Variable speed pedal control?

[71Scamper]

I'm looking for a heavy duty variable speed pedal for my electric rotary tool. I'm almost done with porting my heads and my pedal crapped out. I'm looking for something that can handle 4 amps continuously and is not the stacked pill type. My old pedal had the carbon pills and they just crumbled from using it to do one and a half heads. Any recommendations?

 

[67 Power Wagon]

I myself use an old Singer Sowing machine foot pedal and its been going strong over 10 years (now) and it runs 3 different machines and with my wife, and I in the shop at the same time, it runs one or both at different times, and has yet to give me any back talk......

Sadly, I have NEVER had it apart, so I have no clue whats in side "the works" if its not broke, don't try to fix it...... if ya do, use a BIG hammer!

 

[71Scamper]

well I couldn't find a pedal that could handle a minimum of 5 amps online, so I just bought a rheostat controller made for ceiling fans. Its rated at 15 amps so It should last a while!

 

[67 Power Wagon]

I got to ask, what are you running with this Rheostat? I am not certain 5 AMPS draw on that is a good thing, and with a ceiling fan it be OK, BUT, these type things normally aren't pulling that sort of amperage, till its running wide open......

Sure, a household wall Rheostat rated at 15 AMPs will handle 5 AMPs I'm just trying to figure out what your running variable speed that draws 5 AMPs....?

 

[67Dart273]

As long as this is a conventional brush motor, a "lamp dimmer" (rated for enough amps / wattage) will work.

You can MAKE a foot pedal out of one with a simple bellcrank mechanism. You might not get complete "full rotation" but you might not need it, either If you look around you might find one with a sliding (linear) control, or even tear into it and replace the pot with a linear pot

 

[71Scamper]

I got to ask, what are you running with this Rheostat? I am not certain 5 AMPS draw on that is a good thing, and with a ceiling fan it be OK, BUT, these type things normally aren't pulling that sort of amperage, till its running wide open......

Sure, a household wall Rheostat rated at 15 AMPs will handle 5 AMPs I'm just trying to figure out what your running variable speed that draws 5 AMPs....?

I'm using a rotary grinder to do port and polishing work. I finished one head, started on the next, got to the second port and the pedal gave out. It had the stack of carbon pills and they were all crumbled. It was a Chinese made item. It was suppose to be rated for 6 amps, but it couldn't handle it.

As long as this is a conventional brush motor, a "lamp dimmer" (rated for enough amps / wattage) will work.

You can MAKE a foot pedal out of one with a simple bellcrank mechanism. You might not get complete "full rotation" but you might not need it, either If you look around you might find one with a sliding (linear) control, or even tear into it and replace the pot with a linear pot

It is a brush type motor

 

[67 Power Wagon]

I'm using a rotary grinder to do port and polishing work. I finished one head, started on the next, got to the second port and the pedal gave out. It had the stack of carbon pills and they were all crumbled. It was a Chinese made item. It was suppose to be rated for 6 amps, but it couldn't handle it.

Then I'd take and clean up the mess with the carbon pills and replace them with graphite ones.....Heres the reason why I say that....

I used to work at a place that made logging equipment, and ALL of their forklifts, were electric and had pretty good size electric motors on them BUT the service guy would come in, and replace the old worn brushes, and then get to cleaning up the whole works till one day on lunch break I brought in some graphite type brush materials, and was turning it on there lathe, and then the one forklift gave out in the stock room area, and I had enough of the graphite and just for S&G's I went turned it to fit the lift motors, and it was 6 years later, the service guy had bitched that they never need much more then a simple cleaning!

To this day, now some 8 years later, I see him AND my old Foreman, and the foreman told me, hes like I have no idea where you came up with that idea on the lift for the brushes but they're still going strong.....I'm just glad to know that at one job I had appreciated something right out of left field! Heres where I got it from:

See, on the side, I have a hobby repair shop, I used to repair and somewhat manufacture parts for old Lionel trains, as a hobby for many years till I figured it was paying me good money to start up a business! But anyway, I had a guy once tell me his locomotive wasn't strong enough.....to pull his however many cars coupled to it.... I did some reading up on it and took what he told me as a testimonial to it, and read that if you replace the brushes (factory ones normally are made of Carbon), with Graphite brushes you'll easily gain 2/3rds MORE power.. so I thought, its worth a try, and here at work one time, my home lathe needed a part to keep it running and didn't come in on time so at lunch break I took and did it at work with permission to....WELL that was when I thought they allow me to do what I want, or need to on lunch break and even some times after hours so....I'll do a favor and get the forklift back on work hours time clock, by turning these to fit its motor....

