I have just noticed that the splined part of the prop shaft that goes into the gear box is keyed, ie it will go in one of two ways. I rememeber mickyb saying that there is a right way and a wrong way to mount the prop shaft but does this just apply to the stock shaft as its balenced to be mounted one way?

 

When i fit my new single piece shaft can i just mount it either way?

The propshaft joint angle changes due to engine and diff movement will be roughly the same with a one piece prop as it is with a 2 piece prop. The one piece prop still has a joint at both ends, and will accommodate the movement as well as a 2 piece prop.

 

A one piece prop on a fairly short span such as the zed will work fine, as long as it is dynamically balanced, and the input and output angles are within 1/2 degree of each other, and less than 3 degrees each.

I have to say that this is one of the most enlightening threads I have read for some time. It may also explain the fact that although I have a feather weight carbon prop with light ally ends which Is well balanced I still get a micro vibration at some speeds.

is somewhat similar to second degree harmonics in cranks???

Oh yeh!! One other thing ... I wanna look at da V8! Me n Ed are only up the road??

Group V8 viewing anyone?? :D :D :D

Hi, Pete

No, second degree crank forces are a completely different thing.

 

When a steady rotating speed is fed into a u/j, going thro an angle, the speed coming out of the u/j is not constant. It speeds up and slows down slightly thro the revolution.

Ie, 3000rpm going in, 3001/2999rpm coming out.

 

this is what causes the apparent vibration. The bigger the angle, the more the variation. However, these variations can be cancelled out by having another joint at the other end of the shaft. The only catch is that this joint must be the same angle as the first, and bend the opposite way.

 

So if the input joint bends thro 3 degrees and the output bends the opposite way, but only thro 2 degrees, then you end up with 1 degrees worth of speed variation, and hence the apparent vibration.

 

The cure is to either alter one or both angles to make them the same, or scrap the uj's and use cv joints at either end.

 

Hence the name, constant velocity joint. U/j's are not constant velocity.

 

The prop bends also have to be equal side to side as well as up and down.

 

Ps, call in any time, but bear in mind it's just a garage full of bits at the mo.

01332 556237. You can buy my n/a engine while you're here......

ahh i never knew what cv joint stood for! It seems your the daddy when it comes to the thoery of drive shafts! Are you coming to our meet in uttoxeter tomorrow keith?

Yeah thats what i meant, had to push it right in the gearbox then pull it out a bit to get it over the, er Flange and bolt it on!

 

Is the rear gearbox seal i can see just a dust cover or something then? mmm Fingers crossed

thats perfectly normal, as said it needs some movement

Hi, Pete

No, second degree crank forces are a completely different thing.

 

When a steady rotating speed is fed into a u/j, going thro an angle, the speed coming out of the u/j is not constant. It speeds up and slows down slightly thro the revolution.

Ie, 3000rpm going in, 3001/2999rpm coming out.

 

this is what causes the apparent vibration. The bigger the angle, the more the variation. However, these variations can be cancelled out by having another joint at the other end of the shaft. The only catch is that this joint must be the same angle as the first, and bend the opposite way.

 

So if the input joint bends thro 3 degrees and the output bends the opposite way, but only thro 2 degrees, then you end up with 1 degrees worth of speed variation, and hence the apparent vibration.

 

The cure is to either alter one or both angles to make them the same, or scrap the uj's and use cv joints at either end.

 

Hence the name, constant velocity joint. U/j's are not constant velocity.

 

The prop bends also have to be equal side to side as well as up and down.

 

Ps, call in any time, but bear in mind it's just a garage full of bits at the mo.

01332 556237. You can buy my n/a engine while you're here......

so in reality iff theres a diffrence in angles from front and back and theres a joint in the middle its going to be constantly correcting the variation on the move,remove this joint and the "angle medic" cant do its job :confused: i mean how is the front and rear going to change angles in a equal form (3mm up at the front and 3 mm down at the back) ide say its impossible when you consider torque,speed,worn engine mounts and subframe mounts plus the natural twist of the drive line under hard power

...............err

I think you have completely misunderstood everything I was trying to say.

I'm not sure how else to explain it other than how I did originally.

 

Oh, there's no centre bearing in the above example, it's just a plain one piece shaft with a u/j at each end.

...............err

I think you have completely misunderstood everything I was trying to say.

I'm not sure how else to explain it other than how I did originally.

 

Oh, there's no centre bearing in the above example, it's just a plain one piece shaft with a u/j at each end.

lol i know ime trying to explain the pro,s of having a 2 piece prop ;)

i was,nt being funny as i know what your saying totally,i use to be into 4x4 with 6 inch lifts so i know its a pain in the ass getting props setup right :D

just put a jub clip on it

 

vibrations reduced by about 50%!!!

 

im just gonna put other one on in the same position

Right, putting a second jubilee clip on didnt help much.

 

I have took the shaft off now and its back with the drive shaft company

 

They say that it wont be the shaft causing the vibration as it would do it at 28mph and again at 48 not 70 and 100

 

They are checking it for me again on thier balencing machine anyway.

 

They said that the single peice shaft should be better than the stock one as far as vibrations go, the difference in the angle of the uj's wouldn't do much on this shaft

 

They said thet the old one had a knackered uj and centre bearing, the play in these was probably taking up the vibration that would have been there already making it not noticable.

