catskillrocks
fully equipped rock polisher
Member since July 2008
Posts: 1,270
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Post by catskillrocks on Aug 31, 2021 15:33:37 GMT -5
I inherited a home built tumbler that turns a Lorotone QT66 a mere 14 RPM. There is no RPM information for the motor. The pulley on the motor is 1-5/8" and the one that turns the barrel is 11" and the shaft that it is connected to is 5/8". The diameter of the QT66 is 7-1/2"
I was thinking of changing the 11" pulley to a 9" pulley just hoping that it would give me a 28 - 35 RPM for the barrel. I looked at different threads that give a formula for figuring this out but I am stumped. So would a 9" pulley get me to where I want? Thanks in advance.
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AzRockGeek
has rocks in the head
Member since September 2016
Posts: 635
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Post by AzRockGeek on Aug 31, 2021 15:46:24 GMT -5
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Post by oregon on Aug 31, 2021 15:59:56 GMT -5
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catskillrocks
fully equipped rock polisher
Member since July 2008
Posts: 1,270
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Post by catskillrocks on Aug 31, 2021 17:24:30 GMT -5
Thank you AzRockGeek and oregon . I did search and found Chuck's Excel spread sheet, but it was a read only. On the gadi.agric.za/software/renting/pulley_calc.php one I do not know the shaft speed of the motor. Assuming that it is 1750 RPM and the shaft speed on the 11" pulley is 14 RPM, and the pulley at 1.5" turning at 1750 RPM my numbers just don't make any sense.
I'm obviously doing something wrong,
but I don't know what.
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AzRockGeek
has rocks in the head
Member since September 2016
Posts: 635
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Post by AzRockGeek on Aug 31, 2021 19:03:09 GMT -5
Throwing your numbers in excel, your tumbler should be turning ~21 RPM, if you go with a 9" 2nd pulley you would be around 26 RPM. Assuming it is a 1750 RPM motor.
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Post by oregon on Aug 31, 2021 19:03:51 GMT -5
It's all simple ratios, so if it's 14 rpm now, you'd have to half the diameter of the pulley to get 28 rpm.
Calculations are never exact as belts will ride at different diameters,slippage etc etc etc, but in the ball park. not likely, but your motor could be 1050 rpm's too? download a strobe light app for your phone and put a tick mark on your motor pulley if you want to know the rpm. (can use it for the barrel too) I have strobily here on my phone, but there are heaps.
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AzRockGeek
has rocks in the head
Member since September 2016
Posts: 635
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Post by AzRockGeek on Aug 31, 2021 19:16:20 GMT -5
If you are using a two speed evaporative cooler type motor, the low speed is around 1120 RPM which would give you the 14 RPM you are seeing. A 9" pully would put it around 17 RPM, to get in the 25 RPM range use a 6" pulley.
Hope this helps. Tim
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catskillrocks
fully equipped rock polisher
Member since July 2008
Posts: 1,270
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Post by catskillrocks on Sept 1, 2021 16:09:26 GMT -5
Again, thank you to AzRockGeek and oregon . I had no idea that you could use your phone as a strobe light. The motor runs at 3600rpm. I'll get the rpm of the 2nd pulley and try figuring it out from there. Thanks again.
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Post by oregon on Sept 1, 2021 16:27:59 GMT -5
seems more likely to be half of that 1800 (1750) rpm?
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