When I was considering doing some animation with my earlier Mine Trolley for Stopmotion I decided that maybe a Go-Motion version would be better because it would allow a bit of motion blur and maybe be more fun to film. At about that point I realised I was kidding myself if thought I was ever going to do any animation – building the props was much more fun.
I wrestled with the design for a while trying to fit the batteries into the crate while still allowing room for the motor and any figurines. Eventually I reluctantly added the truck to carry the control board and the battery. This game me plenty of space for the “driver” as well as an opportunity to greeble up the motor. Luckily the trolley still has enough traction to pull the truck. The Truck is pretty much just the previous mine truck design with the only modification being the addition of a hole in the front buffer to take the wires to the motor.
Initially I designed it to use a Tamiya 70103 Gear Motor I had kicking around. When I did some calculations on the fastest gear ratio it had, I found the whole trolley would crawl along at the speed of an arthritic snail. So I changed to using a 12V gear motor. This meant that I also needed to change the battery to something with a bit more grunt than the handful of 1.2V NiMh AAs I was intending to use. So a 3S LiPo battery entered the design.
In the end I came up with a design that moves along the tracks at a moderate speed. I would still say it is slow. Unfortunately the chain drive arrangement has too much slack in it. As the trolley moves over the not-particularly-smooth-and-even tracks the different axles get a chance to grip at different times. The slight slack in the chain means that the motion is a bit uneven. In my opinion it is a bit too uneven to really use. Despite the ability move the axles to take up the chain slack I think the problem is that the chain I have used stretches gradually. While it may start off moving quite well, five minutes later it is getting a bit rough. So I present this as an interesting but ultimately not that successful project. If you build it maybe you’ll come up with a better scheme.
Building the Go-Motion Mine Trolley
There are some detailed instructions for putting this together as well as the various electronics and programming required to get it to work. These can be found here:Go-Motion_Trolley_Assembly.pdf
This project pulls on the work described in this page: DC Motor Motion Sequence Controller. The circuit and control sketch are the same. I have included this information in the Go_Motion_Trolley_Assembly.pdf Guide linked above.
The parts list can be found in the assembly guide along with step by step instructions for putting the thing together.
If you have a different chain for the drive (as it is likely you will), the chain drive pulleys are parametric and use the OpensCAD file described on this page: Parametric Chain Link Drive Pulley. I have uploaded this model to Thingiverse’s Customiser if you would prefer to do it that way. Parametric Chain Link Drive Disk - Thingiverse
Unlike the Stop-motion version of this Mine Trolley, the axles must rotate freely and so I used steel axles. These were simply large nails cut to the right length with their ends smoothed.
The bins mounted on the 3D Printed chassis are made from ice-block sticks.
The other item of note is the tarpaulin covering the battery and electronics. This was made using a technique I read about in “How to Build Dioramas” by Sheperd Paine. It was simple and effective. Basically you drape wetted tissue over the shape and then harden it with PVA glue or something similar.
First I made the rough shape I wanted underneath the tarpaulin by piling some wood blocks into the unfinished iceblock stick bin.
Then I layed over a thin plastic bag to prevent the glue from sticking the tissue to the bin (seeing as I wanted to lift it off to get to the batteries and controller). I painted it with water, and then followed up with some house paint acrylic to firm it up.
Once the final layer of paint was dry I lifted the tarpaulin off and trimmed it to size. As I trimmed it I found the plastic bag separated from the tissue shell quite easily and I was left with a tidy little model tarpaulin with enough rigidity to withstand being placed on the truck bin without distorting or falling a-skew.
And that was that. Done.
Download the Model Files
So here are the model files in an STL format.
This design by Hamish Trolove is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.