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?

On 03/08/2013 05:17, Matty F wrote:
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?

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

--
Rod

On 03/08/2013 05:17, Matty F wrote:
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?


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

On Saturday, August 3, 2013 7:26:38 PM UTC+12, dennis@home wrote:
On 03/08/2013 05:17, Matty F wrote:

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?





You have seen those trucks with railway wheels on swing arms that

actually drive using the tracks rather than the rough track beds?

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

On Saturday, August 3, 2013 7:26:37 PM UTC+12, polygonum wrote:
On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems - but,

obviously, to the running rails rather than the (non-existent) third rail..

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

Matty F wrote:
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?

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.

--
Tciao for Now!

John.

On 03/08/13 05:17, Matty F wrote:
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?
metal brushes.
Or slippers.

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.

Matty F wrote:
On Saturday, August 3, 2013 7:26:38 PM UTC+12, dennis@home wrote:
On 03/08/2013 05:17, Matty F wrote:

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?


You have seen those trucks with railway wheels on swing arms that

actually drive using the tracks rather than the rough track beds?

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

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.

--
Tciao for Now!

John.

On 03/08/2013 08:48, Matty F wrote:
On Saturday, August 3, 2013 7:26:37 PM UTC+12, polygonum wrote:
On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems - but,

obviously, to the running rails rather than the (non-existent) third rail..

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

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.

--
Rod

polygonum wrote:
On 03/08/2013 08:48, Matty F wrote:
On Saturday, August 3, 2013 7:26:37 PM UTC+12, polygonum wrote:
On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems - but,

obviously, to the running rails rather than the (non-existent) third
rail..

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

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.

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....

--
Tciao for Now!

John.

On Saturday, August 3, 2013 7:48:52 PM UTC+12, John Williamson wrote:
Matty F wrote:

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?



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.

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

What?

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

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Matty F" wrote in message
...
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?

But I can't alter a heritage vehicle. And if people know what I'm on about, I won't be able to do it.

On Saturday, August 3, 2013 8:40:25 PM UTC+12, Brian Gaff wrote:
What?



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

the rails?



Brian

Matty F wrote:
On Saturday, August 3, 2013 7:48:52 PM UTC+12, John Williamson wrote:
Matty F wrote:

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?


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.

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

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.

--
Tciao for Now!

John.

On Saturday, August 3, 2013 5:17:15 AM UTC+1, Matty F wrote:

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.

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

In article , polygonum
scribeth thus
On 03/08/2013 05:17, Matty F wrote:
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?

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


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...

--
Tony Sayer

Onetap wrote:
On Saturday, August 3, 2013 5:17:15 AM UTC+1, Matty F wrote:

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.

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


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.

--
Tciao for Now!

John.

On Saturday, August 3, 2013 8:51:37 PM UTC+12, John Williamson wrote:
Matty F wrote:

On Saturday, August 3, 2013 7:48:52 PM UTC+12, John Williamson wrote:

Matty F wrote:



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?





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.



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



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.

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 or 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 under the truck. I have a spare CCTV camera. Otherwise some kind of indicator to show how central the trolley is.

On Saturday, August 3, 2013 9:42:26 PM UTC+12, tony sayer wrote:
In article , polygonum

scribeth thus

On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems - but,

obviously, to the running rails rather than the (non-existent) third rail.





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

Matty?..

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

On 03/08/2013 08:48, Matty F wrote:
On Saturday, August 3, 2013 7:26:37 PM UTC+12, polygonum wrote:
On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems -
but,

obviously, to the running rails rather than the (non-existent)
third rail.

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

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


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 03/08/2013 11:10, Matty F wrote:
On Saturday, August 3, 2013 8:51:37 PM UTC+12, John Williamson
wrote:
Matty F wrote:

On Saturday, August 3, 2013 7:48:52 PM UTC+12, John Williamson
wrote:

Matty F wrote:



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?





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.



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



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.

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 or 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 under the truck. I have a spare CCTV camera. Otherwise
some kind of indicator to show how central the trolley is.

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


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Matty F wrote:


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 or 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 under the truck. I have a spare CCTV camera. Otherwise some kind of indicator to show how central the trolley is.

