solenoid engine research....

[John Hill]

I have been messing around looking for ways to improve on the typical "solenoid engine".


One avenue I have been researching is the best way to add permanent magnets to the 'piston' with the object of gaining a longer power stroke.


My best configuration so far is to make a soft iron/steel piston about twice the length of the solenoid coil, I put a permanent magnet each end, mounted in opposition so that, for example, there is a north pole at each end and two south poles induced in opposition at the mid point of the piston.

The coil I am using is 500 Ohm, 50mm long, 45mm diameter and 20mm bore diameter.

The armature, i.e. "piston", is 18mm diameter mild steel 110mm long.

There is a neo. magnet on each end, they are cylindrical 20mm diameter and 12mm long.

When DC power is applied the piston slides to the end of available travel which is limited by the magnets being unable to pass into the bore.  Reversing the polarity slides it back the other way, almost 60mm.

I used electronic kitchen scales to measure the thrust at different point of the travel and found, somewhat to my suprise, that the force is almost uniform for the entire length of the stroke!

With 20V on the coil the force at the beginning of the stroke was measured at 136 grams, midway 127 grams and 122 grams near the end of the stroke.


I therefore have no hesitation in recommending this form of 'piston' to anyone seeking to build themselves a model "solenoid" engine!

[cfellows]

Thanks for the info, John.  Solenoid engines have always interested me.  One question about your idea.  If you fix a magnet on each end, how do you attach the connecting rod?

Chuck

[John Hill]

Chuck, good question.  I have tried a couple of brass fittings  but really I think the easiest way is a steel fitting that sticks to the magnet.

[John Hill]

I made a little engine to prove my ideas regarding solenoid engines...

http://flic.kr/p/az9wqs



... I dont know why the audio is so loud as the engine is really not quite that noisy..

As you can see this is a two "cylinder" machine and each cylinder is double acting.  That may seem an odd way to arrange things but the double magnet and pole piece that makes up each armature is rather heavy and having two like this tends to balance things somewhat.

The engine can run quite slowly, just a little slower than in the video and it will even run without the flywheel.  I think this demonstrates the long power stroke achievable with this arrangement of the armatures.

It is running on about 24V in the video and it goes quite a bit faster if I wind up the voltage to the maximum of my power supply which is 36V.  The solenoid coils are quite happy and show no sign of heating at 100V which I suspect would be beyond the capability of the very light weight crankshaft I have made in this engine.

[dsquire]

John

That little engine looks like it would have a fair bit of power and sure seems to tick over pretty nice. I'm not sure what I was expecting but I would say that it doesn't look like a solenoid engine. Nicely done John as you always do.
 

Cheers 

Don

[John Hill]

Thanks Don,  the solenoids I had on hand were pretty hunky types and that set the size of the machine.  Yes, I think it would have considerable torque if those coils were getting the 100V or more that they could easily handle.

[Henning]

Great work! An excellent little engine 

[Rob.Wilson]

Hi John 

Very interesting engine you have built  ,, i really like the sound of it 


Rob   

[John Hill]

Thanks for the comments. 

Rob, it really should not be making all that racket!

[DaveH]

John,

That is rather splendid,   I like the sound it makes, not what I would call a racket.
 
DaveH