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Earthing a truck

This is entirely hypothetical of course! Let's say you had a large petrol powered truck that had to drive along railway lines, and you wanted to earth the truck to the lines. The truck has rubber tyres. Perhaps a small four steel-wheeled wagon that is dragged along under the truck. That's the easy part. When driving the truck, how can you see where the wagon is, so that the truck doesn't derail the wagon? The truck would be 100 times heavier than the wagon, so can't really be connected directly to it except by a towbar and a wire. Possibly a CCTV camera. Yes, that would do. Any other brilliant ideas?

Reply to
Matty F
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Sliding shoe contacts like third-rail electric railway systems - but, obviously, to the running rails rather than the (non-existent) third rail.

Reply to
polygonum

You have seen those trucks with railway wheels on swing arms that actually drive using the tracks rather than the rough track beds?

Reply to
dennis

railway lines, and you wanted to earth the truck to the lines. The truck ha s rubber tyres.

wagon is, so that the truck doesn't derail the wagon? The truck would be 1

00 times heavier than the wagon, so can't really be connected directly to i t except by a towbar and a wire.

Yes, but we will have to use the existing rubber tyres. No rough track beds around here :)

Reply to
Matty F

railway lines, and you wanted to earth the truck to the lines. The truck ha s rubber tyres.

wagon is, so that the truck doesn't derail the wagon? The truck would be 1

00 times heavier than the wagon, so can't really be connected directly to i t except by a towbar and a wire.

OK, I looked up sliding shoe contacts. They don't go over gaps and points v ery well. I think I like four wheels better. I don't want to see sparks!

Reply to
Matty F

Possibly something along the lines of a T shaped metal thing with L shaped brackets on each end, and attached to a towball on the truck would be the simplest. Just make sure that it's always at the trailing end to avoid it catching in the joints.

On the other hand, if this also has to trigger the type of track occupation sensors that most railway lines in this country use, it needs to guarantee a continuous low resistance from one rail to the other to work safely. This implies a good, guaranteed contact to both rails.

What most people in these circumstances do is install a hydraulically controlled bogie with metal rail wheels fore and aft, which carries some of the weight, guides the rubber-tyred vehicle, and guarantees track occupation circuitry triggering.

Reply to
John Williamson

Or slippers.

Reply to
The Natural Philosopher

The wheels on the swing arms are only for guidance and some weight transfer, traction is still through the normal road tyres. You may have a problem with the width of the vehicle not matching the gauge of the line, and with double tyres as used on larger trucks , it would be rather embarassing if the rails were to coincide with the gap between the pair of tyres on each wheel.

What is the vehicle type? If it's a Land Rover, then the tyres are the right distance apart already.

Also, have you thought about the difficulty of steering the thing exactly enough to keep it on the rails? It's not possible at anything above a very slow speed, and even then, the odds are you'll fall off the rails onto the track bed within yards.

Reply to
John Williamson

Why is the earthing so important?

The sparking of UK third-rail is reduced by having more than one fitted so that, most of the time, at least one is in full contact. And you only get spectacular lightning when the train is using a significant amount of traction current. If you are only earthing the truck for low current, the sparking would be insignificant in most cases.

Reply to
polygonum

If track occupancy detection is involved, then a low resistance connection between the rails is vital. On occasion, with track that's not regularly used, it can miss a single truck. In some places, I've seen a bead of weld run along the rail surface to ensure that any rust is removed as soon as the first axle travels along the section.

Another possibility as the OP specifically mentions petrol power, maybe he's worried about sparks igniting fuel vapour. Or he's trying to arc weld....

Reply to
John Williamson

railway lines, and you wanted to earth the truck to the lines. The truck ha s rubber tyres.

wagon is, so that the truck doesn't derail the wagon? The truck would be 1

00 times heavier than the wagon, so can't really be connected directly to i t except by a towbar and a wire.

There is no track occupation circuitry to worry about. The surface around t he track is nice an smooth. The trolley will need to be under the truck so that people can't touch it.

Reply to
Matty F

What?

Why is the most obvious question. Why not just convert the truck to run on the rails?

Brian

Reply to
Brian Gaff

Reply to
Matty F

How about giving us a hint as to why you need to earth the truck. Then we may know of a working solution. Working under tram wires, for instance, needs a different answer to running a high power transmitter in the truck. Which needs a different solution to earthing out a lightning strike.

Reply to
John Williamson

It is earthed. The tyres are conductors, ISTR. They're a synthetic compound, not rubber.

Reply to
Onetap

Just how are you going the keep the rubber tyred wheels on a rail Matty?..

Road-rail vehicles do exist they normally have a separate set of wheels that can be put up or down as required...

Reply to
tony sayer

With carbon black in it to give it the colour. I'd not want to rely on it being less than a few hudred ohms from wheel to ground, though. They'll dissipate static, but not touching and overhead line.

Leaks from live to earth via the tyres used to be one of the main reasons for taking a trolleybus off the road. There was a prescribed test that had to be done before you took one out in the morning.

Reply to
John Williamson

g railway lines, and you wanted to earth the truck to the lines. The truck has rubber tyres.

he wagon is, so that the truck doesn't derail the wagon? The truck would be 100 times heavier than the wagon, so can't really be connected directly to it except by a towbar and a wire.

nd the track is nice an smooth. The trolley will need to be under the truck so that people can't touch it.

Well OK, it will be running under an overhead wire at 600V DC, and needing an earth return. There are several devices that need power, e.g. a welder o r large motors. It will be driven very carefully along the rails. Really I just want any other ideas for how to know where the trolley is und er the truck. I have a spare CCTV camera. Otherwise some kind of indicator to show how central the trolley is.

Reply to
Matty F

Very carefully! The ground is paved on either side of the rails. We already drive ordinary trucks along that.

Reply to
Matty F

Given that an earth conductor should not normally be current carrying, there ought not be any even if the contact is not always perfect.

Reply to
John Rumm

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