Monday, July 30, 2012

It's Alive!

Sunday was beautiful compared to the rain filled misery of moving day. The first task of the day was to re-install my fence. Surprisingly I think it's leaning less than when we took it apart. I'm pretty sure a stiff breeze could have brought it toppling over.

I started looking over the lathe and getting familiar with all the levers, dials, screws, etc. I had seen it run before but I didn't have the knowledge or the time to test out every little thing. So my first order of business was to get the motor running so I could test everything out.

A little background first. The motor on the 4914 is a 1 horsepower, three phase, 220 volt model. Three phase is the type of current that industrial sites receive, not your typical DC residential apartment which has single phase power. There are several ways you can drive a three phase motor on single phase power but I will only be discussing the path I chose, using a Variable Frequency Drive, or VFD for short.

After doing a lot of online research on various brands and types, I purchased a Teco Westinghouse FM50-101-C. It is probably the cheapest most robust VFD I could find that met the requirements I need. Essentially it takes 110V single phase power, and converts it into 220v three phase, and it's rated for 1 HP. That's important, you have to make sure the VFD is rated for your motors HP. It seems that in the early days of VFD's you had to choose a VFD that was rated for MORE than your motors HP but I've found that is not the case anymore. Also, I've found a lot of other home machinists have used this same model to hook up their three phase machines, so there is a lot of 3rd party advice on how to connect one.

I'll be getting into the really cool functions of the VFD and exactly how to hook one up in a later post. For now, I just wanted to get the motor running. Call me ghetto if you like, but I live in an apartment, and my shed doesn't have power, so I run any electrical devices off a heavy duty 12ga extension cord. Crazy you say? Well maybe. My friend Grant who helped me unload it told me I should hire an electrician! ha!

The lathe has a heavy duty three phase fused disconnect switch on the rear of the machine. I opened this up and started disconnecting both the motor leads and all the wires coming out of the drum switch, which is used to put the machine into forward or reverse. All I needed was the 3 leads from the motor plus it's grounding wire. I hooked these up to the VFD and plugged it in. I made sure the lathe was in direct drive (not in back gears) and that the feed control lever for the lead screw was in neutral. I hit the start button and the motor purrs to life. It's alive!

video

The motor's "native" frequency is 60hz, so by lowering that frequency the motor runs slower. I slowly ramped the speed up to 60hz and everything sounded good. No crunching noises, relatively quiet. The belt drive was set somewhere in the middle of it's speed range. I ramped down to half speed, 30hz, and stopped the motor. I wanted to try out the feed control and since the tumbler bracket for the quick change gear box is broken I wanted to keep it in relatively low speed for testing. I set the QCGB to a relatively fine feed rate and had to wedge a wrench under the broken bracket to keep it in gear. I started up the motor again. The lead screw was slowly turning! All the levers on the apron were pretty tight, but I was able to engage the half nut lever and see the carriage move on it's own. I then tried the longitudinal feed lever and again, the power feed worked. Finally I tried the cross feed and that too worked! So far so good.

The feed control was set in the lower position so it was feeding away from the headstock. I stopped the motor and put it into the upper position to test feeding towards the headstock. This is when I got some nasty grinding noise and immediately stopped the motor. What I found was that when the feed control lever is in it's upper notch, it's not quite engaging the gear train. I pulled it out and pushed it PAST the notch and re-tried. No grinding, everything works. I'm hoping something may just be misaligned and can be fixed. Overall not a huge problem.

At this point I moved the belt over to the highest speed position of 1700 RPMs and let her rip up to 60hz. Whoa, no bad noises but this thing can scream at these high speeds.  I'm hoping the restoration will quiet a few things down a bit.

I had not attempted back gears because I couldn't seem to get the back gear pin to pull out. I was spraying it liberally with PB blaster when finally I gently pried it loos with a screwdriver. Then I was able to engage the back gears and try it out at low speed. As before everything functioned properly.

Now that I know everything works for the most part, I decided to start tearing into the machine to clean it up... But that's for another post.


2 comments:

  1. gotta love that first power-on... definitely a step in the right direction (or counter-clockwise direction for that matter)

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    1. A bittersweet first power-on. Since I was only testing to see if it worked before I completely tore it down. Now I'm anxious to get it restored so I can start actually using it!

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