailer axles. Just torque vectoring using variable power to each trailer wheel. Already commercially available.
I wouldn’t promote lateral sensing on the coupler. Sway could be easily managed with a stability control box using yaw sensors. Already commercially available. First response to sway events would be torque vectoring, in both drive and regen modes. Next step would be single wheel trailer braking.
Using wheel speed sensors on the trailer wheels would allow improved control in slippery road conditions and could be set up to always keep the combination in tension, preventing the trailer from pushing the tow vehicle.
All of the above has already been demonstrated. And the drive axle supplier, who also supplied all the controls, was ZF. It is their business.
With a battery matching the capacity of an Audi e-tron, they achieved a towing range greater than the published range of the Audi. And a low tongue weight, incidentally.
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10-21-2022, 07:21 PM
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#87
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Rivet Master
Currently Looking...
Vancouver
, British Columbia
Join Date: Oct 2012
Posts: 4,592
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Quote:
Originally Posted by richard5933
All this hypothetical discussion is great, but I really believe that for the foreseeable future any EV tow vehicles are going to be towing traditional trailers 99.9% of the time. I don't believe there is even one EV-enabled trailer on the market yet.
This is why it seems that the initial discussion of how to property set the trailer's brake controller to maximize safety AND regen seems more relevant at this time, at least to me.
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But wasn’t that answered by the OP back in post #6?
Without an integrated trailer brake controller, like in my vehicle, I would set the trailer brake gain the same way anyone with an exhaust brake and no integrated trailer brake controller does. Let the vehicle provide retarding force. Ensure the trailer brakes activate when stabbing the brake pedal. And I would use the onboard energy monitor screen on a descent, during setup, over repeated runs, to confirm the balance between trailer brakes and regen. Don’t compromise regen more than necessary, and ensure trailer brakes work on brake pedal application.
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10-21-2022, 07:33 PM
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#88
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3 Rivet Member 
Northern
, California
Join Date: Sep 2022
Posts: 215
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Here’s an idea - instead of a full eTrailer with a huge battery bank, instead do a hybrid, meaning something in-between a traditional freewheel trailer and a powered one. What you do is, instead of putting a 60kWh battery on there, just put on a regenerative breaking system as a upgrade to simple brakes, and hook it up to a small 6 kWh battery pack. Now this would need to be a HV pack (which may be difficult/impossible at that size - or would it? Maybe a LV pack would be fine), and for regen would need at least two motors. So easy - when a brake signal comes in, instead of braking the trailer does a heavy regen - if its a hard brake then it can switch to physical brakes just like EV’s do.
The only problem is what to do with that power? You could have a fantastic all electric trailer for one - electric heat, water and cooking. That’s the simplest solution, or you could have a hitch sensor like the eTrailer and do some powered assist. And to be really cool you could provide emergency EV charging as a backup. But ideally you’d want to start your trip with an empty battery. If you start out full then you get no benefit and the system has to use brakes. Additionally the motors will need to be cheaper induction motors (no rare earth magnets) which is a bonus. The reason is only these motors freewheel (the B field is created via power from the battery in coils, less efficient but perfect in this application).
I like this solution better - it’s backwards compatible, simple and should be relatively cheap, but best it’s economically the most feasible as it has a customer facing benefit of offering a practical fully electric solution. Because of this it has a chance as people would pay for that, and it works with ICE and you don’t have to worry about overheating your trailer brakes.
So with this we have three possibilities - full eTrailer, Hybrid, and the ‘can be done now with any trailer’ just using your brake controller, as described above and previously, which is to just set the brake gain to maximize vehicle regen (similiar to the setting you’d use with a Diesel exhaust braking)
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10-21-2022, 08:08 PM
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#89
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3 Rivet Member
Northern
, California
Join Date: Sep 2022
Posts: 215
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Answering my question about LV/HV - cells are generally 3-4 something volts in series. Ultium has a trick up its sleeve though, where it has two stacks of 12 modules (and modules are made of cells), each of which (the stacks) are the usual 400V architecture. But it has this crazy 800V 350kW charging, which is accomplished via a shunt/switch which takes those two parallel stacks and wires them in series (2x400V = 800V at half the kWh or capacity).
So likewise here, have a bunch of 12V modules wires up in series for some HV for regen. Then in camping mode a switches to parallel for 12VDC usage with a 120VAC DC-AC conversion, or depending on the details maybe a 124+VDC system with conversion to AC and 12 VDC.
