Cable Math
Friday, August 18th, 2023 12:29 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
snoozefestaudio
70F and sunny with light breezes this morning.
I successfully made it all five days this week, getting my feet on the floor by 11AM, out the door with the pets by 11:20, and back to bed before 4AM.
Above, you can see the blue-green of the preservative being more noticeable in the lighter parts of the wood grain on the second coat.
I did not flip it over today, but rather, gave the same side a second coat...
This is because the sheet is bowing, and I want to give it another 24 hours to flatten out, if possible.
But tomorrow I will flip it and get the second coat on, what will be the topside.
I'll also run to Home Depot for the paint. And I think I'll grab some new PVC and fittings for counterweights.
I was still confused this morning by the trigonometry problem of how adding a second eye bolt would effect the drop distance of a single counterweight, but I think I've figured it out.
I had to remember that the way it was rigged, the line went to a pulley on the counterweight, and back up to the unistrut, meaning that if the counterweight droped six feet, it was using up 12 feet of line.
The single pulley on HD1.0 was 8 feet from the unistrut... taking up 16 feet of line, which reduced to six feet of line in the fully opened position. It therefore lost 10 feet of line, which was easily taken up by the counterweight.
So, in a two eye system, both 8 feet away from the unistrut... in the closed position they would take up 32 feet of line.
In the open position they'd take up only 12 feet of line... losing 20 feet of slack.
Since a single counterweight can only take up 12 feet of slack, that leaves 8 feet unaccounted for.
Or, in other words, it would need to drop four more feet to fully open the door... and we can't do that!
HOWEVER...
The solution is to have two counterweights!
Instead of one big counterweight made from 4" PVC, I need to have two weights made from, like, 3" PVC.
Each has it's own pulley, and they hang side by side.
So, if I have to make up for 20 feet of slack, it means that each of the two counterweights only has to drop 5 feet!
Okay!
Oh, and as for waterproofing the eye bolt connections, the solution to that is teflon paste!
Teflon paste, used in plumbing all the time, is eternal!
I just put teflon paste where the shoulders meet the flat washers, and under the washers where they meet the door.
Totally waterproof... won't react with the paint... and won't degrade with temperature changes or UV exposure.
So, I thought about the dual counterweights tonight and then drew a diagram when I got home...
It looks pretty wacky, but I like it!
So let's slap some labels on everything and talk about it!..
So, we have System A, on the left, and System B, on the right... each designed to balance the weight of half the door.
The door is four feet wide. Pulley A is one foot in from the left. Pulley B is one foot in from the right... so that each one is centered in a two-foot section of the width.
The mirror image riggings are identical to the original rigging of HD1.0... which gave a single counterweight the mechanical advantage of four pulleys... and centered the load at one point on the door.
So in this dual system, we are not doubling the mechanical advantage... because we now have two focal points, and the weights are half of what the original weight was.
It will take exactly the same amount of work to lift this door as it did to lift HD1.0!
The only difference is that the load will be spread out more evenly across the plywood.
So... if we're doubling anything... it's the strength of the plywood.
Now, it's worth noting here, that HD1.0 worked GREAT, when that plywood was new!
And if I'd been more careful to waterproof the hardware penetrations, it would probably have lasted ten or twenty years.
So I probably don't NEED to be using this dual system for HD2.0...
But I'm deliberately over-engineering this one, to make it as long lasting as possible!
But by far... the waterproofing measures I'm taking for 2.0 are what will make or break it, in terms of longevity.
Shoulder bolts, teflon paste, enamel paint... but if water does get through all those defenses... it's soaked in microbe killing, copper infused, preservative.
As long as it doesn't rot... it will be fine.
And the dual rigging lowers the mechanical stress that might eventually tear it apart.
So the only thing to worry about should be... my fat ass, or somebody elses, standing on it and cracking it!
Lastly tonight... I did publish, Coffeehouse Boyfriend last night, with, Melancholy Moon as the single.
In 24 hours, that single's gotten two partial plays, and two immediate skips.
But I absolutely LOVE how BandCamp is putting all the pressure on ME, to promote this myself... to my friends!
Like, this is what artists are up against in 2023... "You do everything yourself, and we'll host the music online and take a cut!.. Now get cracking!.. we're not making any money yet!"
I will embed below, and it IS free to play the song or the whole album, just like it is, and was, on SoundCloud.
But there is the option here to buy the song for a dollar, or the album for three dollars, here... which I, PERSONALLY AM NOT ASKING OR EXPECTING ANYBODY TO DO!
I got into big trouble here, a couple weeks ago, just mentioning in this blog that I could see some plays on SoundCloud that had to have come from readers... and immediately the traffic went to zero!
And I know why!..
Because you read this blog to get a story about a guy... and it's NOT cool, if that guy starts using the blog to promote his music!
I get that!
I apologize for that!
And I do NOT expect anybody to play the embed below, or, God forbid, give me any money!
I only embed this stuff because this IS a journal... and I want to be able to come back to this entry myself, and hit the link to the other thing I was doing online back on that day, or in that time period.
Okay, with that... it's been a long week, and I have a big mission to Home Depot tomorrow, to fetch hardware and PVC fittings for HD2.0.
So... talk to you tomorrow!
°¦}
