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Statistics: Posted by Thomas — Mon Aug 31, 2015 5:47 pm

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madmattd wrote:

I totally missed that statement Dave relayed. I certainly haven't heard about this. An Air Cannon hit that distance a couple years ago, no mechanical I have heard of has even hit 4K yet (officially at least, Chucky III may have in practice for all we know).

KerikM wrote:A FAT did a mile?? Where? When? Whose? Details please!

I totally missed that statement Dave relayed. I certainly haven't heard about this. An Air Cannon hit that distance a couple years ago, no mechanical I have heard of has even hit 4K yet (officially at least, Chucky III may have in practice for all we know).

I remember either in a video or post that they were hitting over 500 mph at the 2013 chunk. Based on a graph that Leonard Vance has in a video, that should get over 4000 feet with no wind. You gotta wonder what the reault would be if they didn't pie on friday with that big tailwind and over 500 mph. They have superior ballistics to air cannons too, that's for sure.

Statistics: Posted by Nick481 — Wed Jul 29, 2015 10:34 pm

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KerikM wrote:

A FAT did a mile?? Where? When? Whose? Details please!

A FAT did a mile?? Where? When? Whose? Details please!

I totally missed that statement Dave relayed. I certainly haven't heard about this. An Air Cannon hit that distance a couple years ago, no mechanical I have heard of has even hit 4K yet (officially at least, Chucky III may have in practice for all we know).

Statistics: Posted by madmattd — Tue Jul 28, 2015 4:42 pm

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Statistics: Posted by KerikM — Mon Jul 27, 2015 8:38 pm

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Statistics: Posted by madmattd — Fri Jul 24, 2015 2:57 pm

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Hi Dave,

We do have this from our archives - I'm not sure if it's currently recognised by our records team but it has been in the past.

The greatest recorded distance for a catapult shot is 415 m (1,362 ft) by James M. Pfotenhauer (USA), using a patented 5.22 m (17 ft 18 in) Monarch IV Supershot and a lead ball on Ski Hill Road, Escanaba, Michigan, USA on 10 September 1977.

Best wishes,

Dan

Community Manager

Statistics: Posted by Dave — Fri Jul 24, 2015 4:31 am

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Dave wrote:

Can you suggest a good link where you can choose any size tubing with a grid and I could build it up?

Can you suggest a good link where you can choose any size tubing with a grid and I could build it up?

Do you mean where you can build up the truss and run stress calculations on it? If so no, I think to get that you have to step up to full engineering CAD packages, such as Solidworks, ProEngineer, NX, etc. ANSYS would do the job too. None are cheap, and they have a pretty significant learning curve if you are new to CAD.

There may be a program out there to at least help you build up a truss to get cut lengths, angles, etc, but I don't know of one to send you to.

Keep us posted, I remember hearing the stories of "endless bridge Dave" but I think you had mostly stopped posting on theHurl by the time I showed up.

Statistics: Posted by madmattd — Wed Jul 15, 2015 11:28 am

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I'm hopeless with computers so I have employed a friend to help me who is very good on the keyboard as also very patient. I will be doing a manual test with the single tube initially so we can compare/confirm and possibly with the built up truss as well.

Thanks for your excellent help so far and I hope I can call on you again later on as I'm certain we will come to some problems along the way.

Statistics: Posted by Dave — Wed Jul 15, 2015 8:36 am

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Check the following link out: http://www.engineersedge.com/column_buckling/column_ideal.htm. Once welded up into a structure, you will effectively have fixed-fixed end conditions, so your "effective length", Le, will be 0.5*L.

You'll need to work through that page, there are different formulas to use depending on the "slenderness ratio" versus a "critical slenderness ratio". When finding the critical slenderness ratio, σy is the yield stress of your column material. Note that I had an error in my formula for I, the area moment of inertia, in my last post, which I have gone back and fixed. You'll have to do a couple of iterative runs to get an idea of the load/length. My hunch is that you will end up as a "short column" setup, which uses Johnson's formula on that page, but you may be able to get away with Euler's after all.

I also found a decent-looking set of lecture notes on this topic that may be of help (it's been a while since I've looked at this stuff. Definitely a use it or lose it type of thing, though it's slowly coming back to me): http://www.colorado.edu/engineering/CAS/courses.d/Structures.d/IAST.Lect26.d/IAST.Lect26.pdf

Or, yea, run the real-life test

Statistics: Posted by madmattd — Tue Jul 14, 2015 7:31 am

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So looking at the truss now there would be the central tube (25x25) plus struts, diagonals and two outer chords on both sides of the tube... The struts would be extended at every 3 metres for the outer webbing.

Hope that makes sense?... Sorry I don't have a drawing to show you for easier understanding as I'm only using iPhone

Thanks for your input,

Dave

Statistics: Posted by Dave — Mon Jul 13, 2015 9:58 pm

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The following link will be of help: http://www.engineersedge.com/beam_bending/beam_bending2e.htm

That is for a beam simply supported on the ends, not with ends locked as if they would resist rotation at the end (which at certain points in a throwing arm would in fact be the case). There are other scenarios at this link, which may be of help too: http://www.engineersedge.com/beam_calc_menu.shtml

You will need to calculate the area moment of inertia for these calculators, which for a box beam is relatively simple. For a solid rectangle where b=base, h=height. You have a hollow rectangle (square actually), so you subtract the area moment of inertia of the "missing" part. So, , where b1 and h1 are the outer base and height, and and are the inner base and height. Since you are using a square tube, b and h are the same, so . Using your 25x25x1.6mm box tube (I assumed those were metric dimensions, so a roughly 1"x1"x1/16" tube), . Watch your units and make sure you use common ones (m vs mm, etc).

Hope that helps!

Statistics: Posted by madmattd — Sun Jul 12, 2015 5:39 pm

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Statistics: Posted by Dave — Fri Jul 10, 2015 5:18 pm

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Time for the 'endless trebuchet'?

Statistics: Posted by madmattd — Fri Jul 10, 2015 3:18 pm

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Statistics: Posted by Dave — Thu Jul 09, 2015 9:12 am

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