DC Permenant Magnet Motor Retorfit on my Knee mill

[PatMarlin]

Most folks here know we live of grid, and use solar power. We have only single phase 110 (a good amount of amps thereof), and I don't like running a noisy generator to power equipment, so I scraped the 3hp 3phase motor that came on my knee mill, and installed a Permanent Magnet Drive DC treadmill motor as a replacement.

The motor is 3hp, way more power than this machine needs, as even a 3/4 hp in DC would power it very well. It did not have the nema flange that would make life much easier to install no, so I had to fabricate a mount to work with the side saddle motor mount.

The DC motor shaft was smaller also, so I machined a reducer bushing, then rough machined a step key with a mill end bit, chucked in my Logan. Worked pretty slick.

Going to fabricate a control switch box, and wire it up tomorrow. Will see how she does. The DC motors a hell for torque, variable speed, and use very low amperage in 110v. Can't wait to make some chips fly with this baby ...! ...:Fire:

[Buckshot]

.................Kewl beans dude :-) YA got to use your lathe too[smilie=w: Yup, you should have pleanty of 'twisting energy'.

..............Buckshot

[PatMarlin]

Did ya see my genuine extra large mug I brought back from Holland with our Dutch code of arms cuz... ?

"Heldhaftig, Vastberaden, Barmhartig", meaning "heroic, determined, merciful".


Motto

During the 1941 February strike in Amsterdam, for the first time in Europe non-Jewish people protested against the prosecution of Jews by the Nazi regime. Queen Wilhelmina of the Netherlands wanted to remember the role of the citizens of Amsterdam during World War II and created a motto consisting of the Dutch words "Heldhaftig, Vastberaden, Barmhartig", meaning "Valiant, Steadfast, Compassionate". On March 29, 1947, Wilhelmina presented the motto as part of the coat of arms of Amsterdam to the city government.

Never will I forget the emotion that overwhelmed us, when eyewitnesses first notified us in London of how the entire population had actually turned against the inhumanity of the cruel tyrant.

-Wilhelmina of the Netherlands

In the coat of arms of Amsterdam, the motto is written on a silver scroll. This scroll is positioned on top of the compartment under the escutcheon.


...

[PatMarlin]

Mounted and wired up the control today, and it works beautifully. Only uses 10 amps@110V. Very smooth, with smooth transition on the variable speed pot.

Surfaced some AL with one pass by hand crank, then I made a pass with the whole cutter and power feed. Mirror smooth with fine cross hatching- shows prism colors. I am very pleased.

Now got to make a box to enclose the control, mount the speed control pot, and on/off SW. Makes some brackets to hold the way cover rubber I cut out, replace felt in the wipers, and fix the one shot lube (hose broke), and I think it will be ready for service.

[PatMarlin]

pics.....

[dominicfortune00]

Pat

Did you ever think of building a rotary phase convertor to run the three phase motor?

Check it out here: www.instructables.com/id/Homemade_Rotary_Phase_Convertor

Tried to make it a link, if it doesn't work, copy and paste.

[JIMinPHX]

This thread shows a control box that I frequently use for applications like this.

http://castboolits.gunloads.com/showthread.php?t=49233&page=2

[PatMarlin]

Thanks for the link Dominic. I had considered all the options, and the permanant mag DC was the way to go for me. I put the machine in backgear and a load and it was pulling about 12 amps 110v. 12 AMPS! That's what cheap vacuumes pull. Pretty hard to beat that measured result. Plus I got the motor free, and the control is a KB- very good company, for $85 off ebay.

My logan is gobbling 20 amps just running, so I will be replacing that old motor- circa 1950. I've got a heavy industrial 1 1/2 hp Baldor, brand new never used, that I'm going to try on the Logan. If that one doesn't work out, I'll go the DC route again.

Good idea on the control box Jim. I've got metal brakes here and a bunch of AL, so I will brake up something to work.

[Willbird]

On the amperage draw, there is no way to get X number of HP without Y amount of draw :-).

What did the motor come from ??(sorry did a reread and saw "treadmill")

From my own personal experience a VFD beats the stuffing out of any rotary phase converter. The only way the rotary phase converter is even in the same realm is if you get the motor for free. I would only ever use one for say a cnc machine that needs 3 full phases to even power on.

