Propeller key

[rotrax]

I wonder if they use the key because they are not always 100% sure about the integrity of the tapers, or perhaps a 1 in 10 taper is a bit "marginal" so the key is a sort of belt and braces?

My V8 Jaguar has no key on the four camshaft pinions and they are transmitting far more power than a auxiliary marine engine and against a much higher resistive force at much higher revs. However, I reckon that the taper is much shallower than 10:1.

Richard

Interesting. That is not an engine I am familiar with.

No doubt the manual will give instuctions for correct valve timing. I can imagine locking devices to hold the camshafts in the correct place while the pinions are tightened. Avoiding movement while tightening would be critical I imagine. It certainly is with Magneto timing.

Our Island Packet prop uses a long shallow taper, not the much shorter and steeper taper found on many European vessels. Sounds like your Jag camshafts are similar.

The resistive force of valve springs and valve gear is, as you say, quite high. Fitting modern-well, modernish, they had to be eight valve ones- Porche valve springs in place of the old tech ones fitted as OE in my 500 JAP Longtrack engine saved 2.3 BHP on a Heenan and Froud dynamometer. The engine could be easily turned by hand using the engine sprocket carrier and with the plug removed using the Porche springs, but was impossible with the OE JAP springs.

 

[RichardS]

Interesting. That is not an engine I am familiar with.

No doubt the manual will give instuctions for correct valve timing. I can imagine locking devices to hold the camshafts in the correct place while the pinions are tightened. Avoiding movement while tightening would be critical I imagine. It certainly is with Magneto timing.

That's exactly right. Both the camshafts on each side have a "flat" machined into them. The cam-setting tool bolts down across the cambox with a straight edge across the two flats. The valve timing is then correct and the cam sprocket can be tightened up.

I suppose that if one was an engine tuner one could make up a tool with the straight edge at a known different angle and independently vary the inlet and exhaust valve timing whereas with a keyed camshaft this would require different shafts or sprockets, I guess, unless one was looking for a step-change by altering the sprocket engagement with the camchain.

Richard

 

[rotrax]

That's exactly right. Both the camshafts on each side have a "flat" machined into them. The cam-setting tool bolts down across the cambox with a straight edge across the two flats. The valve timing is then correct and the cam sprocket can be tightened up.

I suppose that if one was an engine tuner one could make up a tool with the straight edge at a known different angle and independently vary the inlet and exhaust valve timing whereas with a keyed camshaft this would require different shafts or sprockets, I guess, unless one was looking for a step-change by altering the sprocket engagement with the camchain.

Richard

I suspect what a tuner would do is make new sprockets up with slotted fixing holes and machine/fabricate the existing sprockets to recieve them. This is common practice on twin cam motorcycle engines. The slotted fixing holes will allow HT bolts to be used to fix the timing where the tuner wants-or thinks he wants-it. Once the optimum position is found, another hole and matching thread-not slotted this time-will fix it in position. Timing of each camshaft can be altered by the amount the slotted holes allow.

Big trouble can occur if the fastning bolts are not drilled and lockwired.

Ask me how I know......................

 

[STUART P]

HI Guys
Ive got a fairline cornich my woodruff key as gone on one of my propellers , i have taken the other one off to check and measure the size,
Do you know if there is any one local who supply the keys and castle nuts .
Keys sizes approx 9mmx 9mm (3/8) rounded both ends , the shafts are 1.5 inch.
thanks Stuart

 

[VicS]

HI Guys
Ive got a fairline cornich my woodruff key as gone on one of my propellers , i have taken the other one off to check and measure the size,
Do you know if there is any one local who supply the keys and castle nuts .
Keys sizes approx 9mmx 9mm (3/8) rounded both ends , the shafts are 1.5 inch.
thanks Stuart

Whre is local ? Your profie does not give your location.

BTW it would have been better to have started your own new topic rather than adding your question to an old thread

 

[earlybird]

Description is for a feather key, which is parallel in depth. Woodruff keys are approx. semi-circular in profile

 

[mattonthesea]

Back on Topic:

Advice given to me by several engineers was to clean the taper very carefully and NOT to grease it. As mentioned earlier the taper join between the prop and shaft is the main/total force transfer; grease will both loosen that and provide a thin, and potentially self-removing, layer between the two surfaced. A while later and the prop can shake loose.

 

[Heckler]

Back on Topic:

Advice given to me by several engineers was to clean the taper very carefully and NOT to grease it. As mentioned earlier the taper join between the prop and shaft is the main/total force transfer; grease will both loosen that and provide a thin, and potentially self-removing, layer between the two surfaced. A while later and the prop can shake loose.

Stick to electrics!