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Thread: How to Build a Skuff Machine

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    How to Build a Skuff Machine

    Here are plans for a skuff machine that can built with hardware store parts and a rotisserie motor for a few dollars, provided you have some handyman skills. If the exact construction methods don't appeal to you, hopefully at least I have given you something to think about. Nothing makes hash better than a rotating skuff machine.

    1. General construction
    The machine is basically like a squirrel cage, with the pot being the squirrel. Two circular plywood sides are aligned on a shaft, with silk-screen netting between. The cage is rotated with a motor, and the glands fall through the screen to be collected on a base, like a piece of glass, or perhaps foil.

    The device itself can be made with hardware store parts, with one exception; you need a motor. It should turn no faster than about 10-15 RPM, and needs to have good torque to handle the out-of-balance condition of the device when loaded. A rotisserie motor is perfect. I bought one from a cooking supply store for $43, the most expensive item on the device. Some Home Base type stores may have units designed for outdoor use. If you're lucky it will come with a metal bracket to hang the motor. I gather Sears is a source as well.

    2. The shaft and cage
    The sides of the cage can be just about anything. I choose 3/4" plywood for two reasons; circular pieces were available already cut down at Home Base in that width, and the wide edge gives you plenty of area to mount the screen.

    The sides need to be held parallel on a shaft at some distance. I choose 6 1/2" pretty much arbitrarily, except that the total width of the screen, including the width of the plywood sides, was 8", and that made for even strips I could cut from the silk screen frame I was working with.

    The diameter of the wheel is also variable. I choose 16", as a larger wheel seemed to require a more substantial structure to hold it together. But the
    device turns very slowly, so it does not need to be very strong and the tolerances do not need to be tight.

    The choice of shaft was easy; a 7/16" threaded rod. The threads give you a way to mount the plywood sides on the shaft with nuts. I also used a short piece of steel tubing on the shaft between the sides to hold the sides in place, but plastic pipe should be fine. Why 7/16"? Because all rotisserie motors are built with a 5/16" standard square opening to drive the spit shaft, and in order to have enough steel to produce a 5/16" square end, you need to start oversize.

    3. The frame and bearings
    The easiest frame to hold the wheel would be two parallel pieces of plywood, stiffened with cross pieces. I choose to be a little more elegant, so I used 1 x 2 hemlock pieces to build an open frame.

    The threaded shaft needs to be located in the frame with a bearing surface. If it was a smooth piece of steel, you could go with a bronze sleeve, since the device turns so slow. But a threaded shaft would cut up the bronze in short order, so a ball bearing unit is required. I found cheap 7/16" bearings at Home Base in the nuts and bolts area in a speciality cabinet.


    4. The screen, and how about a door?
    Some say that the best screen for skuffing is fine steel, around 100 mesh, but I've had excellent results with plastic. I settled for silk screen material that I cut out of frames I purchased at a printing supply shop. I made three drums, each with a different mesh screen, 83, 110 and 137 (see below for comments). The screen needs to but cut out of the frame and into wide strips that are draped over the wheel.

    How to hold the screen on the wheel? I thought of several ways, including glue, like Liquid Nails. I ended up settling on plastic strips drilled and screwed to the plywood wheel edge with small pan head screws. I bought the styrene strips at a local hobby shop, but I'm sure there are other materials that would work.

    Now, how do you get the pot in and out of the wheel? Two ways. First, you could take a jig saw and cut a hole in one of the plywood sides. I planned on doing so,until I thought of how to hang the door and how to seal it, and what a pain in the butt it would be to get the pot out (turn the whole thing sideways and shake it??).

    So, I determined to find a better way, and settled on a flap in the screen. The screen is screwed down around the wheel except for a 4-5" section. I mounted nut studs in the wheel, and drilled holes through a section of the plastic strip to fit over the studs. A cross piece of hobby hardwood fits across the end to provide stiffness. Wingnuts hold the flap down on the wheel. To open the unit you spin the wingnuts, lift the flap off the studs, hinged just with the screen material, and just let the flap flop down. It's easy to unload, you just turn the wheel and the pot flows right out the opening. It's not real sturdy, but it doesn't have to be.

    5. Mounting the wheel on the shaft
    Step one is to mount the circular plywood sides on the 7/16" threaded shaft. I cut a piece of steel tube 6 1/2" less the width of two large washers, and drilled a hole in the center of each plywood wheel. I put one wheel on the shaft, ran a washer up against it, dropped on the steel tube and another washer,
    and then completed the sandwich with the other plywood side. To hold the unit together I ran up washers and lock rings on both sides and bolted it together with 7/16" standard nuts. I used two per side to provide some clearance. That made it easy to bolt the shaft up tight against the bearing sides, as there is no open shaft between the bearings, just a solid chunk of nuts, washers, plywood sides and the steel tube spacer. Nice and rigid.

