CMI Catalog

[TheTreeSpyder]

i recieved a CMI catalog today. As i was reading, my highlighter 'accidentally' caught these lines.

They have specialized in rescue gear since 1974, they guarantee their cams for life from wear; they will replace worn cams free of charge!


Rigging plates are designed for multiple anchor attatchments actually.

1" Loop runner slings are tested to ~6795#, making a choke grip at ~5,436#; ~ 13,590# for basket. Their bar tack stitch is stronger than the webbing!

Their Ultra 8 (deaf) surpassed 9200# pull in tests! Their hot forging for them produces 'advantageous molecular alignment' in the aircraft landing gear aluminum and then is hardcoated.

They are the recognized leader in pulley technology and have done extensive testing on strength and efficiency. In strength, the hidden axle is more a determining factor before the cheekplates.

In pulley efficiency the load bearing member on the axle is most determinant item. A bushing spreads the load out widder on axle, lasting much longer, very little wear, but presenting more friction, for less eficiency. Bearings as a choice, give the opposite properties, so are more efficient; but won't last as long.

The next determinant of pulley efficiency is Sheave diameter; because it takes leverage on the rotation on bushing/ bearing. This works for the same reason that a bigger wheelbarrel tire is more efficient for carrying loads.

i have always read and quoted that loss of efficiency per sheave was a nominal 2-4%, but these numbers here can really change some things. CMI reports their tests on typical pulleys as 91%+ for Bushings, and 95%+ for bearings; dropping to 173% on double 2" w/bushings. 1"rs come in at 85%, 133% on a double! Hmmmmmmmm but...............jumps to 215%+ on double 4"w/bearings (RP125)?...........

Wait...........where's Joe? How did they get to 100% efficiency per sheave; ................ let alone beyond? i can't be reading that write!

Has anyone ever tried their micro belay plate for low load frictin?

 

[blackwaterguide]

rigging pulleys for mechanical advantage

sure wish there were more posts on this thread.. Like the ship rigging from the days of old, there are so many tricks of the trade and such a vast array of tools. Blocks, pulleys, fiddle-block set ups, porty, etc, etc. Sure would like more info on that. GRCS is just too dang expensive, when I have been told there are old time methods with near ratio comparison.. Help this worthy thread!

 

[Joe]

Ken: you have a handle on things in this department. You know what's going on.

Joe

 

[Stumper]

Ken, If it is a 3/1 arrangement then 215% would be far short of 300%.............But that doesn't mesh with the other figures. It sounds like an error in proofing.

 

[John Paul Sanborn]

Re: rigging pulleys for mechanical advantage

Originally posted by blackwaterguide
. GRCS is just too dang expensive, when I have been told there are old time methods with near ratio comparison..

I still don't understand the differeance between th gear ratio and output MA that Greg G. talks about with his GRCS. But I would love to see a 12:1 tackle set up in just a few min.

12:1 is where Greg says The Winch output is on a single block. So I put just 100# of effort into it and lift 1200# of wood?

Anyone dealing the GRCS will work on the price for you. I lost a sale for Charly Pottorf at the WAA convention when Ariel let their show unit go for $2300.

Look at it this way, using the $2500 list price, and if you bid out at only $100 per crew hour. If the GRCS saves you just 1 hour on a normally bid job, it pays for it's self in 25 jobs.

I guarentee it will save more then that on many jobs.

I talk to guys who barely bat an eye at 1200 for a big stumping saw to save 15 min on the last cut. Why is 2500 to much for such a versitle tool?

 

[Frans]

I also talked with a guy who spent $1200. for signege on the truck, spends (I have seen him do this regularly) $60-80 at the bar, $150. on golfing fees, buys $1000. saws, BUT SAYS THE GRCS IS TOO EXPENSIVE. I just dont understand it at all.
The rigging set ups work dont get me wrong I used the fiddle block when they first came out sold by Sierra Moreno many years ago and they work great. But they are lame compared to the GRCS (or the MIGHTY HARKEN as I call it)
My friend calls it penny wise and pound foolish. The sticker cost may be unusual for some but the product is worth every penny.
So start saving
Frans

 

[TheTreeSpyder]

Originally posted by The Big Guy
.......... But I would love to see a 12:1 tackle set up in just a few min......

If you carry a 5x1 compression jig and prusik; to pull/compress into Porty's nose, bring the pull line from the compression jig under the Porty "T" balanced with minimal friction, bringing it back up to trucker's hitch or 3/1 position on pull line from compression jig; would be (3 x 5 : 1) - Friction; maybe slop down to 12:1.

Sweating in a line until the first 4 degrees of bend should give more than 12x, just not very far; compared to reeling in a GRCS over distance quickly etc., ya got the prize on that one on all counts, a heck of a tool!

But over short distance, allowing some things to leverage themself to their final needed potential can really help sometimes.
Taking JUst the 5x1 compression jig from 1st example, and sweating in final tweak on it's end as in in 2nd (without trucker's/3:1) would give even quicker, less friction, but over shorter range even; but greater than 12:1.

That pretightening, on an overhead support rig, then letting the load leverage itself the rest of the way to just equalize it's own force; which nature demands is done, wo that she takes care of that for you (so just reach to the other side of the equal sign and pull those forces to your favour). For if you just want to hold/lower/control something (not lift or steer); IMLHO you just have to match it's force, and that is what Nature does. Positions of support overhead are in the opposite direction of the downward pull, so therefore are the most automatically leveraged positions of support as the motion presses down. i think you will find that true in leveraging fibres of synthetic rope or natural wood in a hinge. So once again more leverage, but just for a short distance; if you can 'bounce' the downawrd pull off of the leveraged fibers (for less direct/more arched->leveraged).

It was an error Eric, (i called and emailed a guy there about several things last year when i though i posted this, musta gone through the time warp again!); it was a multiplied out/theoretical/non actual test deal they way that it was ex-plained to me (best as i can remember); but the potential in the system wasn't 3x or 4x ; but rather 2x; so the quoted miracle was that they not only achieved 100% efficiency, but exceeded it- Heck, gimme 2 of dose!!

So they really achieved trhe impossible breaking the Law of Conservation of Energy; in this theorectics they quoted. But the efficincy of bearings in the frictional part, then leveraged by the 4" (larger)sheave; to give great leverage x high efficiency for almost nil 'drag' is still quite a lesson and imagery to keep IMLHO.