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Thread: mechanical accuracy

  1. #21
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by roboticmehdi View Post
    I am sure I can explain myself better while actually talking to you guys. just add me and we'll arrange the call according to ours country times. im am from Azerbaijan but I live in Turkey. my skype name is: mehdi.mehdizade It's night here time to sleep, so good night everybody. see ya tomorrow
    If you can't define it in writing then you don't know what you want...

  2. #22
    Lead Engineer Cake of Doom's Avatar
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    If you want a good idea of how the ancients worked things out, you could do a lot worse than look at De Architectura Libri Decem. It's a book on Roman surveying and architectural practices circa. 20 BC.

    As the title suggests, it's ten books so you may need quite a bit of free time.

    Good luck.

  3. #23
    Quote Originally Posted by Kelly Bramble View Post
    If you can't define it in writing then you don't know what you want...
    I know what I want exactly and I explain it, but first you tell this is homework then you tell why not use modern tool then you say how you will measure without a centimeter/inch scale. You dont or dont want to understand me because this is tough question for you and for me. no question is bad.

    Quote Originally Posted by Cake of Doom View Post
    If you want a good idea of how the ancients worked things out, you could do a lot worse than look at De Architectura Libri Decem. It's a book on Roman surveying and architectural practices circa. 20 BC.

    As the title suggests, it's ten books so you may need quite a bit of free time.

    Good luck.
    I already have a look at that book, no such information can be found in that book. that book is mostly about the design of structures.

  4. #24
    Lead Engineer Cake of Doom's Avatar
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    I think the trouble you are going to get with this, is that by the time humans were making cones and cubes and cylinders and whatnot; units and systems of measurements were already in place giving an early form to national standardisation. The Greeks had a way of doing things, the Egyptians had a way and so on and so forth. Prior to to the building of complex structures and mechanisms, I'd imagine that everything was as big as needed to be based on the judgement of whomever was building it.

    If I was a teacher, this would be a purely practical lesson based on trail and error. Get some rudimentary items, sit in the garden and give it a go.

    Good luck.

  5. #25
    Quote Originally Posted by Cake of Doom View Post
    I think the trouble you are going to get with this, is that by the time humans were making cones and cubes and cylinders and whatnot; units and systems of measurements were already in place giving an early form to national standardisation. The Greeks had a way of doing things, the Egyptians had a way and so on and so forth. Prior to to the building of complex structures and mechanisms, I'd imagine that everything was as big as needed to be based on the judgement of whomever was building it.

    If I was a teacher, this would be a purely practical lesson based on trail and error. Get some rudimentary items, sit in the garden and give it a go.

    Good luck.
    But like I said my question is not about standards, that is very easy. The only unit I need for making solid object is length to tell the dimensions on cuboid or cylinder for example. And that unit as I said could be some length of fiber that I call mhd. then I tell all friends that when talking about dimensions let's talk in terms of mhds so we can understand each other.

    Actually I am thinking of going to garden and try to do what I can the problem is I don't enev know where to start. Say I have some stones around. I chip them by striking against each other and make descent kinda of knife tool( which won't be dimensionally very accurate but approximation to a knife, say with error of 2 mm). Then using this tool and my mhd scale fiber I want to make cuboid 3x5x7mhds and cylinder 5(diameter)x14(length)mhds, say my 1 mhd is close to about 1 cm( so you can have idea on how big these objects are). So, try and you fail to achieve an acceptable accuracy.

    Months ago I tried to cut a cylinder out of wax using ordinary knife and it's accuracy was not acceptable. was something like 3 mm perhaps. So doing these things by hand you can't really get good acccuracy. You may say how come sculptors do good sculptures, well sculptures are not geometrical objects they are like somebody's face or body, I mean not straight stuff but curvy and irregular stuff. There must be practical methods to obtain good acceptable accuracy and ensure it. I am looking for them. Today accurate tool creates other tools and that tool creates other tool. But in early days there accurate tool around. so they must have somehow started all this.

