Sunday, June 26, 2016

How I motorised a ModelTown steam wagon

The 16mm scale ModelTown Foden steam wagon kit is no longer available. I bought mine secondhand already made up with a view to having it as a static model in the station yard at Beeston Market. However, while making a time-lapse video of the station in operation over the period of a day's timetabled session I decided to animate the steam wagon.

This prompted a fellow modeller to enquire as to whether I planned to put the wagon under radio control. Well, I like a challenge and so .......

Planning

The wagon is constructed from a series of resin mouldings - the first job was to decide where I could attach a motor.

The underside was quite open but I felt it would be relatively straightforward to connect a motor to the rear axle.

I had a few small 12v gearbox motors to hand which I'd purchased a while back with the intention of using them for powering small locos. However, they were smaller than expected and so I felt they might be insufficiently powerful for locos - but ideal for a road vehicle.

Motorisation

The rear axle was detached - a piece of 2mm bore plastic tube provided the bearing for the axle and so I needed some other way of mounting the axle to enable a bevel gear to be attached.

A couple of L shaped brackets were bent up from some 1.5mm brass sheet and drilled with 3mm holes.

These were attached behind the axle supports with Gorilla Glue.

The motor was bolted to another L-shaped brass bracket which was, in turn, bolted to the base of the wagon.

A pair of 3mm bore bevel gears were acquired from MotionCo and one was forced on to the motor shaft and fixed in place with some Loctite adhesive.

A piece of 3mm diameter brass rod was cut for the axle and the other bevel gear fixed to it with more Loctite. A couple of rubber wheels (from Technobots) were attached to the ends of the axle. I tried finding wheels which were more traction-engine style but I could find none of the right size.

Steering

The front axle assembly was removed (it was held on by a small nail). The same arrangement for mounting the axle was used here - a length of 2mm bore plastic tube.

The tube was cut to remove the centre section and the remaining two lengths of tube were reamed out (with a 3mm drill bit). A length of 3mm brass rod was cut and smaller plastic wheels attached to the ends.

 The wheels needed to be smaller than those provided to enable the front axle to swivel under the cab for steering.A couple of 16mm diameter holes were drilled into the bottom of the firebox moulding to accommodate a small servo.

 The holes were tidied up with the blade of a craft knife....... 

........ to enable the servo to slot into place.

 Two hooks were fashioned from some copper wire ......

..... and inserted into holes drilled in the front axle mount. These were then connected to a swivel arm on the servo with some brass chain.

Wires were led from the servo and the motor through a hole in the floor of the wagon body.

Wiring and control

I decided to use what resources I had to hand and so I used an RC Trains / Deltang Rx102 and a Brian Jones Mac5 ESC. The output from Channel 1 of the receiver was connected to the ESC and the output from Channel 4 (pin2) on the receiver was connected to the steering servo. Power was provided for the ESC by six AA alkaline batteries (9v). The receiver was, of course, powered by the ESC.

I could have used a conventional joystick transmitter to control the wagon, but I was keen to see how re-setting the inertia control on one of my RCT-Tx22 transmitters would work.

By waiting until the transmitter had been switched on for at least a minute, the bind button was then held down for around 20 seconds until the Tx LED went out and came back on again. Releasing the bind button then changed the function of the inertia control knob so that it now controlled Channel 4 (repeating the process changes the knob's function back to controlling inertia) - see RC Trains - Transmitters for more information.

I am pleased to say that the wagon and transmitter performed well.

  There is still plenty of work to do. The wagon needs a fair amount of additional detailing and a new paint job - but I have shown that the system is workable. It seems that, in a later life, these wagons were equipped with pneumatic tyres and so, if I am unable to source any spoked wheels resembling those used on the early steam wagons, then I may continue with my 'temporary' plastic wheels.

My mate in Australia (Greg Hunter), has suggested that maybe I could put the wagon under automatic control using a Picaxe microprocessor. Rather than having to control the wagon from a transmitter, the wagon would be programmed to come 'on stage' at the station, pull up to the goods yard, perform a three-point turn, wait to be loaded and then depart. I must admit that this is tempting. My main focus during operating sessions is running trains, and so this sort of automation is very attractive - as they say, watch this space!




2 comments:

Peter Mack said...

good work Rik.

that's a nice little unit, and cleverly modified- pretty good for an experiment.
I like the sound of Gregs suggestion, So I'll look forward to news.
cheers

Peter mack

Ge Rik said...

Thanks Peter.
Might be a while yet. Got quite a few other jobs on the to do list.
Rik