Propshaft coupling advice

[Mei Mac]

You are a sensible person with obvious engineering knowledge.

Thanks for your kind words. It's hardly rocket science is it! More contact more friction more hold.

 

[jim.howes]

Thanks for your kind words. It's hardly rocket science is it! More contact more friction more hold.

They were not just kind words, it is a genuine appraisal of your abilities and your willingness to learn.

 

[rogerthebodger]

You are wrong it is not overkill to lap a coupling / propeller to a shaft it is the correct thing to do. Couplings and propellers rely on the taper to be a good fit(as in morse tapers)to stop them turning on the shaft the key/keyway is a secondary means of stopping the coupling / propeller from turning on the shaft.

Its interesting that in all my design engineering career we very rarely used a shaft taper in any power transmission equipment we always had a parallel shaft with either a fitted taper key or a parallel (side fitted key). This needed a way to locate the pulley/gear laterally onto the shaft.

We some times use a fenner taper lock bush to locate the pulley/gear.

We used many hundreds of worm gear boxes on all the conveyor we designed for the motor manufacture, coal /rock/sand belt conveyors and in floor conveyors for car/truck assembly

Some of the gearboxes we used were higher than me so quite big.

The shaft coupling on my boat is a R & D with a fenner taper lock bush the coupling end of my propshaft is parallel, it's only the prop end that has a taper to match the taper in the propeller.

Maybe tapers are needed on big container ships where you have several 10 of thousands of horse power and immense torque to transmit.

These props are hydraulically fitted without any key as with this reversing torque you can get key fretting.

But what do I know only being in mechanical design engineering for most of my life.

All these electric motors have parallel shafts

elctric motors shaft - Google Search

Even the small petrol engines have parallel shafts

Then you have the power transmission couplings.

shaft couplings - Google Search

 

[Mei Mac]

Its interesting that in all my design engineering career we very rarely used a shaft taper in any power transmission equipment we always had a parallel shaft with either a fitted taper key or a parallel (side fitted key). This needed a way to locate the pulley/gear laterally onto the shaft.

We some times use a fenner taper lock bush to locate the pulley/gear.

We used many hundreds of worm gear boxes on all the conveyor we designed for the motor manufacture, coal /rock/sand belt conveyors and in floor conveyors for car/truck assembly

Some of the gearboxes we used were higher than me so quite big.

The shaft coupling on my boat is a R & D with a fenner taper lock bush the coupling end of my propshaft is parallel, it's only the prop end that has a taper to match the taper in the propeller.

Maybe tapers are needed on big container ships where you have several 10 of thousands of horse power and immense torque to transmit.

These props are hydraulically fitted without any key as with this reversing torque you can get key fretting.

But what do I know only being in mechanical design engineering for most of my life.

All these electric motors have parallel shafts

elctric motors shaft - Google Search

Even the small petrol engines have parallel shafts

Then you have the power transmission couplings.

shaft couplings - Google Search

My situation was that I had a tapered shaft and a tapered coupling and didn't have much choice but to go with what I had. It wasn't an option to change to a straight shaft or even shorten the shaft I had.

I'll accept what you say about your experience with straight shafts and so on, but in the instances of tapers, it is good practice to lap them for a snug fit. I believe this is the point Jim was getting as. Any engineer will agree that a snug fitting is better than a loose/uneven one. I wouldn't call getting a really good fit an overkill. Similarly at the other end, like on your boat, it's important to have good fit between the prop shaft and prop.

 

[jim.howes]

Its interesting that in all my design engineering career we very rarely used a shaft taper in any power transmission equipment we always had a parallel shaft with either a fitted taper key or a parallel (side fitted key). This needed a way to locate the pulley/gear laterally onto the shaft.

We some times use a fenner taper lock bush to locate the pulley/gear.

We used many hundreds of worm gear boxes on all the conveyor we designed for the motor manufacture, coal /rock/sand belt conveyors and in floor conveyors for car/truck assembly

Some of the gearboxes we used were higher than me so quite big.

The shaft coupling on my boat is a R & D with a fenner taper lock bush the coupling end of my propshaft is parallel, it's only the prop end that has a taper to match the taper in the propeller.

Maybe tapers are needed on big container ships where you have several 10 of thousands of horse power and immense torque to transmit.

These props are hydraulically fitted without any key as with this reversing torque you can get key fretting.

But what do I know only being in mechanical design engineering for most of my life.

All these electric motors have parallel shafts

elctric motors shaft - Google Search

Even the small petrol engines have parallel shafts

Then you have the power transmission couplings.

shaft couplings - Google Search

I agree with what you say to a degree but my argument would be if you have a taper on a shaft the corresponding taper e.g. a Coupling should be quite an accurate fit to achieve the desired friction. I mentioned Morse tapers in my post they are a good example of a taper and both mating surfaces are ground finishes. Unlike you i am a practical man a fitter and turner all my adult life working in the marine industry and have fitted many propellers and couplings and haven't lost one yet.

