Speed Control..

E

electric

Joined
Mar 7, 2010
Messages
50
Hi Guys,

Just wanted you people that use paper wheels to know if you already know that H.P. sells a router speed control that works with their buffer that works Great.

I just sent a friend from my house grinning from ear to ear after sharpening his hunting knife. With the speed control you have a foll range of speed from dead stop to full tilt. Takes away the worry about burning the blade.

Thanks Guys,
Electric
 
thats a good tip for guys with high speed buffers that want to slow it down. the only way to burn a blade is user error of course but the speed control lets you slow the whole process down when using the grit wheel. when using the slotted wheel on a buffer with a built in variable speed, max it out if you want.
 
You may want to do a bit of research... using this type of control on a motor not designed for it can cause it to overheat and/or burn out.

cbw
 
image_1025.jpg


Item # 43060 Manufacturer: Drill Master

Assuming this is the one referred to by the OP, it's designed for 'universal AC/DC brush-type motors'. If I'm not mistaken, most bench buffers/grinders are AC only (brushLESS)?
 
Motor cooling is designed into the motor based on its speed. Obviously variable speed motors such as drills, Dremels and Foredoms are designed to cool adequately throughout their speed ranges. There are some motors, mostly 3-phase, that are designed to operate through wide speed ranges. I'm electrically challenged, so I don't know how to tell exactly. I have a 3-phase motor designed to operate through a VFD that I intend to use as a variable speed power source for sharpening/grinding. It would be easier and cheaper to pick a motor and learn to use the speed it has. One can always use an arbor and multi-diameter sheaves.
 
richard j said:
does anyone make a speed control that will work on a brushless motor?
Click to expand...

This thread got me to reading a little bit about AC motors vs. DC. The gist of what I've read so far suggests that the speed of AC motors is directly dependant on the line frequency (60 Hz in the U.S.A.). Speed can be varied by varying the FREQUENCY, but this is more complicated (and more expensive). And there's a low limit to how slow you can make 'em run, because they will overheat. I know Delta makes a variable speed (1725 - 3450 rpm or so) grinder/buffer based upon an AC motor, but it's relatively expensive. I've seen it at Lowe's.

DC motors (or so-called 'universal AC/DC brush-type' motors) vary their speed in direct proportion to VOLTAGE. They run on DC, so it's easier to vary the voltage up/down (and therefore less expensive). These are the type of motors generally found on variable speed portable power tools (drills, circular/jig saws, routers, etc.)

Here's one of the links I looked at regarding the different types of motors:

http://www.oddparts.com/acsi/motortut.htm
 
Bernoulli said:
I have a 3-phase motor designed to operate through a VFD that I intend to use as a variable speed power source
Click to expand...

This is what I alluded to in my reply to richard j. The VFD (variable frequency drive) is used to vary the line frequency to the AC motor, and therefore vary the speed.
 
Does anybody know exactly what the pictured controller does?

I just measured it throughout the L/M/H range and the voltage remained at 119VAC.

It does not vary the frequency.
 
kelbro said:
Does anybody know exactly what the pictured controller does?

I just measured it throughout the L/M/H range and the voltage remained at 119VAC.

It does not vary the frequency.
Click to expand...

Just to be sure, you measured it with the switch in the 'VAR' position (as pictured)? If it's in the 'FULL' position, the dial for speed control will have no effect.

Barring the switch setting, you might need an oscilloscope to actually see what's happening with the output voltage. Most voltmeters, when 'measuring' AC, will only respond fast enough to show peak (or near-peak) AC voltage values.

Based on what I've been reading about these variable speed (voltage) controllers, they work by using a circuit which intermittently turns ON/OFF the AC, as opposed to continuously varying the voltage UP/DOWN through the full range of the AC waveform. In essence, the AC voltage will be FULL ON for a certain length of time, and FULL OFF for the remainder of the cycle, all depending on the speed-dial setting. The net effect is a reduction in the 'average' voltage (over time) delivered to the motor. This would also explain why there's usually a significant loss of motor torque as the speed is varied, because the motor is essentially free-spinning (no driving current) during the period of time the AC is switched off.

That's my two cents... ;)
 
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Obsessed with Edges said:
Here's one of the links I looked at regarding the different types of motors:
http://www.oddparts.com/acsi/motortut.htm
Click to expand...

Great link! I've been trying to figure out how to slow down a Harbor Freight 1x30 for awhile - don't think it's going to happen on the cheap.

Too bad too, the machines are inexpensive and if they could be controlled they'd be great for knives. 3450 RPM is just too fast for fine work, maybe lawn mower blades.

I did try the router controller on the HF - no good.

Thanks again for the link, it's a great resource for the electronically challenged.

Keith
 
handamerican said:
Thanks again for the link, it's a great resource for the electronically challenged.

Keith
Click to expand...

:thumbsup:

I'm glad you found it informative. There are lots of links out there with some VERY technical info on how these things work, but this particular one seems to do a better job of explaining it in language that most of us can deal with. Most of my work experience is in the electronics field (military electronics tech & semiconductor mfg tech for combined 20+ yrs.), and I still feel the need to seek out the 'simpler' explanations for a lot of this stuff, more often than not. :D

Dave
 
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The simplest method is to reduce the size of the drive wheel.
 
Some of these discussions are funny . I've been using a variable speed belt grinder for 12 yrs. for knife making with no problems . I inter-phased a programable brain/ speed controler behind my motor switch, simple but not cheap . They were nearly 200$ back then, I'm sure they've gone up . A Reliance Electric SP-200 model AC drive . Then you wire it to come out of this junction box into another switch that will turn the motor on and off . But the Reliance unit allows one to program an endless amount of settings or a range of rpm's and does not decrease power (output) . Mine is programed down to 400 rpm and up to 3200 rpm and it does not heat up my 1 horse motor . This should cover any range I'm working . It allows me to do things a Baldor doesn't . It helps living in a mining district as these supply houses cater to companies who need this specialized type of equipment . DM
 
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I just got a VFD from Southland Electrical. I am way highly impressed with them. No joke, fabulous products and especially great service. They rock.

I got a rebuilt Allen Bradly 5hp VFD for my 3hp motor (yes, I know this is slightly overboard for a 2x72) for just $325. It carries the same warranty as brand new, and they will totally fix anything that can go wrong with it. Going bigger is better because you don't lose as much torque at super slow speed.

Near as I can tell, cheap little VFDs are money well wasted.
 
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