Tank Suspension
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Hi All
I am making a tank suspension and I have a independant torsion arm test Im working on.
My issue is I want to make the bogie wheels respond to the ground objects. Now I have a hinge where the torsion arm connects to the hull. And a hinge where the wheels connect to the bottom of the torsion arm. Everything is good.
What i was thinking about doing was adding some hidden geometry, adding a spring joint and connecting that to the torsion arm so that if a wheel met an object it would be brought back to its origin via the spring.
This is where my problem lies. As you cannot nest groups with joints because the wheels keep falling off. How can I achieve my desired result?
This image is my test trolley with torsion arms and bogie wheels attached at the rear. I just want the arms to bounce and come back when the run over an obstacle.
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Heres a vid prior to "everything falling apart" with just two hinges.
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I believe I understand your problem, but without the model I cannot be sure. What I belive is happening is that the torsion arms aren't bouncing? I uploaded a model explaining how torsion bars work in sketchyphysics, it can be found here: http://sketchup.google.com/3dwarehouse/details?mid=cb6fcdcf9ab5382e9312901ba4068eab&prevstart=0
it is used for a slightly different purpose here (in this case, a bending rotor blade) but it can be applied to your problem to create suspension for a tank. I hope this solves your problem, but if not then please post the model here so we can take a look -
Thank you for your reply. I cant post the model yet Im at work. The issue is gnawing at me however.
I downloaded your helicopter blade - very well done - thank you. I had no idea you could attach more that one joint to an object. I see it rotate when i press play and bend. How did you make the blade in so many components? Ctrl+Move and then intersect each one? What was the process on that.
But i digress.. I will post the model when i get home in 4 hours.
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what i did was this:
I made a single segment of the blade, then added the two hinges.
I grouped these hinges and the segment together so they could all move together.
Then I used the physics copy function on that new group to create a sort of "Blank blade"
Then i copied this blank blade many times using the normal copy and paste.
I then exploded these new groups and connected the hinges from each segment to the segment next to whichever hinge I was using. For example, if I had Group A which consisted of a box and a hinge, and then Group B which consisted of a box, In order to connect the two then I would simply connect the hinge inside Group A to Group B.
This concept can be applied to pretty much naything, but a word of warning: contradicting joints will not work. What I mean by this is: if you ahve a hinge along the y axis and then another hinge along the x axis connected to the same object, that object will not be able to move at all.
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okay heres my test dolly with the torsion arms and bogie wheels. also a ramp with some minor obstacles.
btw hobbnob thanks for taking the time to reply. im not familiar with the 'physics copy function" is that a plugin?
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No worries mate, I've got a bit of time on my hands so i figured I may as well help out a bit.
The model has a couple of problems, I see now how you have configured the hinges and groups on this and The main problem is the lack of symetry. when I remade the hinge joints connecting the bar to the body I found out that the two sides of the tank behaved very differently. I don't know why this is, because I have rebuilt everything and it doesn't make a difference
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Well I fixed it, but in all honesty I don't know what caused it. I fixed it by exploding the bar all the way to it's bare entities, and then just regrouping it with the hinge. I then added a second hinge above the first and then it worked like normal suspension. Heres the file, thanks for the challenge
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Wow you did it! Thanks my friend this is awesome. I never wouldve figured this out on my own.
How come the two hinges dont cancel themselves out?
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honestly i don't know, it just works and i'm grateful for it
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Man ive looked over your fix and tried to make like-for-like changes to the left side only, on my original, and when i play it just collapses on the left at the double hinge with the wheel up in the air.
Sighs.
Ahh im trying to compare versions in the outliner to see what i did wrong - very interesting
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@hvypetals said:
collapses on the left at the double hinge with the wheel up in the air.
what did you do to copy it to the left side. if you used the scale tool then it can flip it or mess it around. if so what you need to do is explode the group or component and then re-group it. that way it wont flip.
if thats you didnt use the scale too, try seeing if the bars are connected to the right hinge.
if all else fails, ask hobbnob.
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nope i didnt use the scale tool. as soon as i add the second hinge where the bar connects to the chassis - the tire flys off now.
i exploded the arm, which was in two components, and regrouped it as hobbnob did.
i cant seem to add the second hinge without things falling apart.
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Hey wait a second - was something scaled? lol im such a newb its horrible
i notice when i right click on the hinges hobbnob left "reset scale" is available.
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woo-HOOO!!! I got it working!
I just started over. I mustve had something funky going on in my setup hobbnob your were right.
When i deleted all the joints, exploded the tire and the bar and then regrouped them both, then added new joints like you explained and another joint for the wheel and viola - suspension.
man.. i was like a mad sceintist there for a while trying to figure it out
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lol, dont worry, we all get like that at some point when we find a break though. its good to hear you've got it working, its all part of the learning.
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I am going to try and add 5 off these arm and wheel assemblies per side. I have made a component out of the interior wall and arm sockets for the 5 wheel and bar assemblies.
But Im curious what would be the best way to proceed? These are my thoughts
1.) make the previously mentioned wall and socket component a group
2.) bring in the physics copied (now saved component) arm n wheel assembly with joints
3.) explode the arm and wheel assembly component then physic copy the 2 a total of 4 times
4.) explode again both and redo the jointsTHEN..and here where i think my problem is
Then I want to somehow bring that wheel well now with the torsion arms and wheels (assuming it works) and attach it to slot in my tank hull proper.
How do I bring it there as a component and then explode the hell out everything all over again and reattach? Or should i bring into the tank hull scene as a model and then intersect the wheel well now with wheels with the tank hull proper?
does this make sense what i just said?
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errrrmmmm, so are you wanting to copy the arms of the suspension and the wheels.
if so what i find the easiest is to copy it without any joins, so then you can copy it however many times you like and then attach the joints.
or you could use physics copy to copy them with the joint, and then explode the groupe an reconnect the joints (but im not to sure with this method, i havnt used it must before)
-- the way ide go around it, is copying the arm and wheel, then get rid of all joints inside the arm and wheel, and disconnect them from any other joint (so the arm and wheel have no joints inside or are connected to any).
-- then copy and paste the arm and wheel together and place them where they are needed.
-- then finally remake all of the joints again and then re-attach them.if you get confused with this method then just use your own and take your time. and remember save a copy before you start so if it goes wrong, you still have something to go back on.
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Thank you kindly.
Do joints export? Like to 3DS for example?
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the physical joint will, but the mechanics of it won't
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