Mods to BP drum switch for VFD (adding speed pot to existing?)

[AdamC]

Has anyone figured a way to incorporate a speed potentiometer into an existing Bridgeport drum switch enclosure? I'd like to add a pot, maybe to the LHS. My enclosure is pretty tight. I could use a larger box.

What I'm thinking is, I'd like to keep the drum switch roughly where it is, and have a pot within finger distance, such that I can turn on the mill, leave my hand up there and adjust the speed.

Tried searching the forums and google, but haven't found anything.

BTW- I've read the many suggestions about push buttons and disagree with our UK brethren (aside from e-stops). The nice thing about the drum switch is that it's very easy to find and change without looking at it. I really don't want fwd/reverse and stop push buttons. And I don't want a big switch box.

Is there such as thing as a 3 position drum switch (F-N-R) that is also a pot? I'd need a click for N that would be definable motor off. That would be ideal.

(Obviously planning to power the mill with a VFD)

 

[Greg Menke]

I found the drum switch so packed with wiring that I punted to putting the knob down on the vfd's box. I leave the drum switch set forward and control direction and start/stop via the vfd. Though its not on the drum switch, it does make locating the knob down at chest level straightforward. OTOH my vfd is located around back which is a little tedious, but still efficient. I have a shaper head wired to it as well, so having the knob not associated with the mill head itself is helpful.

 

[memphisjed]

You just need a three way switch. That will free up 90% of the box from wires and drum.
You switch the drive logic not the motor.

https://www.automationdirect.com/adc/shopping/catalog/pushbuttons_-z-_switches_-z-_indicators/selector_switches/af16pr-3c2b

You have no load (sub amp) and 10 volts going to the switch, wires can be thin. You can run a cat5 cable to vfd to carry all the wiring to switch box.

 

[604Pook]

You just need a three way switch. That will free up 90% of the box from wires and drum.
You switch the drive logic not the motor.

https://www.automationdirect.com/adc/shopping/catalog/pushbuttons_-z-_switches_-z-_indicators/selector_switches/af16pr-3c2b

You have no load (sub amp) and 10 volts going to the switch, wires can be thin. You can run a cat5 cable to vfd to carry all the wiring to switch box.

this and If wanted and if you like the clicking of the old drum switch, you could use the forward reverse switch and just wire it up to the stop forward and reverse duties, by using the right combo of contacts to close the ccts. you would likely need to run the VFD in jog mode since the drum switch isn't momentary. The pot, would need to be its own thing for the speed control.

Found this on youtube.

 

[AdamC]

Thanks guys. Yes, I want the drum switch, but I’m okay with replacing it with a modern version, if that’s my only option. Just hope it will have a good metallic feel.

I’d like the speed control pot proximate to the drum switch, not somewhere else. Looking for one handed, eyes on the spindle operation. I’ve seen a couple large drum switches online.

just wondering if anyone else has solved this issue, or tried replacement drum switches?

 

[johansen]

I bought a used fuji vfd recently and it has the ability to reverse without a switch 0 to + or - 10 volts.

I think that you could find a lever action potentiometer to replace the drum switch to get what you want. Or add it to the drum switch.

 

[AdamC]

Like to see the details on that. That would be of interest to many I would think. I thought this was a dead end:

Help with remote speed and direction control for VFD

I could use some help from some of you electronics wizards on here. I'm setting up my 1909 Hendey Engine lathe with a VFD, not for voltage or phase change, but for speed control. The lathe was a very early "electrically driven" machine tool that probably had a DC motor that was controlled by a...

www.practicalmachinist.com

Essentially, as I understand your post and the thread above, we could have a single pot knob that controls both speed and direction and includes some sort of detent for OFF. That would be ideal, but I didn’t think most VFDs would accommodate.

 

[AlfaGTA]

Not really an answer to your exact question , but I took a slightly different tact.
I fitted a VFD to our “Kondia” power mill.
Used the original drum switch to switch the direction on the VFD
Really only takes two of the three contact sets.
Used the third contact set to switch 110v that I used to power a digital tachometer.
Made an enclosure to hose the tach display and that is where I put the “pot”
for the VFD speed control.
Entire setup mounted just above the drum switch so very handy and a real tach gave real time display of the actual spindle RPM.
Cheers Ross

 

[AdamC]

Not really an answer to your exact question , but I took a slightly different tact.
I fitted a VFD to our “Kondia” power mill.
Used the original drum switch to switch the direction on the VFD
Really only takes two of the three contact sets.
Used the third contact set to switch 110v that I used to power a digital tachometer.
Made an enclosure to hose the tach display and that is where I put the “pot”
for the VFD speed control.
Entire setup mounted just above the drum switch so very handy and a real tach gave real time display of the actual spindle RPM.
Cheers Ross

Picture?

 

[AlfaGTA]

Sorry, looked at my photos and don't have any of the finished install, just some of the bits to do the tach.
Problem is that machine has been sold, will ask the current owner if he can snap some shots..
Cheers Ross

 

[jim rozen]

Ditch the drum switch and use a simple center-off toggle switch. Goes in the same small box as the speed control pot. Honestly no need for a tach IMO. Simple is good.

 

[AlfaGTA]

Don’t agree. Rather have a full sized drum switch , one you can get your hands on Mmachine. -esk.
As to the tach ,not important unless you are working with surface speed for a given material, suppose guessing is good enough for some.
Cheers Ross

 

[Greg Menke]

A center-off fwd/reverse knob is perhaps less desirable; for instance if a job involves a series of ops all that the same rpm then you're stuck putting a mark on the panel or having a rpm display- all more cumbersome than hitting a fwd/start button, or flipping a drum/toggle switch. Generally I adjust the rpm for "about right" and keep an eye on the chip color when its important. I've only rarely needed reverse motor rotation, mostly only needed it when in backgear, so integrating it into a single fancy control wouldn't help much. It also makes stopping more cumbersome; way easier to avoid mistakes when theres a stop button or drum switch- even a center-off toggle switch is prone to flipped too far over the other way.

I ended up with a 2nd drum switch mounted on the Bridgeport, wired to the vfd control inputs. The nichols mill has an integrated OEM start/stop button, so I wired that to the vfd also and since the small wires left a lot of room in the box I mounted the speed pot in it, and put a fwd/rev toggle back on the vfd enclosure.

 

[jim rozen]

Drum switch is fine but he'll need to graft on some other box for the speed control pot. Just seems a bother to me.

 

[Greg Menke]

Definitely a bit of bother to set it up.. but way better than fishing around with buttons and tiny knobs on the vfd panel. I suppose it comes down to how fussy the OP wants to be. Model railroad guys make me tired and a bit nervous with the level of detail they go to...

 

[jim rozen]

Not advocating using the vfd panel. Just a single box with switch and pot. All kinds of meaty switches out there. Everyone has a fetish for old school drum switches but it's just a switch. Itty bitty teeny weenie toggle that goes in a 1/4 inch hole is fine - as far as the vfd is concerned.

 

[jbacc]

Ditch the drum switch and use a simple center-off toggle switch. Goes in the same small box as the speed control pot. Honestly no need for a tach IMO. Simple is good.

That's what I did with my BP Mill. Toggle switch and a speed control pot.

 

[gustafson]

Rotary wafer switch
You buy the frame and the contact wafers separately
Nice heavy detent

I don't think I would want the speed in the same spot, watching a tap while reversing and bumping the knob could be 'bad'

 

[Brandenberger]

22mm 3 way switch replacing the drum switch and a 22mm pot controlling VFD speed…