Need Help!- Harbor Freight BD812 motor problem

[mechatronic]

Hi. My lathe now has trouble running in the 'reverse' direction (the one that I use). It runs fine in the forward direction. When set in reverse, it will either:

-stall and hum
-if pushed by hand start for a half revolution, the power will cut, and the cycle will start again.

I did a visual inspection of the motor and everything looked good. The machine has only 10 hours or so on it over the last 2 years. I guess I'm more of a mill man

Any ideas?

Thanks in advance,

Alex

[TroyO]

That's the 8x12 (8x14) right? I don't have any clues, but mine is working so far so if you need some pics or something to compare wiring or how something looks I can do that.

[mechatronic]

Yes, it's the 8x12 harbor freight model no. 44859.

Thanks. One nice thing about it's low use is that's it's pretty clean.

I'll run through some basic diagnostics and tear it down and post the results here.

[mechatronic]

I tried the motor without the belts connected and had the same problem.

I have noticed that there is what sounds like a brake engaging when the power is cut to the motor after it runs in the forward (working) direction. I don't hear this electronic clutch sound when running in the reverse (broken) direction.

Does anybody know on which side this clutch is located? It would be great if I didn't have to do a complete disassembly to whack the proper part with a hammer.

[mechatronic]

So I took the motor apart. There's no clutch or brake, and everything looked clean. Re-assembled and still the same problem. The motor spins freely in both directions.

I'll take it apart again tomorrow for a closer inspection.

[TroyO]

I read somewhere on a forum about the capacitors in the motor being likely suspects on another motor problem. Any chance there's one for each direction, and if so could you reverse them and see if it then runs the other way?

[Mike Nash]

Here's a link to the drawing I did of my lathe's wiring.

http://www.cnczone.com/forums/showpo...56&postcount=4

I never ohmed it out to see which wires get tied where through that switch, but I suspect the switch may be your problem area. The motor should have a centrifugal switch that opens above start speed to disconnect the start capacitor. If reverse is never running fast enough to open the switch you won't hear it close when you are stopping. It could still be the start capacitor too if it happens that the motor develops just a little more torque in the forward direction and can get the motor moving fast enough for the run capacitor to be sufficient.

Check all of the connections. My HF 12x36 lathe wouldn't start and there were wires almost falling out of terminals. Of course the start capacitor failed a month or so later also! There was also a thread on one of the Yahoo groups about issues with the 8x motor/wiring. But then I can't recall which group.

I've got a 1 HP AC servo motor and drive I plan on sticking in my 8x12. I'm thinking a position controlled spindle could be fun.

[Ziuck]

My HF 8x12 motor failed last week. Started making a weird noise and wouldn't go in one direction. After a while my cap blew.

I replaced the cap with a 330uF cap since my local electronics store didn't have a 300uF. All is well now! Cost was $7.00

I've been looking on e-bay to for an AC motor and VFD conversion but haven't had much luck find a motor around $50

[mechatronic]

I didn't get the email that you'd replied so I'm sorry for the delay.

I'm strongly suspecting the wiring now too. After two disassemblies the motor looks good inside. I desoldered the caps and they look good (resistance steadily rising when tested with a mulitmeter). I also removed the switch and it shows good symmetric low resistance between the terminals. The big indicator that it is the wiring is that when pushed in the forward direction with the switch in reverse, it turns forward with the same low speed.

It's probably just a loose wire, I'll check that out as soon as I can. Thanks for the blown cap warnings.

-Alex

[mechatronic]

I removed the forward/reverse switch and re-installed it and now the motor works fine. I guess somebody just did a crappy job of screwing down the wires.