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If you have access to the actual original factory drawings of the 2, 3 or 4 step V-pulleys typically used on machine tools, you may find that the V-angle is smaller on the smallest diameter step than it is on the largest.?? And that in the case of 3 or 4-step ones, the angle(s) on the in-between steps are in between.?? This is to compensate for the ID being wider when the belt is bent around a smaller diameter.?? Whether this is true of the Taiwan and/or Chinese made pulleys on the 4x6 band saws, I don?€?t know.?? I?€?ve never looked at any of them that closely.?? They should be but may or may not be.?? I?€?ll skip commenting on link-belts versus V-belts.
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Robert Downs
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From: [email protected] [ mailto:[email protected]] On Behalf Of John Vreede
Sent: Saturday, August 22, 2020 15:34
To: [email protected]
Subject: Re: [4x6bandsaw] Drive belt tension
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It occurred to me why the differences in belt performance are not that noticeable.
The 4x6's pulleys are not made to standard so the belt wont be able to transmit as much power as its capable of, but a 4x6 is not using much power anyway.
When the belt bends around the small 48mm pulley it will fatten up on the inside of the bend since the belt cords are all on the outside.? It won't fit in the bottom of the 36deg vee (where it would have if the vee was only 31deg) so the belt will just ride a little higher up the vee? than it should, and the speed increase you should get, won't be as great.? The saw won't run quite as fast. but you wont even notice.??
Gary's post shows the range of machinery where A-section belts are used, the Tormach is rated at 1.5HP and jointers, table saws etc can be 3HP, where a 4x6 is only 1/2HP at best.? HF and others claim 1HP motors (High-school physics says Volts times Amps = Watts and there are 746W in a Horsepower, so if the motor draws 6.8A @ 110V = 748W - Hey that's 1HP!), but that is INPUT power not output, so at 30-40% efficiency the HF's motor is only a bit over 1/3HP at best.
NEMA and IEC rate induction motors as 'HP output at a given rpm', i.e 1/2HP @ 1425rpm.? When you load them up so the revs drop below 1425, they give correspondingly higher HP, so a 1/2HP motor might be giving more than 1HP just before it stalls. 4x6's are rarely loaded up so much, you have to be running 12lb bow weight on high speed to stall at the end of a cut? And then its only transmitting ~1HP, when 1/2" A-section belts can transmit 5HP.?
When running near the limit of the belt's power transmission capacity, then Gates and Dayco belts win out over cheap OEM belts every time. Fennerflex belts are unparalleled if you have to dismantle the whole machine just to replace the belt (as I would have had to do recently on a friend wood lathe - Fennerflex saved the day),? or have lots of machines all running A-section belts, then you willingly pay the extra cost - jv??