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 were none available, free or for sale. Another scratch build project was hatching!
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.
Plans for this model are now available Here
More info on the scratch built RC crawler Crane with lattice boom are available at
The project was started in April 2009 and finished in November 2010, a long project that spent a lot of time on the back burner due to work commitments.