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Thread: Fan Modification.
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15th December 2013, 10:37 AM #16
I'm inclined to agree with leaving the fan alone. I've been told that motor failure on these machines and also the small lathes that use them is a common failure. Also that the manufacturers are changing the design to incorporate an induction motor with a VFD.
Incedentally the motor design is a ripped off copy of a "Philips" washing machine motor.Best Regards:
BaronJ.
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15th December 2013 10:37 AM # ADSGoogle Adsense Advertisement
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15th December 2013, 10:48 AM #17
At the time I was using a 3/8" slot drill to square up a small 2"x3"x0.25" alloy plate. Running in low gear at about 1000rpm. So no great load on the motor.
In actual fact the original motor failed because two of the comutator segments had shorted together, more acurately two windings ! I did hear the motor noise suddenly change at the time but didn't realise what it was until I saw the smoke.Best Regards:
BaronJ.
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15th December 2013, 11:01 AM #18
Rob (Nearnexus) and i put 180v DC treadmill motors on our lathes. We both ended up burning them out as we just could not keep them cool. I got mine hot enough to start to melt the lacquer on the windings and then of course it shorted. What really gets them hot is when they brake, does your mill have a brake on it? We both had computer fans pulling air through the motors but it was not enough.
https://www.woodworkforums.com/f65/ma...ersion-159263/ It's a long thread but may help you out....
Cheers,
Ewan1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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15th December 2013, 11:26 AM #19.
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I don't know where you get the idea that slowing down air flow will carry away more heat. Rate of heat transfer between materials depends on the nature of the material and the temperature difference between the coolant and the object being cooled. As soon as the coolant heats up it's ability to draw heat away from the object being cooled is rapidly reduced.
If it were me I would have just made ~20 mm wide full length louvered slots on 3 sides near the top. Now that you have put holes in the top I would cut out all bar about 10 mm near the sides of the whole top and cover the hole with a sheet metal cover ( to stop gunk falling in) stood off about 20 mm from the top.
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15th December 2013, 02:40 PM #20GOLD MEMBER
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as bobl says...to remove more heat you need more airflow
Axial fans do not I repeat DO NOT like restriction. best to use a backward curve centrifugal fan if restrictions are present..and even then air flow volume is still dependent on static pressure...the higher the static the less volume. ...air is like water ..it likes the easiest path
If you look at most motors incorporating a fan on the back of the motor the fan is a paddle type which also has the ability to handle higher static pressures than axial.
paddle fans can also deliver more air for comparative size of axial diameter
and that was a big part of your problem...you let the smoke out
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16th December 2013, 10:55 AM #21
Hi Ewan,
Very useful information about the treadmill motors. I've been looking out for one or two of those without any luck. I'm not sure about the brake. It does stop very rapidly when the stop button or the shield switch is actuated. Though I did discover that the spindle has a fair amount of drag which reduces when it gets warm.
Thanks for the link. I'll peruse that with interest.Best Regards:
BaronJ.
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16th December 2013, 11:13 AM #22
Thankyou for that info. It seemed somehow right to allow the air to absorb some heat as it flowed over the hotter surface. I can see where as the temperature difference reduces the cooling effect becomes less. I like the idea of a big hole and a flat cover over the top. That would give roughly the same apature as the fan.
Yes I did ! The fan project I hope will reduce the risk of doing it again.
Thanks guys. The wealth of knowlege and experience here is very much apreciated.Best Regards:
BaronJ.
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17th December 2013, 08:07 AM #23GOLD MEMBER
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BaronJ
how big is the diameter of that hole
I may have a fan that will certainly deliver much much more air that that peeezly little axial
One of the ones I am thinking of needs a hole diameter of around 90mm or 125mm...but they are 240v
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17th December 2013, 08:38 AM #24
Hi Eskimo,
I'm not sure 80mm I think. Its a standard computer PSU fan salvaged from a scrap one. The chrome finger guards came from a scrap HP server that had a dual redundant power supply. I have several fans of varying sizes and voltages, some 250mm 240V ones out of instrument cabinets. They have alloy blades that will take a finger right off if you don't take care. I'm tempted to scrap them and salvage the ball races.
The fan I used has a high airflow, much higher than is normally found in fans of this size, which is why I picked it from the ones I have.Best Regards:
BaronJ.
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