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Thread: Jointer RPM

  1. #1

    Jointer RPM

    Okay, second question regarding my WRR Jointer. Now this machine has Babbitt Bearings, a two knife cutter head witha diameter around four inches and is pretty stout steel wise. Orginally it was designed for flat belt operations, but for some reason I cannot get a permit from the EPA to dam up my local stream to install a water wheel.

    Purchasing an electrical motor big enough to drive this thing would be prohibative, but I do have a 25 hp farm tractor. I was thinking I could rig up some belts to drive this thing at any given speed, but it would be much simpler to attach a shaft directly to the PTO of my tractor.

    Of course I would use a shear pin as I am not completely foolish, but my question is, my tractor only puts out about 1000 rmp on the PTO when running at full throttle (3000 rpm). Is that fast enough considering the age, rotating mass, and size and number of the cutterhead on this machine?

    Last edited by Travis Johnson; 03-24-2007 at 10:54 AM.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  2. #2
    Join Date
    Oct 2006
    Location
    Tokyo Japan
    Posts
    15,582
    Travis, I also have a two knife jointer, not as big as yours, but close.

    The motor runs at 1440 rpm, the pulley at the motor is about 8" in diameter, the pulley on the knife end is about 3" in diameter, so 3" divided by 8" is 0.375.

    1440 divided by 0.375 = 3840 RPM, that is just off the cuff, I could be out by a bit....?

    BTW, the motor if in Osaka, would run at 1730 rpm (60 hertz in Osaka, 50 hertz in Tokyo).

    I'll check later
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  3. #3
    Join Date
    Oct 2006
    Location
    The Heart of Dixie
    Posts
    4,265
    The obvious answer is change the pulley dia.'s to get the proper speed. Which I don't know what that is. Also remember you really want to find the correct Surface Feet per Minute (SFM) and calculate RPMS from there. SFM takes into consideration the dia of the cutter head. The simplest way is to just calculate the SFM for 2 or more jointer's and go from there.

    Now I got to ask this. How big a board are you going to put on there?? Unless you jointing ship timbers I would just put a 3HP motor on it. Vintage motor of course. If my 12" ever gets here I am going to look for a 2hp motor for it. Might be a little undersized by some people standards. But I am not going to be cramming a 12" board in it. I can feed it slow if it bogs down.

    Jeff
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  4. #4
    Join Date
    Dec 2006
    Location
    37 5'16.25"N 7625'28.11"W
    Posts
    193
    Travis,
    General wisdom says jointers should rum about 4000rpm. The reasoning is at higher speeds the possibility of throwing a knife increases, especially in the older machines. Babbitt bearings are considered slow speed also so you don't want to run them too fast either.

    A 3-5hp motor would work fine. A vintage motor (or water wheel) would be cool, but cost and availability can throw a wrench into the plan. I've seen similar jointers constructed with a base of sorts that incorporates a motor platform to make it one unit for mobility. Check out OWWM.com for more info on your jointer and look at the photos of large jointers for ideas.

    Better yet, just send it to me and I'll take care of all your problems Heck, I'd even drive over and load it myself just to help you out!

    Mike

  5. #5
    Thanks guys. I was hoping I could juust get by with a direct drive. Cobbling up bearings, an aux shaft, pulleys and all that will be a headache so I was hoping to avoid all that.

    I was thinking of just using a PTO shaft purchased from my local equipment dealer. They are pretty cheap at around thirty bucks. From there I can toss it on the lathe, bore out the inside diameter to take the 1 1-2 inch shaft that comes off my jointer, drill a hole for a shear bolt and I am off to joining lumber. I mean that is if the 1000 rpms I get out of my tractor is fast enough. The problem is, anything that is quick and easy to do, typically does not work.

    As for the hp needed. I was told that it takes 1 hp for every four inches of knife length. That makes sense as a 4 inch jointer typically has a 1 hp motor. Your machine would need a 3 hp motor, and mine would need a 4 1-2 hp motor. To expensive for me when I have a tractor that could spin the cutterhead.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  6. #6
    Quote Originally Posted by M Toupin View Post
    Travis,
    General wisdom says jointers should rum about 4000rpm. The reasoning is at higher speeds the possibility of throwing a knife increases, especially in the older machines. Babbitt bearings are considered slow speed also so you don't want to run them too fast either.

    A 3-5hp motor would work fine. A vintage motor (or water wheel) would be cool, but cost and availability can throw a wrench into the plan. I've seen similar jointers constructed with a base of sorts that incorporates a motor platform to make it one unit for mobility. Check out OWWM.com for more info on your jointer and look at the photos of large jointers for ideas.

    Better yet, just send it to me and I'll take care of all your problems Heck, I'd even drive over and load it myself just to help you out!

    Mike
    Don't say that too loud. I am considering selling it after its up and running. The size alone scares the pants off me.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

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