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Hi, everyone! Welcome to my first instructable! I hope it will be helpful to anyone who wants to make an automatic door closer with this design, using sheaves and internal counterweight. I'd like to apologize for any grammar or english errors, because i'm brazilian and i am also trying to learn english while publishing some few ideas that i was able to put in practice!

Well, let's go to the instructable:

Bill of Materials:

Well, I didn't take any picture of all the material that I used in this instructable, but here is a list of the most important that were used:

   -> 0,5m of " U" Beam (35x10mm) for office divider panels;
   -> Two 50A1 sheaves (Diameter 50, A1 channel);
   -> One 60A1 sheave (Diameter 60, A1 channel);
   -> 2 pieces of M8x50 DIN933 screws;
   -> 14 pieces of M8 DIN934 nuts;
   -> 2 pieces of M8 DIN125A washers;
   -> 1 piece of M8x95mm cut of threaded rod;
   -> 2m of wire/rope. I used clothes line rope, here;
   -> 6 sets of 6mm steel screws for concrete fixturing;
   -> One bottle for counterweight.
   -> 6 pieces of aluminium rivets 3,2x12,7mm

Materials left to get other level of finishing:
   -> 700mm of sewer PVC pipe of 75mm diameter;
   -> One cap of 75mm PVC sewer pipe.

Tooling:

Tools that I needed to make this instructable:

   -> Power Drill
   -> 8mm concrete drill bit
   -> 3,5mm HSS drill bit
   -> Angle grinder for cutting the "U" beams;
   -> Hand riveter for 3,2mm rivets;

Step 1: Making the sheave supports

Cut two U beams with 120mm length and one U beam with 195mm length with the angle grinder.

For the two "L" supports, cut only the beam laps at 60mm of the border. This will allow you to bend the "U" channel easily, and precisely, using your hands. The drawing will give you the dimensions of this part that I made. Do the same for the "U" support with the 195mm piece of "U" channel. Forget about the 45º cut that the drawing represents, i just messed up one part when I made that because i didn't realize that the beam was so easy to bend!

Before bending the parts, make sure you've drilled the fixture holes of 6 and 8mm of diameter.

