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Decided to build my own Wet Tumbler - Have RPM & Pulley Questions
5/11/2012 6:35:24 PM
All the pretty brass bling has convinced me that I need want a wet tumbler.
I have a "new" (as in old stock from a hardware store that went out of business) 1/3 HP motor. The plate indicates that it is 1725 RPM.
My question is how to step down the RPMs for the tumbler. According to http://www.culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html if I use a pulley with a 1.5" diameter on the motor shaft (assuming I could even find one that small), I would need a pulley with a 26 inch diameter to get down to 100 RPM. This does not seem to match the what I have seen in other threads.
Does the diameter of the Drum effect the RPM (it would seem to)? My plan is to use pillow block bearings to hold two shafts. One of the shafts would be connected to a pulley which would connected by a V-belt to the drum. (Like this setup: http://www.ar15.com/forums/t_6_42/369783_YAWTBT__Yet_Another_Wet_Tumbler_Build_Thread_.html except without the drive second set of pulleys driving the second shaft). The Drum would then set on top of the shafts and be driven by friction.
I am looking for some feedback on pulley sizes and RPMs.
Also, with a 1/3 HP motor (rated for continuous use), could I use a 5 Gallon Bucket as the starting point for my Drum and expect it to have enough power to get is going?
In my prior life, I was a chemist, so all this engineering is beyond me. 
I am going to try to make my base out of wood (OSB) and will take pictures of my build (as well as any injuries) for posting.
Thank you!
5/11/2012 6:59:21 PM
in
5/11/2012 7:48:25 PM
you will want a 4 or 5 inch pulley. for 6 and 8" drums
you have to consider the shaft diameter as a pulley as it turns the drum. so you have to figure both ratios. this was discussed in my tumbler thread and a couple others.
i run the 1725 motor with a 1.5 drive pulley and 4" driven pulley. that gives me 70-80 rpm with 6" drum and 60 or so rpm with and 8" drum.
for example my shaft with hose on it makes it .75 diameter then you have a 6" drum
with the 1725rpm motor and 1.5 and 4 inch pulleys that give you 647 rpm shaft speed
when you plug the 647rpm for rpm 1 and .75 for pulley diameter 1 then input the drum size 6" for pulley 2 you get 80.88 drum rpm
you have to consider the shaft diameter as a pulley as it turns the drum. so you have to figure both ratios. this was discussed in my tumbler thread and a couple others.
i run the 1725 motor with a 1.5 drive pulley and 4" driven pulley. that gives me 70-80 rpm with 6" drum and 60 or so rpm with and 8" drum.
for example my shaft with hose on it makes it .75 diameter then you have a 6" drum
with the 1725rpm motor and 1.5 and 4 inch pulleys that give you 647 rpm shaft speed
when you plug the 647rpm for rpm 1 and .75 for pulley diameter 1 then input the drum size 6" for pulley 2 you get 80.88 drum rpm
5/11/2012 8:54:31 PM
You're forgetting the the larger pulley is driving a (relatively) tiny shaft that the drum sits in.
You don't need to drive the shaft at 100 RPM. Think of it's circumference in relation to that of your drum.
5/11/2012 10:18:51 PM
Rotation of the motor will also play a role in how effectively your tumbler will be able to rotate a heavy drum. Take my build for example where my motor has a clockwise rotation. Placing the v-belt on a pulley closest to the motor will also spin the pulley and shaft clockwise and will have the effect of "pushing down" on the barrel. Placing the v-belt on a pulley farthest from the motor will also spin the pulley and shaft clockwise but will have the effect of "pushing up" on the barrel. In another forum where they discuss building similar devices called ball mills, it was observed that pushing up in a single drive system was more effective in getting the heavy barrel spinning then pushing down. By using secondary pulleys to spin the second shaft, I can mount my motor to the right side of my frame and connect it the closest pulley. For me the orientation is specefic to how and where i will finally have the tumbler located in my shop.
