Adding Weight To The Inch

[gerryg]

Just ordered some magnets. Been meaning to ever since I saw this threead materialize. Looking to add them to the inch, blob, kettlebells... Should be great.

Jedd, which magnets did you buy?

[tspinillo]

I get a lot of use out of Platemates. They are invaluable for blob work, hammers, etc and very durable.

[Jedd Johnson]

http://www.gaussboys.com/ndfeb-magnets/B5006.html

Those are what I got. Richard, I had no idea you offered magnets, so my bad. I am mainly looking to add weight to kettlebells.

-Jedd-

[bunchofbananas]

Call me stupid but i still don't see how the offset handle causes the inch to rotate more than a revolving handle, i don't doubt it does but can anyone explain it precisely. I mean if it was offset surely wouldn't you pick it up when the handle is at the highest point to prevent rotation?

It must be offset in a different way than i imagine.

The handle is not offset. Mull this info over for a bit. This explanation was submited a few years ago right here on the board by a former member named Nathan. probability theory of the inch rotation.

There is a formula for the moment of inertia of a sphere. Since a sphere's mass m=(density)x(4/3)x(pi)x(radius)^3, the moment of inertia is I=(2/5)x(mass)x(radius)^2. That's the rotational equivalent of mass. A rotating body with a big moment of inertia is hard to keep from rotating, just as a barbell with a big mass is hard to lift off the floor. (^2 means squared & ^3 means cubed if you didn't already know) So if the mass stays the same, the moment of inertia would increase by 2/5 for every unit the radius is increased. The units are kg*m^2 (say kilogram-metres squared)

Barbender, also a member here, followed Nathan`s post with this observation:

The rotational inertia formula given is for a solid sphere rotating about a diameter of the given sphere. To calculate the rotational inertia for a dumbbell we first need to decide on an axis of rotation. Nathan's point is correct in that the rotational inertia increases as the spherical diameter of each bell increases.

I've only just read this reply and thanks for the post.

However, inertia taken into consideration, there must still be a position to hold it whereby it doesn't rotate.

Pinching it by the handle's diameter would do just this.

Inertia only counts for anything if the object is rotating. I suppose there is rotation even on a revolving bar when you pick it up normally.

It is obvious why the fixed globes would cause greater torque but i had thought there would be a way of picking it up with no rotation. Reflecting on this, there is a way, but it is biomechanically much harder.. e.g. pinching it up.

Even a standard olympic barbell tries to roll with double overhand, and this is due to the fact that the fingertips are hooking it against the pads of your hands. The fingertips being weaker is why the barbell would force them out, as opposed to forcing the pads out.

To conclude: When picked up conventionally all barbells will roll due to the anatomical structure of the hand. However non-revolving handled dumbbells will deliver more torque as they have greater inertia.

Edited October 14, 2006 by bunchofbananas