This Amazing 70 Year Old Calculating Machine

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They've done it again! After the success  of the model one Curta calculator,   first launched in 1949. This  marvelous device has been updated   to the new model 2. With expanded  calculating ability up to 11 digits.   A delight to engineers, scientists, pilots and  rally car drivers. Everyone loves their Curta. I've wanted to see one of these for many years.  This is an original 1954 Curta calculator.   Unfortunately it's broken. The internal mechanism  is all jammed up. I can't move the main rotating   handle on the top simply doesn't want to budge,  and I don't want to force it. Because the last   thing I want to do is cause any more problems.  Some of the input sliders on the side do still   work. But a number of them are also jammed. So I'm  going to have to fix this, and the way this came   about was I was contacted by Edd from Historic  Tech in the UK. And he said he had a damaged   Curta and he asked if I would be able to fix this  for him. Of course I immediately said Yes! I found   out about them many years ago from watching  YouTube, and I was intrigued, not just by the   device itself, I was impressed by seeing just how  prized these are by people who own them. Such as   Techmoan: "the item I'm going to show you today is  one of the most precious things in my collection."   "A lot of people will know what this is already"  And Adam Savage: "ah this is one of my favorite   objects in the world, a Curta computer." "there  are over 600 separate parts inside this." And now   that I get to see one, I can start to appreciate  why. It feels so good to hold in the hand, and I   can't wait to do some calculations. But before I  can do that I'm going to have to fix it. On the   bottom there are two obvious screws and removing  them allows the bottom casing to easily slide off. Giving us our first glimpse of  the amazing engineering inside.   It seems to be made mostly of steel. But it looks  like there's also some brass and maybe even some   aluminum. During this process I'm sticking  to the rule of doing no harm. I'd rather not   be able to fix this, than do something that  causes more problems. I mean I usually try to   follow this sort of rule with my own stuff. But  it's never been more important than with this.   The insides look nice and clean. The mechanism is  already looking amazing, and I'm not even into the   main section yet. The Curta is the invention of  Curt Herzstark. He started drawing up plans for   this design before World War II. Which he then had  to put on hold when he was imprisoned during the   war. For being of a particular ethnicity. Despite  all this he didn't give up. In fact designing this   while in prison helped keep him alive. When he  was finally liberated from prison by the Allies,   he then went on to start a company. Which  then manufactured these for the next 20 years.   I'm pleased to see that the serial number  on the case matches the serial number on the   internal mechanism. This looks like a complete  original unit. But to fix this I'm going to   have to disassemble the top section. This is  where things start to get a little bit tricky.   The next step is to remove the top handle.  Which involves removing a precariously placed   pin. And to do this I'm going to have  to use a radical dislocation method. In   other words I'm going to have to bang it out  with a hammer, in order to push the pin out. Until I was able to dislodge the pin  enough to get some pliers onto it.   I still didn't want to move, but  eventually I got it to pop out. The handle then comes off relatively easily,  showing the next challenge. There's a   spring-loaded locking ring that has to be removed  next. This usually requires a special tool to   open the locking ring and lift it out, which  I don't have. But with a bit of improvisation,   I found a small blunt pair of scissors is able to  hold the spring open just enough to lift it out.   I can now see the first clue as to what  may have happened to this calculator.   The shaft on the top appears bent,  and this is a thick steel shaft,   and not easy to bend. This must have  had quite some impact to cause this. The next step is more radical dislocation.  According to the disassembly instructions,   the top shaft has to be hammered until the  brass ring around the shaft is removed,   and reveal the insides. The top indicator dial  also has its own set of complex gears to drive   the output numbers. I'm pleased to see the top  gears are all moving freely. As is the clearing   ring that resets the top dial to all zeros.  But I've spotted something else that doesn't   look correct in this Curta. This pin in the top is  called the 'carriage lock pin' and it appears to   be bent very badly. This is a very solid piece of  steel, and another indication of a severe impact.   With the top now removed, there are three  more screws that have been revealed. And   these are holding the third and final piece of the  casing. This final piece slides off fairly easily,   and there it is the internals are revealed.   