Jump to content

Log in or register to remove this advert

Rigging forces


stewmo
 Share

Recommended Posts

Log in or register to remove this advert

Yes - it will be (theoretically) twice the load applied.
Two times loading only applies to a static load. When pieces are freefalling (before the slack is taken up) the forces multiply significantly. Up to 12 times the weight of the piece, although up to about 6 times is more the norm. With a good groundie letting stuff run and slowly decelerate that greatly lessens shock loading the system.

If you have a 100kg piece, rigged from below, with 1 to 2m slack, stopped dead you could create a force equivalent to 600kg on each side of the pulley, meaning 1200kg at the rigging point.[emoji15]

Something to think about.

J.
  • Like 3
Link to comment
Share on other sites

15 minutes ago, jfc said:

Two times loading only applies to a static load. When pieces are freefalling (before the slack is taken up) the forces multiply significantly. Up to 12 times the weight of the piece, although up to about 6 times is more the norm. With a good groundie letting stuff run and slowly decelerate that greatly lessens shock loading the system.

If you have a 100kg piece, rigged from below, with 1 to 2m slack, stopped dead you could create a force equivalent to 600kg on each side of the pulley, meaning 1200kg at the rigging point.emoji15.png

Something to think about.

J.

I know the math and have destroyed rigging & rigging points. Well explained 

Link to comment
Share on other sites

The 'twice the load' idea in most rigging situations is a myth. The pulley in rigging is being used for a change in direction, not to create a mechanical advantage.
 
That is the case with static and dynamic situations.
Sorry jules, you are totally wrong on this, very unusual for you to make a wildly inaccurate statement.

I decided to do a we demo.

Photo 1, drill on weighing scales. Approx 2kg.
Photo 2, drill on pulley with rope, approx 4kg.

To hold the drill steady, you have to apply a 2kg downward force on the other side to oppose the 2kg drill, total 4kg.

RIGGING POINTS EXPERIENCE DOUBLE LOADING VIA PULLEY.

J.20200826_073551.jpeg20200826_073638.jpeg
  • Like 4
Link to comment
Share on other sites

The 'twice the load' idea in most rigging situations is a myth. The pulley in rigging is being used for a change in direction, not to create a mechanical advantage.
 
That is the case with static and dynamic situations.
Got me confused with that one.

I'd say most rigging situations have two ropes leading down from the pulley, close to straight up and down? At least once the piece is getting closer to the floor.
Link to comment
Share on other sites

8 hours ago, daltontrees said:

The 'twice the load' idea in most rigging situations is a myth. The pulley in rigging is being used for a change in direction, not to create a mechanical advantage.

 

That is the case with static and dynamic situations.

I mean you're right in a sense, in that peak forces at the anchor point will likely be significantly higher than twice the load. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share


  •  

  • Featured Adverts

About

Arbtalk.co.uk is a hub for the arboriculture industry in the UK.  
If you're just starting out and you need business, equipment, tech or training support you're in the right place.  If you've done it, made it, got a van load of oily t-shirts and have decided to give something back by sharing your knowledge or wisdom,  then you're welcome too.
If you would like to contribute to making this industry more effective and safe then welcome.
Just like a living tree, it'll always be a work in progress.
Please have a look around, sign up, share and contribute the best you have.

See you inside.

The Arbtalk Team

Follow us

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.