"Duo-Prop" Inboard Transmission ????

[ATMHC]

I heard that an Italian company recently introduced an inboard transmission that puts two counter rotating props on a single shaft. If anyone can help me verify this and help me find this company I will be very grateful.

[Nojjan]

Its actually a Swedish company and the product is called IPS !!! ;-)

[ATMHC]

Re: Nojjan's reply:

"Its actually a Swedish company and the product is called IPS !!! ;-)"

Wrong !

I'm talking about an 'INBOARD TRANSMISSION" which could be used with a single engine / traditional shaft layout with one set of counter rotating props just forward of a rudder.. NOT the Volvo IPS which is an articulated pod drive which only works in twin engine installations...

[Nojjan]

Sorry, it was a small and apparently not so clever joke, hence the symbols ;-) , wink, wink !

Anywho, the duo-prop has been tried on inboard configurations before, not sure what company (maybe it was ZF Padova). The problem was that appendage drag was increased due to thicker over-all diameter of the outer "sleve/shaft" as well as bigger bossings on P-brackets etc. Also, the complexity of it all made the cost too high. If this new system that you refer to is more efficient, cheaper and easier to install I am sure it will become popular, I have my doubts though.

[KnottyBuoyz]

http://www.boatdesign.net/forum/arch...hp/t-1038.html

dual prop shaft ?

[Pericles]

ATMHC

Explore the Schottel site here. http://www.schottel.de/eng/r_produkt...uebersicht.htm

Just about every propulsion system possible except http://www.yellowfin.com/VSDTechnology.asp

Good luck.

Pericles

[brian eiland]

Originally Posted by ATMHC

I heard that an Italian company recently introduced an inboard transmission that puts two counter rotating props on a single shaft. If anyone can help me verify this and help me find this company I will be very grateful.

Not exactly sure what you mean by 'transmission' and 'single shaft'??

If you have a duo prop arrangement on a single rotation center I believe you MUST have concentric shafts...that's two shafts, not a single.

Could a 'transmission' be much simiplier than one gear driving two pinion gears as in most outdrives?

Or maybe you might have a look at these duo-chain drive I propose here:
http://www.runningtideyachts.com/dynarig/Tennant_Hull_V_ChainDrive.php

[FAST FRED]

The counter rotating props (any brand) are claimed to get 30% lower fuel burn .

This is nice for a boat designed to run at a relativly fixed speed where the props can be optomized for the vessel.

I have read about a "pre swirler" that was claimed to swirl the water before the prop, making the prop more efficient.

Sorta like the Stators in a jet , but forward, not aft of the prop.

Anyone have info on this?

Am convinced that a 2 speed tranny and adjustable pitch prop would allow best engine loading at the cuise speeds I am willing to pay for.

But the more efficent the better!! 20K 5nmpg

FF