- Technic MOC
- Started May 2015
- Completed June 2015 (for now)
- ??? parts.
Foreword: this is in fact a first prototype, suffering from a few flaws. But it's a good starting point for a future (and better) model.
I wanted to build this tractor since Top Gear UK episode on tractors back in 2007 (episode 5 of Series 9), where Hammond brought one on the show. It's a massive 25t Tractor with four tracks instead of wheels and an articulated chassis. It's used to drag very heavy or large agricultural machninery in fields.
The scale of the MOC is derivated from the size of the tracks. It's somewhere between 1:21 and 1:22. This makes it large enough to be motorized but not too large, thus not overweight.
It uses an XL motor for propulsion (4 tracks, 2 differentials), with a 3/7 reduction (3/5 and 5/7). This gives it a nice speed. A fake engine is linked to propulsion via a rubber band.
Steering is achieved with a servo and a steering mechanism similar to the one found on #42030, which is very robust.
Regarding the design, I've made some compromises in order to get the best result possible with the existing Lego parts. I've used panels to close as many gaps as possible, using liftarms only when panels wouldn't fit. The cab isn't finished, I just built the basic shape.
Here is a short video showing the MOC's capabilities on gravel.
After a few tests, there are several things that will be changed in the next version:
- The fake engine will be properly integrated (it wasn't planned at the beginning, and took the place of the BB that couldn't fit at the front),
- The IR receptor will be much better integrated,
- The turning radius will be lowered a bit,
- I like the speed, so that shouldn't change much,
- The tracks will be rebuilt. I wanted to be as realistic as possible. Unfortunately, putting those 3 small wheels makes axles pop out at the back and they catch in the track when reversing (very noticeable on the video). The best way to correct this is to put only two small wheels with 1.5L pins.
- The way the tracks are attached to the chassis will be strengthened,
- I have to study tractors a bit more and add some trailer hook, and eventually, build a trailer.