  6. #26
    Lead Engineer Cake of Doom's Avatar
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    It sounds like you're trying to solve a problem that has already been solved. I'm pretty sure that early man didn't care about tolerances when he was napping a piece of flint for a knife or spear head. He also wouldn't have bothered himself with how to carve out a dimensionally accurate cone.

    Looking to recreate todays accuracy using bygone methods is always going to cause you problems. Trying to eye in 0.1 mm is ridiculous.

  7. #27
    Quote Originally Posted by Cake of Doom View Post
    It sounds like you're trying to solve a problem that has already been solved. I'm pretty sure that early man didn't care about tolerances when he was napping a piece of flint for a knife or spear head. He also wouldn't have bothered himself with how to carve out a dimensionally accurate cone.

    Looking to recreate todays accuracy using bygone methods is always going to cause you problems. Trying to eye in 0.1 mm is ridiculous.
    But when they started to care, how did they do stuff? thats what I am asking.

    early man- no accuracy
    todays man- very high accuracy, sometimes even to scale of atoms !! they make sphere balls with an error of a few atoms !!

    What I am asking is, how that transition exactly happened. I know it took some time etc, but how exactly. what specificly they did.

  8. #28
    for example: what steps it takes from no accuracy at all to an accuracy with the error of no more than about 0.1mm, this is a huge number compared to sizes of atoms that todays highest precision can do.

  9. #29
    Lead Engineer Cake of Doom's Avatar
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    You have already answered your own question in a previous post: we invented better tools and developed better techniques. Each time improving on the last until we get all the way to Joseph Whitworth and Henry Maudsley and anal levels of precision. Imagine what they would do with todays methods and technology.

  10. #30
    Quote Originally Posted by Cake of Doom View Post
    You have already answered your own question in a previous post: we invented better tools and developed better techniques. Each time improving on the last until we get all the way to Joseph Whitworth and Henry Maudsley and anal levels of precision. Imagine what they would do with todays methods and technology.
    oh again you are giving just general answer. of course everybody knows we developed better tools using existing tools. but how exactly, i need more specific answer like the procedure how to do it. what are steps from no accuracy at all to about 0.1mm accuracy. if you don't know the answer then say that you don't know, you are trying to show that you the answer by bringing a very general answer and bypassing the details.

  11. #31
    If I leave you on the island, give you a cm scale only and tell you : "either make an acceptably accurate and precise 3x5x7 cuboid and a 5x14 cylinder in five days or you'll stay here forever" , would you be able to do it ? No. because you don't know how !

  12. #32
    Technical Fellow jboggs's Avatar
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    Nobody was measuring stuff just to be measuring stuff. They had to have a reason. As those reasons changed so did the measurement methods. As in most things, you can follow the money. In my opinion, the main driving force behind the development of high precision measuring methods was in the growth of mass production techniques. For example, man knew how to make guns for centuries before anyone ever thought about making all the parts EXACTLY alike so they could be interchangeable, thus enabling the mass production of guns . . . and the resulting profit. Follow the money. The same story occurs in numerous other fields ranging from farm implements to warships. To learn about the "how", look at the "why".

    Man didn't jump from measuring the speed of a ship speed by literally counting the "knots" in a trailing rope to using lasers and GPS overnight. All the developments in that field, like so many others, were so gradual and slow that the individuals involved barely even noticed the difference. Comparing the methods of today to those of decades or centuries ago requires an understanding of that evolutionary process.

    Honestly, I still have no idea why you seem so captivated by the challenge to try to recreate something that was never done in the first place, and I am rapidly losing interest.

  13. #33
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by roboticmehdi View Post
    If I leave you on the island, give you a cm scale only and tell you : "either make an acceptably accurate and precise 3x5x7 cuboid and a 5x14 cylinder in five days or you'll stay here forever" , would you be able to do it ? No. because you don't know how !
    What? I think I would be more interested on that island in making a spear, collecting water, food and finding/building shelter and none of these will require accuracy of 0.1 mm. I have no idea why I would be stuck if I could not build a cuboid..

    Perhaps I should also build a low mechanical tolerance club to defend myself against my captor..

