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JuddJones

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Posts: 382
Reply with quote  #31 
Quote:
Originally Posted by Danny Harvey
Big J,

It doesn't take long.

So they had a big sprocket on the motor and a little one on the arbor? In addition to bearing a bearing killer, depending on the diameters, that drive would also likely require special construction because of the linear speed. 

I can't say I'm glad that someone else had the same problem but it is nice to know it's not just me.[smile]



That is correct. 1800 RPM motor, 4500 RPM arbor. The rep was onsite to show off his new toy, and he assured the millwrights that was the proper tension. They didn't agree and were proven correct. Can you elaborate on the special construction linear speed part. I can't help but feel this is an opportunity for me to learn something about belt drives.
Danny Harvey

Sr. Member / Moderator / Supporter
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Posts: 1,402
Reply with quote  #32 
For most standard sheaves. timing belt pulleys and HTD sprockets like made by Gates or TB Woods there is a maximum rim speed of 6500 fpm stamped into the item.

If you use the formula fpm=rpm * pitch diameter * .262 and that number comes in at under 6500 fpm, you will be ok with standard stuff which is made from Series 30 Grey Iron and statically balanced.  Over 6500 fpm, it will require dynamic balance and construction from Series 50 Grey Iron or steel.

So in your case you may have a 10" motor sprocket and a 4" diameter arbor sprocket.

FPM=1780 * 10 * .262 = 4663.6 fpm which would be ok except that the 4" diameter sprocket will likely result in a high overhung load on the bearing.


JuddJones

Sr. Member
Registered:
Posts: 382
Reply with quote  #33 
Quote:
Originally Posted by Danny Harvey
For most standard sheaves. timing belt pulleys and HTD sprockets like made by Gates or TB Woods there is a maximum rim speed of 6500 fpm stamped into the item.

If you use the formula fpm=rpm * pitch diameter * .262 and that number comes in at under 6500 fpm, you will be ok with standard stuff which is made from Series 30 Grey Iron and statically balanced.  Over 6500 fpm, it will require dynamic balance and construction from Series 50 Grey Iron or steel.

So in your case you may have a 10" motor sprocket and a 4" diameter arbor sprocket.

FPM=1780 * 10 * .262 = 4663.6 fpm which would be ok except that the 4" diameter sprocket will likely result in a high overhung load on the bearing.



Thank you sir!
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