Ofsetting surface on piston design

I am making an assembly of a motor so that I can cut out the topography of the piston based off the cam profile where the valves and piston are at there closest point to each other.


What i need to do though is then offset the surface by a chosen amount so the piston is a safe distance away from the combustion chamber and valves.

 

I am trying to figure out what the easiest way will be to accomplish this.
In the assembly I managed to subtract the shape of the head and valves from a piston plug but haven't managed to figure out how to offset the surface of the solid.

Is this the way to do it and if so how do I offset the shape of the solid?

I tried using the surface offset but it resulted in unsupported features. 

 

Or am I better off creating an offset surface off the valves and head and then trying to turn that into a solid?

6 REPLIES

Re: Ofsetting surface on piston design

Phenom
Phenom

If i understand you correctly this is pretty straight forward.

 

You need to use the OFFSET command in Surfacing...watch here: http://screencast.com/t/2jtiBDZX

 

This is a very simple example but I'm sure you can use this to work with in your assembly. But remember you can direct the offset in either direction, so in your Piston Example you can select either part and use the proper direction to give you the clearance.

 

And once this is OFFSET Surface is made, you can use a Boolean command to remove mateial from the Piston.

Re: Ofsetting surface on piston design

Ah I hadn't thought about that.

So make a surface offset x amount from the combustion chamber then use the surface to make the cut in the piston.
I'll give it a shot.

Thanks

Re: Ofsetting surface on piston design

PLM World Member Phenom PLM World Member Phenom
PLM World Member Phenom

Hello,

 

This is a little off topic, but I'm glad to see you are checking for clearance between the valve and top of the piston.  There are so many engines out there these days that don't have clearance designed into them and when the timing belt breaks, you can say goodbye to the top end of the engine when the valves and pistons crash into each other.  I have never understood the logic of manufacturers not providing relief pockets other than the pennies it costs to machine them into the pistons.  It's not IF the timing belt will break, but WHEN.  When was the last time you heard of a small block Chevy breaking a timing chain?

 

Kyle

Kyle Joiner
IPA LLC
ST10 MP1

Re: Ofsetting surface on piston design

Legend
Legend

I think it may be due to two things- one, squish and compression ratio are very important to modern combustion chamber design necessitating very tight clearances, and two, deep pockets increase surface area causing undesirable heat absorption by the piston crown. But what do I know- I race a two stroke ;-)

Using SE since V12, 2002

Re: Ofsetting surface on piston design

PLM World Member Phenom PLM World Member Phenom
PLM World Member Phenom

I figured they didn't want to spend the money on machining valve relef pockets in the tops of the pistons and put the responsibility on the consumer to change the timing belt.  Smiley Happy

 

You race two strokes?  I hope it's not a Trabant. Smiley Wink

 

Kyle

Kyle Joiner
IPA LLC
ST10 MP1

Re: Ofsetting surface on piston design

Legend
Legend

Yamaha RD400 in vintage road racing. My avatar is a shattered piston from it.

Using SE since V12, 2002