Can a single phase motor be wired to run in reverse

So i have spent lots of time trying to bridge the knowledge gap. I can say with about 90% confidence that I know know how an AC induction motor works. What use to be PFM is now knowledge. This video was the AH HA! moment for me. It deals with 3 phase motors but it made it much clearer. The same gentlemen has a video on single phase motors that build off of this video. In conjunction, they made it seem easy.

I then found this video which helped some. It is by the same creator and builds off of the knowledge above and makes it seem easy.

In this video he discusses a method to use a mulitmeter to determine which winding is a running and which is the start winding. In its most simplistic form, the winding with the highest resistance is the start winding because it (most typically) uses a lighter gauge wire for its winding being as it is not in continuous use. Using this concept I set out with my trusty (now 20 year old) Fluke and got to work. I have 6 total wires in the junction box. 1 through 4 are gray and 5 and 6 are black. My multimeter does not test capacitance. Quick amazon order later, I have one on the way that will. This means that the capacitor is still untested. However, it started fine with I test ran it so that is not a priority. I do know however that wires 5 and 6 are the wires that bridge across the capacitor. I checked for continuity across those leads after ensuring the capacitor was safely discharged and the removed. I know that leads 1 and 2 are low resistance as well as 3 and 4. Both pairs reading less than 1 ohm (I think, Auto ranging might be getting me here). I hade no resistance across just 5 or 6 and had more than 1 but less than 2 across 5 and 6 with the capacitor in place.
A photo of the capacitor for reference.
325A1B25-F8BA-4AC4-A083-549A25997687.jpeg

With knowledge comes more questions. Does 5 and 6 represent the start winding? Is the capacitor giving me false information here?

I did further test continuity across the other lead (1-3-4, 2-3-4, 3-1-2, 1-5-6, 3-5-6) and got none across those. I also read somewhere that capacitor can be polar or have a polarity. Mine had no markings as such.

To add to this puzzle I have another machine, long story don’t ask unless you want to give it a good home, that had a very similar motor. It is a 4 pole single phase dual voltage 1720 RPM but it is 3 HP. I mention this because it has a fwd/rev switch already wired in that I can peak at to help wrap my mind around the physical application compared to the theoretical.

Now, as I understand it, if I feed the start winding from the other side it will change the rotation. Please insert corrections here. As a more practical application, if I swap leads in 5 and 6 in the wiring diagram then that should change the direction of rotation. Correct? Insert more corrections here. That leads me to a problem with my specific application in that I have 4 terminal bars in the motor junction and 3 are used. Further more the brass bars are molded into the unit and not removable. How would I wire the motor in this application? When I say how would I wire it, I mean all the way back to the 4 line wires coming in. I understand that it would be 3 line (2 hot 1 neutral) and then the green ground. The green ground gets bounded to the box at each of the stops along the way (drum switch and then motor casing). With the other 3 (black red and white) carrying the current. How many terminals on the drum switch? I have seen 8 12 and 16 terminal variations, with my thought being an 8 terminal being correct for this application.

What are the errors of my ways? If I have to change windings or go beyond the changing of some wire’s in the junction box, I would rather spend the money and look seriously at 3 phase and VFD. I get little time and want to progress as I mentioned in the original post. If I can make a few wiring changes, let do it.

@RJSakowski I saw your article before I had full grasp on how things work and it seemed more than I could chew on both in terms of skill set and mental capacity. Might be different now but you are much braver than I am at this point.

@Eddyde The video you posted is good but it did not speak to me like the others I posted I have however watched it.

@Ulma Doctor You sir have been a help. I watched your videos on the lubrication of your Shen Wei lathe which happens to be a be fundamentally the same as my Lantaine LAM 350B 10x24 lathe. It was a good guide to maintaining my machine once I get here QCGB back together so that I can try and get that machine running. I thought I had it all lined up last week but the thrust bearing I ordered were wrong so I am waiting those to finalize that. I am guessing that your post about he SSR switch would answer the drum switch question from above. I will try to look at that when I get a minute.

Thank you to everyone has replied and anyone that will reply to this post. I however go back to work tomorrow and don’t get more than 24 hours off at any one time April 1st. My day job is running around on the ambulance causing trouble so I swing back into that shift work staring tomorrow and will not be able to get much productive time in the garage or keeping track of progress here. Just don't want anyone to think I abandoned the topic or lost interest. As Arnold would say “I’ll be back.”
 
Mikeyc66 said:
@RJSakowski I saw your article before I had full grasp on how things work and it seemed more than I could chew on both in terms of skill set and mental capacity. Might be different now but you are much braver than I am at this point.
Click to expand...
At that point, I had little to lose as the motors had been sitting around gathering dust for thirty years. It was an experiment and it worked out. It was also an educational experience.

The thing to remember is that motors, or for that matter, anything manufactured has an assembly procedure to make the finished article. The key is determining the procedure used and to reverse it for disassembly. There are a number of interesting videos of completely rewinding a motor which gives some insight as to how the process works.

