Introduction: Make a Light-duty Block and Tackle
Needing a block and tackle for my kid’s tree fort I didn’t want to go overboard with some store bought mechanism although with a bit of shopping you can find them fairly cheap. All I needed was something light duty and simple – I did try to make a double pulley similar to my antique set, but I had problems getting the double side-by-side pulley to sit perfectly balanced. Then I had the idea to keep it really simple with all the pulleys in one plane so this is what I came up with. This is not a complicated project by any means, I was surprised at how easy it was to make and can easily be manipulated (bigger/smaller pulleys, heavy duty materials, etc.) to make something really interesting. It works well and holds more weight than you would need – I used 1/16” aluminum which has a tensile strength far higher than anything my kids will haul and the #8 bolts will ensure that their arms or interest give out long before the B&T does!
Materials are plywood, sheet aluminum, nuts and bolts, and a couple inches of half inch straight copper tubing. I used simple hand tools and an electric drill and had them put together in about 4 hours worth of time.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Pulleys and Plates
First thing is the pulleys - depending on what kind of system you want (2/1 or 3/1 or 4/1 . . .) you need that amount of pulleys. I decided that my plates were long enough to make a four-to-one system so I made four - this means that hauling a 100 pound load will actually be 25 pounds on the rope that I am pulling. Pretty cool. Yes, I am easily impressed. I used a hole saw to cut out my discs (keep in mind they can't be the same size or you will have interferance with the rope as they run around the pulleys) and then used the drill as a lathe with a round or rat-tail file to form the groove for the rope. A bolt through the disc can be chucked in your drill to hold it. It took me about 5 minutes for each disc. The aluminum plate I cut out from some angle plates I had, labeling them 1 and 2 as to not confuse them. The last shot shows both discs with the rope around them - I grooved it deep enough that 3/4 of the rope sits below the outside edge of the pulley. They could be deeper if you are a belt and suspenders type person.
Step 2: Drilling the Plates
There are two sets of two plates - one has 4 holes and the other 3. The most important aspect is getting the holes in both plates to be aligned to each other. This is pretty easy as all you have to do is clamp them together and drill the pilot holes through both at the same time. Then, as you step drill each one separately to size, your original holes will all remain aligned. In the photo you can see my scratch line with the punch marks, with the second and third photo showing the finished holes. I also rounded the ends of the plates to make it look nicer.
Step 3: Bolting It Together
The first photo shows how the the plates and pulleys are arranged without the other plate. You can also see the short sections of copper pipe - I used those instead of having the carabiners resting on the threads of the bolts and does look nicer. The second photo shows it put together - what you can't see is that I have a washer on the bolts running through the pulleys that are sandwiched between the pulley and the plate. This is to keep so much of the pulley from rubbing on the plate, creating too much friction. I used an old trick or the "cheap man's locknut" as I call them - the third photo shows two nuts, the one on the right has been hit one time (forcefully but not too much) to deform it. This will make it grip the threads of the bolt pretty well, just like a lock nut. Or you could use a split washer too, in any case you need something to keep it on the bolt - it spins enough with the pulley that it won't take long to unthread itself. Last shot is another look at the B&T. It works really well and I am pretty happy with it.