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10-24-2022, 07:23 PM
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#90
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Rivet Master
2019 22' Sport
High River
, Alberta
Join Date: Aug 2006
Posts: 1,192
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Quote:
Originally Posted by richard5933
Show us a model which shows that a trailer can be stable at 75-80mph on a downhill run with only 5% tongue weight.
On a 30-ft, nearly 10,000-lb trailer that would be only 500 lbs, and the length of the trailer is going to play into the equation as much as the weight and where it's placed. In order to have as much weight low and centered over the axles as you are talking about, the rest of the trailer would have to go on a serious diet.
Not saying that the batteries won't help stabilize things, but I don't see them as being the panacea you're describing where all previous models are suddenly thrown out the design room window.
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What if the battery pack weighs a ton by itself and is integrated with the axle assembly?
There is nothing magic about 10% tongue weight. Tall trailers with slides and a high centre of gravity need 15% or more. From experience, I think Airstreams - at least older ones - do well at 11%. Boats are good down to 5 or 6%.
No, I don’t have a model and I’m not an engineer. But I’d guess that prototyping and testing are the way to determine these things.
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10-25-2022, 04:23 AM
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#91
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Site Team
1994 25' Excella
Waukesha
, Wisconsin
Join Date: Sep 2020
Posts: 5,576
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Quote:
Originally Posted by AlbertF
What if the battery pack weighs a ton by itself and is integrated with the axle assembly?
There is nothing magic about 10% tongue weight. Tall trailers with slides and a high centre of gravity need 15% or more. From experience, I think Airstreams - at least older ones - do well at 11%. Boats are good down to 5 or 6%.
No, I don’t have a model and I’m not an engineer. But I’d guess that prototyping and testing are the way to determine these things.
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Could be.
But a travel trailer has a much different weight distribution and wind catching ability than the average boat being pulled, which is likely behind the different tongue weights generally seen on each of them.
Even with 2,000 lbs sitting in the belly there will still be the big wind sail above it and all the other weight to be considered. For sure adding 2,000 lbs down and low will help stabilize the trailer, but as you said modeling and real-world testing are necessary before we'll know if this will make a big enough difference to make for safe towing at US highway speeds with only 5% on the tongue.
__________________
Richard
11018
1994 Excella 25 Follow the build on Gertie!
1999 Suburban LS 2500 w/7.4L V8
1974 GMC 4108a - Custom Coach Land Cruiser (Sold)
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10-25-2022, 07:39 AM
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#92
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2 Rivet Member 
2013 20' Flying Cloud
minneapolis
, Minnesota
Join Date: Aug 2016
Posts: 62
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Center of mass
There are still some basics missing here. Forget the TV. I already commented that the trailer needs to not be pushed from the front. Now just the trailer itself needs to be stable and yes, there is something critically important about tongue weight. First boats are WAY more aerodynamic and those forces on a trailer are very significant. Just consider a cyclist at 2.0 mph spends more than 1/2 their energy overcoming aerodynamic forces.
These forces can introduce instability, and under the right conditions, a harmonic resonance based on the natural frequencies of the trailer system. So you want a trailer that dampens these forces and is convergent.
Basically your trailer has only three points of load from the ground.. tires left and right and trailer hitch. The distribution of weight between all three determines the center of mass which determines how the trailer responds. When the center of mass is at the axel (like your battery example) there is no counter force to induced sway. You need mass forward of the wheels to create an opposing force to sway… simple as that.
Quote:
Originally Posted by AlbertF
What if the battery pack weighs a ton by itself and is integrated with the axle assembly?
There is nothing magic about 10% tongue weight. Tall trailers with slides and a high centre of gravity need 15% or more. From experience, I think Airstreams - at least older ones - do well at 11%. Boats are good down to 5 or 6%.
No, I don’t have a model and I’m not an engineer. But I’d guess that prototyping and testing are the way to determine these things.
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10-26-2022, 07:28 AM
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#93
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Rivet Master
2019 22' Sport
High River
, Alberta
Join Date: Aug 2006
Posts: 1,192
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Quote:
Originally Posted by cedonly
There are still some basics missing here. Forget the TV. I already commented that the trailer needs to not be pushed from the front. Now just the trailer itself needs to be stable and yes, there is something critically important about tongue weight. First boats are WAY more aerodynamic and those forces on a trailer are very significant. Just consider a cyclist at 2.0 mph spends more than 1/2 their energy overcoming aerodynamic forces.
