I have been working alongside crawler cranes for many years and I thought building a scale model of one would be an interesting project.
To keep things a reasonable size I decided that a model in the region of 1/20th scale was the ideal size for budget and available materials.
I searched the web for Crawler Crane Plans and it did not surprise me that there where none available, free or for sale. Another scratch build project. I found the full size crane that I would use for the dimensions and started measuring.
After many measurements and calculations I changed the scale to 1/21st Scale - not standard but this scale enabled the main struts of the lattice boom to be 3mm, and I just happened to have 3mm brazing rods so the decision was made.
The Radio Control model has two servos controlled by a small FM receiver
servo No.1 lowers and raises the boom through a 6:1 pulley system (the full size crane uses a 12:1 ratio)
servo No.2 Lowers and raises the hook block via a 4:1 pulley system as in the full size crane
The slew and tracks are not powered due to the small scale of the model but are made to replicate the full range of movement.
The model is surprisingly strong and easily lifts more weight than it takes to overbalance her. The servos used are just the standard Futaba 9003 bottom of the range proportional servos modified to rotate (this makes a fully controllable RC winch)
The lattice boom is painstakingly soldered together from brazing rod. The difficult part is keeping the completed struts cool while soldering on the connecting pieces, you will get the hang of it but it can be frustrating to start with.
The photographs above have been taken alongside the real Ishiko 40T Crawler Crane that the measurements where taken from.
Plans for this model are now available Here
Updated 11 May 2013
Model Crane Plans to build a working model Crane
19 Pages in PDF Format that is 700KB in Size - Click Here to download the free Crane Plans
16 Pages in PDF Format - Plans to build a working Live Steam Crane Model, File size is 400KB
Click here to download the Steam Crane Plans and Instructions