Free-standing striking dummy with arms.

Posted: February 18, 2013 in DIY, Duct tape, Foam, Futon, Grappling, Heavy bag, Kicking, Punching, Striking, Tires

Similar commercial equipment: H2H Trainers grappling arms/legs/dummy, Body Opponent Bag (BOB), Century Wavemaster 2XL Pro

It is somewhat surprising to me that heavy bags with arms are not much more common than they are. Having arms on the bag makes training more realistic and interesting, and provides an opportunity to work on blocks, redirects, traps, and other techniques rather than just strikes. Obviously, there are options like a mook jong or single-arm apparatus that are used for specific Kung Fu drills, but what I wanted was an arms with joints and hands. These, it turns out, are much harder to come by. In fact, the only commercial example could find is offered by the good folks at H2H Trainers. I purchased a pair of the arms that can be attached to an existing heavy bag from H2H Trainers, and I am quite happy with them. Some aspects of the design below were borrowed from these arms, so if you are not looking to make your own, I definitely recommend that you check out their website. They have arms, legs, and entire dummies available.

Phase One: The base and core
The basic aspects of making a DIY free-standing striking dummy were covered in a previous post, but adding arms does require some important modifications. The start of the process is the same, however — the inner core is made using three 2″ x 4″ pine boards glued and screwed together at right angles and kept upright by attaching a piece of plywood to the base.

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Some large nails or screws are added at various points to the bottom to help secure the post in the concrete.

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The next step, as before, is to put two old car tires around the post and to mix and pour enough concrete to fill both tires (some space at the top is ok — foam can be added to top it off at the end). This works out to four or five 65 lbs bags of ready-mix concrete, giving a final weight around 250-300 lbs for the base. So much weight makes it very stable against punches and kicks, but it remains moveable by tipping it over and rolling it along on the tires. The concrete needs to harden for a couple of days, but you should check on it periodically at the beginning to make sure everything is centred and straight before it becomes permanent.

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Phase Two: The body and head
At this point in the previous build, we were ready to wrap the post with half a futon mattress and duct tape. However, for this version we first need to drill a hole using a hole saw attachment on a drill and to insert and secure a length of 2″ ABS pipe. The length of the pipe used here will be a bit less than the final width of the dummy’s shoulders. About 18″ should be plenty, and you can trim it later as needed. To secure it, just screw through the wood and into the pipe in a few places on both sides of the post.

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Next, you will probably need to trim the top of the post to get the desired height. Keep in mind that you will be adding a head on top when deciding how much to take off. Once that is done, you can make a neck and central block for the head. For the neck, I used some clear plastic tubing that I had with a large spring stuck in the middle. (In the previous build, I used a garden hose and spring connector that you can get from a hardware store — either should work). Drill a hold downward from the top in the middle of the post, insert the hose, and secure it with screws from all four sides. Next, make a block out of 2″ x 4″ pieces by gluing and screwing them together. Drill a hole in the bottom of the block, place it over the hose, and screw it in place.

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It’s time to add the padding, which once again is half an old futon mattress. Before you start, clean off any excess concrete that is on the outside of the tires using a brush and hose, and let it dry. When you’re ready, cut the futon mattress in half and wrap it around the post. This is somewhat trickier than before because you’ll have to cut holes in the mattress for the pipe to pass through. Wrap the whole thing tightly with plenty of duct tape. Add some foam and stuffing from the mattress to the top to cover the post and tape this up as well.

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Once the main body is done, it’s time to make the head. In my case, I filled a plastic grocery bag with foam and stuffing from the mattress, and then wrapped it tight with duct tape, shaping it into a head-like form along the way. I then cut a hole in the bottom and emptied it out enough to make room for the block. I placed it over the block and added some more tape to keep it in place.

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The head is going to take a beating, so I further secured it by putting a canvas shopping back over top, with the handles looped around under the pipe — plus a little more duct tape around the neck and over the shoulders for good measure.

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The head and body are then covered with a large canvas duffel bag (50″ in length), which can be found at surplus stores. This was larger than the one I used in the previous build, because in this case it is also going over the head. I removed the handles and straps, pulled it down over top of the dummy, and tied it tight at the bottom using some rope. The bag is much looser on the body than the other build, but that’s ok because this dummy has a front and a back — just tie it so the looser part is at the back. Also, unlike the previous build, the canvas bag on this dummy can be removed easily for cleaning if necessary. I had originally intended to put head gear on as well, but this proved unnecessary. Instead, I just tied a piece of rope around the next to help give the head and neck a more distinctive appearance.

