Lapping prop to shaft
- Thread starter zoidberg
- Start date
<152587>
...
Take a guess.
(Clue ..... it's not the engine in post #13)
Richard
Think you are missing the point here. If the cams need 300 hp to turn them, then the total out put of the motor must be well in excess of that. The fact is that if the engine is producing 300 hp then it does not transmit 300 hp to rotate the cams.
lw395
Well-Known Member
The key is mostly there to avoid spinning the taper and ruining it during assembly. The key is not able to transmit very much torque on its own.
Lapping should not be necessary, and can have the wrong effect if the shape of the taper is lost.
The main thing is to rmove any damage from the prop bore which might prevent it sitting properly on the taper.
The nut should be correctly tight, but make sure the washer is bearing on the prop and not bottoming onto the shaft.
Correctly fitted props generally show no sign of leaving the shaft, even with the nut removed.
Morse tapers are steel-on-steel, with a lot less tension on the drawbar than you get from a 3/4 inch nut or whatever. Different animal really.
RichardS
N/A
Errrrrr ..... does that sound like someone who could post the photo of his handiwork in post #13?
Richard
lw395
Well-Known Member
I've not watched the video ..... but can't you lap it in for a few minutes with fine valve grinding paste. If it's anything like engine valves after a few minutes you will see from the colour whether there is a problem or not and can carry on lapping until it looks right.
I lapped these valves in at the weekend and then poured in white spirit:
Richard
Needs more valves!
reeac
Well-Known Member
Must be a new design where the clutch/gearbox is driven off both camshafts ....sounds exciting.
earlybird
Well-Known Member
Not so. For a key of normal proportions, for a given torque, the shear-stress in a key is of similar order of magnitude to the maximum shear stress in the shaft, ( ie at the surface). The key should be able to carry the shaft torque without assistance from frictional grip of the taper.
I wouldn't be happy with a prop fitted without a key.
RichardS
N/A
Or one could be in neutral and blipping the throttle. Where do you think all those horses and torques are going then? :encouragement:
Richard
reeac
Well-Known Member
Well a fair proportion will be going to accelerate the crankshaft, pistons and flywheel and/or torque converter.
RichardS
N/A
Although, compared to the valve springs, those are all trivial loads. The engine can be turned over with one hand on the crank pulley once the cams are removed .... but once those 32 springs are in place it's a struggle to turn it over even with a 12 inch spanner. :ambivalence:
Richard
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macd
Well-Known Member
The springs give back much of the power applied to them. If they didn't, you'd be tripping over desmodromic engines in every race paddock.
Blipping the throttle won't give full power, or anything like it, unless applied against a sufficient load.
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vyv_cox
Well-Known Member
Whilst not exactly comparing apples with oranges, the vast majority of modern industrial rotating equipment such as pumps, compressors and turbines does not use keys and keyways. There is a long history of fatigue failures initiated at keyways. The equipment I have worked on, anything from pumps of 4-5 MW up to large gas turbines producing 90 MW, universally have tapered connections to their drives or driven equipment. The large ones are hydraulically applied, smaller ones with various bolted arrangements.
NorthUp
Well-Known Member
..and the tapers were probably lapped at first assembly
Richard S - please stop digging!
rogerthebodger
Well-Known Member
Vyv I agree with that as a mechanical design but when I was designing mechanical equipment of a more modest power usage parallel and tapers keys were the norm and not even using tapered shafts.
Non of the worm drive gearboxes had tapered shafts and either drive the coupling, sprocket or pulley either with a top fitted taper key or a side fitted parallel key.
This is the type of worm box we used
Also why id the motor coupling end of a boat prop shaft parallel and not tapered like the prop. It is subject to the same forces as the prop and if it became disconnected would be of a greater problem than just loosing the prop.
BTW the way the keyway was machined in the video was not the best. keyways in shafts should be machined on a vertical mill so you get round ends to hold the key in unlike the one in the vides that had keyway ends the tapered up to the shaft diameter.
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lw395
Well-Known Member
Fairly obviously, a parallel shaft at the engine end is convenient to use with a clamped-up split coupling. Which alloows for a little length adjustment. A similar split coupling at the prop end would be a poor solution for the hydrodynamics of the prop.
vyv_cox
Well-Known Member
Yes, of course. I don't think I have come across many tapered couplings in automotive applications. I was only pointing out that tapered couplings in very high power applications do not have keyways.
I have witnessed very many disassemblies of Solar gas turbines. The shaft between the compressor and turbine section is joined with a taper coupling. The guys doing the work used to love getting the owners/witnesses to be looking into the machine when they separated the two parts. It always went with a hell of a bang, amplified by the discs still inside the casing, producing a suitable reaction from the watchers. Such simple pleasures.
scottie
Well-Known Member
It was common to taper both ends on shafts and if the gearbox coupling allowed it to make them reversible in quality sterngear
It did mean that you had to measure accurately and wait for manufacturing but often short intermediate shafts would be used this also allowed gearbox removal
It did mean that you had to measure accurately and wait for manufacturing but often short intermediate shafts would be used this also allowed gearbox removal
scottie
Well-Known Member
Just as a trivial note Kelvin propellers never had keys or key ways but they stopped manufacturing last century
RichardS
N/A
If you Guys really think that this has been a serious discussion you really need to reset your humour compasses.
Re-visit post #24 and look carefully for any give-away smileys. :encouragement:
This afternoon's job was the removal of an entire wiring loom without breaking any connection behind the dashboard and only removing connectors where they actually interface with the final item. Find me another mechanic in Christendom who can do that in one afternoon and I'll say three Hail Marys. Now it all has to go back again.
Richard
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zoidberg
Well-Known Member
I wish I hadn't started this. That's next...
