Ping Pete - Mechanical Advantage

Following our discussion yesterday, I did as you suggested and had
something of a mixed bag of results:

Leg Press

This machine has no moving pulleys but the strap moves around three
static rollers.

Using the distance of the movement of the weight, over the distance
travelled by the seat, there was a reverse ratio of 31:21.

This means that the stack of 150 kgs (15x10) is actually heavier than
believed with a plus differential of 71 kgs, making a total of 221 kgs
or 148%.

Arm Curl (Low Pulley)

A positive advantage ratio of 33:53, reducing the stack of 100 kgs
(20x5) to 60 kgs or a 40% minus differential.

NB
Some confusion here, as the weight and arms are moved in order to get
into the start position. However, we stuck to the principle used for
the other machines, and measured the distances moved while carrying
out the actual lift, which was obviously less.

Seated Military Press

A positive advantage ratio of 31:43, reducing the stack of 100 kgs
(20x5) to 72 kgs or a 28% minus differential.

Do these sound to be realistic results for such machines? I am
particular confused about the leg press machine. I can only assume
that the reverse findings were the result of drag/friction over the
guiding wheels/rollers.

All numbers and calculations are approximate.

"Charles" <jrh@msn.com> schreef:

> Following our discussion yesterday, I did as you suggested and had
> something of a mixed bag of results:

> Leg Press

> This machine has no moving pulleys but the strap moves around three
> static rollers.

> Using the distance of the movement of the weight, over the distance
> travelled by the seat, there was a reverse ratio of 31:21.

> This means that the stack of 150 kgs (15x10) is actually heavier than
> believed with a plus differential of 71 kgs, making a total of 221 kgs
> or 148%.

> Arm Curl (Low Pulley)

> A positive advantage ratio of 33:53, reducing the stack of 100 kgs
> (20x5) to 60 kgs or a 40% minus differential.

> NB
> Some confusion here, as the weight and arms are moved in order to get
> into the start position. However, we stuck to the principle used for
> the other machines, and measured the distances moved while carrying
> out the actual lift, which was obviously less.

> Seated Military Press

> A positive advantage ratio of 31:43, reducing the stack of 100 kgs
> (20x5) to 72 kgs or a 28% minus differential.

> Do these sound to be realistic results for such machines?

Seems pretty accurate, especially the last one.

Is it possible for you to test your strength on the Smith machine?
Just calculate what you moved on this particular Military and load that on
the Smith.
Thats the only way to be 100% sure, with of course a -/+ 5% margin of error.

I did that when i calculated the overhead i used, and on the Smith i was
pretty damn close.

>I am particular confused about the leg press machine. I can only assume
> that the reverse findings were the result of drag/friction over the
> guiding wheels/rollers.

I admit its a bit weird. Most machines have levers where the weight stack
only moves a portion of arms/legs.
If that leg press had the stack moving more distance that the seat, i guess
its safe to assume that 48%

Its unusual, though...

Can you test your strength on an old fashioned Hack, were you load the
machine with plates on each side?

----
Pete

Proly changes a little over the lift, as the angle changes.
but not much.
------
Mr. P.V.'d (formerly Droll Troll), Yonkers, NY
Stop Corruption in Congress & Send the Ultimate Message:
Absolutely Vote, but NOT for a Democrat or a Republican.
Ending Corruption in Congress is the *Single Best Way*
to Materially Improve Your Family's Life.
entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie,
all d'numbuhs
"Charles" <jrh@msn.com> wrote in message
news:865kk2hff08t0rcacmjbos84eksjco0s2q@4ax.com...
> Following our discussion yesterday, I did as you suggested and had
> something of a mixed bag of results:
>
> Leg Press
>
> This machine has no moving pulleys but the strap moves around three
> static rollers.
>
> Using the distance of the movement of the weight, over the distance
> travelled by the seat, there was a reverse ratio of 31:21.
>
> This means that the stack of 150 kgs (15x10) is actually heavier than
> believed with a plus differential of 71 kgs, making a total of 221 kgs
> or 148%.
>
> Arm Curl (Low Pulley)
>
> A positive advantage ratio of 33:53, reducing the stack of 100 kgs
> (20x5) to 60 kgs or a 40% minus differential.
>
> NB
> Some confusion here, as the weight and arms are moved in order to get
> into the start position. However, we stuck to the principle used for
> the other machines, and measured the distances moved while carrying
> out the actual lift, which was obviously less.
>
> Seated Military Press
>
> A positive advantage ratio of 31:43, reducing the stack of 100 kgs
> (20x5) to 72 kgs or a 28% minus differential.
>
> Do these sound to be realistic results for such machines? I am
> particular confused about the leg press machine. I can only assume
> that the reverse findings were the result of drag/friction over the
> guiding wheels/rollers.
>
> All numbers and calculations are approximate.
>

On Thu, 2 Nov 2006 17:34:38 +0100, "Pete" <phoutstra@wanadoo.nl>
wrote:

>"Charles" <jrh@msn.com> schreef:
>
>> Following our discussion yesterday, I did as you suggested and had
>> something of a mixed bag of results:
>
>> Leg Press
>
>> This machine has no moving pulleys but the strap moves around three
>> static rollers.
>
>> Using the distance of the movement of the weight, over the distance
>> travelled by the seat, there was a reverse ratio of 31:21.
>
>> This means that the stack of 150 kgs (15x10) is actually heavier than
>> believed with a plus differential of 71 kgs, making a total of 221 kgs
>> or 148%.
>
>> Arm Curl (Low Pulley)
>
>> A positive advantage ratio of 33:53, reducing the stack of 100 kgs
>> (20x5) to 60 kgs or a 40% minus differential.
>
>> NB
>> Some confusion here, as the weight and arms are moved in order to get
>> into the start position. However, we stuck to the principle used for
>> the other machines, and measured the distances moved while carrying
>> out the actual lift, which was obviously less.
>
>> Seated Military Press
>
>> A positive advantage ratio of 31:43, reducing the stack of 100 kgs
>> (20x5) to 72 kgs or a 28% minus differential.
>
>> Do these sound to be realistic results for such machines?
>
>Seems pretty accurate, especially the last one.
>
>Is it possible for you to test your strength on the Smith machine?

Not until January, when we get a whole new gym including the Smith
machine.

We had a great weights room but lost it ages ago due to persistent
drug problems, both performance enhancing and recreational. It
attracted some awful oafs who should never have been there, and caused
an increasing loss of respectable professional clients, particularly
those on packages provided by their firms as part of their employment
perks (like me!).

>Just calculate what you moved on this particular Military and load that on
>the Smith.
>Thats the only way to be 100% sure, with of course a -/+ 5% margin of error.
>
>I did that when i calculated the overhead i used, and on the Smith i was
>pretty damn close.
>
>>I am particular confused about the leg press machine. I can only assume
>> that the reverse findings were the result of drag/friction over the
>> guiding wheels/rollers.
>
>I admit its a bit weird. Most machines have levers where the weight stack
>only moves a portion of arms/legs.
>If that leg press had the stack moving more distance that the seat, i guess
>its safe to assume that 48%
>
>Its unusual, though...
>
>Can you test your strength on an old fashioned Hack, were you load the
>machine with plates on each side?

Unfortunately, we won't be getting anything traditional, but some of
machines we are getting are the latest models supplied by Life Fitness
and are purported to be really good quality equipment. YMMV!