Building the Rover
Assembly Steps Required
1. Read the Mechatronics webpage for the Rover, at least 3 times to fully understand the scope of the project.
2. Download the STLs and start printing the functional parts. Note: the STLs were originally provided for free when I started my project, but now there is a small charge for them from Cults 3D website. See Mechatronics webpage. Because the STLs are Mechatronics intellectual property I will not provide any here.
3. Order the materials that you need. Mechatronics provides sources for all the major parts so you can get the exact parts required. This is important because the parts you buy MUST fit into the parts you print, unless of course, you are adept at modifying or creating 3D files.
5. Build the frame.
6. Assemble the tubes for the wheels. The tubes may not fit inside the holes of the plastic parts, due to shrinkage. You can compensate for that in Cura (refer to Mechatronics), or try to grind and sand out the part so the tube fits.
7. Make 2 complete wheel assemblies, one for the left side and one for the right side. Check the alignment of the wheels. (You probably won't have wheels yet, since they take a long time to print, so use the motor assemblies for reference). They should like the image below
8. Install the servos. Leave the DC wheel motors out until later because they are heavy. Put these aside.
9. Print the side and top panels so you can install them without the wheels being in the way. Leave the top pieces off so you can do the electronics inside the belly of the Rover.
10. Install the wheel assemblies, including the differential bar and rocker joints. See "notes on printing", below.
11. When the wheels are printed and installed, you can let it stand on its own, a good test for the integrity of the parts. For performing all the other actions, it's best to support the Rover body high enough to take the pressure off the wheels.
12. Install the electronics. You will need the PCB made by Mechatronic or you can build your own. The Mechatronics is very nicely designed and very compact. I obtained my boards from JLCPCB.com using the Gerber files supplied by Mechatronics. Populate the board as required. No schematic is provided but the block diagram has most of the information required. I drew a schematic for my Rover. See above menu bar for the link to the Electronics page.
13. Wire the external components: 4 servos and 6 motors. The camera has a stepper motor and one servo to wire as well, so make allowances for that. Use zip-ties (tie-wraps) to run the wiring so it's not visible on the Rover side of the tubes. The wheels have to turn maybe 15 deg either way, so allow slack for the motor wiring.
14. Finish off the electronics bay by installing the batteries, the Mega with I/O board shield, any voltage or buck converters, on-off switch, and relays if used. (The camera needs 12 volts at about 300 mA, so I route the power through a relay rather than having it come from the Mega which could not provide that current.)
14. Test your Flysky R/C control to make sure it works with the receiver. I tested my receiver with other (off-board) servos first, then used iBus through the Mega to test the ones steering the Rover, and then the motors.
15. There once was a 3D blowup at Thangs.com for the Rover, allowing you to see how the parts fit together. I used this quite a lot to know where to install and how to orient the parts. It is no longer available.
Thursday, December 21, 2023
1. Read the Mechatronics webpage for the Rover, at least 3 times to fully understand the scope of the project.
2. Download the STLs and start printing the functional parts. Note: the STLs were originally provided for free when I started my project, but now there is a small charge for them from Cults 3D website. See Mechatronics webpage. Because the STLs are Mechatronics intellectual property I will not provide any here.
3. Order the materials that you need. Mechatronics provides sources for all the major parts so you can get the exact parts required. This is important because the parts you buy MUST fit into the parts you print, unless of course, you are adept at modifying or creating 3D files.
5. Build the frame.
6. Assemble the tubes for the wheels. The tubes may not fit inside the holes of the plastic parts, due to shrinkage. You can compensate for that in Cura (refer to Mechatronics), or try to grind and sand out the part so the tube fits.
7. Make 2 complete wheel assemblies, one for the left side and one for the right side. Check the alignment of the wheels. (You probably won't have wheels yet, since they take a long time to print, so use the motor assemblies for reference). They should like the image below
8. Install the servos. Leave the DC wheel motors out until later because they are heavy. Put these aside.
9. Print the side and top panels so you can install them without the wheels being in the way. Leave the top pieces off so you can do the electronics inside the belly of the Rover.
10. Install the wheel assemblies, including the differential bar and rocker joints. See "notes on printing", below.
11. When the wheels are printed and installed, you can let it stand on its own, a good test for the integrity of the parts. For performing all the other actions, it's best to support the Rover body high enough to take the pressure off the wheels.
12. Install the electronics. You will need the PCB made by Mechatronic or you can build your own. The Mechatronics is very nicely designed and very compact. I obtained my boards from JLCPCB.com using the Gerber files supplied by Mechatronics. Populate the board as required. No schematic is provided but the block diagram has most of the information required. I drew a schematic for my Rover. See above menu bar for the link to the Electronics page.
