peterd51
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Hi,
I've got one of these electonic 'laser' rpm counters to play with, off ebay, and just tried it on my pillar drill.
The drill was set up on the second pulley, out of four available, and the chuck was running at 1190 rpm. So I dropped it to its lowest pulley and it runs at 480 rpm. But how accurate will this be...
imagine the chuck is a couple of inches diameter, so about six inches circumference. The counter sees the refective strip whizz past at so many times a second. But if the chuck was four inches diameter, and 12 inches circumference, then would it read half the revs per second?
Sounds a reasonable assumption to me. There's nothing in the instructions about chuck sizes, etc. Chinese...
On the pillar drill the motor is a 1/3hp, marked up as 1450 rpm so do my readings for the two lowest pulleys sound about right?
I guess I could 'calibrate' the tester by using the car...stick a bit of strip on the bottom pulley at 1" circumference and run the engine at tick-over, I know that's 900rpm. Then try it again with the strip at 2" and again at 3", etc.
Or maybe try my B&D power drill as I'm sure that has the rpm marked on the case?
What do you reckon?
Regards
Peter
I've got one of these electonic 'laser' rpm counters to play with, off ebay, and just tried it on my pillar drill.
The drill was set up on the second pulley, out of four available, and the chuck was running at 1190 rpm. So I dropped it to its lowest pulley and it runs at 480 rpm. But how accurate will this be...
imagine the chuck is a couple of inches diameter, so about six inches circumference. The counter sees the refective strip whizz past at so many times a second. But if the chuck was four inches diameter, and 12 inches circumference, then would it read half the revs per second?
Sounds a reasonable assumption to me. There's nothing in the instructions about chuck sizes, etc. Chinese...
On the pillar drill the motor is a 1/3hp, marked up as 1450 rpm so do my readings for the two lowest pulleys sound about right?
I guess I could 'calibrate' the tester by using the car...stick a bit of strip on the bottom pulley at 1" circumference and run the engine at tick-over, I know that's 900rpm. Then try it again with the strip at 2" and again at 3", etc.
Or maybe try my B&D power drill as I'm sure that has the rpm marked on the case?
What do you reckon?
Regards
Peter