settle this for once

oldfella · Apr 30, 2008

I can state with absolute certainty that my smith bars weigh exactly 17.5 kgs. No counter balancing.

Scrawny1 · May 1, 2008

Quad-smack said:
Ready for a little mental fun?
The Smith machine I have at my gym is counter balanced. It has a standard bar with a set of hooks and a set of 12 inch long linear bearings affixed to it - bringing the total weight of the bar to 65lbs. There are a pair of 30lb weights with built in linear bearings to off-set the weight of the bar to approx. 5lbs.
Easy enough.
Now, what most people don't factor in is INERTIA. Everytime you press or pull the bar you have to accelerate either the weight or the counter weight which will be either the 65lb bar or the 60lb counterweight - in addition to the weight you place on the bar itself. The faster you push/pull the bar the more inertia you must overcome (same principle with free weights too).
And then there is friction - was it cleaned & oiled recently? I don't even want to get into that one...
Bottom line - to keep from blowing a gasket on this one, just record the weight you place on the bar. Unless you have an accelerometer & dynamometer attached to your smith, you will never know EXACTLY how much force you are applying/lifting.

That's why I could never be a body builder...

Too much math!

eroc613 · May 1, 2008

Flex4777 said:
Does it really matter what it weighs? lol

+3

mrshoulders · May 2, 2008

My smith machine is linear bearing w/ no counter balance...The bar weighs 45lbs so it is all true weight...

Quad-smack · May 2, 2008

Scrawny1 said:
That's why I could never be a body builder...

Too much math!

Yeah, I hate it when I have to do all the totals for Ft-lbs, Newton-meters, K-joules and Watts for the atheletes I train. Especially for micro-cycles. Strength coaches live it, head coaches love it...

Chrysler · May 2, 2008

It varies. I've used some that were heavier than using free weights when attaching the same amount of weight on each side, and some where it was easier than the same amount in free weights after adding an extra 45 pounds as if the bar weighed zero.

rotty · May 2, 2008

Quad-smack said:
Ready for a little mental fun?
The Smith machine I have at my gym is counter balanced. It has a standard bar with a set of hooks and a set of 12 inch long linear bearings affixed to it - bringing the total weight of the bar to 65lbs. There are a pair of 30lb weights with built in linear bearings to off-set the weight of the bar to approx. 5lbs.
Easy enough.
Now, what most people don't factor in is INERTIA. Everytime you press or pull the bar you have to accelerate either the weight or the counter weight which will be either the 65lb bar or the 60lb counterweight - in addition to the weight you place on the bar itself. The faster you push/pull the bar the more inertia you must overcome (same principle with free weights too).
And then there is friction - was it cleaned & oiled recently? I don't even want to get into that one...
Bottom line - to keep from blowing a gasket on this one, just record the weight you place on the bar. Unless you have an accelerometer & dynamometer attached to your smith, you will never know EXACTLY how much force you are applying/lifting.

Well...if we're going to get technical here, weight is the gravitational force acted on an object by the Earth's gravitational force, in SI it is measured in Joules. So to get the mass you would have to convert it Si and multiply it by 9.8m/s^2. But to actually get the real numbers you have to consider the whole system including pulleys, counterweights, etc... with somene sitting in a seat pushing on the bar, otherwise it would be a free fall situation. There would be multiple forces (Fnet)acting on the system, including tension, weight and normal force. You would have to know the angle of the arms in relation to the bar to accurately measure the force of the upward push (Tsin theta).

Quad-smack · May 3, 2008

rotty said:
Well...if we're going to get technical here, weight is the gravitational force acted on an object by the Earth's gravitational force, in SI it is measured in Joules. So to get the mass you would have to convert it Si and multiply it by 9.8m/s^2. But to actually get the real numbers you have to consider the whole system including pulleys, counterweights, etc... with somene sitting in a seat pushing on the bar, otherwise it would be a free fall situation. There would be multiple forces (Fnet)acting on the system, including tension, weight and normal force. You would have to know the angle of the arms in relation to the bar to accurately measure the force of the upward push (Tsin theta).

I just got wood...