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Phase Three: The arms and hands
Each arm is made from one piece of 2″ ABS pipe (upper arm) and one piece of 1.5″ ABS pipe (forearm). Best to start with pieces that are longer than you need in case it takes a few tries (if so, just cut off the end and start again). Something like 18″ or so ought to be more than enough. Making the elbow joint will require some tinkering to get it right, but here is the basic idea:

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The cuts can be a little finicky, but the goal is to get the smaller pipe to sit inside the end of the larger pipe and to trim off corners of the smaller pipe so it can rotate inside the larger pipe. Drill through everything and fasten together with a bolt and a lock nut, with washers on either side between the pipe and bolt and between the pipe and the nut. Once you have it working, it will look like this:

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At this point, the length of the upper arm isn’t so important. However, you will need to get the forearm to the right length before you proceed. I suggest just lining it up with your own arm, marking it, and cutting it to length (probably 12″ or so at most). Once that is done, drill five large holes in the forearm pipe at different distances from the end and on different sides of the tube.

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I’ve tried a few ways of making hands, but this one seems to be the easiest and to give the best results. Of course, you don’t need to make individual fingers at all unless you want the dummy to be positioned to make fists, knife hands, etc., or if you want to practice wrist locks and such.

For this method, we start by making each finger. You can use any type of wire for this, but I found it convenient to use foam-padded twist ties. Each tie can make two fingers. Take some of the leftover stuffing from the mattress, and wrap one end of the twist tie with it and some duct tape to make it the thickness of a finger. Repeat five times for each hand (obviously).

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Now put the fingers inside a glove and twist them together at the wrist. Add some stuffing to the glove to fill it out, and tape it shut at the wrist.

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Now insert the other end of each twist tie through one of the holes that you drilled in the forearm. (This is a bit tricky, but you’ll be able to make it work by bending the tie slightly to help guide it through the hole). Pull the ties through until the wrist area is the correct length. Wrap the protruding ties around the pipe and tape them down. This will double as your first bit of padding for the forearm in addition to securing the hands to the arm.

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Phase Four: The shoulder joints

I considered a variety of ways of making a shoulder joint, including some ideas for ball-and-socket joints, but in the end I think the one that you can see on the H2H Trainers website is the best (kudos to them for coming up with this, as well as the elbow design).

The shoulder joint consists of one eye bolt in the end of the arm and another at the shoulder, connected in the middle with a thick bolt and washers. This allows rotation in all directions, creating a convincing shoulder model. To attach the eye bolts to the arm and the body, I cut a circle of the correct diameter (just under 2″) using a hole saw on my drill press. You will need a total of 4 of these. I sanded the edges smooth on the belt sander, and drilled a hole in the centre on the drill press. The eye bolt goes through this hole. You will also need some large washers and a lock nut. The eye bolts that I used were 3/8″ x 4″.

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Trim the upper arm to the right length (again, probably 12″ at most). Then insert one of these circles into the end of the arm, eye bolt out, and the other into the pipe that passes through the body. Secure them with screws.

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Now attach the two eye bolts together using a wide bolt and lock nut. I put a washer in each space, so it goes bolt-washer-eye bolt-washer-eye bolt-washer-lock nut. You also don’t want a lot of play within the eye bolts, so make sure the connecting bolt is thick enough.

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The eye bolts have a tendency to become loose with use, so I wanted to be able to tighten them up as needed. To make this easier to do, I drilled a hole in the two pipes with eye bolts, large enough for a wrench to be inserted.

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Next, cover the arms in foam and duct tape. For the main areas of the pipes, this is easy. But for the joints it’s a bit trickier, because they need to be covered at all times but they also need to bend. Here is what I came up with:

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Then I just wrapped the elbows loosely in some fabric to keep the flaps in place and taped it in place with a small amount of duct tape.

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I also stuffed a tennis wrist band into the wrist area, though you could just wrap this with fabric as well. Basically, this is just to thicken it up a bit and to make sure the pipe isn’t exposed at the wrist.

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Phase Five: Finishing touches

The last step is to dress him up. I decided to use a long-sleeve shirt with the same sort of olive drab army colour, which I picked up at a thrift store.

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The last task was to deliver him to the dojo. He is no lightweight, so I recommend having a helper for this. In my case, I ended up rolling him up a ramp into my trailer by myself (not recommended) but I did have help to unload him and roll him into position when I got there.

Here he is in his new home:

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I expect that there will be a few adjustments and repairs to make in time, but so far he has been working out quite well.

Comments
  1. […] I have written up the build details for a free-standing striking dummy with arms. Check it out over at Martial Makers. […]

  2. Andrzej Pietrzak says:

    Oh man, I visited your page due to an unrelated Google search and just said OMG this can’t be real.
     
    I’m a Filipino Martial Arts practitioner, and I’ve been working on my mook-jong based training dummy. I tried ball socket joints same as you, but I’ve had problems with eliminating play in the joint. My next idea was to use strong rubber and simulate muscles with this to allow movement and as a bonus some back-to-default force to give user some resistance/feedback when training locks, but it seems complicated and time consuming to design. I’ve seen H2H Trainer arm and tried to replicate it as I’m not able to buy myself one.
    I like your ideas on how to pad joints to make them safe. It will save me a lot of time. Great work.
    I think that making a realistic size neck section is a good upgrade to consider. It allows to also train some head manipulation techniques (spring+water hose connection should allow it, if no, it shouldn’t be hard to stabilize head section in other way) and gives you a vital target to train against.

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