A different form of jet drive... - RC Groups
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Apr 12, 2017, 08:02 PM
Just Plane Nutts
AirDOGGe's Avatar
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A different form of jet drive...


(Edited for corrections)

I stumbled across a unique form of marine jet propulsion. Most likely no benefit for our RC boats, but I still find it fascinating to review. After some deeper research and photo hunting, I decided to share what I discovered with my fellow RCGroup members.

This Russian submarine looks rather conventional in this photo...





But in drydock it's unusual propulsion feature stands out. The sub has a jet drive with dual impellers.

The man standing on the scaffolding gives a great perspective of the size of this unit!






Here's another angle. Water is pulled into a gap in front of a shroud circling the circumference of the hull, and ejected out the rear nozzle.





This shot was taken after the nozzle and rear impeller was removed. A stator/bearing housing is now visible on the end of the vessel.





And further into disassembly, we see the middle stator housing resting on the ground and the foremos impeller is now visible.





And final close-up of the stator and front impeller. The driveshaft for the rear impeller is clearly visible, as is the bearing that resides in the now-removed stator.





Though the boat is well documented, I haven't found much detail about the drive itself. I can only assume it's design was to counter typical propeller emisions to minimize detection. This is what I do know about her:

Quote:
Russian submarine B-871 Alrosa is an diesel-electric Kilo-class submarine that joined the Soviet Fleet in 1990 and is active with the Russian Black Sea Fleet as of 2011.

Instead of a conventional propeller Alrosa uses a pump-jet propulsion system.

In June 2011 she took part in a NATO submarine rescue exercise, "Bold Monarch 2011", the first Russian submarine ever to do so.

I will add more info if I run across any. Enjoy.
Last edited by AirDOGGe; Apr 12, 2017 at 09:16 PM.
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Apr 12, 2017, 08:10 PM
Fast electric boats maybe
Jeffro Bodine's Avatar
Unique indeed AirDOGGe
Apr 12, 2017, 08:15 PM
Registered User
What a strange design!

What confuses me is that there's a rudder under the jet unit, (would not expect a rudder in the front) and the shape of the hull and con tower in that area don't match the appearances from the picture of the vessel underway.
Apr 12, 2017, 08:27 PM
Just Plane Nutts
AirDOGGe's Avatar
I see what you mean. It does look like a stern drive judging by the conning tower, despite what the text description said..... More investigations ahead for me...

Yep. Looks like I was mis-led. Text corrected. Thx for spotting that.
Last edited by AirDOGGe; Apr 12, 2017 at 09:03 PM.
Apr 12, 2017, 09:55 PM
Fast electric boats maybe
Jeffro Bodine's Avatar
I have been looking at the pics for some time now , I assume the intake is around the circumference of the vessel the 3rd pic shows a difference in diameter of the sub body compared to the diameter of drive unit that small space between the two is the intake I presume am I right
Apr 13, 2017, 01:57 AM
Registered User
Either way still very interesting. That is one seriously massive jet unit!
Apr 13, 2017, 04:05 AM
Fast electric boats maybe
Jeffro Bodine's Avatar
Got to looking on web cause it got my curiosity up on finding more about jet driven subs and found the US has them as well ,they are Virginia and Ohio class submarines but really can't find detailed specs of drives ,I suspect it's all classified stuff because it's government property and you know people like to take things and share with the highest bidder
Last edited by Jeffro Bodine; Apr 13, 2017 at 04:14 AM.
Apr 13, 2017, 04:53 AM
Fast electric boats maybe
Jeffro Bodine's Avatar
Found a couple more photos at different angles
Apr 13, 2017, 05:48 AM
Registered User
That's a cool looking sub. I always have appreciated Russian engineering - they do come up with some crazy things! The Lun-class Ekranoplan is one of my favourites.

Quote:
Originally Posted by Firehawk989
What a strange design!

What confuses me is that there's a rudder under the jet unit, (would not expect a rudder in the front) and the shape of the hull and con tower in that area don't match the appearances from the picture of the vessel underway.
I would imagine having a rudder separate from the jet allows you to steer off power.
Apr 13, 2017, 10:50 AM
Registered User
Talking of Russian design & engineering but not quite a boat or water jet. But the incredible 300 mph Ekranaplane just a few feet off the water, straight out of the cold war days.
Apr 13, 2017, 12:51 PM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by Cobalt6700

I would imagine having a rudder separate from the jet allows you to steer off power.
In this case, the nozzle is fixed, so a rudder is a requirement.

Since they only made one jet-sub, I suppose they found no advantage to it for one reason or another.
Apr 14, 2017, 03:17 PM
Registered User
unusual_rc's Avatar
I know the Russians did investigate the possibility of a parts-less jet drive: only a tube with electric coils around it. Because salt water is conductive it would move without an impeller.

As far I as know the amount of power necessary to get it even moving in the first place made np sense. Very inefficient, but if it would work...no sound!



I guess this drive is for low sound output too. The skin of the subs is some kind of rubber compound usually.
Apr 14, 2017, 04:15 PM
Sea Dragon-Lover
Umi_Ryuzuki's Avatar
The Yamato 1 built by Mitsubishi, in Japan, used magnetohydrodynamic drives.

https://en.wikipedia.org/wiki/Yamato_1

http://lifeform.coomaru.com/hoka/023/

It was not very efficient.

http://www.evilmadscientist.com/2006...ic-propulsion/
Apr 15, 2017, 12:19 AM
Registered User
unusual_rc's Avatar
Yes, that is exactly what they were trying to do.

I remember this Japanese vessel from an old tech magazine.

The speed sounds enough for a sub silent "drive". Who knows it has been implemented already
Last edited by unusual_rc; Apr 15, 2017 at 12:25 AM.
May 11, 2017, 04:59 PM
Registered User
I believe the boat in the pictures is a Kilo class with an experimental pump-jet. Pump-jets work differently than jet drives, but are extremely quiet, see the Seawolf class and the Virginia class boat the US builds. I have a 1/48 Seawolf with a pump-jet that David Merriman built for me. It is amazingly efficient With an rpm range of 20-650 it puts out approximately 30 lbs of thrust at full throttle. I need alot of room to run.
I amm always puzzled that those working on jet drive are using such high rpms. I realize scale factors effect the output, but it seems that lower rpms would allow more pitch and less power.
My ramble...


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