[TC29] Mini Excavator

[2GodBDGlory]

After deciding to enter this contest, I went through a few different model ideas before settling on some kind of excavator. Now, there's been a fair bit of discussion lately about how the latest Volvo excavator set has failed to advance on the legacy of 8043, so this seemed like a good opportunity to see how that classic set could be improved, while retaining its basic spirit. Coincidentally, the contest motor limit of 4 corresponds with the motor count of the original set, so a similar gearbox approach will be needed to create an RC model!

Now, in order for my model to actually advance on 8043, it can't just have one motor for shifting between two modes, for six motorized functions. No! It must have at least three different modes, for nine motorized functions! However, that means that I need more things to actually motorize, which brought me to the Mini Excavator topic. My model is certainly not going to be "mini," but it will be a model of a real-world "Mini Excavator" I've worked around these cool little machines on a few occasions, and have always thought they'd make a good Technic model, on account of their extra functions, which typically include an adjustable blade on the base, a claw for the bucket, and a rotatable arm. I don't have enough motorized functions to do the rotatable arm, so I'll gladly leave it out to avoid the absolute nightmare of trying to route all the driveshafts for the arm through both vertical and transverse pivots! So, the functions will hopefully be as follows:

Motorized:

1x Servo motor for switching between three modes.

3x other motors for running three functions per mode

Functions:

Mode 1: Drive track 1; Drive track 2; rotate superstructure

Mode 2: Lift arm; bend arm; operate bucket

Mode 3: Operate blade; operate claw; tool change/PTO

To expand on a couple of those. Operating the blade is a challenge, because I've already got two functions going through the turntable for drive. What I'm hoping to do to get around that is to use vertical motion of the inner drive axle (going through the turntable) to operate the blade. It's got a sliding 8T gear on the bottom, and will be able to slide through a gear on the top as well, which should allow some other method pushing down on the axle to push down the blade (A rubber band will have to work to lift it up). It sounds complicated, but should be interesting to try to make work.

I'd like to have a tool change function to match the Volvo excavator set, and I think having a PTO for some other attachments would be nice. To fit that within my function limit, I'm hoping that I can use one motor for both, that will run the PTO while slipping a clutch on the tool change function. We'll see if that works or not.

Anyways, most of that is far in the future, but this is what I've got so far!

It's always fun when a 40T gear turns out to be needed!

Note the small linear actuators being used for manual track tension adjustment. It seemed like a fun function to include, and I had room for it!

I realize that this is an ambitious model, and I'm in very early stages, but hopefully it comes together according to plan!

I just finished college for the year, and I have yet to find summer work, so for the next while, I do have a disturbing amount of time on my hands to build Lego!

[Jurss]

Since when this is mini?

[Aurorasaurus]

27 minutes ago, Jurss said:

Since when this is mini?

7 hours ago, 2GodBDGlory said:

My model is certainly not going to be "mini," but it will be a model of a real-world "Mini Excavator"