BaneBots Shorted, Now What Do I Do?

[dexo568]

I've got a fairly large problem. My shooter subteam came to me today and said that one of their two BaneBots 775s burned out. This was in their attempt to construct a working shooter (they've never succeeded in making a functioning shooter thusfar). After perusing ChiefDelphi, I can see that
BaneBots shorting is a common problem. So where do I go from here? I have several options:
A. Attempt to fix BaneBot motor.
B. Order new BaneBot motors (their shipping lag is currently around six days, and this also shares a problem with option A in that I don't know if the shooter will even work once they actually assemble it with BaneBot motors).
C. Redesign shooter to accomodate different type of motor. Another team recommended using FP motors, but those are both currently in use by our ball conveyor belt.
Our current shooter design looks very similar to iR3 Creative's rectangular shooter system. Is there another option here I'm not seeing?

I'd really appreciate some mentors weighing in, because I have no adults to consult with. We're now rather short on time, and I need some experienced opinions on what the fastest way to get a working shooter is. It doesn't have to be the world's greatest shooter, just something that's reasonably effective. Thanks in advance.

[EricH]

RMA to BaneBots.

There is a temporary fix, however--12V from the lead to the case.

I assume that you've seen this thread; there is a wealth of information in it: http://www.chiefdelphi.com/forums/sh...ad.php?t=91733

But, like I said, contact BaneBots immediately and let them know there is a problem. They may have procedures for returning/replacing.

[RogerR]

Have you tried the am-9015 motor (andymark p/n am-0912)? It has very similar characteristics to the FP motors, and you should have received one in your kit.

[dexo568]

Originally Posted by EricH

RMA to BaneBots.

What is RMA?
Return Merchandise...something?

[EricH]

Originally Posted by dexo568

What is RMA?
Return Merchandise...something?

Something like that. It means that you contact the company and do what they tell you to do to return/repair/replace the product.

BaneBots has come out and said that they shouldn't be shipping anything with a case short. If you get something with a case short, then they would love to know about it, even if they don't replace it (and I think they probably will replace it, but I'm not sure about that).

[artdutra04]

Originally Posted by dexo568

I've got a fairly large problem. My shooter subteam came to me today and said that one of their two BaneBots 775s burned out. This was in their attempt to construct a working shooter (they've never succeeded in making a functioning shooter thusfar).

Did the shooter sub-team discover a case-short problem, or did their prototype actually smoke/burn out the motors?

While the RS775 motors have had a history of case-shorted issues, it's also entirely possible the shooter prototype overheated/smoked the motor. This is likely if the motor was stalled for some period of time, or if the prototype gearbox/motor mounting blocked the front vents on the 775 motor. All of the 500- and 700- series motors in the KOP (Banebots, FP, AM) have front air vent ports that must not be blocked or the motors will overheat and die.

[dexo568]

Originally Posted by EricH

There is a temporary fix, however--12V from the lead to the case.

Can you elaborate on this? I'm not sure what you mean. I tried running 12V from a DC power supply box and got no current.

[dexo568]

Originally Posted by artdutra04

Did the shooter sub-team discover a case-short problem, or did their prototype actually smoke/burn out the motors?

While the RS775 motors have had a history of case-shorted issues, it's also entirely possible the shooter prototype overheated/smoked the motor. This is likely if the motor was stalled for some period of time, or if the prototype gearbox/motor mounting blocked the front vents on the 775 motor. All of the 500- and 700- series motors in the KOP (Banebots, FP, AM) have front air vent ports that must not be blocked or the motors will overheat and die.

They say there was no smoke. i can't imagine what would have stalled it- it was just in a gearbox.

EDIT to say that it was in an official, unmodified BaneBot gearbox.

[EricH]

Originally Posted by dexo568

Can you elaborate on this? I'm not sure what you mean. I tried running 12V from a DC power supply box and got no current.

It's early in the thread I linked to--you short a lead to the case with something like the battery, then repeat for the other lead. Be warned, though, that teams doing this have reported problem recurrence and reduced performance.

