View Full Version : bridgeport steppers

11-19-2004, 01:04 AM
I got an old bridgeport boss machine (I think) I know its got the 4J head on it, when I found it everything was stripped except the steppers. I have been able to find more info on rocket science then I have these steppers. Inside the motor cap I find it has p/n 025804. Some guys tell me to run geckos and the motors require 56V at 6amp. Other guys swear they need 100V 12amp. I really need to know before I spend a lot of money on something I cant use with my motors. I know they are on a 2:1 belt reduction if thats of any help.


11-19-2004, 07:48 AM
I didn't have much luck with geckos on them. I know why now talking to others.

THE weight of the table on my bridgeport cnc. Decelleration close to voltage tolerance causes pump up/heat that killed my geckos. Most the losses occurred while running my joystick w.little ramp up.down. Rapid stopping of motors in motion actually charge the capacitor instead of discharging it. Degen. Add this to the heat and something is going to die.

I am running Larken drives Cobra 16's from Canada.
If you are running a system with less inertia it might run just as well on geckos. Mite. They will do as designed. They are a lot more economical in power consumption than any other drive I have played with, ie they shut back to idle current faster and save lots of power going through the bridges.

www.geckodrive.com (http://www.geckodrive.com) has lots of information for new users and hobbiests. Mariss is a pretty nice guy who you can talk to directly on the yahoo chat sites. Thou I am still mad about losing the drives(my money) we did have a pleasant letter exchange recently.

With anything else, make a informed decision since it is your money. No other guy with a company of his own is out here talking to us "normal guys"

THE motors ratings were in a copy of Home shop Machinist when they did a refit.. I don't have that copy handy. Amperage varies on the motors from a few amps to 20.. the one you have may be high or low.. and, geckos and Larkens are bipolar drives meaning you only use 4 wires, individual coil currents see twice the unipolar power current going through them while in series. My motors are running 8 amps quite well.

The Larken drives run/function so well I have nearly forgotten all my troubles. I can break a rock. Next step would be to upgrade to servo.

David Cofer, Of:
Tunnel Hill, North Georgia

11-19-2004, 07:55 AM
Oh, and..

My system is a 24+24 transformer good for 32 amps w/cube type bridge rectifier to a electronic opto relay then two capacitors out of the original bridgeport textron system. A small resistor keeps the charge trickling to the caps when the opto relay is off.

If you don't do this, a inrush will blow the bridge since a capacitor of this size (4"x8") looks like a direct short in inrush and over-amps the bridge. I had a 70volt zener across the system to dump excess. My system w/capacitor doubling sees 68vdc with the drives off.

I lost one bridge about a year ago.. no problems since..

All this is on Mariss's site with a much better explanation.

Forrest Addy
11-19-2004, 01:38 PM
The stepper drivers popular with home CNCers are optomistically rated amd poorly cooled. I suggest if you elect to go with Gecko et al and use them to full ratings you bond a finned heat sink to the weenie aluminum extrustion that came on the stepper drive and install poweful biscuit fand nearby to blow down the length of their fins.

11-19-2004, 05:47 PM
still my question isnt answered,, I need to know what voltege and ampege to go with before I decide on drives.


11-19-2004, 07:38 PM
Sorry, Don't have that page of information, it has been posted in the past here by Evan. Do a search (top right of screen) I posted what is good for my bridgeport motors. They used a whole bunch of different motors. Some can run 16 amps easily.

68vdc at 8 amps = 544 watts in my case.

Motor Filaments are designed for watts and maximum voltage (size and insulation). Factory bridgeport textron unipolar systems work off a 70 volt system coming off 3 phase control transformer inrush/reactance current limited through reactors in series with the T03 style transistors mounted on a substantial heat sink 18"x24" on the back door of the textron paper tape/cpu/capacitor cabinet. If you look you will notice you have six lead motors, A gecko only needs 4 but they must be identified. Inside the motor covers you will notice you can series motor elements, you can parallel leads, you can mix or mess them up quite easily. You need to notice the common leads and the polarity (red dots). If all else fails call a good robotics technician. You can usually hire one for $175-$250 a hour plus travel expenses. (what I charge)

If you stay around 70 volts you should be fine. Limit the current to about gecko levels of 7 or 8 amps and that should be fine. Like mentioned by Forrest, use pentuim heat sinks and fans if you decide to use geckos.

JOIN the yahoo group Mach2, DIYrobot, cadcamedmdro group and the Turbocnc group. Mariss of geckodrive does hang out in there.
Help and reading old posts can be valuable. you can gather enough information to make your motors run correctly just from the old posts here.


11-19-2004, 10:29 PM
I tried the search but came up empty. All I have from the orignal setup on this mill is the steppers. I found the mill in a junk yard owned by my cousin. The iron is in amazing condition the ways still have the frosting. It had that spindle wizard on it (what was left of it anyway) I took that off an put a handle on the down feed and it wouldnt move. I took the head off and looked inside just grease finally it came free. Dont look as if the quill was ever ran up and down. The quill is perfect all the way around with no scratches. The motor was missing along with the varable speed pullys and belt. I found a complete head (manual head) and ram in michigan (I live in Mississippi) drove up there and brought ram head and all back in a dodge caravan.

As you guys on on the J4 head BP put on the cnc machine had a solid spindle with a QC@40 on it. The QC collar fit on the new head which was hollow for a draw bar so I just put head and all on it, anyone need a J4 head, a series2 ram, tranny, and part of a spindle wizard?

OK now you all know that all I have is a PC and 3 steppers of the electronics system. PLease tell me what else I need. The steppers have p/n 025805 and have been told I should run around 70-80 volt with 7amps. I know how to wire them from a diagram that was given to me and to use larkin drives (might use geckos as a temp fix until I can get more later) I dont have an ohms meter to check the motors to know EXACTLY which ones I have as my shop is still pretty much empty so tell me what I need to do.


11-20-2004, 05:44 PM
As noted in the "posted before" 70 volts is the MAXIMUM a gecko can swallow..

If you run like I did the 24+24=48vac output transformer with a large capacitor you will have 68 volts. I think my transformer is a 3kva. Right up there next to MAX.. Dangerous ground..

(1) Transformer, (1 ) 35 amp bridge rectifier, (1) opto-22 cube to break power clean without a spark, you can power the control side of the opto-22 cube relay with a pin on the parallel port, geckos don't like sparks (voltage spike) so this is good insurance.
Some wiring (cable with color codes will save you trouble of a meter), a breakout box or someway to hook the parallel cable up to the geckos or Larkens, terminals to hook it all up.. The capacitor must be within a foot if I remember correctly. Someway to cool everything well.. A heatsink or pentuim heatsinks with fans to attach to drives.

That'll make the drives run the motors.

The motors are labeled real well in the end.

You can go to the HSM site that sponsors this, do a search and buy the back issue copy with the information on the motors. Cheap insurance.

Drives destroyed by error are not warrantied.

take your time, route the digital parallel step wires away from the current carrying motor leads. It can induct pulses into them and make the drive self-propelled.. (run away)..

Other than that? I am not much more help I guess. Look around in the sites I mentioned and you can see what others have done.

(off to the showers)...

David Cofer, Of:
Tunnel Hill, North Georgia