Tommy
Administrator
Member since January 2013
Posts: 12,881
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Post by Tommy on Sept 13, 2018 19:22:06 GMT -5
I have a slow speed flat lap with a gear motor spinning at 30 RPMs (yes 30) running a 4" pulley motor side to a stepped 2" pulley on the table - table is running at 60 RPM's yes?
I want a bit more speed and I can fit an 8" pulley motor side and line it up with the 3" step on the table side pulley. What would the new RPM's of the table be?
The bonus question is with the 8" pulley and the 3" pulley located shaft center 10.5 inches from each other - what size V-belt would I need?
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Post by johnjsgems on Sept 13, 2018 19:37:32 GMT -5
80 rpm shaft speed of equipment. Motor rpm X motor pulley diameter divided by equip pulley diameter. Belt size is harder. Easiest way is to use a string, wrap around outside of both pulleys then lay flat and measure. Helpful if you have adjustment capability. Or can exchange belt if off a little.
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Post by oregon on Sept 13, 2018 20:00:11 GMT -5
The bonus question is with the 8" pulley and the 3" pulley located shaft center 10.5 inches from each other - what size V-belt would I need? Wonder if Siri could figure that one out? lots of vbelt calculators out there... www.calculatoredge.com/mech/vbelt%20length.htm
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Post by aDave on Sept 13, 2018 20:28:43 GMT -5
The bonus question is with the 8" pulley and the 3" pulley located shaft center 10.5 inches from each other - what size V-belt would I need? Wonder if Siri could figure that one out? lots of vbelt calculators out there... www.calculatoredge.com/mech/vbelt%20length.htm Link is bad.
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Post by stardiamond on Sept 13, 2018 20:50:27 GMT -5
I don't know pulleys but I thought geometry would be the ratio of the squares of the radii or 4 times.
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Post by Rockoonz on Sept 13, 2018 20:58:09 GMT -5
I have a slow speed flat lap with a gear motor spinning at 30 RPMs (yes 30) running a 4" pulley motor side to a stepped 2" pulley on the table - table is running at 60 RPM's yes? I want a bit more speed and I can fit an 8" pulley motor side and line it up with the 3" step on the table side pulley. What would the new RPM's of the table be? The bonus question is with the 8" pulley and the 3" pulley located shaft center 10.5 inches from each other - what size V-belt would I need? Message me an email and I can shoot you a spreadsheet calculator that can tell you everything including belt length. Lots of other fun stuff too.
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Post by aDave on Sept 13, 2018 21:00:23 GMT -5
I have a slow speed flat lap with a gear motor spinning at 30 RPMs (yes 30) running a 4" pulley motor side to a stepped 2" pulley on the table - table is running at 60 RPM's yes? I want a bit more speed and I can fit an 8" pulley motor side and line it up with the 3" step on the table side pulley. What would the new RPM's of the table be? The bonus question is with the 8" pulley and the 3" pulley located shaft center 10.5 inches from each other - what size V-belt would I need? Message me an email and I can shoot you a spreadsheet calculator that can tell you everything including belt length. Lots of other fun stuff too. I thought someone here had something, though I couldn't recall who. Thanks for the reminder.
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Post by Rockoonz on Sept 13, 2018 21:02:00 GMT -5
Message me an email and I can shoot you a spreadsheet calculator that can tell you everything including belt length. Lots of other fun stuff too. I thought someone here had something, though I couldn't recall who. Thanks for the reminder. It's from a member who lives near me and is a millwright engineer type.
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Tommy
Administrator
Member since January 2013
Posts: 12,881
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Post by Tommy on Sept 13, 2018 21:03:16 GMT -5
Holy cow that interweb thing sure makes it easy
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,687
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Post by NRG on Sept 16, 2018 14:10:05 GMT -5
That calculator made my belts 1" too long on all setups. YMMV
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Post by aDave on Sept 16, 2018 14:52:45 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Interesting. I just grabbed it off the 'net as it seemed to have all the numbers that Tommy was looking for. I've never used it myself.
