2016 POTD Thread Archive

[cathead]

A bridge rectifier is simply 4 diodes hooked in a ring. You can test all four
diodes to determine if each one conducts one way but not the other.
Usually a bad diode will be shorted if it fails from an overload. If it trips
the breaker, you can be relatively sure the diodes are shorted.



edit: For clarification, this can be accomplished with any simple analog
or digital volt-ohm meter. Personally I prefer an analog meter
for these kinds of tests but a digital one would work as well.
I use the X100 scale in resistance (ohms) for this as
one can quickly see the forward and backward resistances.

 

[hman]

One way to test the motor itself would be to totally disconnect it from everything else, then connect a car battery across it with some jumper cables or something similar. Obviously, it won't run at full speed ... but it should at least turn over. If it shows no sign of wanting to turn at all, the motor is probably bad. If it goes at all, it's probably OK, and your problem is likely elsewhere else (like the rectifier, switch(es), wiring, etc.

 

[intjonmiller]

Today had to be productive. I would have kicked myself all week at work if it hadn't been. I got a lot of stuff cleaned up in my little shop. It's so crowded (1950s excuse for a 1 car garage, with wood and metal working equipment) that any project makes a huge mess, even though it really isn't that much stuff.

One thing that has been driving me nuts is that I don't have anywhere for lathe tools yet. I'm planning on building a cabinet with many shallow drawers below the chip tray, but that's going to have to wait until I wrap up some other things. The space above/behind the lathe is also wasted, so that's where I focused today.

I made two shelves. The lower shelf is 5" deep, the upper 10". Size was dictated by the scrap on hand. Both are made of 1/2" plywood on top with a 2" plywood skirt around the sides to stiffen it. The shelves bridge the window, which is why the reinforcing skirt was necessary instead of just more brackets.

I had a 20" strip of LED lights leftover from another project, so I mounted them on the underside of the upper shelf, about 3" from the front. That way it casts light well in front of the lathe, but my eyes are shielded by the shelf skirt. My dad is the only other one I expect to use the lathe at any point in the foreseeable future, and he's my height so this should work very well.

I also have a 4"x6" grid of LEDs (MUCH brighter) which I will mount on an articulating arm (just as soon as I build it...) for more focused and intense light where/as needed.

Finally the lathe and the light will be on the same power strip switch, so the light will serve as a reminder when I'm leaving the shop that the lathe still has power. By switching it off at my head-height my 6 year-old son won't be able to turn it on should he feel so inclined.

 

[intjonmiller]

made one of these...

That's on my list of things to make. Also a tippy-top.

 

[intjonmiller]

A bridge rectifier is simply 4 diodes hooked in a ring. You can test all four
diodes to determine if each one conducts one way but not the other.
Usually a bad diode will be shorted if it fails from an overload. If it trips
the breaker, you can be relatively sure the diodes are shorted.

Thank you for all the tips! When I searched for how to test a rectifier the results I found showed guys using power supplies and a diode test mode on a much nicer multimeter than mine. I'll test the impedance of the rectifier and the lower voltage motor test tomorrow.

 

[dave_r_1]

Bought a Snapper 52 hydro walk behind mower and then worked on servicing it. Lubed and changed engine oil/filter, sharpened blades. Used my fancy home-made blade sharpener, which worked great. The blades were so dull, after sharpening each side of a blade, I had to adjust the grinding wheel down.

Still to do:
-replace the hydraulic fluid/filter [not done because I couldn't get the filter today]
-figure out how to inflate one of the front tires. can't get it to seal along the bead, tried wiping/rubbing the tire and rim surface down with a rag, spraying on windex [helps with making it seal just enough to get air pressure to hold it on the bead, didn't work], trying green slime around the bead on each side overnight and see about inflating it tomorrow. If that doesn't work, see I can get proper "rim sealant"
-fix the deck height adjustment screws. it's stupid that they are way up at the front of the deck and sticking up above the frame, so something solid can hit them and bent them over a bit, and they are threaded screws...

It's a little tricky to drive, left and right levers on a horizontal handlebar, you have to hold both in the 'middle' of their range of travel to be stationary, you release [so it goes forward] one or both levers to turn forwards/go forward, and pull one or both levers to turn in reverse/go in reverse. And it's faster than my Gravely Zero Turn. There will be a little bit of a learning curve for me.

Bone-headed mistake of the day: while warming up the motor to change the oil, was leaning over to look at the hydraulic system, and placed my hand squarely on the spinning air inlet on the top of the motor [the grill just over the fan that pushes air over the rest of the motor]. Fortunately, the bolts holding the grill only damaged a bit of my thumb, rest of the fingertips just have a good rubbing-burn thing happening.

 

[bmw rider]

This was a welding project not machining, but had to make room on my welding cart for a new TIG welder. The cart was a donation from a friend originally and I had made it work for my MIG and Gas setups. I had to do a bit of reworking when I upgraded my MIG to the Miller 211 from the cheapo one I started with. Still, it was an ugle abomination of a cart. This time I had to do a bit more work to fit the new TIG. I cut half of the top deck off and fabbed up a two tier rack to hold the welders. I decided it deserved a coat of paint this time as well rather than the bare rusty metal it had always been. Haven't tested the new welder yet, have to get a bottle for it yet. I'll be doing lots of practice to learn the process as I've never used a TIG before. Lots of gas welding in years past though, so I understand the basic technique, just need to learn to apply that to TIG welding. I've found a few good tutorials online, but am open to any direction to other good sources. Once I figure out plain steel, I'll move up to aluminum and stainless which are part of the reason for the TIG.

 

[xman_charl]

finished my static rotor balancer last night after a ton of futzing around and it works! It always stops with one part of the flywheel down and will even reverse direction to rotate to that point if it goes past it. Didn't have time to do an drilling and testing last night, that's on the list for tonight. Really excited about getting this balanced better and having a nice smooth motor on the lathe.

View attachment 128930 View attachment 128931

Do you have access to another lathe? Might put it between centers on another
lathe, check it will running. Indicate for run out first.

Charl

 

[mattthemuppet2]

Do you have access to another lathe? Might put it between centers on another
lathe, check it will running. Indicate for run out first.

Charl

good idea, but sadly just the one lathe. If I'd thought it through, I would have used the LH threaded arbor I made to turn the flywheel true before taking the other pulley off the motor (and before painting the flywheel!). Just never thought it would be that out of round and out of balance!

I did get it largely balanced, much less vibration now. I'll post pics in a bit

I am however doing what you suggested for another treadmill motor - truing the pulley and flywheel between centers (actually, 4 jaw and center) before doing the same balance job I did for my lathe motor. Hopefully that'll cure any vibration problems before they start

 

[Mark_f]

good idea, but sadly just the one lathe. If I'd thought it through, I would have used the LH threaded arbor I made to turn the flywheel true before taking the other pulley off the motor (and before painting the flywheel!). Just never thought it would be that out of round and out of balance!

I did get it largely balanced, much less vibration now. I'll post pics in a bit

I am however doing what you suggested for another treadmill motor - truing the pulley and flywheel between centers (actually, 4 jaw and center) before doing the same balance job I did for my lathe motor. Hopefully that'll cure any vibration problems before they start

Is there a reason you are using the treadmill flywheel? Why not take it off and put a pulley on.