  14. #34
    Quote Originally Posted by jboggs View Post
    Nobody was measuring stuff just to be measuring stuff. They had to have a reason. As those reasons changed so did the measurement methods. As in most things, you can follow the money. In my opinion, the main driving force behind the development of high precision measuring methods was in the growth of mass production techniques. For example, man knew how to make guns for centuries before anyone ever thought about making all the parts EXACTLY alike so they could be interchangeable, thus enabling the mass production of guns . . . and the resulting profit. Follow the money. The same story occurs in numerous other fields ranging from farm implements to warships. To learn about the "how", look at the "why".

    Man didn't jump from measuring the speed of a ship speed by literally counting the "knots" in a trailing rope to using lasers and GPS overnight. All the developments in that field, like so many others, were so gradual and slow that the individuals involved barely even noticed the difference. Comparing the methods of today to those of decades or centuries ago requires an understanding of that evolutionary process.

    Honestly, I still have no idea why you seem so captivated by the challenge to try to recreate something that was never done in the first place, and I am rapidly losing interest.


    Quote Originally Posted by Kelly Bramble View Post
    What? I think I would be more interested on that island in making a spear, collecting water, food and finding/building shelter and none of these will require accuracy of 0.1 mm. I have no idea why I would be stuck if I could not build a cuboid..

    Perhaps I should also build a low mechanical tolerance club to defend myself against my captor..


    .....

  15. #35
    Administrator Kelly Bramble's Avatar
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    If you examine manufacturing methods used by American pioneers in build log cabins, you will find they used clay/mud to seal the gaps in the wall logs. This is because building a tight tolerance fitting logs was not a reasonable or achievable task.

    Even today with all of our modern and high accuracy tools one should not specify mechanical tolerances greater than what is needed.

    As far as manufacturing your 5 x 14 cylinder I would find a sharp rock make an ax, cut down a tree and core out the log. Accuracy not required..... it just needs to work.

    If bamboo is available, cut as required and poof! done.

  16. #36
    You simply don't know the answer. Ok.

  17. #37
    Lead Engineer Cake of Doom's Avatar
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    It probably went something like: This stone is rubbish for bashing things and it hurts my hand! I wonder what happens when I tie it to the end of a stick...

    Quote Originally Posted by roboticmehdi
    oh again you are giving just general answer. of course everybody knows we developed better tools using existing tools. but how exactly, i need more specific answer like the procedure how to do it. what are steps from no accuracy at all to about 0.1mm accuracy. if you don't know the answer then say that you don't know, you are trying to show that you the answer by bringing a very general answer and bypassing the details.
    You're getting general answers because your question is basically "how did people outside of recorded history do things and why did they make it better?" which is a rubbish question.

    Quote Originally Posted by roboticmehdi
    If I leave you on the island, give you a cm scale only and tell you : "either make an acceptably accurate and precise 3x5x7 cuboid and a 5x14 cylinder in five days or you'll stay here forever" , would you be able to do it ? No. because you don't know how !
    "Acceptably accurate" is arbitrary. When working with hand tools and standard measuring devices +/-2.0 mm is deemed acceptable. Tolerances change depending on what's available to get the job done. Using rudimentary tools such as flint and bone, I'd be happy to be within +/-6.0 mm.

  18. #38
    You simply don't know the answer. Ok. I got it, Ok.

  19. #39
    why I ask you, xxxxx in first place, my bad.
    Last edited by Kelly Bramble; 10-04-2013 at 09:05 AM. Reason: Let's try a 14 day ban for that word....

  20. #40
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by roboticmehdi View Post
    You simply don't know the answer. Ok. I got it, Ok.
    One can build a rock cylinder by simply taking a large rock and tapping on it for days with smaller rocks to hollow it out. Also, one could find clay, build a fire and form a pipe from hand or around a small tree log, fire the clay and you have a pipe of some low accuracy.

    Does this hollow rock or clay pipe need to be 0.1 mm accurate in terms of form and size? NO! The ancients built what they needed for fit or function, nothing more.

    Here's what you're missing - building 3x5x7 cuboid and a 5x14 cylinder to 0.1 mm without modern tools to is just silly and not required on an island or otherwise. Your question remains academic in nature.

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