Can't PC Pressure be Simplified?

[Brett LaCroix]

I read many posts describing how many pounds of pressure to be applied to the PC... but this is hard to judge... and practicing on a bathroom scale is really inaccurate.

 

I put a 1/2" black strip on the back of my backing pad... so I can see the rotation.

 

Now all I need to know is, how fast should the pad rotate?

 

Pressure is irrelevant... since depending upon the speed (which also affects torque)... the same amount of pressure will cause the pad to rotate at different speeds depending upon the speed setting of the PC.

 

Conversely... different amounts of pressure will be required to keep the pad spinning at the same rotation speed at different PC speed settings.

 

So... have you marked your backing pad?

 

.... and if so, what rotation speed should we be shooting for?

 

Brett

[Team Adam's]

I could shoot a video later possibly to show you how I let mine spin, but you have to remember that the "correct" amount of pressure also depends on how aggressive you want to be in removing defects, the product you're working, and pad you're using, the panel you're working, etc.

 

At speed 6 on an XP almost no amount of pressure is going to completely stop the rotation of the pad, while relatively low pressure on speed 4 will stop it completely. Curvatures of body panels can also impact rotation speed as well... remember the head of the PC is not a forced rotation so many other things other than the setting on the dial and applied pressure will impact the rotation of the backing plate.

 

At speed 5 I like to see the line go around 1x every 3-5 seconds, roughly... I've never actually counted it out, but from memory thats what it would seem to be. The best advice I can give is go to work on a test panel and get a feel for it and keep in mind there are many right answers to the "how much pressure question" just as there are many wrong answers... machine polishing is not an exact science, its as much an art form that you learn by practicing IMO.

 

BTW... beautiful BMW!!

[Brett LaCroix]

I agree about it being variable...

 

Just saying that for the novice... telling someone to draw a line on their pad and shoot for "x" number of revolutions... is MUCH easier than telling them 8-15 lbs.

 

That number means nothing to me... but I can easily watch the pad spin and judge my pressure based on that.

 

Brett

[Team Adam's]

I agree about it being variable...

 

Just saying that for the novice... telling someone to draw a line on their pad and shoot for "x" number of revolutions... is MUCH easier than telling them 8-15 lbs.

 

That number means nothing to me... but I can easily watch the pad spin and judge my pressure based on that.

 

Brett

 

True, but thats also why I added this:

 

Curvatures of body panels can also impact rotation speed as well... remember the head of the PC is not a forced rotation so many other things other than the setting on the dial and applied pressure will impact the rotation of the backing plate.

 

Start maybe on the hood or truck of a car (flat surface) and put enough pressure to actually bog the machine down, then back it off to just before the machine started to bog... the reason I suggest that method is that your eyes and concentration need to be more on making gradual/methodical movements, keeping the pad flat, and working the product, not counting the pad revolutions.

 

I've watched people try and do what you're saying at clinics and other events and the problem generally becomes that they get so fixated on maintaining a constant count on that black line that they lose focus of the rest of the process which is far more important.

 

I can't stress enough... the rotation of the pad has VERY LITTLE to do with the correction process using the PC, its actually more just a byproduct of the function of the machine. Focus more on working the product, keeping the pad flat, and 'feel/hear' the amount of pressure. Free your eyes up to focus on the process.

[Chewy]

Honestly... I'm with Dylan on this.

 

WAY to many variables to lock in values. It is MORE an art then a science IMO as well.

 

I'm still learning and I've done it several times now.

 

Chris

[Team Adam's]

Brett -

 

The nice thing is, even if you do it "wrong" the first time theres nothing you can do with the PC (short of pounding your hood with it) that can't be fixed with the PC. Even if your technique is off by a mile on the first attempt you just treat it as a learning experience, redo the same area and correct it... really there is nothing to worry about.

[Junkman2008]

I agree about it being variable...

 

Just saying that for the novice... telling someone to draw a line on their pad and shoot for "x" number of revolutions... is MUCH easier than telling them 8-15 lbs.

 

That number means nothing to me... but I can easily watch the pad spin and judge my pressure based on that.

 

Brett

 

You're making this way too complicating by thinking too much. Look at this chart as to the way I do it and I know that you have seen my results. This chart does not include any reference to my slow cut technique.

 

Speed Setting #1: Used to spread the polish around before you start working it. Pressure is totally irrelevant. Use any amount that you want because the pad does not need to be spinning in order to accomplish this.

 

Speed Setting #2: Useless.

 

Speed Setting #3: Used to spread wax around. Pressure is not a concern because you are not correcting anything.

 

Speed Setting #4: Not used.

 

Speed Setting #5: The most important speed of all because this is the speed I work at. First, if you can watch that mark go around AND count the revolutions, you are a better man than I. But something that is extremely simple for me to do is:

 

1. Place a scale on a table next to the car.

2. Place the pad of the PC on the scale and support it until it is flat.

3. Look at the reading and begin to apply pressure.

4. Once you reach a reading of 9-15 pounds, notice the feel. Let up and reapply that pressure a couple of time.

5. Whip the polisher around to the car and apply that same exact pressure. Bam, you've got a pressure gauge!

 

There is no guess work in that technique. You are not trying to guess rotations, it is an exact science. You apply the pressure to the scale, and then to the car. After going back and forth enough times, you don't have to watch the black line. You will develope a feel for the amount of pressure that is needed. It is literally that simple.

 

The speed setting of six is one that I personally never recommend to a novice. I feel the polisher can be out of control to someone who is not use to it and thus, they never develop a good paint correction technique at that speed. Once you learn how to use the polisher effectively, you can venture up to that speed however, I am able to do everything you see in my write-ups at a speed setting of 5.

 

Thus, 5 is the only setting where pressure is of any concern. For all of the other settings, speed is of no concern. When you follow my chart, things are a lot less complicated and you are not introducing unnecessary variables into the use of the polisher.

[b_pappy]

I was giving a customer a demo the other day, trying to explain the same thing about the PC. He was worried about burning the paint, etc. I put my hand down on his hood and put the running PC on top of my hand, explaining "you can't burn the paint, so use the pressure you need, I suggest seeing the timing mark spin about like a second hand on a watch." I don't know if anyone has done the PC on top of the hand, but it really helped convince him he was safe using it.

Bruce

[Chris@Adams]

Brett you got a lot of good advice here, just remember it is like anything you do it take practice.:pc:If possible go get a panel from a junk yard and practice away!

[11chevz71]

Brett you got a lot of good advice here, just remember it is like anything you do it take practice.:pc:If possible go get a panel from a junk yard and practice away!