Garden Railway Forum

I’ve been trying to NOT build any more locos as I have run out of storage room.
But I’ve bent my rules again and decided to build a radio controlled (road) traction engine.
Maybe I can drive it around the loungeroom? But it would be nice to see it trundle along Lilyvale’s main street. To do this it will need to be able to have a turning circle of max 30cm.
If all else fails I can mount it on a flat car.

Making the wheels has always been the impossible sticking point for me, but when ge_rik mentioned he had a simple model he didn’t need, I took it off his hands.
It turned out to be too small for me to put RC in, but I used the wheels and started from scratch to build the body.
I had an old solid vacuum cleaner hose 36mm dia and it looked right for the boiler. I also had a Tamiya motor/gearbox, I’d bought long ago but was too wide for a 45mm gauge loco. It seemed the speed would be slow enough for a traction engine, even with it’s large dia wheels.

So I started the design, based on the parameters of
• boiler dia 36mm
• Wheels 90mm dia
• motor dimensions of 75mm long x 30mm high x 35mm wide
• and needing four AAA batteries.

The main ‘box’ (what else can I call it?) contains the motor with the boiler above.
The motor is screwed to a base of 1.5mm styrene with aluminium angles to allow it to be screwed up into the main ‘box’, which is hollow. The top of the box is held on by magnets. The boiler contains the hobbyking 2.4 GHz receiver and I’ll use my own design Picaxe controller for :
• speed (using the Picaxe PWM command and a FET),
• direction (5V relay with DPDT contacts) and
• steering (Servo, using chains to the front axle).
All this is inside the boiler and will pull out of the from smokebox.
The batteries are four, NiMH AAA 900 mAh cells mounted under the floor of the driver’s standing space.
I don’t think I can find space for a speaker, so there will probably be no sound system.

Here it is roughly put together to check how it looks.
I've now got as far as getting the RC electronics to work so I can test if it will really work and if I should continue.
This video shows the progress so far - the basic body shape, undercoated but no detailing
It also shows test driving it around Lilyvale main street which is the purpose of the whole exercise.

https://youtu.be/TrooWm2IwOo

There are 2 problems:
1) the horrible gear noise (how come I never noticed it before?)
2) the steering - the front wheels don't have enough grip. I think I need more weight over the wheels but have little space to fit any.
I have tried putting a couple of rubber bands around the wheels and that has helped enough to convince me I can somehow over come the problem. It can actually turn the sharp corners of the street which was my main worry.

I have even managed to test the idea of programming a set sequence to run it over a set route without my driving it. (So I can drive my train and have the traction engine trundling along the street in the background.)

Great looking transformation, Greg. If anyone can program a Picaxe to control her movements up the street, then you're top of the shortlist. Maybe you'll have to fit sound, to mask the gear noise

Rik

Looking good so far Greg - like the way you ran across the grass whilst turning!

As for the weight on the front wheels, it looks as though the front axle is mounted to a block of wood under the smokebox, currently? Could you cast a block of lead to do the same thing?

philipy wrote: Sat Apr 21, 2018 7:48 am Looking good so far Greg - like the way you ran across the grass whilst turning!

As for the weight on the front wheels, it looks as though the front axle is mounted to a block of wood under the smokebox, currently? Could you cast a block of lead to do the same thing?

I've never tired casting lead. But it's a great idea - maybe I can fabricate it somehow.
The plastic chimney is hollow, so it's another possibility to be filled with lead.
Maybe some lead sheet around the motor would reduce the noise too

Great video, but I don’t think putting lead around the gearbox would help much, but the lead in the smoke box would and it’s easy to fold to shape in the smoke box.

FWLR wrote: Sat Apr 21, 2018 10:38 am Great video, but I don’t think putting lead around the gearbox would help much, but the lead in the smoke box would and it’s easy to fold to shape in the smoke box.

But the smoke box has the electronics in it. I can perhaps fit a little lead, but not very much.
It's going to be little bits everywhere I can manage.

Fair comment, little bits are still better than a great big lump though, but it’s your build and it is what ever is best really. Try different ways of doing it and see what works.

Great build Greg.

Going to throw this one out there but to make your automation easier can you not place a magnetic strip or some rails for the traction engine to use so you don't have to worry about steering?

You only then need to code speed, forward and reverse.

gregh wrote: Sat Apr 21, 2018 9:49 am I've never tired casting lead. But it's a great idea - maybe I can fabricate it somehow.
The plastic chimney is hollow, so it's another possibility to be filled with lead.
Maybe some lead sheet around the motor would reduce the noise too

It will be an interesting project and should keep you off the streets for a while.

Lead is easy enough to cast, all you need to melt it is an old soup ladle and a blowtorch, or a gas ring.

You can cast lead into a plaster mould, but you need to make very, very sure the mould is perfectly dry before putting hot metal into it.....

I don't know if it is still easily available, but Woods Metal (Cerrobend) has a melting point of 70degC and is useful for weighting models, as it is safer to handle and can be cast into a plastic, or a wooden mould.

Be wary of using lead shot for weighting. It's an easy way of placing weights into any odd nooks and crannies, but it can corrode and then expands enough to break a model apart.

If all else fails a slug of brass or steel is still a lot heavier than a wooden or plastic block. You can't beat lead sheet as an acoustic barrier, but a bit of thick grease also helps with noisy spur gear boxes.......

Regards,
Graeme

Fabricate a small brass box of the right dims, silver solder the joints and then just pour molten lead ( or Woods Metal - good idea) in and leave it.

