Brushless motor and propellor combined

While in Europe, I came across this incredible powerful up to 8,5 Kw Brushless motor and propeller combined. It was just a pity that due to low production volumes, the price was a little too high. The center, which is the propeller and has the magnets mounted on a ceramic part, also function as the bearing. The lubrication is water, seawater, any water. The efficiency of the system is very high. It is made in de Heeg, Holland.

 

If water is the lubricant, I'd think it would be susceptible to sand and silt and mud or whatever is in the water, and wear out quickly.

 

What I could see, was that the rotor/propellor had a seal and sand, etc was not able to enter the bearings. They worked 10 years to get a fully functional and performing production "engine".
Bert

 

Looks like a modified Alstom/Schilling thruster from the late 1980's. Still didn't fix the blade shape, just copied. Schilling thrusters had bearing problems, but more from balance/fabrication than lubrication. Here is the latest patent showing how the lubrication method http://www.freepatentsonline.com/6692319.html

Not more efficient ( i.e. power in/thrust out because of ring drag) than an open wheel, just smaller tube as compared to a center drive because of less blockage (i.e. more effective disk area). Ring drives have thier uses, but absolute efficiency is not it.

 

Yes you may be right. There are similarities with the patent. However the patent does not mention the ceramic bearing, Maybe they have come up with slight differences, which may makes something working better. Often an improvement of a patent means it works and is marketable better than the original concept.
Bert

 

If I remember correctly, Voith marine engineering in Rostock, Germany claims they were the first with a production-ready shaftless thruster.
The design is challenging, just one moving part, no maintenance etc. But the large bearing surface must be kept immaculately clean, seals on both sides and a small aperture for water to enter the bearing gap. No standard parts you can buy off the shelf, everything has to be specially made, which makes it an expensive project.

Even a multinational like Voith decided not to enter the production phase yet.

 

What is interesting, I have never seen a more than 1 KW thruster build in this way, but to have a 8,5 KW motor for normal propulsion is in my view a winner. The place did not look to me, that they could handle large production quantities and it may well be that they have been imported from Germany. Who knows. Or maybe they solved the bearing problem, who knows again. They were not disclosing too much info, other than I got 2 leaflets.
Bert

 

Apart the possibility to steer each prop individually and act like azimuth thrusters, what other advantages does this configuration offer? That particular ring looks too fat and draggy at higher flow speeds, more draggy than a conventional prop on a central shaft - though this might be just my impression. Any efficiency data, or Kt & Kq curves available?
If the ring increases drag at higher speeds (as it inevitably does imho), it would mean that this product is intended mainly for low-speed or bollard-pull uses (tugs and similar). But then what is the advantage over much simpler and proven shrouded azimuth thrusters?
I recall that back in my student days I have had exactly the same idea, but after doing some math I had abandoned it because there was no evidence of any increase of efficiency, while there were evidence of many mechanical problems brought by this solution, as have been pointed out by previous posters. Don't tell me that I had abandoned it too quickly?

 

Maybe you would like to take a look at Brians thread started in 2005?
http://www.boatdesign.net/forums/propulsion/exciting-new-eps-thruster-propulsion-9432.html

Compactness is certainly a bonus especially in something retractable.
Perhaps one of the most note worthy advantages I have witnessed is the RIM drives ability not to get tangled by a rope. Although not all rim drives share these props, some are more conventional looking with center thrust bearing to solve the issue.

http://www.oceanyachtsystems.co.uk/thrusters/rim-driven-thrusters

 

Aah I found the rope tangling one now. http://www.youtube.com/watch?v=No0pzwOLabk

 

How much thrust can something like that handle? Power alone means very little as a specification.

 

Both Voith and OYS give thrust along with power specs.

 

Hubless props have also been used on some computer fans for years

If nothing else, maybe it will further the technology for jet drives. My biggest question is how they deal with mixing water and electricity? As for bearings, the obvious answer is magnetic levitation (no surfaces touching at all, so no lube/bearings needed), but not sure how that would work with an electric motor that relies on magnetism anyway...

I've always thought hubless drives would be practical on an electrical terrestrial vehicle, especially a four-wheel-drive automobile/truck. With each wheel having its own motor (the rim being integral to the motor), you can do away with driveline components and possibly have a more robust 4wd system. All motors, of course, would be computer-controlled drive-by-wire to avoid wheel slippage, unintended acceleration, better cornering, etc.

Applying that to an aquatic environment, pontoon boats would be much more maneuverable with a small motor at each corner of the boat. Yes, this can be done with trolling motors, but the hubless motors are much more elegant, IMHO.

For the larger apps, best use I see is as a bow thruster.

 

Hi daiquiri,
Attached the leaflet with the thrust information. Guys, here I was jumping like a little baby that I found something which could be a backup in case I do not have enough thrust with what I have fiddled together. I think 130 Kg/1275N is not bad, but tell me if that is not enough to replace a 10 Hp smelly diesel engine. At 10,5 Kg it can be nicely lifted up and down a chamber as per leaflet. Daiquiri, I am fed up with those oil sheiks holding everybody at ransom. I wish that more money is being put into electrics. Some 35 years ago I was accidental at a very top secret development of a German military vehicle using brushless motor technology. The fellow who forgot to tell the developers, that I was with Siemens South Africa and not with Siemens Germany received quite a knock. Although I had local security clearance.
Now 35 years later we still have not seen much progress. I wished that you were able to convince your Professor at that time to help you to patent that idea you had.
But probably you would have sold it out to the oil sheiks. They have the money today and most of the patents
Bert

 

Sorry, the file size was too large, here it is in reduced format
Bert