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QMRD3

Qualification Model Rover Demonstrator for Deep Drilling

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Qualification Model Rover Demonstrator for Deep Drilling or QMRD3, is a full size Curiosity / Mars 2020 Rover with a high percentage of 3d printed parts. The rover will serve as a testbed for the development of deep ice drilling technologies. The ultimate goal is to unlock access to liquid water under the Mars South Polar Ice Cap in the Planum Astrale regon of Mars.

This rover is a remix of Roger's Sawppy rover, which is a 1/4 scale rover that can be built for under $500.

This is the QMRD3 Rover (Qualification Model Rover Demonstrator for Deep Drilling). It is a 4x scale copy of the Sawppy rover designed by Roger. Due to the size difference, several changes (mainly relating to motors and power transmission) have been made and an entirely different motor strategy is required. You can find more about Roger's original Sawppy rover at https://hackaday.io/project/158208-sawppy-the-rover and https://github.com/Roger-random/Sawppy_Rover

This rover was born out of the necessity for a mobile testbed with flexible mounting options, but is turning into quite a project, both in the amount of work involved as well in the many ways that it represents the bleeding edge of home-workshop additive manufacturing capability. For example, each wheel weighs 5kg and takes 4 days to print (0.8mm nozzle, 0.4mm layer height, 1.2mm extrusion width, single wall and 10% infill), with a material cost of ~$100. A screenshot with the details of the wheel print is below. If you are inclined to build a rover like this, the wheel should be your deciding factor. It is by far the most expensive and largest printed component.

The Rover Chassis has reached Version 1.02 and all components have been prepared for the larger size. A Github repository for QMRD3, containing STLs as well as the Fusion360 archive is available here: https://github.com/Shootquinn/QMRD3

Also of note is the 22mm skateboard bearings used extensively on Roger's Sawppy rover have been replaced with 88mm 3D printed gear bearings. The bearings are licensed separately from the rest of the rover and the files can be found here: https://www.thingiverse.com/thing:3116838

The drive motors are from makermotor and are available at: https://makermotor.com/pn00113-6-6-rpm-gear-motor-12vdc-high-torque/ while the steering motors are from Amazon seller STEPPERONLINE and can be found by searching for the following listing: STEPPERONLINE 47:1 Planetary Gearbox Nema 23 Stepper Motor 2.8A. The mounting bracket for the stepper motor is required and will match up to the bolt pattern on the steering corners.

The Sawppy was designed with a $500 budget in mind, it appears that the budget moves linearly with the scale at this point, but the scrap costs from prototyping also do. If you want to build one of these I would plan on it costing around $5,000. Eventually the cost could be reduced to $2,000 from lessons learned, etc.

  • Front wheels on, Rocker Test

    Quinn Morley09/16/2019 at 02:00 0 comments

    The front wheels are on! I need to get all the wheels on and locked in the straight-ahead position because I will be using tank steering at first. I'm eventually going to modify Roger's Ackerman control method from Sawppy, but my motor strategy is different so it will take some time.

    Also with the rockers set up, before I mounted the wheels, I tested the articulation. In my opinion this needs some work and may be the weakest part of the whole contraption. We'll see how it works when everything is on the ground under it's own weight. 

    Here is another shot with the front wheels on:

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Quinn Morley wrote 09/18/2019 at 07:59 point

I have a backyard full of cars, I wish you brought this up sooner!

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Quinn Morley wrote 09/18/2019 at 08:04 point

How much torque, do you know? Moving these 20 inch wheels is no easy task. 

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Kyle Brinkerhoff wrote 09/18/2019 at 09:11 point

enough to break hands! 

they are worm drive so coasting is a no go, but that probably works out in your favor anyways. also the better ones like this come off of old american cars like buicks and pontiacs, the drive spline is huge and a gorilla glued 3d printed coupler adapts to the needed application, id recommend heat sinks too if your gonna run these for more than 30 min at a time, also try to find ones with metal bodies, they hold up better 

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Quinn Morley wrote 09/18/2019 at 17:36 point

I bought 6 of these rotisserie motors already, the torque is pretty insane. 21 Nm.

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