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Old 12-07-2013, 06:38 PM   #1
Luke Conner
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Need advice for jerk blocks getting to much bounce

https://www.facebook.com/photo.php?v=476510622467192 (WFS)

If you look at this video you can see what's happening. This is the second set I've made, the first set doesn't have this problem.
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Old 12-07-2013, 10:02 PM   #2
Mike Gin
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Re: Need advice for jerk blocks getting to much bounce

Can you make the tab on the inside that holds them together taller? That might help.

The layer one down from the top is just 2x4's it appears - super light. You can pin them by drilling a hole through each end and then inserting a bolt/rod/pin to hold it to the third layer down. The bolt/rod/pin would need to pass through the tab of the third layer.

Is your upper layer a solid platform? It is hard to tell - I see fewer screws on that one...

Edit - I was thinking - you can always put that 2x4 section on the bottom and experiment - I think the weight of every box on top of that should prevent the thing from bouncing...
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Last edited by Mike Gin : 12-07-2013 at 10:10 PM.
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Old 12-07-2013, 11:05 PM   #3
Luke Conner
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Re: Need advice for jerk blocks getting to much bounce

http://www.endofthreefitness.com/how...ld-jerk-boxes/

These are the plans I used. I'm wondering if it has to do with the tabs. On the first set I made the tabs didn't go all the way to the end. Because they don't go all the way to the end they tend to slide and shift sideways. This set I made the tabs go all the way to the end. They fit together more snuggly, but I think because of this when they do bounce if they don't come right back down in the same spot they don't land on top of each other.

I don't want to connect them together though because I want to be able to restack them at different heights for pulls from the knee or elsewhere.
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Old 12-07-2013, 11:47 PM   #4
Harold Collins
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Re: Need advice for jerk blocks getting to much bounce

First off... Those are Some nice jerk blocks you have there, although I don't have a definite fix , I can share my limited experience building jerk blocks.

I combined details from several sources to come up with my plans ( including end of fitness)

I wanted stackable as well, but can be used without top platform if need be. Although mine are modified version here's an example:

http://www.heaveyduty.com/2013/05/je...pulling-blocks

I found that adding this top layer of plywood, and using these 'top' tabs made the overall structure more secure. And there's absolutely NO bounce. Rogue uses a similar design as well.

Don't know if you'd consider modifying the ones already built, but you may consider something similar in the future.

I believe many of these plans came from Catalyst model, so you may want to compare your plans to those as well.
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Old 12-07-2013, 11:47 PM   #5
Mike Gin
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Re: Need advice for jerk blocks getting to much bounce

I was thinking an easily removable pin like these:

http://www.doublehh.com/cat_images/3...tionHeader.jpg (wfs)

I built these and have the tabs go full width:

http://www.eng.auburn.edu/~simonrl/wl/jerkboxes/ (wfs)

They fit very snugly together. No bounce. You could also experiment with putting some tabs on the side of the shorter layers. I did notice in your video that one of the lower boxes bounced a little bit too. Might want to re-do all the tabs so they go full width. You can use 2x4's for that since they are cheap.
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Old 12-07-2013, 11:55 PM   #6
Mike Gin
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Re: Need advice for jerk blocks getting to much bounce

Quote:
Originally Posted by Harold Collins View Post
First off... Those are Some nice jerk blocks you have there, although I don't have a definite fix , I can share my limited experience building jerk blocks.

I combined details from several sources to come up with my plans ( including end of fitness)

I wanted stackable as well, but can be used without top platform if need be. Although mine are modified version here's an example:

http://www.heaveyduty.com/2013/05/je...pulling-blocks

I found that adding this top layer of plywood, and using these 'top' tabs made the overall structure more secure. And there's absolutely NO bounce. Rogue uses a similar design as well.

Don't know if you'd consider modifying the ones already built, but you may consider something similar in the future.

I believe many of these plans came from Catalyst model, so you may want to compare your plans to those as well.
Nice job Harold! After seeing Rogue's I would re-do mine as well I like their design. The dimensional stability of plywood is so nice those things won't shrink or warp and get all wobbly like with typical lumber. But seeing how much plywood they used in theirs the cost even for a DIYer is crazy.
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Old 12-08-2013, 10:27 AM   #7
Luke Conner
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Re: Need advice for jerk blocks getting to much bounce

I love the plywood on top of all of them. That should be an easy modification. Thanks also for the suggestion Mike, the pins are a good idea as well.
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Old 12-08-2013, 10:44 AM   #8
Harold Collins
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Re: Need advice for jerk blocks getting to much bounce

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Originally Posted by Mike Gin View Post
Nice job Harold! After seeing Rogue's I would re-do mine as well I like their design. The dimensional stability of plywood is so nice those things won't shrink or warp and get all wobbly like with typical lumber. But seeing how much plywood they used in theirs the cost even for a DIYer is crazy.
Thanks Mike. And btw I agree the cost to follow rogues design exactly would be a stretch, my plans called for using both timber ( ends and crossbars) and plywood (side walls/tops).

Luke... Using this design it helps to have an electric planer/sander to ensure those tabs fit snugly (as you have to round the edges down some)
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Old 12-08-2013, 07:47 PM   #9
Brandon Heavey
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Re: Need advice for jerk blocks getting to much bounce

Hey Luke, that is a ton of bounce. Out of curiosity, do you have any supports in the middle of your blocks? I get almost no bounce out of mine (which are the ones that Harold referenced in his post. Also, it looks like most of the bounce is coming from the shorter blocks, have you considered building a couple more taller ones when using them for jerks like you are?

Mike, mine were pretty inexpensive to make and a fun project if you're into that sort of thing I wrote up the costs on my site, you can find an outline here: http://www.heaveyduty.com/2013/07/je...g-block-costs/

Good luck guys!
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Old 12-08-2013, 08:05 PM   #10
Luke Conner
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Re: Need advice for jerk blocks getting to much bounce

Brandon, what's in the center of your boxes from those pictures? Is it just plywood on top with nothing underneath?
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