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Old 04-15-2017, 10:01 PM   #1
Port&PolishMan
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Checking Driveling Vibration & Calculating It.

First Off
RPM and Drive-line Vibrations - Looking at the Gearing and Engine RPM's

Seeking to Figure - Drive Line - RPM to see If the Drive Shaft may be
an Issue as it is Past it's Design .. Limit ..

I see where a few stated 45 - 48 Mph & 1 or 2 say Run up to 55 Mph
Pumpkin Gear 5:14

1954 4 Speed - with PTO - Type of Transmission .

V8 Spinning 4000 RPM with 5:14's in Third Gear or 4th Gear
Approx what RPM is Drive-Shaft Spinning ?
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Old 04-16-2017, 12:10 PM   #2
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Re: Checking Driveling Vibration & Calculating It.

top gear is 1:1, so the driveshaft speed will be the engine rpm.

if you need a gearing calculator to figure out what the effect the rear axle ratio and tire size will have on engine rpm, I like to use the unix nerd one I found years ago for BMW, easy to change, you might have to do an inch to mm conversion on your tire size if its different than the width in mm/aspect ratio/rim diameter standard though.

enter your tire diameter, enter rear gear ratio, enter rpm and use 4th gear, its 1:1, then select calculate speed. or, if you know speed, enter speed and calculate rpm.

http://www.unixnerd.demon.co.uk/revs.html

working backwards (entering speed and calculating rpm), you can see what the effect of a lower gear ratio will be.
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Old 04-16-2017, 02:25 PM   #3
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Re: Checking Driveling Vibration & Calculating It.

Thank You
Yes those Calu. are Handy :

2.5 Inch Drive Shaft - 54 inches long - Has a Max Safe Limit of 3148 RPM
with 1/2 Critical Vibration Drive-Line being - 2802 Rpm - They are Referring to Harmonic's @ 2802 RPM . .

It Calu. to Potential Speed of 52.0 - 55.0 Mph - depending on Tires Size .
Cruising Speed : 40 Mph - 46.4 Mph - all these being in Safe RPM Ranges .

Now the Other Vibration Drive-Line - Item .. ( It Seems everyone Here on this Site has talked about these Angles )
But No Where did I find anything about the Designed Offset - built into the Rear Gear and Or the Transmission .

Many 4 Speeds with PTO or With Out - look to be - Off Center approx 2 " Out Put Shaft ; and the Rear Gear just looking approx 4 " at Pinion . .
with a Carrier in between . . ( Will Measure Soon ) - these Offsets have a Direct Impact on Drive Line Angles . .

[IMG][/IMG]

Last edited by Port&PolishMan; 04-16-2017 at 02:32 PM.
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Old 04-16-2017, 06:45 PM   #4
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Re: Checking Driveling Vibration & Calculating It.

The offset in the plan view can be disregarded because they are equal and opposite; they cancel each other out .
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Old 04-16-2017, 09:54 PM   #5
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Smile Re: Checking Driveling Vibration & Calculating It.

Quote:
Originally Posted by Keith Seymore View Post
The offset in the plan view can be disregarded because they are equal and opposite; they cancel each other out .
OK - Keith I think I understand the Canceling out Point - in 1 Plane
as We look at it ( Side View ) - how about ( Top View ) or as I always say
The Other Plane `\ : - )

That's the Trans Offset & Pinion Off Set - I'm concerned with ?

So Both the Out Put Shaft on Trans Tail and Input on Pinion - would
need to be Same Dim. Off - ( Center Line of Chassis )
Hence - Top View ..

Also - May I add seeing many Trucks have Center Shaft Bearing - Total Length of Drive Shaft would be ( Considered )
Both Half's and ADD .500 to the Dia. - due to extra Support OR
Just Consider the Longest Drive - Shaft - Minus .500 Dia. Due to the Presence of a Bearing Support ?


Above ? is for everyone having Any Experience with these Considerations - as many have Changed Rear Axles & Center sections ..
Chasing Down - Eliminating Bad Vibrations !

Last edited by Port&PolishMan; 04-16-2017 at 10:05 PM.
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Old 04-17-2017, 05:42 AM   #6
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Re: Checking Driveling Vibration & Calculating It.

Looking down at frame rails, center line of trans and center line of pinion should be in line with truck frame rails. Angles auto-magically cancel. More offset of one to the other doesn't matter. If axle is set back to make big thrust angle, or trans and engine are not parallel to rails, then you might see a problem.

WRT to vertical plane, pinion angle is not parallel to ground, trans angle not parallel to ground, shaft must be installed so angles cancel.
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Old 04-18-2017, 07:44 AM   #7
Keith Seymore
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Re: Checking Driveling Vibration & Calculating It.

Quote:
Originally Posted by 1project2many View Post
Looking down at frame rails, center line of trans and center line of pinion should be in line with truck frame rails. Angles auto-magically cancel. More offset of one to the other doesn't matter. If axle is set back to make big thrust angle, or trans and engine are not parallel to rails, then you might see a problem.

WRT to vertical plane, pinion angle is not parallel to ground, trans angle not parallel to ground, shaft must be installed so angles cancel.
This is correct on all counts (except for the "magic" part ).

