Propshaft angles

[cliftyhanger]

Having had a disaster almost a year ago in my Spitfire because of excessive prop angles, I am now approaching the refit of my engine/box and prop in a few days.
I have ordered one of the volvo gearbox mounts as the current one is very wobbly. I read how Galileo did his (good article) but I am unsure if my engine is at the normal height.
So how much of an angle should the front section of the prop be at? (ideally compared the gearbox centreline)
Guidance very welcome!

[Carledo]

Having had a disaster almost a year ago in my Spitfire because of excessive prop angles, I am now approaching the refit of my engine/box and prop in a few days.
I have ordered one of the volvo gearbox mounts as the current one is very wobbly. I read how Galileo did his (good article) but I am unsure if my engine is at the normal height.
So how much of an angle should the front section of the prop be at? (ideally compared the gearbox centreline)
Guidance very welcome!

There doesn't seem to be a maximum prop angle, nor can you actually ACHIEVE much of an angle without the engine sticking up through the bonnet! I don't know how far out your Spit angle was, but i'd have thought you'd need at least 15 degrees to do it harm. With the confines of the engine bay, I imagine you'd struggle to get as much as 5 degrees. So IMO, it's a non issue!

From what i've learned, the thing to avoid at all costs, is a ZERO angle between the the prop and 3rd motion shaft/O/D output shaft. This has been known to introduce vibration and unwanted sympathetic resonances in the driveline as well as shortening UJ life because it's always running in exactly the same line.

I'm not knocking Galileo, far from it, but I have fitted a good half dozen Volvo mounts now and have not bothered with a 6mm spacer nor have I had any problems! If it looks like you are close to the dreaded zero angle, use the Sprint method of mounting the centre bearing with one lug of the bearing housing BELOW the body mounted support bracket.

When I built the Carledo, I used the Vauxhall sourced front coupling, which resembles a small Rotoflex unit. After i'd done all the work fitting the engine and gearbox and supplied the prop and front section of the Carlton prop for my man at Proptech to assemble and balance, when he handed it back to me, he commented that THIS sort of coupling should run the shaft at no MORE than 1 degree out from the gearbox/crank line. NOW HE TELLS ME! So I took it home and fitted it with some trepidation, but it LOOKED pretty close so I went with it! Either i'm very lucky or VERY VERY good, cos it's still there 8 years and countless storming starts later! And though I have 2 spare couplings, so far i've not needed one!

Steve

[cliftyhanger]

Having had a disaster almost a year ago in my Spitfire because of excessive prop angles, I am now approaching the refit of my engine/box and prop in a few days.
I have ordered one of the volvo gearbox mounts as the current one is very wobbly. I read how Galileo did his (good article) but I am unsure if my engine is at the normal height.
So how much of an angle should the front section of the prop be at? (ideally compared the gearbox centreline)
Guidance very welcome!

There doesn't seem to be a maximum prop angle, nor can you actually ACHIEVE much of an angle without the engine sticking up through the bonnet! I don't know how far out your Spit angle was, but i'd have thought you'd need at least 15 degrees to do it harm. With the confines of the engine bay, I imagine you'd struggle to get as much as 5 degrees. So IMO, it's a non issue!

From what i've learned, the thing to avoid at all costs, is a ZERO angle between the the prop and 3rd motion shaft/O/D output shaft. This has been known to introduce vibration and unwanted sympathetic resonances in the driveline as well as shortening UJ life because it's always running in exactly the same line.

I'm not knocking Galileo, far from it, but I have fitted a good half dozen Volvo mounts now and have not bothered with a 6mm spacer nor have I had any problems! If it looks like you are close to the dreaded zero angle, use the Sprint method of mounting the centre bearing with one lug of the bearing housing BELOW the body mounted support bracket.

When I built the Carledo, I used the Vauxhall sourced front coupling, which resembles a small Rotoflex unit. After i'd done all the work fitting the engine and gearbox and supplied the prop and front section of the Carlton prop for my man at Proptech to assemble and balance, when he handed it back to me, he commented that THIS sort of coupling should run the shaft at no MORE than 1 degree out from the gearbox/crank line. NOW HE TELLS ME! So I took it home and fitted it with some trepidation, but it LOOKED pretty close so I went with it! Either i'm very lucky or VERY VERY good, cos it's still there 8 years and countless storming starts later! And though I have 2 spare couplings, so far i've not needed one!

Steve

Spit had the grarbox and diff parallel (OK within 0.2degrees) but the uj angle was about 7 degrees.
Anything over 3 degrees is unacceptable accoprding to all the UJ manufactureres, if you intend to use anything more than low revs.

took 2 days effort to lower the gearbox, alter the exhaust and adjust the diff/reset suspension. Diff/box angle slightly worse but UJ angle down to 3.2 degrees. So needs to be revisited.

Will avoid zero angle like the plague!

[Carledo]

Because the Toledo has a 2 piece prop, the angles are not so critical, or so big as they can be split between the 2 sections.

Considering i've seen many Sprints running quite happily with collapsed engine mounts (oil pump nearly on rack) soggy gearbox mounts and ripped and half destroyed centre bearing rubbers, all of which will have an effect on the gearbox/crank/prop alignment, I would say there is a fair chance of SOME latitude being acceptable, it's not as simple as right or wrong. Lowering the rear suspension will also alter the angles. (and the mean prop length)

Steve

[jikovron]

There is a good 25mm of vertical movement either way of ideal tail housing height before it starts to thrum resonantly under light load and if the engine has enough torque wobble the gear lever under load like I experienced with my v8 before i raised the centerbearing to equalize the angles.
As long as the middle and diff UJ measure the same angle and the box uj has a tiny amount it's all good.
Also some tube in tube rubber damped props will naturally thrum at high speed although I dont think any dolomites had those sort.