Most folks never use the top HP a BP mill comes equipped...the single phase machines only had a 1/2hp motor on them and for most uses you would never feel a need for more HP.



Bill

[PatMarlin]

That motor came from a Treadmill Bill. It's rated at 3hp and over 3000 rpm, but my control is only rated for 1 1/2 hp, which is more than enough for what I need.

Since I generate my own power, I need the most efficient motors I can run that will get the job done. I can see this rig will be well in the efficiency range for my needs and I'm well pleased.

It's not a reversing control though. How often do you need reverse on a Knee Mill? I can always use that control on my lathe, and get a reversing one for the mill.

[JIMinPHX]

On the amperage draw, there is no way to get X number of HP without Y amount of draw :-).


Correct. 746 watts = 1Hp. A motor doesn't create or destroy power, it just converts it from one form to another.

[JIMinPHX]

Since I generate my own power, I need the most efficient motors I can run that will get the job done. I can see this rig will be well in the efficiency range for my needs and I'm well pleased.


PMDC brushless motors are pretty efficient, but so are 3 phase squirrel cage motors. A VFD with proper adjustment will give you equal efficiency & limited start up current on a 3 phase motor. Just because a motor is rated at 3Hp doesn't mean that it needs to pull a full 3Hp worth of current all the time. As load torque is reduced, motor slip is reduced & a 3-phase motor starts to draw less current. Also the VFD can be programmed to limit current. If you run a 3-phase motor on a straight contactor, it will draw 6 x name plate current when starting. That would probably be a big problem for you. A VFD can get rid of all that.

[JIMinPHX]

How often do you need reverse on a Knee Mill?

I do it all the time when I'm power tapping. Tap in...Tap out. Also, when I switch from high range to low range, I need to change the direction of rotation because of how the gearing in my mill head is set up. I thought that most all of them were that way. In the last week, I have used from 200rpm to 14,000rpm, so I really do need both ranges & both directions.

[PatMarlin]

How bout reverse on a lathe?

[Willbird]

How bout reverse on a lathe?

It is handy, and sometimes needed depending on how the back gearing works. A BP for example when in back gear you run the switch in "reverse" to get forward. Also sometimes on a lathe you want to cut on the back side of the work and then you need reverse. You cannot take a heavy cut in reverse with a threaded spindle, but you can whip a chamfer on an ID or such without a problem.

Bill

[leftiye]

My mill goes backwards when in low range, so I need a reversing switch. Lathe - you might want to reverse to do left hand threads. I've seen guys advocate reversing directions to put the load on the saddle into an upward thrust (don't ask me).

[JIMinPHX]

How bout reverse on a lathe?

If I'm single point threading up near the chuck, I sometimes use reverse spindle rotation & bring the upside-down tool in from the back side of the work piece. It keeps me from accidentally crashing into the chuck if I don't get the threading half nuts disengaged fast enough. Other than that, I almost never use reverse on a lathe. Actually, I usually only use the reverse threading trick once or twice a year if that often. That could almost come pretty close to qualifying for almost never too.

[Buckshot]

.............Yup, when you put your mill in low the spindle reverses it's rotation, so you may eventually need it.

http://www.fototime.com/BA6361C20C96D6A/standard.jpg

I like to thread on the backside, spindle running reversed (clockwise). Eliminates the pucker factor as you approch a shoulder or other feature you don't want to run the threading tool into, or on :-). You can also run the spindle much faster which helps to improve the finish of the thread.

Did ya see my genuine extra large mug I brought back from Holland with our Dutch code of arms cuz... ?

I didn't notice it a first, but checked back in the pics and found it!


..............Buckshot

[PatMarlin]

Very cool threading proceedure cousin.

I got to thinkin'... My KB controller is not the reversing model, but what in the world could make that DC motor reverse but switching the polarity on the power input? There's only 2 wires, since its a permanant mag motor there is no field connetion, so a swap of the wires should make it run in reverse shouldn't it? Then I could wire up me a reversing circuit switch. Gotta check that in the morning.

