False crotch block

[Treecutr]

I am finally going to upgrade to a block and sling ( little extra money now ) I never looked at cost of block, wow, does it matter which style I get, or will either suffice.
This style,View attachment 125578

Or this style and used with steel binerView attachment 125579

Or suggestions. I have the sling picked, thats an inexpensive investment

 

[tree md]

I use the type on the top only mine is made by CMI. I haven't used the type on the bottom (for heavy rigging) so I can't comment on it.

You need to be careful if you have it set remotely that the lock is facing away from the tree and that it does not twist around to face the tree when doing multiple rigging operations. It can work loose if there is friction from rubbing against the tree. I had this happen to me one time when I was lowering multiple limbs from the same rigging point. Luckily I was close enough to my rigging point to check the block and noticed that it had started to come unscrewed. I always keep an eye on it now, especially when I am using a remote rigging point and make sure that it does not get twisted around and rub against the tree which could cause it to work loose.

 

[flushcut]

Blocks

Use the top ones for the heavy stuff and the ones on the bottom for the light stuff. The blocks that you connect a sling directly to are much stronger and involve less gear to rig and have less fail points unlike the biner connect type. They both have uses in your arsenal of toys, redirects in your rigging, simple mechanical advantage setups, or connecting a block to chain/metal eye of some sort.

 

[pdqdl]

I recently bought that exact pulley (the little red CMI) for lighter rigging, as I figured it would be much handier to move around in the tree.

We damaged it in the first tree we put it in. We were using it to carry speedline drops out of a locust tree for some of the heavier branches because we did not want to heat up the rope or 'biners with non-rolling friction on some of the larger branches. Attached to a loopie with a steel carabiner, the bends in the side plates straightened out and pinched the pulley. It was sliding down the speedline without rolling. The cheek plates were squeezed tight against the sheave.

Nothing we cut was more than 750 lbs, and the speedline was rigged pretty loose and stretchy to soften the blow. I was really disappointed that it quit working right, especially since the pulley had a higher rating than the loopies or the carabiner. They never seemed to even get nervous by the loading, but the pulley got damaged "out of service".

It's a nice little pulley, and I am sure it will not fail until the rated load. It will quit working correctly quite a bit sooner than 7k it is rated at.

We fixed it by taking it apart, hammering out the cheek plates, and replacing the axle with a grade 8 shoulder bolt. Lubed it, and it is back in service (light duty, of course).

 

[mndlawn]

We have a couple of these, I like them.

 

[tree md]

We have a couple of these, I like them.

Hmm... I have the same block only mine has the lever to tighten the lock. Looks like they went to a twist knob. I wonder if it was because they had problems with them working loose when they got banged around. This is the type I have. Have been using these blocks for several years now. Haven't bought a new one in over two years:

 

[RacerX]

The major difference between a block and a pulley is it's ability to withstand shock loading. Here's a good explanation from Wesspur.

Choosing an Arborist Block or Pulley

There are dozens of pulleys and blocks available for the use of arborists today. However not all are created to the same specifications, and there are many applications which will put high demand on the hardware and for which only certain blocks should be used. While the terms "block" and "pulley" are largely interchangeable, we have divided them into two main groups for clarity:

* (1) Arborist Blocks
* (2) Pulleys

Arborist blocks are built to sustain shock loading a situation where the load free-falls momentarily before being caught by the block. This places far more force on the hardware than normal lowering, therefore only arborist blocks should be used in such situations. Arborist blocks have widened cheek plates to protect the rigging line from abrasion against the tree. Arborist blocks also have an upper sheave to safely attach a rigging sling.

Pulleys are excellent tools for lowering static loads. They are not manufactured to handle shock loading and for these reason are often cheaper than arborist blocks.
The relatively narrow cheek plates on a pulley may expose the rope to abrasion, so care should be taking that the line does not rub against the tree when rigging with a pulley. Most pulleys have carabiner holes in the upper body rather than an upper sheave, and so the rigging sling can not be tied directly to the pulley, and a shackle or clevis is necessary for safe operation.

Other factors to consider when choosing a block or pulley are:

Rope Diameter Capacity -- Blocks may be safely used with rope sizes up to the max. diameter capacity.
Sheave Diameter -- The wider the sheave diameter, the less it will reduce the breaking strength of the rope or sling.
Working Load Limit (WLL) -- Working Load Limit is the maximum load the block is intended to handle. The percentage of breaking strength that constitutes the WLL is different from one manufacturer to another, but is generally 20 -25%.
Breaking Strength (Brk Str) -- This is the weight at which the device fails under test conditions.
Bearing vs. Bushing Bearings are more expensive than bushings, but are more efficient and are sealed against dirt and sawdust. In practical terms, they have identical strength properties.

 

[JeffL]

I have the same large steel CMI block like posted above. I like the handle on the screw, makes tightening/loosening a little nicer as opposed to those spring pins on the aluminum blocks.

Pulleys are not meant for heavy rigging, like you posted up at the top. Get a nice whoopie, a 5/8" bull rope and a good block for the heavy stuff.