Hello everyone, lots of expertise here. I’m working with the San Diego Mars Society chapter that does lots of local outreach/education events with kids, including having them drive a “Mars rover” around, either viewing it directly or via an on-board TV camera.
We need a new rover - various RC car chassis have been used, and our Vexplorer didn’t last long (plastic drive gears stripped in each case), so we’re looking for an RC rover with front gripper as a more robust replacement.
**My question is: Although the A4WD1 v2 kit would work just fine, could we instead take the same control electronics+transmitter and use them with one of the 6WD Sumo bots (e.g. Predator chassis)?
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Possible advantages of the 6WD Sumo would be:
slower speeds (17.5"/sec) with more torque for obstacles/slopes. The A4WD1 rover travels twice as fast, which is a problem when dealing with over-enthusiastic kids.
more “Martian” look with 6 wheels instead of 4.
greater carrying capacity? (We’ll be adding a fixed pylon for the mini TV camera, and eventually some fake solar panels and superstructure)
better traction on smooth surfaces?
Possible disadvantages of the 6WD Sumo chassis - your expert advice on this gratefully accepted:
much lower ground clearance (how much lower? Will it run on grass?)
more difficulty turning on the spot? (Should the center wheels be “omni”?)
would have to fabricate custom front mount for A4WD1 gripper?
any others?
We have a grant with a max. of about $1000 to spend including all accessories, AND we’re not robot hobbyists, so autonomous operation, odometry, articulated robot arms (too complex for kids to operate anyway) are all out of the question for now.
If you go to flickr and do an image search on “mars society san diego rover” you’ll see what we’re using these for.
I’d pass on the sumo chassis as the design is not really relevant to what would be expected of a Mars rover. You might also consider incorporating web control of the rover. It would better simulate operating a rover on Mars and allow science classes/groups that have internet access to remotely operate the rover.
The ground clearance on the sumo is probably the biggest problem. It’s very little… The A4wd1 speed listed is with the 30:1 motors. You can request the rover with 50:1 motors for almost half the speed and double the torque. Hope this helps.
Thanks for the fast replies - sounds like the A4WD1 with 50:1 motors is the way to go.
We hadn’t thought of web control but it does open up some possibilities, e.g. programming in a 1.3-second delay on commands and TV picture to simulate a lunar rover, as well as throwing in some intentional communications glitches (“solar storm”). That may have to wait for a future rover.
For the most part the kids will be using direct radio control - one joystick for motion, the other for the gripper. That’s challenge enough for them, especially with only a TV image for guidance.
Out of interest though, what additional components would be required for web control, while still preserving handheld function?
One way to do this would be to “replace” the handheld remote with a computer-controlled version of the RF transmitter, with a GUI for the joystick commands and some software to allow for time delays, speed limits etc. Nothing on-board the rover would have to change. Has such a setup been done before?
(Desperately trying not go get sucked in to a really cool hobby…!).
Web control brings in realistic issues for which advanced students could develop solutions (maybe a little competition between groups). I don’t know much about RC equipment so my ideas would be pretty lame. Maybe you could give more detail on the joysticks on the remote control (does each stick have up/down and left/right?). Servos might be used to operate the joysticks, or pots that could be added to the transmitter. Another option might be to make an ssc-32/bluetooth setup which could be put on the rover when desired by unplugging the RC receiver from the servos and plugging the servos into the ssc-32. lots of possibilitys. With the ssc-32, one could receive telemetry from sensors on the rover. The ultimate would be to add a netpad to the rover for remote control. Below is a simple setup where you remotely operate servos over the internet thru a servo controller (is it my place or Mars, hmmm…).
Thanks for the feedback. In fact, hunting around this forum under “computer remote control” post on this forum I came across the PCTx
Assuming that the Hitec Laser 6 (which comes with the A3WD1 kit) is compatible and has an input (presumably the same as the training mode “master” input), the PCTx cable and software will allow us to use a laptop to command the same transmitter. Much more elegant but the same effect as using servos to push the joysticks (if it works, that is!).
Writing the software to introduce time delays, speed limits, and solar storm “command blackouts” would be an easy student project. And if the rover gets out of control, unplugging the PCTx from the handheld should be quick and easy.
The rover will be visiting local schools for at most 1/2 day each - we reach a lot of kids that way, and generate a lot of questions, but no time for the kids to work on the rover.
