What's my mechanical advantage

[CarpeDiem 427]

Hi folks, I am rebuilding the vang on a Cookson 47 that I am racing on out of Australia occasionally.  The vang was repaired after a breakage and I am trying to calculate what the current mechanical advantage is of this setup.  I don't know how the formula works when a compound pulley system is connected to an intermediate cascaded system.

 

In the attached diagram the dotted line is confusing me and I don't know how to calculate it.

 

I am probably not going to rebuild it like this, I just want to know what the advantage is, because it's adequate and I don't need more or less.

 

Thanks

[RushMan 31]

7 x 2 x 2 .... 28:1 (less friction)

 

After more thinking....

 

If the compound pulley system finished at the top triple block it would be 7 x 2 x 2 but as it finishes on the boom it might be only 6 x 2 x 2

[CarpeDiem 427]

So it makes no difference that the compound 7 is linked to the load as well?

 

I don't understand this, why doesn't some of the force from the 7 get distributed away from the 4 and directly to the load.

 

What if the dotted line was attached to the second pulley from the top, would it still be 7 x 2 x 2, or would there now be some equal or unequal distribution of the 7.

 

I totally get that if the dotted line was attached to the block of three, then it would deffinitely be 7 x 2 x 2, but I am not understanding why it would be still 7x2x2 when one leg of the 7 is connected to the to load.

 

Thanks

[RushMan 31]

Instead on finishing on the boom is it an option to finish at the top triple block?

 

Are you looking for less or more purchase?

[CarpeDiem 427]

Instead on finishing on the boom is it an option to finish at the top triple block?

 

Are you looking for less or more purchase?

 

I can build it anyway I want, I just kind of want to know what the advantage is, cause it's got me stumped.  My guess was it's somewhere between 24:1 and 28:1...

 

Thanks

[madyottie 82]

I think the movement of the top block is going to be so minimal as be unnoticeable.

 

Isn't it just going to increase friction by a similar negligible amount?

 

I'd just call it 28:1

[RushMan 31]

I can build it anyway I want, I just kind of want to know what the advantage is, cause it's got me stumped.  My guess was it's somewhere between 24:1 and 28:1...

 

Thanks

Call it 26:1 and time to rip the top of a cold one

[Ed 143]

25:1 by my calc, 24:1 through the Cascade, plus 1 extra fall

[Black Panther 1,579]

I get 24;1

[Adrianp 119]

25:1 by my calc, 24:1 through the Cascade, plus 1 extra fall

I get 25:1 too by imagining 1kg of load applied to the yellow line and then adding it up a 6x2x2+1 for the anchoring of the tail on the final cascade block 

[Black Panther 1,579]

Yep, missed the +1, 25.

[madyottie 82]

I'll go with the 24:1, should have turned the phone sideways for a better look.

 

Not sure how to work out the extra part.

 

Just do a practical test, set it, measure it, shorten the whole thing by say 50mm, and see how much line it uses.

 

Good way to test all our thoughts.