Designing & Building
After settling on the model, I scaled a schematic drawing to the size of the Backhoe I had built and determined that the tyres should be 95mm wide. The best candidates for these appeared to be Technic tyre 54120, which are 94mm wide.

 Having already built Eric Trax’s excellent Claas Telehandler, I had some idea of the challenges that lay ahead. In the process of building Eric’s model, I realised that the Technic servo motor could have an axle coming from either side, something that unbelievably, I had not noticed before. I felt that this would probably make it easier to build the steering mechanism.

I began building in September 2020. The first step was to figure out the rough dimensions of the model using the schematic. Once this was done, it seemed clear that the main issue with the chassis was going to be the drive train and the steering, both of which needed to be centrally located. Rather than start with a basic chassis framework and try to fit the motors into that, I decided to turn the servo motor on its side and built outwards from it. In the first few days of experimental building, I was able to lash together an ugly, basic chassis which would allow for the drive train to sit in the middle of the chassis, with the steering working around it. It wasn’t elegant, but I thought it might work. Having researched other Telehandler MOCs, I realised that many of them drove too fast, so I decided to add in some gear reduction in order to slow my model down a bit.

A few days into the build I realised that the steering was unlikely to work going around the drive motor and it would be better to do the opposite: keep the steering axle central and build the drive motor to the side. After several frustrating and unsuccessful attempts at putting this into action, I dismantled what I had built and started again. My second attempt was more successful, although a lot of experimentation was required with various sized gears to find a combination that worked well. At this point, I drew out an ariel view of the model on a large piece of paper and carried on working on top of this, using it as a guide for where I could place components like the S-bricks and the battery box.

After a couple of weeks of building, I began experimenting with fitting the battery. I realised that I would be able to fit it in very tight to the chassis if I swapped the location of the driving and steering motors. This meant that I needed to rebuild the chassis as a mirror image of itself. At this point I recreated what I had so far in Stud.io and then moved the motors to their new positions. This worked well, with the two motors and battery now built into a nice, compact chassis. By now I had been working on the model for about a month and was able to begin thinking about the placement of the linear actuator and the mounting point for the telescopic arm.

 Building the telescopic arm required a huge amount of experimentation and building/rebuilding. I created several versions of this using liftarms, all of which were far too big and cumbersome for the scale of the model. Eventually I completely scrapped what I had and decided to find a different approach.

My second attempt at a boom arm used curved panels for the main structure, which enabled me to build something a little slimmer, with the added benefit of being more aesthetically pleasing and more in keeping with the design of my backhoe. Finding a home for the extension motor was relatively simple, but the same could not be said for the motor that would tilt the forks. After several days of experimenting with building the motor at the fork end of the arm, I decided to change tack and instead build it onto the other end, inside the boom. This turned out to be an excellent solution and was far simpler and more elegant than my previous attempts had been. An added benefit of this design was that the cable routing became much simpler than it might otherwise have been.

After building some basic forks onto the end of the extension arm, I was initially at a loss as to how to tilt them: I had a powered axle running through the extension but wasn’t sure how to utilise it. Several experiments using worm gears were unsuccessful. Fortunately, there was building work going on outside my house, and for several days a JCB Telehandler was working just across the road. After studying the actual machine, I realised that the solution was going to be to use a small linear actuator to tilt the forks. This turned out to be remarkably simple to build into the model. Over the next few weeks, I repeatedly redesigned and rebuilt everything that I had done so far, and by mid-November I had a model that was fully functional, although quite ugly.

I spent much of November working on the cab of the vehicle. It took a long time for this part of the model to begin taking shape, and I tried many different approaches for the curved bars at the front. In the end, I settled on using flexible hose, with tubing over the top. I decided to use a sloped 11×5 panel to box in the battery, and my original intention was to build a cover section using curved panels. Whilst this seemed promising when I tried it, looking at the actual machine showed me that this wasn’t going to be quite right. I therefore redesigned the cover piece using curved bricks and cheese slopes on the top to mimic the engine vents. Fortunately, I was able to use those curved panels to tidy up the rear part of the vehicle.

 The final part of the build was the mudguards, and these proved very tricky to get right. I initially started with angled lift arms, and although the result looked good, they clashed with the chassis when steering. To better mimic the curve of the actual mudguards, I built a second version using no. 3 angled connectors. This allowed me to create the correct shape, although there was too much ‘detail’ on the top surface. However, in the absence of a better solution, this was the design that I stuck with.

 Over the next few months, the model was rebuilt many times and many further refinements were made. Quite often, once a model has been built, I leave it on my desk at work for a few days, so I can casually consider it, without really thinking too much about it. I tend to notice things that are bugging me this way.

 By June 2021 I had finished the model and had begun working on the instructions. I had received a lot of praise for my Backhoe instructions and was keen to repeat this success. I once again used a bag system for the build, which always makes the process more enjoyable. As with the Backhoe, the cable routing ended up being the most complicated part of the build, although I managed to find neat solutions to most of these problems.