Use of door magnets for climbing

[Chadfrom7226]

What is the legality of using an electronic door magnet as part of a hanging mechanism? The rules say the pipe is schedule 40 steel.

COUNS Single Door 12V 600lbs Electric Magnetic Electromagnetic Lock Holding...

Here is a magnet rated for 600lbs @ 12V. Someone in the reviews says it takes 350mA which is about 4.2W

The rules say you can use electrical solenoids that are up to 10W continuous. Would this count? Are the other rules that would prevent someone from using these?

Might be a good way to connect/disconnect from a rung

[Peter_Johnson]

The manual says this:

Electrical solenoid actuators, no greater than 1 in. (nominal) stroke and rated electrical input power no greater than 10 watts (W) continuous duty at 12 volts (VDC)

What they are talking about is products like this:
https://www.amazon.com/Tulead-Solenoid-Electronic-Actuator-Electromagnet/dp/B07VC5JKYG/

My read is that straight-up electromagnetics are not (they don’t have a “stroke length”). But this could be clarified with a Q&A.

[Aidan-Mundy]

There is a Q&A up for this already (Q38). Hoping it is answered with something other than “blah blah REFEREE blah blah blah head REFEREE blah blah blah”

[electroken]

It’s an interesting idea. Be sure to think about what happens when the match ends mid-climb and the robot disables. Unless something else is also holding it up, your robot will be on the express elevator.

[Jon_Stratis]

@Peter_Johnson

My read is that straight-up electromagnetics are not (they don’t have a “stroke length”). But this could be clarified with a Q&A.

We’ll wait on this year’s Q&A for a difinitive answer, but as reference, in past years the GDC split hairs on this sort of thing. One used purely for holding was not considered a solenoid, while one that caused motion was. It’ll be interesting to see if they stick with that, or rule differently this year!

[Skyehawk]

There has already been a fair bit of discussion on climbing with (electro) magnets here:

Them monkey bars

For the monkey bar challenge, are the rungs magnetic? Could I possibly use an electromagnet to pull up my robot?

[beedward]

Legality aside, these latches derive their holding force from having effectively zero gap between the electromagnet and the flat steel plate. The force applied to a round pipe, probably not exactly in line with the magnet’s axis, will be far less. Even the powder coating will reduce the force significantly.

[Skyehawk]

^ This

elaborated further on here:

Them monkey bars

I’ve used multi-thousand pound permanent magnetic lifters; super handy! There are some sorta small ones too. Many have a v-shaped area on the bottom to accommodate round stock. The rotate/engage force on mag lifters is non-trivial and goes up with size. The better the pole pieces fit the target, the stronger the holding power. The rating for round is MUCH less than flat. Th PNL0250 is 250 pounds on flat, 125 pounds on 2"+ diameter, 1/2" wall stock. You MUST let it self align; if its not i…

[ChickenSkunk2000]

I think the idea might be to use it for traversing as an easy way to conect and disconnect from rungs?

[GeeTwo]

I strongly suspect that the strength of one of these operating on [powder coated] iron pipe will be greatly improved by a piece of steel which follows the pipe’s curvature more closely.

And as was noted previously, this is probably* NOT a solution for the final rung.

* Long shot: If you can both get this electromagnet ruled NOT an actuator, AND if the switched circuit on the PDH will hold an “energized” state when the robot is disabled, AND ALSO you 're confident in having enough charge left in your battery, you can think about going that route. I would definitely put a physical hook on the traversal bar and skip these three ifs.

[Peter_Johnson]

@GeeTwo

get this electromagnet ruled NOT an actuator, AND if the switched circuit on the PDH will hold an “energized” state when the robot is disabled

I cannot see how an electromagnetic would not be an actuator. For clarity, as you imply, it is not legal to drive actuators with the switched circuit on the PDH (that was changed in R503 in Team Update 1 because the PDH switched circuit state is not controlled by enable/disable).

[camtunkpa]

As somebody who has used these in industry, I’m not going to say they won’t work, but they likely won’t as the 600lb rating depends on correct alignment with the door plate. I’ve tested whether or not the magnet is working with my screw driver and I can easily remove it from the magnet.

[electroken]

I get the concept. I’ve also seen gravity have its way with robots.

[GeeTwo]

@Peter_Johnson

I cannot see how an electromagnetic would not be an actuator.

In principle, I totally agree, but this has happened before. Note also that I put this out as a long shot: that both the GDC rules decisions AND physics had to work out in your favor.

[philso]

Time for some STEM education. The force generated by a magnet is proportional to the inverse of the distance to the magnet cubed. Thus, the magnetic force falls off dramatically with distance. As others have suggested, the flat surface of these magnets is not the best for attaching to a round surface. This is because the distance from the magnet increases as the tube curves away from the contact point.

The weight of these magnets is quite considerable at around 4 lb. Controlling an arm with this 4 pound weight on the end will be much more difficult than controlling an arm with a hook on the end.

It may be possible to make a climbing mechanism work using one of these magnets and I would love to see it because it appears to be a rather difficult but novel way to solve the problem.

[Chadfrom7226]

It’s a power-to-disable-magnet style of magnet

[quad]

I you like magnets, these things exist or make your own custom version.

[Weldingrod1]

These folks offer lifters with better thin metal performance, air switching, and power-to-release magnets

Magswitch Hand Lifter 60-CE - 8800487 - Magswitch Technology

[Skyehawk]

Oof that pricetag.
Still under 600 greenbacks…