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ankurpraja

3 stage hydraulic cylinder

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ankurpraja

Hello All,

I am completely new to 3DS Max. In past i have used it to do some basic rendering. So apart from that i know nothing.

 

hyd.max

 

I want to animate an assembly which has a 3 stage hydraulic cylinder. The modeling was done in inventor and then imported as meshes in MAX. Unfortunately all the constrains created in inventor are lost during the import and i have no idea how to make similar constrains in MAX.

 

Please HELP.

 

Thanks in Advance.

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lrm

It looks like you saved the Max file with version 2015. I am using 2014 so I cannot open it. Please save the file in an older format if you would like me to look at it.

 

From the thumbnail that I was able to see it looks like you have a cylinder within a cylinder. Since you are new to Max I suggest you avoid using IK (Inverse Kinematics) and Bones. They will give you a dynamic relationship between the components of your system but that may not be necessary for your needs. Depending on your desired output (e.g., an animation that looks good), you might find it easiest to just use simple object linking an manually position the parts for each key frame.

 

The first thing to do is to move the pivot points for each object to a logical location of the Max part and align one of the part's principal axes with the hydraulic cylinder's axis (go to the Hierarchy tab, Pivot, Affect Pivot only). Next position the parts in Max in their initial position. Use object linking to link the inner cylinder to the outer cylinder then lock two of the Move axes - not cylinder axis, all 3 Rotate axes, and all 3 Scale axes. MOve the time slider out to your first key frame and turn on Auto Key. Now reposition the two parts and you have your first key frame.

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nukecad

Not to do with 3Ds max, but to do with the way multi-stage hydraulic rams work to give the realistic look.

 

With a multi-stage hydraulic cylinder the largest inter tube extends fully, then the next largest, and so on.

Retracting, eg. under gravity, is the opposite, smallest all the way in, next smallest, etc.

 

This assumes that they are standard single acting rams, but if you are doing something special like a single acting with a double acting first stage then I would expect you know this already.

 

EDIT

This was also assuming that the rams were acting in the usual way to PUSH against a force.

Having now seen the OP's project he is using them to PULL a platform into place in which case the sequencing order of the tubes will be reversed when retracting the rams as they will be powered and not under gravity. (see later post).

Edited by nukecad

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ankurpraja

Hydraulic Cylinder_01.max

 

Hi,

 

See attached model i saved in 2012 version. Imported from Inventor.

I want to animate it exactly as shown in this video. Only difference is that mine is 3 stage.

 

Cylinder Animation.jpg

 

Also, see the attached picture showing what exactly i want the cylinders to do.

Sorry for the crap render.

 

One more quick question. On the lower right corner of the picture you can see the dark area under the shadow. How can i illuminate that area. I tried using different types of light but not able to do it.

 

I am using only one light in the model and that is Daylight system.

 

Thanks.

Cylinder Animation.jpg

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nukecad

The youtube video looks more like shock absorbers than hydraulic rams.

 

Whoever has animated that 2 stage one has made the common mistake of showing both size inner tubes moving at the same time.

Multi stage hydraulic cylinders don't behave like that unless there is something wrong.

 

(I worked with hydraulic cylinders for years, single stage, multi-stage, single acting, double acting, s/a with d/a stages, etc,etc.

As well as cylinders for our own tipper trucks, we made them for the likes of CATERPILLAR, JCB, HIAB, FIAT-ALLIS)

 

The jpeg of the rig shows twin hydraulic rams, double acting if they are raising and lowering that platform.

Just looking at the general geometry there then, yes they would have to be 3 or 4 stages.

 

When lowering the platform (extending the rams) as this is under power the sequence would be largest diameter tube out first, next largest second, etc.

When lifting the platform (retracting the rams) as they are pulling against platform the sequence will be the same, largest in first, next largest second, etc.

 

On a design note; the way you have the rams positioned means that you are using the cylinder retract to lift the platform.

If you could have positioned them underneath then you would be using the more powerful cylinder extend and could specify a smaller cylinder to do the same job. (Of course this would mean that the tubes would be extended all the time the platform was raised).

 

It's all to do with oil pressure and area, when the oil is pressurised it is the same throught and so the cylinder with the largest area moves first against an opposing force until it comes to the end of its travel, then the cylinder with the next largest area starts to move.

The difference between extend force and retract force for the same sized cylinder is typicaly X5 to X8, see the figures on the attached

http://www.edbro.com/Portals/43/Images/RK171TS504628001.pdf

 

(Flippin heck; I drew that 20 years ago and its still on their website, I've worked at two other companies since).

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lrm

Assume the hydraulic cylinder is composed of three parts, the outer, inner and middle cylinder. The local Z axis for all three is the axis of the cylinder. The pivot points of the outer and inner cylinder are at or beyond the end of the cylinder. Note, your original model for the cylinders includes a clevis hole detail. This detail may not be necessary as it might never be seen in the final animation. I’ve left them out in my sample solution.

Hydraulic-Cylinder-iso.JPG

Position the inner and outer cylinder so that their z axes are coincident.

 

Select the outer cylinder and click Animation, Constraints, Look AT Constraints and then select the Inner Cylinder. In the Motion tab change the Select LookAt Axis to Z. This should align the axes of the two cylinders.

 

Snap a dummy object (from the Create tab click Helpers) to the pivot point of the outer cylinder.

 

Add a LookAt constraint to the inner cylinder that looks at the dummy object. Fix the LookAt axis to Z.

 

You should now be able to move the end of the inner cylinder and the outer cylinder will follow its location. The next step is to add the middle cylinder.

 

Align the middle cylinder axis to the outer cylinder axis by selecting the middle cylinder and clicking Tools, Align, Align… when the Align Selection dialog box appears check the Z-axis for Align Orientation. The Middle Cylinder should now be in line with the inner and outer cylinders.

 

The location of the inner cylinder pivot point will needs to be linked to a point on the platform that is pushed up by the hydraulic cylinder system. Add a dummy object at this point and then link it to the platform.

 

Now we need to link the inner cylinder to the dummy object you just added. To do this first select the Inner Cylinder and then go to the Animation tab, Constraints, Position Constraints and then pick the dummy object.

 

You should now be able to rotate the platform and have the Inner and outer cylinders follow accordingly. You will need to manually adjust the location of the Middle cylinder with respect to the other cylinders via key frames to behave the way you want (e.g., the middle cylinder fully extends before the inner cylinder starts to move).

 

I've attached the Max file. I created a .mov file but cannot upload it as it is 2 MB (greater than the 0.5 MB limit here).

Hydraulic-Cylinder-rigging.max

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ankurpraja

Thanks guys for all your support. Just managed to do it. Not exactly as i wanted but its OK. I don't want to spend more time on this. I followed the method shown in this video.

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lrm

That is an excellent tutorial. I am glad you found it. It does not address the concern nukecad raised as it splits the distance for the middle cylinder rather than making it extend all the way before the small cylinder. You could address that by manually key framing its position.

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