Bruder CAT 320 excavator RC conversion

[SteinHDan]

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2688.jpg

This is a great model from Bruder and of course I had to give it a try when my son asked me if we could make it RC.

Goals of this project:
1. Minimize work :-)
2. Have a fully functional model (but it doesn't need to be very strong)
3. Great sound


Taking the model apart:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2689.jpg


Cut off the drive wheel axles. Expand the axle hole up to 6mm.

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2690.jpg


3D-print a hub that sits in the old wheel. A steel rigid flange coupling (6mm axle, M3 holes) is screwed to the hub with four M3x15mm self-tapping screws. The motors are 12V 62RPM worm gear motors.

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2691.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2692.jpg


Fixing the hub in the wheel by drilling two small holes, one from each side, into the wheel and hub and using two small self-tapping screws M2x7mm:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2693.jpg


Cut away some plastic to make room for the motors:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2695.jpg

Make sure they fit snuggly:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2696.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2697.jpg


3D printed a template to guide where the motor mount holes should be (3mm):

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2708.jpg


Carve out the inside of the motor mounts to give room for the steel coupling. Drill a small hole from the underside to be able to reach the set screw in the coupling when it has been inserted into its position:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2719.jpg


Attach the motors with two M3x6 bolts on each side:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2721.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2723.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2724.jpg


3D print motor covers for the motors and attach with two self-tapping screws:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2726.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2727.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2728.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2730.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2731.jpg


Re-add the tracks:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2735.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2736.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2737.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2740.jpg

[SteinHDan]

I tried to make the swing mechanism as simple as possible. It's currently made up of one worm gear motor (20rpm, 12v, 6mm axle), a steel rigid flange coupling (6mm axle, M3 holes). The motor and the coupling is the same type as used for the wheels, except that the RPM is 20 for this motor.

The motor drives a 40mm long 6mm diameter steel axle through a 6mm coupling. The axle has one flat side grinded 1mm down. A hole-type slip ring (7mm hole, 6 wires) is put on the axle and allows the unlimited turning of the excavator house on the undercarriage:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2749.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2752.jpg


Drill a hole in the bottom center and expand it to 10mm. Use the flange coupling as a template to drill the small holes:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2754.jpg


Remove plastic to make the floor inside flat:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2753.jpg


Attach the flange coupling to the axle with the two set screws:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2755.jpg


Insert the axle and coupling from the bottom:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2756.jpg


Attach with four M3x8mm screws and locking nuts:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2757.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2758.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2760.jpg


Add the slip ring. In the undercarriage I made Dupont connectors on both the motors (male) and the slip ring (female):

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2761.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2764.jpg


3D print a template to drill the holes in the house floor:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2770.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2771.jpg

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2772.jpg


3D print a 6mm spacer to get the motor in position at the right height:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2773.jpg


Fix in place with four M3x10mm bolts:

http://d1t2tbzmskak12.cloudfront.net/bruder-cat320-excavator/IMAG2775.jpg

[Zabco]

Very nice work. Really like the use of the 3D templates. Are you going to use hydraulics or actuators for boom movement?

[SteinHDan]

I will be using Actuonix linear actuators for the boom on this build, trying to keep it all kid & indoor friendly (e.g. no oil, over-discharge prevention, auto shutoff of remote, etc). So it won't be strong, but maybe be able to dig some loose dirt.


Stein :-)

[Lil Giants]

You make it look easy Stein, good job :cool:

Use of pet food would be better than for in the house.

[skeeter]

Awesome work, my friend!

[Wombii]

Nice work. Will you be using your Raspberry Pi system for remote control?

[SteinHDan]

Nice work. Will you be using your Raspberry Pi system for remote control?

Initially. yes, but this build can be controlled easily by most any system, since you just need six motor controllers that can do forward and reverse. (bucket, stick, boom, turn, left track and right track).

I'm using the Raspberry first, but I'm thinking about changing it to an Arduino setup. The kids don't like the 15 second boot time of the Raspberry..

You could also just use a normal six-channel RC radio and receiver together with six motor controllers, like three of these double ones:
- 3 x Sabertooth 2x5 R/C (https://www.dimensionengineering.com/products/sabertooth2x5rc)


Stein :-)

[SteinHDan]

Thanks, Joe and Skeeter! :-)


Stein :-)