Re: Banebots RS-775 Case Short
 

Are you seriously ignoring the second best motor in the KOP (following the CIM) just because it has a little, easily avoidable, problem. As far as I can tell, the case shorting does not hinder the motion of the motor directly, it can only cause problems when connected to an improperly isolated frame. I understand that creating a perfectly isolated frame is sometimes difficult and the easiest way to avoid the problem is to isolate the motor, eg, by putting the motor in a plastic housing like a drill motor transmission or even a PF gearbox. I still don't know whether either of the 775s we used last year had case shorts because the way we used them, it didn't matter.

Re: Banebots RS-775 Case Short
 

I took apart a 775 last year, and found the cause of the "case" short. Nothing is shorted to the case, the winding is shorted to the armature. Since they haven't fixed the problem this year, I have no confidence in the motor.

We used the 540/550 BB motors and gearboxes in previous years, when the gearboxes were provided in the kit. They worked fine for us.

We can find other ways to make things move.

Re: Banebots RS-775 Case Short
 

One winding is shorted to the armature? So what? As I understand it, that shouldn't affect motor performance. The 775 is much more resilient than a 550 and, in most cases, requires less reduction.

Re: Banebots RS-775 Case Short
 

Essentially you are turning your back on some very reliable and powerful motors if you exclude all BB motors.
By not informing your students of the scholarships available to them by participating in FIRST, you would be turning your back on extraordinary opportunity for them.

Yeah, kind of convoluted, but I think you can see where I was headed with that.

Bottom line:
RS775 = NO
RS550 = YES
RS540 = YES
RS395 = YES
...........

Re: Banebots RS-775 Case Short
 

http://www.chiefdelphi.com/forums/sh...9&postcount=74

http://www.chiefdelphi.com/forums/sh...4&postcount=82

Re: Banebots RS-775 Case Short
 

The 775 does require less reduction, but with it's known flaw it isn't the clear choice for most teams. No need to mock someone for ruling them out.

As long as the rules let you choose between the 550 and 775, we will NEVER use those specific 775 motors (not all 775s, as I have several for other projects that are champs).

The 550 is trivially weaker, a good deal lighter (which is a con in some systems for heat dissipation), and is nearly the exact same as the generic average FP we get year to year that has proved to be a reliable champion in FRC.

TL;DR. I agree with squirrel and others; 550's are the way to go.

Re: Banebots RS-775 Case Short
 

I'm not mocking, I'm questioning the reasoning to avoid such a great motor when its only little flaw can be avoided so easily. I understand being extra careful with the motor and not wanting to use it in a BB or similar transmission, but completely ignoring the 775 seems quite rash.

Re: Banebots RS-775 Case Short
 

It seems if you get one without defect, it appears to be a great motor. The problem for us was getting our hands on one without defect.

Avoiding if possible just for our own sanity.

Re: Banebots RS-775 Case Short
 

FWIW I just got off the phone with Banebots and they are going to replace our motors. I talked to tech support and the gentleman seemed baffled because they are testing/checking all the motors before they are sent out.

We will still give the 775 a shot after our success using it last year, but I will always have some doubt about the motor. I will make sure we always have a plan B

Re: Banebots RS-775 Case Short
 

Doesn't that mean that there are (at least) two different models of motors using the same BaneBots part number?

To which motor(s) do the present specs on the BaneBots page apply?

Does FIRST know that there are multiple motors, and is FIRST alright with this? This might be legal if either:

1. Both types of 775s were provided to various teams in the KOP; or
2. The "acceptable part numbers" part takes precedence over "the BaneBots motors provided in the KOP".

Re: Banebots RS-775 Case Short
 

If this year's batch of Banebot RS775 motors also suffers from a lot of case shorting problems, but still delivers on the 273 Watts claimed in the motor spec sheets, then there is an easy solution: complete electrical isolation from every other metal part on the robot.

This must be done both via the mounting plate (I'm thinking either Lexan or Delrin) and via the motor gearing (I'm thinking steel or brass pinion on motor, then using an Delrin/acetal spur gear for the first reduction). To achieve the latter requirement, I'm thinking this can easily be achieved by going 24DP for the first gear reduction and making a custom hex/keyed aluminum hub for the VEX 60-tooth High Strength gear (yup, I'm biased ;)), as shown below:

Re: Banebots RS-775 Case Short
 

So you have non-metal pinions and screws on your motor? To me it seems VERY hard to electrically isolate a 775.

Re: Banebots RS-775 Case Short
 

You essentially have to use something like Art's suggestion above to get total electrical isolation.

When we ran into case short issues last year, the first tactic was to isolate the motor. We tried many things hoping that if we could eliminate all but the pinion electrical connection we would at least cut down on the issue. It didn't matter, after isolating everything but the pinion, the short was still present through the whole frame.

-Brando

Re: Banebots RS-775 Case Short
 

The armature is pressed to the shaft, the windings are shorted to the armature. That's what I'd expect to happen.

Re: Banebots RS-775 Case Short
 

Not that I am trying to sell Banebots, but I have it on good authority that the source of the shorted motors is no longer supplying parts to Banebots. I am not pushing you to use them but if you do, please test while rotating and report your findings. Thanks in advance.