13. Wire the external components: 4 servos and 6 motors. The camera has a stepper motor and one servo to wire as well, so make allowances for that. Use zip-ties (tie-wraps) to run the wiring so it's not visible on the Rover side of the tubes. The wheels have to turn maybe 15 deg either way, so allow slack for the motor wiring.
14. Finish off the electronics bay by installing the batteries, the Mega with I/O board shield, any voltage or buck converters, on-off switch, and relays if used. (The camera needs 12 volts at about 300 mA, so I route the power through a relay rather than having it come from the Mega which could not provide that current.)
14. Test your Flysky R/C control to make sure it works with the receiver. I tested my receiver with other (off-board) servos first, then used iBus through the Mega to test the ones steering the Rover, and then the motors.
15. There once was a 3D blowup at Thangs.com for the Rover, allowing you to see how the parts fit together. I used this quite a lot to know where to install and how to orient the parts. It is no longer available.
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Notes on Printing
2. Parts that do not bear weight or stress, i.e. all the NON-moving parts, can be printed with infills from 15% to 50%, but the motive parts, blue on my model, should be printed 100% infill, in other words, SOLID. The parts will be quite a bit heavier but they will have the strength they need to prevent breakage. Solid parts take screws and screw inserts better as well.
3. I used generic PLA at 200 deg C. for the nozzle and 60 deg C. for the bed. PLA was used for all parts except the tire treads which use TPU filament which is flexible like rubber.
4. Mechatronics organized the STL files into 3 categories: Functional, Non-functional and Camera. As noted, print all the functional parts first so the legs and wheels can be built and attached. Put the side panels on before installing the legs and wheels, for easy access to the screws, and leave the top 4 panels OFF so you can do the electronics.
5. The RTG (yellow thing in the photo gallery) can be printed last, along with the "decorative" parts that had specific functions on the real Rover. The RTG takes 24 + hours to print, so I cut it in quarters using Meshmixer and then glued the 4 pieces together.
6. Print the camera parts and assemble the camera but don't install it because it will be in your way for other work. This gets installed LAST after all the electronics and other printing is complete.
7. Test fit everything. Remove the supports if any, being careful not to break the part. (I did so numerous times!). Drill out the holes. The 3mm holes that are "printed" come out to about 2.9 mm and will NOT take a M3 screw. Same for other holes.
8. I used skirts, brims and rafts for various pieces. For the rims that were printed with spokes down, I used a raft which I removed later. You must have good adhesion. For flat pieces, like panels, I didn't use anything at all and just printed it the easiest way.
9. You must keep track of what you printed. I created a spreadsheet and numbered each item, and then I toner-printed screenprints of each part and numbered them. See the photos below.
10. When you break parts (and you will) you can fix them with Testor glue meant for model car making. It's the one in the red and white tube.
Thursday, December 21, 2023
1. The "rims" take a long, long time to print, about 9-12 hours for each one. I made 5-6 misprints before I realized the ONLY way to print them was with the spokes down on the print surface. If you try to print "logically", with the spokes facing up, the print head will hit a spoke and break it, and the printer will not be able to recover. Once I printed spokes down each rim printed properly. It wouldn't hurt to make them solid. The spokes are weak, so watch how you handle them.2. Parts that do not bear weight or stress, i.e. all the NON-moving parts, can be printed with infills from 15% to 50%, but the motive parts, blue on my model, should be printed 100% infill, in other words, SOLID. The parts will be quite a bit heavier but they will have the strength they need to prevent breakage. Solid parts take screws and screw inserts better as well.
3. I used generic PLA at 200 deg C. for the nozzle and 60 deg C. for the bed. PLA was used for all parts except the tire treads which use TPU filament which is flexible like rubber.
4. Mechatronics organized the STL files into 3 categories: Functional, Non-functional and Camera. As noted, print all the functional parts first so the legs and wheels can be built and attached. Put the side panels on before installing the legs and wheels, for easy access to the screws, and leave the top 4 panels OFF so you can do the electronics.
5. The RTG (yellow thing in the photo gallery) can be printed last, along with the "decorative" parts that had specific functions on the real Rover. The RTG takes 24 + hours to print, so I cut it in quarters using Meshmixer and then glued the 4 pieces together.
6. Print the camera parts and assemble the camera but don't install it because it will be in your way for other work. This gets installed LAST after all the electronics and other printing is complete.
7. Test fit everything. Remove the supports if any, being careful not to break the part. (I did so numerous times!). Drill out the holes. The 3mm holes that are "printed" come out to about 2.9 mm and will NOT take a M3 screw. Same for other holes.
