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Delta Bandsaw Runs Backwards

Delta Bandsaw Runs Backwards

(OP)
Thanks if anybody can help. I've seen similar threads. I got this old Delta/Rockwell bandsaw at a garage sale. SER. # BZ2574. I got the guy to plug it in, and I saw it run for a few seconds, but may not have noticed it runs backwards. Motor specs are MASTER
THE MASTER ELECTRIC MOTOR CO. DAYTON, OHIO
SER EX 22238 STYLE 290241 TYPE CS FRAME F56 HP 1/4 VOLTS 115 CYCLES 60 AMPS 4.8 PHASE 1 RPM 1725
I had the motor apart to clean and check. It has a centrifugal mechanism. Capacitor is a Mallory 161 MFD. Cap checks good.
It was soldered in as the 110 leads were. The AC line comes in, and goes to two winding leads. These leads are soldered to a yellow wire that goes to the cap, and a yellow wire that goes to the windings. Motor seems original.
Motor should spin CCW, but it spins CW and the blade goes backwards.
I wound a string around the shaft, and spun it CCW as I hit the start switch. This causes the motor to spin CCW!
Not sure how to proceed. I can provide more details if anyone is interested.
thanks,

Dan

RE: Delta Bandsaw Runs Backwards

It looks like the start winding in your motor is badly burned, and probably non-functional if you can get reverse rotation. It would probably be wise to replace the motor. The real question is how does it start at all without a push?

RE: Delta Bandsaw Runs Backwards

(OP)
Thanks, I was wondering about the appearance. I thought it might have been factory tar-sealant or something. Wishful thinking! I believe the saw was made in 1958 according to what I could find on the Serial #.
Thanks for the response.

RE: Delta Bandsaw Runs Backwards

(OP)
PS 3DDave, thanks for the link, very informative. Seems the main winding is both black leads, and the start winding has a green wire from the centrifugal switch and a yellow wire from 110. No specific info available on this old General brand motor other than it's likely original to the machine. No idea why the motor would reverse if something is not wrong in the windings. I'll see if I can determine resistance in the windings and if there is a short or open in there.

RE: Delta Bandsaw Runs Backwards

A single phase motor will turn in whatever direction it is ALREADY turning if spun up with a pull cord if you get it spun up to where the centrifugal switch is made before you energize it. All the start winding does is what that pull cord does, get it spinning. After that it no longer matters.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Delta Bandsaw Runs Backwards

I was hoping it was just the result of a failed repair, and not well cooked. I hadn't looked at the picture because there wasn't a mention of the winding conditions. All the magnet wire I've ever seen has been copper or tinted red in color.

If it's from 1958, then that's gotten a good life out of it.

RE: Delta Bandsaw Runs Backwards

I see two yellowish wire connected to two black wires. If those wire come from the run winding and the start winding, then they are reversed.
The AC coming in should be connected directly to the run winding.
The Ac should connect to one end of the start winding and the other end of the start winding should go to the cap and then to the switch and thence to the other Ac line.
the start winding may connect to the switch, from the switch to the cap and thence to the other Ac ine.
Either way, it doesn't matter.
Interchange the two run winding leads. If the start winding is serviceable the motor should run the other way.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Delta Bandsaw Runs Backwards

Did someone say pull cord? Really?

Maybe as a test, but nothing else.

RE: Delta Bandsaw Runs Backwards

Another possibility;
Have you checked the capacitor or replaced it with a known good capacitor?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Delta Bandsaw Runs Backwards

(OP)
Hello guys. I very much appreciate all the replies! I had to send away for a solder sucker tool, and just noticed the replies this morning. This motivated me to continue. I got this machine at a local garage sale last year, $50. The guy told me it was in a school, it also has a Cutler Hammer magnetic safety switch mounted on it. If power fails, the machine will not start by itself again.
I switched the yellow leads, with some difficulty, had to get out my serious stained glass soldering iron.
The motor spins counter clockwise now!

The cap had tested good. I hadn't noticed any burnt smell whatsoever, and the black tar looking substance on the windings actually had a drip that stuck out horizontally, a clue that the motor would have been vertical when that happened- so perhaps it is a factory coating.

Grateful that I can keep the original motor on the band saw!

RE: Delta Bandsaw Runs Backwards

If the centrifugal switch isn't closed when the rotor is put back into the end bell it will not start.
If the centrifugal switch is fried together, it will not start, it will sit and hum, burn out the start windings.
If the capacitor is bad, it will not start unless it is pushed.

It looks like the start windings are cooked.

