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Thread: v belts

  1. #11
    Supporting Member Frank S's Avatar
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    One big limiting factor in your design is not going to be the belt versus the capacity of the motor but the diameter of your shaft.
    @ 20mm shaft diameter with a 40 mm vertical travel your sanding drum diameters are going to be limited. which will mean you will not be able to take full advantage of the available power you will have.
    You would probably need a shaft more like 30 mm in diameter to take full advantage of your 2300 watt motor then you could use a 100 mm drum or possibly larger.
    But you wold need either 2 10mm belts or a single 15 mm belt with a small pulley diameter of 90 mm or larger.
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  2. #12
    Supporting Member jonnydot's Avatar
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    The motor arrived today and it has no id plate so I done some investigation and the most likely rpm is 2850 second guess is 1450rpm both these motors can be found with a 3.15hp size .I pulled the pump off and it has an unusual shaft with 2 flats ,measuring over the flats looks to be 8.1mm and over the rounds it looks to be 10mm.This is presenting a problem sourcing the pulley but I guess I could drill and tap 2 grub screws to rest in 2 small holes drilled into the flats to match and get a pulley with a 10mm bore? I also looked into spindle sanders rpm and most seem to be @ 1750rpm with oscillations from 60-90 rpm ,so raising a pulley size may not be a good idea? However when they are in drill press they would run faster than that ? I ordered the chuck and collets today I am using a C20 ER20 100L and I will reduce the length to about 50 mm and connect it to the shaft with a cnc flexible shaft coupler 40x 65@20mm ID Here is a link to where I got the basics of this design DIY Oscillating Spindle Sander • WoodArchivist Most of the timber will be replaced with steel and more modern bits and bobs

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  4. #13
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    Quote Originally Posted by Frank S View Post
    One big limiting factor in your design is not going to be the belt versus the capacity of the motor but the diameter of your shaft.
    @ 20mm shaft diameter with a 40 mm vertical travel your sanding drum diameters are going to be limited. which will mean you will not be able to take full advantage of the available power you will have.
    You would probably need a shaft more like 30 mm in diameter to take full advantage of your 2300 watt motor then you could use a 100 mm drum or possibly larger.
    But you wold need either 2 10mm belts or a single 15 mm belt with a small pulley diameter of 90 mm or larger.
    you think the 20mm shaft might bend? and I have been thinking that I should increase the vertical travel

  5. #14
    Supporting Member Frank S's Avatar
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    A lot will depend on the maximum diameter and length of the sanding drums
    I used to have a Commercial drum sander similar in function of what you are wanting to build it had a large 3 Hp motor T184 frame size 1.125" (28.575 mm) shaft diameter
    the spindle was 1.5" (38.1 mm) with a vertical travel of 3" ( 76.2 mm)
    it was made for maximum of 4" drums.
    I am thinking that you are probably not looking for anything near to a machine like that
    Your motor had me wondering though it having only a 10 mm diameter shaft that is not consistent with a motor that would have a 2300 watt capacity.
    it sounds more like a 230 to 400 watt motor.
    if you go with a shaft made of say or equivalent 4140 then I should think that 20 mm would be fine for sanding drums up to around 40 mm
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  6. #15
    Supporting Member jonnydot's Avatar
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    Stripped down the motor some more and the shaft is 14mm then up to the 2 flats ,measuring over the flats looks to be 8.1mm and over the rounds it looks to be 10mm and then the thread v belts-42221607_515770605513286_8079687778540978176_n.jpg v belts-42156897_286304858871311_2964122738182062080_n.jpg I also pulled the switch box apart to see if there was any identification inside (there wasn't ) v belts-42272316_549602768809237_1094022384693805056_n.jpg

