# Solenoid Motor Strength

Discussion in 'Sensors and Actuators' started by TannerMan, Apr 3, 2020.

1. ### TannerMan

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Apr 3, 2020
Im trying to create a powerful solenoid. I've got 10 lbs of 28 gauge wire which is about 4 miles. Thats alot of expensive wire that i dont wanna waste.
I just wanna know how much pulling force will that create wrapped around a 1 inch copper pipe at about 8 inches from front to back? or a 1/2 copper pipe at 6 in length? Or what would be ideal? I want alot of force.

2. ### WHONOES

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May 20, 2017
The puling force created in your copper pipe will be nil, zero, none. you will need a ferromagnetic core such as iron in the middle of you coil for any force to be generated. The force generated will depend on the ampere turns and average diameter of the coil. The dc resistance of 28AWG wire is 0.15Ω per foot. if your coil consists of 4 miles of the stuff, its dc resistance will 4 x 5280 x 0.15 = 3170Ω.
You will need a lot of volts to generate a substantial force. Ideally you would need to arrive at a reasonable estimate of the number of turns in your coil.
Then you would need a Professor of difficult sums to work out the field strength.

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3. ### Alec_t

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Jul 7, 2015
According to this chart I reckon the maximum current your coil can draw before it starts overheating is likely to be around 1A, in short bursts, since most of the wire will be buried inside the coil. If all 4 miles of wire is used to wind the coil in monofilar manner you would need a supply voltage of 3170V to drive that current!
However, if we assume the coil can be allowed to dissipate only 100W continuously, then the current would have to be reduced to 178mA, which would require a supply voltage of 564V.

Edit:
Interestingly, the chart in the link says 64.9Ω per 1000ft, i.e only 0.065Ω per ft. ???

Last edited: Apr 4, 2020
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4. ### WHONOES

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249
May 20, 2017
The chart I saw said 0.0126Ω per inch which equates to 0.152Ω per foot.
Maybe some of the charts that can be found via google may not be entirely dependable..

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5. ### duke37

5,364
769
Jan 9, 2011
You could look at ludens.cl/electron/transfos/transfos.html
"Practical transformer winding."
Ludens works in modern units only.
He says that 1T is the maximum strength of the field.
You mayl need a steel bar about 30mm diameter to get the field.
The diameter of a coil 150mm long can be calculated with 6km wire. of the approprate diameter.
If the required voltage is too high then several parallel strands can be used.

The pulling force will depend on what is being pulled.

It will not be possible to switch the field on and off quickly.

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6. ### TannerMan

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Apr 3, 2020
thanks for all of the input fellas.

7. ### BobK

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1,686
Jan 5, 2010
Now, how about telling us what it is you are trying to accomplish with your solenoid. There is very likely a better way to do it.

Bob

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8. ### TannerMan

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Apr 3, 2020
i wanna make a solenoid motor like I've seen on YouTube, but i wanna make powerful enough to do some work, like drive the propeller for my raft that i have on my pond

9. ### WHONOES

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May 20, 2017
Which YouTube thread.

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10. ### TannerMan

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Apr 3, 2020

thats just one example

11. ### WHONOES

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May 20, 2017
Have looked at the link videos. I think all the info you need to build a motor is in there. The only thing is, to do any useful work will require quite a lot of power which will have to come from somewhere. How big is the raft?

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12. ### TannerMan

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Apr 3, 2020
the shaft is an inch in diameter

13. ### Alec_t

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Jul 7, 2015
Unless you're aiming for a steam-punk look I think a rotary motor would be far more efficient than a solenoid one.
I guess your propeller is pretty big if it has a 1" diam shaft, so it will need some serious power if it is to be effective. I suggest you do some research into the power required from you motor.

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14. ### BobK

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1,686
Jan 5, 2010
Yep, as I suspected, there is a far better way to do it.

Bob

15. ### TannerMan

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Apr 3, 2020
I recognize that there is better ways to do this, however I like this version and want to see what i can make of it. I also feel that this build is much easier than making a regular electric motor style.

16. ### hevans1944Hop - AC8NS

4,541
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Jun 21, 2012
Amazing! A motor-powered raft for cruising around on a pond! Huckleberry Finn and Tom Sawyer would be proud of ya!

However, if some of us here are gonna help get your project in the water, you need to provide more details and mebbe some pictures of your pond and your raft. How big is your raft? How many people can the raft carry? How big is your pond? How big (diameter) is your propeller? How many blades? What is the pitch? How fast do you want it to turn? How much does your propeller weigh? Is it an underwater propeller or an air propeller? How are you gonna obtain enough electricity to operate your motor? A floating extension cord perhaps? A car battery (or two or three) with a dock-side charger? Solar panels? Hand-cranked on-board generator? A few hundred disposable "D"-sized cells?

Inquiring and (hopefully) helpful minds want to know!

BTW, I second @Alec_t's suggestion of a steam-punk look. You might want to consider using an actual steam engine instead of electricity to spin your propeller. DIY steam engines are fun to build if you have the machine shop facilities available for your use, or can afford to have machining done for you. Of course a steam engine can also spin an alternator to generate electricity that can be used to spin a propeller driven by an electric motor. That's the way the U.S. Navy has been doing it for years and years with nuclear-powered submarines and ships. Lots of advantages with using steam power, at the expense of some complexity and perhaps a steep learning curve. For a raft on a private pond, an alcohol-powered steam engine might be more appropriate than the nuclear option.

Remember, the important thing is to have FUN! Good luck on your project! Feel free to return here with more questions and to supply us with more information. We are here to help!

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17. ### TannerMan

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Apr 3, 2020
Well here is what I have done now, I made a solenoid with 20 gauge wire and attached two 12v 850cca car batteries in series. That means Ive got a 24v system. The 20 gauge wire is about 1200 feet long and comes to about 5 ohms. it is rapped around a 1" copper pipe. My shaft, or piston if you wanna call it that is about one inch in diameter as well. The pulling force is less than 10 pounds. What I'm thinking now is that I may put it on a bicycle in a low gear.

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