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Unread 19-02-2004, 22:28
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Vince Vince is offline
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FRC #0236 (Techno Ticks)
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Re: Drill Motor + Gearbox + Breaker Problems

There may not be a single solution here, but rather a combination of factors. Many of these have been mentioned and I'll add a few ideas.

1. The drill motors (even in low) with the supplied gears and the 12 inch wheels are not a combination suited for motor effeciency and non-tripping action. Having said that, you can still use them, but you must be very careful (as you are seeing).

2. Even when EVRYTHING is corrected, you probably do not want to drive this combination more than 1/2 power. The good news is that even at 1/2 power (easy software fix, with a button to over ride in an emergency) you will move around the field quite fast.

3. From your photos, it appears there is lots of metal / plastic "dust" on the gearbox housings - something is wearing that shouldn't be. You need to find that and fix it (especially on the right side).

4. It is hard to tell from the photos, but are you using 6 Bearings on each side? The resolution gives when zooming, but it looks like some bearings might not be used in your gearbox.

5. Be careful that you do not contort the plastic gearbox mounts when tightening things down. These plastic mounts are designed to fit over the 2x4 AL beam in the kit - they have small cut outs to fit. If you tighten up on the mounts too much, you can distort the mount (i.e. cause misalignment) AND press the bearings against the frame. Also I'd use Nylock nuts to avoid having things work free (and leading to more alignment issues).

6. Again, it is hard to tell from the photo, but it looks like the left outside gear box is bowed out. If so, a likely cause is a spacer that is a bit too large (and associated misalignment).

7. You have to be VERY careful with the key on the gears. If it is a bit too long, it will work its way under the spacer, leading to additional unwanted wear. You have to be very careful that thess keys are EXACTLY the correct length.

8. The 3 spacers used to center the large gear can lead to unwanted problems. Better to use a single spacer of the correct length.

9. Your motors are having a difficult time dumping the heat they build up. Can you provide some air route from above the motors? As mentioned earlier, fans would help as well. You also might want to add some cooling fins to the motor case (be careful not to cover any existing air holes on the case). Finally, the plastic mounting frames act as a good electrical and thermal insulator. If there is a way you could use your robot frame as a heat sink (i.e. some good hunks of metal between your motors and the extruded AL) you can pull off some of the built up heat. Again - this is patch to a more fundamental problem (i.e. this combination not being efficient).

10. When your system is running, be very cautious of the motor temperatures. With this combination of systems you cannot run the design for long periods without giving the motors a chance to cool down. Stop every 2 minutes of use (the time of a match) and check the motors - if you can't hold a finger to the case for x seconds - stop ( the larger the x you set the better off you will be). You must pay attention to this, or even worse things start to happen (things that don't reset with time).

11. Your design has the motors / gearbox mounted such that they are "out of sight - out of mind" - no problem with their location, but don't adopt that thought process. The drive motors / gears are the most important part of your robot. Even though they are hard to see in your design, spend time (regularly and often) inspecting them to detect problems that might be starting but are not yet critical.

Again, there are many layers to the situation at hand. If you are still having problem, take up some of the other local teams for help as soon as you can.

For the problems you are experiencing, you might say "am there - am doing that" with regards to some of my comments (see the link....)

Feel free to email me if you are still running into problems - Vince"am there... am doing that....."