Is it OK to cut the fins and tits off a squirrel cage rotor?

[kubeek]

Wouldn't that work without filling it with oil?

As oposed to air? Air is way too compressible to balance out the external pressure at the bottom, yet have close to zero pressure at sea level.

 

[strantor]

I worked at GE motor factory once in Murfreesboro TN those tips are ejector pin holes for the die cast machine. They are left long for a reason it makes it easy to balance the rotor. Rotors spin in a machine when the red lights comes on the machine stops with the red lights on. Red light lines up with the tips that need to be shorter on the ends.

Read about the Tesla Motor your motor in oil will have oil resistance which will pull extra high idle current when the motor is not under load.

Ok, good to hear. I'll whack off the tits and post a nude pic.

About it pulling higher amps in an oil bath, I fully expect you're right. Even after streamlining the rotor I expect the oil to put up a fight. But even so, I also expect that filling the motor case with oil that conducts heat 10-15 times better than air, I will actually improve the current carrying capacity of the motor.

I've compared rotor/stator designs between TEFC, TENV, and TELC. What I found is that In general, if the same rotor/stator set is used in a non-ventilated and also in a liquid cooled motor, the liquid cooled version will have around double the HP.

So while I may be putting a dent in the efficiency, I'm probably turning a 1.5hp motor into at least a 2.5hp motor. And I don't expect the oil drag to eat up that entire extra HP. But we will see. I'll post the results after I test it.

 

[gary350]

Wouldn't the oil drag be considered a load?


As long as the motor winding are being adequately cooled by oil circulation substantial overload compared to open air operation is not a problem meaning a 10 HP rated air cooled electric motor running submerged in a bath of light viscosity oil can easily take being overloaded to the 20+ HP equivalent input power levels without winding overheat damage.

By machining the rotor down to be as smooth as possible on the exposed surfaces the overall mechanical drag will be greatly reduced. By doing that the main source of drag that will be present will be from simple surface tension between the rotor and the oil.
Taking the fins and stubs off is basically like taking an oar for a row boat and turning it 90 degrees to its normal orientation when it's in the water. Same surface area in contact with the fluid but the ability to transfer mechiacal motion energy to fluid displacement is greatly reduced.

Maybe so but why would anyone want to 3 phase motors are a dime a dozen. The shaft is designed for 10 hp not 20 hp. The shaft is pressed into the rotor it is designed for 10 hp too. The shaft key way is designed for 10 hp. I have seed shafts twisted off, shafts spun inside the rotor, key ways sheared off. Too much torque can break off the motor mounts.

 

[tcmtech]

Maybe so but why would anyone want to 3 phase motors are a dime a dozen. The shaft is designed for 10 hp not 20 hp. The shaft is pressed into the rotor it is designed for 10 hp too. The shaft key way is designed for 10 hp. I have seed shafts twisted off, shafts spun inside the rotor, key ways sheared off. Too much torque can break off the motor mounts.

Those must have been some pretty low-grade motors for them to twist off or they were being used in some horrifically abusive/neglectful environments.

The standard shaft size for a 10 HP motor would be 1" - 1 1/2" inches in diameter of which unless it's made of some really junk iron would be good to for 1000 - 2000 foot pounds of torque which is way beyond the torque levels a motor that size could produce on it's own.

As for they why apparently you have not been following this and the other threads related to it. The motors are being used out at sea under ~500 feet of water and Strantor is looking for viable alternative methods of being able to run common cheap motors at that depth Vs having to buy specialty submersible motors that can cost 20 - 50 times as much. That's why!
It's not about how much more power he can get out of a motor. It's about making it survive under 250+ PSI of pressure while surrounded by highly conductive seawater. The ability to overload them past their normal air cooled specs without damage is just an added bonus.

 

[dr pepper]

Looks professional strantor, I was going to mention lube for the bearings, its going to be much colder underwater and ordinary grease might not do the trick, but I see the internal oil does the job, and no doubt it'll be ok for lubing the 'box.
What make of 'box is it, hopefully not a bonfiglioli.

On a lighter note I've known outdrives run for ages with nothing but seawater for lube when a seal has gone.

 

[schmitt trigger]

You may find that even the lightest commercial oil imposes unwanted drag.

I've read that in these instances, that the oil may be further diluted with kerosene.

But I find your idea correct, file down all those protuberances from the rotor.

 

[Mikebits]

There's a piece of the puzzle you're missing. I thought I discussed it, but maybe I neglected to mention the integrated accumulator. There's a collapsible bellows exposed to atmosphere which keeps the internal pressure always a few PSI higher than atmosphere via compression springs. Here's some screenshots of my current design. It's rough; I'm not done.
View attachment 98568 View attachment 98569 View attachment 98570 View attachment 98571 View attachment 98572

Strantor, did you make the 3D drawings? Pretty nice. Knowing a 3D tool along with your electronics background makes you quite versatile.

 

[strantor]

Looks professional strantor, I was going to mention lube for the bearings, its going to be much colder underwater and ordinary grease might not do the trick, but I see the internal oil does the job, and no doubt it'll be ok for lubing the 'box.
What make of 'box is it, hopefully not a bonfiglioli.

