Author Topic: Flywheels again :)  (Read 12782 times)

Andre Blanchard

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Flywheels again :)
« on: September 25, 2006, 07:50:00 PM »
Not to revive yet another argument but I found some destructive test data on some 24" cast iron flywheels, tests were done in 1899 and are complete with before and after pictures also pics of the test structure.
http://books.google.com/books?vid=0wgP2lF6VG2RCHMny6&id=_DsgCveKE84C&pg=PA168&dq=%22Copyright,+1902%22+intitle:Transactions+intitle:of+intitle:the+intitle:American+intitle:Society+intitle:of+intitle:Mechanical+intitle:Engineers&as_brr=1

It is interesting to note the type of construction of the highest speed wheel.

That book is available as a full download PDF, it is 29M but there is a lot of interesting info in it.
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rpg52

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Re: Flywheels again :)
« Reply #1 on: September 25, 2006, 08:06:51 PM »
What page is the flywheel info on?  I saw open hearth furnaces, manila rope breaking strength, standardize fittings, dam construction, etc., but didn't see the flywheel information.
Ray
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Andre Blanchard

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Re: Flywheels again :)
« Reply #2 on: September 25, 2006, 08:12:05 PM »
The link should have been to the first page of the flywheel data??

Page 168 of the book, page 199 of the PDF.
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oldnslow

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Re: Flywheels again :)
« Reply #3 on: September 25, 2006, 10:13:11 PM »
The document page 168 corresponds to pg 199 in the reader. The section is on pg 199-216 on the acrobat reader. Printed that section to read. A great reference. THANKS.
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Rainbow-Farm

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Re: Flywheels again :)
« Reply #4 on: September 27, 2006, 02:43:50 AM »
The only view I can get is "snippet"... am I missing something? I poked for about 15 minutes, never found the PDF document, or any of its pages.
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Procrustes

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Re: Flywheels again :)
« Reply #5 on: September 27, 2006, 03:58:41 AM »
For those who can't read this, the highlights IMO are that they got solid 24" flywheels up to 3,850rpm which corresponds to 15,600 pounds/inch centrifugal force, rim speed 395 ft/second.  Flywheels consisting of two semicircles bolted together got to half the rpm's and 3,750 pounds/in of force on rim.  Basically joints are a no-no.  A spoked (bicycle style) flywheel hit 4,050 rpm.

EDIT:  the above erroneously read 395 ft/minute.  Fixed it to read ft/second.
« Last Edit: October 06, 2006, 05:54:10 PM by Procrustes »

rcavictim

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Re: Flywheels again :)
« Reply #6 on: September 27, 2006, 05:37:12 AM »
For those who can't read this, the highlights IMO are that they got solid 24" flywheels up to 3,850rpm which corresponds to 15,600 pounds/inch centrifugal force, rim speed 395 ft/minute.  Flywheels consisting of two semicircles bolted together got to half the rpm's and 3,750 pounds/in of force on rim.  Basically joints are a no-no.  A spoked (bicycle style) flywheel hit 4,050 rpm.

I think something is wrong with your 395 ft/minute rim speed figure.  A good ROT I am aware of says 60 MPH rim speed for cast flywheels is considered safe.  That is many times faster than 395 ft/minute.  Did you omit a zero?
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Andre Blanchard

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Re: Flywheels again :)
« Reply #7 on: September 27, 2006, 03:16:40 PM »
The only view I can get is "snippet"... am I missing something? I poked for about 15 minutes, never found the PDF document, or any of its pages.

They have a lot of really good books but the interface really sucks.  The search seems to have a big problem with multiple books having the same title even if they are different volumes and copyright dates.  But the link in my first message still takes me to the page of the book with the 24" wheel tests.
They seem to be making a bunch of changes right now a few full view PDF books I downloaded two weeks ago are now listed in the snippet view, which near as I can tell means they are unsure of the copyright status of the book so they are doing a CYA.



24" Wheel tests.
http://books.google.com/books?vid=0wgP2lF6VG2RCHMny6&id=_DsgCveKE84C&pg=PA168&dq=%22Copyright,+1902%22+intitle:Transactions+intitle:of+intitle:the+intitle:American+intitle:Society+intitle:of+intitle:Mechanical+intitle:Engineers&as_brr=1
Link to PDF
http://books.google.com/books/pdf/Transactions_of_the_American_Society_of_.pdf?vid=0wgP2lF6VG2RCHMny6&id=_DsgCveKE84C&output=pdf&sig=FqK5ohigiYVrOPSrdlOsub8pIog

Title : Transactions of the American Society of Mechanical Engineers
Volume : XXIII
Copyright : 1902
Page of book : 168
Page of PDF : 199


I found some more tests.

48" Wheel tests : This one has a more exciting ending showing that more complicated is not always better.
http://books.google.com/books?vid=0xWDihsZDgGVLv3SIR&id=-PwrQBRs9PYC&pg=PA232&dq=Transactions+of+the+American+Society+of+Mechanical+Engineers+1905&as_brr=1
Link to PDF
http://books.google.com/books/pdf/Transactions_of_the_American_Society_of_.pdf?vid=0xWDihsZDgGVLv3SIR&id=-PwrQBRs9PYC&output=pdf&sig=ggB9DY5k2UJ0T940pGXOLqO_LNc

Title : Transactions of the American Society of Mechanical Engineers
Volume : XXVI
Copyright : 1905
Page of book : 232
Page of PDF : 278



