Building an RC Traction Engine

gregh

gregh

electronics, computers and scratchbuilding
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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.
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.
rik traction 2.jpg

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 36mm dia
  • Wheels 90mm dia
  • motor dimensions of 75mm long x 30mm high x 35mm wide
  • and needing four AAA batteries.
I sketched it out on Libre Office Draw ( a freebie) in full size. And then got out the 1.5mm styrene!
As usual, the main design problem is how to fit in, and then access the RC and batteries. And where to mount the on/off switch and charging lugs.
2nd attempt design dwg.jpg

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.
tamiya motor gearbox.JPG

progress1.JPG

The boiler will contain 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 will be inside the boiler and will pull out of the from smokebox. (I hope it fits – the wiring is always the thing that takes up lots of space.)
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.

progress3.JPG

And that’s where I’m up to. I have no idea how to make the cylinders on top of the boiler or how to make them operate. I’d hoped to drive them from the main axle by a belt, but space is a bit tight.
I have a further dream, where the picaxe program will allow it to run a ‘pre-programmed route’ automatically, without the RC control.

To be continued……..
 
Was that an old playmobil model? Looks a bit like pictures I have seen of same.
Nice conversion so far.
 
Nice idea Greg, perhaps a Mecanno Belt could be used to get power from the main wheels to the smaller wheel thus driving the cylinders via that way? An elastic band of the right size may even do service so long as you make things so that it easily be replaced.
 
dunnyrail said:
Nice idea Greg, perhaps a Mecanno Belt could be used to get power from the main wheels to the smaller wheel thus driving the cylinders via that way? An elastic band of the right size may even do service so long as you make things so that it easily be replaced.
Click to expand...
I'm hoping I can do something along the lines of a rubber band.
 
I've 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.


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.
Anyone have any other ideas for increasing the friction?
A also suspect I'm trying to turn the wheels too far - 45 degrees max. As I have no expertise in mechanical type stuff, can anyone tell me if it's too much.

I have even managed to test the idea of programming a set sequence to run it over a set route without my driving it.
 
Nicely done, Greg. A transformation!

I reckon weight must be the issue with the steering. You maybe need to counterbalance the weight of the batteries somehow. Any room in the smokebox for a couple of lead strips, or maybe in the front of that box on the boiler ahead of the rear wheels?

Rik
 
How about a micro motor like the HO/OO boys use, to power the cylinders and flywheel so flywheel goes at a different speed to wheels as the real ones seem to do. Also the real ones make a lot of gear noise when they are driving
 
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Super Job Gregh. A couple of possible idea's.

Frint Weight, Traction Engines often have Buckets hanging aroundin varying places. Why not a couple at the front end load with Lead and cosmeticed up to be full of Coal?

Motor Noise, you have effectively created a Speaker Box for the Motor hence the amplified sound. Not sure how much room in that space but perhaps lining it with thin Cork may provide a partial solution.

Good luck with the rest of this great little project.
 
With regards to the steering; the rear axle is fixed I assume? Without a differential the drive wheels will always try to push in a straight line as one needs to slow down/speed up to negotiate corners. Lots of cheaper toy makers get round this by only having one wheel driven with the other able to rotate freely on the axle.
 
This is very cool! It gives me some ideas for how to stratch build rolling stock I'm planning.
 
Lots of ideas there. Thanks.
I will try loosening one rear wheel on its axle, but I suspect one wheel won't have enough drive then.
Nice heavy buckets hanging off the front are a good idea. As a test I taped 60g to the chimney and it worked really well. So I just have to fit in something about that weight.
Ge-rik actually sent me a micro motor with the traction engine, so I'll have a think about how I could use it to drive the pistons.
No-one commented on the use of rubber bands on the front wheels. Do you you think they would work if I glued them on with some 'rubbery' glue, like contact adhesive?
 
gregh said:
Lots of ideas there. Thanks.
I will try loosening one rear wheel on its axle, but I suspect one wheel won't have enough drive then.
Nice heavy buckets hanging off the front are a good idea. As a test I taped 60g to the chimney and it worked really well. So I just have to fit in something about that weight.
Ge-rik actually sent me a micro motor with the traction engine, so I'll have a think about how I could use it to drive the pistons.
No-one commented on the use of rubber bands on the front wheels. Do you you think they would work if I glued them on with some 'rubbery' glue, like contact adhesive?
Click to expand...
Oh I wonder if you could get any of that Snot Stuff they flog in America to use as Traction Tyres, bullfrog snot.

http://www.bullfrogsnot.com/faq.asp

If you were wondering how I know about this stuff in UK, I buy US Mags Model Railway when I see them.
 
gregh said:
Lots of ideas there. Thanks.
I will try loosening one rear wheel on its axle, but I suspect one wheel won't have enough drive then.
Nice heavy buckets hanging off the front are a good idea. As a test I taped 60g to the chimney and it worked really well. So I just have to fit in something about that weight.
Ge-rik actually sent me a micro motor with the traction engine, so I'll have a think about how I could use it to drive the pistons.
No-one commented on the use of rubber bands on the front wheels. Do you you think they would work if I glued them on with some 'rubbery' glue, like contact adhesive?
Click to expand...

Greg
How much room is in the smoke stack, if there is enough room for about 60g of weight possible use some melted solder to fill it. That way the weight will be at a centre point of the steering arm.
45 degrees is to much for steering I would not go more than about 30-35 degrees anything over that and the edges of the wheels will try to "dig in".
You could try rubber bands for traction or adhesive backed rubber strips like this https://www.clarkrubber.com.au/natural-strip-insertion-rubber-6mm-thick
or this https://www.bunnings.com.au/raven-8-x-15mm-2m-rubber-grey-multi-use-sealing-strip_p3970014
 
Many of the original engines were one wheel drive. There was often a pin that could be inserted to lock the second rear wheel to the axel if grip was needed. I am pretty certain all this was done to enable steering.
 
stockers said:
Many of the original engines were one wheel drive. There was often a pin that could be inserted to lock the second rear wheel to the axel if grip was needed. I am pretty certain all this was done to enable steering.
Click to expand...
Yep, I didn't know about the one wheel drive, but we forget how effective a differential is. That's why go-karts always skid round corners so easily even on slick tyres.

Years ago, on a building site, we had a 2w drive Manitou forklift (rough terrain) with a difflock to get you out of trouble. Once you had the difflock on, the steered wheels acted like ploughshares :nod::nod::nod:
 
GAP said:
Greg
How much room is in the smoke stack, if there is enough room for about 60g of weight possible use some melted solder to fill it. That way the weight will be at a centre point of the steering arm.
45 degrees is to much for steering I would not go more than about 30-35 degrees anything over that and the edges of the wheels will try to "dig in".
You could try rubber bands for traction or adhesive backed rubber strips like this https://www.clarkrubber.com.au/natural-strip-insertion-rubber-6mm-thick
or this https://www.bunnings.com.au/raven-8-x-15mm-2m-rubber-grey-multi-use-sealing-strip_p3970014
Click to expand...
I manage to bash a piece of lead into a cylindrical shape and got 20g in the chimney and another 50g in the smoke box and it made a big difference. I did reduce the angle of the steering down to about 35deg by changing the linkage. And I can still get a turning circle of 75cm. without the rubber tyres.

stockers said:
Many of the original engines were one wheel drive. There was often a pin that could be inserted to lock the second rear wheel to the axel if grip was needed. I am pretty certain all this was done to enable steering.
Click to expand...
I tried loosening one wheel on the axle and I could see the wheels turning at different speeds on corners. Didn't seem to affect the turning circle though. So I'll keep that mod 'up my sleeve'.
 
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