My newest tool, the Mega Pry!

O

olaf_anderson

Joined
Jun 30, 2012
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13
So here is the prototype of my latest tool and the object of my soon to launch Kickstarter project, the "Mega Pry"! This is a modular tool made of two tools that can be used independently but join together for bigger jobs. One has a normal pry tip and the other has a 90 degree offset tip which enhances leverage by four times (verified by independent structural engineer) and can be used in situations where working space is an issue. Both are 6" x 1/4" (handle sections are 3/4" wide) made of 440c stainless steel treated to HRc54. I chose this material and hardness to give the tools a balanced blend of strength, toughness and corrosion resistance.

The U shaped notch at one end of each tool is 1/2" deep so that when joined the tool is 11", nearly doubling its length. The CNC machined ball grooves reduce weight while simultaneously increasing the tool's structural strength. I designed this tool with active duty military and fire rescue professionals in mind however I am sure everyone will enjoy the power, convenience and versatility of this tool. I will take many more photos and some video once they come back from heat treat and before the project launches. Any questions or comments are welcome, let me know what you think and thanks for looking!















 
olaf_anderson said:
while simultaneously increasing the tool's structural strength
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If your "independent structural engineer" told you this, you need a different structural engineer. :(

But the design overall is interesting and ingenious. I think more people would be interested if it was scaled down a bit for EDC and maybe even made of lighter material such as Ti. Right now it's a bit large for pocket carry.
 
I went to justanswer.com and paid $30 to talk to a structural engineer about this aspect of the tool. What leads you to believe that I shouldn't have spent my money?
 
Removing material cannot make the piece stronger only lighter or have a negligible effect on strength. But otherwise the coupling idea is great to give extra leverage while reducing overall length.
 
If you are talking about the ball groove, it does indeed make it stronger. Its similar to an I beam, the geometric shape is stronger than if no material was removed there, I love science! Yeah, I like the simple joint, no moving parts, quick connect/disconnect.
 
I like it Olaf. The pics that show it without the stonewash look even better to me. Not sure what I'd use it for, but if I did need to abuse a tool, that one would do. Nice work.
 
olaf_anderson said:
If you are talking about the ball groove, it does indeed make it stronger. Its similar to an I beam, the geometric shape is stronger than if no material was removed there, I love science!
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You may love science, but that is flat out wrong. Removing material from a solid bar always makes it weaker. An I-beam is a strong shape compared to other geometry with the same cross-sectional area, but that is not what you are saying.

Another way to think about this: you have slightly increased the strength-to-weight ratio of your tool by adding the grooves, but the solid bar, although heavier, is still stronger.
 
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Cool idea, sort of like linking two flat wrenches together. Have you thought about how well your tool will work if drop forged or stamped? I think having them individually machined would be very expensive.
 
dogstar said:
You may love science, but that is flat out wrong. Removing material from a solid bar always makes it weaker. An I-beam is a strong shape compared to other geometry with the same cross-sectional area, but that is not what you are saying.

Another way to think about this: you have slightly increased the strength-to-weight ratio of your tool by adding the grooves, but the solid bar, although heavier, is still stronger.
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By removing the material you are changing the way stress is distributed on the bar in it's entirety. I think I understand your meaning of strength to weight ratio. But it still should be able to withstand more overall force. Maybe not necessarily to an amazing degree but every little bit is an improvement.

I forsee the easiest way to solve this being make a second one with no milled out section and go through a short number of tests comparing holding weight and possibly weight dropped (to simulate an intense fast motion of stress on the tool) between the both of them and compare results
 
mrnotsam123 said:
By removing the material you are changing the way stress is distributed on the bar in it's entirety. I think I understand your meaning of strength to weight ratio. But it still should be able to withstand more overall force. Maybe not necessarily to an amazing degree but every little bit is an improvement.

I forsee the easiest way to solve this being make a second one with no milled out section and go through a short number of tests comparing holding weight and possibly weight dropped (to simulate an intense fast motion of stress on the tool) between the both of them and compare results
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After milling it is NOT able to withstand more force. But weight reduction is bigger than strength reduction, so strength/weight ratio is better.

When it comes to tests - this tool has SO MUCH material and milling is so small, that it will be very hard to test difference in durability.

Anyway - absolutly fantastic tool. I love the idea and the design.
 
mrnotsam123 said:
By removing the material you are changing the way stress is distributed on the bar in it's entirety. .....But it still should be able to withstand more overall force.
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No. If this were the case, literally everything you see would have a groove cut into it; it uses less material and it is stronger! You can't get something for nothing.

Other than this hard to kill fallacy, I like the tool the OP designed. It shows a bit of ingenuity.
 
Well all the folks who fabricate stuff for a living and have degrees in mechanical and structural engineering are telling me that the ball groove DOES make it stronger. So while I respect your opinion, I will go with the ones from the people with degrees if that's ok.
 
olaf_anderson said:
Well all the folks who fabricate stuff for a living and have degrees in mechanical and structural engineering are telling me that the ball groove DOES make it stronger. So while I respect your opinion, I will go with the ones from the people with degrees if that's ok.
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I do have a degree in Mechanical Engineering. So probably do some of the others here who have tried to tell you the truth. We don't like to brag about it. A student learns this in the first or second year. You are misapplying a scientific concept, that is all.
 
No he was very clear when he told me in the message that "the ball groove will make the tool stronger". We talked about the idea of having it extensively, I wasn't on board at first but changed my mind when he told me that. I may still go with it because its good for weight reduction and I think some people will find the look appealing. I'll ask them again Monday.
 
cross_sections.jpg


You are saying B is stronger than A, yes?

A is stronger than B or C because there is more material. It is also heavier.

B and C have the same area (8 squares). B is stronger than C.

Make calculations here:
http://civilengineer.webinfolist.com/str/micalc.htm
 
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