Somehow this fantastic set of gears and  levers is able to do addition and subtraction,   and multiplication and division. On numbers  up to 11 digits long. Including floating point   decimals. And there's even a procedure to find  square roots using this thing. I'm slowly going   through and very carefully checking each part  in turn. I'm noticing that almost everything   seems stuck. But carefully working each part  is beginning to bring some movement back. I'm really pleased to see that  with every small movement,   I'm slowly bringing life back to this mechanism. I'm going to speculate that this was maybe dropped   a really long time ago and then  put away in storage and just left. I'm going to try turning the main shaft  now and even though it's still bent,   it does seem to turn and it even sounds good. it's time to do the first test and for this I'm  just going to do a partial reassembly. If I enter   some numbers into the sliders on the side and turn  the handle once. We can see that the numbers are   added to the output register on the top. I can  also do subtraction by lifting the shaft into the   negative position. Each rotation then subtracts  the numbers on the side from the total number   on the top dial. The way this subtraction works is  called a nines complement addition. Which is a way   of using the addition of complementary numbers  to do a subtraction. But during this testing I   found there is a problem. Here the second register  normally shows how many turns of the handle you've   done. It's also used in multiplication to let you  know you're getting the right result. And it's   particularly important for division, because this  is where the answer is shown. Looking very closely   inside, I can see that the gear for this section  is indeed sitting higher than its neighbors.   If I just very gently move it with a screwdriver,  I'm finding that it was indeed stuck.   Looking again at the mechanism, I can  see that each gear has a carry lever.   This is the part that actually moves the  gear up and down when it's time to carry   the 10. And the carry lever on this first  gear looks like it's bent and unable to move   this gear. So I'm going to very carefully  remove the entire carry lever assembly.   I have to be really careful because there's  a number of very small parts here. Including   a tiny rectangular spring. And with the carry  lever out, I'm just going to start bending it.   It's not too hard and I did feel it bend a little  bit. Let's put it back and see how that went. It's   not quite bent far enough. But it's pretty  close, and the lever does seem to be moving   the gear again. It's time for a proper test and  I'm going to do an almost complete reassembly. I'm now going to do a final test by doing a  division. I'm going to divide 1 million three   hundred and sixteen thousand one hundred and  fifty four by Thirty one thousand three hundred   and thirty seven. First input one three one six  one five four into the side, and enter that into   the top dial. I now have to use this lever on the  side to reverse the counts. I also have to remove   that initial one from the first turn and bring  it back to zero. I now need to change the dial   on the side to the second number that I want  to divide by. In this case 31337. We should   now be set up to do a division. I have to lift  the shaft handle into the subtraction position   and begin rotating. If I don't know how many  digits the final result is, for example I think   it might be four digits long. Then I set the digit  counter to four digits. But when I rotate the   handle I'll get nines across the output register.  That means that digit is a zero. I have to reverse   this by switching the shaft back to addition and  reversing that initial turn. Since I already know   the result is two digits long, I'm switching  to the second digit position. Putting the   shaft handle into the subtraction again and begin  rotating. Once I get to the fifth turn I again see   the nines on the output dial. Do I push the shaft  back down to addition and reverse that last turn. Then switch the dial to digit one and start  turning again. Get to the third turn and   reverse that. This will then give the result  of the division on the second output register. One million three hundred and sixteen thousand  one hundred and fifty four divided by Thirty one   thousand three hundred and thirty seven equals  42. I finally have the answer that I've been   looking for. Thank you for joining me on  this journey inside the Curta calculator.   I'm really pleased I was able to get it  calculating again. I still need to get some proper   oil to finish the job. There are certain parts in  here that need tiny amounts of the correct oil. But for now thank you for watching. I  hope you enjoyed this experience with   this amazing little machine. I'll be  getting back to some slightly more   modern tech in future videos. So I hope you  stick around for that, and I'll see you then.
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Channel: Janus Cycle
Views: 31,124
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Length: 12min 5sec (725 seconds)
Published: Thu Aug 03 2023
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