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John Stevenson's gear cutting writeup

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  • crancshafter
    replied
    Originally posted by metalmagpie View Post
    i found the ivan law book online in pdf. After reading it john's writing is much clearer, thanks!
    ditto

    cs

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  • metalmagpie
    replied
    I found the Ivan Law book online in PDF. After reading it John's writing is MUCH clearer, thanks!
    Last edited by metalmagpie; 11-09-2017, 12:37 AM.

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  • Erich
    replied
    The pins are dropped into drilled holes. Button is then soldered or tack welded into place.
    tool holder is milled with a 5-7 degrees of negative top rake.
    That gives a 5-7 degrees of relief on the front of the tool for cutting.

    Leave a comment:


  • JCHannum
    replied
    It is pretty much described in figure 2. The "pins" are "T" shaped, the top button the desired diameter, reduced in diameter on the lower part to fit in the holes in the tool holder which are on the appropriate centers. The pins are held by grub a screw from the side. The tool holder is fabricated with the 5* relief and pins or buttons ground flat on top.

    Probably the best place for the beginner to start is with the Ivan Law book, after that most of the hard part becomes understandable.

    Leave a comment:


  • metalmagpie
    replied
    Does anyone else have trouble understanding John's technical writing? I learned back in grad school that if I read something a few times and still don't get it, to look for a different textbook because my author was having a bad day when he wrote the part I didn't get. The first time I didn't even understand what the buttons were for. What I don't quite get still is how are the pins attached to the form tool and how the pins are ground to give relief. Sure wish there were some clear photos, oh well.

    metalmagpie

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  • Deanda
    replied
    Originally posted by CCWKenr View Post
    As for the bass shafts or tubes, I bought mine years ago at a Hobby Shop. They fit together very well. I did not check for steel ones but they might have them also.
    I have most of the blanks cut for the gears, now I just need to turn them to the proper diameter and spend the long tedious hours of cutting the teeth. A number of them are the same diameter so I will make a mandrel and turn and cut those at the same time.
    All this stuff I have for this project have been setting in a box for 7 or 8 years waiting for me to continue the job.
    Someone questioned the accuracy of the planets rotation and as I remember the Earth one was off the most.
    Great resources for sure Rich. Thanks for sharing.
    Last edited by Deanda; 11-01-2021, 01:09 PM.

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  • lugnut
    replied
    As for the bass shafts or tubes, I bought mine years ago at a Hobby Shop. They fit together very well. I did not check for steel ones but they might have them also.
    I have most of the blanks cut for the gears, now I just need to turn them to the proper diameter and spend the long tedious hours of cutting the teeth. A number of them are the same diameter so I will make a mandrel and turn and cut those at the same time.
    All this stuff I have for this project have been setting in a box for 7 or 8 years waiting for me to continue the job.
    Someone questioned the accuracy of the planets rotation and as I remember the Earth one was off the most.

    Leave a comment:


  • J Tiers
    replied
    I do not know why the accuracy should be bad for gears, as long as the ratios can be set up correctly with the tooth ratios.

    That may be the problem which Paul is trying to suggest, the ratios may need some "interesting" gear combinations. But as for "irregular", I don't see that as an issue, they are far enough apart that any gravitational irregularities are far less than the error of simply visually seeing the position with the large "representative" planet spheres. Aside from gravitational stuff, the orbits should be fairly ideal at the level of detail such a model can give.

    As long as the ratios between the different planets is set up right, it should be fine. Even if it has nice shiny gears.......

    As for shafts, hobby shops can provide telescoping brass tubing in a range from about 1/8" to 1/2".

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  • RichR
    replied
    Originally posted by CCWKen View Post
    Tedious work but the gears are easy with the right equipment. I'm wondering where you'll get all the telescoping hollow shafts. I guess you can get them in brass though. I need some in steel to make two small spring over center locks.
    Cannibalize one of them old timey telescoping radio antennas.

    Leave a comment:


  • CCWKen
    replied
    Tedious work but the gears are easy with the right equipment. I'm wondering where you'll get all the telescoping hollow shafts. I guess you can get them in brass though. I need some in steel to make two small spring over center locks.

    Leave a comment:


  • lugnut
    replied
    Well Paul, I spent $120 for a set of 32DP gear cutters and it's going to use gears I think by the time I get done, I should know a little more about cutting gears.

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  • lakeside53
    replied
    Party pooper! It's not like he's going launch a rocket to get there.

    I think it's pretty cool!

    Leave a comment:


  • Paul Alciatore
    replied
    The gears are not going to provide any real accuracy in the motion of the planets. Their orbital motions are too irregular for that. You might as well use pulleys and belts.

    But if you want nice and shiny gears for appearance sake, knock yourself out.



    Originally posted by lugnut View Post
    This is what I am attempting to build. Lots of gears to cut. I have some done that I made a few years ago before my eyes took a dump. but now that I got the cataracts removed, My Macular Degeneration under control and some new glasses I am ready to try to finish it.

    Leave a comment:


  • lugnut
    replied
    That largest gear is 123 tooth, the smallest one is 6 teeth.

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  • lugnut
    replied
    This is what I am attempting to build. Lots of gears to cut. I have some done that I made a few years ago before my eyes took a dump. but now that I got the cataracts removed, My Macular Degeneration under control and some new glasses I am ready to try to finish it.

    Leave a comment:

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