Quick question, probably asked a thousand times...

[Sparks333]

WHY does FIRST insist on using oversized wires??? I mean, I can understand that FIRST doesn't want any wires to fail, but if you are using thicker wire than the leads on, say, the compressor, than the extension will not burn up, but the leads will. That's not avoidable. Also, why do you have to use 6 AWG wires after the 120 amp breaker? If you have enough power to melt a 6 AWG wire, then it will trip the breaker. PLEASE TELL ME WHY!!!!!

Off on a tangent,
Sparks333

[nuggetsyl]

that way your robot does not go up in flames i know because ours did the first year we played

[Kevin Sevcik]

Ummm.. the 6 AWG wire from the batteries looks to be just about right based on a random google search. Check here:
Recommended Current (http://www.alphawire.com/pages/383.cfm?partner=0&part=0)
As for the rest... many teams will attest that the standard wires to the drills aren't thick enough to handle current right now, and go to great lengths to replace them. I don't really think having wires that are too thick is THAT big of a problem unless you're really pick about easy routing or you're just that close on weight.

[Al Skierkiewicz]

As for the rest... many teams will attest that the standard wires to the drills aren't thick enough to handle current right now, and go to great lengths to replace them. I don't really think having wires that are too thick is THAT big of a problem unless you're really pick about easy routing or you're just that close on weight.

Wire size and current carrying capability is based on temperature rise for a given size wire at a particular current. Al of our wiring is out in the open and not enclosed in conduit so that raises the amount of current it can handle. Also factored in are the lengths of a given wire as to how much series resistance will affect the voltage supplied to the load. Again our wiring is fairly short compared to real world applications. As to the blue wires for the drill motors, even if they were four time the series resistance of #10 they are only four inches long each and the insultaion is 200 degree C rated. #10 is .001 ohm per foot so even at 4 times the resistance, 8 inches of #16 wire is only .003 ohms. At 129 amps of stall current, that only drops a little more than 0.3 volts.
Whena a branch circuit breaker is chosen, it is sized to protect the wiring in that circuit from reaching a temperature at which the insulation will fail due to heat rise. Hence the #6 is protected by the 120 amp delayed action circuit breaker. The breaker will trip before current flowing through the #6 has a chance to heat up to the point of failure. Like wise for the 40, 30 and 20 amp circuit breakers. First mandates some apparantly larger wires for those circuits that teams have had trouble with in the past. You could wire your entire robot with #6, if you had enough weight under 130 lbs. but why.

[Kevin Sevcik]

About the blue wires, I was referring to all these anecdotes I hear about the drills unsoldering their connections from excessive heat. I dunno what causes it, but I'm inclined to believe that it actually occurred if people say it did.

[Mike Hendricks]

if you are using thicker wire than the leads on, say, the compressor, than the extension will not burn up, but the leads will.


Not if the 20a breaker on the compressor or spike pops first :)

The fuse on the spike, blows fast. We've discovered this while reversing motors REALLY fast (using old spikes and old motors)

[Austin]

FYI: IF you want some really good, flexible 4 AWG wire 100x more flexible than the Kit 6AWG ). PartsExpress carries some great stuff...this 4AWG is made up of 1672 strands of 36AWG wire! It's really amazing stuff. They also sell ultra-flexible 8AWG wire made of 675 strands of 36ga. wire. It's great stuff...what we're using this year. Makes wiring a lot easier.

4AWG (http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=100-194&DID=7)

8AWG (http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=100-174&DID=7)

[Aidan F. Browne]

WHY does FIRST insist on using oversized wires??? I mean, I can understand that FIRST doesn't want any wires to fail, but if you are using thicker wire than the leads on, say, the compressor, than the extension will not burn up, but the leads will. That's not avoidable. Also, why do you have to use 6 AWG wires after the 120 amp breaker? If you have enough power to melt a 6 AWG wire, then it will trip the breaker. PLEASE TELL ME WHY!!!!!
Sparks:

In sections 5.2.6 and 5.2.7, you will notice that there are not any rules on power wiring downstream the speed controllers and relays. (This was not an accidental omission).

Section 5.6 contains guidelines for wiring... but they are only guidelines - not rules.

At all times you have to be compliant with the safety rules.

Hope this helps!

:)

Aidan

[Al Skierkiewicz]

About the blue wires, I was referring to all these anecdotes I hear about the drills unsoldering their connections from excessive heat. I dunno what causes it, but I'm inclined to believe that it actually occurred if people say it did.
Kevin,
Believe it! The quality control on the wire solder job is not very good. If you run the motors (in practice) long enough to get the brush assy. hot, the wires do start to melt the solder. Since the connection is not a good mechanical one first, the connection series resistance rises as the solder melts making the problem worse. Sort of a domino effect.

