Electric (road) train

[freebeard]

An interesting means of system integration.


justacarguy.blogspot.com/2025/08/compared-with-diesels-electric-prime.html

The product is an electric motor dolly that can be spliced between the tractor and trailer of any standard diesel semi-truck and then propel the truck via its electrically driven axle.

Power comes from a battery carried on the dolly with a 575-kWh capacity that's comparable to batteries in fully electric prime movers. Revoy says it offers a range of about 250 miles (400 km), and a higher-capacity unit is in the pipeline.

[Piotrsko]

So we get to have wider travel lanes to accomodate the out of possition the trailer can have? Ever been behind a 3 trailer truck in a crosswind?

[freebeard]

Good question. Does the short wheelbase mitigate the effects? Would differential torque between the two pivot points allow further mitigation?

[redpoint5]

Looks fun to back up!

[Piotrsko]

Originally Posted by freebeard

Good question. Does the short wheelbase mitigate the effects? Would differential torque between the two pivot points allow further mitigation?

Short wheelbase <> 20 ft, should make the lane offset smaller, so maybe. I have seen only one triple trailer UPS truck on the highway, but going the other way.

Don't see a lot of double dumps running short connection and we have length limits. Not sure your comment about differential torque.

Got to see an Aussie land train up close and personal while the driver took a break. They must have figured it out or they don't care since they drive on dirt not on asphalt regular roads. They also had 12 tire 3 axle undercarriage, so like a hundred tires per truck

[freebeard]

I have seen only one triple trailer UPS truck on the highway, but going the other way.

I recall climbing a grade in the South Salem hills on 1-5 decades ago, and I passed a double, a triple and a super single. It was a solid wall of truck the whole way.

Torque steering would be cheaper than a steerable axle.

[Piotrsko]

Steering axles must be relatively inexpensive, have a poop pot load of 22 wheel 15 (?) Yard dump trucks with as many as 6 that follow the front wheels in various amounts. Would think it beats scuff/drag on turns

[redpoint5]

Will be fun times when a jack-knifed tractor/trailer that has the highway shut down has the added bonus of a battery fire that keeps reigniting for the next 24hrs.

I wonder if that might be part of the delay of Tesla getting the semi to market? Jason would be better informed.

As a tangent, AI is saying fuel represents about 25% of trucking operating costs, which is 2nd to driver wages. My guess is electric "fuel" could cut that cost by 2/3rd. Charging would then represent about 10% of the operating cost.

[Piotrsko]

Hate to point out they generally don't relight. They stay burning. Only way to extinguish is to isolate all the reactive components from the heat and internal oxidizers and that's not gonna happen the way we use them now.

Might look like it is out, but until it gets back to ambient temperature, it's a fire just sleeping.

[Ecky]

Bandaid "fix", when the system fundamentally needs a re-think. I applaud the ingenuity here, but there are deeper issues.

Road damage goes up by log scale with vehicle weight. 50,000lb trucks do most of the damage to roads where they operate. Trucks (or their owners) do not pay proportionately toward road maintenance. In other words, they're implicitly subsidized. A lot. Fuel would be among the least of their concerns.

Alternative methods of transport are not used, in part because they can't compete on price versus the aforementioned subsidized transport methods, and in part because laws prevent them from even operating. See the "Jones Act" regarding why ships are not used between US ports. Freight rail is basically fully privately owned and self-funded.

~

That aside, designing a system from the ground-up to operate on roads, I'd go with a powertrain similar to how diesel trains operate. Which is to say, electric motor at the wheels, with the engine acting as a generator. This gives the option to choose a battery size (or not at all) to have some electric-only range, downsize the engine, and get rid of the transmission.