How to make your own triple blocks for less than $45

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Why a triple block? Why not a double? or a single?

Because two triple blocks working together gives you a 7:1 mechanical advantage- 5,000 lb log requires only ~720 lbs of force to lift. And you can use just 5/8″ thick rope to lift 720 lbs. A double block would only reduce the force down to 1,250 lb. But you have to double that- for each end of the log. And a single……ummmmm…..there’s no mechanical advantage to a single. Stop talking about single pulleys. On the other end, a “quadruple” block doesn’t really exist beyond huge construction cranes with wire rope- from what I’ve seen and read, anything more than three pulleys and the friction increases beyond the efficiency gained. So, a triple block it is.

First, I looked online. And found…..not quite nothing, but almost. It’s unbelievable in this age of Amazon and Ebay that you can’t find a triple block with more than 3,000 pound capacity. I suppose not many people are lifting heavy objects by hand. Ok, you can find them, but they are insanely expensive, and you need two to make a set. Not to mention you need four sets to work efficiently. Look at that price:2017-07-03-22-48-53_scrot

I mean, I guess you could climb a 30-foot lifting pole and change the block and tackle out every time you want to lift a log, but you would still need four pulleys- two on each pole- to lift each log. So, it would cost you $1,300, plus rope (about $300).

This calls for a cheaper solution:

Enter Harbor Freight:

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Of course, I’d need six of them to make a set, but that’s only $72, not $327. And some grade 8 bolts, which are easy to obtain from Fastenall.

Here’s what I came up with:20170705_204824_zpsm7auqpcv

 

 

Some more notes: I needed somewhere to tie the end of the rope- on the antique pulleys, there’s a place called a becket 70d1a3c340f41214567fd48f2725ccd9--block-and-tackle-pulley-light. I didn’t have one, so I took two extra plates from a single pulley, and put a bolt through them.

The results

I just finished lifting the biggest log yet- over 6 feet around at the base, and 50+ feet long- I figure it weighs around 6,000 lbs. The pulley held just fine- in fact, it held better than the #6 triples that I had on the opposite end. The singles (on the box) were originally rated for 3,000 lbs, so I figure the modified triple is worth at least that much, but with that huge log, probably more like 4,000 lbs.

I spent $12 per pulley x 3 pulleys = $36. The two grade 8 bolts were about $4 each. So for ~$45, I got what normally costs over $300.

 

1st layer done

This is a great feeling- The lifting poles worked, the pulleys and chain hoists worked, we figured out the kinks and got all four logs on the piers. It looks less like a grave yard with tombstones sticking up, and more like a….well, at least a perimeter with big posts sticking out of it:

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There was a little preparation required before setting the logs down on the piers:

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That’s pressure treated #2 pine – 2×12 from the local hardware store, laying on top of a shingle (90lb builder’s felt) that I sourced from the county dump (they were new in the plastic, so I scooped up a bunch).

We set the first log, then I had this nagging feeling that I was supposed to call the inspector before stacking logs. I was pretty sure he would find something wrong with the concrete. I checked the inspection schedule and it said a post-pour inspection was due, so I worked up the motivation and finally called him. He said- “No, go ahead and keep doing what you’re doing- call me when you get to the rough in.” Ok! We’re on a roll now. The rough in is when you have your electrical outlets and wires run, along with the plumbing, but you haven’t put any drywall in (yes, we will have framed walls inside the cabin, just like a normal home).

Piqued their interest

With four 30-foot lifting poles sticking up in the air, our property has become something of an attraction. Everyone from the water utility guys, to the motorcycle guy down the road slows down and takes a gander every time they drive by. The utility guys actually drove onto the property and looked over the mechanics of everything- according to one neighbor they were there for over an hour checking out the ropes, pulleys, rebar, and logs. The neighbors say this build is the “talk of the town”. Everyone is so nice and excited. Now when I’m out there working, I’ve seen several cars every day slow down to look. I’ve seen some stop, then back up, stare, then wave, and drive on slowly. A few have even pulled up, just to say hi (and get a closer look). The older guys who stop by tell me if they were 10-20 years younger, they’d be doing this too. It’s nice- the positive support is great motivation.  I usually wave and continue on with my business. The permit office lady saw me at the store last night. She said the utility guys had their doubts, but she set them straight- “Don’t worry- he’s an engineer- he’s got it all figured out.” Wellllllllllll……yeah. I’d like to think I’m more of a mathematician, you know, because that’s what my degree is in, but ok…….

