deflection and critical speeds of a stepped shaft 1

[paulratledge]

I would really love an equation to figure out the deflection of a rotating shaft.
The shaft is 76" from bearing to bearing.
9" at 2.950" diameter
64" at 9.685" d
9.5" at 2.95" d
the 64"section is a hollow shaft and has about 52" at 3"d missing from middle.
density of material is .28lb/in^3 and we spin it at about 3000rpm.

there is no 'load' so to speak of on the object besides the weight of the object its self which if you calculate the volume and density is about 880lbs.
criticals would also be lovely. thank you

 

[paulratledge]

Hey electric.On the first excel you posted.. How can I change the calculations using a bearing coefficient of 1.52?

 

[electricpete]

I think you are wanting to change the bearing multiplier?

If so, here’s what I did to produce the attached.
Delete all the old tabs with multipliers 0.1, 1, 10, 100, etc.
On main tab, edit the list of multipliers to include 1.52.
On main tab, press grey “RUN..” button.
Wait for program to tell me it’s done.
On tab “outsheet”, highlight the cells of interest. In this case for multiplier 1.52, we highlight A44

On tab “outsheet”, press grey button “TO PLOT A MODESHAPE...”
This creates a new tab (sheet 1 or somethign like that). Rename tab sheet1 as 1.52
Done.


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(2B)+(2B)' ?

 

[paulratledge]

I found a couple places where the id and the od in your charts isnt as exact as I want it. Should I be changing values in rotor section tab and or rotor picture? Id also like to play with the density a bit.

Thanks

 

[paulratledge]

I noticed on the rotor section tab that you divide the inches by 39.97 is this an error or should it be 39.3700787?

 

[paulratledge]

Here is the first two tabs changed a bit. let me know what you think

 

[electricpete]

Yes, should be 39.37

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[paulratledge]

I am having a hard time getting the buttons to work or I am doing it wrong. If you could throw me a couple tips or do I need to buy another version of excel. I have office pro now.

Thanks

 

[electricpete]

When I tried to "run" the file you posted, I got an error message suggesting problem with the data in rotor tab. There was extra data below (sum of lengths). When I removed that, I ran the program and then generated a modeshape plot for multiplier 1.54. Maybe that will fix your problem.

I also un-hid the tab entitled instructions, which gives lengthy instructions. Maybe it will give some help. I used to have a website to accompany this program (with many examples showing how the program was validated), but it got lost when I switched ISP's. At one time I had ambitions of selling the program, but now I realize that's silly. fwiw, I am working on another version based on direct stiffness method with more capabilities.

I have only tested it in Excel 2000 and 2003.

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[electricpete]

Here is a file extracted from the webpage that shows some of the validations. I'm not sure if links will work.

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[electricpete]

Here is another file from my old website that shows the basic transfer matrix algorithm (nothing that I invented). Might be handy if you have the inclination to program it yourself.

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[paulratledge]

Does the rotor picture affect the calculations?

 

[electricpete]

Does the rotor picture affect the calculations?

No, the rotor profile picture is a static graph generated from the rotor description. If you change the rotor description after generating the picture (as we did), the picture doens't change (you have to delete the picture tab and re-generate rotor picture using "generate rotor profile button"

(In a similar way, the mode shape plots are static).

Attached I have updated both the rotor profile picture and the modeshape to match the current rotor description (as you modified it).

Does the program work in your version of excel, now that the extra stuff in the rotor tab was deleted?




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(2B)+(2B)' ?

 

[paulratledge]

I still dont think I can press any "buttons" so to speak. Finally got actual picture of inside of my object and found out that the ID of hollow portion is 6" ID and the section is 56.5" long. I finally got a weight of 925.66lbs using .285 as my density. Those dimensions change the size quite a bit.