Roly-poly sparring post.

Posted: July 1, 2012 in DIY, Duct tape, Foam, Inexpensive, Kicking, Modern, Punching, Sparring, Striking, Tires, Upcycled

Similar commercial equipment: Pro Bounce Back Bag, ProForce Bounce Back Target, S.M.A.R.T. Bag, Free standing bounce back punching bag

Many readers in my age group will remember roly-poly toys like Weebles. The defining feature of these toys is that they return to an upright position when they are rolled over or knocked down. The physical principle behind these toys is pretty simple. Basically, they are rounded in shape at the bottom and have a weighted base. They are hollow or otherwise much lighter above the base, such that they have a low centre of mass and one stable equilibrium position — namely, being upright. Here is an explanation from Wikipedia:

Another well known application of this principle can be found in inflatable clown-faced “bop bags” that could be punched (by a child) and would return to an upright position.

A more serious version of the bop bag is available from some manufacturers, but it’s still quite a light-weight piece of equipment.

What I wanted for my own training was something with the same roly-poly action as a bop bag, but which could take a real beating and provide more of a sparring-like experience. As noted, there is a commercial punching bag that works in this way, but I wanted to see what I could make for myself using inexpensive and easily accessible materials. The result is the Roly-Poly Sparring Post.

Here it is in action:

I must say, it is a lot of fun to “spar” with, and it definitely provides a vigorous workout. It’s also quite a different experience from working with hanging bags or striking dummies, and it costs very little to make, so I think it’s a worthwhile addition to a collection of training gear.

To build one, here is what you will need:
* 1 strong bowl. I used a stainless steel salad bowl that I purchased at a thrift store for about $2. Mine had an upper diameter of 18″ and a bottom diameter of 7″, but I suspect that any similarly sized bowl would work.
* 1 old tire. The one I used had a total diameter of 24″ and an inner diameter of 18″, which allowed the bowl to fit perfectly inside it. You can get old tires for free from an automotive repair shop. If possible, try to get one that fits the bowl.
* 2 30kg (66lb) bags of concrete. These cost about $4.50 each.
* 1 piece of 4″ ABS pipe about 5′ long. I found a piece at my local ReStore for about $5.
* 8 pool noodles. These cost about $1.50 each at a dollar store.
* 1 roll of duct tape. You can get a 60 yard roll for about $4 from various stores.
* 2 pieces of black fabric. I spent about $8 on this at a thrift store. If you want, you can skip this or use whatever fabric you have (e.g., an old pillow case and bed sheet).
* Miscellaneous supplies: a flat piece of foam (I used anti-fatigue foam that I had), spray adhesive, 3 screws, and colored duct tape.

The total cost to make this item should be less than $30.

The first step is to make the base and the central post. I did this in two stages. The first was to fill the bowl with concrete (less than one bag), with the ABS pipe sitting in the center. To anchor it in the concrete, I put three long screws into the bottom area of the pipe and I also filled the pipe with concrete up to about the level of the top of the bowl. I let this set for around 24 hours. It is important to keep the bowl on a flat surface and the pipe level and centered while the concrete is wet. You can check it after a few hours and adjust slightly as necessary.

Remember to wear gloves when working with concrete, as its alkalinity can cause serious chemical burns.

Once this had set, I pushed the tire down over top so that the rim of the bowl was inside the tire. Then I filled the tire as far up as it would go with the rest of the concrete (all but about an inch from the top).

I then allowed this second round of concrete to set for about 24 hours. Once hardened, it looked like this:

Here is a view from the bottom, showing the filled bowl and tire:

In order for the roly-poly principle to work, the top part of the apparatus must be substantially lighter than the base. Using a futon or other dense foam won’t work because it will prevent the post from bouncing back to an upright position when struck. This is one of the reasons for using a hollow ABS pipe in the center. For padding, I surrounded the ABS pipe with pool noodles. It took 7 to go around the 4″ ABS pipe. (I also added a piece of pipe insulating foam that I had lying around, but that’s not really necessary).

An easy way to do this is to line up the pool noodles on the ground and then place a strip of duct tape over them in a few places to hold them together. Then, with the tape on the inside toward the pipe, simply wrap the noodles around the pipe and tape them in place. The pool noodles are not long enough to cover the entire ABS pipe, so I used another noodle to fill in the bottom part.

To fill in the space in the top part of the tire, I cut a piece of anti-fatigue foam (i.e., puzzle mat) to fit and placed it over the concrete and under the lip of the tire.

I used the central part of the anti-fatigue foam that I cut out and some ends of pool noodles to cover the top of the ABS pipe (six or seven bits of pool noodle around the outer edge and one in the middle to make it more rounded). Then the whole thing was wrapped in duct tape.

I covered the top part of the post with one piece of fabric (folded a few times for added thickness) and taped it into place. Then I wrapped the second piece of fabric around the post, using spray adhesive to hold it in place. I sprayed about a foot wide section at a time, patted it down to make it stick, and then sprayed the next section, and so on.

Finally, to make everything just a bit more secure — but mostly for aesthetic reasons — I added a few rings of purple duct tape to the post.

The post itself is quite light, but it feels more substantial when striking it because of the heavy base. It tends to bounce back quickly if struck hard, so make sure you practice your blocks and evasions and not just punches and kicks. You will also want to use it in an area with a fair bit of space. If you build one, share your experiences in the comments and maybe post a video of you training with it.

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