And just to be complete Google has a third volume of that book, that I have found.
No exploding flywheels but lots of good reading.
http://books.google.com/books?vid=0licVnfrTdXHGWE8hB&id=5rlkes-IYrgC&pg=PP13&lpg=PP15&dq=Transactions+of+the+American+Society+of+Mechanical+Engineers+1910&as_brr=1
Link to PDF
http://books.google.com/books/pdf/Transactions_of_the_American_Society_of_.pdf?vid=0licVnfrTdXHGWE8hB&id=5rlkes-IYrgC&output=pdf&sig=RtUNZyt_0wLbOL6qILDk5x20tFU

Title : Transactions of the American Society of Mechanical Engineers
Volume : 31
Copyright : 1910
« Last Edit: September 27, 2006, 03:22:26 PM by Andre Blanchard »
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Procrustes

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Re: Flywheels again :)
« Reply #8 on: September 28, 2006, 06:57:35 AM »
For those who can't read this, the highlights IMO are that they got solid 24" flywheels up to 3,850rpm which corresponds to 15,600 pounds/inch centrifugal force, rim speed 395 ft/minute.  Flywheels consisting of two semicircles bolted together got to half the rpm's and 3,750 pounds/in of force on rim.  Basically joints are a no-no.  A spoked (bicycle style) flywheel hit 4,050 rpm.

I think something is wrong with your 395 ft/minute rim speed figure.  A good ROT I am aware of says 60 MPH rim speed for cast flywheels is considered safe.  That is many times faster than 395 ft/minute.  Did you omit a zero?

That should have been, 395 feet per second.

rcavictim

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Re: Flywheels again :)
« Reply #9 on: September 28, 2006, 08:32:05 AM »
For those who can't read this, the highlights IMO are that they got solid 24" flywheels up to 3,850rpm which corresponds to 15,600 pounds/inch centrifugal force, rim speed 395 ft/minute.  Flywheels consisting of two semicircles bolted together got to half the rpm's and 3,750 pounds/in of force on rim.  Basically joints are a no-no.  A spoked (bicycle style) flywheel hit 4,050 rpm.

I think something is wrong with your 395 ft/minute rim speed figure.  A good ROT I am aware of says 60 MPH rim speed for cast flywheels is considered safe.  That is many times faster than 395 ft/minute.  Did you omit a zero?

That should have been, 395 feet per second.

No wonder it exploded.  That is 4.5 times the safe speed at the circumference and 20 times the safe centrifugal force that the rim can handle in a cast iron wheel.

I was right.  Safe operating rule of thumb for cast iron flywheels is one mile per minute.  That`s about 900 something RPM for a 24 inch wheel.  Steel flywheels with 60,000 PSI steel are safe at 1.9 times the allowable maximums for one piece cast iron wheels.  Very good paper here.  2.5 meg PDF.

http://literature.rustyiron.com/Flywheel_Explosions.pdf
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Procrustes

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Re: Flywheels again :)
« Reply #11 on: October 03, 2006, 03:08:02 AM »

No wonder it exploded.  That is 4.5 times the safe speed at the circumference and 20 times the safe centrifugal force that the rim can handle in a cast iron wheel.

I was right.  Safe operating rule of thumb for cast iron flywheels is one mile per minute.  That`s about 900 something RPM for a 24 inch wheel.  Steel flywheels with 60,000 PSI steel are safe at 1.9 times the allowable maximums for one piece cast iron wheels.  Very good paper here.  2.5 meg PDF.

http://literature.rustyiron.com/Flywheel_Explosions.pdf


Does a 4x safety factor sound about right?  I seem to recall hearing that figure somewhere, but it may be my imagination.

Quinnf

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Re: Flywheels again :)
« Reply #12 on: December 21, 2006, 08:28:41 PM »
There's a section in Machinery's Handbook that discusses safe working speeds for flywheels.  5000 ft/minute surface speed is what they recommend, if my memory's right, so a mile a minute or 60 mph is about right.  However that's for good quality cast iron, of a given tensile strength, not the recycled stuff they cast flywheels from in India. 

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Andre Blanchard

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Re: Flywheels again :)
« Reply #13 on: December 21, 2006, 11:07:57 PM »
There's a section in Machinery's Handbook that discusses safe working speeds for flywheels.  5000 ft/minute surface speed is what they recommend, if my memory's right, so a mile a minute or 60 mph is about right.  However that's for good quality cast iron, of a given tensile strength, not the recycled stuff they cast flywheels from in India. 

Quinn

And I would guess the Machinery's Handbook editors were looking at the ASME data from these 1898 tests when they came up with that safe speed.
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rcavictim

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Re: Flywheels again :)
« Reply #14 on: December 21, 2006, 11:12:43 PM »
Grinder disc explodes!

I just had my own flywheel explosion of sorts and in a demonstration as fast as a gunshot I was reminded of the power and potential dangers of centrifugal force.

I had just started to use a handheld angle grinder today that I had been using yesterday when the 4 inch abrasive wheel, about 1/3rd worn, exploded suddenly with no warning. The disk had not been subjected to any unusual forces or unusual use.  Fortunately I was not viewing the disc edge on as I sometimes did in the past (will reconsider this) and the guard saved me from the lightning fast, glass sharp shrapnel.  Without the guard this could have potentially killed me.  I found one piece which is a 1/3rd pie section of the whole and has the label still attached on it.

The grinder was a Chinese brand of which I am actually quite happy with.  The 4 inch disc that exploded is marked on the piece I have as rated at 13,500 RPM Max. was also the same Chinese  branded item made for the high speed grinder I was using.  I`m quite sure the grinder is nowhere near that fast.  Must check this. I am not going to discuss the brand at this time in case litigation happens.

I am 52.  I have been using angle grinders actively all my life since I was 16 years of age.  I have never ever had an abrasive wheel explode on me, never!  The discs I have used in the past were always North American or Japanese brands.  My use of Chinese power tools is a fairly recent adventure.
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