I found this item when looking on Ebay, which has some interesting info on uses, further down the listing.https://www.ebay.co.uk/itm/Cerrobend-wo ... SwWMFa2kVv

GTB wrote: Sat Apr 21, 2018 2:03 pm Be wary of using lead shot for weighting. It's an easy way of placing weights into any odd nooks and crannies, but it can corrode and then expands enough to break a model apart.
Regards,
Graeme

Hi Graeme
Would the same apply to .22 airgun pellets do you think? I've used them for weighting one of my locos. I smothered them with UHU to stop them rattling around so, hopefully, they're insulated from the air - but they're also now impossible to remove.

Rik

GTB wrote: Sat Apr 21, 2018 2:03 pm
Lead is easy enough to cast, all you need to melt it is an old soup ladle and a blowtorch, or a gas ring.

I don't know if it is still easily available, but Woods Metal (Cerrobend) has a melting point of 70degC and is useful for weighting models, as it is safer to handle and can be cast into a plastic, or a wooden mould.
Be wary of using lead shot for weighting. It's an easy way of placing weights into any odd nooks and crannies, but it can corrode and then expands enough to break a model apart.
If all else fails a slug of brass or steel is still a lot heavier than a wooden or plastic block. You can't beat lead sheet as an acoustic barrier, but a bit of thick grease also helps with noisy spur gear boxes.......
Regards,
Graeme

Not so easy since I have no blowtorch or gas ring. And it sounds 'scary' to me. I do have some Woods metal 'somehwere'.
I'll use steel if all else is too hard.
I did a test and found that 60g of weight on the front works wonders, so all I have to do is aim for that.

tom_tom_go wrote: Sat Apr 21, 2018 1:14 pm Great build Greg.
Going to throw this one out there but to make your automation easier can you not place a magnetic strip or some rails for the traction engine to use so you don't have to worry about steering?
You only then need to code speed, forward and reverse.

A good suggestion. No idea how to start though. I've seen 'white line follower' type controls used in robots, but how does a buried magnetic strip work?
My present idea of controlling steering as well seems to be impossible. It's like the 'butterfly effect' - a small error in steering, such as caused by slop in the steering, or even a stone on the road, magnifies as you go along.
Maybe strategically placed 'guide' rails' along the route would help get it 'back on the rails'

gregh wrote: Sun Apr 22, 2018 12:32 am I've seen 'white line follower' type controls used in robots, but how does a buried magnetic strip work?

Assuming that a strip could be magnetised strongly enough, then two reed switches mounted just inside the front wheels could detect when they approached and/or moved away from the strip and trigger an appropriate twitch to the steering. How easy that would be in practice and how effective, is another matter, of course.

Sunday update.
I managed to bash a bit of lead into a cylindrical shape which gave me 20g in the chimney. Then 25g under the electronics board and a circular piece of 25g glued on the inside of the smoke box door. A great improvement, even without the rubber band tyres.
I also rewrote the picaxe program so the steering has a delay and now takes 1 second to go from centred to full right or left. Looks a lot better.
And I reduced the max angle of turn of the front axle from 45 degrees, and can still get it to turn within a 70cm dia circle (measured over the outside wheels).

So now it's time for a bit more modelling of the details like cylinders - I've decided they will be static. And the roof.

[Don't you hate it when you make a model and show to your wife trundling around the floor and she says " that's cute - but what is it?" ]

philipy wrote: Sun Apr 22, 2018 6:28 am Assuming that a strip could be magnetised strongly enough, then two reed switches mounted just inside the front wheels could detect when they approached and/or moved away from the strip and trigger an appropriate twitch to the steering. How easy that would be in practice and how effective, is another matter, of course.

This all sounds like an interesting future project! But I just remembered that the 8pin picaxe I'm using has no spare I/O pins so I can't add any extra inputs like reed switches.

At least your wife acknowledgeds your railway efforts Greg

Regarding the magnetic road I was thinking you just need the front wheels to be magnetic (or replace them with a metal roller wheel so it becomes a steam roller) and then place a magnetic strip or strategically placed magnets along the route.

Neodymium magnets are very strong and survive outside as mine have not corroded or lost any of their magnet charge (I use them for uncoupling).

ge_rik wrote: Sat Apr 21, 2018 2:57 pm Would the same apply to .22 airgun pellets do you think? I've used them for weighting one of my locos. I smothered them with UHU to stop them rattling around so, hopefully, they're insulated from the air - but they're also now impossible to remove.

Hi Rik,

I've started a new topic, as the reply is long and not really relevant to Greg's thread.

https://gardenrails.org/forum/viewtopic ... 29&t=11777

Graeme

gregh wrote: Sun Apr 22, 2018 12:32 am My present idea of controlling steering as well seems to be impossible. It's like the 'butterfly effect' - a small error in steering, such as caused by slop in the steering, or even a stone on the road, magnifies as you go along.
Maybe strategically placed 'guide' rails' along the route would help get it 'back on the rails'

I did wonder how reliable a programmed path would be, without some form of location feedback.

You might be able to use something similar to the Faller Car System which is made in HO and N scale and has been around for years. I've seen it used on layouts locally at exhibitions and it appears to work reliably. The steering is purely mechanical, no electrickery involved.

The system uses a small neodymium magnet on a steering arm under a battery powered vehicle to follow a steel wire laid just under the road surface.

In garden scale the old Australian standby of fencing wire would probably work as the guide wire, if it was embedded in a cement road surface. The Faller models have Ackerman steering, but I can't see why it wouldn't work with the farm cart steering used on traction engines.

The description of the Faller System on the UK importers website should give you an idea of how it works. The magnet is mounted on the top of the brass skate that slides along the surface of the road, keeping the magnet to wire distance fairly contant.

http://www.gaugemaster.com/articles/pro ... ystem.html

Regards,
Graeme