View Single Post
Old 12-29-2008, 09:27 PM   #31
Bud
Bionic Poster
 
Bud's Avatar
 
Join Date: Jul 2007
Location: San Diego, CA
Posts: 30,814
Lightbulb

Quote:
Originally Posted by lionel_101 View Post
Just wondering,

If I set my tension to be at 50 lbs and when I pull the string and the bar is horizontal is it exactly 50 lbs that nice.

If I ratchet it up once more and now the bar is pointing about 5 degrees upward, did I just increase the tension on the string or is the tension still 50lbs? You decreased the tension (about 0.2 lbs - value according to LF's earlier post when reference tension was 60 lbs.)

I am pretty dumb and didn't understand any of the math stuff, but it seems if the bar is pointing up then the tension on the string is higher then what it is set at, otherwise the bar would keep falling. Isn't this the reason when it drops below horizontal you need to keep ratcheting it up more and let it drop again until it is horizontal? No, when it drops below horizontal, the tension is also less, by the same amount, as when it's above horizontal. If it's 5 degrees above or below horizontal, it will be 59.8 lbs. (assuming a reference tension of 60 lbs.)

Can some tell me if I am right or wrong if the

Bar pointing up means to much tension? Incorrect (see above).

Bar pointing down means to little tension? Correct (see above).

Bar pointing horizontal means it is just right? Correct (see above).

Thanks

As a simple empirical proof of the above, try the following:

1. Tie a weight (anything close to a pound or more) to the end of a 12"-15" long piece of string. **You can also hold a fairly heavy shoe by the end of one of the laces for the same effect **

2. Tie the string to the end of your finger.

3. Place your elbow on the edge of a table and rotate your forearm so that it points straight to the sky (weight should be hanging directly beside your forearm).

4. Rotate your forearm so it horizontal and hanging off the table (weight should be hanging 90 degrees from your forearm, now).

5. Observe the effort it takes to resist the weight as your forearm moves closer to horizontal.

6. Now, let your arm drop below horizontal and see if you can feel the weight decrease (less effort) the further your arm drops.

7. Lift your arm back to vertical then try it again.

** the heavier the weight... the more you'll feel the effect.

Last edited by Bud : 12-29-2008 at 09:38 PM.
Bud is offline   Reply With Quote