    I didn't worry about the length of the threaded shaft at this point, I just left plenty of length hanging out both sides.

    6. Building the frame
    I cut two lengths of 1 x 2 24" long (the width of the mirror I use as a collection base), which is plenty of length for stability. I cut two more 1 x 2 pieces equal to the diameter of the wheel plus three inches on the bottom and one on top for clearance. I glued and screwed the two pieces together in a T shape and allowed the glue to dry.

    To add stability, I created a stiff triangle by adding a 1 x 2 diagonal brace, which runs from the pivot point to the base. It's easy to cut the brace if you use the T section as a template, first marking a line where it crosses the upright piece, cutting it, putting it back in place and marking where the base
    piece crosses it. I screwed and glued these into place, with Liquid Nails and #6 self-drilling screws, after drilling a pilot hole in the 1 x 2 with a combination bit that also chamfers out a depression for the screw head (a couple of bucks at the hardware store). Otherwise you will split the wood.

    The next step is to mount the bearing at the pivot point. Home Base must have been missing some pieces, as the bearings were just smooth steel with no way to mount them to anything. Oh well, no biggie, I drilled out a hole in the 1 x 2 vertical pieces with a 1 1/8" hole bit, just to the depth of the bearing body. I then drilled a 3/4" hole from the back to provide clearance for the nuts bolted to the shaft. To hold the bearing into place, I could have glued it, and that probably would have been fine. But instead I found a big flat steel washer the right size, and drilled a couple of holes in the edge, placing the washer over the bearing and fastening the washer to the 1 x 2 upright with a couple of small pan head screws. Voila, two base sides with bearings.

    7. Support brackets and cutting the shaft
    The next step was to partially assemble the unit. I added a 7/16" jam nut on each side of the wheel assembly and placed the frame sides on the shaft, bolting up another jam nut on either side to hold it all together. I gave it a spin to make sure nothing was hanging up. I then arranged the frame on a level surface and squared everything up. When I was happy with the arrangement, I measured
    across the unit for support brackets. I used three cross pieces, one at each end of the base and one right across the top of the uprights. Diagonal bracing was considered, but it didn't appear to be necessary.

    I wanted to be able to take the unit apart for storage, so instead of gluing and screwing the support brackets to the frame, I mounted nut studs in the frame and drilled holes in the brackets, which are held to the studs with wing nuts. The main advantage of the wingnuts is the ability to make up wheels with different mesh screens and drop them right in the basic frame.

    Once the frame was complete, I marked the shaft on one side to cut it off just past the outside bearing jam nut. The other side will be driven by the rotisserie motor, and here's where some fancy engineering might be required. I was lucky, and my motor came with a steel bracket that the motor rested in. The bracket was designed to fit into some standard mount in upscale barbeque units, and had some unnecessary surfaces, which I cut off with a dremel tool. I was left with a flat piece of steel with the motor attached. It worked out that the motor could be held in proper relationship to the shaft merely my adding another 1 x 2 vertical piece parallel to the upright support, plus one 1 x 2 thickness for clearance. I clamped everything together on that basis, and marked the threaded shaft so when cut off it would fit right into the rotisserie motor drive opening.

    I took the unit apart and cut the shaft ends with a dremel tool (using the large fibre cutoff wheels).


    8. Mounting the motor and tooling the shaft
    The end of the shaft on the motor end needs to have a 5/16" square section filed or cut out of the 7/16" round steel. I used a dremel tool with the small heavy duty ceramic cutoff disks, working slowly and carefully, and test measuring often. It was actually very easy to do, as the threaded shaft was soft steel, and you could easily do it with a file.

    After I was sure the end was right, I re-assembled the unit. To mount the motor, I held it to the end of the shaft and marked where the bracket needed to be, adding a vertical 1 x 2 support at that point. I doubled the thickness by adding another 1 x 2 glued to the support, and added a horizontal support at the top over to the vertical frame member.

    To be able to take the unit apart, I added three more nut studs on the motor support 1 x 2 and drilled three matching holes in the steel support, which I mounted with wing nuts.

    Next I plugged it in and turned it on; success! It spun very nicely.

    9. Adding the screen
    At this point I started to mount the screen. The screen is not long enough to go all the way around the wheel, so you have to glue the ends together (Liquid Nails works well). I wanted to support the screen at those points, and at the opening, so I added small wood cross pieces inside the wheel. They also act as baffles, to tumble the material a bit. I added them as I went around the wheel, to make sure they ended up right underneath the glued seams.

