I wana make a cartridge (brass) thumbler...

Discussion in 'The Projects Forum' started by herbeapuce, May 23, 2013.

  1. herbeapuce

    Thread Starter New Member

    May 23, 2013
    3
    0
    Hi. I am thinking about making my own brass rotary tumbler.

    I am looking at eBay for some cheap gearmotor.

    so far I thought of 2 sources: gearmotor for industry ( AC and DC ) and windshield wiper motor..(12v DC) Ideally the rpm would have to be around 40 rpm

    I don' t know much about circuit in general... also I am a cheap baster to that limits the choice greatly.



    Ok I have many questions for you guys...

    let start with an 120V AC gearmotor...

    A- is it OK to suppose the first rpm is 1725 for most 120V ac gearmotor ?

    B- if it's a 20:1 greamotor, then the final speed would be around 86 rpm...Still too fast for my needs ( I need close to 40 rpm) can I take a regular ceiling fan speed controller to cut the speed in half ? ) I read that not all motor can be controlled by ceiling fan rheostat...

    C- if I can't use this, can you point out the right type of control please? can you see one here : http://dx.com/ (told you I was a cheap baster...hehe)

    now if I end up buying a 12 V DC gearmotor...

    D- can I use the same dometic ceiling fan controler

    E- if not, what can I use to control the speed ? if you can, can you please provide a link for such a part, preferably here : http://dx.com/

    F- also for my power supply, I was thinking of using a old PC power supply. I understood that most atx power supply have 12, 5 and 3.3 volt. do you know any reason why I should not try different voltage ? that won't damage my DC motor , right? I understand slowing the speed can affect the cooling of the motor, hopefully I won't slow it too much...

    G- regarding the different voltage of a atx power supply I understood that the lower voltage have more amp. so will the motor have more torque with the lower voltage ?

    H- I am not considering buying a DC motrogear other than a 12V because I imagine I will need a costly transformer to get the higher DC current.. I am righ?

    I - Am I right to treat a windshield wiper motor just lire a 12v DC motor. same controls, same problems ? ( but with a closer to wanted rpm )

    Please if you know of a better ( and cheap ) way, you are very welcome to share it.

    thanks for your help
    stef
     
    Last edited: May 23, 2013
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    3,756
    Make something like a rock tumbler. They simply have a drum filled with grit. The drum is set on pair of rollers. The large diameter of the drum acts as the large gear to turn itself against the small diameter.

    A 5 gallon bucket would even work for a larger version. set a bucket on the one roller and add three more bearings with solid mount (no motor). Put some o-rings on the motor shaft so it gets some traction with the bucket. The bucket diameter is about 12 inches so find a motor with a 3/8" output shaft and your 1725 motor RPM gets you down to 54 RPM. Hows that you cheap b?
     
  3. herbeapuce

    Thread Starter New Member

    May 23, 2013
    3
    0
    that is a good idea
    I have seem somes like that on youtube...

    one thing I am worried about a bit is that shaft turning at 1725 againt the bucket... not sure it won't slip of jump and not lasting long...

    I would really be happy if I could find a way to slow down the motor(s).

    but thank you for your help.

    stef


     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    How many hours does it need to run? And the load weight it needs to turn?

    A DC motor might not be ideal for many hours continuous running.

    A rock tumbler I saw had a small AC mains motor with integral worm gearbox. The final sharp speed was about 30 RPM.
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Many (if not most) brass tumblers vibrate rather than revolve. The plastic container for the brass is rubber coupled to a vibrating AC motor. The spherical shape of the container causes the medium and the brass to rise at the center of the container, move toward the outside, and then sink to the bottom of the container. The cleaning medium is either crushed nut hulls or ground corncobs. I usually let mine run overnight.
     
  6. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    I would use the AC motor that they use to oscillate the cheap fans
    Like this and it moves really slow
    [​IMG]
    [​IMG][​IMG]
     
  7. Rbeckett

    Member

    Sep 3, 2010
    205
    32
    For cartridges you want a vibratory type of tumbler. The higher the frequency the better. So using 1725 RPM or 3200 would be good and then creating the counterbalance to vibrate the media would be relatively simple. Much easier and quicker than a rotating tumbler. Need help? PM me and I will help you build the eccentrics to vibrate the container.

    Bob
     
  8. herbeapuce

    Thread Starter New Member

    May 23, 2013
    3
    0
    Hi everyone

    and thank you for your suggestions and help.

    I should have said I wanted a rotary tumbler. I want to try the stainless steel pin media for cleaning up brass. apparantly it's now the best thing to use.
    http://www.stainlesstumblingmedia.com/. ( clean all flash holes and all )

    I guess this motor would have to run for 2 to 3 hours straight.

    the load weight is not that great, maybe something like 5 to 7 pound in a 2 to 5 gallon pale,

    anybody knows how to slow down engines in a cheap way please?

    do you have any faith in something like this : http://www.ebay.com/itm/321131266241?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649



    thanks in advance

    stef
     
  9. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    You did say that; you just didn't say why. I may have to try the ss pin method.
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,001
    3,756

    I think this motor is a great start. It seems to fit what you need at a great price. If it lasts forever, great! If it only lasts for a few runs, you had a great prototype and you re likely to confirm the polishing media does what you want. Some little Chinese motors last for ever, some don't. For $16, it is a bargain of an experiment.
     
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