ferretlegger
Aluminum
- Joined
- May 15, 2009
- Location
- San Jose, CA
Hello everyone,
I was helping some friends in the car restoration business attempt to get a Famco 100 milling machine, which they had been given, to work. The machine is a pretty beefy old 1 HP mill, with powered X and Y axes, and a variable speed head using adjustable pulleys, similar to, although not as sophisticated as a Bridgeport 2J head. We spent quite a bit of time cleaning the ways, re-establishing the Bijur lube system, and getting the frozen NMTB-30 toolholder out, while waiting for a 2HP rotary phase converter to show up. When it did, we wired it up and turned on the motor.
The motor is controlled by a three phase contactor in a box on the side of the mill which has Allen Bradley N20 thermal current limiters on two legs of the three phase windings. The three phase power then goes to a drum switch similar to a Bridgeport for selecting On or Off and the direction of rotation. When we energized the contactor and switched the drum switch to FORWARD, the motor began to run CCW at a very slow speed, and after a short time (less than a minute), the thermal current limiters activated and shut down the power to the motor. As one might expect, the motor windings and flywheel were pretty warm. I immediately thought that the phases might be hooked up wrong, so I reversed two of the connections from the phase converter and we tried again, with identical results, although the direction did reverse.
This led to a series of troubleshooting steps. I measured the open circuit resistance between the windings (through the drum switch) at around 5 ohms for all windings. We measured the voltage applied to the windings (before the drum switch, as access after that is very difficult) and they were around 240 volts, plus or minus 15 volts, across each of the windings. The voltage agross the winding did not drop significantly when the motor was running (slowly).
We were unable to get the motor to run at speed by cleaning contacts, swapping the two leads we had access to, or anything else we tried. We explicitly verified that the motor was wired for 220 volts (not 440). The motor shaft moved easily, and there was no load on the spindle. The motor itself is EXTREMELY simple. When we removed the cover, there was an iron flywheel on top, a single set of windings about 1 1/4" in diameter, and the flange plate from which the shaft extends downwards to the driving pulley. Total height of the motor from flange to flywheel is circa 10 inches.
The motor is a Fairbanks Morse, Type QZA. Frame is 4570. No:A157179. Spec: Q0016-11.
The motor specs are 1 HP, 3 phase, 60 Hz. Full load RPM is 1745. 220 VAC at 4.2 amps. 24 hour duty cycle with 40 degree C rise. S.F=1.25 Code = J Design=B
For reasons we do not understand, the motor runs at perhaps 200 RPM. The thermal rise which shuts down the breaker is apparently due to the low speed not generating much reverse EMF, so the windings see much more voltage (and hence more current) than they would at full RPM. Unfortunately, the shop is a Fab shop and was lacking in good electrical diagnostic tools such as a clamp-on ammeter or even a really good voltmeter, so at this point we are looking for ideas. Specifically, I would like thoughts on any more wiring/troubleshooting tricks we could try to get the motor to run correctly, or to diagnose a motor electrical/mechanical issue. Secondly, if anyone can point me to a source of documentation for the motor that would be most useful. Finally, since the top of the mill where the motor mounts is similar to a Bridgeport, we had the idea that if all else fails perhaps we could make an adapter to mount a Bridgeport 1 or 1.5 HP motor in place of the current one, and put the drive pulley on that shaft. If anyone has any ideas along that line, or has any experience with such a modification, I would be very happy to hear about it.
As a piece of machinery, discounting the motor issue, the mill is quite functional. The scraping is barely worn, and the axes move freely. The shop in which this resides does restoration and fabrication of Toyota Land Cruisers and other Toyota related 4WD vehicles, and as such, their technical needs for the mill are rather modest. They would really like to be able to make slots, machine odd brackets and plates, drill positioned holes and so on. Having a well conceived Frankenmill with a Bridgeport motor grafted onto an old, but robust frame, would be a useful tool, as they do not do highly precise milling operations. All insight into these issues would be greatly appreciated!
