Power for solenoid engine

[jambo88]

I recently built a two cylinder solenoid engine that i was hoping to power with a 9 volt battery. It did not work. I tried the 9 volt, an A23 battery (12 volts), two 9 volt in series (18 volts) and three in series (27 volts). Checked with meter and getting sparks at the contacts, but it won't run. I connected the 12 volt lithium battery from my black&decker cordless drill and the engine runs great. Any ideas on why it works with that battery and not the others? I wanted the battery hidden in the base with all the wiring, etc.

 

[BaronJ]

It is down to the amount of current required to pull the core in !

 

[Chiptosser]

Did you wind the coils, or salvaged from a phone or something else?
It depends on the wire size and the number of winds on each coil.

 

[Herbiev]

As Baron said, it sounds like lack of current. If you have access to a multimeter put it in series with the Li ion battery and check the current. Generally, the bigger the battery, the larger the current it will supply without dropping the voltage.

 

[jambo88]

Chiptosser - I wound the coils myself using no. 22 magnetic wire. The pistons shot into the coils using a 9 volt alkaline battery prior to assembly, but not when everything is together. Here is the address where you can find the plan that I followed: http://blog.modernmechanix.com/a-simple-2-cylinder-electric-engine/#more

I started to think about what Baron & Herbiev said about current. It works with one 12 volt battery but not another. Started to look at battery capacity instead of voltage. My drill battery says its 13.2Wh (Watt hours). I converted that to Milliamp hours so I could compare it with the other batteries. 13.2 x 1000 = 13,200 divided by the voltage (12) = 1100 mAh. My A23 12 volt battery only has a capacity of 55 mAh and a 9 volt alkaline battery has a capacity of 550 mAh. Even though I connected 9 volt batteries in series, that increases the voltage, I believe the capacity stays the same (550 mAh). So I think I'm on to something. A 9 volt lithium battery has a rated capacity of 1000 mAh. I am going to buy one and give it a try. I'll let you guys know what happens.

 

[BaronJ]

Hi jambo88,

In 1932 when that design was published the batteries would have been substantial 2 volt lead acid cells in series giving 12 volts or so and would have been able to supply several amperes.

There are a lot of losses inherent in that design that will have to be overcome in order for it to work satisfactorily.

The coils need a lot more turns if you want to try to run it on 9 volt dry batteries, however you could try eight "D" cells in series. That might give you enough current for a short time.

Whilst this is a simple design it holds a number of gotchas

HTH.

 

[cfellows]

Based on the wire size and the coil form dimension, Your coil has about 850 turns and has a resistance of 2.9 ohms. With a 12 volt power supply the coil will draw 4.3 amps which the lithium battery would have no problem delivering. This gives you a total of 3495 amp turns. The 9 volt battery would not be able to deliver more than about 1/2 amp at most which would give you about 425 amp turns.

Amp turns is a pretty good measure of the magnetic strength of your coil. The 12 volt lithium battery is giving you 8 times more magnetic force than the 9 volt.

I've attached a wire table and coil calculation spreadsheet that you can use to calculate various coil parameters and properties.

Chuck

View attachment WireTable.xls

 

[BaronJ]

Good Morning Chuck,

I'm glad that you confirmed what I'd thought. Though I guessed at nearer 2.5 ohms since cotton covered wire is around 5% larger in diameter and I had neglected to take into account that he had used 22swg enameled wire.