working with mechanical seals to waterproof motors

[Erik102696]

i was wondering if anyone on here has worked with mechanical seals to waterproof the shafts of motors. i have been looking into this topic a little bit but there isn't much out there in way of using theses seals for something like waterproofing a motor. i have seen them used on things like big pumps but i haven't seen them scaled down like this. i have one company that i am in contact with and i am hoping that they could shed some light on this subject. but if any of you have worked with anything like this for your motors please let me know.

thanks
erik wirtz

[Erik102696]

so really no one has worked with mechanical seals?? . thats a major surprise. i would have thought that someone out of the 50 that looked at this would have done something. what have you guys done in the past to water proof motors?

[a_shorething]

Many don't seal the motors. Others seal the coils of the motor only.

The cost of motors and ease of replacement basically means that anything that costs more than 2 or 3x the cost of a motor is not really justified.

I'm working on a magnetic coupler but the time and materials need to be below that price point listed above or else it's just easier to swap out a used motor for a new one, you know?

[rossrov]

Hi Erik. Ha Ha! Responses seem to be very shy on the forum, but I guess if one looks at the total number of users online compared to other forums like then probably not surprising. Fairly specialized interest after all, and alot of views are from people who are not members, so cannot post comments.... Personally i would like to see alot more activity and responses here.

The seal you are referring to has two faces, one fixed, the other rotating, with a spring pressing them together, am I right? Considered for hobby ROV but no, have not tried to source a miniature version. I am using the pressure-compensated (oil-filled) approach with a common shaft seal of the type as used on outboard motors and a million or so other things. Not many places stock the small diameters it seems but you can internet search them out easy enough

Brushed motors: Bilge pump motor "cartridge" for limited depth, or magnetic coupling
Brushless motors: Oil-filled pressure compensated or magnetic coupling

Ross

[Erik102696]

thanks for the responses. russ the depth that i'm going to working in is a max of 14 feet in a pool. do you think that a normal shaft seal would work. i dont really want to fill up the motor housing with oil or anything. then it just gets messy lol.

[rossrov]

I do not have any experience with shaft seals without pressure compensation, bilge pump motors being just that, but if you do a forum search for "bilge pump" you can find out what others have done, and how well or otherwise they worked at the depth you require.

Some of my own thoughts: Bilge pumps are designed to work with the shaft vertical and the seal/exit pointing down, and only in a few inches of water. I'm guessing that the brushes are at the top end of the motor, so small amounts of water that may leak in are less likely to have an immediate effect on the brushes and commutator. A minimal ROV usually has at least 2 motors with the shafts horizontal, so any water that gets past the seal will be more of a problem, and not able to leak back out of the seal. Another issue pointed out elsewhere on the forum is that with increasing depth the seal is pressed harder against the shaft, causing friction and wear.

[scubersteve]

I have just ordered some turnigy dst700 motors and some small seals.
I am going to experiment with waterproofing them...at least for pool depth. i.e. MATE competition.
May be totally useless for real-world purposes, but may help you out.
If it works out, I'll post how-to pics.

[Erik102696]

That sounds like fun Steve. Thanks and I hope that it works out. Where did you get the seals from?

[sthone]

You should be fine with just using small seals in a pool environment. I've done a few tests using small motorcycle oil seals with good results. I've even tested the seals (think they are just lip seals) in bilge pumps to a simulated depth of about 200'. And while they didn't leak at all I did have some problems with the added drag of the seals on the shaft that the pressure caused. See the bottom of THIS PAGE for more on those tests.

The oil seals I tried can be see HERE I never got around to pressuring testing these but I feel they would fine.

-Steve

[scubersteve]

That sounds like fun Steve. Thanks and I hope that it works out. Where did you get the seals from?

I'm using U-cup seals from The O-Ring Store. I doubt they would withstand much pressure, but they should work in the pool. Right now I'm waiting for a few more things to come in the mail, but I hope to get started on it this weekend.