OTW Dive Module - operation weirdness

[apa-228]

Got a thought during the night, do you have capacitors connected between the motor lead terminals and motor casing? If a capacitor failed by shorting it would allow current flow to the motor casing. This would be more likely than commutator insulation failure.

[subdude]

Greg - no prop, shaft only. Problem manifests itself as soon as the tip of the shaft touches the water.

Ralph - there can be absolutely nothing touching the water but the shaft when it occurs. Or, the entire cylinder can be wet. No difference. The only other things coming out are 2 pushrods (thru exit housings in the plastic end cap), 6 studs for holding the cyl together (screwed into plastic) and the battery terminals (insulated, separated, and again no difference if they are wet or dry)

Mike - brushed motor. I've changed it to a different motor, no change in the fault.

apa - there are caps on the motor. When I changed the motor, I soldered new caps to the replacement motor.

[eckloss]

Probably a silly point, but were you holding it with your hand/s the whole time, or did you also allow it to free float?

[JWLaRue]

Both.

-Jeff

[mike dory]

Subdude When all goes sideways with one of my boats, I CALL WILL Oudmayer. He's up todate on alot of stuff that I'm not.
There is a bunch of us going to our lake this Sat. for mini fun run, I'll hit him up for you if you like, Send me a P.M. with your phone number. We'll call you from the lake.

[subdude]

Hi Mike,

Thanks for chiming in, great to hear from you. I sure miss seeing you every year at the regatta!

Anyway, I *think* I made a little progress last night. I need to spend another evening changing some things and testing, so hopefully will know more tomorrow.

Thanks for the offer of the call with you and Will, if things don't get turned around by then I'll take you up on it.

Hope you're well.

Jim Butt

[Ralph --- SSBN 598]

Some time back, a year or two, I was having issues with Tx range, about 40', and I was having servo jitter and motor(s) that didn't do what they were suppose to.
At the lake, WIll looked at my equipment in the cylinder as said I might have a power distribution problem.
Okay, what does that mean?
Will said, I had too many power inputs to the Rx.

I had a secondary battery for the Rx.
I had 2 speed controllers. (1 for the propellor and 1 for the ballast pump)

He suggested I remove the Rx battery completely.
Then he suggested I remove the red wire from the ballast pump.

This baffled me completely.
Will went on to explain that the speed controllers where sending power to the Rx through the red wire and through the black wire on the power side of the speed controller.
I was getting power to the Rx from 3 sources.
1 Rx dedicated battery and then from the other batteries through the speed controllers.

I don't know anything about the electronics in these things but I know Will knows what he is talking about.

I removed the dedicated Rx battery.
I disconnected the red wire on the ballast pump speed control. (this is the Rx to speed controller wire.

I made sure the main power wires to the speed controllers was correct.
Turned on the system and every thing works but it did before with lots of issues.
Now there were no issues and I had a tested range of over 800'.

What I think was happening is with 3 different power supplies to the Rx, the Rx was confused.
The power voltage inputs were not synced up coming from the speed controllers and giving different signals.
==============
On your issue of changing when put in the water.
I would be looking for power getting to the motor ground casing.
Check that the black wires are connected to the negative on the motors.
And I would look to see if a frayed wire is touching the motor case.
A black wire is not a problem but if a red wire is touching, putting the shaft in the wire would amplify the current.


Can't wait to learn what is going on here.
It needs to go in to my Check This book!

[subdude]

Well, issue resolved.

This module originally had a 3:1 gear reduction. When I changed it to direct drive, I changed the entire motor/motor mount/propshaft/seal housing. That was when the glitching started. I originally thought that the gearbox one was doing it as well, but that was apparently actually a slipping universal joint.

So, last Sunday Jeff brought me a replacement motor. I soldered caps to it and installed it. The glitching did not go away, causing all the aforementioned drama. After replacing everything except the power lead thru the center of the ballast tank and the forward bulkhead, the issue remained.

Tonight I went thru everything, checking for voltage leaks, excessive resistance, etc. I cleaned every connection. I installed a ground jumper from the battery negative lead to the motor case. And, the problem remained.

I decided to try once again turning off my shop lights, in case they were causing interference. We did this Sunday afternoon, but I'm doing things 3 and 4 times now to verify. With the lights out tonight, it was quite dark. Every time the motor sputtered and glitched, I saw arcing from the brushes and commutator.

I removed the module from the tank, replaced the motor / propshaft with the original one with the gearbox, and plopped it back in the tank. The heavens opened, the angels sang, and the issue was completely gone. I ran it for 30+ minutes without a single glitch.

Bottom line, I had a bum motor, and replaced it with another bum motor. What are the odds? Think I'll go buy a lotto ticket.

And with that, all is right with the world. Thanks to all for all the interesting ideas and help!

Jim

[apa-228]

Happy to hear you worked it out! Troubleshooting is sometimes fun, but most of the time it is also a lot of frustration.

[mike dory]

Your Welcome Jim, God Speed Mike

[JWLaRue]

We should probably note that Jim and I bench tested the new motor with it directly connected to a variable power supply....and it dit not exhibit any problems running. So that would not have clued us in to the issue.

Definitely one for the troubleshooting book!

-Jeff

[feet wet]

A very interesting lesson learned. Thank you for sharing your findings. As an aside, I have been "breaking in" my motors by submerging them in water and running them for up to several hours, with repeated changes of water when it gets too black. This process really helps to seat the brushes and reduce the arcing of the motors, as well as quieting them. I don't know that it would have helped much in this case Jim, but it may have showed up the bum motor before the original installation.
Jonathan