Wednesday, 30 December 2020

DIY Cannonball Grips - How To Make Your Own

Something I always wanted to do was make my own set of cannonball grips to take my pull up and grip training to the next level. One of my local leisure centres had a gym rig that had molded on cannonball grips but obviously these aren't portable.

Looking online for some pre-made cannonball grips and well they aren't cheap especially for something so simple. So eventually I decided to dive in and make my own. This post will share with you how I went about doing it, the costs, and some of the setbacks and remedies I came across.

Table of contents

Requirements

Several years ago I saw a video on how to make cannonball grips however I can't remember where at. Luckily the basics of it remained lodged in my memory so I knew what I needed to go for. The equipment needed is incredibly simple and easily attainable:

  • Two baseballs or other kind of hard ball to use as the cannonballs. Whatever you choose ensure they are solid hard balls. See Problems encountered below for why.
  • Two eyebolts at least 4-5 inches long with a good thickness. For mine I choose ones that were 9mm thick.
  • Four nuts and four washers. Two pairs for each eyebolt. This helps keep the ball in place.
  • Two straps for attaching the grips to a pull up station.
  • Two carabiners to attach the eyebolts to the straps.
All the bits needed to make a large and small pair of cannonball grips.

Along with this you only need a few basic items to assemble the grips:

  • Adjustable wrench
  • Drill with a Spade or Spur Point wood drill bit a size down from the bolt. I.e. 8mm for a 9mm bolt.
  • Clamp for holding the ball in place whilst you drill.

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Sourcing the parts

Firstly I went onto Amazon and purchased two Wilson baseballs at £4.49 each. I would strongly recommend not buying these ones. Again see Problems encountered for why.

I also bought a two pack of 6cm diameter Efco wooden balls for £2.70. I bought these so I could try different sized grips to vary my exercises.

Next I ordered a set of Joyhoop Hammock Straps, which came with carabiners for £11.98 (at the time). There are other straps available and for cheaper however I liked the look of these ones and they were also shorter meaning the grips wouldn't end up hanging too low. After receiving them I can currently testify that they are indeed a good job able to support my 79kg body, and the carabiners are good and thick.

I went to the nearest hardware store to look for the eyebolts, however the smallest length they had was 6 inch, which I felt was too long. After driving around a few places I decided to return and just buy them. They cost 90p each slightly more than other places but unlike other places each bolt came with two nuts and two washers attached rather than one. This meant less hassle to find the right sized nut and washer.

I bought five eyebolts, one of which was to be a spare. I intended to glue the balls and nuts into place so needed one eyebolt for each grip. You could if you want use just two eyebolts and swap the grips for a different size for variation however for the cost of the eyebolts why waste the time it'd involve?

As a bit of a DIY enthusiast I already had the equipment needed to assemble the grips so I didn't need to deal with that stuff. So in total (excluding the Efco wooden balls as they are an extra) this cost £22.76. Not too bad, though turns out I could have done it for £19.76. Indeed even less with a cheaper set of straps.

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Making the grips

When it came to making the grips, the process was easier and quicker than sourcing the parts.

Firstly place the ball into a vice clamp. The one I used had a moveable neck allowing me to have it positioned so that I could drill straight down without hitting anything.

The next bit is the hardest bit: trying to drill through the ball so that it goes straight through the north and south poles of the ball. Unless you are using a drill press, which takes the problem away, you will have to depend on human judgement and you will not get it perfect, but you should be able to get it close enough. The drill bit should go through easy enough though there will be some cork dust ejected so do it outdoors or somewhere easy to hoover it up.

Vice, vice, baby! Make sure its tight enough to stop the ball moving whilst drilling.

Once the hole has been drilled through get an eye-bolt (with a nut and washer already on it) and start to screw it through the ball, or vis versa. I found screwing the ball the easiest way of doing it. Keep screwing until you have enough of the bolt protruded through the other side of the ball so that you can place on the other washer and nut. I found the hole a good width and snug fit for the bolt allowing for a tight fit.

After this tighten both nuts with the wrench. For added stiffness to prevent the nuts from possibly unscrewing over time you can apply glue to the bolt at either end of the ball and screw the nuts tight on top of it and then letting it cure.

Give both ends a good tighten with the wrench.

The final thing to do was to simply attach the eye part of the eye-bolt to the carabiner, which itself was attached to the eyes of the strap, and voila! A cannonball grip.

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Problems encountered - 1

Everything seemed to go great. I had done the baseball grips first and thought they looked great. I had orignally screwed the balls to the top of the eyebolts and intended to get the bottom of the bolt grinded off. However after hanging them there was no need for them to be screwed so high considering the height of my pull up bar. A bigger problem with them however was that they felt like if I hung my entire bodyweight off them then the baseballs would tear through the nuts at the bottom.

Checking online it turns out proper baseballs are made out of a combination of cork, rubber and wound string inside a leather skin. Some are simply pure cork. The ones I had purchased whilst feeling quite firm on the outside consisted of nothing but sponge. They bounced well but that was it. At least I can fun with my daughter throwing them about.

Looking around online for a pair of proper baseballs I couldn't find a good cheap ball or trust they had a good amount of cork in them. You could get full cork bodied ones yet I found them hard to find. I also wouldn't be able to tell if they were truly solid until delievered. They all seemed to be over £6-7 each. For something that goes for a couple of bucks in the states, it appears not for the UK. Had I not already wasted £10 on those soft baseballs I may have went for two of these other ones.

A day later I had to go Sports Direct to get my daughter a new pair of trainers and thought I'd chance my arm in seeing if they had any baseballs. I didn't hold much hope but lo and behold they did, and thankfully these Slazenger ones had a solid cork core and for only £2.99 each discounted from £5.99! I would caution that they do also sell a soft ball version, which should be avoided.

Arriving back home I went straight away to drill holes in the two balls and found it a better process than for the sponge core ones. When it came to putting the eyebolts through them it took a good steady screwing action to do so and it was a nice tight fit. After tightening the nuts I gave them a test and bingo they fitted the bill perfectly.

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Problems encountered - 2

Another issue I had was with the Efco wooden balls. It turns out it was next to impossible to screw the 9mm eyebolt through 8mm holes. I tried to find a 9mm flat-wood/spade wood drill bit (external link) of any kind in my local hardware shops however couldn't find anything but even numbered sizes over 12mm. So I had to use my 10mm Spur Point wood drill bit (external link) instead. It didn't matter in the end as tightening the bolts enough ensured the ball didn't twirl around.

Unfortunately the 10mm Spur Point drill bit wouldn't drill through the "pilot" 8mm hole without getting stuck so I decided to drill a new hole through it (intersecting the original hole track). Maybe a Spade wood drill bit wouldn't have had this sticking problem?

Filling in the gaps with some good ol' wood filler.

The gaps and damage to the ball from the original hole I filled in with wood filler. Unfortunately it was white coloured whereas the balls are a natural wooden colour, however I may end up painting the balls anyways. They are untreated wood so would benefit from a coat of something if I use them in poor weather.

After it sets give it a nice sand.

Thankfully the second ball hadn't been drilled through yet so I didn't have the same problems.

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The end product

The finished cannonball grips.
Don't let them dangle too low :-)

Lyle Richardson,
Gym Pal - Unlock Your Potential

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