First, try out just a basic assembly to get a feel for how springs work:
1st - experiment with springs:
Part #1: Create a base for your spring.
1"
0.1"
0.2"
2"
Part #2:
0.2" - 1"
0.1"
Open up an assembly
Assemble parts #1 and #2 together:
Right click on the base and ground it,
constrain the top to move up and down on the axis of the base:
Environments → Dynamic Simulation → Insert Joint → Spring / Damper / Jack
Component 1: Click on the edge of your base Component 2: Click on the edge of your top
Right click on external loads, define your gravity just click on the axis for the direction
Right click on your spring, apply a stiffness
Open up your simulation player, and play! If the stiffness is set to a good value, it should bounce up and down under the force of gravity.
After playing around with the springs, can you figure out how to make a cam/valve assembly? I'm not going to give you dimensions for this - think about the size of your engine, and see if you can figure out how to make one of these!
You will need 3 parts: your cam shaft, your valve, and a support. Start with a Valve - this is what will let fuel into the combustion chamber above your piston, or let exhaust out of it. Think about the diameter of your piston, and make your valve small enough that two of them can fit above the combustion chamber.
Choose something for your semester project - If you want to finish up a nice engine with timing gears, cam shaft, and valves that would work! If you have another project in mind, that can work too. No class the weekend after thanksgiving. The last weekend in class will be open for you to work on whatever project you would like to do. The final will be creating a simple assembly in Inventor.
Gears in Inventor 1st - play around with gears on their own to get a feel for how they work. 2nd - add timing gears to your engine. Open an assembly
Click "Create", give it a name, then OK.
Open the Design Tab, and have a look around.
Choose "Spur Gear" Gear 1 → Component Gear 2 → No Model
Desired Gear Ratio → Choose 2.00 (instead of 2.4783 - 2.00 is what you need for timing gears)
Calculate: Check a box near Material Values
Choose the material to make your gear out of:
Assign materials to both Gear1 and Gear2
Set desired Gear Ratio, Preview the gears, run the simulations to see how the teeth come together.
"OK" - creates your first gear:
Choose "Spur Gear" again out of the Design tab Gear 1 → No Model Gear 2 → Component
Desired Gear Ratio → Leave what you had it before
Calculate, Ok, Ok, Place your second gear into your assembly:
Now, Play around with assembly constraints. Inventor automatically grounds the first gear you place, Right click on Spur Gear 1, and deselect "grounded" After deselecting it, you should be able to grab gear 1, and move it freely around on your screen.
Each part in the assembly has it's own coordinate system, next, we'll constrain both gears to revolve around the world z axis, by snapping their gear z axis to the world z axis.
Click on the (+) to open up all of the coordinate systems. Constrain Gear#1's z axis to the world origin's Z axis:
Test out your z axis constraint - if you choose a front view (with z pointing towards you) you should be able to rotate the gear around z.
Gear 2 should be constrained around an offset z axis, to see how far to offset it, right click on gear 2, then select "Edit using Design Accelerator"
This opens up the spur gear box again, find the center distance (4.00, or 19 inches, or whatever it is) and copy it.
Next, constrain gear 2's z axis around the world axis with a displacement of (4.00 or 19 or whatever the spacing is).
Just use the "center distance" between your gears. If you forgot what your center distance was, right click on the gear, and select "edit using design accelerator" to re-open the above box.
Click on gear 2, then assemble, constrain, gear 2 z axis, origin z axis, change offset to 4.00 (or 19, or whatever it is), apply, OK.
Test out your new constraints - from a Front view, move your gears around, the 2nd gear should rotate freely around the first gear, always maintaining a distance of 4.00.
Look at the constraints that you have generated in the dialog box, this is where you can go back and change them, suppress them, or delete them if you need to.
Next, constrain both gear's z axis to the xz plane:
The only constraint left, is to make the faces flush with one another:
Constrain the faces of both gears to lie along the xy world plane:
Test out your gear movement, you should be able to rotate each gear about their axis, and they should be perfectly spaced from one another and in line with one another.
Now, Let's constrain the motion! Associate → Constrain → Motion To constrain the motion, we need the gear ratio first, so exit out of constrain motion, and go back to find the gear ratio.
Right click on a gear, Edit Design Accelerator,
Find your gear ratio, copy it (2.4783ul or 2.00ul) Ctrl + C to copy.
Then go back again to constrain the motion, Associate → Constrain → Motion input your gear ratio (2.4783, or 2.00), then select the valley of your largegear first, and then your small gear, choose a reverse solution, Apply, ok. (Note, if you select them in reverse order, your ratio will be 1/2.47 instead of 2.47)
Check your gear motion, moving one gear should now move the other gear as well, but it still isn't perfect! Let's check and fix intersections, and better align our gears:
Inspect → Analyze Interference → click on gear 1 and gear 2, OK
Red areas are interference areas.
Suppress your motion constraint by right clicking on it, and selecting suppress. This will allow you to move the gears independently again.
Now move the gears so they line up with one another:
It might be impossible to get them to line up without interference, so let's move the centers away from one another just a little bit.
Just click on the constraint that separates them by 4in (or 19, or whatever the separation is),
Change the separation distance until you get something that just barely works (not too large of a gap!)
Then go back and turn your motion constraint back on (deselect suppress) Hopefully your gears are now turning with one another, without intersections.
Create a simulation:
Start by opening up another constraint,constrain gear 1 with:
Then this:
If your gears are rotating around the z axis, then link Gear 1 yz plane → World xz plane
Notice the two blue lines for what planes are being linked. Right click on the new constraint, choose drive.
End →360° We are going to rotate the gear's yz plane about the world xz plane along the z axis for one full revolution.
(Note, make sure you chose the gear with the z axis down the center, and not an offset center)
Press play!
Now that you are getting an idea for what the gears look like, think about what sizes would be good for your engine.
your cam should rotate once every time your crank rotates twice...
I made the gears large enough to attach a cam to the top gear that would be above the pistons....
Is anyone up for making timing gears to attach to your engine? Otherwise we'll have to mess with making belts and chains.
Timing Gears:
Think through what diameters you need in order to give ample room between your cam shaft and your pistons.
If you are feeling ambitious - check out some of the chain tutorials -
