I think something is binding and causing the breaker to pop

[cmn135]

Hello everyone,

Recently bought a working '84 mark v. Decided to do some preventative maintenance. Waxed the tubes, oiled the sheaves and vacuumed the dust out inside the case. That is all I did. To do this I ran it up to full speed as instructed to expose the bottom sheave oil hole. Shut it off, did my oil with 3 in 1 and vacuumed.

When I went to turn it back on it hesitated and popped the breaker. I took the casing back apart and tried one or two more times and same result. It seems to spin ok by hand but I'm new so I'm not sure how much resistance there should be. The belts seem properly tensioned. I attributed it to being on a 15 amp breaker with some lights on and trying to start it on high so I took a break for a few weeks till I could run a new dedicated line.

Flash forward to today. I have a new 20 amp breaker run with nothing else on it. This time it hesitates longer, then finally starts to spin and then pops again. This time a very faint burning smell. Hopefully didn't cook the motor.

Then I spin it by hand back and forth a little and though it moves ok it 'sounds' like the belt is rubbing and I'm not sure if this is normal. I took a brief video and tried to rotate it and show the different sheave and belt positions. Any ideas? Should it make this sound?

I can't seem to figure out how to embed the youtube video properly, my apologies.

https://youtu.be/RbqxBPnK4ME
[youtube]https://youtu.be/RbqxBPnK4ME[/youtube]


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[ChrisNeilan]

Quite often it you try to start the headstock on fast speed the breaker will pop. That is one of the reasons you should turn the speed to slow BEFORE turning the shopsmith off. Do not attempt to chang speeds while turned off as damage is likely. Turn the quill by hand while turng speed to slow then start it up and see if things are back to normal. Good luck.

[cmn135]

Ok so I rotated the quill slowly counterclockwise while slowly turning her down to the slowest speed and it does fire up. I ran it up and down a few times. I even shut it off around a mid range speed and it turned on fine again.

I'm still a bit nervous though. From what I've read starting on high can often blow a 15 amp breaker but what about a 20 and what about the very slight burn smell. Does the sounds in my video sound ok? I just want to be sure it's truly fine before putting her through her paces and potentially damaging something. I don't have a good handle on what sounds and feels normal on these yet.

Thanks for the help!


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[wa2crk]

OK I tried to answer before and when I tried to submit my computer gave me the "internet connection has been lost" message for the third time this week.
Anyhoo try disconnecting the motor from the motor drive belt and see if the motor runs up to speed normally. If it runs OK check that the shafts rotate with minimal resistance. This test is subjective at best but there should be no noticeable resistance.
Changing to the 20 amp breaker is a good idea as long as the service to the house is good. Try putting a table lamp on the same circuit as the Shopsmith and see if there is a noticeable dimming when the machine is turned on.
If there is excessive loss on start up because of a compromised voltage supply then the circuit breaker may not improve the conditions.
Check the poly V belt and make sure it is in the correct groove and not rubbing on the casting.
One of the reasons that SS says to back the speed down is to lower the start up load, the other is for safety to lessen the chances that an operator may start the bandsaw or some other SPT from being started at an excessive speed.
I would not try the motor more than a few times if it seems to drag and not come up to speed because it is possible to burn out the windings. Most SS motors are NOT protected by an internal heat sensitive thermal switch.
Bill V

[cmn135]

Thanks Bill. What's the correct groove for the poly v belt? Mine isn't quite in the middle and is more to the right against the sheave if you can see in the video. Perhaps that's why I hear what sounds like some belt drag?


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[reible]

The sound is very mechanical like the sheave rubbing on the the motor bracket. That should not effect the start up but should be corrected.

(Some times if the poly v is too tight it can cause the starting problem.)

Lots of other potential issues.

Ed

[reible]

Forgot to mention, the belt position seems alright, most times if you are in the third groove from the left it is fine but sometime a particular situation could happen where it isn't but that would be rare.

Ed

[dusty]

12ga or 14ga wire? That is the real question. Just upping the breaker can present safety issues. Furthermore, a 20a breaker on a 14ga feed may be against the local building code.

[cmn135]

Hi Dusty, thanks for checking on that one. I did run a new 12 gauge line. Thankfully not my first rodeo running electrical.

Thanks for the advice guys. I will pop her back open shortly and investigate further. I appreciate the advice!


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[everettdavis]

When you took the belt off the motor and let it run no load I am sure you manually rotated the quill by hand and felt the condition of the Drive assembly.

If you do that with the 12" sanding disk on and turn it with your fingertips you can feel a good bit more about how freely the mechanisms rotate.

It helps me assess tight bearings, belt set in the poly-v, and as you rotate by hand, run the speed dial up and down.

Measure the width of the Drive Belt across the face. If it is less than 1/2" it's time for a new one as its width controlls how deep it rides in the sheaves at either end of the range.

The power switch can occasionally deteriorate the contacts and increase the start load with added resistances.

Not your first rodeo with electrical so good idea to pull switch out checking both it and the condition of the wires leading to it, and the condition of the power cord and the connections

Everett