Worth a try on your rig. Whats the worst that happens? Your still out of a foot pedal? OR you gain one to beat the **** out of! And it just won't quit!

 

[71Scamper]

67PW thats awesome. Unfortunately I already sent the old pedal back to where I bought it from.

Food for thought: The stack of carbon pills offers up X amount of resistance. The harder they are pressed together the resistance value goes down and current is allowed to flow more freely. If i replaced them with graphite ones that will flow more current (less resistance) then I would theoretically be defeating the purpose of the carbon pills. It's a great idea, but maybe not in this application. I will definitely keep the graphite in mind for motor brushes though!

 

[KitCarlson]

I assume the rotary tool has a universal motor? That is a series field brush motor, like is used on a electric drills, vacuum cleaner and leaf blowers, powered by AC. There are triac, solid state speed phase based controls, that work in a similar fashion to light dimmers. Light dimmers are often rated at 600W and are designed for incandescent loads, so will likely fail easily. There are controls however that are designed for universal motors. Electric drill with trigger speed control is an example.

Another robust way is a PWM DC or universal motor speed control, it uses a bridge rectifier, and capacitor to generate a DC supply from AC, then controls speed by a variable duty-cycle using a MOSFET or IGBT. It works well because full voltage is delivered, but for short periods of time at low speed. Speed increases with increase of duty cycle. The full voltage provides excellent torque at low RPM, much better than the carbon pile, or triac phase controls.

 

[67 Power Wagon]

67PW thats awesome. Unfortunately I already sent the old pedal back to where I bought it from.

Food for thought: The stack of carbon pills offers up X amount of resistance. The harder they are pressed together the resistance value goes down and current is allowed to flow more freely. If i replaced them with graphite ones that will flow more current (less resistance) then I would theoretically be defeating the purpose of the carbon pills. It's a great idea, but maybe not in this application. I will definitely keep the graphite in mind for motor brushes though!

Not sure your needing resistance, it sounds as tho your looking for steady use....continuous use, this saying the carbon "loose packed" carbon brushes are the failing reason of the old pedal. The hard pack of the Graphite brush will last a bunch longer, maybe not increase any power rating but will last a bunch longer then the factory ones, kind of like a wrench made from sheet metal like OLD ones once was, todays new drop forged steel, casted ones.....See?

As really all those carbon pill brushes did was "wipe" across a series of wire windings......As pressure was increased or decreased.....

 

[71Scamper]

As really all those carbon pill brushes did was "wipe" across a series of wire windings......As pressure was increased or decreased.....

These didn't move at all. as you pressed down on the pedal there was a spring on the inside that would just push the contact harder against this stack of pills. On the other end was the wire going to the motor. I'm assuming that the harder they are pressed together, less resistance would be had, allowing more current flow.

Am i not understanding it right?

Anyways, here's what I purchased:

[ame]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=151323300284[/ame]

Any good?

 

[67Dart273]

Yes I believe one or both of you is confusing different types of controls

A rheostat foot control uses a coiled length of resistance wire with a mechanical moving contact

A conventional rheostat. Imagine this converted into a foot controlled configuration



The second type is more correctly called a "carbon pile" and is exactly what the name implies---a "pile" of carbon. A stack of carbon discs---which are a poor conductor compared to wire---are stacked up with a control device which can "pack" them together more tightly and then cause more current to flow through them

These battery testers is where you see a huge carbon pile



Here's an old Kenmore sewing machine carbon pile control

http://softsolder.com/2009/03/10/old-kenmore-sewing-machine-foot-control-repair/



This is one type of rheostat design



Frankly, if you have a carbon / graphite type, you might be able to lightly sand the faces of the discs and get more use out of them

The fact that carbon pile resistors are still in use, either doesn't say much about the progress of man, or it says that the "early guys" of radio got it pretty close the first time, LOL