 

[rogerthebodger]

My situation was that I had a tapered shaft and a tapered coupling and didn't have much choice but to go with what I had. It wasn't an option to change to a straight shaft or even shorten the shaft I had.

I'll accept what you say about your experience with straight shafts and so on, but in the instances of tapers, it is good practice to lap them for a snug fit. I believe this is the point Jim was getting as. Any engineer will agree that a snug fitting is better than a loose/uneven one. I wouldn't call getting a really good fit an overkill. Similarly at the other end, like on your boat, it's important to have good fit between the prop shaft and prop.

I would not even consider changing your existing set up. If it ain't broke don't fix it.

It was a response to jim.howes comment about a " Couplings and propellers rely on the taper to be a good fit" . My experience id that you can get good fit with parallel shafts.

Parallel shafts with the standard British Standard fits are what is normally used. Sometimes you may design a shrink fit or a press fit

Your issue is that the fit may not machined correctly as the taper could be different and thus could wobble on the shaft. With a parallel fit all you need is to ensure that the diameters are correct. Too close and the fit may be too tight and if the too loose could again wobble but not machined correctly. This could be machined out and pushed to the correct fit.

I had a new stainless propeller made and I took the current prop to the machinist to match the tapers that I just fitted with a parallel key and shaft nut.

When I had a propshaft nut made I took the whole propshaft to the machinist to make the nut correctly (to fit)

 

[scottie]

As the person suggesting lapping it was due to the coupling not fitting properly that I proposed it as an option

 

[rogerthebodger]

I agree with what you say to a degree but my argument would be if you have a taper on a shaft the corresponding taper e.g. a Coupling should be quite an accurate fit to achieve the desired friction. I mentioned Morse tapers in my post they are a good example of a taper and both mating surfaces are ground finishes. Unlike you i am a practical man a fitter and turner all my adult life working in the marine industry and have fitted many propellers and couplings and haven't lost one yet.

I have always wondered why a prop/ shaft taper was considered essential as the thrust on the shaft is in both directions so one way pushing the prop onto the shatf (fair enough) but in reverse pulling the prop off the shaft and so the possibility of losing the prop is greater.

Its therefore the prop nut that ensures the prop stays on. The the prop nut was not fitted correctly of cane lose the prop would move back and loosen on the shaft due to the taper. If it was parallel with a shoulder to resist the thrust in forward the nut in reverse and if the nut was loose the prop would bit loosen too mush on the parallel shaft unlike a taper shaft.

 

[rogerthebodger]

As the person suggesting lapping it was due to the coupling not fitting properly that I proposed it as an option

I agree the taper would need fitting. The way I do that is blueing the shaft and coupling/prop bore and the either scraping the bore using a very fine flap wheel in a die grinder. blueing again and again until you get at least a 60 % fit.

 

[jim.howes]

I agree the taper would need fitting. The way I do that is blueing the shaft and coupling/prop bore and the either scraping the bore using a very fine flap wheel in a die grinder. blueing again and again until you get at least a 60 % fit.

Brilliant we got there you have just stated THE TAPER WOULD NEED FITTING but i cannot agree with your method of achieving the end result. The whole question was how do i fit my coupling to the tapered shaft. If you had a tapered or a parallel shaft with a nut to retain the propeller and the nut loosened goodbye propeller and the lapping method i believe is still the best.

 

[rogerthebodger]

Brilliant we got there you have just stated THE TAPER WOULD NEED FITTING but i cannot agree with your method of achieving the end result. The whole question was how do i fit my coupling to the tapered shaft. If you had a tapered or a parallel shaft with a nut to retain the propeller and the nut loosened goodbye propeller and the lapping method i believe is still the best.

Each to his own.

 

[Beneteau381]

Its interesting that in all my design engineering career we very rarely used a shaft taper in any power transmission equipment we always had a parallel shaft with either a fitted taper key or a parallel (side fitted key). This needed a way to locate the pulley/gear laterally onto the shaft.

We some times use a fenner taper lock bush to locate the pulley/gear.

We used many hundreds of worm gear boxes on all the conveyor we designed for the motor manufacture, coal /rock/sand belt conveyors and in floor conveyors for car/truck assembly

Some of the gearboxes we used were higher than me so quite big.

The shaft coupling on my boat is a R & D with a fenner taper lock bush the coupling end of my propshaft is parallel, it's only the prop end that has a taper to match the taper in the propeller.

Maybe tapers are needed on big container ships where you have several 10 of thousands of horse power and immense torque to transmit.

These props are hydraulically fitted without any key as with this reversing torque you can get key fretting.

But what do I know only being in mechanical design engineering for most of my life.

