Adjustable pitch propellor question

[nairda96]

I have an Ex royal navy mobo which is fitted with a Kitchen steering nozzle and a composite
adjustable pitch propeller, The steering nozzle is pinned of and fitted with an additional rudder
so it is no longer adjustable but I have no idea about the prop and how it work or adjusts,
Has anybody any experience with these, Its just out of curiosity really and to save me ripping
it to bits jus to find out, Thanks

 

[charles_reed]

At the last count there were some 18 manufacturers of different variable-pitch marine propellers.

All have different methods of control.

The probability is that it's an Hunstedt - the best known model having a central rod down the centre of the prop-shaft with a cast-iron box at the inboard end and an handwheel which you wind to vary the pitch.

I'm afraid you'll have to be more specific with a model/name.

 

[Nigel_Ward]

Apart from the one described by Charles Reed, Hundested also used to make an adjustable pitch propeller which was adjusted at the propeller boss.

The boat had to be beached then a crank handle of some sort inserted into the boss.

This type was used for some small fishing boats, which were often hauled out on a beach. The idea being that if the boat used different fishing methods seasonally the pitch could be altered to suit.

 

[nairda96]

Thanks for that info, It would have been fitted in the late 70's ,

Not sure if this pic will work, There is a large flat head screw on the end of the center cone,
The coupling appears to be pretty standard on the gearbox end,

 

[nairda96]

Can anyone tell anymore from the pic ?

 

[westernman]

Apart from the one described by Charles Reed, Hundested also used to make an adjustable pitch propeller which was adjusted at the propeller boss.

The boat had to be beached then a crank handle of some sort inserted into the boss.

This type was used for some small fishing boats, which were often hauled out on a beach. The idea being that if the boat used different fishing methods seasonally the pitch could be altered to suit.

That is common with many yacht propellers. I have a feathering J Prop where the pitch can be changed. No tools required - just pull the spring loaded cap back a bit and turn it a little one way or the other. You could do it by diving down to it with snorkelling gear when anchored in a calm bay in the med in summer.....

But, by the looks of it, what is in the picture is not an adjustable pitch propeller (like what I have) but a real variable pitch one.

In these boats the engine usually controlled by a governor. The engine speed is set by a lever and a wheel is turned to vary the pitch. Usually the pitch can go both ways - i.e. the boat can be made to reverse by simply changing the propeller pitch.

 

[nairda96]

Thanks Micheal, But on mine originally the nozzle could be closed or opened to take her fore and aft with out changing the prop direction, I read somewhere that the a variable pitch prop was used with the kitchen nozzle as with the kort nozzles to make it efficient at different speeds, the nozzle greatly inceases pulling power at low speed but causes drag at higher speeds so I believe they compensate by using a variable prop, just don't know how in works or how to take it off for that matter, will it go to bits or change pitch it I take the screw out of the end of it

 

[Tranona]

Do you have a normal FNR gearbox? Is the shaft solid or does it have a sleeve which moves back and forwards? Looks to me like it is an adjustable pitch prop, not a variable pitch as fo the latter you would clearly see some mechanism , either a lever or a wheel to alter the pitch when you are running.

 

[nairda96]

The navy sold the boat without an engine so it was later fitted with a PRM500 box, The coupling looks like a standard flange bolted to a (roughly) 8" diameter by 4" long what looks to be a metal drum instead of a flexible coupling, Presume it just a spacer/adapter. If there was an internal control I assume it has been done away with, I have never had the shaft off so don't know if it is a solid shaft or not

 

[SHUG]

The photo looks like an early Brunton self-pitching propellor fitted into a fabricated tunnel.
No idea how it comes apart. Interested to know what it actually is.

 

[Tranona]

The navy sold the boat without an engine so it was later fitted with a PRM500 box, The coupling looks like a standard flange bolted to a (roughly) 8" diameter by 4" long what looks to be a metal drum instead of a flexible coupling, Presume it just a spacer/adapter. If there was an internal control I assume it has been done away with, I have never had the shaft off so don't know if it is a solid shaft or not

Then I think it is just an adjustable pitch prop. Do the blades swivel like a feathering sailing prop? Think if you take that end cap off you will find some form of adjustable stops inside for changing the blade angle and thus the pitch.

 

[nairda96]

Then I think it is just an adjustable pitch prop. Do the blades swivel like a feathering sailing prop? Think if you take that end cap off you will find some form of adjustable stops inside for changing the blade angle and thus the pitch.

I think so to. I reckon the end cap probably unscrews and there is some way of adjusting it inside, It does not feather, they are solid in that position and I see no reason for it to be reversible from on board as the nozzle is capable of that.

SHUG : the tunnel is in fact a Kitchen's Patent Reversing Rudder http://en.wikipedia.org/wiki/Kitchen_rudder
Its a bronze nozzle which can be closed to reverse or used as a stern truster, the steel rudder is later addition and only really there to fix the nozzle in position as the boat now has a reversing gearbox.

 

[nairda96]

Found a few words and numbers on the hub today, Very difficult to make out but what I could see looks like
19334
19.75 x 1725
****ford & co
fiasa
port
LH
Words could be wrong or part missing but thats how it read to me,