Crank Shaft, Derived parts, Engine assembly

To make a simple crank shaft
(keep it simple!)

Before you start - pay attention to your part origin planes and axis.  If you keep everything centered on your part origin, it will be much easier to assemble everything later on. 

You will need some cylinders:
Diameter → determined by your connecting rod
Length → determined by your piston diameter

and something to connect them together:
Center to center distance → depends on your connecting rod, and stroke length.

Save multiple copies of each of the above parts, then assemble them together into one solid part using "Derive".


(**You don't want to assemble them together, it will be a constraining nightmare - so just turn it all into one giant part now)


"Mirror Part" comes in handy when you are first placing the object:


Move everything into place, then combine parts into one solid object.

Note: You can type in equations, instead of just numbers, when you are moving things around etc.


Note - you can always go back and delete Combines, change how far you moved something, etc. from your model tab!

Once you have a good repeating pattern, save it under a new name, and copy it into your part with "Derive".

Once you have everything combined into one part and set, save it with a descriptive file name!  (ie Crankshaft.ipt)

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Constraining your crank shaft to your gears:

Open up a new assembly, create 2:1 Spur gears like before.

Constrain the Crank shaft to the smaller spur gear (not to the assembly origin) so that the spur gear rotates with the smaller gear (two crankshaft rotations for every one cam shaft rotation)


Note: once you get the gears moving correctly, you can increase the distance between the gears, and they will still be constrained to move with one another.  You do not need to add a chain etc.

Note:  Adding working planes & axis to your parts can make assembly much easier!  Although you want to constrain parts to parts (not parts to working planes) for your dynamic simulation. 

Create a separate assembly for your piston and connecting rod:

Import your connecting rod assembly into your gear/crankshaft assembly.

Tip: If you right click while placing your assembly in, you can rotate everything before you set it down.

Make sure moving parts can move correctly!

You can uncheck the visibility on your working planes and axis once everything is snapped into place.

Once your pistons are all in place, create an engine block to put them into.  This might be easiest to do while in the assembly.

Line up your piston vertically
Create →click on the top of a piston →create 2D sketch→click on a sketch plane→create a new part.

Use "project geometry" to line up holes in engine block with the pistons in your assembly.

Ground your engine block, remove any other constraints that are one it, and constrain your pistons to move inside of it.

Getting your constraints right is necessary for getting the dynamic simulation to run correctly!


It might take a few practice runs to get it right - often it is easier to start a new assembly from scratch, than to try and figure out which constraint is wrong.  Practice makes perfect!

Play around with sectional views and appearances to see what is going on inside of your engine block. 

Note:

• Drive → just shows how parts move around
• Dynamic Simulation → parts move due to applied forces.

Temporarily use "drive" to make sure everything is moving correctly, but then delete your drive constraints before attempting a dynamic simulation.

Feeling ambitious?
Add a cam & valves into your assembly!  If you want to create the entire working engine, this can be your semester long project. 


A good site to learn how to put together engines etc. is below, although you need to make your own parts for our engine project!!

http://engineeringexploration.autodesk.com/content/module-5-piston-assembly-example