And finally, what knot did you use to secure the carabiner into the loop?
Sent from my iPhone
> On Dec 9, 2019, at 7:56 AM, Gedas <w8bya@mchsi.com> wrote:
>
> Grant TU for the very useful write-up and description. Yesterday before solid
> rain and below freezing temps set in today my wife and I managed to put
> everything in place and raised up both towers. Each now has my 2x4 with
> pulleys arrangement attached & threaded and I really like the way it turned
> out. Running up the loop with attached SS Carabiner clips up & down worked
> out so well.
>
> I provided a couple of URL's showing the 99% finished setup. Images do not
> show the SS pulleys attached to those clips. The images may look a little
> confusing but I tilt over my 70' Universal towers (with 22' mast) using a
> system I designed and have been using for over 35 years. The black poles are
> a pair of 6"x6"x18' PT timbers bolted together and set into 7' deep concrete
> (same as the HD tower bases). A double pulley system and geared winch allows
> me to tilt up & down the towers in about 10 minutes since I do not climb.
>
> The images show I used a simple square knot to join the rope ends but these
> will be replaced with a double fisherman's knot in the next day or so. Thank
> you again to everyone who helped out and provided input.
>
> https://drive.google.com/open?id=1VLLuLA9e7lridHe3BgwfX34fbRPZeKti
>
> https://drive.google.com/open?id=12aRNdm-8hnw31shSPDEoO-Lz7QGm4J-R
>
> https://drive.google.com/open?id=1hn2NeCGb5lYBqMVq4dqbvomNpWM0836T
>
> Gedas, W8BYA
>
> Gallery at http://w8bya.com
> Light travels faster than sound....
> This is why some people appear bright until you hear them speak.
>
>> On 12/1/2019 11:40 PM, Grant Saviers wrote:
>> I looked at your 2x4's with pulleys jpgs. If rope strength is a concern,
>> then consider that going around a sheave (pulley) significantly compromises
>> strength in two ways. I thought a comment would be appropriate given the
>> discussion about knot strength.
>>
>> The rope fibers are compressed inside and stretched outside in the sheave
>> wrap so the strength can be degraded 50% or more. The pulleys you appear
>> have a tiny radius. Repeated passage is cumulative for damage. Check rope
>> specs for the recommended sizes.
>> https://www.mazzellacompanies.com/portals/0/Images/Page206_3.png (might be
>> for wire rope, same problem, bigger loads and life safety = bigger concern)
>>
>> The second problem is there is a lot of friction in the pulleys. I've seen
>> tests for hardware store ones where the output tension is only half of the
>> input tension. I use a good sailing block, the best have polymer ball
>> bearings. It's amazing the difference low friction makes.
>>
>> Sailboat pulleys are also made to minimize chafe, so if the load moves or
>> the rope stretches in the wind you will be much happier in the long run
>> spending $20 for the good ones. I figure a tower climb costs much more than
>> $20 if the rope breaks or the pulley fails. Harken, Lewmar, Ronstan, are
>> all great. Here is the one I am currently using
>> https://www.amazon.com/Ronstan-Ball-Bearing-Orbit-Block/dp/B002NSSCF2/ref=sr_1_6?dchild=1&hvadid=3527191554&hvbmt=bp&hvdev=c&hvqmt=p&keywords=ronstan&qid=1575260910&sr=8-6
>>
>>
>> Also, I went back to your original post to understand the goal. You mention
>> 30# load. The actual load in a rope pulled from the side is greatly
>> affected by the angle the rope makes with the a line between the ends. i.e.
>> at halfway actual rope tension is load/sine(angle). That means at zero
>> degrees the tension multiplier is infinite for a load 50% between the
>> support points. Obviously, that never happens since the rope stretches or
>> something fails. When your hoist point gets to the top pulley then that
>> pulley will take all the load and the other line part can be slack, so not a
>> problem. Be aware that when hoisting,there might be a larger tension then
>> expected halfway up if the hoist is a tight loop. And the loop force on the
>> supports is twice the tension. So a better solution is to put a lot of slack
>> in the hoist loop. I always use a loop through my permanent sailboat blocks
>> in trees, just to never lose an end, but they have a lot of slack, also to
>> reach the antenna on the g
round partway out.
>>
>> Grant KZ1W
>>
>>
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