    I started by adding one of the cross pieces and screwed the screen to it and the edges of the wheel with a plastic piece covering the screen to hold it down. I then draped the screen over the wheel and fastened it down with pre-drilled plastic strips using self-drilling pan head screws.

    Half way around where I ran into the glued seams, I added the other cross pieces, and screwed the screen down to that as well, with another plastic stiffener across as support to hold the screen down.

    Where the screen completed the circle, I cut it off square. I then marked the area where I wanted the flap opening, and added the last plastic strips to the edge of the plywood right up to the opening. I then added 7 nut studs, two on the edge of the wheel along the sides, and three across the top, where the opening started, and where the other edge of the screen is attached. I cut plastic strips to length, and pre-drilled holes to match the studs, elongating the holes with a small file to allow clearance (you can't lift a circular section off a wheel on straight studs).

    For the end I added a small piece of hobby hardwood. I filed slots in the ends so that the plastic strips would fit under the wood cross piece, and after making sure everything was aligned, I glued the plastic and wood together while bolted to the wheel with the screen in place. I used painter's tape to separate the glued pieces from sticking to the wheel. After the glue dried, I removed the tape.

    I then removed the motor to allow the wheel to spin freely, and balanced it by screwing steel washers to the side as needed. That's it.


    10. Operation
    To open the unit, first you spin off the wingnuts holding the wooden cross piece at the end of the flap, then the next lower set of wingnuts and then the last set at the hinge end of the flap. The flap peels itself right off the wheel as the plastic strips straighten out. The flap just hangs off the wheel connected only by the screen fabric itself.

    Dump some pot inside, and then re-bolt the flap to the wheel the other way around, first with wing nuts near the hinge, then in the middle and finally across the wood end piece. You may have to bend the studs a bit to allow the wood piece to clear the ends depending on the thickness of the piece (there are about a thousand other types of material you could use, but this works).

    Turn on the motor and wait. Again, rotisserie motors are perfect, as they are designed to operate for long periods. You measure your progress by examining the deposits with a loupe or a microscope. I have a cheap 16x loupe that works fine for this purpose. After running the machine for several crops, I have learned something about the process.

    I start with a 137 mesh screen, the tightest I use. The first pass is for about 20 minutes, and that should just knock off gland heads. That material is colected and compressed by hand, and it's really special. A small piece, like a shrew dropping, provides a wonderful head rush, like the best vaporizer hit you've ever had. You can't do it too often though, or the rush effect is reduced considerably. Twice a week is about the maximum for me. I then run the 137 screen for about 45 minutes, maybe an hour. This grade of powder consists mostly of heads and stalks, compresses easily, and is premium grade hash, with a nice lift off and a mellow high.

    Then I might run the 137 mesh again for another hour, which produces a second grade of hash, with a fair amount of contaminants, cellular hairs and mineral trichomes. This grade also compresses easily, and has a nice taste. Finally I switch wheels to the 83 grade and run it for a couple of hours, sometimes with a rubber ball in the cage to work the material, especially if the skuff consists of large pieces of leaf. This grade usually compresses with some work, but sometimes it is necessary to mix in a few drops of water and heat the powder mixture in the microwave for brief periods, a little at a time, until it can be worked. I like the utility grade, because you can smoke more than a couple of shrew droppings, and who doesn't like to smoke hash? It's a nice gift for friends as well.

    I recommend that the skuff be at room temperature, 60 degrees or so, not too dry, and definitely not processed in any way, like being crushed up, frozen or dried. The machine will strip nearly all the glands from the skuff regardless of the look and feel of the material. Like I said, if it's very leafy, use a tennis ball or something like that to rotate with the skuff to help it contact the screen.

    What to do with the exhausted skuff? If your machine works as well as mine, you can put it on the compost heap, because there's nothing left in it. I've smoked bombers the size of cigars with exhuasted skuff and it was pointless.

    Credit the great oldtimer1 for the basic design of the unit, and for the inspiration to build it, and good comments from the gang at . . . well, you know who you are. Dedicated to Aeric77, long may he grow.
    hydrorod likes this.

  2. #2
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    Re: How to Build a Skuff Machine

    A picture could be worth a thousand words. The concept is there.

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    Re: How to Build a Skuff Machine

    post some pictures dude, this sounds like a great idea

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    Re: How to Build a Skuff Machine

    one picture of the completed project and this would all make sense.

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    Re: How to Build a Skuff Machine

    Look at a clothes dryer. Same thing.(And works)