Aidan, I am missing something. Table 5.2: Minimum Wire Size and Protection by Device Type in Section 5.6.2: Wire Size, lists the minimum wiring sizes for devices and controllers. Are you saying this is a guidline?

Newark has some superflexible wire that is zip cord #10, red paired with black, part # 24-1930 for the 100' roll, about $35/roll.

[Adam Krajewski]

About the blue wires, I was referring to all these anecdotes I hear about the drills unsoldering their connections from excessive heat. I dunno what causes it, but I'm inclined to believe that it actually occurred if people say it did.
We experinced this first hand after driving our prototype drivetrain a little too much last year. Check out this thread for my solution: http://www.chiefdelphi.com/forums/showpost.php?p=131959&postcount=21

[Sparks333]

Wow! I really didn't expect so many posts!
First off, let me tell you the deal. I wrote that post in a fit of rage when I ran out of 10 guage wire when the leads I was soldering to was 12 guage. I had plenty of 12 guage, but no 10. I, in my madness, went off, as I stated, 'on a tangent', and started ranting. I knew the answer, and saw the wisdom, but that was after I found more 10 guage.
Thanks for all the info. I didn't realize that the wiring specs didn't apply to downstream. That's interesting.

Again, thanks for helping me get through the madness!

Sparks

[Elgin Clock]

Thanks for all the info. I didn't realize that the wiring specs didn't apply to downstream. That's interesting.
And of course, that was the way it was written and thus done in 2004.
Who knows what 2005 will bring?

Maybe a change, maybe not.

[Mike Betts]

WHY does FIRST insist on using oversized wires??? I mean, I can understand that FIRST doesn't want any wires to fail, but if you are using thicker wire than the leads on, say, the compressor, than the extension will not burn up, but the leads will. That's not avoidable...PLEASE TELL ME WHY!!!!!...

Sparks,

I tried to address this issue last year: Last Year's Discussion (http://www.chiefdelphi.com/forums/showthread.php?p=145607&highlight=awg+motor+temperature#post145607)

Please let me know if this does not make sense.

I can assure you that proper engineering has gone into FIRST's selections. People like Al, Adrien and I would be all over FIRST if they were being too conservative or too risky.

Please remember that no engineering decision is ever black and white. Without compromise, engineering would be boring. Just as you and your team will make hard decisions as you struggle to build a robot, FIRST has had to make hard decisions concerning maximizing safety while making the number of rules as small as possible.

It's not easy...

[Steve W]

Kevin,
Aidan, I am missing something. Table 5.2: Minimum Wire Size and Protection by Device Type in Section 5.6.2: Wire Size, lists the minimum wiring sizes for devices and controllers. Are you saying this is a guidline?


I do no believe that RULE 5.6.2 is a guideline. When I was doing inspections last year it was enfourced as a rule. This was true at 3 regionals and championship while I was assisting with inspections. There was more than 1 challenge but 5.6.2 was always brought forth as the rule.

[Al Skierkiewicz]

Sparks and everyone,
Not to let anyone get misled at this late date by some of the early season discussion, we need to make some things clear based on the actual competition practice and rules. In the sections quoted by Aidan above, there is a small reference to conforming to the "robot power distribution" drawing. In that drawing you will find a table that states that certain motors and speed controllers wired to those motors be wired with #10. Additionally, the inspectors sheet required inspectors to check that wiring of the correct guage was used in each leg or branch of the circuit. As an inspector at GLR, MWR and Nationals I can assure you that we were trained to watch for these wiring minimums.
As to the original question relating to the wire size supplied with devices, we must add that resistance in wire (and the heating that takes place in that resistance) is also a function of length. The compressor and drills both have fairly short leads where the resistance is at a minimum. Additional information on the drill's #16 is that the manufacturer chose the high temp wire with the knowledge that the wire may burn open at stall currents. Design engineers at the manufacturer consider the #16 a fuse and as such, FIRST chose to rule that it be left attached. Other than the challenge it presents in wiring, teams should not have too much trouble in leaving it attached. I will add that many teams have found the solder job less than adequate and remove the brush assy by moving aside the little keeper, correctly solder the wire in place, and replace the brush assy after cooling.

[Sparks333]

Thanks, Al. That's good advice on the drill motor. I can't say I'm unhappy about seeing it leave.

