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Engine/gearbox/prop alignment.
jon200 - 14/1/13 at 08:59 PM

Is there a tolerance tht I should be working to? Obviously in an ideal works it should all be dead straight inline. I am struggling to have the engine back enough and get it all straight. I either need to chop the chassis on the vertical section on the driver side or notch the bell housing but that's a different story.
Is anyone running their engine slightly angled in the bay?

Jon

jps - 14/1/13 at 09:07 PM

Apparently in an ideal world it isn't all supposed to be perfectly aligned, having a slight angle allows the u/j's to move slightly with each rotation, making them last longer...

jon200 - 14/1/13 at 09:10 PM

Really, well if that's the case then I've learned something new today.

rusty nuts - 14/1/13 at 09:29 PM

You need a slight angle on the prop UJs otherwise they will fail .

unijacko67 - 14/1/13 at 09:39 PM

Look up phasing.

http://jniolon.clubfte.com/drivelinephasing/drivelinephasing.html

jon200 - 15/1/13 at 03:56 AM

That's an interesting read thanks, I was thinking that because or torque it all needed to be inline. Good job I asked. Because of the Darrow tunnel I can't offset the engine left to right though. I can angle it slightly or have it inline, which would be better?

Slimy38 - 15/1/13 at 08:19 AM

If I understand the concepts correctly, having it inline will mean that both UJ's aren't working, so they will both wear out. Having the engine angled will mean that the engine end UJ will work but the diff end won't, so that one will wear out.

Are you able to set the engine lower and get the parallel working that way? The article suggests between 1 and 3 degrees which isn't a great deal.

Interestingly, the Haynes roadster manual says 'In general, the plates should be fabricated to ensure that the gearbox is level and pointing directly at the rear mounted differential', and I think the Locost says something similar. So you're not along in your assumption that straight line is best!

jps - 15/1/13 at 08:50 AM

quote:
Originally posted by Slimy38
Interestingly, the Haynes roadster manual says 'In general, the plates should be fabricated to ensure that the gearbox is level and pointing directly at the rear mounted differential', and I think the Locost says something similar. So you're not along in your assumption that straight line is best!


When I first started building my car I, perhaps naievely, assumed that having everything aligned to the n'th degree and measured in thousands of an inch was going to be the case for every component. The more I read and actually do stuff the more I realise that 'it looks straight to the eye' is often about as precise as it gets!!!

johnemms - 15/1/13 at 09:05 AM

The diff flange & gearbox flanges should stay theoreticaly
flush and square on with each other during - driving - up & down movement..
The prop angle varies & keeps the bearings moving..

If the flanges are not square on - one end of the UJ prop will have a shallower
turn point & rotate slightly faster than the other and give vibration and shake..

ie:
fixed diff no movement - angle gearbox down = bad
fixed diff no movement - square gearbox on to flange = good

somthing like that ... :p

Slimy38 - 15/1/13 at 10:18 AM

quote:
Originally posted by johnemms
The diff flange & gearbox flanges should stay theoreticaly
flush and square on with each other during - driving - up & down movement..
The prop angle varies & keeps the bearings moving..


That would work with a live axle, but as an example I'm looking at an MX5 donor with a fixed diff. The only up and down movement will be the engine on it's mounts, and that won't be enough to keep a UJ running. I think I'll have to 'artificially' deflect the engine in order to get the movement. But I will check the diff and engine as it sits in the donor, I wonder whether Mazda work on everything being in line.

But yes, the parallel aspect also implies that the flanges are square related to each other.

unijacko67 - 15/1/13 at 09:24 PM

Has anyone used constant velocity at gearbox and UJ at diff, live axle? That’s what I will be using on the kitten.

I have offset diff which has no more negative effect than the axle going up and down, for example if the output shaft flange and diff flange are parallel to each other it makes no more difference being to one side 1” as axle travel up and down, so keep the engine to the side if thats where it fits, dont point the engine/gearbox at the diff (plan veiw).