snatch blocks

[dahfred]

If a snatch block effectively halves the effort does it then effectively halve the strain, force, applied on your fixtures. ie a hand winch with a rated pull of 1.6t, will the shear pin survive on heavier pulls. Same goes with the other fittings like the hook and wire.

[kimamigo]

erm........no.....think of a snatchblock like a gearbox.....just gears down the effort involved, not the total amount of force required

[killa]

Increase the capacity of the TIRFOR
The lifting and pulling power of TIRFOR machines can be greatly increased by the use of multiple sheave blocks.
These can increase the nominal capacity of the TIRFOR machine by 2, 3 or 4 times or more (see diagram). For most applications, an allowance must be made for friction in the sheaves.
Ensure that the capacity of the blocks and fittings and anchor points are suitable for the load.
When using the TIRFOR for pulling purposes it should be noted that the necessary pulling effort is not equal to the weight of the load to be moved.

Yes the shear pin will survive as you are not increasing the amount of load on it. See the little 1's in the diagram? They relate to the total capacity of the creeper winch.
Every time you add a sheave/snatch block you get double the capacity but have the same line pull on the creeper winch.

HTH

[Dr P]

so was that yes or no?

I'm still confused? lol

[killa]

Ok, Think of it as doubling the load able to be pulled not as halving the load on the unit.

Single line pull of 1.6T without sheave applies 1.6T to the Creeper winch.

Double line pull of 3.2T with a single sheave applies 1.6T to the Creeper winch.

Triple line pull of 4.8T with two sheaves applies 1.6T to the Creeper winch.

ie the more sheaves creating more lines allows a greater load to be moved, however the capacity of the winch and therefore the load at which the shear pin will break never changes.