[JIMinPHX]

a swap of the wires should make it run in reverse shouldn't it?

Yep, that's all it takes. A big chunky double pole, double throw switch or relay is all that you need. If you are only going to change the polarity when the motor is stopped, then you don't need an expensive HP-rated motor controller switch. You just need one that is rated for enough amps. Actually, depending on the particular speed controller you have, switching polarity under load may kill the speed box. Some of them will "catch a flying load" & others will fry trying.

[JIMinPHX]

Hey, by the way, where might I find some good info on that off-the-grid power generation equipment? I'm especially interested in solar, since we have so much sun here in Phoenix.

[Flinchrock]

that motor came from a treadmill bill. It's rated at 3hp and over 3000 rpm, but my control is only rated for 1 1/2 hp, which is more than enough for what i need.

Since i generate my own power, i need the most efficient motors i can run that will get the job done. I can see this rig will be well in the efficiency range for my needs and i'm well pleased.

It's not a reversing control though. How often do you need reverse on a knee mill? I can always use that control on my lathe, and get a reversing one for the mill.

tapping!!!

[PatMarlin]

Hey, by the way, where might I find some good info on that off-the-grid power generation equipment? I'm especially interested in solar, since we have so much sun here in Phoenix.


http://www.backwoodssolar.com

Good folks to do business with. Their catalog is a wealth of info as well as their website.

[JIMinPHX]

Thank You Pat.

[Linstrum]

Back about 37 years ago I changed from a 3-phase induction motor to a reversible Boston Gear 3/4 HP shunt-wound DC motor on my U.S. Burk Mill Rite clone of the Bridgport milling machine. I used a Boston Gear variable speed control until about three years ago, but it is a nightmare to repair and I went to a US$160 KB variable speed control when the Boston Gear control smoked itself. I also put the same model Boston Gear DC motor on my 13"x60 Jet lathe. Permanent magnet motors are also darned good for lathes and mills now that the rare earth magnets are available since the modern magnets, like the cobalt-samarium type, are very strong and do not weaken with time or use like the old AlNiCo type.

For both the lathe and mill, I never looked back after converting to DC. I CONSTANTLY use the variable speed and reverse on my lathe and mill, I don't see how I ever got anything done without the variable speed and reverse! I use the variable speed when facing off the end of a large diameter shaft in the lathe in order to keep the surface feet per minute close to about 120 fpm (120 fpm for mild steel, slower or faster for other materials).

I cut metric threads as well as oddball threads a lot, and with the metric thread 120x127 converter jack shaft gears the lathe MUST be reversed to back up the lathe carriage for each pass of the thread cutting tool bit, or else it loses thread timing if the carriage feed half nut is disengaged and then the carriage moved or headstock shaft rotated. I leave the half nut engaged until done cutting the thread and reverse the lathe motor to back the carriage up for each new pass. With that method I can cut metric threads almost as quickly as inch threads. The one particular oddball thread I cut a lot is the 17 turns per inch 1/2" British pipe thread, which I accomplish by mixing and matching the various gears that came in the lathe to create a 16.97 turns per inch thread that works just fine. I used to use a metric 1.5 mm thread for Brit pipe, which comes out to 16.933 threads per inch, which also works fine for short thread engagement of 17 tpi threads.

The gist of my ramble is that variable speed and reverse accomplished using a DC motor makes life in my machine shop so much easier.

The only thing you have to watch out for with reversing a DC motor equipped with an electronically controlled variable speed circuit is the power to the variable speed absolutely has to be turned off before operating the reversing switch, or else the control unit smokes itself. In the "heat of battle" or when really tired, it is REAL EASY to accidentally hit the reversing switch with the power on. When I did it, it cost me $160 for a new variable speed unit. Put a guard cage over your reversing switch!

There is another way of running a DC motor so it is variable speed. A special borax solution liquid diode rectifier can be built. It is extremely simple to build, it has aluminum plates submerged in a non-conductive plastic tank of water and borax solution for each of the four required diodes and the motor speed is controlled by lowering or raising the aluminum plates in and out of the borax solution to change current density. The very first industrial diodes were the aluminum plates in water-20 Mule Team borax type.

Have fun!


rl533