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Thread: 1944! Colchester lathe coversion

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    1944! Colchester lathe coversion

    Hi,

    I've just bought 1944 Colchester lathe (a "pig in a poke", £50 on eBay UK, 113 euros transport to France where I live, it has very little wear for a sixty year old machine!), my intention is to"CNC" it. It came without change wheels, intend to use the Electronic Lead Screw being developed on the ELS yahoo group. The ELS will allow threading and taper turning, and for "real" CNC, I'll go over to EMC and Linux, this also gives me time to learn G code ans stuff! Mechanically I can cope with this project, but I need help with the maths involved. Thirty five years ago, when training as a mechanic, I learnt to check bearing preload on differentials (third members for our American cousins) using a piece of string and a spring balance. I've only ever done this once in my life, as fate has it I've never had to rebuild a diff since! Today I wound a piece of string around a 25mm diameter part of the cross slide screw, pulled it with a spring balance and obtained a read out of 800grams. Can anybody out there help me with the calcuations to transform this into stepper motor torque.

    Matthew TINKER (Tinker is my real name!)

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    No. I think it should be put on a pedestal with a sign underneath reading;

    "The Way Things Were. Oh For The Good Old Days".

    CNCing it is nothing less than sacrilege; like when people take 500 year old mansions, gut them and install all modern conveniences. Have you no appreciation of the finer things in life you, you, Philistine!!!!!! Splutter, spluttter.



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    I never said that I was making an ireversable change to a museum piece! I have no intentions of mutilating it! It's missing too much to restore, besides I appreciate the quality of the machine! It's easy to jude without knowing!

    Matthew


    Quote Originally Posted by Geof View Post
    No. I think it should be put on a pedestal with a sign underneath reading;

    "The Way Things Were. Oh For The Good Old Days".

    CNCing it is nothing less than sacrilege; like when people take 500 year old mansions, gut them and install all modern conveniences. Have you no appreciation of the finer things in life you, you, Philistine!!!!!! Splutter, spluttter.




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    I'm joking for goodness sake!!!!

    But I bet I will get support from some of the other old fogies .



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    Other antiquities!

    Goef

    Good!

    I also have in my workshop, an 1841 folding machine, on a pedistal "cos I use it lots"! It's a French made machine, that I saved from the slow boat to China. It was made the year after the French passed the law that obliged the use of the metric system, fourty years after it's introduction! It is beautiful to use, I can fold 2.05m lengths of 2mm steel with it by hand. I get a kick out of using it on stainless and alluminium, metals that didn't exist when it was made! It's quite an attraction in it's original drippy black paint, I just cleaned it oiled it adujusted it and use it!

    Respectfully, Matthew

    P.S. an one got a solution for my maths problem!



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    Quote Originally Posted by mattinker View Post

    P.S. an one got a solution for my maths problem!
    I would think a 1944 Colchester at least deserves servo's
    I would expect it is on the beefy side and not exactly a 'table-top'

    For Break-away torque, the method you describe, or similar would work, you can also get an idea using sizing programs like Kollmorgen etc, http://kmtg.kollmorgen.com/motioneering/app_engine/ . which introduce the inertia motor to load aspect (Free).
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Quote Originally Posted by mattinker View Post
    ...and alluminium, metals that didn't exist when it was made!....

    Are you sure?

    I found this when I went Googling.

    Some scholars have suggested limited production of aluminium metal may have occurred as long as 2000 years ago! In his famous encyclopedia "Historia Naturalis" Pliny the Elder mentions a familiar sounding silvery metal:

    "One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had made the metal from plain clay. He also assured the Emperor that only he, himself, and the Gods knew how to produce this metal from clay. The Emperor became very interested, and as a financial expert he was also a little concerned. The Emperor felt immediately, however, that all his treasures of gold and silver would decline in value if people started to produce this bright metal of clay. Therefore, instead of giving the goldsmith the regard expected, he ordered him to be beheaded."

    While there is obviously no way of testing the truth behind this story (Pliny's Historia Naturalis is not known for its scientific accuracy!) the similarities are interesting. Indeed, almost 2000 years later another Emperor, Napoleon III, used aluminium plates and cutlery to serve the King of Siam at a state banquet. Aluminium was then a rare and precious metal and less important guests had to eat from plates of pure gold.


    I knew about the Napoleon link but not the Tiberius one.



