In the past, I have already made a few different solenoid engines.
They were pretty cool, but you needed a lathe to make them.
Not this one!
In this video, I'm going to show you the steps of how to make a solenoid engine yourself without a lathe.
I am Emiel, The Practical Engineer. 
Let's go!
The coil is the most important part of the solenoid engine.
Without this, it wouldn't be a solenoid.
In my previous builds, I made a special bobbin on the lathe.
But today I'm going to wrap the spool around this tube with an inner diameter of 6mm,
and two end flanges that I printed.
In my first solenoid engine, I wound the coils on the lathe,
but on second thought that was not such a safe idea.
That is why I made this simple tool for the V8 to be able to wrap it with the drill.
The chosen wire diameter and the total length of the wire determine the voltage
at which the solenoid engine will run and how much current it will require.
You can calculate exactly the number of windings you need,
I like to take the thickest possible wire but which still provides enough resistance.
I like to get a resistance of 4 ohms.
In this case, I use a 0.5 mm wire of about 45 meters.
That gives me a resistance of 4 ohms. 
It's 3 amps at 12 volts.
When winding the coil, make sure that you leave enough wire at the beginning so that you can connect it later.
And that you do not damage the coating of the wire during winding.
Then you get a short circuit.
Also, make sure that you never hold the wire in your hand in a way that it can pull you along.
I hold it very loosely here, and if it gets stuck, then it pulls out of my hand.
For the plunger of the solenoid, I use a piece of 6 mm round rod of normal steel.
Here I sharpen a flat side, and I drill a hole with a thread so that I can attach the connecting rod to it later.
I make the plunger so long that it is still comfortably in the coil in the furthest position.
But in the shortest position, it should not protrude from the back.
And before you continue, this is a good time to test the operation of the coil.
It is now a lot easier to fix things than when everything is in place.
Because this solenoid engine has only one cylinder,
it has to go back to the extreme position due to its momentum.
That's where this flywheel is needed for.
In the previous versions, I made them from aluminium and brass.
For this one I printed it and I use these bolts
to give it the necessary weight so that it has enough momentum to keep the solenoid moving.
For the base of this solenoid engine, I printed this block
in which I put two bearings for the central shaft.
On one side there will be the flywheel and on the other side this eccentric where the connecting rod is attached.
But of course, all of this has to come together and for this version, I made it on my CNC mill.
Of course, you don't, I also have this model available as a 3D print,
but you can also make something by hand.
I make the connecting rod from a small piece of aluminium.
With this template, I can easily drill the holes in the right place and quietly auction the rest out.
I did this in my previous videos on the band saw but I got quite a bit of criticism about that.
And you were probably right there, so today I'll do it with a file.
You can choose different options to switch the solenoid on and off.
In this video, I use a simple limit switch.
A switch like this often lasts about 1 million clicks.
For me, that is not such a problem,
but keep in mind that 1 million may seem like a lot, but is not so much.
At 100 rpm it will last for about 166 hours,
and at 1000 rpm it is already finished after 16 hours.
So think about this for a moment.
You can solve this by making a switch yourself with pieces of copper wire,
like I did in my first version.
Or by doing it utterly contactless with infrared sensors.
The solenoid as I made it now draws about 3 amps at 12 volts.
This is quite a high current to switch like this,
and the switch will not like that very much. May even weld itself on the inside due to the sparks.
To prevent this, you can solder a small circuit with a MOSFET and a diode.
The MOSFET ensures that you only switch a small current with the switch,
and the diode functions here as a flyback diode
and allows the rest of the current to drain from the coil instead of to the MOSFET.
You can find more info about this in the blog which you can find in the description of this video.
But for now: Let's test it!
I have tested this solenoid engine with two different batteries.
With a 3s battery, which gives about 12 volts
and with a 2s battery which gives about 7 volts.
You can see that it reaches about 500 rpm at 7 volts.
At 12 volts it goes a lot faster and reaches over 800 rpm.
But it gets a lot hotter at twelve volts, so the lifespan will probably be a bit shorter.
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because there are many more fun things to come!
You can download the models to make this yourself on my website.
Until next week!
