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Comment by WindyTree | Hacker News Reader

In the US, commercial trailers are used like these crappy sheds, you go get one and the ABS unit is gone, the only thing worth stealing. For any company where this doesn’t hold it’s a big deal. The bigger deal is really RV trailers. You power assist, with simple motors controlled by pulling, and you can pull a huge one with ANY car, you don’t need truck, just modified mirrors. Plus the RV trailer benefits from slow self movement and power wall when disconnected. Total off grid tiny home.

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In practice it's of course not so simple. Every truck that passes you (or that you pass) will suck you right in if your tow vehicle isn't heavy enough or you don't have good enough grip. Also, (RV/drum) trailer brakes suck so hard that you really want a vehicle with some additional stopping power other than regular brakes (heavy duty transmission, big engine, and diesel exhaust or compression brake). E-brakes work well so there the e-assist trailer has a real advantage if it can do that but you'll have to get used to the feeling of being pulled back rather than leading the stop... So evy 6.7l diesel I tow a big RV and e-assistance would be very welcome but costs likely drastically reduce the attractiveness of such a system for an RV. For a trailer that's constantly on the road I can definitely see a use case but it's not to be towed by a (comparatively) tiny car

Or flip the narrative and put the steering wheel in the RV trailer and tow your tiny car behind it!

Wait...

Obligatory VW trailer assist ad:

https://www.youtube.com/watch?v=bvZuSxibyYE

lol! Good point: Really it’s the integrated vehicle components that make motorhomes cost so much more than towables. In trucking, the triples trailers don’t have front axles, they’re added through converter dollies. That’s really all you need to make this work, a motorized steerable converter dolly and you can use it with any existing trailer. It only needs to be able to steer, maybe through combining different wheel speeds. they are basically moving trailers already this way with robot Dollies in China.

Realistically you can digitally tow the trailer at that point, you don’t even need the connection, just the promise the trailer following your tracks and staying close behind.

> Every truck that passes you (or that you pass) will suck you right in if your tow vehicle isn't heavy enough or you don't have good enough grip

You'd think you'd ever see some evidence of this happening and right now at the height of Tourist Season you'd expect to see the roads littered with smashed caravans, but no - it does not appear to happen.

It has happened people I personally know. It wasn't just a truck passing, it was a truck passing with a good cross wind, which is why it isn't common. This wasn't a small tow vehicle, it was a F350 which is a large truck even by US standards, and it has a heavy duty frame. At least the truck was strong/heavy enough to say out of the ditch and could safely be moved to the side of the road unlike if it was a smaller tow vehicle.

Yeah, driving semi on tight two lane roads there’s be a whip cracking sound when we passed by other semis close, the two air vortexes colliding.

But I think it’s surmountable. Someone in this thread joked you could put the steering wheel in the RV, which is of course done, so really it’s just a question of RV motion not compatible with car. I could imagine problems with this, if the stopping distance of the RV is higher as it is in loaded semis, you need a feedback mechanism to the car not destroy the brakes of the car, same with pulling. Really the advantages are too high, solar charging, weeks of battery, ability to slow move with no car, but no restraints of being a motor vehicle.

> and you can pull a huge one with ANY car, you don’t need truck, just modified mirrors

So pretty much like everywhere outside the US?

Here in the UK it's not uncommon to pull a 1500kg caravan with a bog standard Ford Focus, without any problems at all, and well over two tonnes on a twin-axle one with something like a Volvo V60.

People come from all over Europe to holiday here with their caravans, and are towing them at "realistic Autobahn speeds" behind perfectly ordinary cars.

It just seems to be the US where you need a 7.5 tonner to pull a trailer the size of a suitcase.

Those are small trailers that you can pull with small cars in the US. The US has many RVs that need much larger trucks to pull them as well. I don't have much autobahn experience, but I don't recall ever seeing a RV type trailer like are somewhat common in the US.

Even if your car can pull the trailer, that doesn't mean you should. If the trailer is oversized the car and engine can pull it - but you need something much bigger/heaver to control the load if anything goes wrong. More than one person has had their car roll because they were towing a large trailer at high speed and a wind gust pushed them into the ditch. If they were towing at city street speeds they would have been okay, but not autobahn speeds.

You don't need a 7.5 tonner to pull a small trailer. However you do need to carefully check the tow rating, bad things happen if the tow vehicle is too small. You do need a 7.5 tonner to pull a large trailer though.

European caravan trailers are generally designed with a much lower tongue weight, like only 4%. This reduces strain on the tow vehicle at the cost of reduced stability. It is ridiculously dangerous to tow such a trailer at full "Autobahn speeds". You might be able to get away with it on a straight road if nothing goes wrong but a sudden maneuver or even a strong gust of wind can lead to uncontrolled oscillation and a roll-over crash.

https://www.theautopian.com/heres-the-physics-behind-tongue-...

US trailers are generally designed with something like 10-15% tongue weight which allows for much higher dynamic stability but also requires a much stronger tow vehicle. As usual there is no free lunch in mechanical engineering.

Uh, you still need suspension on the tow vehicle capable of the tongue weight. And enough mass that a gust of wind doesn’t push you over a lane.

This would be based on a different wheel configuration. The control shaft fixed to the car essentially works to steer a pair of front wheels, and may steer back wheels to minimize off tracking.

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