CMI RP145 Arborist Block

The CMI RP145 arborist block is a rigging block made to hang from a sling and redirect a lowering line on tree removals. It replaces a natural crotch with a turning sheave, which saves the rope, protects the tree, and gives the ground crew smoother control.

Putting the RP145 to work

Set the block on a sling above the piece you are removing, run the rigging line through the sheave, and take it down to a lowering device at the base. With the block carrying the redirect, the ground worker controls the descent with the device instead of fighting crotch friction.

The anchor and block take roughly twice the load on the rope because the line pulls from both sides. Size slings and anchors to that, and choose a rope that fits the sheave as listed by CMI. Check CMI's ratings for this model before you size it to a job.

Placement matters as much as the block itself. Hang it above the piece and as close to the trunk as the work allows, so the load hangs in line with the stem and the anchor is not levered sideways.

Checks before each job

Look for cracks, bent side plates, a loose axle, and grooves worn into the sheave. Spin the sheave by hand and make sure it runs smoothly. Retire a block that has been dropped from height or shock loaded beyond its rating. Compare other blocks in our rigging blocks.

Rigging forces are dynamic and can be several times the weight of the piece. Follow the manufacturer's ratings and ANSI Z133, inspect every component before the job, and keep rigging work to trained crews.