How to slow down RPM of miter saw?

I'm probably going to try the diode method first. There are some ultracheap 1000 V 10 amp diodes available. I might put some of them in parallel. I doubt that has the same problem. And then it can be used for any other appropriate brushed universal motor device.

Reply to
John Doe
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John Doe prodded the keyboard

I suspect that it will not achive the desired effect ! Recall that a universal motor will happily run on ac or dc, the motor brush gear simply chops up a dc supply to create an alternating field.

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Best Regards: 
                       Baron.
Reply to
Baron

Baron wrote in news:m5ik9q$rf5$ snipped-for-privacy@dont-email.me:

What effect do you suspect it will have?!

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> Recall that a universal motor will happily run on ac or dc, the motor 
> brush gear simply chops up a dc supply to create an alternating field.  
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Reply to
John Doe

John Doe prodded the keyboard

Never having actually placed a diode in series with a universal motor, not a lot. I belive that the motor current will increase to try and compensate for the drop in speed due to the load. The motor will try to maintain its speed.

It is however an interesting experiment and I would be interested in your findings.

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Best Regards: 
                       Baron.
Reply to
Baron

I used to repair such and I have never seen one that directly drove the blade, they all had reduction gears.

Reply to
Rheilly Phoull

Not that it matters, but the argument is lost... The original point was that the motor is spinning too fast to be an induction motor. Therefore, the 5500 RPM specification either applies to the motor or the motor is spinning faster than that. Talking about reduction gears doesn't help refute the fact that it's a brushed universal motor.

But of course you may argue about whatever pointless thing you wish to argue about...

Reply to
John Doe

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Reply to
Tom Biasi

** Errr, that rating is for one half cycle at 50/60 Hz.

The time it takes to put a of charge in a filter electro.

IOW way shorter than a motor's start up surge.

.... Phil

Reply to
Phil Allison

It would be interesting to how a series motor can be dynamically braked in a hand tool?

Jamie

Reply to
Maynard A. Philbrook Jr.

Many of those images are clearly gear driven saws.

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umop apisdn
Reply to
Jasen Betts

I can't help that. Many are not. The statement was "I have never seen one that directly drove the blade"

Reply to
Tom Biasi

Some do some don't. How long ago was this?

I have an old Skill Saw with a pair of gears, and a fairly old Sears and newer B&D that are direct drive, and depth of cut is nothing to brag about.

Reply to
default

I know. I just looked up a 20 amp DO4 case diode and current surge is

400 amps. I couldn't find any definitive start-up specs for AC/DC motors just some comments like "double" or "several times" the rated current. When they say the motor is a 14 amp motor - they do mean it might pull 14 amps when cutting.

My bench table saw has a universal motor in it and is rated at 15 amps. I've popped the 10 amp breaker on the power strip a half dozen times in 5+ years, and then cutting things like wet 4X4 wood with a dull blade. The power strip probably has a cheap thermal breaker on it, the 20 amp house circuit has never tripped.

I can rip 8 foot 2X4's without tripping a breaker.

I can't prove it, but would bet serious money it would work with a 20 amp diode.

Reply to
default

John Doe wrote in news:m5d282$si5$1@dont- email.me:

I missed a part of the discussion due to the limitations of my news servers so I may tell no news. Nevertheless:

This type of machines usually have universal motors. They can be slowed down by ordinary dimmer like controllers. This however is not very effective as lowering the voltage will make the speed very dependend of the load. The best way to control this type of motors is using DC and PWM.

In my experience Al will not be cut very effective by an abrassive disk. The soft Al will smooth the disk by filling the spaces in it. I got the best results using a saw blade with hardened steel teeth as for hardwood,

petrus bitbyter

Reply to
petrus bitbyter

An induction motor can be dynamically braked by connecting DC to the windings. This can be done with a capacitor and a diode. I think that if the brushes are shorted and DC is connected to the windings this would work like an induction motor. See this link:

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It is from 1970. Eric

Reply to
etpm

Tom Biasi prodded the keyboard

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Have a look at the "SawTech" Italian machines. Mine is a direct drive

2Hp single phase induction motor running at 2800 rpm with a 10" blade. There is no gearbox !
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Best Regards: 
                       Baron.
Reply to
Baron

None of my saws have a gear box.

Reply to
Tom Biasi

Sure, you have 50Hz with a 2 pole (Tree Rat) cage motor and ~6% slip.

Jamie

Reply to
Maynard A. Philbrook Jr.

The key is DC current... where does one get that from a device that only has an off/on switch to a series motor with no magnets for self generation? You can dynamically brake a series motor but it's not as simple as just connecting the A1 and A2 together.

Jamie

Jamie

Reply to
Maynard A. Philbrook Jr.

Maynard A. Philbrook Jr. prodded the keyboard

Yes ! That is exactly what It is. :-)

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Best Regards: 
                       Baron.
Reply to
Baron

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