All these electric motors have parallel shafts

elctric motors shaft - Google Search

Even the small petrol engines have parallel shafts

Then you have the power transmission couplings.

shaft couplings - Google Search

I used to work on Janus diesel electric locos. The electric motor drive pinion was held on by just a taper. Hundreds of horsepower transmitted through that. All British motorcycles from the 60s clutches were held on by tapers and a woodruff key. I was involved in a Triumph engine based project. 100 plus bhp transmitted through a taper, properly designed and fitted they are more than capable. The Radicon type gearboxes that you refer to, brute force and ignorance couplings with taper keys that were used to take up the slack in the inadequate machining capability of the times?
Ex maintenance engineer in Coal mines, Steel works, Oilfield in Africa and Middle East.

 

[rogerthebodger]

I used to work on Janus diesel electric locos. The electric motor drive pinion was held on by just a taper. Hundreds of horsepower transmitted through that. All British motorcycles from the 60s clutches were held on by tapers and a woodruff key. I was involved in a Triumph engine based project. 100 plus bhp transmitted through a taper, properly designed and fitted they are more than capable. The Radicon type gearboxes that you refer to, brute force and ignorance couplings with taper keys that were used to take up the slack in the inadequate machining capability of the times?
Ex maintenance engineer in Coal mines, Steel works, Oilfield in Africa and Middle East.

Just shows there are always several different ways to solve and design issue and different Engineers will do different things and different ways to solve any issue.

They are dust different and any one who proposes as design will always defend there design and consider its better and all the others.

The production engineers will always blame the design engineer and the maintenance engineer will also blame the design engineer who has screwed up the design in their view.

Been there done that and got the tee shirt.

 

[Silvercloud]

Looks like this debate is beginning to "taper off"

 

[rotrax]

I used to work on Janus diesel electric locos. The electric motor drive pinion was held on by just a taper. Hundreds of horsepower transmitted through that. All British motorcycles from the 60s clutches were held on by tapers and a woodruff key. I was involved in a Triumph engine based project. 100 plus bhp transmitted through a taper, properly designed and fitted they are more than capable. The Radicon type gearboxes that you refer to, brute force and ignorance couplings with taper keys that were used to take up the slack in the inadequate machining capability of the times?
Ex maintenance engineer in Coal mines, Steel works, Oilfield in Africa and Middle East.

Interested to know what Triumph motorcycle engine you were involved in.

Best I ever got on a H&F Dyno was 64 BHP from an iron head 650 on Methanol/10% Nitro Methane mix.

VMCC Sidecar championship winner x2.

Norton / AMC clutches were available with a splined centre.

Alf Hagon would twist them with hiss 200MPH JAP Special with the 1100cc vee twin!

 

[rotrax]

My two penny worth after a lifetime of fitting tapered shafts and their associated bits.

As most will know the key on a tapered shaft is merely a locating device. It is NOT required for security of fit.

In fact, fitting a driven part to a tapered shaft with a key often requires a degree of hand fitting.

If the key is too high above the slot it can stop the taper holding. I bought a boat, changed the prop and found the one removed was suffering from this. It was lucky to have stayed put.

Seen motorcycle ignition flywheels fly off hundreds of times through the same cause - a moment with a vice and a sharp file would always fix it if the shaft or bore were not damaged.

Reliant rear axle hubs were not keyed and were the very devil to pull off the long, slow taper. They NEVER shifted in use, even when we purposely drove one around for a week with the nut loose as we could not get it off. It was burned off with an oxy/propane torch in the end.

Triumph motorcycle clutches could be difficult too - pulled the threads out of the centre a few times with the little puller - they never engaged very far.

If a shaft or driven component would not grind in with paste, new bits was the way forward.

 

[Beneteau381]

Interested to know what Triumph motorcycle engine you were involved in.

Best I ever got on a H&F Dyno was 64 BHP from an iron head 650 on Methanol/10% Nitro Methane mix.

VMCC Sidecar championship winner x2.

Norton / AMC clutches were available with a splined centre.

Alf Hagon would twist them with hiss 200MPH JAP Special with the 1100cc vee twin!

RGB Weslake, he has reached the limit of the unit cases, about 110-120 bhp now 900cc. Still using E3134 cam profiles but 180 deg crank so having the cams made. We started off with pre unit cases but they used to crack horizontally where the barrel studs pulled on the top side of the main bearings. We went to helicoils as far as we could go which worked for a while. Then unit cases, they were a lot stronger. Meanwhile Norton cranks, then big Suzuki pistons and valves, inlet bored out from 1-1/16" to the biggest Spanish Amals you can get. Then the unit cases started cracking so weld on the inside of the cases so that we could get the barrel studs below the main bearings. Trick gearboxes next, made in NZ. But as I said, he has reached the end of what is possible with those Triumph based bits.

 

[Beneteau381]

Interested to know what Triumph motorcycle engine you were involved in.

Best I ever got on a H&F Dyno was 64 BHP from an iron head 650 on Methanol/10% Nitro Methane mix.

VMCC Sidecar championship winner x2.

Norton / AMC clutches were available with a splined centre.

Alf Hagon would twist them with hiss 200MPH JAP Special with the 1100cc vee twin!

The history of RGB Racing I was involved spannering up till that fatal day at Oulton. Horrible and I suspect that you have had similar experiences!