Scratch Build – In Progress Trebuchet: Update - Construction complete!

PC + wifi camera on the projectile + some other webcam as a 'sight' on the trebuchet itself + remote trigger = truly epic ownage

 

LOL

Here's a trebuchet --> PC translator
Counterweight = Power supply
Throwing arm = Motherboard/Central Processing Unit
Sling = removable disk drive
projectile = removable disk
base = chasis

 

i was referring to this: Project Logs Rules - Please Read BEFORE Logging

not that i didn't like the project its just the wrong place for it (if there's no pc somewhere on the Trebuchet)

 

Good luck with the project Will be interesting to see what the final performance of this Artillery piece will accomplish once its done and dusted. Amazing to think that The Trebuchet (invented in China) entered service at around the 4th Century and didn't really become obsolete till the 16th. Testament to the great design.

 

I don't think the framerate would be high enough to catch more than a blur even in the unlikely case that the projectile doesn't spin. The camera would also be bigger than the projectile, so it's not happening. It is an interesting idea, though.

You may have been referring to it, but because you didn't provide that link in your original post I just assumed you were either making a really bad suggestion in the form of a joke, or that you had not bothered reading the thread.

Technically, you're right. However, the thread has been up for 24 posts in 9 days and nobody has complained yet. If one of the moderators does have a problem with it, I'm sure they'll use discretion and move the thread to an appropriate place rather than deleting it. As I'm sure you're aware, I don't have the ability to do that.

 

[smartarse]

You could argue, when it says "project log," it means the thread topic, as opposed to to the section of the forum. This thread is under the "Scratch Build" catagory.

[/smartarse]

Anyway, looks good, so when you starting work on the full size one?

 

accelerometers and some kind of tracking widgets then, graph the flightpath!

 

for some small accelerometers and small breakout boards check out:
http://www.sparkfun.com/

A PIC or a small ARM7 ucontroller can easily be built to less than golfball size. Check out www.gumstix.com for some tiny flyinging thingys.

 

Actual Construction, pt. 1

Well, this weekend we managed to get the frame built. This part is now almost completely done. We still have to apply finish to it (going to oil the wood) and do something on the bottom of the base to keep it from getting destroyed if we fire on concrete. We'll probably attach carpet to the underside for a durable, grippy base.


Just to refresh your memory, so you don't have to flip back to page 1 to see what this was supposed to look like.



And this is what it actually looks like! I'm quite pleased with these results.



Everything is attached using T-nuts, right-angle brackets, and bolts.



A shot up the center, where the sling will slide. In addition to being oiled, this portion will be waxed to minimize friction with the sling.



A shot of the main axle and its attachment.



And finally, a shot of the end of the main axle. This combination of washer and hitch-pin will be used on all three axles so the whole thing can be stripped down for easy transport.

 

you gonna have some weight sitting on the two side parts of it to keep it flat on the ground? I think keeping it firmly on the ground should help the launch distance a bit, carpet is too soft i reckon, and would absorb some of the momentum reducing the launch distance a bit. i reckon a thin layer of rubber like the non-slip matt meant for showers would be good as a base. I also think the brackets & bolts would look great painted black, or a dark brown - my 2c

Looks cool btw! nice job

 

ok why not make the pull cord that releases it have a pc mouse at the end as the handle that way if anyone does complain (unlikely as it is the projects to cool to complain about) then it is sorta PC related

BTW I love this project are we going to get to see videos of it being fired ?

 

Have you seen the episodes of the old TV show Northern Exposure, where they launch a, I think, Piano with one?

 

I've got to admit, that's a pretty good use of T-nuts.

 

The side sections are designed to hold sandbags or to have 1-ft stakes driven through them (through the large empty holes) for that very purpose. As for carpet, we were thinking of a very tight industrial carpet like you might see in a cheap hotel - something hard and durable, rather than something soft and thick. That will protect the bottom and allow for slightly irregular terrain like a few small rocks on otherwise clean concrete, but shouldn't allow any movement (in fact, it should be higher friction than rubber). Painting the hardware isn't really an option as it will probably be assembled and disassembled a fair number of times and the paint would flake off. Once the wood is oiled and the arm is in place, if we decide the silver hardware doesn't look right we might transition to socket-head cap screws. The T-nuts aren't removable, so we might as well leave the brackets silver as well, but black cap screws give a nice contrast with silver (and are easier to work in enclosed spaces)

I think a mouse would clash badly with the colors and materials used in the rest of the project, but you most certainly will get videos.

Thanks. It works out really well, because we can set the base down and assemble everything on top of it without ever moving the base and with only a single wrench.

EDIT:
I was looking at my pictures and realized they give you no sense of scale whatsoever. Tomorrow I'll try to take a few more with some reference in them for size, but until then just try to visualize - the frame stands just over two feet tall.

 

make a bigger one out of 2x4's and launch pumpkins for halloween. that would be awesome.

 

thatd be great. have it in the front yard and when kids are walking down the street you launch pumpkins at them. lol

 

i like the sandbag idea better than using stakes - i reckon the bags wouldn't do any damage, maybe just a bit of wear over time
this firm carpet sounds very good aswell, especially when compressed with the weight of the sandbags
and yeah, allthough painting the bolts & brackets dark may look good, it won't look good after some reassembly i'm full of dumb ideas

....and i've got another idea, it would be cool to use a solenoid to trigger a gate or whatever to launch this thing, that way you can have a long cord with a button in the end, and the battery can be clamped to the trebuchet. Better yet, how about making a little remote control! now that would be VERY cool i think. There's at least a couple of guys here that can help you with designing the electronics if you needed it!

 

I've got parts!


Ball bearings for the axles. Like I said, we're all about efficiency and a big part of that is minimizing friction.


The counterweight - it's just a big chunk of iron. We'll be cleaning it up a bit and painting it to prevent rust, but aside from drilling a hole for the axle it's not going to change shape at all. I'd love to round the edges off and clean up the ridges left by cutting on the flat surfaces, but I don't have access to anything like the tools that would take.


Here's the weight sitting inside the frame, in the general vicinity of its final assembled location. Also, since my earlier posts didn't provide any sense of the size of the frame, please note that the white thing in these pictures is a sheet of A4 paper.


And here's the carpet for the base. It's about 1/8" thick and has almost no give, so I'm confident it's not going to rob us of any range.

We hope to start building the arm this week. It'll be a long process, but it will be nice to have it started. First, we have to carve the arm from foam insulation, then we have to figure out how to lay fiber on such a strange shape (it's double-tapered in the long direction and single-tapered on the short end, with lots of compound curves - carbon cloth doesn't really do compound curves). That's all the hard stuff; once we start mixing epoxy and putting cloth on it should only take a few hours, and it has to be done all in one sitting.

 

Whoa, she's looking really serious now, i'm talking WMD status I thought you were just gonna use a 20lb disc from a gym set, but that iron disc is gonna give it a much cleaner look So how much weight are you gonna have in these sandbags? I dunno how much would be enough? I reckon maybe 2 x 10lb would still let the trebuchet wiggle a little at launch, maybe 2 x 15lb or more would be needed to hold her steady?
It's looking very dangerous in a good way btw

 

ive outgrown sketchup. im getting solidworks pretty soon.

Sorry to be off topic, but can solidworks do 2d templates pretty good?

love the project and sorry for threadjack!