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The Contraption

Posted by D869 , in Hayle North Quay, Shunting Tractor 16 March 2018 · 635 views

Thought it might be time to say a few word on here about the thing that's been taking up most of my modelling time since last June.

 

The Esso depot at Hayle North Quay was laid with a kicked back siding. As the quay had no run-round, it could only be worked using a shunting tractor... so my layout needs one of those.

 

It might have been nice to just get on with building the layout and worry about this later but that's really not going to work - the tractor is too small to have an on-board drive so it needs to be driven from below ground and the drive system needs to be designed and tested before the baseboard can be built... so building and testing a mockup is what I've been doing.

 

I need to thank Laurie Adams, John Greenwood and Pixie of this parish, all of whom have provided some of the inspiration for this and in Laurie's case a lot of in-depth info about how his tractor works... but my drive system is not the same as any of theirs.

 

The drive uses an old curtain rail which is curved to follow the line of the Esso siding. A stepper motor and toothed belt moves a carriage to and fro. The carriage has a swing arm to allow the tractor to move about 40mm either side of the siding and a swivelling magnet carrier which allows the tractor to point in any direction. An Arduino Mega and a bunch of stepper motor drive electronics control the whole thing and attempts to make it move in a realistic manner.

 

I won't bore you with the details, let's just say that it's complicated and it's taken a long time to get it this far. It's not yet moving perfectly but it's doing well enough that I'm sufficiently confident that it will work that I can move on to other things. It will need more tweaking when it's installed under the real layout.

 

The tractor... or the mockup tractor anyway
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The inevitable video with me at the wheel... if you can stand watching 2 minutes of it.

 

An overview of the contraption with the lid off... this is NOT the real baseboard.
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The carriage
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The carriage a few months back when you could still see the gear train on the swing arm (it's still there)
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The real Esso Tractor (copyright John Lloyd from http://www.cornwallr...branches.html).

 

I'm going to be modelling a 4WD vehicle from the same manufacturer. Rule 1 and all that.
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  • Craftsmanship/Clever x 11
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That's very good. 

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Northroader
Mar 16 2018 22:13
Very, very clever, — and it works, amazing!
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Kylestrome
Mar 17 2018 07:26

That's working really well.

 

The tank wagon could do with a little bit of built-in friction to stop it lurching forwards. Assuming there is some weight in it, you could try a very lightly sprung wire rubbing against one axle. Alternatively, you can cut a couple of turns from an N gauge coupling spring and put it over the pinpoint of one axle (an idea cribbed from Micro Trains). Either way, I've been doing similar things on Chapel Wharf since the early days, and the end effect is to make wagons move as if they really do weigh a few tons.

 

David

Impressive stuff Andy - The 2 minute vid is very therapeutic ;)

It needs the obligatory pound coin in the pic just to show how small it is :o

Can you tell us more about the layout? Is that balsa used for the inlaid track area?

Very good Andy.  I'm impressed that you managed to avoid driving the tractor where the buildings will eventually go!  I didn't when I played with it the other night :-)  But then you've had a lot more practice, and I'm used to driving a 1/10th scale racing car at around 30mph around a track that's significantly wider than the gaps between the buildings :-)

 

Ian

That's very good. 

 

Very, very clever, — and it works, amazing!

Thank you both.

 

 

That's working really well.

 

The tank wagon could do with a little bit of built-in friction to stop it lurching forwards. Assuming there is some weight in it, you could try a very lightly sprung wire rubbing against one axle. Alternatively, you can cut a couple of turns from an N gauge coupling spring and put it over the pinpoint of one axle (an idea cribbed from Micro Trains). Either way, I've been doing similar things on Chapel Wharf since the early days, and the end effect is to make wagons move as if they really do weigh a few tons.

 

David

 

Thanks David. Yes, some brakes are on the 'to do' list. I have them on some of my 16 tonners but so far none on the oil tanks.

 

Impressive stuff Andy - The 2 minute vid is very therapeutic ;)

It needs the obligatory pound coin in the pic just to show how small it is :o

Can you tell us more about the layout? Is that balsa used for the inlaid track area?

 

Cheers Pete. I tend not to go in for the whole coin shot thing. The layout ain't built yet - this is just a mockup to test out ideas but yes the infill is all done with 1/32 balsa - another idea borrowed from Laurie Adams. I found that there are some big variations from the nominal thickness of the balsa where the grain varies from soft to hard so will need to be more careful in choosing sheets in future. The deck is 1mm PCB - 3 sheets stitched together (with splints made from 16mm scale rail!) but I will order a big sheet for the real layout.

 

Of course the whole contraption requires a completely clear run underneath the board surface so there must be no board cross members, wiring, point tiebars or uncouplers to get in the way. All these things must either be arranged above ground or else some means devised to keep them out of the way when the tractor is coming through.

 

Very good Andy.  I'm impressed that you managed to avoid driving the tractor where the buildings will eventually go!  I didn't when I played with it the other night :-)  But then you've had a lot more practice, and I'm used to driving a 1/10th scale racing car at around 30mph around a track that's significantly wider than the gaps between the buildings :-)

 

Ian

 

I haven't had that much practice. I only drew the building lines on just before I brought it to the meeting. It's pretty tricky to swing the tractor round through the other gate but on the final layout there will be a bit more space - the mockup is truncated at both ends because the bendy bits in the middle are the more important things in terms of proving whether the thing works or not. The result is that the oil depot outlines are rather more constricted than they will eventually be. I just re-checked the drawing and that building by the gate is in reality outside the area covered by the mockup.

 

22mph was the top speed of the tractor I'm modelling although I slowed mine down a bit because I think it was close to the limit in terms of how fast the Arduino can keep up with the trig to work out how to move the steppers.

 

I'm sure you will get another go sooner or later :)

 

Regards, Andy

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A blog about my own modelling projects (as distinct from the St Ruth group layout) - centered around BR WR circa 1968-1972 and my own minimum space 2mm Scale 2FS layout 'South Yard'

 

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