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    The cross slide isn't heavy, I'll have to do the test on the lead screw. John Dammeyer on the ELS group did some calculations for me (since I posted here)and came up with a torque of 12oz.in so a minimum size 23 stepper at 55oz.in should be sufficient. He suggested belting it down 2 to 1as it's a 5 T.P.I.

    I'm on Mac and Linux (anti microsft!) so I'll have to find some body to try the
    program you propose.

    Thanks, Matthew

    Quote Originally Posted by Al_The_Man View Post
    I would think a 1944 Colchester at least deserves servo's
    I would expect it is on the beefy side and not exactly a 'table-top'

    For Break-away torque, the method you describe, or similar would work, you can also get an idea using sizing programs like Kollmorgen etc, http://kmtg.kollmorgen.com/motioneering/app_engine/ . which introduce the inertia motor to load aspect (Free).
    Al.




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    Geof,

    I allways thought that the first smelting of Alluminium was arround 1875 don't know where I remember this from, happy to be corrected! I know I'm right about the stainless!

    Respectfully, Matthew


    Quote Originally Posted by Geof View Post
    Are you sure?

    I found this when I went Googling.

    Some scholars have suggested limited production of aluminium metal may have occurred as long as 2000 years ago! In his famous encyclopedia "Historia Naturalis" Pliny the Elder mentions a familiar sounding silvery metal:

    "One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had made the metal from plain clay. He also assured the Emperor that only he, himself, and the Gods knew how to produce this metal from clay. The Emperor became very interested, and as a financial expert he was also a little concerned. The Emperor felt immediately, however, that all his treasures of gold and silver would decline in value if people started to produce this bright metal of clay. Therefore, instead of giving the goldsmith the regard expected, he ordered him to be beheaded."

    While there is obviously no way of testing the truth behind this story (Pliny's Historia Naturalis is not known for its scientific accuracy!) the similarities are interesting. Indeed, almost 2000 years later another Emperor, Napoleon III, used aluminium plates and cutlery to serve the King of Siam at a state banquet. Aluminium was then a rare and precious metal and less important guests had to eat from plates of pure gold.


    I knew about the Napoleon link but not the Tiberius one.




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    Quote Originally Posted by mattinker View Post
    Geof,

    I allways thought that the first smelting of Alluminium was arround 1875 don't know where I remember this from, happy to be corrected! I know I'm right about the stainless!

    Respectfully, Matthew
    You are correct aluminum was not produced in commercial quantities until then but it was produced in small quantities a lot earlier; as my excerpt pointed out it was a precious metal.

    I think the statue of Eros, Piccadilly Circus I think, was cast in aluminum around the late 1800's.

    Perhaps I should also Google stainless just to be awkward.



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    Eros, layshafts and Maths

    Goef,

    what you only "think" Eros was cast aluminium, your slipping, your right, but....

    I think the statue of Eros, Piccadilly Circus I think, was cast in aluminum around the late 1800's.

    Perhaps I should also Google stainless just to be awkward.[/QUOTE]

    Google away to your hearts content!

    Meanwhile, I'm going to start to cobble together a temperoy motor mount so that I can turn a new layshaft to replace the missing one that this "pig in poke" doesn't have! It's the only lathe I've got so it will have to stay working!

    Fortunately, I've had some mathematical help from elsewhere, but if anyone wants to add their 2cents, Euro, dollar, pence, whatever! I'm open!


    Matthew



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    The beginning!

    Well, if this is going to be a conversion log, maybe I better show you something of what the lathe in question looks like! tony@lathes.co.uk confirms that it's a standard 1930's Colchester lathe, this one was made in 1944 which explains why it's exposed flat belt drive. I have mounted the motor on a tempoary plate and have started turning a lay shaft it has to work before I can CNC it! Over a 40cm (OK 16") I have a 0,002" taper so I'm not touching the tailstock for the time being! For the time being I'm thinking mostly in inches, as the cross slide is calibrated in thous, this is going to be a bit scytsophrenic for me, as I've spent nearly thirty years here in France, so I have a metric tendancy despite my being brought up on the Imperial system! At least all those whitworth "spanners" (wrench allways sounds so violent to me) that I've been dragging around since I trained as a mechanic in 1972 are getting used! My unified stuff gets used on my Elliot M10 shaper (maybe a CNC shaper later!)

    I did a black and white version of the general view just for Geof!

    I still need help with the calculation of the stepper size for the lead screw!


    Matthew

    I don't seem to be able to attach the pics, I'll send this and try later!

    Last edited by mattinker; 04-11-2007 at 04:14 PM. Reason: spelling mistake


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