3D Printed Block & Tackle

[Ulma Doctor]

I'm thinking the breaking point will be the base of the mounting ring.
Pretty cool Mike.
A video of destruction would be fun.

testing soon to be initiated!!!!

The pulleys are in compression and should hold hold up well.there is shearing stress from the axles on the side walls. The eyes are under tension and I'll bet they fail first.

i'll be interested in finding out how much the blocks can take.

 

[Ulma Doctor]

First test results....

i chose my first design, all PLA, to test first.

not knowing how much weight this first design would accept, left me grabbing for low hanging fruit.

using 700#paracord, i reeved the double blocks to 4:1 mechanical advantage
its all attached to a ceiling joist anchor point

i decided to lift my HF 6 ton A frame press- advertised weight is 52#

to my great surprise, the system proofed at at least 50#
i find that astounding, considering that all plastic components comprise these assemblies

secondary to them being plastic, they're not 100% plastic by volume (about 30% plastic, 70% air)

 

[Aukai]

I surmise there will be a surprise in your future

 

[RJSakowski]

When I was measuring torque on my lathe, I used a bucket of lead weights. I recast old wheel weights as 10 lb weights using old vegetable cans and weighed each one on a digital scale. I had a heavy metal bucket to hold them and could build up to a total of 110 lbs.

I am interested in finding what the failure mode will be. I have a small block and tackle that I bought many decades ago that was rated at 1,000 lbs. The sheaves were plastic and the side plates were 1/16" aluminum. There were plates between each set of sheaves as well. It had seven strands. I still have it and other than replacing the twisted strand Nylon rope with braided Nylon rope, it is original. The most that I have lifted with it was a 364 c.i. V8 engine from a '58 Buick. Kind of scary as I think back on it. It hangs out by my barn where I used it for hanging deer over many years.

 

[Ulma Doctor]

I tested the combination of my 2nd design, and the 3rd design
the second design is nearly identical, using 1/4 stainless pins instead of grade 5 bolts

i attempted to pick up a 150lb < Onan CCKM engine for the destructive test

the rigging was reeved as gun tackle.

as assumed, the design failed at approximately 80 to 90 lbs pull weight

here is the failure

the eyelet failed that Jeff and RJ had astutely predicted failure

i have already designed and printed upgraded replacement parts
no little hurdle will stop this train!

stand by for more mayhem!!!

 

[MikeWi]

no reason to print the eyes hollow though. You may as well make them solid to help with the strength. Not normally a factor, since the strength is in the 4 sides, but that's so small it would help.