Tool time.

[He Who Shall Not Be Named]

Thanks David and everyone,

I have another series of questions that I hope you don’t mind answering, even though some aspects we’ve been over. I suppose I just need a little further clarity.

Leaks in drive shafts.

David, do you guarantee that your shafts don’t leak? Or is this a hot potato? I can vouch I have one of your older SD’s and it don’t leak. But are you that confident in the product?

My latest design hasn’t leaked until today, So I was really disappointed and I am assembling the first ZB2 for a customer and am currently checking the shaft seals and Uh oh, a leak.

Now you know my seal design is similar to yours, I use an Oil lite Bush with an outer housing and a U cup seal lightly glued to the top of the outer housing and the shaft is pushed through. My biggest unknown is how much grip should the lip of the cup seal push around the shaft. Obviously when you push the shaft through the lip it should flex outwards and wrap around as you push the shaft up. I am still trying to work out the fine balance between how tight this should be.

I am guessing that if it’s tighter then the motors just pull more amps? But also if you run the motor for longer periods out of water then the lip rubbing against the shaft will cause wear?. Do you not run the shaft out of the water for any length of time?

I am am convinced that there is something really subtle and tiny that I have missed, maybe it’s just getting the tightness of the lip on the shaft just right? Maybe my lip seal isn’t tight enough?

I have some pics here of my set up if it helps, I have looked at all your photos of the shaft arrangement that many times. I hope my line of enquiry make sense.

Thanks for your time,

david H.

I would say that 90% of the shaft seals I assemble and test are leak free -- this testing of course is part of the MSD/SD test and certification process each WTC gets here before sending it off to the customer (these days, The Nautilus Drydocks).

Leaking shaft seal assemblies are either repaired or replaced. The major cause of a shaft leak is a crack or scratch of the seal inner bore where the cup-seals outer edge makes contact; that portion of the rubber that makes the watertight seal between seal and inside bore of the shaft seal body. My seal bodies today are machined pieces of polyurethane sprue. A cracked or scratched inside bore would permit water to flow around the outer rubber seal lip, through the crack, letting water into the motor bulkhead.

I see that you are adhering the rubber cup-seal outer lip with adhesive. Stop doing that! Use silicon oil (not silicon grease!) to lubricate the outer and inner seal lips during assembly.



Typically the manufacturer supplies the cup-seal with an inner lip diameter slightly smaller than the stated diameter of shaft it is supposed to seal against. In our sizes that's a few thousandth's of an inch smaller. They don't have to be tight.



Are you using proper cup seals or the spring tensioned seals used by the piston crowd?

David

[Davidh]

Hi David,

Thanks very much. I am using Cup seals, not the spring ones. Not simmering. I suppose it would make sense that the outer edge of the cup seal not pressing up,adequately against the inner dia of the housing would be where the leak is occurring. It’s a larger circumference.

I will give silicon oil a go.

David H.

[He Who Shall Not Be Named]

Hi David,

Thanks very much. I am using Cup seals, not the spring ones. Not simmering. I suppose it would make sense that the outer edge of the cup seal not pressing up,adequately against the inner dia of the housing would be where the leak is occurring. It’s a larger circumference.

I will give silicon oil a go.

David H.

There you go: reduce the bore diameter of the seal body, use

[Davidh]

Hello David,

I hope you and Ellie have a good Christmas.

I have a request of you. A couple of months ago I was looking through some photos of your work (today’s work) and you were testing motors. (Brushed) you had a pic of an ammeter attached to a circuit with a speed controller. I assume that you were seeing how many amps were being pulled by a given motor on a circuit. Could you possibly upload any more pics of this set up?. I am testing endcap assemblies with motor at the moment and have an amp meter. I Am just not sure how to set it up.

I have been running tests on my ZB-1/2 single motor twin drive and have found that the motor gets warm, but one of the leads gets really hot really quick.doing something wrong somewhere. I don’t know if there is too much friction on the shaft?

any suggestions...?

Thanks,

David H

[He Who Shall Not Be Named]

Hello David,

I hope you and Ellie have a good Christmas.

I have a request of you. A couple of months ago I was looking through some photos of your work (today’s work) and you were testing motors. (Brushed) you had a pic of an ammeter attached to a circuit with a speed controller. I assume that you were seeing how many amps were being pulled by a given motor on a circuit. Could you possibly upload any more pics of this set up?. I am testing endcap assemblies with motor at the moment and have an amp meter. I Am just not sure how to set it up.

I have been running tests on my ZB-1/2 single motor twin drive and have found that the motor gets warm, but one of the leads gets really hot really quick.doing something wrong somewhere. I don’t know if there is too much friction on the shaft?

any suggestions...?

Thanks,

David H

New type brushed motor are examined to determine no-load and stalled current draw for a specific voltage. My torque meter are my pinkies and wrist. I'll tear into a new motor type to get ACTUAL dope as to number of poles to the armature, winding turns per pole, gauge of the windings wire, and if spark suppression is provided.

You always wire the Ampere meter is series with the device whose current load you are measuring. I only bother with these numbers because they drive the type BEC and fuses I will select to control and protect the motor.

Increase the cross-section (wire gauge) of the power cable if it gets warm -- heat generated is inversely proportional to the conductors cross-section. The power cables must be able to handle the load of a stalled motor getting full power from the ESC.

Hint: fuse the motor, not the battery! That boat ain't coming back up if hotel services go dark.

Here's how to wire the Ampere meter and some other shots showing how I hook things up as well as how I test things:

















































David