Winter Development

[Nick Jones]

On 13/10/2024 at 16:35, 65redspit said:

That's very interesting Nick, where do you go to get this done please?

On axle stands with wheels and brake drums off. Just make sure the drive shafts aren’t in contact with the chassis. Then it’s two suitably sized jubilee clips on the propshaft and run it up in 4th gear.  Then it’s lots of experimentation with the absolute and relative positioning of the jubilee clips.

Vitesse is good to 112mph. Actually it’s difficult to tell over 100 as everything else is shaking and flapping so much 🙃

Can also be worth running it SLOWLY with the wheels on. This gives an idea of whether the wheels/hubs/drive shafts are straight and true. Though experience has shown that wheels can be really bent without actually causing vibration!

[Nick Jones]

3 minutes ago, 65redspit said:

so I'm fairly certain it's not the prop but the idea of balancing it all on the vehicle with the wheels does make sense ...

The thing about the prop is that as well as the actual balance, the stiffness of each UJ axis matters. They need to be free moving but without play. The shaft angle and operating range of each joint also plays a part.  If you look at the ideal or acceptable parameters against what actually exists on these cars, there’s not much overlap.  The gearbox mount height and where it puts the front UJ can be a problem (some of my gearbox conversions have certainly not helped!). 
 

The big problem though is the relatively lightweight and flexibly mounted diff which doesn’t damp and vibration as a live axle does.

[65redspit]

23 minutes ago, Nick Jones said:

The thing about the prop is that as well as the actual balance, the stiffness of each UJ axis matters. They need to be free moving but without play. The shaft angle and operating range of each joint also plays a part.  If you look at the ideal or acceptable parameters against what actually exists on these cars, there’s not much overlap.  The gearbox mount height and where it puts the front UJ can be a problem (some of my gearbox conversions have certainly not helped!). 
 

The big problem though is the relatively lightweight and flexibly mounted diff which doesn’t damp and vibration as a live axle does.

Hmmm very good info ... brand new driveshafts high quality race UJs all round - like the idea of the jubilee clips and having a go at home 👍🏻💪

[JohnD]

I've understood that there are four ways to mount a prop shaft, thanks to the way that the flange plates at each end are drilled. Two pairs, so two ways at each end.

Of these, one will offer dreadful balance, two so-so and one perfect!   That's why the flanges should be marked before dismantling.  If not, more opportunity for try 'n' test!

John

[65redspit]

11 minutes ago, JohnD said:

I've understood that there are four ways to mount a prop shaft, thanks to the way that the flange plates at each end are drilled. Two pairs, so two ways at each end.

Of these, one will offer dreadful balance, two so-so and one perfect!   That's why the flanges should be marked before dismantling.  If not, more opportunity for try 'n' test!

John

That they were drilled one way I knew, that they could be 180 out I didn't .... the ujs were on when it was balanced but I can switch 180 and see what happens, only take 10 mins...

[65redspit]

Just now, 65redspit said:

That they were drilled one way I knew, that they could be 180 out I didn't .... the ujs were on when it was balanced but I can switch 180 and see what happens, only take 10 mins...

 

14 minutes ago, JohnD said:

I've understood that there are four ways to mount a prop shaft, thanks to the way that the flange plates at each end are drilled. Two pairs, so two ways at each end.

Of these, one will offer dreadful balance, two so-so and one perfect!   That's why the flanges should be marked before dismantling.  If not, more opportunity for try 'n' test!

John

Thank you !!

[JohnD]

58 minutes ago, 65redspit said:

 

Thank you !!

You mean .. it worked?   Not that I'm surprised, but grateful for the feedback!