Quote:
Originally Posted by Port&PolishMan View Post
OK - Keith I think I understand the Canceling out Point - in 1 Plane
as We look at it ( Side View ) - how about ( Top View ) or as I always say
The Other Plane `\ : - )

That's the Trans Offset & Pinion Off Set - I'm concerned with ?

So Both the Out Put Shaft on Trans Tail and Input on Pinion - would
need to be Same Dim. Off - ( Center Line of Chassis )
Hence - Top View ..
When I referred to the "plan view" that is the "top" view (plan view = view from the top).

So we've answered your question twice now, in a couple different ways.

It is a geometric principle that if a line bisects two parallel lines then the opposing angles will be equal. In the diagram below angles "A" are equal and opposite, as are angles "B". So the offset doesn't need to be the same; only that all of the components need to be square to the vehicle centerline.

Also - the u joints can easily tolerate a difference of +/- 3 degrees; considering the amount of offset compared to the length of the shaft(s) the resulting angle is usually much smaller than this and does not result in a disturbance.

That's why the angles in the top view are generally discounted and all of the focus /discussion is on the view from the side.

Quote:
Originally Posted by Port&PolishMan View Post
Also - May I add seeing many Trucks have Center Shaft Bearing - Total Length of Drive Shaft would be ( Considered )
Both Half's and ADD .500 to the Dia. - due to extra Support OR
Just Consider the Longest Drive - Shaft - Minus .500 Dia. Due to the Presence of a Bearing Support ?
Variations of shaft length (in fractions of an inch) are not significant in terms of effects on U joint working angle. Increasing the length of the rear shaft in the basic design can affect launch shudder (a u joint disturbance that manifests itself upon initial acceleration from a stop).

The working length of the shaft is from the center of the u joint cup (front) to the center of the u joint cup (rear).

K
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Last edited by Keith Seymore; 04-18-2017 at 02:02 PM.
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Old 04-18-2017, 08:03 AM   #8
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Re: Checking Driveling Vibration & Calculating It.

Take a look at this and see if it helps.

There is a section on two piece drivelines but I did not include it here; I try to avoid two piece applications (both at work and at home) and order my trucks such that they get a one piece shaft.

http://67-72chevytrucks.com/vboard/s...d.php?t=522180

If you can follow the logic shown in the flow chart you can fix any driveline problem.

Quote:
Originally Posted by Port&PolishMan View Post
Above ? is for everyone having Any Experience with these Considerations - as many have Changed Rear Axles & Center sections ..
Chasing Down - Eliminating Bad Vibrations !
I have a little bit of experience with these considerations.

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Last edited by Keith Seymore; 04-18-2017 at 08:10 AM.
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Old 04-18-2017, 05:01 PM   #9
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Re: Checking Driveling Vibration & Calculating It.

You'd the Man
I understand all Your Input . - I'm stuck with a Two Pc. Drive Shaft - Unfortunately .

Also the Tail Stock on Truck Drive-Line is Not Centered - Neither is Pinion on Rear Gear.

But , from what I'm seeing so Far on this Truck - I can only Hope !
Hence the ?'s - Before I Go and Investigate Deeper .

Thank You - I have just started to set up , some Measuring Equipment .
Currently the Rear Bolt Mounts to the Trans - Are Not Even Bolted Down
NOT SURE - what those Intentions Could Be , so Digging In !

Last edited by Port&PolishMan; 04-18-2017 at 07:17 PM.
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Old 04-19-2017, 08:26 PM   #10
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Re: Checking Driveling Vibration & Calculating It.

Still Checking Vibration - may have found some Good Vibrations :
[IMG][/IMG]
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Old 04-19-2017, 08:30 PM   #11
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Re: Checking Driveling Vibration & Calculating It.

Looking at all the Angles : Pumpkin Offset 5 inch approx - Pinion comes Back
2.25 Approx . - Picking up that Center Line - to Check - All the Way
Tail Trans Area :
[IMG][/IMG]
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Old 04-19-2017, 08:31 PM   #12
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Re: Checking Driveling Vibration & Calculating It.

Trans _ C/L _ Mission : Nailed It !

[IMG][/IMG]
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Old 04-19-2017, 08:34 PM   #13
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Re: Checking Driveling Vibration & Calculating It.

Same: Center / Line = C/L

Viewed Now on the Carrier or Mid Bearing :

[IMG][/IMG]

Then it's just Steel Rule to Frame and Math , all done . For that Plane !
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Old 04-19-2017, 08:38 PM   #14
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Re: Checking Driveling Vibration & Calculating It.

More Disturbing was the Carrier Bearing Mount with Bearing is Bolted
Square to the Frame - when Nothing Else is ? Seems a Bit Odd ..

Possibly You'll see it these Photo's :
[IMG][/IMG]

This one for Sure - Easily Pass Finger on 1 side - No Way on Other ..

[IMG][/IMG]

What the Hell ?
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Old 04-19-2017, 09:18 PM   #15
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Re: Checking Driveling Vibration & Calculating It.

In the Area - so - Why Not ! "INSPECT" other Items .

https://youtu.be/fuTFBxxk9Fk

Had .018 T.I.R Before - Adjustment .

https://youtu.be/fuTFBxxk9Fk
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