Original BP M Head 110/220v Troubleshooting

[Shiseiji]

The reason behind trying to salvage this motor is the shaft length and diameter. Not an easy combination to find. Also this is for a "M-D" or M drill with a taller belt housing for more pulley steps and a longer shaft than my other M head. Looks like it's never been abused other than zero indication it was ever lubed.

My other M Head is off the mill because the metric to SAE key I made for the metric shaft 3Ph motor with the longest shaft I could find at the time isn't tight enough and it is walking out of the key way despite the set/grub screw. Chicken or the egg . . .

The M-D motor will spin up without a load. Nothing with a load.
Capacitor has no markings. Tried a 50 micro farad 370/440, sat and hummed.
Removed motor (cast iron frame, at 66 this is getting old) and disassembled to check centrifugal clutch. Clutch appears to be fine, contacts closed have continuity through the points and starter winding. Point open fine and break the circuit. Starter field doesn't present being grounded.

Ideas?

TIA

 

[markba633csi]

Could it be wired for 220?- can you show the wiring terminals or terminal strip?
50 ufd might be too small also- I would expect a higher value with a 1/2 hp motor- 100 or more

 

[Geswearf]

I suggest you read this. Did you check to see if the windings are broken?

 

[Shiseiji]

Could it be wired for 220?- can you show the wiring terminals or terminal strip?
50 ufd might be too small also- I would expect a higher value with a 1/2 hp motor- 100 or more

No, it's wired for 110/120v. The wiring marches the label on the inside of the lead access panel and the cord and wiring set-up looks original and untouched since placed in service.
I didn't bookmark the topic/thread, but picked the value based on what I read here. Not to say I didn't miss-remember something when I placed the order.

I'm going to try to educate myself some more at the link Geswerf provided.

 

[Shiseiji]

I suggest you read this. Did you check to see if the windings are broken?

Thank you, first glance looks very informative. "No but" the windings look incredibly good for a motor that I would guess at a minimum is ~ 60 years old. No oil contamination, no appearance/smell of burned varnish, wires are stiff, and I don't see any cracking/broken insulation. Not to say that isn't a valid question I may have to get a definitive answer to it.

 

[Shiseiji]

Could it be wired for 220?- can you show the wiring terminals or terminal strip?
50 ufd might be too small also- I would expect a higher value with a 1/2 hp motor- 100 or more

Mark, interesting. At the site Geswerf provided, they give a formula: C = (7150 x HP) / (V x PF). Power Factor is raerly known, not on my data tag, so they suggest a generic 80%. Quickly jammed into a spreadsheet we get:

7150​

0.5​

110​

0.8​

40.625​

and a round up is 50. Expect I'll be trying to trouble shoot the field windings tomorrow.

Mark, after I posted the above, I found a generic table further down so this is an edit. Looks like your expectation is spot on.

Small Motor Capacitor "Ballpark" Sizes Based on Motor Horsepower

1/2 Hp or 0.37 KW, 120-150 VAC

320-400 µF

 

[Ulma Doctor]

most of the 1/2hp 1P motors on 110v i see in my line of work have between 150 and 250Uf capacitance

 

[markba633csi]

Yeah I was going to say around 200 to 250
I don't know where the 7150 formula originated- it seems more applicable to a PSC or capacitor run motor
at least at lower voltages

 

[Shiseiji]

most of the 1/2hp 1P motors on 110v i see in my line of work have between 150 and 250Uf capacitance

Good information, thanks. I've used that as my criteria and have found what should work.

Of all things I found a capacitor showing a single picture of the bottom, below, that is the first I've seen that matches the bottom of the OEM. Sadly not the range needed: U.S. Seal Start Capacitor 25-30 Mfd 125V BC-25

On Amazon less than half the descriptions include dimensions, but did find one that should work: 216-259 uF MFD 220-250VAC Round Run Start Motor Capacitor, +/-20% Tolerance, 1-3/8" x 3-11/32 and the price makes me think it's been in production a long time $9.99

I've found one motor repair company in Olympia, no air conditioning suppliers that appear to have over the counter sales. Granger is like :90 away with a listing for a Dayton Motor Start Capacitor: 110 to 125V AC, 216-259 mfd, Round, 3 3/8 in Case Ht, 1 7/16 in Dia. Sadly no 220v in a size that will fit in my cover.

Now that I have an idea what to ask for I'm going to try the motor repair company for over the counter.

Thanks again for the guidance!

 

[Shiseiji]

Yeah I was going to say around 200 to 250
I don't know where the 7150 formula originated- it seems more applicable to a PSC or capacitor run motor
at least at lower voltages

Thanks again, another bit of useful information. I did a quick search and looked in the Copeland document and couldn't find a reference. I probably won't put any more time into trying to figure out where it came from.