RE: Delta Bandsaw Runs Backwards

(OP)
The centrifugal switch was carefully examined, the contacts cleaned with a light buff with 600 emery paper.
The action of the centrifugal switch can be heard as the motor is operated.
Capacitor checked good.
The machine starts and operated with plenty of power to zip through a Douglas Fir 2x4.
This was an impulse buy at a garage sale. It will see occasional use. I do still wonder why it ran backwards in the first place, and there is the possibility that black substance is cooked varnish. No shorts to ground though, and as I mentioned, there is no burnt odor at all.
Perhaps a student got into the motor to re grease the bearings and resoldered the wires incorrectly - Everything was soldered, and there is no distinction between the yellow wires.
I have other motors, just wanted to keep this original.
Replies much appreciated!

RE: Delta Bandsaw Runs Backwards

Is there any chance that the original motor was shot and the owner put on a motor that he had to hand, to make it more saleableÉ

Quote (OP)

Cutler Hammer magnetic safety switch mounted on it. If power fails, the machine will not start by itself again.
You may want to verify that before trusting it. That package looks small for a magnetic contactor.
There are some manual starters with a shunt trip for undervoltage release. They are not common. You lucked out if you have one.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Delta Bandsaw Runs Backwards

I agree Bill, that looks like an NVR switch, i.e. a starter without an overload relay. Not really how it should be done. neutral

RE: Delta Bandsaw Runs Backwards

Hi Scotty. In NEMA land There are a lot of approved small manual motor starters that do include overload protection. Some of the starters use the same interchangeable overload heaters as the larger three phase magnetic starters to match the motor current.
Most of the small manual starters are toggle operated. The push button operator in that small size is unusual and probably no longer availale.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Delta Bandsaw Runs Backwards

Hi Bill,

Yeah, we have functionally similar devices over here but they're a relatively new style of device. Something like http://www.schneider-electric.co.uk/en/product-ima....

There are older types which are probably closer to what you are thinking of:
Outside http://www.cnczone.com/forums/attachment.php?attac...
Inside http://www.cnczone.com/forums/attachment.php?attac...

Sorry about the links, the [img] function wasn't working.

RE: Delta Bandsaw Runs Backwards

(OP)
Here's a couple pics of the device. No way for me to tell its vintage. As I said, the only thing the seller told me was that the machine was in a school. The switch may have been added as a safety measure. If I pull the plug when the machine is running, it will not start again until I hit the reset.
Thanks for the help once again, the level of knowledge here is astounding to me!

RE: Delta Bandsaw Runs Backwards

North American version of the thing I posted above. Would be adequate over here and I imagine equally so over your side of the pond. You really need to loop the third overload element into one or other of the current-carrying legs for it to be 'right', i.e. the current must pass through all three overload elements for correct operation of the relay, even if it will work with only two wired.

"Thanks for the help once again, the level of knowledge here is astounding to me!"

Most of us have been doing this stuff for a living for a long time, some longer than others. smile Thank you for the kind words.

RE: Delta Bandsaw Runs Backwards

My bad. I didn't focus on the box with the magnetic starter in the picture. I was looking at the push button station.
We have single phase motor starters that are about that size. Almost all were toggles but at one time there was a push button version.
As to the wiring of the overloads in the magnetic starter; That meets all past and present codes.
There are two main issues when all three overloads are not used.
The first issue is differential protection. You must pass the current through all three overload heaters in order for the differential protection to function properly.
That old starter does not have differential protection, it is a melting alloy type and each pole functions independently.
The second issue is total heat in the enclosure.
Those starters had a chart pasted inside the case that gave you the correct heater part number based on the motor FLA. As you can see, there is a factory installed jumper in the center pole and the chart will take into account that the total heat in the enclosure is from one instead of two or three overload heaters.
Those melting alloy heaters ran pretty hot and the total heat in the enclosure would affect the tripping point.
To compensate for this, some manufacturers used a slightly different chart for;
-Single phase use with one overload heater used.
-Three phase use with three overload heaters used.
-A basic box as is use on the band saw.
-A combination motor starter.
-Some may use another chart for use in an MCC.
-Another chart may be used if the starter was to be a component in a relatively large control panel.

A note to the OP.
If the starter trips on overload, give it time to cool down and for the melting alloy to solidify.
The melting alloy overloads were reliable and dependable, BUT.
When a production machine tripped on overload, some operators had a habit of pumping the reset button to try to get going as soon as possible. The alloy would often catch and hold before it was properly solidified. Sort of a cold solder joint effect.
Then the overload would start tripping at less than rated current.


Bill
--------------------
"Why not the best?"
Jimmy Carter

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