Calling on Envelope experts (part Deux - transferring info to subassemblies)

Hello Ed,

Trebuchet huh.

As internet savvy as you are I'm sure that the answer is yes, but do you have ATreb, a trebuchet simulator? If not you should look into it; just Google "ATreb" its the first to show up.

I made a nice SW model (model as in small as well) unfortunatly it stayed when I was laid off.

Muggs

Forget a simulator - I have a real one, with a six foot high axle and a 14 foot throwing arm. SWx has been great for working out permutations FAST and virtually. I am in awe of the foks who build good ones with pencil and paper. Using a SWx layout sketch and assembly techniques has allowed me to really try it out virtually and test changes before I even stepped into the shop. I can even set up an equation to calculate the theoretical range (so I can see how efficient I can get - treb 1.0 was about 50% efficient before an eye bolt failed and the tuning/shooting had to stop for the day. Not too good, but it was a prototype) I was cocky enough to go to full scale for my first one - and frankly, lazy (everyone recomends making a scale model first, but that would have taken as long as it took to build the real one and I just didn't want to take the time. I wish I could describe my neighbors faces when I was tuning the release point in my yard with a 25% load)

I am in the process of converting my treb to a whipper-style treb, using the same frame but a brand new arm. The guy who came up with this was just inspired. Instead of going through about 90=B0 of rotation this goes through 270=B0, and with swx I figured out how to get about 360=B0 of rotatation and an extra couple of feet of drop from my counterweight- I built a lego model to check it, and the difference is amazing. Oh, don't get mestarted on trebuchets - it has been a passion for six months now and i could go on and on and on (heck, I just have... must think about productive stuff, must think about productive stuff. Word of warning - don't get into trebuchets unless you are prepared to be consumed by the challenge)

I went to a pumpkin trebuchet toss last Fall and it was amazing (and frightening). There were about 15 full size machines run by mostly locals folks.

Warning, don't park your car behind a whipper-style treb. The slings can let the load go at the wrong time and throw it straight back. I also saw a 20 lbs pumpkin come off it's sling and go straight-up about

300 feet and the then arch backward into the parking lot. Luckily it missed any cars but if I go next year, I think I'll park on the road and not in the lot!

Ed,

I do top down with envelopes using the concept of a master model (I think that is what they call it.)

In one case I had a particularly nasty weldment. Warped plates, nothing touching, everything slightly skewed but using square cut plates. So a surface model of the outer boundary was made and everything in the weldment was mated to it. Before the weldment was even made it was used in the next level assembly to check fit in the model. And in a part with warped (lofted) plates it was used as an inserted part to get the loft right without even having the assembly the loft went into open. In the top level assembly this master part probably showed a dozen times in various incarnations. The affect on mate stability was to make this assembly far more stable than past attempts.

Thanks, paul. So if I read you correctly you dropped that envelope/master model into the subasemlies (and even as an inserted part - interesting...) and had stable results? Did you use this envelope as your primary vehicle for transfering relations between components, or did you go beyond one-degree-of-seperation by making relations not only locally, but having the component of the subassemblies also relate to the next level or even the toppest level assembly (I know toppest isn't a word, but darn it, it ought to be)? BTW - Thanks for the response - my mind has just gotten around to reusuing the envelope in subassenblies, and now I have to consider the value of re-using it by even inserting it in to parts! ( a practice I am initially suspicious of, but frankly I am initially suspicious of everything - until I try it and it works, then I go full bore. One nice thing about having an education in science is that testing theories is in your DNA, and once a theory proves out you can run with it)

Definately off topic now, but what the heck... Thanks Bob for sharing your experience. I would have LOVED to be there.

Tweak> I went to a pumpkin trebuchet toss last Fall and it was amazing (and

Ed - please reassure us all that its just a hobby and use inanimate loads - unlike these guys - and you have no intention of being the payload.

or unfortunately I fear this might happen.

TTFN

Jonathan

I had to get beyond thinking of the part as an envelope because the "envelope" property seems to be the way assemblies handle parts designated as envelopes. An envelop is really just a part.

At any rate the construct in my head for all this is that the master part is just a "fixture", template or measuring device that I can drop into a part or assembly to establish certain relations that are parametrically related through the master part.

My take, with no actual verification...

It should be OK to put an instance of the the envelope in each subassembly and have components DRIVEN from it. Probably best to make sure that any in-context features DRIVING the envelope are in one place only.

This is how I've done it, with most incorrect variations that could be imagined, including multiple-context relations on features in the envelope. This has been very stable, though in-context relations in the envelope obviously should be avoided for performance reasons.

If only we could insert these skeleton parts into other parts and keep sketches, etc....

Why, why, why would anyone user want such functionality!?!?

Clearly, SW Corp knows better,... ya think? They know what the users need and listen to what the users want, surely!?!?!? And, they don't want to waste the users time and efforts by not implementing important workflow tools like data sharing between parts to increase LOGICAL efficiency?!?!?!?!?

.. (pinch me, I think I'm dreaming again)

FROTFLMAO!

Hey Ed,

I tried to email you but the address in the post doesn't work. I wanted to know what the #'s are for your treb so I can put them into ATreb and run a simulation and see how it compairs to what you actually got. I have a jpeg of the dimensions that I would need if your interested. Change "home" to "comcast" in my address.

Muggs