Sparks

[Al Skierkiewicz]

Sparks,
The drill motor as far as I know has not been dropped. We won't know for sure until the kit of parts comes out. I know there has been some discussion but the most recent is on the "rumor mill" board and should not be believed. If someone has some concrete info please let me know.
The drill motor has some flaws but that does not make it a bad motor. It is a pretty good merge of speed, power, size and weight. Coupled with the transmission and drive system designed by FIRST, you can have a driving base within a few hours and then concentrate on other parts of the robot. Although you will see lot's of people complain about parts (sometimes that includes me) all of us are held to the same constraints. That's what makes this so much fun. We all have to overcome the same things and still try and compete. We have used FP, Bosch and/or Chalupas in our drive systems over the last few years. We won nationals with two FP and two drills in our crab steering modules. I expect to see several of the AndyMark multimotor drives using these same motors when I inspect this coming season.

[Sparks333]

Good point, but they are selling the extras. I think they are either replacing it or getting rid of it.
PS: It's chuapa, not chalupa.

Sparks

[Al Skierkiewicz]

Good point, but they are selling the extras. I think they are either replacing it or getting rid of it.
PS: It's chuapa, not chalupa.

Sparks

Sparks,
The selling of the extras may be to just clear out the storage for new inventory. I use "chalupa" because many of us used that name when the motors were first introduced. Kind of an inside joke I know, but after 9 years of late night sessions and all of the other craziness you do get a little punchy. Maybe just a midwest thingy. Besides I can spell "chalupa".

[Doug G]

FYI: IF you want some really good, flexible 4 AWG wire 100x more flexible than the Kit 6AWG ). PartsExpress carries some great stuff...this 4AWG is made up of 1672 strands of 36AWG wire! It's really amazing stuff. They also sell ultra-flexible 8AWG wire made of 675 strands of 36ga. wire. It's great stuff...what we're using this year. Makes wiring a lot easier.

4AWG (http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=100-194&DID=7)

8AWG (http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=100-174&DID=7)

We've be thinking about using some more flexable wiring solution this year, but one question I have is do you still use the Power Connector that comes in the kit for the batteries? Is there anyone who uses a more flexible or convienent connector for their batteries?

[Al Skierkiewicz]

Doug,
I am expecting that FIRST will reguire the 50 Amp Anderson connector again this year. The connectors are donated and we should use this generous resource. In the past we had used a 100 Amp version of the Power Pole without failure.
Please remember that you don't have to use the wire length that come preterminated with connector. Order extras so you can add them to your spare batteries and the battery charger. Clip leads from the charger is likely the highest cause of failure in this connector. The sharp points on the clip leads damage and score the connector faces and produce hot spots that cause eventual failure at high currents.

[Gamer930]

Order extras so you can add them to your spare batteries and the battery charger. Clip leads from the charger is likely the highest cause of failure in this connector. The sharp points on the clip leads damage and score the connector faces and produce hot spots that cause eventual failure at high currents.
We have always used Clip Leads. . . Never had any problem but little worried now. I see your reasoning behind it and will look into switching the connections.
Is there a recommended way from going from #14-16 wire out of the charger to the #6 wire of the connector???

Another subject: Yes, they do check to make sure you use the right wire size in each leg of the circuit. Al Skierkiewicz inspected our robot at the Midwest regional and noticed our wire to be #14 wire instead of #12 wire going all the way up to the top of our towers. We thought we were right according to a rule update but actually we weren't. We ended up spending the 30-40 mins of practice day to change it. FIRST makes the rules so we are SAFE and not going by the manufactures recommended facts. Safety FIRST

[Al Skierkiewicz]

We have always used Clip Leads. . . Never had any problem but little worried now. I see your reasoning behind it and will look into switching the connections.
Is there a recommended way from going from #14-16 wire out of the charger to the #6 wire of the connector???

Jason,
If you buy the connectors without wires already mated it is pretty easy. If you use connectors from the KOP, using a small screwdriver you can release the contact from the shell. (Look in the contact end and you will see a steel spring holding the tip of the contact. Just move it out of the way and the contact will release out the wire end of the connector.) Cut off the #6 wire at the point it exits the contact. Using a large soldering iron just tin the connector and tack on the #16 from the charger. Be sure to replace the contact in the right side and check the polarity of the wiring before you use it to charge a battery. Or if you find it easier to open the crimp and release the #6 you can do that as well.

[telkanuru]

To the original topic, I believe it comes down to safety factor. Safety factor is a simple calculation- the max voltage/force/whatever an item can withstand theoretically divided by the max it's supposed to take. So a wire capable of carrying 40A on a 20A breaker would have a SF of 2. A SF of 2 is recommended on devices that do not have the possibility of endangering a human life, SF of 3+ otherwise. As for connecting larger wires to smaller, I guess they can't do much about their suppliers...