Audio Analysis of PowerPro

[bainin]

hey guys -

Well I am back and running again. Now on to the next possible problem-which I think has always been there since I first owned the tool.

I can hear a wobble or rattle on the tool, most notably for me at low speed (250rpm) but that may just be my bad high frequency response at this point

It almost sounds like something is shifting position, then stopping against something else at the low rpm settings.

I noticed when i hooked everything back together, the eccentric adjustment didn't seem to do much for the noise level and that the eccentric position is far from the 9 o'clock mentioned in the install manual..its probably more like 1 or 2 o'clock. With the belts on, it was impossible to shift the eccentric all the way back to 9 o'clock...I think I could maybe shift it to 11 or 12 o'clock at the most. Tension on the belts at 1 or 2 o'clock seems reasonaly equal with a 1/8 to 1/4" deflection-more toward 1/4".

Also noticed-there is a slight bit of play on one of the motor mounts-since I don't know the exact names-i will take a picture after i tear it down some but the mount bracket slides into the fins on the motor and this is where i can see some play on one side. Its almost like the fin slot is a bit wider than the mounting bracket mate piece that slides into it.

I'd like opinions on if this sounds like a healthy tool-or needs further tinkering and what might be some places to investigate.

The video was recorded with a saw blade mounted, upper saw guard removed and anything else i could think of which might cause vibration type noises.

https://vimeo.com/439306988


Any thoughts would be appreciated.

b

[JPG]

I would be suspicious of a loose pulley.

Someone please enlighten me with the details of adjusting the power pro belt tension(equalization). The details above confuse me.

IIUC adjusting CW increases motor belt tension while decreasing drive belt tension(and vice versa). Any thing past 12 inverts that.

[bainin]

JPG showed a good image of where I see the play on the motor mount.

tempsnip.png (105.71 KiB) Viewed 5803 times

[JPG]

JPG showed a good image of where I see the play on the motor mount.

tempsnip.png

Dusty posted the pix first.

[DLB]

I think the issue with the 'nine o'clock' position may be one of communication. Specifically, what represents the hour hand in this? This direction comes during installation of the eccentric and idler shaft, so the eccentric starts out with the upper belt loose. The split in the eccentric is near 12:00 and the recess in the eccentric used for adjustment is near 6:00. (I think the latter is the hour hand.) Then you adjust the eccentric "clockwise toward nine o'clock until the belt is tight." To me that suggests belt tightness is the objective, not the degree of rotation.

The eccentric only has 180 degrees of useful adjustment, so the only way I can envision you getting to 1:00 or 2:00 is using a different 'hour hand,' perhaps the split in the eccentric? Or I am misinterpreting something.

In any case, the above step is done with only the upper belt in play. Once you add the lower belt (also a poly-v) then either direction you try to adjust the eccentric is tightening one of the belts (while loosening the other). Because you are tightening an already tight belt, it is not going to rotate very far without a fight.

The noise in your video is not normal in my experience. First thing I would try is the low speed testing with no saw blade attached. See this post: https://www.shopsmith.com/ss_forum/view ... 13#p111713 I'm going to summarize it as the engineer stating that evaluations need to be done under normal conditions, i.e. saw blade spinning at saw speeds. And more importantly that the control algorithm is more complex than we might intuitively believe.

Is the "play" you see in your motor mount actual movement or just a gap? Actual movement seems unacceptable to me and may be the source of the noise.

- David

[bainin]

Alright- sorry got distracted by making a jointer blade sharpening jig.

I've done some further investigation now.

1. Disconnected the motor from the belt and ran the motor alone. Very quiet.
2. Reconnected belt, remove quill and ran. Some noise, but certainly less than with quill engaged.

Its a 2 bearing quill and there is a minor amount of sliding (<1/32") back and forth along the quill axis. Could that indicate a bad bearing?

I took a couple of photos-hopefully someone can educate me on previous parts of the discussion above.

First - the eccentric position ... is that 4 oclock or 10 oclock?

Also-at 6 o'clock in the image- seems I am missing a retaining screw/washer?

IMG_20200722_150829680.jpg (66.07 KiB) Viewed 5620 times

2nd- I noticed that the offsets for the front and back of motor brackets were different.
Measuring the gap near the offset screws- the top is ~ 5mm, the bottom about 3.9mm.

IMG_20200722_150841261.jpg (61.23 KiB) Viewed 5620 times

However, a straight edge running from the motor pulley surface across to the belt pulley is making pretty close to 90deg.

I couldn't find any guidance on if the offset gap top and bottom should be the same?
I adjusted the top set screws to be roughly equal gap, and the bottom screws to be roughly equal gap..but not equal top/bottom .

I have to assume I want the belt to be perpendicular to the eccentric axis--which is why I left the motor angle the way it is shown on the brackets.


b

[JPG]

ecc 10 o clock.jpg (68.96 KiB) Viewed 5614 times

[DLB]

So, as JPG rotated your picture the missing screw/washer is at 12 o'clock. I reckon the function of the screw/washer is somewhat less critical on a PowerPro, but they would normally be there. I had a conventional headstock that was missing the same parts, and in fact the hole was not threaded so they were never there. (And it did not have a problem in its first 17 or so years of use.) https://www.shopsmith.com/ss_forum/view ... 90#p268690

A very small amount of 'play' of the spindle inside the quill seems normal. I can hear this more than feel it. I'll try to rig a way to measure a couple of samples.

Does your install manual have section E? It refers to the Tensioning Setscrews at the pulley end of the motor and the Belt Alignment screws at the other end of the motor. They are not adjusted equally, having different purposes. (But IIRC the install video said they should be equal?) Procedure says to adjust them using a straightedge so that the face of the motor pulley is aligned with the center of the Poly-V Pulley on the Idler.

- David

[DLB]

I set up a dial indicator on the main table to measure end play of two sample spindles in their quills. Both were two bearing quills. The two measurements I got were 0.004" on a near-new quill and 0.006" on a 2003 (I presume) quill. Basically I held the dial indicator fixture tightly in the T-slot with one hand while manipulating the spindle in and out with the other while all locks were tight. Both of these quills are good to the best of my knowledge. Tentatively, I'd be concerned with anything exceeding ten thousandths (.010).

- David

[bainin]

Thanks David ,

I read somewhere another simple test which I did today.

Run at speed where rattle occurs.
Loosen and retighten quill setscrew to see if any change in rattle (no change)
Extend quill, loosen and retighten quill setscrew to see if any change in rattle (no change)

b