Hi everybody!

Sorry if this question has been brought up before, but forum search didn't give any results (doesn't seem to work anyway, no results even for "COG"!).

How do you determine the COG of your pen exactly?
Balancing it on my fingertip is too inaccurate.


I just made a Hybrid HGG2 - which spins perfectly!
But it seems the COG doesn't coincide with the COP - is it normal for Hybrid HGG2 or did I make a mistake?

Thanks for your answers - if any of these questions has been answered in another thread, just give me a link please.

You can loop a rubberband around the pen and try to balance the pen while hanging in the rubberband,

I don't think many pens have the COG match up with the COP, unless it's a double cap mod with double tips.

Thanks for your answers!

@sketching: thanks, works perfectly - i found the COG now and marked it!

@nike t: you're right, I just read the hybrid GG2 tutorial again, it says that the COG lies within a 1 cm range of the COP, so I guess I didn't make any mistakes :D

For your information, the COG of the pen is in fact the COP. COP actually means: Centre of gravity/mass Of Pen.
If you want to refer to the middle of pen, just use MOP.

What about an unbalanced pen? The COP would always be in the middle but the COG might be towards the heavier end(it should be).

COP: Centre of mass/gravity Of Pen

Didn't you read my post?

Just use the rubber band method <_<

Yes but you are wrong.
Centre Of Gravity.
Centre Of Pen.

he's right man, not all pens have COG in COP. dont mind if it become unbalanced. well my Pilot-Bic GTX mod has COG in COP...but not all mods do

you can fix it by wrapping more rubbers on one side...my mod can change COG tho whitout adding or removeing lol....yea...uh...

Oh, god, not this again...

Alright, although COP is actually Center Of Pen, it pretty much means Center (of gravity) Of Pen. That's the way it's been for years and there is no need to change it or to argue with it.

It's fine if you prefer to use COG. I don't have a problem with it. But just know that a lot of people use COP, and have been using it forever, and it means the exact same thing as COG.

Nope, I'm correct.

Edit: Finally, managed to find that post kam made in UPSB.
http://pentrix.com/upsb2/viewtopic.php?p=2846#2846
There, as you can see, COP means Center (of mass) Of the Pen.

Regarding the COP/COG issue:
Originally, the COP is used to mean the Center (of mass) Of Pen. But, currently, it has been used less often due to the confusion with it being the middle of pen. In fact it's more common to find it being used to refer to the middle of pen nowadays.

As for the COG, it may be more accurate to refer to the center of mass of the pen. However, for a more accurate abbreviation, CG should be used instead. When refering to the center of gravity (not necessary of pen), people (any scientist for that matter) use the abbreviation CG (except for us, obviously). I believe we used the abbreviation COG because we were not able to adapt to the change from using COP to using COG, and therefore we included the "O" into the abbreviation of the center of gravity. The "O" is not necessary and should in fact be excluded in the abbreviation.