These forces can introduce instability, and under the right conditions, a harmonic resonance based on the natural frequencies of the trailer system. So you want a trailer that dampens these forces and is convergent.
Basically your trailer has only three points of load from the ground.. tires left and right and trailer hitch. The distribution of weight between all three determines the center of mass which determines how the trailer responds. When the center of mass is at the axel (like your battery example) there is no counter force to induced sway. You need mass forward of the wheels to create an opposing force to sway… simple as that.
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Interesting, thanks for adding these comments.
This has me thinking that a lower tongue weight would also make a trailer more sensitive to loading at the rear, because the pendulum effect would be more pronounced. Rear bicycle racks might not be suitable for such trailers.
European caravans have low tongue weights, and the axle is typically centred under the body. I suspect if you looked at their layouts, refrigerators, tanks, and bathrooms are located very close to the axle, and not at the rear.
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10-27-2022, 09:26 AM
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#94
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3 Rivet Member
Currently Looking...
Niagara Falls
, Ontario
Join Date: Sep 2020
Posts: 174
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Quote:
Originally Posted by cedonly
There are still some basics missing here. Forget the TV. I already commented that the trailer needs to not be pushed from the front. Now just the trailer itself needs to be stable and yes, there is something critically important about tongue weight. First boats are WAY more aerodynamic and those forces on a trailer are very significant. Just consider a cyclist at 2.0 mph spends more than 1/2 their energy overcoming aerodynamic forces.
These forces can introduce instability, and under the right conditions, a harmonic resonance based on the natural frequencies of the trailer system. So you want a trailer that dampens these forces and is convergent.
Basically your trailer has only three points of load from the ground.. tires left and right and trailer hitch. The distribution of weight between all three determines the center of mass which determines how the trailer responds. When the center of mass is at the axel (like your battery example) there is no counter force to induced sway. You need mass forward of the wheels to create an opposing force to sway… simple as that.
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Forward mass is the reason the trailer wheels are always behind the centre of the trailer to reduce the possibilty of the the trailer "slingshotting the" TV.
https://www.etrailer.com/faq-where-t...iler-axle.aspx
https://mechanicalelements.com/trailer-axle-position/
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10-28-2022, 05:56 AM
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#95
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Liquid Cooled
2017 27' Flying Cloud
Currently Looking...
Currently Looking...
Currently Looking...
near Indy
, Indiana
Join Date: Mar 2006
Posts: 745
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Quote:
Originally Posted by hairyclive
Forward mass is the reason the trailer wheels are always behind the centre of the trailer to reduce the possibilty of the the trailer "slingshotting the" TV.
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This is a pretty good post, IMO ^
In terms of anecdotes ... I used to pull a Schweizer 1-26 on a trailer. Trailer with sailplane on it probably weighed 1500 pounds, was around 28' long, width varied between 4 & 8 feet, and had a tongue weight of around 50-75 pounds. Was pretty stable up to around 80, but not great after that. I think I buried the speedometer once or twice in the name of experimentation. Oddly, similarly designed trailer with nominally similar characteristics (weights, length, height, etc.) were stable at 70-75. Now, I did have one for a while that had a tongue weight of around 150 pounds and it wasn't very good over 65 but it sat lower to the ground.
I towed with either a short bed regular cab F-150, a 4 cyl Ford Ranger (hey, at altitude it was a better tow vehicle than my friend's diesel Luv), or a 2 door Accord. Known guys to tow them cross-continent with a Fiero and Marion Cruce (RIP) did a lot of towing to competitions in OK, TX, and CO with a VW Beetle, although he didn't recommend the practice.
My anecdotal conclusion? A superficial brush with the numbers isn't particularly useful. I think we all agree that having the center of mass be ahead of the center of pressure does good things for stability, but absent modeling with something pretty interesting (maybe a variation of https://openrocket.info/ ) it's always going to be Joe's anecdotes against Bob's anecdotes, and quite frankly, I'm old enough that the "who yells loudest" school of debate has lost its charm. So ... Math up! 
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10-28-2022, 06:30 AM
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#96
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4 Rivet Member 
Join Date: Oct 2021
Posts: 419
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Coming soon to an EV + trailer
https://www.motortrend.com/news/brem...r-performance/
Quote:
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Installing Sensify on a trailer's brakes with the tow vehicle controlling them promises unprecedented towing safety and stability.
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