Trebuchet SIG 2016 Build (season over)

What about running beads just around the corners from the side we need to bend towards? Any chance of drawing it in that way and avoiding the need to grind as completely/carefully?

Tried to draw here, red being warp direction (not to scale), it is warped some in both dimensions, both of the faces in picture will have something sliding over it. Was thinking of running bead where the green lines are.

I was just talking to my Foreman about our plight and showed him the picture.

He said, ā€œcan any of your friends get the bottle refilled?ā€

I have it with me right now and will be near the space this very evening. If someone could get it filled for me tomorrow morning. Save the receipt and I will repay you Saturday afternoon once I get out of work.

What do you think.

Is this the reason that the wide cross-bar thingy isnā€™t level?

I may be confused.

I thought that the warping was really only evident in the vertical elements.

If only I had gasā€¦I used to straighten I beams with heat like that.

Well, my opinion does not constitute the official opinion ā€¦ but today I was standing in the shop and looking at the treb, straight on or fairly close. The arm really does not look level.

And before someone says that itā€™s just the angle of the photograph ā€¦ I viewed it in person. I didnā€™t judge it from this photograph. I was just lucky that @Brandon_Green had uploaded a relevant photo.

I know the floor may not be level, but this looked pretty far off. I didnā€™t have any measuring tools with me to check whether itā€™s square / perpendicular / straight, etc. so it might be OK.

But I think someone who knows these things might ought to look at it. And even if itā€™s not ā€œlevelā€, it might not matter, either.

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Will have to double check that arm pivot axle that the two wheels are mounted on is parallel to the weight axle (4ā€™ steel rod). For that part was mainly depending on the carbide hole saw through the arm beam drilled on bridgeport to align the arm pivot bushing to the arm while welding.

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It always pays to have a second pair of eyes see your work.

I will often overlook my own mistakes.

Keep on double checking!

@Afloyd was kind enough to weld up the end of the arm, so the arm itself is complete, I neglected to take a picture of the full length, itā€™s about 10.5 feet long. I was able to do a pullup off the end of the release pin, which should be more force than it sees while launching.

Was able to unwarp the uprights in one axis by heating it with welding but not the other, so tomorrow will be cutting the top angle iron connecting the sides to expand the width of the slot the weight drops in. Hopefully then the base will be to final dimensions

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Did we happen to get the breaker flipped in the metal shop?

If not I suppose those little Ryobi cordless grinders might work.

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Fixed, the breaker for 120 quad outlet in welding area is in electrical room, panel 3 lower right, labelled Mig

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When we were making those wheels the other day, I was thinking just thatā€¦ Iā€™m not sure you accounted for the hydration of the cement.

But heyā€¦ the more the merrier :fearful:

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Good point. I forgot about hydration & cure time.

Also donā€™t accidentally drop sugar into wet concrete.

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After failing to fix the too narrow weight gap (warped during welding) yesterday, cut the top bars and spread it out to the desired width, adding about 3/8 to the top gap.

But then I welded some more supports near the bottom and the gap immediately closed back up to a 20-30 thousandths interference again. A plausible theory was that the weight of the rails hanging off the uprights is what was causing it to warp, so suspended it by the outside rails

Then sawzalled halfway through the back upright and spread it with a few wedges

Then welded it back together

And at least now the arm can go through its full range of motion without getting stuck.

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And it was a beautiful motion (from ~15 degrees depression - the full motion will likely need additional tuning).

I am anxious to make good on my promise to work on the sling/pouch, but I know you arenā€™t quite ready for that yet. If you can PM me (when you get to that point) and let me know when you are ready to start testing that, Iā€™d love to come out and kibbitz er, participate in that.

We have seat belt webbing, some sketchy 1.5" webbing, and some 3/4" webbing I nicked from the donation shelf. Thereā€™s a prototype from 1.5" webbing that needs to be finished. Suspect we need to settle on a semistandard projectile size - the Bismarck class weā€™re in is essentially defined as >5lb projectile and our model pumpkin might be closer to 10.

Wouldnā€™t our shooting performance be better (and our ammunition cheaper) if we used 6 lb pumpkins?

Will have to experiment with different size projectiles. The question is how to most efficiently transfer energy into the projectile, given that our arm length and weight are now fixed, and the max sling length is dictated by the distance from end of arm to uprights when arm is raised, it may turn out that a slightly heavier projectile works better with the variables we have already fixed.

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I put the money in an envelope in the finance dropbox with a sheet describing it as a donation to the Trebuchet project.

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