Reddit reviews uxcell 12V DC 100N Electric Lifting Magnet Electromagnet Solenoid Lift Holding
We found 1 Reddit comments about uxcell 12V DC 100N Electric Lifting Magnet Electromagnet Solenoid Lift Holding. Here are the top ones, ranked by their Reddit score.
Input Voltage: 12V DC ;Peak Force :100N Holding Force : 75N Duty-cycle (ED%) : 50%; Electric time:Less than 7 minutes ; Thread size : M4*6; Material: Pure IronOverall Size : 30 x 21 mm / 1.2 x 0.8inch(Dia. *T); Lead Length : 24cm/9. 5 inchUse QA-1/155 Varnished Wire, withstand high temperature up to 155C, better than the QA-1/130 in the marketUse UL1332 lead wire, non-deformation withstand high temperature up to 155CUse PA66GF30 nylon plastic for framework; high temperature resistance
TL;DR - The math isn't very accurate, and electromagnet circuits require a few considerations.
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Not an expert, but I did a little bit of searching and found an equation that might be relevant. A lot of the ones we've learned in lecture so far only deal with ideal solenoids. That is, they model the magnetic and electric fields inside the coil. With real world electromagnets, mathematically modeling the field (let alone calculating the force it exerts on a nearby ferromagnetic object) gets really complicated really fast. However, we're in luck.
I did some searching for commercial electromagnets and noticed that a most of them have a specification called "holding force". For some reason, half of them list this spec in kg and the other half list it in Newtons (N). If it's in kg, multiply by 9.8 to convert it to newtons.
The holding force seems to be the maximum force exerted by the EM when in direct contact with a ferromagnetic object, but WE want to know the force at a distance. According to Daycounter Engineering Solutions, the force at distance can be calculated with the following:
Force = (Holding Force Spec)\^2 x (magnetic constant) * (Area of solenoid's face) / (distance \^2)
magnetic constant = 4 * pi * 10\^-7
*Measure area and distance in meters
A quick look at this equation tells me that whatever result we get is going to be a very, very rough approximation. Now for the math.
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Say an average nail weight 15g = 0.015 kg = 0.147 N
We need a magnetic force greater than that to pick it up. Note that this doesn't account for the speed of the bike. In reality, we'll need something much stronger to lift it. Let's double it for approximation's sake.
F (needed) = 2 x F (gravity) = 0.294 = 0.3
We also know that our distance is 2.5" off the ground = 0.0635 m = 0.06 m
Most of the EMs I found on Amazon have a surface area of approximately 0.008 m\^2
Plugging all of these numbers into that first equation and solving for the Holding Force Spec yields:
Holding Force = 104 Newtons (N)
*I'm about 68% confident that this result is semi-accurate.*
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Like I said in my previous comment, you need pretty beefy boi. EMs at this strength totally exist though. Here's one I found on amazon. You might also consider, in a more accurate equation, that you might not be biking directly over the object (reducing it's effect dramatically), the objects' varying ferromagnetic compositions, and the fact that the magnet is moving (relatively fast considering the forces involved). Powering the magnet for long-ish periods of time (10 mins) will also cause it to heat up, increasing the wire's resistance, and reducing the magnetic field. Depending on the bike's battery, you may also need to employ a DC-DC boost / buck converter to achieve the right voltage. And, of course, safety is a big worry too.
Hope you found some of this interesting. I had a fun time reviewing my notes and searching around the internet for this post. Cheers.