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    Supporting Member Frank S's Avatar
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    A fun little trick that manufactures love to play on the consumer is to state the HP (wattage) rating of their motors based on the start up amperage. then call it peak hp.
    I'm no EE but I have found that this is often times about 2.5 to 3 times the actual full load running hp @ 85% efficiency. This is not to say that a 12 to 1500 watt motor will not put out over 3 hp for brief periods of time because it will and then some or at least until there is significant thermal rise then it will rapidly degrade.
    Your motor has a 14 mm shaft that has been turned down to a smaller size this would be consistent with a manufacture knowing their product is going to be used at around 1/2 or less the rating they state on the motor for most of the time.
    Just like the manufactures of hydraulic power units for automotive lifts most motors will have a rating of 2.5 to 3 hpthe actual HP of the motor according to NEMA rating would only be 2 HP. The shafts will be machined very similar to your's in size or have a slot cut across the end the little pumps will have an out put of 3.3 CC per revolution . but they will have the max pressure setting at 3000 PSI which at that flow rate would require double the amount of power the motor is rated for. They also know that the motor is capable of this output for a brief period of time and the average amount of time required per cycle will be within the limits of the overload protection. Some will install a larger run capacitor and post a 4 HP rating on their motors.
    Without actually installing a flywheel on your motor and running a friction load test while monitoring the amperage draw and temperature rise there is no real way of knowing the true power output of your motor. but I suspect that it would be somewhere in the range of 14 to 1500 watts @ 85% efficiency continuous. and 40°c thermally protected.
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  9. #17
    PJs
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    Quote Originally Posted by Frank S View Post
    A fun little trick that manufactures love to play on the consumer is to state the HP (wattage) rating of their motors based on the start up amperage. then call it peak hp.
    I'm no EE but I have found that this is often times about 2.5 to 3 times the actual full load running hp @ 85% efficiency. This is not to say that a 12 to 1500 watt motor will not put out over 3 hp for brief periods of time because it will and then some or at least until there is significant thermal rise then it will rapidly degrade.
    Your motor has a 14 mm shaft that has been turned down to a smaller size this would be consistent with a manufacture knowing their product is going to be used at around 1/2 or less the rating they state on the motor for most of the time.
    Just like the manufactures of hydraulic power units for automotive lifts most motors will have a rating of 2.5 to 3 hpthe actual HP of the motor according to NEMA rating would only be 2 HP. The shafts will be machined very similar to your's in size or have a slot cut across the end the little pumps will have an out put of 3.3 CC per revolution . but they will have the max pressure setting at 3000 PSI which at that flow rate would require double the amount of power the motor is rated for. They also know that the motor is capable of this output for a brief period of time and the average amount of time required per cycle will be within the limits of the overload protection. Some will install a larger run capacitor and post a 4 HP rating on their motors.
    Without actually installing a flywheel on your motor and running a friction load test while monitoring the amperage draw and temperature rise there is no real way of knowing the true power output of your motor. but I suspect that it would be somewhere in the range of 14 to 1500 watts @ 85% efficiency continuous. and 40°c thermally protected.
    All Correct Frank (imho), and the last paragraph is where I would start...find out what you actually have. Somewhere back when on HMT, I wrote a small dissertation on Vacuum motor HP ratings and what you actually get and why the hype. Thing that bothers me about this motor is it doesn't have a data plate...at all (not a good sign to me)! A design like this needs to have all the components matched for the tasks at hand...especially the yoke and oscillation rate. Working forward from the motor to see what capacity sanding it can actually accommodate, by trying to stay in the 85% continuous efficiency ball park using whatever shaft/sheaves and couplings sizes to keep it in the zone.

    You can get an inexpensive digital tach on Amazon.au. This is the one I got back in 2012 and only change the batteries once...keeps on counting just fine.

    PJ
    Last edited by PJs; 09-23-2018 at 01:31 PM. Reason: digital tach
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  11. #18
    Supporting Member Frank S's Avatar
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    Still if the motor should turn out to be a 1500 watt motor that is still a respectable size for an osolating drum sander and if I understand his writing he plans on obtaining the vertical travel via a separate power supply IE a windshield wiper motor this will mean a DC power supply as well. This could easily be accomplished by using a plug and play DC converter 12Vdc output,
    A little research of drum sanders manufactures should give him a good idea of what his sander capacity should be for any given size of motor.
    Many people have already invented and reinvented the wheel just use what they have learned.
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  12. #19
    PJs
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    Agreed, Frank and pretty much what I said...build to what you have. As for the windshield wiper motor, a decent choice but have some concerns about continuous duty and that cantilever yoke design used with it in his provided link to the plans. Something like Doug's (rossbotics) sliding block and cam on his Filing Machine would be easier to fabricate and likely easier to set up than the Yoke system. And, for the electrical a simple speed control with the DC Converter would give it variable oscillation rates which I would think would be a good feature, having only used small shop ones a few times...inexpensive add-on's for single source power.
    ‘‘Always do right. This will gratify some people and astonish the rest.’’
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  13. #20
    Supporting Member jonnydot's Avatar
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    Thanks guy's I have already purchased a tach should be here in a couple more days https://www.ebay.com.au/itm/DT2234C-...53.m2749.l2649


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