8. I used skirts, brims and rafts for various pieces. For the rims that were printed with spokes down, I used a raft which I removed later. You must have good adhesion. For flat pieces, like panels, I didn't use anything at all and just printed it the easiest way.
9. You must keep track of what you printed. I created a spreadsheet and numbered each item, and then I toner-printed screenprints of each part and numbered them. See the photos below.
10. When you break parts (and you will) you can fix them with Testor glue meant for model car making. It's the one in the red and white tube.
Motive Parts
2. None of the bearings would fit because of shrinking plastic as it cooled but I found an excellent way to get them into place without sanding and grinding the holes bigger. I heat the "hole" with a heat gun to soften up the area, then press the bearing into place. When the part cools, the bearing is held tightly in place.
3. Mechatronics mentions screw inserts but not how to use them or even where to put them, but after looking at some of the parts that had holes too big for an M3 screw, I realized this is where they go. I heated them with a soldering iron as shown in one of the photos below. About 5 seconds is all that is needed to heat this little brass inserts, at 375C soldering temperature.
4. The wheel coupler is a weak part because, even with the screw inserts, one cannot tighten the screw enough onto the motor shaft to keep it from turning. Not only that but screwing a grub screw into the insert causes it to come out the more you screw the part in to get it tight. I fixed that problem by putting a hose clamp around it, pushing the grub screws and inserts back towards the motor shaft. This was not the ideal solution and it didn't work as well as expected. A new approach fixed the problem. Go to Wheels page, a page devoted just to this issue.
What is needed is a coupler made of metal. I could not find 30mm diameter metal couplers, so I will have to make some on my lathe. The hose clamp will work for now.
Monday, December 25, 2023
1. The motive parts are the ones that support the wheels and servos and...move! They are under some stress, supporting the entire robot body.2. None of the bearings would fit because of shrinking plastic as it cooled but I found an excellent way to get them into place without sanding and grinding the holes bigger. I heat the "hole" with a heat gun to soften up the area, then press the bearing into place. When the part cools, the bearing is held tightly in place.
3. Mechatronics mentions screw inserts but not how to use them or even where to put them, but after looking at some of the parts that had holes too big for an M3 screw, I realized this is where they go. I heated them with a soldering iron as shown in one of the photos below. About 5 seconds is all that is needed to heat this little brass inserts, at 375C soldering temperature.
4. The wheel coupler is a weak part because, even with the screw inserts, one cannot tighten the screw enough onto the motor shaft to keep it from turning. Not only that but screwing a grub screw into the insert causes it to come out the more you screw the part in to get it tight. I fixed that problem by putting a hose clamp around it, pushing the grub screws and inserts back towards the motor shaft. This was not the ideal solution and it didn't work as well as expected. A new approach fixed the problem. Go to Wheels page, a page devoted just to this issue.
What is needed is a coupler made of metal. I could not find 30mm diameter metal couplers, so I will have to make some on my lathe. The hose clamp will work for now.
The image below is two of the most difficult parts to deal with and not surprisingly the most critical. There are two sets here, 2 parts each, screwed together with the hex M4 screws. The very top of the rocker joint contains a bearing but the area around it is very thin. I broke one or two just removing the supports in the hole!! Refer to the Mechatronics diagrams to see where these parts fit.
The image below is a 3D viewer screen-print image of the rocker joint. The hole in the middle takes an M8 bolt that feeds from the inside of the rocker joint base (photo #4 in the gallery), into the rectangular chamber at the top. That's where an M8 nut has to sit to hold the two parts together. Well, the chamber is too small, at least for the nuts I had so I had to hollow it out with a Dremel. (A competent 3D artist could have modified the part). The nut fits quite a distance down, obviously centered around the nut, so you can't heat the nut or the plastic to get the nut in place. Either you carve out a space or find a nut that fits.
Here are some tips for those contemplating building their own Rover
Here's a sample of the spreadsheet I created to make sure all the parts were printed and no duplicates were made. I printed in what some slicers call "draft" quality, or 0.2mm because printing at 0.1 mm (fine quality) would have taken an extra month! The time shown is what my slicer reported, but it depends alot on the orientation of the object, infill, and of course the quality required. The quantities of each may have changed. It was not immediately obvious how many of each was required (except for wheels and servo mounts). As construction continued, it became obvious some parts were not "singles" and I would need more copies. When parts broke, I would reprint it solid rather than with infill.
These are the dimensions of the Rover model
Use this sketch to get the correct wheel orientation. Front is at bottom. I got the rocker joints mixed up (left side/right side) and wheels were splayed out like Wile.E Coyote in Roadrunner cartoons!
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