How did you overcome the error? Did you just get an adjustable belt? I know they are much more expensive than a standard belt, but it would seem they might help with any initial calculation error, especially if there isn't much room for movement/adjustment.
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Tommy
Administrator
Member since January 2013
Posts: 12,881
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Post by Tommy on Sept 16, 2018 14:57:46 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Could it have been an ID vs. OD thing? I've done that before where I tie a string and then measure it but the belt measurement was the OD and I was off. In this particular machine the motor is held by two bolts, each in their own 1.25" sliding hole, and I measured the 10.5" c-to-c from the closed-most position. I wonder how much leeway that buys me - I guess I could go measure the c-to-c in the open-most position.
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Tommy
Administrator
Member since January 2013
Posts: 12,881
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Post by Tommy on Sept 16, 2018 15:00:15 GMT -5
P.s. I have the belt already - based on that calculator - but I don't have the pulley yet or I'd just run out and try it.
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Post by Rockoonz on Sept 16, 2018 16:38:52 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Interesting. I just grabbed it off the 'net as it seemed to have all the numbers that Tommy was looking for. I've never used it myself. How did you overcome the error? Did you just get an adjustable belt? I know they are much more expensive than a standard belt, but it would seem they might help with any initial calculation error, especially if there isn't much room for movement/adjustment.
Don't use link belts for anything that must not stretch or slip. They stretch a lot and have significantly less contact area to the v pulleys, which causes slippage. I had recurring issues with my 18 inch HP saw until I replaced it.
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Post by aDave on Sept 16, 2018 20:20:11 GMT -5
Interesting. I just grabbed it off the 'net as it seemed to have all the numbers that Tommy was looking for. I've never used it myself. How did you overcome the error? Did you just get an adjustable belt? I know they are much more expensive than a standard belt, but it would seem they might help with any initial calculation error, especially if there isn't much room for movement/adjustment.
Don't use link belts for anything that must not stretch or slip. They stretch a lot and have significantly less contact area to the v pulleys, which causes slippage. I had recurring issues with my 18 inch HP saw until I replaced it. That's good to know. I've only been grabbing stuff off the 'net in the event it might help. It's looking more and more that I shouldn't be adding to the conversation. Thanks for the heads up.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,687
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Post by NRG on Sept 16, 2018 20:45:29 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Interesting. I just grabbed it off the 'net as it seemed to have all the numbers that Tommy was looking for. I've never used it myself.
How did you overcome the error? Did you just get an adjustable belt? I know they are much more expensive than a standard belt, but it would seem they might help with any initial calculation error, especially if there isn't much room for movement/adjustment.
I simply bought another belt. They cost <$5 ea
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,687
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Post by NRG on Sept 16, 2018 20:47:20 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Could it have been an ID vs. OD thing? I've done that before where I tie a string and then measure it but the belt measurement was the OD and I was off. In this particular machine the motor is held by two bolts, each in their own 1.25" sliding hole, and I measured the 10.5" c-to-c from the closed-most position. I wonder how much leeway that buys me - I guess I could go measure the c-to-c in the open-most position. I used the dimensions of pulleys as purchased.
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Post by johnjsgems on Sept 18, 2018 11:29:20 GMT -5
Most common belts are "4L" or "A" which fit 1/2" wide pulleys. Buy pulleys that match the width of belt you have.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,687
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Post by NRG on Sept 19, 2018 22:07:29 GMT -5
That calculator made my belts 1" too long on all setups. YMMV Could it have been an ID vs. OD thing? I've done that before where I tie a string and then measure it but the belt measurement was the OD and I was off. In this particular machine the motor is held by two bolts, each in their own 1.25" sliding hole, and I measured the 10.5" c-to-c from the closed-most position. I wonder how much leeway that buys me - I guess I could go measure the c-to-c in the open-most position. Certainly buys you the inch even if you measured from the middle
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,352
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Post by quartz on Sept 19, 2018 23:08:07 GMT -5
I just did it my way and came up with a 38.25" belt. Works better than the calculator. Not dead on, but I've found it to be very close on many projects, and it's easy. 1/2 of each pulley circumference [on outside, or marked diameter] + twice the c-to-c of the shafts.
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