After bending, you will need to place two rivets on the laps of the "U" channel, to make sure it will not unbend with the counterweight and the forces involved on the operation of the assembly.
<p>whoa, what a list of mats. I did this with simple rolls that are connected to ear-and-hooks from a hardware-store. With these the rolls always fall into place. I used paracord as my ropes. Additionally i weighted it to a minimum so that my cat still can open my door.</p>
<p>Hi Luziviech, can you send me images of what you did and the materials you used please? It was the fact that you mentioned your cat that caught my attention because I need a way of letting my cat into the bedroom while allowing the door to close behind him when he does. The only problem I'm struggling with is that once it closes the poor thing can't open the door from the inside to go back out again! I need to find a counterweight system that allows the door to open again with minimal pressure - the cat DOES know he has to try and pry the door open towards him (he's so funny, trying to claw into the groove of the door and trying to bring it back but it is too heavy for him!) - so I need to help him out so when he does apply some force to it, the door starts to open and he can then assist it and dash through. once he's through, the door would close again, since there is the counterweight. Any ideas how I can do this are appreciated! Thanks</p>
Don't remember having such photos anymore, but your construction is pretty stiff. if you use rolls with an eye and hooks to the wall, the wheels move the way the tension of the rope force them to - i mean, the whole thing gets smoothier and you don't need three, but two rolls to build. And to find out what your capable to pry, just animate yor cat to keep trying by prying while you open the bottle and pour more and more liquid out until she can open the door. If she has no chance anyways, then the door must be to heavy and it might help to give some oil to the livers (dunno bout your door, but mine is from quite light wood).<br>But in any case, you still could add a small spring to that groove, allowing both closing the door and enlarging the groove for your cat, i guess.
<p>Hi Luziviech. The counterweight door on this page is not mine, so I don't know which construction you're calling &quot;pretty stiff&quot; :) (though they guy did at least share his contraption and put it out there, which is more than can be said for the both of us, at least when it comes to opening and closing a door with a counterweight!) </p><p>Still, thanks for your advice and will keep it in mind, together with the advice you gave 3dfernando.</p><p>Unfortunately, my door is a bit heavier - it is an old wooden door but I've oiled the hinges so it does open and close quite smoothly. The only problem is if the door actually closes shut, though I could probably find a simple way of keeping the latch bolt of the door knob (simply jamming it with a small piece of wood comes to mind). The counterweight should technically keep the door closed unless it is pushed by the cat or a person.</p><p>When I'll finally get down to doing it, I'll try remember taking photos of how I did it and posting them up :)</p>
<p>Well, done - this reminds me on a system I had done to open louvers on top of the front door using a multi-pulley system - I did not use any counterweight though, but what was cool about it was that I managed to make a system that opened and closed the two louvers simultaneously with the rope hanging only from one side. It was quite practical. Pity I never took photos of the system (it was already difficult to actually do the system over the front door entrance, let alone take any photos!) Unfortunately we sold the house and the new owners remodelled the front entrance and took everything down before it occurred to me that I should have taken photos! Pity! It might have given somebody some ideas for their own homes and even improve on my system - I have similar window louvers in my new house but they do not open like normal windows - it is a semicircle window that can be completely unattached and does not have hinges keeping it in place, so that's one added complication! Anyway. Good luck with any new projects :) It is always nice to DIY, use your hands and mind to do something without simply going to some store and buying some gadget - especially if to do the job you recycle stuff! :)</p>
Hi Fernando and thanks for this! <br>Here's a more rational design (I think): <br>Skip the Return sheave and simply twist the Couterweight sheave 90 degrees to the right and stick it to the other wall. And shorten the string of course. <br>Thoughts? <br>Again, thank you!
me and my brother built something similar a few years ago, we had to close the door the opposite way, used fishing line for a bungy effect so when the bottle reaches its lowest point the line flexes a little and doesnt send it crashing into the wall. we used a mountain dew bottle filled with pennies and drilled a hole through the top of the bottle instead of just tying it so it would come down straight, room air pressure [whether the window was open or not] was an obstacle because if the window was opened the door would slam so we had to have a small spring between the door and the jamb so it wouldnt slam
Good job! Just a suggestion, could you describe the inverting sheave a little bit more in detail?
Thank you! Of course, here it is below: <br> <br>Let's suppose that you didn't have put that sheave. Then the rope would have to connect directly to the &quot;return sheave&quot;, and it would cause it to face towards the wall opposed to the door. <br>This way, when the weight falls down, it will generate a tension force on the rope that would, in the point where it is fixed in the door, point towards the inside of the room. Then it would open the door, not close it! And my mechanism would so be called &quot;Automtic door opener&quot;, hehehe! <br> <br>So I had to put that &quot;inverting sheave&quot;, that will make the rope tension force point towards the outside of the room, in a way that it closes the door. <br> <br>Let's say that you had put the mechanism on the other room, then it would not be necessary, because the tension force is already pointing towards the closing movement of the door. <br> <br>Hope this explanation helped you!
i've done that with a few doors i built in Afghanistan, except waaaay simpler, just a couple of U nails and some 550 cord and some water bottles. is simple and it works, just dont get your hand caught in it it doesnt feel too great
I did the same in my dorm room at university. Epic. :)
Can you post another video. i cant see whats going on here. <br>
Very nice. Simple and effective design.
Nice work... <br> <br>Am i the only one who instantly thought of ferris bueller's day off?
This is a nice complication, and very impressively executed (great instructable!! :-) would be simpler with the rope attached above the door, and a pulley/sheave on the top edge of the door, with the weight hanging down the back of the door. <br> <br>This way does allow you to put the weight in the corner and more out of the way however. <br> <br>Good work, <br> <br>Giles
The weight next to the door means it will knock against it.
I know what you mean, however when I tried it, the weight rarely hit the back of the door. That does not seem to be intuitive (according to my level of physics anyway), but you had to push the door really hard/quickly in order to make the weight hit the door. <br> <br>However I would agree that the solution here, although more complicated, is a much neater way of closing the door.
We used to do that for all of our doors when I was in Iraq to keep our cool air in, but yours works and looks much nicer. We would just drive a nail halfway in, and then bend it into a hook. Also, I think we had our water bottles on the other side of the door so they would close all the way, but they tended to make the door bang shut. Good work!
Cool, I use one of those stretchy curtain cables, it's like a long spring in a white sleeve, a screw hook in the door frame by the hinge and a screw eye in the door on the handle side, both at the top of the door it does close a bit quick and the girlfriends dog gets stressed when it's head gets stuck :/
I made a similar one years ago using fishing line, pulleys from an old radio (the tuning dial mechanism) and two &quot;D&quot; size batteries as the weight. Three would have worked better, and when someone commented that it did'nt work very well, I said it was because the batteries were flat. ;-)
From the photo it seems that it would work well until the last few cm because of the angle and does not hold the door firmly closed. How did you get that to work?
I'd attach a short stub out from the door so that the string pulls at the same angle the whole time. Could do away with the left-most pulley too.
Great !&hellip; <br>A nice way to remember us that older easy mechanisms can replace sophisticated expensive engineering &hellip; <br>However, when the soda bottle has been drunken, what happens ?&hellip; <br>LOL &hellip;
Very nice
Bom trabalho! Exatamente o dia de hoje minha esposa estaba falando pra mim sobre como manter a porta da habitacao das minhas filhas fechada pra evitar o ingreso dos mosquitos, eu pensei en colocar um fecha-portas hidraulico que tenho por algum lugar da minha casa.. ha ha! pero agora vou fazer uso da sua ideia... Obrigado desde Asuncion, Paraguay, South America. <br> <br>Good work! Just today my wife was talking to me, about keeping the door closed in my daughters' room to avoid mosquitoes, I thought putting an hydraulic door closer that I have somewhere in my house .. ha ha! But now I'll make use of your idea ... Thanks from Asuncion, Paraguay, South America.
Well done, i need one of this thing but it is hard to find . <br> <br>Muito bom, tava querendo um aqui destes que se v&ecirc; em escrit&oacute;rio, nunca pensei que poderia ser feito assim, valeu.
Looked lik a door opener to me until I watched the video ^^
Very nice, I had a similar pulley system on my bedroom door growing up.
Thanks for sharing this project. One question: where do you get the &quot;sheaves&quot;. Is this some part of a machine or can you buy them &quot;of the shelf&quot;?
Thanks for the comment! <br>I bought them on a hardware store, here in brazil, it was very cheap (about $5 each). These are single channel pulleys for &quot;V&quot; belts, I think it is easier to get there in USA than here!
Would not the project work better if the door swung the other direction? However the demonstration of the theory is marvelous.
Thanks for the comment! Surely it would be easier if it was on the other side, but in my case it was impossible because I couldn`t invert the door. Also, this way the counterweight stays hidden behind the door while it is being opened, preventing accidents while it`s moving.

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