[dexo568]

Originally Posted by EricH

It's early in the thread I linked to--you short a lead to the case with something like the battery, then repeat for the other lead. Be warned, though, that teams doing this have reported problem recurrence and reduced performance.

Willing to try that, but it sounds extremely unsafe. Any way to reduce risk?

[fox46]

This is how we fix them....

http://www.youtube.com/watch?list=UU...&v=zpxolE76bZw

[Ether]

Originally Posted by dexo568

What is RMA?
Return Merchandise...something?

Return Material Authorization.

You seek (and hopefully get) authorization from the supplier to return the defective material for repair/refund/replacement.

[Kevin Sevcik]

Also, also, Banebots does ship thing out quicker than 6 days. Gearboxes take 6-ish days to ship, but we just got a shipment of gearbox parts and bearing blocks that shipped out in 2-3 business days.

[theprgramerdude]

Originally Posted by dexo568

Willing to try that, but it sounds extremely unsafe. Any way to reduce risk?

The unsafeness is how it works. I suggest wearing thick gloves and safety glasses, naturally. There might be a big spark if you indeed do have a case short, so be prepared for that. You might also get nothing at first, in which case you might have to have someone else rotate the output shaft until you reach the short again.

[Dale(294engr]]

In deference to Eric et al..

Please do not use the 12v unlimited current from a tab to case to clear (burn open) the RS-555 armature short!!

Justification is The theory of a metal flake causing the short is flawed.

I have examined lots of 550 shorted case failures at multi Regionals & championships, none had a metal flake. All had armature winding short to the metal armature at the turn around (sharpest point). None had evidence brush holder to case debris. Post test cleared the brush holder every time. Every short traced to contact to case via rotor, thru end bushings bearings.

A metal flake is highly unlikely to cause a short to CASE! wire is enamel insulated
so such a short would need to be in the brush holder tab to case in which case it would easily shake out!

The HARD short of the armature winding is another story.

It is caused by mfr relying on epoxy insulation + enamel on wire, rather than customary brown fiber covering sharp iron ends so tight wraps have a buffer.

Done to maximize copper window in small armature winding areas + save $.

Check out CIM armature brown fiber insulation use to effectively eliminate this failure mechanism.

As motors become smaller mfrs seek alternate methods like omitting fiber barrier.

Enamel wire tightly wound over sharp cornered steel laminated in 550 armatures has extensive history of high short to case fail rate. high as 50-70% new out of boxes at Regionals where I was RI in 2011 going back to 2010

Burn open short clearing is not only DANGEROUS but also BAD fix.

12v ~800A: blows apart offending single wire short armature to case ~debris?

This disables one armature pole reducing motor power plus asymmetrical excitation. Not something you ever want to put back into a competition robot!

Also it may set up a condition of intermittent dynamic to case continuity!
..cause now you have two burnt loose copper ends free to flip around.

In improperly geared CIM's I've observed a similar gradual degradation where too high a gear ratio combined with heavy throttle by driver pushing opponents etc keeps CIM at High current, low torque part of curve too long.

Much self heating results weakening copper wire bond to commutator.

Subsequent High RPM force causes wire to detach, fly off, or high current burnout from concentrated current density in a short work weakened copper (bending back & forth), opening a pole on the armature.

The degraded motor still starts up & spins with remaining poles but at greatly decreased performance and not so smooth anymore! (& lower start-up & running torque due to lost pole)

Hint Perform Destructive Failure Analysis of failed motors as a class exercise to gain better understanding of what happened to apply forward. (destructive = observe closely then unwind the rotor carefully inspection as you go for problem areas (wire may break as you unwind). Take close up photos when you find a 'smoking gun', document in daily log pics & text description + hypothesize why/how it happened, then publish results.

Good luck.. all teams going with RS-550's again this year!!
Stock up on pre-tested open spares if you need capability it serves!
The Spare Parts will run out of their limited replacements EARLY!

Teams NOT using their RS-550s please Graciously bring them to regionals
to turn-in to Spare Parts to help your fellow competitors!!