Need help cnc plasma cutting trigger for trebuchet

Would anyone of the trainers / installers be willing to cut the following out on the cnc plasma cutter for the trebuchet project? There is a 2’x2’ sheet of 3/16" steel plate leaning up against the trebuchet uprights in project storage to use, I will be around thursday night or cutting it anytime someone gets a chance would be great.

DXF File

Idea is that the 3/16" plate will be doubled up to create the trigger (the mounting plate is welded to the structure), almost all the load (up to 1,000 pounds) is carried mostly through the 1/2" pin/bolt, which is slightly offset from the center line, so in theory it should take only a small force to release the latch.

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FYI

DXF is a unitless file format. What unit did you export your DXF in?

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Inches, for reference the small holes are .25 and .125 inches in diameter (half final, was going to drill them out after cutting), in total it’s about 23 x 13 inches

We need to get the higher amp consumables, right now I believe we only have the lower amp. I’ve been meaning to go by airgas & see if they have some. The good thing is I need to get some screen captures for the content for the upcoming classes. Do you have a reference as to how big the parts are besides the holes? Also for the ones you are doubling up, do you want to cut holes for rosette/plug welds for more weld surface area?

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By the way, we have an empty Airgas cylinder by the back door for over a month. If you contact them please let them kbow to retrieve/exchange it since we are paying rent on it monthly.

Thanks!

BTW: @JayJohnson600 was getting screen captures and working on a training video (??) for this class.

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The slots/large half circles are 2 3/8" wide

That looks like a scaled up version of the independent releases on the scale model. Do you have some means of synchronizing their operation?

Friday I did some cuts that were dimension sensitive. They turned out ok. What I will do is position the torch in those two known positions to verify the size.

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I’m happy to help. There’s likely a normal tip around somewhere. If not, we can just crank the amps up. The tip on there currently has apparently already been run at like 50 amps (rated for 30 amps) so it’s toast anyway.

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Hopes and dreams? The trigger will probably be the hardest thing in this build, which is why getting it created to test out on the gantry before installing it is important.

Synchronization is critical, if one releases and one doesn’t at full weight it will be hanging from one side and likely break itself. Attempt one will be using the door lock actuators wired in parallel (the movement of top hole on small latch is .53 inches, within the .75 inch actuator range, and hopefully requiring less than 5 pounds of force to pull), and hoping that the cheap chinese motors in them work close enough to simultaneously when supplied with the same voltage.

Attempt two if that doesn’t work during testing will be to use something like bicycle brake cable to try and mechanically link them(which is how the small scale is setup right now) so that you are pulling from a single location on both latches.

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I picked some consumables up from Metroplex welding supply. They have quite a bit of consumables. We should do some sort of dividers to separate the 60 from the fine cut & 40 amp consumables.

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Maybe Consider Heavy Duty Snap Shackles used on large sailboats. They will easily carry that amiunt of load.

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Ok, the holes are being interesting. About the best I can get out of the .125 is .150"ish. The .25 is a tad over as well. I presume this won’t be an issue?

That would be fine, in the drawing they are half size of the final OD, was planning on drilling them out on bridgeport after cutting

You bore on the Bridgeport. Drill on the Clausing. Ream on the bench. :wink:

Intuitively, looking at this design, I think it could hang. I think you need to put a slant into the hook where the pin is pulling against it.

I’d be worried that the plasma cutter will harden the steel. At a minimum I would anneal it before attempting to drill.

Fortunately, low-carbon steel like what he’s cutting doesn’t harden. That can be proven with a file after cutting.

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If it is common cold rolled stock, the plasma cutter might actually anneal the stock. Especially since I don’t think any quench is being performed. I would suggest a file test after plasma cutting to start with and see if it needs to be annealed.