Gearboxes

I need help to find any alternatives for a simple small gear box that has FORWARD / NEUTRAL / REVERSE 1:1 ratio 10 hp@2500 rpm. The only example i find is ZF6M, but seems expensive.:?:

 

How about just using a velvet drive? They are always plentiful on ebay.

 

Its quite likely the Zf will be quite happy directing power with eiether direction.

ZF's usually are.

The BW velvet drive does not,-- reverse rotation should be only used temporary, as reverse is. Its prefered rotation will be on the plate.

 

Frosty, why is that so? I'm just asking for my own knowledge.

 

gearbox

sir
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for gearbox manufactured pdf files.(YERLİ ŞANZIMAN İMALATÇILARI )
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Oktay Çemberci

 

The Velvet drive will handle your needs if you all you want to use it as is a primary forward transmission. Although at 10 hp a full time reverse would not present a problem other than ratio.

The Velvet drive uses a planetary and a single clutch disc for reverse so the forward is 1:1 but the reverse is 1.5:1 thus the Velvet drive is not intended as a full time reverse transmission, but 10 hp is very small and would not present a problem other than ratio.

http://www.velvetdrive.com/techinfo/V7172/V7172pg1.pdf

 

Zf also have a different rotation ration but much smaller say 2.5---2.58. I honestly don't know exactly why that is but I know it gives me a bit of trouble running two counter rotation props.

Well not exactly trouble but if both engines are the same the roosters are different . If I set the roosters the same stbd engine is 200RPM down, and I notice a fuel consumption difference.

ZF dont call it forward and reverse they refer to it as rotation A&B

 

All standard "Marine Gears" are full forward/full Reverse meaning they can be run full time in either direction.

ZF, Twin Disc, Nico, etc. are and have been full time either direction for many many years. They also have the same ratio in both directions.

 

Not exactly the same.

http://www.simplicity-marine.com/ZF/ZF63A/Technical.htm

Like I said close but not exactly the same.

I have heard of some owners tweaking the pitch to compensate.

It is slight, some owners don't notice it

 

Hi Frosty,

I was just wondering why you don't turn one of those gearboxes around? Wouldn't that give both props the same RPM?

 

Yes it would but I need counter rotation as all twin screws do especially surface props. I would be going side ways!!!!

 

Apparently you're running one gearbox in "Rotation A" and the other in "Rotation B" in order to spin your counter-rotating props. Is this correct?

If so, I meant to simply to turn one gearbox around (so the input becomes the output on that box) then run them both in "Rotation A". Wouldn't this work to get your engines running the same RPM when your props are also running the same RPM?

 

Theoretically yes, totally ignoring the pump being on the intake shaft and that the gearbox just would not fit that way round.

Take a look at a picture of one.

 

No need to see the pictures, I understand there may be physical limitations in a particular installation. But if there weren't ...

 

But if it were'nt? then it would be a hypothetical question to which I dont know. I suppose so.