A few notes about the method

If we were laying 2×4’s, it would be pretty easy- draw a center line on the 2×4, measure the distance between each piece of rebar, drill holes, place 2×4 on the pier, done. Logs are a little more hairy….

Curvy logs

They are not straight- and they may curve in more than one direction. Also there are a lot of knots on this wood. Finally, the logs have a lot of taper, which is a comparison of bottom diameter to the top diameter. The taper is a measure how much the diameter decreases from the bottom to the top.  LHBA recommends logs have a taper of less than 1 inch for every 10 feet. Our logs are about 20″ on the bottom, and 12″ at the top, and 40+ feet long. Our taper works out to be 20-12 = 8″ over 40 feet, or 2″ every 10′- double what LHBA recommends. But LHBA also recommends building with what you have. It can be done, but adds a level of complication when you try to level the structure. Probably more on that will come as we stack logs- each layer, you alternate butts and tops: where the butts are on one layer, is where the tops will be on next layer. If you “mind your levels”, i.e., measure the height at each corner as you stack, you can pick logs that match each other. The goal is less than 1/2″ height difference between all corners at the top of the walls.

Block and tackle

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I’m using antique triple blocks that weigh about 20 lbs each. I need two for each pole- one on top and one on the bottom. They are rated at I-don’t-know-but-I’m-sure-it’s-a-lot pounds. They are not made anymore because no one does it like this. The physics behind them is pretty cool. My rope is rated at about 800 lbs, but the logs weigh between 3,000 – 6,000 lbs. Using the triple blocks, I’m gaining a 7:1 advantage- 850 lbs per log, but since I’m using 2 sets of blocks- one on each pole, it’s really 850/2 = 425 lbs per log…..Well, I thought it was cool.

Other equipment

I’m also using 6,400 lb straps from Harbor Freight, a Cant Hook (or “can” hook, 🙂 ), my wife’s Landcruiser (helps center the logs over the rebar), a chain saw, sledge hammer, some trucker chains (5,400 lb) and my trusty tractor.

The process for the first course

The first course is different from all the other layers- you are putting the log down on the rebar (cemented into the piers), instead of pounding the rebar into the log (like on the rest of the courses).

I stair-stepped the rebar before putting the logs on: I cut the longest rebar to 30″, then made the one next to it 28″, then 26″, etc. This helps when lowering the log so you only have to mind getting one piece of rebar in the log at at time.

I also tried the recommended template approach- lay a strip of 1×4 on the piers and mark where the rebar is, turn the log upside down and mark the holes on the log- but they were so bumpy and long that it didn’t work. I asked around- and found a method using string- attach a string to the piers, and measure the offset of the rebar from the string, (remembering that if the rebar is 1″ to the right of the string, the hole will be drilled 1″ to the left of the center mark on the log (because the log is upside down)).  Transfer this info to the log, then drill straight down. Flip the log over (flip is a generous word), then attach to lifting straps, pull until it’s over the rebar. Then slowly lower the log until the rebar can be fed into the hole in the log (done by my wife).

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This is very exciting. All the work for the past year+ designing our plans, getting utilities installed, cutting down trees, borating them, removing branches, burning brush piles, digging holes, building forms, fixing the tractor, and on and on- got us to this point. I guess you could say we are done with phase I. Phase II will be getting the rough in complete- the goal is to get the roof on this year (by New Years Eve). Phase III will be finishing the inside. So I’ll just say thanks for coming on this journey with us. Feel free to leave comments.

Next up is the rest of the courses- these are placed on top of the log below, pilot holes drilled, then rebar is pounded through log and halfway into the log below- every two feet, and offset by one foot on alternating rows.