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The 12 cent Kettlebell for your 4 hour body workout

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Most gyms do not have Kettlebells (at least the ones I go to) and to buy them is not cheap! I also would like something I can take with me on business trips and not be faced with upset airport security.

Looking online for DIY Kettlebells brings up the standard pipe fittings 'T' bar handle and it is a great solution but definitely not a solution I can take traveling with me.

Here are two solutions I have come up with that have cost me a total of 12 cents!
Below is the video podcast we have made but the written instructions are on the next few pages


Here is the link to the MechanicalMashup website

 

 
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Step 1: First the supplies needed

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The supplies needed are:

1' of 3/4 sched 40 PVC pluming pipe
2' of rope or tubular webbing with at least 700lb breaking strength
1 Linchpin (preferably 3/8 hairpin version)
Work out plate weights

Tools:
Drill with 3/8 inch bit (only needed for one of the two builds
PVC cutter or saw
utility knife (or a deburing tool)
Ruler

That's it!

Step 2: Prep the materials

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First take your PVC and cut a 5" section and a 6" section. The 5" section is for the handle, the 6" is for the weight mounts. DEBUR the inside edge of the PVC THIS IS CRITICAL you do not want a sharp edge on the rope or webbing.

Drill a 3/8 inch hole 1/2 inch from the bottom of the 6" tube

Step 3: Math section

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I know someone is going to give me the "Is it strong enough" or something to the effect that no way could this work and that it is dangerous (and make it seem that this is a threat to humanity itself if used ;) ) in the next section.

So here is the math

To calculate centrifugal force we use this equation:

RPM2 x Radius (in cm) x 0.00001118
  • First a kettlebell swing takes about 1 second to complete one half a full swing or 1/4 revolution This equates to 15 RPM
  • I measured from the floor to my shoulder for the length of the radius of the swing and got 95 cm
Plug this into the formula and you get:

152 x 95 x 0.00001118
and get about 0.2g

So in the worst case scenario in the bottom of the swing we get 1g due to gravity and have to add 0.2g due to the swing so multiply the weight you are using by 1.2 to find out the max force exerted on the rope or webbing.

Most people will not be able to handle a 50lb kettle bell so lets use that as a max weight. 50x1.2 = 60lbs max force

Now knots compromise the strength of a rope but worst case is they half the breaking strength. Lets assume you get some cheap braided rope that is rated at 750 lbs. If you half that you get 375lbs max force. No where near the 60 lbs you can use in a kettlebell. In fact that gives you a safety factor of 6.25!!!!! If you use 1" tubular webbing like in the second build it is rated at thousands of lbs.

Suffice to say this is plenty strong enough!

Step 4: Put it all together

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If you you either know how to tie a overhand weave-back knot and a double fisherman knot. You can skip this step. If not check out the video skip to the time -6:25-  I am not confident I could explain knot tying in text :)



Step 5: Put it all together kettlebell #1


For Kettlebell #1
This is for the home steel weights you may have lying around...
  • Take the 5" PVC handle and run the rope through it
  • Tie the first half of the double fisherman in the rope
  • Push the loop through the second PVC pipe
  • Get the length of the rope needed by having the loop just peak out of the end
  • Tie the other half of the double fisherman and cut off the extra rope
  • Place the weights on the 6" piece of PVC with the hole you drilled at the bottom
  • run the rope loop through the PVC
  • Place the linchpin through the hole in the PVC and capture the loop of rope
  • Tighten the rope with a tug to the handle
  • DONE!

Step 6: Kettlebell #2

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Kettlebell #2
This one is for use with the gym weights that have bigger holes in them
  • Take the 1" tubular webbing and tie a overhand knot in one end (note this is only 1/2 of the weave back knot)
  • Put the tail of the rope through the center of the weights you want to use and through the handle
  • Take the tail end and weave it back through the overhand knot you made in step one with as little webbing (shortest length) as possible
  • Cut extra webbing off
  • DONE!

Step 7: The end!

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There you go two kettlebell builds for 12 cents (because I had all the materials at home minus the 12 cent linchpin, I suspect if you are here on instructables you will be in a similar situation)

If you want to see the build video go to MechanicalMashup and have a watch or watch the video in step 1. ..


DanielM591 month ago

Looks cool! I'm not any kind of engineer/mathematician/mythbuster so I'm hoping you can answer this question. The 5" handle seems a little small. I'd like to get two hands across, like a more standard kettlebell. What kind of effect would that have on kettlebell #1? Like, would the rope be in more danger of snapping or something catastrophic like that? How wide could one make the handle safely? Thanks for the tutorial!!

ballardst2 years ago
good thinking. I've been planning to try the second type with some big cement plates I inherited with my apartment. How well does it work?

I plan on using paracord, so hopefully they plates do not twist around too much.

If knots can reduce rope strength by 50%, and the cord is rated for 550lb (and cheap), I should be eadily able to use 4 or more stands, or there is no reason to not use 8. As long as the pvc is sturdy enough that should remove any safety issues as long as the type does not wear down.

I am tempted to wrap the rope in electrical tape wear it would wear down, but that might stop me from seeing damage to the rope.
MechanicalMashup (author) 3 years ago
That sucks... Well at least if you ever need a lighter or heavier one you will know what to do to save some loot...
ataylor263 years ago
Very cool. And here I went out and bought a kettlebell. D'oh.