In the case of a motor, the windings are assembled onto the core and the leads are connected appropriately. Then the insulation is placed over the connections and the coils are wound with cord to prevent movement in use. Finally, epoxy or varnish is applied to the coils to further lock the assembly. It is simpple emough once you understand the process.
 
The lazy man's way to locate the start leg is to look at the 220 volt configuration:
The start leg is never directly across the line but is instead found from the center point of the two series main windings to one side of the line
so that the start leg only sees 1/2 the supply voltage (120 volts instead of 240)
You can see that 5 and 6 fit that description; swap those to reverse
 
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The capacitor is non polarized as it is labeled a motor starting capacitor and rated for 120 volts ac. Looking at another motor won't necessarily give you insight as to how this one is wired.

As illustrated in the photo in post #12, if the numbering corresponds to that on the terminal block, it would place the capacitor directly across 120 volts which cannot be. More than likely, one of the numbered wires at the capacitor is connected to the switch or start winding directly and the other brought out to the terminal block. Some probing with a multimeter can sort it out.

I would disconnect all the wires at the terminal block. From the plate, wire #2 is most likely one of the run windings. Find the other end by checking continuity. Wires 4 & 6 are candidates for the other run winding. Find the other end by checking continuity. One of them will be connected to another wire; either 1, 3, or 5. Verify that it is a run winding by comparing the resistance to that of the winding connected to #2. The remaining wire will be part of the start winding circuit. The start winding circuit consists of a winding, a centrifugal switch, and the capacitor.. One side of the capacitor will have continuity through the winding, Whether it is direct or through the switch depends upon how the motor was configured.

If you are lucky either 5 or 6 will be connected to one end of the start winding circuit and the other will be connected too the far end, In that case, reversing 5 and 6 at the terminal block will reverse the motor but I would want to verify that by tracing the wiring before plugging it in.
 
In most cases 5 & 6 (or 5 & 8) or red and black or Z1 and Z2 will represent the entire start leg (cap, switch and winding)
Some Dayton motors and a few others are stinkers though and don't follow that.
 
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Here you go:
Ignore the 5 and 6 numbered capacitor wires, just a factory redundancy
You are only interested in the wires at the terminal block-
Disconnect wire #6 and extend it to reach the drum switch as shown- looks like there's a spare position on the terminal block you can use
To invert rotation vs. switch handle, move that wire from drum 4 to drum 3

-Mark (This connection flips the polarity of the start leg to reverse)
THDS240v.jpeg
 
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Two steps forward, one step back. I am struggling with the practical application. It is that junction of theory and application that has me scratching my head. The problem is this, every video and practical demonstrations show the reversal process with a 110VAC feed. I understand the less wires and less voltage but it also leaves a hole my knowledge. 220VAC as single phase power uses 3 or 4 depending on your specific circumstances. I will be using 4 wires and trying to bring the machine up to current standard. That would mean 4 line (line meaning bring power into the machine) wires, black and red traditionally representing your hot legs, white is the neutral and green is the ground. I am very confident that many of you know that part, however I am trying to bridge theoretical and practical and do not want any crossed wires. Every pun possible is intended there.
At the switch to reverse the run direction, if I base this on the applications I have seen, will I be switching one of the hot leads and the neutral lead to gain the changes in direction? If that is the case then in my application, 4 wire 220VAC single phase, I would use black and white to control the direction, red would pass through the switch to keep from being constantly but not change positions and then green would be bonded at each location as is appropriate. Is that right? Does it matter if i use red or black?

Thank you @markba633csi for the drawings. They are helpful and in fact lead me to realize that gap in my knowledge.

So i am moving forward in attempting to add the forward reverse function to my little mill. I am acquiring parts and that means a switch and wire. I have narrowed it down to this switch,
Baomain Universal Rotary Changeover Switch SZW26-40/D303.3D with Master Switch Exterior Box 660V 40A 12 Position 3 Phase https://a.co/d/9cct7Ic
It is a 12 position 3 phase rotary switch that is rated 660VAC and 20amps. The motor is rated at 7 amps at 220VAC.

87D48A07-191F-4254-AA12-526ABAC2DEDF.jpeg
That wiring diagram for the proposed switch. Before someone asks, i choose the 10am o switch based on physical dimensions. It will fit in the space that I have as a working final resting place. @markba633csi, I am guessing that this switch would use the 3 phase diagram you so graciously provided above.

Also to handle the physical wiring layout of the motor, I confirmed the following with the multimeter:
For the continuity test, I have continuity across 1and 2, 3 and 4.
Testing resistance across the windings show:
1-2 = 1.2 ohms
3-3 = 1.1 ohms
5 = 0.3 ohms
6 = .2.7 ohms

I pulled the end cover and confirmed that 6 is the start winding as it goes through the centrifugal switch. That switch looks to be in good shape without removing it. I also confirmed that the capacitor is good with the correct multimeter. It is rated at 300 mfd and tested at 320 mfd.

What else am I missing?

Thank you everyone for helping me out. I feel like the dumb guy in the room but you have all been immensely helpful.
 
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