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Thread: DIY 2x72 belt grinder build.

  1. #11
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    [QUOTE=Black Forest;1217673]
    Quote Originally Posted by vpt View Post
    A lot of what I am reading seems to point to 90v from 110-120 and 180v from 220-240.

    I was referring to how many volts you get when rectifying the AC voltage. Just make sure what type of rectifier you use if you want to lower the volt out. A straight bridge rectifier will be 1.4 times the input ac voltage I think.

    I was looking at getting one of those converters with speed control and all built in the box much like the one pictured. I see many listed to work with both 90v and 180v. I have a bunch of reading to do yet. I have a couple ac motors that would probably work but I think I would like the speed control of dc, plus it seems to be the power source of choice for belt grinders.
    Andy

  2. #12
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    Tread mill motors are very popular for this sort of build. If you actually scrap a treadmill they usually have a speed controller that works. Usually there is a fancy control head unit, but you can just use a POT for speed control on the input control leads to the speed controller. 5K pots seem to be the choice for these. I've got one with a 5K pot on it, but it seems to not have a fine enough speed control. I'm going to try a 10K POT on it. Basically its the same as a 0-5 or 0-10 input signal except the speed controller provides its own signal power source and you use the POT as a voltage divider.

    You can find treadmill motors and speed controllers on Ebay all the time.

    I'm pretty sure they are square wave pulse output. The idea of pulse is you have full power, but at short intervals. I was told its more energy efficient and the motor runs cooler. The first time I ran across this sort of thing personally was a Minn Kota Maximizer speed control for a 12 volt trolling motor when I was a kid. I know the battery life was a lot longer at medium and low speeds. I think most modern high end trolling motors use this sort of technology built in today.
    Last edited by Bob La Londe; 01-19-2019 at 10:20 AM.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  3. #13
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    [QUOTE=vpt;1217679]
    Quote Originally Posted by Black Forest View Post


    I was looking at getting one of those converters with speed control and all built in the box much like the one pictured. I see many listed to work with both 90v and 180v. I have a bunch of reading to do yet. I have a couple ac motors that would probably work but I think I would like the speed control of dc, plus it seems to be the power source of choice for belt grinders.
    A three phase motor with a VFD is also an option. That is what I use on one of my grinders. 3hp. If you do much fabrication type grinding 1.5 hp might be a bit on the light side.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  4. #14
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    [QUOTE=Black Forest;1217700]
    Quote Originally Posted by vpt View Post

    A three phase motor with a VFD is also an option. That is what I use on one of my grinders. 3hp. If you do much fabrication type grinding 1.5 hp might be a bit on the light side.

    From what I have been reading and watching in videos it seems most grinders can be cranked up to way to much speed. I am wondering if I could just use a smaller pulley on the drive to get more power into the belt and just sacrifice some top end speed.
    Andy

  5. #15
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    [QUOTE=vpt;1217704]
    Quote Originally Posted by Black Forest View Post


    From what I have been reading and watching in videos it seems most grinders can be cranked up to way to much speed. I am wondering if I could just use a smaller pulley on the drive to get more power into the belt and just sacrifice some top end speed.
    That's an option. More low end torque that way, but lower speed also means lower material removal rate. If you go that way I'd suggest using a pair of pulley sheaves so you can have multiple speeds. Not as convenient as variable speed control, but atleast then when you need to seriously grind you will be able to.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  6. #16
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    [QUOTE=Bob La Londe;1217706]
    Quote Originally Posted by vpt View Post

    That's an option. More low end torque that way, but lower speed also means lower material removal rate. If you go that way I'd suggest using a pair of pulley sheaves so you can have multiple speeds. Not as convenient as variable speed control, but atleast then when you need to seriously grind you will be able to.


    Oooo, a two step belt drive! Just stick the motor on a sliding plate to select either of the two sized pulleys. I like it!
    Andy

  7. #17
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    [QUOTE=vpt;1217707]
    Quote Originally Posted by Bob La Londe View Post



    Oooo, a two step belt drive! Just stick the motor on a sliding plate to select either of the two sized pulleys. I like it!
    I was thinking 5ish more like a drill press, but two is better than none.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  8. #18
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    [QUOTE=Bob La Londe;1217712]
    Quote Originally Posted by vpt View Post

    I was thinking 5ish more like a drill press, but two is better than none.


    I was thinking to still stick with the controller with variable speed on the motor. Then just have the "high and low" speed pulley. Without going threw a V-belt system 5 steps on the drive pulley itself would get quite long (10" long) hanging off the motor.
    Andy

  9. #19
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    Well just like that there is a 1.5hp 180v DC motor on the way for $100 shipped.

    Now for a controller. I like these leesons but they sure are proud of them.

    https://www.ebay.com/itm/Leeson-DC-M...r866:rk:7:pf:0
    Andy

  10. #20
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    [QUOTE=Black Forest;1217700]
    Quote Originally Posted by vpt View Post

    A three phase motor with a VFD is also an option. That is what I use on one of my grinders. 3hp. If you do much fabrication type grinding 1.5 hp might be a bit on the light side.
    I recently finished mine:

    Only 1 h.p., but I've not stalled it yet. I may up it to 2 h.p. if I stumble across another Baldor TEFC sometime. About $300 total in parts, and 2 months off and on in labor. The workpiece table tilts 45 and also can be turned 90. I am not a big fan of having the horizontal option as many knifemakers, since it shoots sparks and dust for quite a ways. The VFD is nice for wood and plastic at low speeds and heavy metal removal at 3600 fpm with a 60 grit belt.

    Dan L
    There was a blind carpenter who picked up his hammer and saw.

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