 

The diff and gearbox mounts are original on the car so it looks like i am changing them.

 

Hopefully they will come back to me and say it was slightly out of balence but i cant see this happening tbh

ed, your propshaft company are talking bolox.

If you pop over sometime I'll lend you the tool for checking the box and diff angles. It's a piece of pi88 to do. At least you'd know then if it was an angle prob or an out of balance prob.

OK mate, thanks

 

The prop is off now and I dont really enjoy taking it off and putting it on all the time!

 

I may well take you up on that offer, as i want to get it right before putting it back on again.

 

I am going to ring them in a mo to find out if the prop was out at all.

 

I found this thead, talks about some sort of indicator that can be used, have a look and see if you know what they are on about?

 

http://www.300zx.co.uk/forums/showthread.php?t=55178&highlight=0.001

Ed - keep us informed, like you I'm chasing the elusive vibration. The threads very informative - thanks.

 

Jack

Just phoned them and they said it was slightly bent, they are not sure how!

 

Has now been adjusted and is straight.

 

sounds hopefull me to, i will have a proper chat with them tomorrow when i pick it up

 

I got it from mjp but it was sold as faulty, made too long by the factory in mexico, i bet they made it bent as well! The place in notts only shortened it for me, i bet it was always bent.

 

Sounds like too much power to me lol

 

I think i will come and see you keith, no harm in checking the angles as well. I also want to have a perv at your v8 as well!

 

can you have a look at this thread as well for me keith

http://www.300zx.co.uk/forums/showthread.php?t=55178&highlight=0.001

The problem with checking the runout is that, say the uj is a couple of thou' out and the prop flange, and the prop end yoke, then if all these out of tolerances stack up in the same direction you could get, say 5 thou runout on the propshaft tube.

But when it is balanced then this runout will be taken into account and cancelled out with the balancing weights.

If you go bashing it to run true then it will obviously go out of balance again.

 

It is a good way of checking for a bent tube tho.

 

Is it Wilson Driveshafts you went to. I went there once and they completely wrecked my prop. After speaking to them about propshaft theory I realised I may as well be talking to my rabbit.

 

At the end of the day there are only a couple of things which need to be spot on.

Assuming nothing is worn of course,

 

Firstly the angle of the gear box and the diff needs to be the same, and preferably less than 4 degrees. And the centrelines of the gearbox and the diff need to be parallel when viewed from above. They do not have to be in line, only parallel. This is a bit more tricky to measure than the up and down angle. I used a couple of lasers.

 

2ndly the prop has to be in balance. Unfortunately we are in the hands of the balancer here.

 

Oh, one more thing, the yokes on the shaft have to be perfectly in line too.

 

Ed, bear in mind if you want to measure your angles then it's loads easier to do with the prop off.

Yes, it is Wilson Driveshafts! - oops!

 

I hope thay dont wreck it, what did they do to yours?

 

They said that it was bent but it had now been fixed and its ready for collection.

From how it felt on the car I can belive that is was bent as thats exaclty how it felt.

 

I will leave it off and come and see you this weekend, maybe bring it with me?

Ed, PM sent

Strange, Wilsons did my custom jobby no problem!-no vibration and fit spot on! :smash:

oh yeah now i remember, i went there on your recommendation!

I picked it up this morning.

 

They said the tube was bent and out by about 3mm. I asked about power etc but they said it would be twisted not bent and showed me one that had been twisted by too much power. They said its like it had been dropped but it wouldn't of left them like that.

 

mmm ok well i have not dropped it, and the vibrations started as soon as i put it on the car. I asked about the quality of the tube, could it be poor quality, they said no its fine.

 

They said that even though it was bent they didnt think the prop was the cause of the vibration. I think it was however as the prop being bent would exactly describe the vibration speed and amount. Also the vibration i had started when i fitted the prop and the symtoms were not like anyone elses that were fixed with new mounts etc.

Hi Keith, thanks for the plumb bob tool, sorry about your back door step!

 

I checked the car and the machined face on the diff is at -3 degrees exactly. There is no machined face on the gearbox that I can get to easily so i took a reading from the edge of the dust sheild on the prop end of the gear box. The dust cover projects out from the machined face on the gearbox so should be at exactly the same angle. On this i get a reading of between -2.8 and -3 degrees depending on where i put the steel rule.

 

So at the most the diff and box are 0.2 degrees out, would that be within torrence? To make the gearbox -3 degrees it would need to be raised at the rear by a tiny amount, a new rear mount might be the key.

 

My car is not on level ground, if it was the angles would be about 0 but obviously there would still be about 0.2 degrees between the diff and box.

 

I also weighed the allen bolts that hold the prop to the machined face of the diff. The odd one I got from the motorbike breaker is only 0.3g heavier than the others so I dont think I need to worry about these!

 

Let me know what you think. Lovely looking z you have by the way, cant wait to hear the noise it will make!

 

Ed

Right ok well if 0.2 degress isnt worth worrying about i will start putting it back together on tuesday morning.

 

Will post up the results

Car back on the road today, will find out about the prop shaft later!

Just been to get some fuel, then used it all! Its Smooth as fook!!!!!

 

First time i have felt a sense of satisfaction with this car in a long time yey