Thanks,
Michael
I was helping some friends in the car restoration business attempt to get a Famco 100 milling machine, which they had been given, to work. The machine is a pretty beefy old 1 HP mill, with powered X and Y axes, and a variable speed head using adjustable pulleys, similar to, although not as sophisticated as a Bridgeport 2J head. We spent quite a bit of time cleaning the ways, re-establishing the Bijur lube system, and getting the frozen NMTB-30 toolholder out, while waiting for a 2HP rotary phase converter to show up. When it did, we wired it up and turned on the motor.
The motor is controlled by a three phase contactor in a box on the side of the mill which has Allen Bradley N20 thermal current limiters on two legs of the three phase windings. The three phase power then goes to a drum switch similar to a Bridgeport for selecting On or Off and the direction of rotation. When we energized the contactor and switched the drum switch to FORWARD, the motor began to run CCW at a very slow speed, and after a short time (less than a minute), the thermal current limiters activated and shut down the power to the motor. As one might expect, the motor windings and flywheel were pretty warm. I immediately thought that the phases might be hooked up wrong, so I reversed two of the connections from the phase converter and we tried again, with identical results, although the direction did reverse.
This led to a series of troubleshooting steps. I measured the open circuit resistance between the windings (through the drum switch) at around 5 ohms for all windings. We measured the voltage applied to the windings (before the drum switch, as access after that is very difficult) and they were around 240 volts, plus or minus 15 volts, across each of the windings. The voltage agross the winding did not drop significantly when the motor was running (slowly).
We were unable to get the motor to run at speed by cleaning contacts, swapping the two leads we had access to, or anything else we tried. We explicitly verified that the motor was wired for 220 volts (not 440). The motor shaft moved easily, and there was no load on the spindle. The motor itself is EXTREMELY simple. When we removed the cover, there was an iron flywheel on top, a single set of windings about 1 1/4" in diameter, and the flange plate from which the shaft extends downwards to the driving pulley. Total height of the motor from flange to flywheel is circa 10 inches.
The motor is a Fairbanks Morse, Type QZA. Frame is 4570. No:A157179. Spec: Q0016-11.
The motor specs are 1 HP, 3 phase, 60 Hz. Full load RPM is 1745. 220 VAC at 4.2 amps. 24 hour duty cycle with 40 degree C rise. S.F=1.25 Code = J Design=B
For reasons we do not understand, the motor runs at perhaps 200 RPM. The thermal rise which shuts down the breaker is apparently due to the low speed not generating much reverse EMF, so the windings see much more voltage (and hence more current) than they would at full RPM. Unfortunately, the shop is a Fab shop and was lacking in good electrical diagnostic tools such as a clamp-on ammeter or even a really good voltmeter, so at this point we are looking for ideas. Specifically, I would like thoughts on any more wiring/troubleshooting tricks we could try to get the motor to run correctly, or to diagnose a motor electrical/mechanical issue. Secondly, if anyone can point me to a source of documentation for the motor that would be most useful. Finally, since the top of the mill where the motor mounts is similar to a Bridgeport, we had the idea that if all else fails perhaps we could make an adapter to mount a Bridgeport 1 or 1.5 HP motor in place of the current one, and put the drive pulley on that shaft. If anyone has any ideas along that line, or has any experience with such a modification, I would be very happy to hear about it.
As a piece of machinery, discounting the motor issue, the mill is quite functional. The scraping is barely worn, and the axes move freely. The shop in which this resides does restoration and fabrication of Toyota Land Cruisers and other Toyota related 4WD vehicles, and as such, their technical needs for the mill are rather modest. They would really like to be able to make slots, machine odd brackets and plates, drill positioned holes and so on. Having a well conceived Frankenmill with a Bridgeport motor grafted onto an old, but robust frame, would be a useful tool, as they do not do highly precise milling operations. All insight into these issues would be greatly appreciated!
Thanks,
Michael
