Latching with WM2D ?

[mindsweeper]

When I was a young lad my family would go on boating holidays, the cupboards and draws all had latching systems on them.

Pushing a draw in released it and it would slide out normally, pushing it back in would make it latch, no amount of tossing or turning would release it till it was pushed back in.

I would like to model this in WM2D but don't have a clue where to start and if at all it can be done.

Anyone ?

[Fletcher]

The only ways I've found to create catch & latch mechanisms is to use the square pin joint on an object or the rod element function - then you have to go to >properties & the ticked "always" box at the bottom - untick "always" & enter a time function e.g. t>1.0 [that means only activate after time is greater than 1 second] - you can also use < so that it only latches until 1 second is reached then it lets go - the square pin joint with time functions does the same thing but sometimes I find it a nuisance - its's very hard to tell just by looking at the pin joint or rod latch whether it is working so you have to remember what you set it up to do.

N.B. forces can be turned on or off the same way.

N.B. If I want a latch to come on & off periodically I use an IF statement in the time box e.g. IF(t<1,0,IF(t>3,0,1)) - this works fine but I haven't the skills or knowledge to make a latching function that uses say degrees of rotation instead of time - it probably could be done with some sort of script if somebody were to write it, IMO, & then it would probably work as the wheel kept revolving instead of thru one revolution etc.

[LustInBlack]

I'm pretty sure this does make wm2d inaccurate..

Any dynamical or programmed behavior seem to confuse wm2d..

That piece of software is the most awful I ever saw.. The more I use it, the more it's behavior seem to be random ..

It's probably coded in VB, and lacks a good gui, it's not fast and you are limited to 32768 time frame, which is the most stupid thing I saw in the history of computing! .. Wow, you use a signed short to code a time frame?!.. Where are my negative time frames?!

It could at least be 65536 frames, and still then it would be completely stupid to use a 16bit integer instead of going with the cpu native type.. And still, I'm pretty sure there isn't any optimization in there and a bunch of programming mistakes, bad shortcuts and bad programming ..

Anyways, all of this to say, if somebody knows a real good physics simulating software that is still a bit user-friendly, I want to see it!

[Michael]

I'm glad you said it lib because I lack programming skills and it's always good to learn something.

[mindsweeper]

@fletcher

Many thanks for that info, I'll attempt to use your method to latch but as speed increases the timing will all go a skew.

I need to latch for one and a third rotation then release (at a particular point) so I'll have a good stab and should I need any help I'll post the model.

To be able to program degrees would be perfect for my sim so I'll also be looking into this, perhaps post on the D.S.T forum but have never felt comfortable posting there.

@LustInBlack

Yes the application does have it's limitations but I have nothing better to work with before actually modeling for real.

@Michael

I know exactly how you feel.

[LustInBlack]

Yes well, I am also looking for a proper simulation software if someone know of one!?

I know that physical build is better than simulation, but simulation is very very very fast and cheap to do .. I can try my idea very fast and see if they match the movement I hoped for .. I learned quite a bit with wm2d tho..

Btw, I'm also looking for a cheap way to create physical models, I don't want to work with wood, it's too messy, and I am in an appartment.. I do have access to metals but it's at my father's shop and I want material for small builds... I tried k'nex, but seriously, you can't do anything with this garbage.. I would love to have my old constructs kits, these things were awesome!

Anyways, maybe some lego kits would do the job, I could combine legos, k'nex and common material to have a good, cheap and fast platform to base my wheels on ..

First time I did build something, was using heavy metals and it was far too difficult to work with for the price..

I need cheap and fast and precise.. hmm .. ;P

[Michael]

I'm not sure you can get cheap and precise. A mechano set might get you some where but if your doing any custom work you'll have to spend some dough. You could start with a metal cutting bandsaw, these go for around 300.00. I've used aluminum for a lot of the frame structures,gears, etc. I've built. There is a very economical way to cut metal with precision without having to be a machinist or investing in heavy duty machinery. I've used a metal etching kit and it works great. You do your line illustrations in your favorite illustration program, print them out on a transperancy, and then you make a stencil from it using a developer and stencil film. The developer is basically just a halogen light in a box. You then place the stencil on the piece of metal, and the etcher burns the pattern into the metal. You then cut the pattern where you need to. Hope some of this helps, if you want I can post the link to the company that sells the kits.

[LustInBlack]

Mike,

Well I have access to these tools, band saw for metal, wood, MIG welder, plasma cutters, press to cut metal, press to bend metal, grinders, table grinders, wood tools, I have access to everything, my father is pretty much a do-it-all man.

However, I don't want to drive 40kms to work on my wheel, I want to do it from my home ..

Interesting that you talk about etching .. I am making my own pcbs (I am into electronics, programming, mechanics etc etc...).. I don't know if etchant will cut thru a metal plate?! Maybe your method do..

That's something I will look into, thanks!..

Anyways, my idea was to use a hybrid.. Use legos or knex for basic stuff, like support frame etc, and use custom made parts that can be assembled with legos for the precise parts...

I could reuse those parts if it plugs-in with the legos, that would be pretty much the best case...

[jim_mich]

A lot can be done with Balsa wood and glue. Also heavy thick cardboard. Both can be cut with an Exacto knife or razor blade box cutter.

[LustInBlack]

Hmm one thing I was also wondering. . .

Anybody is using this method : Cut layer by layer and glue the wood so that you have a 3D block gutted to specs?!

Maybe my idea is not clear enough.. But I was wondering if it could be a good solution to build precise parts..

Let's say I wanted to build a box with compartments in it, I could just cut 2 rectangular plates and do the sides by making a hole in many rectangular plates, so I would have let's say 20 layers of wood with a rectangular cut in them and glue every layers together, resulting in a closed rectangular box..

This is an idea I had to make precise parts, I wonder if it's reliable.