Sheave block mechanical advantage?

[RNeumann]

A pulley has to be attached to the load, to be considered a mechanical advantage. If the pulley is attached to the anchor, it's just a change of direction.

Mechanical advantage are always in odd numbers, due to having to have an anchor point. Example, 3:1, 5:1 etc.

You can have even number mechanical advantage.

 

[Spanner]

You can indeed.
And there are several other errors in earlier posts in this thread.
The following article may help explain:

Pulley | encyclopedia article by TheFreeDictionary

 

[Brad_Blazer]

If you pull with some tension T and have some number of strands N at the same tension leading to the object you want to move, the total pulling force is T multiplied by N. (neglecting friction)

 

[RNeumann]

If you pull with some tension T and have some number of strands N at the same tension leading to the object you want to move, the total pulling force is T multiplied by N. (neglecting friction)

And angle/distance between winch and anchor

 

[turnkey4099]

You can have even number mechanical advantage.

yep. I commonly use 2x1 and 4x1. from anchor to pulley on load. 2nd line is from anchor through pulley attached to the free end of line coming from the pulley on load and back to the winch.

I've moved some huge logs using just my 1/2 ton F150 2x...actually a 1x as the positrac doesn't work. Drawback with 4x1 is you have to pull 40 ft of cable to more the load 10 feet.

 

[Egon]

Ahh - look up pulleys & mechanical advatage. Basically the distance the load moves compared to the distance the puller moves will tell the tale.

 

[bcp]

To simplify, count the number of lines going to the moving object. That is your mechanical advantage to one.

Bruce

 

[dougtrr2]

Take some time to look over the entire operation. How much persuading on the direction of fall are you going for? Keep in mind that there can be a massive amount of energy stored in a tree. If it starts going the wrong way you may not be able to stop it. Check you tube for idiots with chainsaws to get some great pointers on what NOT to do. Be careful out there.

Doug in SW IA

 

[Billy Bee]

Take some time to look over the entire operation. How much persuading on the direction of fall are you going for? Keep in mind that there can be a massive amount of energy stored in a tree. If it starts going the wrong way you may not be able to stop it. Check you tube for idiots with chainsaws to get some great pointers on what NOT to do. Be careful out there.

Doug in SW IA

The trees are dead ash about 10 in. at the base, and maybe 30 ft. tall. They are close to the road and I don't want to fell them in the road. I am going to fell them parallel to the road. I could probably do it with no "persuasion" , but I want to be sure. I have used my sheave block many times on trees much larger than these. I understand the dynamics of the energy stored in a tree, I would never try to force a tree to go where it flat won't go. I wear chaps,forestry helmet,ear and eye protection,steel toed boots, and always make sure I have a clear escape route. Yes I have seen the videos, the idiots and also the informative how to videos from Stihl and Husqvarna. I try to be as safe as I can, for myself and bystanders. I have great respect for trees, even after they are down they can hurt you. I will be careful.
Thanks for your concern,
Bill

 

[LD1]

Its already been covered, but keeping it simple.....

With a single pulley.....with the pulley anchored solid and not intended to move......nothing more than a change of direction
With the pulley attached to what you are wanting to move, and thus the pulley moves....2:1 advantage in force....half speed