Earthing a truck

[John Rumm]

A pair of parking sensors either side that sense distance to the trolley?

[John Williamson]

And *still* you avoid the T word....

Put the trolley on a towbar with a swivel at each end and drag it behind, or use clips to attach an earth lead when you stop. If you're working under a live overhead line, you'll want an exclusion zone round the truck anyway, so the public tripping over it won't be a problem. Even if you're not working live, it's good discipline to stop and earth the truck before working under overhead wiring anyway. Any time you save by doing it the way you seem to want it will be more than cancelled out by not complying with safety requirements. Also, if you have a tower on the truck, it must be dropped before you move near overhead cables anyway, to keep things safe.

And that's ignoring the risk of working on an earthed platform at height under live wiring. At 600V, if nothing can get within a foot or two of the wire, you don't need the earth anyway.

If you're worried about damaging an earth clip or its cable, connect it via a plug and socket, so if you drive away, it just pulls out.

You seem to be making life both overcomplicated and less safe for yourself.

If you insist on working live, take professional advice.

[Fredxx]

I don't see why not? The limited circumference of a wheel would pass over points with more undulation. I also don't see why you will get less parking. The unsprung weight will exacerbate contact issues.

A shoe with radiused ends is the typical method of conduction on the underground.

An example shoe though not sure where this type of shoe is used:

[Nightjar]

Connect the wagon to the front end of the truck with a single arm trailing link and set it up so that, even if it comes out sideways, the wagon clears the truck wheels. You would then have to be seriously off line with the truck to cause any problems and presumably it is possible to drive the truck along the tracks with sufficient accuracy to avoid that. Making the arm telescopic and sprung to close would give you even more scope for being off line, if needed.

Colin Bignell

[Matty F]

Yes I like having the wagon (I didn't mean to call it a trolley) under the middle of the truck. And if the truck backs up, the wagon will move back too. I think that will do, plus the CCTV. Now to find some small steel wheels and some 200 amp cable! All suitable inspected by qualified engineers and run on private roads of course!

[Colin Stamp]

If you're passing a lot of current through this setup, surely you'll get arcing across the wheel bearings. They won't take kindly to that. At least shoes can be made to take the punishment.

Cheers,

Colin.

[Matty F]

Not that this is anything to do with trams, but trams have a solid axle that the motor rests on via solid bronze bearings. So I could connect the wire to bronze bearings.

[Rob Morley]

Put a flat board on top of the bogey, attach an optical mouse to the bottom of the truck and position it in the middle of the board (I'm thinking suspend it on a couple of bungees stretched side-to-side and fore-aft, so it's centred but still free to move). Plug into your crappy old laptop/tablet PC, move the mouse pointer to the middle of the screen with a second mouse, then unplug it so it doesn't move again. Watch the movement of the mouse pointer as you drive. :-)

[Zapp Brannigan]

That's my favourite kind of project!

[Matty F]

round-your-mouse/

The trolley isn't going to move backwards and forwards, so I really only ne ed to know the sideways movement. Four microswitches could turn on yellow o r red lights in front of the driver. Perhaps that is better than him trying to watch a video screen as he drives.

[Rob Morley]

I just tried to knock together an applet that said "steer left" or "steer right" depending on the position of the mouse, but it's obviously too long since I last wrote any Java. :-(

[Vir Campestris]

You've got me thinking back to David Beaty's "Cone of Silence".

You want a mechanism that sends a beep with a 1/3 mark space ratio when you're off to the left, and a 2/3 when you're off to the right. When on course you thus get a steady tone.

Andy

[Bob Eager]

I remember that. And others.

Makes me very careful to close fuel flaps! (Sword of Honour)

[Rick Hughes]

Most train companies use standard 4x4 or pickups with a set of wheels that can swing down, and these go on track. The tyres still provide motive power, but steel wheels the guidance.

They also have small diggers that can do the same.

Anything towed as long as on a swivel attachment would follow truck

[Nightjar]

He obviously needs an OBOE Cat radar unit on the wagon and a receiver on the truck.

Colin Bignell

[Chris Hogg]

Not relevant to the OP's question, but actually the carbon black does a whole lot more than that. It improves all sorts of mechanical properties of the rubber. No satisfactory alternative has yet been found, and plenty of people have looked as it's a huge market.

[Matty F]

I think some microswitches and lights will do that job. However I've discovered a new problem. Some of the points are spring-loaded closed. A wheel coming from the "wrong" track simply pushes against the sp ring and opens the point for each wheel. So the wheel or skate needs a few hundred kg of weight on it, to open the points. Or the wagon could have a l arge spring forcing it down. Perhaps this picture makes it all clear :)

[polygonum]

But not the need for earthing via the track! :-)

[Matty F]

aded closed. A wheel coming from the "wrong" track simply pushes against th e spring and opens the point for each wheel. So the wheel or skate needs a few hundred kg of weight on it, to open the points. Or the wagon could have a large spring forcing it down.

Yes, if there is only one overhead wire!

[Colin Stamp]

You'll need to arrange it so the truck can never be touched by anyone on the ground. If it should ever lose electrical contact with the track, it'll float to the same voltage as the overhead wire.

Mind you, I suppose the track itself is also a bit worrying. I guess there are stringent rules about making sure all the joints are electrically perfect?

Cheers,

Colin.