emergency sanding question

[brennerator]

Hey, my name is Daniel Brenner from team 1560. We will be participating in the Silicon Valley Regional tomorrow.

By pure accident, I was re-reading the rules, and found a new document for Robot Inspectors: http://www2.usfirst.org/2006comp/other/2006_Welcome_to_Robot_Inspection-rev_C.pdf

On page 6, it says that sandpaper is specifically not allowed. However, I've reread the normal robot rules (that teams are expected to read) and found no specific mention that sandpaper is not allowed. The problem is is that our coveyor belt is made of sandpaper. We've tested it, and it does not more than lightly scratch the surface of the balls-far from anything we ever considered as "damage." Now it's the night before the regional, and i was wondering if anybody had any interpretations of this rule or any suggestions for us? Do we have to replace the belt?

[The Lucas]

This is specifically answered in this Q&A (http://forums.usfirst.org/showthread.php?t=199)
can you use sanding belts to move balls within the robot at low speed; they would be used for traction, and any actual sanding would be purely incidental


It is reasonable to expect that sanding belts will damage the balls surfaces, even through incidental contact. As such, under the Parts Use Flowchart, sanding belts would not be permitted.


So I would bring a different material for your belt. Other teams may have good materials for you. Worst comes to worse you could turn the sand paper belt inside out. :D

[Rick TYler]

Daniel, I feel your pain. This has been discussed here early in the design season. My suggestion is not to panic, but be prepared if the inspector doesn't listen to reason (which is that the appropriate rule is "don't damage the balls" not "don't build your mechanism with this material"). If the inspectors complain, your backup solution is to turn the belts inside-out. They will almost certainly still work fine, but the inspector won't freak out about the abrasive surface.

If you are using really fine sandpaper (like 220 or finer) it is probably less abrasive than a lot of surfaces other teams are using. Try reasoning with the inspector. If you are using 32 grit -- I suppose you are on your own.

We did a lot of testing with well-worn 220-grit belts and they worked great and didn't damage the balls. It's just prejudice. Our final robot conveyor system replaced the sanding belts with timing belts (which weighed more and didn't work as well, IMO). Good luck.

[Rick TYler]

Originally Posted by GDC
It is reasonable to expect that sanding belts will damage the balls surfaces, even through incidental contact. As such, under the Parts Use Flowchart, sanding belts would not be permitted.

Urethane belts saw into belts. Plastic wheels tear chunks out. All wheels make small acceleration tears in the ball surface. Ramps that open and close pinch balls. Surgical tubing cuts balls. Anything running at high speed will damage the surface of Poof balls, but only sanding belts are singled out in the Q&A. This is one of the rare instances (IMO) of the Q&A folks not thinking through an answer thoroughly. Our first prototype launcher used two belt sanders with old 220-grit belts mounted five inches apart. The balls suffered much worse damage from our first rubber wheel prototype than from the sanders (which caused almost no visible problems).

[Amir]

Daniel,

We decided to use a sanding belt on our robot, however we coated it with a very thin layer of clear silicone 2 caulking. This effectively made it into a light-weight rubber belt. It grips better than the sand paper and will solve your problem. It will not add much weight and will dry in about 12 hours. You don't need to pass inspection to practice so you can wait for it to dry all day and then go to inspection and then use it the next day. You can use a large spackling knife to apply it. Apply it just thick enough to fill in the pores. We also used this on a custom flywheel that we machined. Very light and very effective. It does not tear the ball like a tire tread does and we exceeded 12 m/s until we geared the wheel differently. Hope this helps.

-Amir

Hey, my name is Daniel Brenner from team 1560. We will be participating in the Silicon Valley Regional tomorrow.

By pure accident, I was re-reading the rules, and found a new document for Robot Inspectors: http://www2.usfirst.org/2006comp/other/2006_Welcome_to_Robot_Inspection-rev_C.pdf

On page 6, it says that sandpaper is specifically not allowed. However, I've reread the normal robot rules (that teams are expected to read) and found no specific mention that sandpaper is not allowed. The problem is is that our coveyor belt is made of sandpaper. We've tested it, and it does not more than lightly scratch the surface of the balls-far from anything we ever considered as "damage." Now it's the night before the regional, and i was wondering if anybody had any interpretations of this rule or any suggestions for us? Do we have to replace the belt?

[brennerator]

Thanks for the help. We ended up taking the precautions you suggested but our 320 grit sandpaper thankfully passed inspection.

[evolution]

Anyone else have ball handling materials that have been in question, or called illegal during inspection?