These were invented early on, when electronics was not a word and "it" was just called "radio," "Hertz" was in the history books and you spoke of "kilocycles" and "megacycles" and "capacitors" were called "condensers." "Pico" as in "picofarads" had not come into use, it was "micro micro farads" There WERE no transistors or any other "solid state" device not even a diode, unless you want to count a "crystal radio"

 

[71Scamper]

Yes I believe one or both of you is confusing different types of controls

A rheostat foot control uses a coiled length of resistance wire with a mechanical moving contact

A conventional rheostat. Imagine this converted into a foot controlled configuration



The second type is more correctly called a "carbon pile" and is exactly what the name implies---a "pile" of carbon. A stack of carbon discs---which are a poor conductor compared to wire---are stacked up with a control device which can "pack" them together more tightly and then cause more current to flow through them

These battery testers is where you see a huge carbon pile



Here's an old Kenmore sewing machine carbon pile control

http://softsolder.com/2009/03/10/old-kenmore-sewing-machine-foot-control-repair/



This is one type of rheostat design



Frankly, if you have a carbon / graphite type, you might be able to lightly sand the faces of the discs and get more use out of them

The fact that carbon pile resistors are still in use, either doesn't say much about the progress of man, or it says that the "early guys" of radio got it pretty close the first time, LOL

These were invented early on, when electronics was not a word and "it" was just called "radio," "Hertz" was in the history books and you spoke of "kilocycles" and "megacycles" and "capacitors" were called "condensers." "Pico" as in "picofarads" had not come into use, it was "micro micro farads" There WERE no transistors or any other "solid state" device not even a diode, unless you want to count a "crystal radio"

Yes I thought I was explaining it right! That picture of all the little discs is what I originally had but they crumbled and fell apart. I would much rather a rheostat design but I was having a hard time finding one in a pedal configuration. I'm in a rush to finish my heads so they can go to my machinist for new seats and guides, so I just ended up buying a regular hand controller. It is suppose to be a rheostat design.

 

[71Scamper]

So I got the new speed controller yesterday. It is not bad at all. It barely got warm on the slowest speed with ten minutes of continual use. The only thing I would change is dropping the slowest speed slower just a bit further. But, all in all, it's not bad.

Oh ya, kinda funny that the one I got is actually manufactured by Harbor Freight. So needless to say, I'm expecting it to fail prematurely.

 

[67Dart273]

Can you post a part no? If this actually IS a resistive type controller as opposed to an SCR controller like a lamp dimmer, you could actually ADD resistance in series with the circuit to slow it down more. You might be able to use one or more lamp bulbs, example.


If you bought this thing:

http://www.harborfreight.com/router-speed-control-43060.html

Then it is NOT a resistive control, it is in fact "a lamp dimmer in a box" IE an SCR or other solid state type device.......Nothing wrong with that, but I don't know how you'd reduce it further.

 

[Jimacuda]

Can you post a part no? If this actually IS a resistive type controller as opposed to an SCR controller like a lamp dimmer, you could actually ADD resistance in series with the circuit to slow it down more. You might be able to use one or more lamp bulbs, example.


If you bought this thing:

http://www.harborfreight.com/router-speed-control-43060.html

Then it is NOT a resistive control, it is in fact "a lamp dimmer in a box" IE an SCR or other solid state type device.......Nothing wrong with that, but I don't know how you'd reduce it further.

I have that same one and it works very well, no issues. Just finished porting a set of J's using it and the HF long shaft die grinder which also worked great. Burrs from McMasterCarr. :cheers:

 

[71Scamper]

Can you post a part no? If this actually IS a resistive type controller as opposed to an SCR controller like a lamp dimmer, you could actually ADD resistance in series with the circuit to slow it down more. You might be able to use one or more lamp bulbs, example.


If you bought this thing:

http://www.harborfreight.com/router-speed-control-43060.html

Then it is NOT a resistive control, it is in fact "a lamp dimmer in a box" IE an SCR or other solid state type device.......Nothing wrong with that, but I don't know how you'd reduce it further.

That's the one!

I have that same one and it works very well, no issues. Just finished porting a set of J's using it and the HF long shaft die grinder which also worked great. Burrs from McMasterCarr. :cheers:

I have the same setup. Your using the orange grinder right? So far it has done well porting the one head and part of the second. I'm heading to Canada this next week. I'll get back to them when I return. Then off to the machine shop for seats and guides.

 

[Jimacuda]

Mine is the red one.