On a lighter note I've known outdrives run for ages with nothing but seawater for lube when a seal has gone.

Bojangles? For this experiment I scraped the bottom of the barrel for the **broken link removed** (and **broken link removed**).

The gearbox shipped with ISO460 gear molasses in it. That's going to be replaced with ISO32 hydraulic fluid (Though I might try out more viscous oils and compare results). In an industrial setting where gearboxes are expected to run continuously for years without causing downtime, this would be a huge no-no, but as this tool probably won't see more than 100hrs of use per year, I think it's safe. I'll check for particles of death in the oil after a good 48hr torture test.

 

[strantor]

Strantor, did you make the 3D drawings? Pretty nice. Knowing a 3D tool along with your electronics background makes you quite versatile.

Hey, thanks. Yeah I made the drawings in Sketchup. It's the only tool I know, and that's a problem. When it comes time to have these parts made, machine shops are accustomed to having CAD files submitted in formats that translate to their CAM software to be more-or-less directly loaded into their CNC machines. Sketchup doesn't do that. Sketchup is for hobbyists. Solidworks and Autodesk are what the industry uses, and they play nice with the machines. In the past I have had to submit my designs as PDFs with graphical drawings like this:

Then the machine shop has to re-draw it, or if it's a simple part made on a manual machine, it's good enough for the machinist to just make it.

Last month my boss paid ~$4KUSD for an annual subscription to **broken link removed** for me to use. That's a mammoth package including AutoCAD, AutoCAD Electrical, Inventor, and a few more suites. I'm totally lost in there. I need to attend some classroom training but I don't have time. So far I've only learned enough to get by; I still do all my designs in Sketchup, but now I use a 3rd party plugin to export to *.STL, which I import into Inventor, and then save in Inventor's native format. So far nobody has complained...

 

[Mikebits]

Hey, thanks. Yeah I made the drawings in Sketchup. It's the only tool I know, and that's a problem. When it comes time to have these parts made, machine shops are accustomed to having CAD files submitted in formats that translate to their CAM software to be more-or-less directly loaded into their CNC machines. Sketchup doesn't do that. Sketchup is for hobbyists. Solidworks and Autodesk are what the industry uses, and they play nice with the machines. In the past I have had to submit my designs as PDFs with graphical drawings like this:
View attachment 98581
Then the machine shop has to re-draw it, or if it's a simple part made on a manual machine, it's good enough for the machinist to just make it.

Last month my boss paid ~$4KUSD for an annual subscription to **broken link removed** for me to use. That's a mammoth package including AutoCAD, AutoCAD Electrical, Inventor, and a few more suites. I'm totally lost in there. I need to attend some classroom training but I don't have time. So far I've only learned enough to get by; I still do all my designs in Sketchup, but now I use a 3rd party plugin to export to *.STL, which I import into Inventor, and then save in Inventor's native format. So far nobody has complained...

Have you checked out Design Spark Mechanical (free tool). http://www.rs-online.com/designspark/electronics/eng/page/mechanical

Also, Solid works offers a student version greatly discounted to military veterans (about $20 USD).
To qualify for the discount, you have to fill out an online verification form and submit your DD-214. More info here:
**broken link removed**

Party on

 

[dr pepper]

Bonfig are made from monkey metal, or as us uk'ns call it warmetal, in other words cheese, the slightest load and they fall to bits.
I've seen a fairly large industrial gearbox filled with 100 hydraulic oil (in fact it still is) due to a numpty boss and its been ok for a couple of years hard use.

 

[strantor]

Okay guys, for anyone who was speculating about the difference in current draw between an air-filled motor and an oil-filled motor, the results are in.

Out of the box, the motor plus gear box combo drew 1.94 amps no load. The motor had sealed bearings, a plastic impeller on the shaft on the inside to circulate air, and it had those fins on the rotor. The gearbox was one half full with 460 weight gear molasses.

After removing the plastic impeller, machining the rotor down, installing the stator and rotor inside my new subsea enclosure with open bearings, and emptying the gearbox (totally dry) it drew 1.76 amps.

After filling the entire motor and gearbox full of iso 32 hydraulic fluid it drew 1.65 amps.

So the drag of oil on the rotor is not enough to overcome the benefit of having lubricated bearings. I guess it's barely any drag at all on the rotor.

 

[JimB]

Thank you for the feedback, that is interesting.

Do you have a hyperbaric chamber handy?
It would be interesting to see if the running current changed when the thing was subject to seabed pressure.
Just sitting here I don't see why there would be a significant change, but that is one of those things which is likely to turn around and bite you.

JimB

 

[strantor]

Thank you for the feedback, that is interesting.

Do you have a hyperbaric chamber handy?
It would be interesting to see if the running current changed when the thing was subject to seabed pressure.
Just sitting here I don't see why there would be a significant change, but that is one of those things which is likely to turn around and bite you.

JimB

Yes I have a test chamber and I hope to test it by friday. It will be tested to 450psi (~1000ft seawater). I have not tested under pressure yet because my bellows compensator was a failure. I have a new compensator design that should be ready by tomorrow.