Jump to content

Propshaft vibration ... ?


BogMonster

Recommended Posts

Turbocharger - it's hard to say if 'your maths is carp' when you didn't write any of it down!?!? :blink:

It's the sort of post that we need more of around here! But equally, it's hard to assimilate it while doing other stuff at work... My initial thoughts are as follows, but I may not have fully absorbed what you've done...

1. Any chance of actualy stating your calcs? That's the only way to know if it's right.

2. If I got it right, the first plot is the rotational velocity (how do you write an 'omega' in a forum? - I'll use a 'w') for each end of a single-UJ ended shaft. You state that the diff end is a straight line, then you have some variation in w over a revolution? These two points don't seem to tally - maybe you used a small angle?

3. What is the Y-scale on both plots?

4. Did you use an input w of, say, 100 - is it rpm?

5. What are the axes of the second plot?

6. In the first plot, the diff w seems to have twice the frequency of the propshaft w. Is this the central body of the propshaft? Any thoughts on this relationship?

More questions than answers really... Al. :)

Link to comment
Share on other sites

it is all true!

but:

on the picture from white 90, you can see the castor corrected radius arms, and these are the cause of the smaller angle at the diff end and bigger angle on the gearbox end.

If you want to achieve the bigger castor, the corrected swivels from tomcat are a much better solution, but I believe these are discontinued.

you can improve things with the double cardan joint, but I believe that it is better to use standard ujs, especially if you go to remote places.

in my case, I have lifted the car by about 1.5 inch and no problems at the front. At the back, I run radius arms, and the diff nose points up like it does at the front. No problems with uj s binding or vibrations. And, more important: Simple, cheap and reliable.

Link to comment
Share on other sites

Disclaimer - 4 pints later

Axes - 1st plot is output velocity as % of input velocity, for the shaft (blue) and the output flange (purple). The purists will ask why the average output is 134% of input speed. I don't know. I could explain it for the blue plot: integrated speed wrt angle will be greater, integ wrt time ought to be equal.

2nd plot is standard deviation of output velocity results for different alpha/beta angle combinations. Unsurprisingly, phase makes no difference where one angle is 0° but I was surprised to find 90° phase is always best (but it kinda makes sense).

If the forum allows hotlinking, my equation is:

1b9d6a3968961e42a6dc496473fd3bf4.png

where w2 = output speed

w1 = input speed

beta = UJ angle (ie less at axle end than gearbox end)

phi = shaft rotation (ie effected by the engine, demonstrated over 360° in examples)

Jim - hell, even I'm scared now.

JB

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy