Chief Delphi - pic: 3729's minibot

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Extra Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=68)

- - pic: 3729's minibot (http://www.chiefdelphi.com/forums/showthread.php?t=93500)

Re: pic: 3729's minibot

How exactly are you mounting your magnets?

Re: pic: 3729's minibot

Two magnets each directly opposite each other sandwitching the 1/16 inch Lexan between them. Polycarbonate glue is used to keep them in position. This puts one surface of the magnet about 1/16 inch above the surface of the pole.

Re: pic: 3729's minibot

Are lamp switches legal? The rules say only "2 common household lightswitches"

Re: pic: 3729's minibot

Quote:

Originally Posted by PingPongPerson (Post 1039021)

Are lamp switches legal? The rules say only "2 common household lightswitches"

Yes, if they are sold as a "light switch" for household use. Read Team Update 12 for the full interpretation.

Re: pic: 3729's minibot

Are lamp switches legal?

Re: pic: 3729's minibot

From TU #12

A note about “light switches” permitted on the MINIBOT:
We have previously stated in the Q&A that “light switches” are only “light switches” if they are commonly used in a wall mounting box. Rule R92-N, however, uses the language “common household light switches”; which can have a much broader interpretation. Given the discrepancy in specificity between R92 and the Q&A statements, we defer to the manual. Therefore, “light switches” permitted on the MINIBOT are not confined to those used in wall mounting boxes; anything sold as a “light switch” for household use is allowed. The Q&A answers will be revised.

Lamp switch = light switch and yes you can buy them at Home Depot with the rest of the "light switches"

Re: pic: 3729's minibot

Be careful about aluminum rod pressed onto the motor shaft unless you are using a very strong grade of aluminum. We used 6061 at first and it was a miserable failure. We ended up with 1/4-20 steel bolts as shafts and it works great.

Re: pic: 3729's minibot

Thanks. Sorry I asked twice I didn't think it posted the first time.

Re: pic: 3729's minibot

How did you attach the bolts to the motor shaft?

Re: pic: 3729's minibot

By drilling a hole in the center of the bolt that is an interference fit and carefully pressing the motur shaft into it

Re: pic: 3729's minibot

Quote:

Originally Posted by NOV8R (Post 1038428)

A few answers: The shafts are 2 inch long by 3/8 inch aluminum rod drilled with a 3/32 drill. They are then pressed on with an arbor press. The friction material is 3/8 inch OD Latex stretched on after running hot water over it for a few seconds. The white object just below the motors is a pole guide made from a 1 1/2 pvc pipe fitting. In addittion two magnets help hold the minibot to the pole. The battery is held in position between two pieces of 1/2 aluminum tubing. Inside this tubing are guide pins attached to the deployment tray. There are two on/off lamp switches and one limit switch that control the motors. The first switch turns on the motors when the bot contacts the pole. When the second switch contacts the top of the tower it shifts the motor to half power so the bot will slowly decend the pole. A limit switch on the bot's base then turns off power when it comes down the pole and makes contact with the base. Weight management of the minibot is essential. Let the bot get to heavy and you'll smoke the motors.

How do you get the switches to change the motors to half power?

Re: pic: 3729's minibot

We used a light switch to hook a 4 ohm resistor in series with the motors. Since all the recent problems with switches and getting them thru inspection we're using the KoP limit switches to short the motors to decend. It's working great.

Re: pic: 3729's minibot

Quote:

Originally Posted by NOV8R (Post 1046642)

We used a light switch to hook a 4 ohm resistor in series with the motors.

Resistors aren't allowed on the minibot, by the way.

Re: pic: 3729's minibot

Thanks for the answers!

1 last question, how do you secure the surgical tubing to the motor shaft? We were able to get it on, but it keeps sliding off. Thanks!

Re: pic: 3729's minibot

Quote:

Originally Posted by Free Willy (Post 1047659)

Thanks for the answers!

1 last question, how do you secure the surgical tubing to the motor shaft? We were able to get it on, but it keeps sliding off. Thanks!

It will stay on if:
1. You have enough contact area (>1" has worked for me)
2. The ID of the tubing is the same, or smaller than the OD of the shaft

Chances are it will take some finger strength to get the surgical tubing on without a lubricant. Its what I have been doing for weeks.
Some teams have said they use warm water or rubbing alcohol. For whatever reason we can't get warm water in our building so I haven't been able to try it.

Now that you know, can you explain why the tubing behaves this way?