Gearing a micro motor to retain waterproof seal

[MacWynn]

Hello all....

1st off I am a product designer and not an engineer, I apologize in advance to those that might be offended at that. Wish I had gone to engineering school. 20 years ago.

Question: I have an invention where the problem I need to solve is most closely related (I think) to an RC boat micro motor and propellor assembly. How is the gearing and housing done to get the maximum power to the shaft/propellor and yet keep the motor housing water tight?

Any help in that regard would be greatly appreciated, and yes, a toy rc boat purchase and disassembly may very well be in my future but I thought I would try a non-destructive approach here first.

Thanks to any who can help or point me in the right direction info wise.

MacWynn

 

[MikeHalloran]

1. Keep the motor above the water level, and use a flex shaft.

2. If you must submerge the motor, use a small shaft, careful assembly, good grease, maybe double seals, and leave a small sump under the motor sufficient to catch a few drops of water, which may be enough to delay the motor's inevitable death.

Careful assembly probably includes some kind of temporary guard over the keyway or flat in the shaft, to help prevent the shaft from cutting the seals.





Mike Halloran
Pembroke Pines, FL, USA

 

[MacWynn]

Thanks for the input Mike.

I guess the shaft assembly is where I am having issues understanding and would love to see a good example.

FOr this product the motor can be completely separate from the main shaft that needs to spin with the exception of course of the connection between the shaft and the moror's drive shaft. Using gears and so on may seem obvious but keeping the part that needs to be kept dry from the parts that will be submerged is where I am running into the lack of knowledge.

If it would help I can draw up an example of the area and how it would need to work.

Thanks!

MacWynn

 

[MikeHalloran]

Sometimes a good drawing of the problem can lead you to the solution, so go ahead.


Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

A greased o-ring or lip seal would be used on the shaft. Lip seal have less friction and therefore generate less heat but the are more expensive.

 

[MacWynn]

Thanks both of you for the help. Just knowing what to call certain parts is where I am, which makes me feel so S-M-R-T smart.

Here is a VERY basic diagram of what I am aiming to accomplish. The "Mystery Zone" is where I need the help, a water barrier while still allowing maximaximum torque/rpm's to spin the shaft from the motor is what I am flummoxed by.

Thoughts?

Thanks again!

MW

 

[MacWynn]

The other thing I Wanted to mention too is that the shaft would be going into something that would later be consumed by a person so it would need to be "clean" in that respect too. So I am assuming a flex shaft would not be appropriate, correct?

MW

 

[MikeHalloran]

Now it's starting to look like a natural application for a mag-drive.

Or maybe a wobble drive (think shiatsu massager).

Either way, the water is kept below an impermeable diaphragm.



Mike Halloran
Pembroke Pines, FL, USA

 

[MacWynn]

Mike,

Thanks, your suggestions so far at least are leading me to learn more about different types of engineering solution,s and learning is always a good thing. DId some Google image searches for mag-drives and then went to the sites and on cursory glance all of the hits returned were for mag-drive pumps, and I am not sure if that is the right direction, as I do not know how a pump would translate into spinning motion for a shaft with basically a propellor on the end to spin the liquid.

Again sorry to be so arcane in my details (or lack thereof) but this idea is too good to spill more info on to be slightly punny.

Is there a manufacturer you could maybe point me in the proper direction of? a Micro Motor mag-drive about two inches in length and able to be driven by two AA's (more if absolutely necessary for torque/rpm's) is the ideal solution.

I am chomping at the bit to get to design stage but I am S M R T enough to know to get the parts semi-right first.

Thank you for even bothering to answer this artist playing engineer.

MW

 

[MacWynn]

What to Look For?!?!?

Still looking the micro motor route until otherwise convinced that is not the way to go, but am also running into the cost Q's and trying to get some base idea of how much different micro motors cost and why, quality and purposes being high on the reasons list I am sure.

Like I am looking at one series that seems as if it might be perfect but I am unsure as to the cost even in a ballpark way, and don't want to waste poeple's time if I don't have to.....

http://www.telcointercon.com/DC-Coreless-Motor-id72.html

That's one that seems to be good size to power ratio and battery wise, btu like with much of this I am at best taking semi-educated guesses.

Thoughts?

If you say go to engineering school I agree. After I make a million bux with this thing.

MW

 

[israelkk]

You can use a magnetic coupling between the motor and the propeller (similar to washing machines pump). The propeller (molded in plastic) to stir the liquid will be inside the liquid with two magnets assembled inside it.

The motor can be out of the liquid container (made of plastic) and the motor will rotate two or more magnets attached to its shaft. The magnetic force/filed between the magnets attached to the motor and the magnets in the propeller will drive the propeller when the motor shaft rotates.

A motor to start with can be the same motor used in ellectric tooth brush which is drived by one AA battery.

 

[MacWynn]

Israel,

That is a very interesting way to go about it, and would probably work great, but I am unsure whether that solution would have enough torque and RPM's to do the job I need it to do.

In a situation where I could use a motor with two AA batteries and the motor could be 1.5 or even larger inches, what kind of force could I get?

I know there are tons of variables and without the actual use being proferred it's hard but the RC boat concept again is most similar in force needed.

Not a big RC boat but a semi-fasat little one.

MW