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

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.

--
Tciao for Now!

John.

On 03/08/2013 08:48, Matty F wrote:
On Saturday, August 3, 2013 7:26:37 PM UTC+12, polygonum wrote:
On 03/08/2013 05:17, Matty F wrote:

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?



Sliding shoe contacts like third-rail electric railway systems -
but,

obviously, to the running rails rather than the (non-existent)
third rail.

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


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:
http://www.railway-technical.com/shoe-02.jpg

On 03/08/2013 05:17, Matty F wrote:
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?


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

On Saturday, August 3, 2013 10:40:18 PM UTC+12, Nightjar wrote:

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.

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!

On 03/08/2013 08:48, Matty F wrote:

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

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.

On Sunday, August 4, 2013 12:12:45 AM UTC+12, Colin Stamp wrote:
On 03/08/2013 08:48, Matty F wrote:



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



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.

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.

On Fri, 2 Aug 2013 21:17:15 -0700 (PDT)
Matty F wrote:

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?

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. :-)
http://www.cyberciti.biz/open-source...nd-your-mouse/

On Sunday, August 4, 2013 3:29:18 AM UTC+12, Rob Morley wrote:

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. :-)

http://www.cyberciti.biz/open-source...nd-your-mouse/

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

On Sat, 3 Aug 2013 17:40:29 -0700 (PDT)
Matty F wrote:

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

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. :-(

On 04/08/2013 22:14, Rob Morley wrote:
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.:-(

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

On Sun, 04 Aug 2013 23:25:28 +0100, Vir Campestris wrote:

On 04/08/2013 22:14, Rob Morley wrote:
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.:-(

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

I remember that. And others.

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

--
Use the BIG mirror service in the UK: http://www.mirrorservice.org
My posts (including this one) are my copyright and if @diy_forums on
Twitter wish to tweet them they can pay me £30 a post
*lightning surge protection* - a w_tom conductor

On 03/08/2013 05:17, Matty F wrote:
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?

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

On 04/08/2013 23:25, Vir Campestris wrote:
On 04/08/2013 22:14, Rob Morley wrote:
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.:-(

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.

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

Colin Bignell

On Monday, August 5, 2013 8:17:40 PM UTC+12, Nightjar wrote:
On 04/08/2013 23:25, Vir Campestris wrote:

On 04/08/2013 22:14, Rob Morley wrote:

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.:-(



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.



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

the truck.

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 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.
Perhaps this picture makes it all clear

http://i39.tinypic.com/ny71gy.jpg

On 08/08/2013 05:52, Matty F wrote:
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 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.
Perhaps this picture makes it all clear

http://i39.tinypic.com/ny71gy.jpg

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

--
Rod

On Thursday, August 8, 2013 6:18:45 PM UTC+12, polygonum wrote:
On 08/08/2013 05:52, Matty F wrote:

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 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.

Perhaps this picture makes it all clear



http://i39.tinypic.com/ny71gy.jpg



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

Yes, if there is only one overhead wire!

On 08/08/2013 08:39, Matty F wrote:
On Thursday, August 8, 2013 6:18:45 PM UTC+12, polygonum wrote:
On 08/08/2013 05:52, Matty F wrote:

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 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.

Perhaps this picture makes it all clear



http://i39.tinypic.com/ny71gy.jpg



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

Yes, if there is only one overhead wire!


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.

On 08/08/2013 08:39, Matty F wrote:
On Thursday, August 8, 2013 6:18:45 PM UTC+12, polygonum wrote:
On 08/08/2013 05:52, Matty F wrote:

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 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.

Perhaps this picture makes it all clear



http://i39.tinypic.com/ny71gy.jpg



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

Yes, if there is only one overhead wire!

But how did it work in the past? If it has rubber tyres and one overhead
wire...

I still say, if it needs to be earthed to the rails, then something that
slides on the rail is the perfect counterpoint to something that slides
on a wire.

--
Rod

On Friday, August 9, 2013 3:35:36 AM UTC+12, Colin Stamp wrote:

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.

But people used to touch trams when they boarded. They had earthed metal handrails. How is that different?


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?

The rails are all welded together.