PC jiggling but not spinning

L

lazybum

New member
Not sure if this is supposed to happen but when I'm polishing my car with my PC 7336 and the sonus das kit the pad jiggles like it should but it doesn't spin. Is that normal?
 
That is pretty much the way they are suppsed to work. Its not like a rotary where it just spins in one position at high speeds. they call these 'Random Orbital Polishers' for a good reason. ;) Fear not. You aren't the first to wonder if their PC is working properly. :bigups
 
Yea, i undestand it doesn't spin in one place but I thought it's supposed to jiggle while spinning. Its just jiggling but not spinning at all.
 
Your PC can spin, but thats under little to no pressure. Also your pad being off center will make it harder for the pad to spin. Like Anthony said, the PC is not necessarily supposed to spin, it just happens sometimes and does not have the effect of the rotary.
 
Physics experts plz correct me if I'm wrong:



A PC oscillates, which means that it goes back and forth very fast. A PC will 'spin' when you turn it off, not sure if it spins when you turn it on. The PC is going in one direction right before you turn it off. Normally the PC goes in the other direction (oscillation), but with the power off the pad keeps on going in the inital direction, causing the pad to spin.
 
If you just use the weight of the PC, it will spin. A cyclo will spin and oscillate, which is why it is a more aggressive machine than a PC.
 
Scottwax said:
.. A cyclo will spin and oscillate, which is why it is a more aggressive machine than a PC.
Click to expand...
Do the Cyclo pads rotate freely if the power is off and you spin the pads by hand?



If so then the motion is the same and any extra aggressiveness would come from differences in orbital radius, motor power and speed.





PC.
 
the other pc said:
Do the Cyclo pads rotate freely if the power is off and you spin the pads by hand?



If so then the motion is the same and any extra aggressiveness would come from differences in orbital radius, motor power and speed.





PC.
Click to expand...



They will rotate freely when the unit is off, but unlike the PC they continue to spin and also oscillate when you apply pressure. Definitely a more powerful motor. I've been using it for paint correction and the PC for final polishing. They compliment each other very well.
 
Yeah, but wait a minute!



Remember that the PC is a DUAL ACTION machine.



Use a clean pad, speed #5, a 'reasonable' amount of polish, and NO pressure, the pad will spin freely, and 'jiggle'.



Apply a little pressure - til the machine begins to bog down - and you'll see the rotation slow, or stop.



I mark my backing pads with a Sharpie at about 5 points to monitor the rotation...



Jim
 
Possibly pointless observation: The PC was originally designed as a RO *finish sander*. Used properly, a sander doesn't have pressure put on it; it relies on (only) the abrasiveness of the paper for its "cut". As soon as we lean on it a bit to better effect paint correction, we're "misusing" the tool (and yeah, I lean on it too). Sorta plays into what Jimmy Buffit pointed out. Perhaps that's why the PC seems (to some of us at least) to work so much better for applying glazes and LSPs than for paint correction.



I wish somebody would open up a PC and see how the thing is driven. The Cyclo uses direct gear-drive. No matter how much force you put on it, it acts the same-the heads go around, driven by the gears. The free-spinning heads make it "random" as opposed to being like a rotary. I somehow suspect that the PC uses an elliptical cam rather than gears but that's *purely* speculation based on how it behaves.



the other PC- Heh heh, we go around and around on this without really figuring it out :D but the Cyclo is sure a different animal than the PC, as ScottWax has found out. The fact that he is planning to get a Cyclo to compliment his PC says it all...remember, he's the guy who did incredible work by hand for all those years. A brief test-drive with the Cyclo and he's ready to spend some pretty big money on one.
 
Put a 4" pad on your PC for spot repair work and the pad will spin even if you put a fair amount of pressure on it.



If you want to maximize the cutting ability of your PC, while working those difficult imperfections, a 4" pad is the way to go.
 
RedondoV6 said:
Put a 4" pad on your PC for spot repair work and the pad will spin even if you put a fair amount of pressure on it.



If you want to maximize the cutting ability of your PC, while working those difficult imperfections, a 4" pad is the way to go.
Click to expand...



Yeah, now that you mention it I've noticed that too (funny how it slipped my mind until now :o ). It still bogs for me, but it does seem to spin more than with the big pads. About the only correction I ever do with the PC is small areas where I use the 4" pad and it works better than I'd expected. FWIW, I'm using the 6" counterweight with the 3.5" flex pad and 4" foam pads (getting lazy, I used to fit the 5" counterweight for use with the smaller stuff).



ScottWax- Heh heh, :up on appealing to Santa for the big-ticket items :D
 
Accumulator said:




FWIW, I'm using the 6" counterweight with the 3.5" flex pad and 4" foam pads (getting lazy, I used to fit the 5" counterweight for use with the smaller stuff).
Click to expand...



Same here Accumulator, I use the 6" counterweight with any sized pads I use, including my 4" pads/3.5" backing plates.



I also find the the 4" pads to be useful when cleaning glass and polishing wheels etc. Very useful items to have around, inexpensive too!
 
Accumulator said:
...I wish somebody would open up a PC and see how the thing is driven. ...



the other PC- Heh heh, we go around and around on this without really figuring it out :D but the Cyclo is sure a different animal than the PC...
Click to expand...

I love the internet! It saves all kinds of work. Porter-Cable and Cyclo both have exploded diagrams on their websites. Both machines are direct drive with gears fixed to their motor armature shafts.



The Cyclo's motor armature is parallel to the pads' orbital axes and directly drives the two eccentric shafts with helical gears.



The Porter-Cable's motor armature is perpendicular to the pad's orbital axis and directly drives the eccentric shaft with a pinion and crown gear set.



A bobcat and a cougar are also different animals but do work exactly the same way. One is somewhat more powerful, both are effective.



Haven't seen a power specification for the Cyclo. I suspects it's significantly higher than the PC.





PC.
 
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