Hopefully I did this right and Biggdawg will jump in and correct me if it's wrong:
Here's how I arrived at my barrel rotation RPM:
Motor speed: 1750rpm (RPM 1)
Motor pulley: 2" (Diameter 1)
Drive Pulley: 6" (Diameter 2)
Plugin the numbers and calculate RPM 2
RPM 1: 583.3
Shaft diameter with rubber hose: 0.625" (Diameter 1)
Diameter of barrel endcaps: 5" (Diameter 2)
Plugin the numbers and calculate RPM 2, final barrel rotation
Hopefully I did this right and Biggdawg will jump in and correct me if it's wrong:
Here's how I arrived at my barrel rotation RPM:
Motor speed: 1750rpm (RPM 1)
Motor pulley: 2" (Diameter 1)
Drive Pulley: 6" (Diameter 2)
Plugin the numbers and calculate RPM 2
RPM 1: 583.3
Shaft diameter with rubber hose: 0.625" (Diameter 1)
Diameter of barrel endcaps: 5" (Diameter 2)
Plugin the numbers and calculate RPM 2, final barrel rotation
5/11/2012 10:57:04 PM
Originally Posted By 808state:
Rotation of the motor will also play a role in how effectively your tumbler will be able to rotate a heavy drum. Take my build for example where my motor has a clockwise rotation. Placing the v-belt on a pulley closest to the motor will also spin the pulley and shaft clockwise and will have the effect of "pushing down" on the barrel. Placing the v-belt on a pulley farthest from the motor will also spin the pulley and shaft clockwise but will have the effect of "pushing up" on the barrel. In another forum where they discuss building similar devices called ball mills, it was observed that pushing up in a single drive system was more effective in getting the heavy barrel spinning then pushing down. By using secondary pulleys to spin the second shaft, I can mount my motor to the right side of my frame and connect it the closest pulley. For me the orientation is specefic to how and where i will finally have the tumbler located in my shop.
Hopefully I did this right and Biggdawg will jump in and correct me if it's wrong:
Here's how I arrived at my barrel rotation RPM:
Motor speed: 1750rpm (RPM 1)
Motor pulley: 2" (Diameter 1)
Drive Pulley: 6" (Diameter 2)
Plugin the numbers and calculate RPM 2
http://i459.photobucket.com/albums/qq314/d3vnu11/Wet%20Tumbler/calc1.jpg
RPM 1: 583.3
Shaft diameter with rubber hose: 0.625" (Diameter 1)
Diameter of barrel endcaps: 5" (Diameter 2)
Plugin the numbers and calculate RPM 2, final barrel rotation
http://i459.photobucket.com/albums/qq314/d3vnu11/Wet%20Tumbler/calc2.jpg
Rotation of the motor will also play a role in how effectively your tumbler will be able to rotate a heavy drum. Take my build for example where my motor has a clockwise rotation. Placing the v-belt on a pulley closest to the motor will also spin the pulley and shaft clockwise and will have the effect of "pushing down" on the barrel. Placing the v-belt on a pulley farthest from the motor will also spin the pulley and shaft clockwise but will have the effect of "pushing up" on the barrel. In another forum where they discuss building similar devices called ball mills, it was observed that pushing up in a single drive system was more effective in getting the heavy barrel spinning then pushing down. By using secondary pulleys to spin the second shaft, I can mount my motor to the right side of my frame and connect it the closest pulley. For me the orientation is specefic to how and where i will finally have the tumbler located in my shop.
Hopefully I did this right and Biggdawg will jump in and correct me if it's wrong:
Here's how I arrived at my barrel rotation RPM:
Motor speed: 1750rpm (RPM 1)
Motor pulley: 2" (Diameter 1)
Drive Pulley: 6" (Diameter 2)
Plugin the numbers and calculate RPM 2
http://i459.photobucket.com/albums/qq314/d3vnu11/Wet%20Tumbler/calc1.jpg
RPM 1: 583.3
Shaft diameter with rubber hose: 0.625" (Diameter 1)
Diameter of barrel endcaps: 5" (Diameter 2)
Plugin the numbers and calculate RPM 2, final barrel rotation
http://i459.photobucket.com/albums/qq314/d3vnu11/Wet%20Tumbler/calc2.jpg
you did it perfect from what i see.
5/11/2012 11:13:27 PM
Thanks for checking!
5/12/2012 10:11:27 AM
I'm in also. This thread is off to a fine start. Well done guys.
