Re: Al's Annual Inspection Thread
 

I'm sure there's some non-zero probability of an inspector who's never missed anything (clearly NOT me), but the number is so small as to be not worth calculating. We're all human and there's a lot to look for. In my brief (2-year) inspecting career I've seen, among other things, these items that had passed a previous inspection:
* Illegally-supported bumpers last year that passed at least three inspections
* A robot without a pressure relief valve. It wasn't that the valve was in the wrong place -- it wasn't installed, and the students didn't know what it was for when we found it in their parts box.
* A manual vent plug valve that was accessed by reaching through the kicker (last year).
* A main breaker "installed" by hanging it from its wires from the robot superstructure.

I'd be scared to see the list that Al could come up with. The bottom line is that no inspector can assume that any previous inspectors are perfect.

See you on Curie.

Re: Al's Annual Inspection Thread
 

Al,

I am confused by your post regarding battery chargers. You state the maximum charge current is 900mA, but the charger that comes in the FTC kit can charge at a 1.5A in one of the settings.

This is the same exact charger as the VEX Smart Charger from the same supplier. The only difference is that the VEX Charger has VEX Blue plastic as opposed to the supplier's standard black.

I am confused because you are going to see one irate ThunderChicken if inspectors try to tell me my VEX chargers are not legal to charge.

Paul

Re: Al's Annual Inspection Thread
 

So, it is illegal to use a different connector on the minibot?

Re: Al's Annual Inspection Thread
 

yes. I think radio shack has these if you destroyed the one in the tetrix kit. they come as an extension if you need 2 (chop in half and strip)

Re: Al's Annual Inspection Thread
 

I believe Al is just making a recommendation. ("The minibot batteries are best charged by a smart charger at no more than 900ma made for charging NiMH batteries.") There's no robot rule this year regarding which chargers are legal.

Re: Al's Annual Inspection Thread
 

Yeah, I believe it's just a recommendation also. There have been reports of teams having problem with the batteries when they were charging at 1.8A (CD has a couple of threads about it I think), so many have adopted the 900mA charging setting as a precaution.

Re: Al's Annual Inspection Thread
 

Hi Tristan,
Any chance you're inspecting in Newton this year? :)

-John

Re: Al's Annual Inspection Thread
 

Paul,
This is a recommendation for 900 ma (or less) chargers. The higher setting on the supplied charger, produces a lot of heat. I have had reports of teams attempting to use chargers of much higher current. Standard charge for these batteries is normally stated at 1/10 C to 1/3 C or 300 ma to 900 ma for a 5-10 hr charge cycle. Chargers have been reported at some events at currents in excess of 3000 ma. Without temperature feedback from the battery to charger, which is not provided by the Tetrix battery, these chargers can be dangerous as excess gas builds up and temperatures reach the point where burns may occur.

Adam,
The minibot battery can only be repaired with identical components as all other electrical devices.

Re: Al's Annual Inspection Thread
 

I think the applicable rule is <R55>, which prohibits tampering with control system components (including batteries) and then lists specific modifications to the control system components that are permitted. Part M permits repairs as follows: "Devices may be repaired, provided the performance and specifications of the component after the repair are identical to those before the repair." [emphasis mine]

As an example, repairing damaged battery connectors might be permitted under <R55> part M, if the connector parts (i.e., AMP Mate-N-Lock style crimp terminals and plastic housings) used for the repair have performance and specifications that are identical to those of the original connectors.

Re: Al's Annual Inspection Thread
 

From the Q&A...

Posted by GDC at 01/19/2011 07:27:13 pm
There is no prohibition against altering components from the Tetrix kit, other than motor
modifications strictly prohibited by Rule <R93> and the battery pack modifications prohibited
by Rule <R92>.

R92
C. no more than one 12V rechargeable NiMH battery pack identical to those supplied in the FTC kit of parts (PN W739057) except the 20A fuse may be replaced with an equivalent type of lower amperage,

Sorry to choose 'identical' from the wrong paragraph.

Re: Al's Annual Inspection Thread
 

Would putting a tamiya connector back on return our $200 in modified batteries to "identical"?

Re: Al's Annual Inspection Thread
 

Adam,
If that is the connector that was supplied then yes.

Re: Al's Annual Inspection Thread
 

I fly electric radio controled airplanes. The smart charger of choice (cheap & cheerful) is the Thunder AC6. We use it to charge our Tetrix batteries. It comes with a Tamiya connector. Being smart it tells you how much charge it takes to bring your batteries back to full. It has a Nimh setting we manually set to 900 mah max. Good news it's on sale now for $43. Here's a link

http://www.hobbypartz.com/thac6smbachw.html

Re: Al's Annual Inspection Thread
 

Chuck,
That is a very interesting looking charger that has lot's of features including progamability for NiMH battery packs. I downloaded the manual and it has some interesting cautions including this one with my corrections in syntax added...

This charger and battery to be charged and
discharged should be set up on a heat-resistant, non-flammable
and non-conductive surface. Never place
them on a car seat, carpet or similar.

Re: Al's Annual Inspection Thread
 

This is a very good caution.
Way back when I used to fly electric R/C airplanes (I still fly planes) and we used NiCad batteries. I made the mistake of charging the battery on the plastic piece, in front of the headlight, of my Dodge 024 Miser. The mistake was leaving the battery unattended. When I got back the battery had melted the plastic bumper :yikes: