Driveshaft Critical Speed - A Calculator

Piratetip

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This thread is intended to provide accurate factual information about 1 piece driveshafts regarding critical speed.
All subjectivity and opinions are not intended to be expressed here.

After reading all the discussion about critical speed and 1 piece drive shafts I have decided to research this topic further.

Critical Speed: The critical speed of a spinning shaft is described as the lowest speed which excites the shaft at it's natural frequency of vibration. This will cause the shaft to bend under the stress of vibration coupled with the centrifugal forces due to the rotation. In English, this means the shaft will vibrate very badly and possibly take a permanent bend (if not destroy the car in the process) as the critical speed is exceeded. If you use the calculator to predict the critical speed of a shaft, you can clearly
see that lighter materials with higher modulus of elasticity give higher critical speeds. So do larger diameter shafts with thinner material thicknesses. Unfortunately, there is a limit to the diameter of shaft you can put in the car, so stronger lighter materials were developed to make stronger and faster spinning shafts.

I have modified a multi-purpose calculator in Excel.
It calculates:
Tire Diameter
Tire Width
RPM at MPH per gear
MPH at RPM per gear
Driveshaft Tube Weight
Critical Speed
1/2 Critical Speed
Torsional Yeild
Max Drivshaft Speed
Added -> Driveshaft RPM at MPH
Graphs

Download Here
Host 1
****Updated host 1 link as of 11/29/2020


I hope this thread brings together useful information from the multiple threads on this subject.

Most people are aware of this calculator already.
http://www.wallaceracing.com/driveshaftspeed.htm#modulus
I have recreated all of these calculations and fixed some errors they had.
I also added many more calculations that you may find useful.

Mods: Could you fix this for .xls files?
Your file of 47.5 KB bytes exceeds the forum's limit of 1.0 KB for this filetype.
I would like to upload it directly to the site.
Maybe make this a sticky?
 
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Doward

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Also, thought I'd point out that engine rpm isn't nearly as useful as d/s rpm, in relation to speed (which will be directly dependent on rear end ratio + tire height)

;) Just ideas, that's all.
 

Piratetip

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Dow: Not sure why you can't change the diameter, works on my end. You can unlock the sheet if it still does not work. Tools -> Protection -> Unprotect

Yeah I know engine rpm isn't what we are looking for.
Although when in the direct drive gear 3rd or 4th depending on the tranny these #'s give actual driveshaft speed. If you were to extended the RPM chart beyond 7500rpm you can match them over to the next overdrive gear.

This program will easily let you do this. GearCalc
 

Piratetip

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Dow: I have added a new table you requested to the excel file.
The sheet now includes Driveshaft RPM at MPH table.
Could you change your link to the new Excel sheet.
Thx.
 
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Doward

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Updated. Link will provide the new version.

Piratetip, I'm using OpenOffice here, and the cells for DS RPM were showing up as #### - they were formatted to have a leading zero, so I took those off, and everything shows up fine for me now. I saved that, and uploaded that version.

If anyone here has MS Office, could they quickly check everything out, let me know if any of the formatting is off now?

Thanks
 

Piratetip

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Hmm...not sure why it was doing that.

OpenOffice might have some compatibility issues with it.
But thanks for cleaning it up.
Hopefully everything works now.

:)
 

Piratetip

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Yeah I have office 2003 so it will be compatible with all newer versions as well.
I downloaded your version, everything seems to be working well.
:)
 

Sawbladz

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So what quality aluminum/steel is available in the aftermarket? What does 1053 refer to and what does MMC mean?
 

Piratetip

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Material Properties listed in the chart are the most common materials used to make driveshafts.
MMC is a grade of Aluminum and 1053 is a grade of Steel.
The 3 listed are what most aftermarket shafts are made of.
 

cuel

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Where it says "R154 N/A," in the trans. list, is that supposed to be the w58 that comes stock in the n/a?
 

7M-fanatic

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So, does anyone have this loaded, so I don't have to?
I am looking at installing a Tremec 6-speed with .62 6th gear,
and engine RPM at 8000 (almost 13,000 rpm driveshaft speed).

Have just looked up my friends at the Driveshaft Shop, who made my other shaft,
and was planning on calling them tomorrow to ask what his aluminum shafts will take.
 

Piratetip

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I updated the Host link in the original post if anyone still wants to download the calculator :D
 
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debrucer

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I'm getting close to using the one-piece aluminum shaft I bought in 2006, at least 6 months before this thread :(

One thing I had forgotten, the safety loop, was ordered today. I'm hoping for zero issues, too... now one of the possibilities will likely not be pole-vaulting.
 

Piratetip

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Shaftmasters Aluminum D.S.?

I am still running my original Shaftmasters prototype in my car :D
(I have the first driveshaft they ever made for the MKIII Supra platform)
I drove my car to their shop (when I used to live in Michigan still), they stole my 2 piece driveshaft and made me a new one while I had my car on the lift there.
Good bunch of guys there, that was a looooong time ago.

Works good and no vibration, though I also don't regularly do 115MPH either. (Which is where it should be hitting 1/2 critical speed vibrations)
 
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