Minibot magnets ?

[Team 1574]

Does anyone used a hard drive magnets in the minibot??

does it strong enough??

MisCar 1574

[Zuelu562]

We had originally attempted to, but we got access to neodymium magnets and left the hard drive magnets in the dust. I can't tell you for sure, but I dropped a hard drive magnet about 2-3 feet onto the top face of the tower assembly, and it landed, and immediately stuck back to the pole.

Depending on the weight, I would assume it's possible to use a number of hard drive magnets, if weight becomes an issue, look into neodymium. Our minibot was like 7 pounds at the end, and we had somewhere around 10+ Neo magnets holding it on.

[thefro526]

816's Minibot weighed approximately 2.3lbs and used a single 40lb magnet spaced approximately 1/16" from the pole.

I'm not sure what a hard drive magnet is rated at, I'm sure they'll work, if you can fit enough of them on your minibot. I'd suggest going to your local hardware store and looking for magnets meant to hold things to tool boxes. Most of them are extremely strong and similar to what we used. If you'd like the Part Number (It's from McMaster-Carr so I'm not sure how much it'll help you) for the magnet we used, feel free to PM me.

[wevets]

A great source for magnets is http://www.kjmagnetics.com. I know they've supplied magnets to other FRC teams because earlier this season they published in their newletter an analysis of the forces involved in holding a minibot to a pole that was very helpful in choosing the right item. That, and they mentioned that they'd had inquiries from several FRC teams.

They have a wide variety of shapes of rare earth magnets at reasonable prices, including magnets that come with countersunk holes, making mounting on a minibot quite easy. They also provide technical info on their magnets on strength, etc.

To answer the question at the start of this thread, one, maybe two hard drive magnets should be strong enough for a minibot, depending on weight and how it/they are mounted and how close to the pole they are when the minibot is running. But the mounting might be difficult given the shape of typical hard drive magnets. Maybe you could drill mounting holes in the steel magnet support, but don't drill into the magnets themselves. Rare earth magnet material, neodynium, is brittle and can break up into powdery pieces that may be toxic. Rare earth magnets such as hard drive magnets and the magnets you can buy from K&J Magnetics and others are usually nickle plated. You don't want to violate the nickle plating. They are mostly perfectly safe as long as you don't try to drill or machine them. I say "mostly perfectly safe" because there is another danger with strong rare earth magnets. They are powerful enough that there is a pinch hazard when you let flesh come between them and whatever they are strongly attracted and close to. I got a blood blister as proof of this. I was just playing around, but it was an impressive lesson.

There are other sources out there, too. Google "rare earth magnets" or similar to turn up a raft of suppliers. At this point, a prime consideration would be how soon they can get the magnets to you.

Good luck!

[yarden.saa]

Team 2630 Emek Hefer used hard drive magnets in their minibot. It worked well but their minibot didn't deploy(other problems).
For more help you can ask their team captains: Ma'ayan Shohat and Gil Kedem.

[kinghashbrown]

Aces High got theirs from K&J Magnetics.

we're using the 20 lb force ring magnets.

we have not yet completed our mini bots but we plan to put two stacks of two magnets.

[SuperBK]

We used the ones from KJMagnetics. They were rectangular and already had countersunk holes in them. We used two twenty pound magnets. I think the ease of these beats taking them out of a hard drive.

[Brandon Holley]

This is what we used: http://www.kjmagnetics.com/proddetail.asp?prod=BX0X08DCB&cat=173 ... They are re-donk-ulously strong.

-Brando

[Jeffy]

It seems many are using lots of force (30+ pound) magnets. I'm sure you can make hardrive magnets work, but the best way to find out would be to make a test bot and try it.

We are using a pair of these: http://www.kjmagnetics.com/proddetail.asp?prod=B884DCS&cat=173
Only ~9 pounds of maximum pull from each, but plenty of pull to provide the traction needed for the bot to climb.

In designing the magnets: create a system in which you can change the distance from the pole easily. For me, it was just add washers.

[jvriezen]

Be careful about using hard drive magnets. If they are encased in some other material designed to mount it to the drive that isn't a legal mini-bot part, you might have trouble.

I believe I also read somewhere here early on in the season that technically using a hard drive magnet means you are using a COTS component (the entire hard drive or the device it came from) and then modifying it (stripping it down to just the magnets) and that technically is not allowed, because Hard Drives are not permitted on the mini-bot. I know it sounds weird, but if you want to be uber-safe, buy a magnet alone, rather than scavenging one out of something else. I doubt a nickel coating or other similar coating that comes with a COTS magnet would be an issue, just because its not entirely a magnet.

There is a chance approaching 1 in 4 that I'll be inspecting your mini bot in St. Louis. I'll be asking deferring to my LRI about questionable minibots, however, (especially if you ask me to!)

John Vriezen
Team 2530 "Inconceivable"
Mentor, Drive coach, Inspector

[Mr. B]

The first "small" minibot that we built used 2 hard drive magnets and worked very well. We used nail polish remover to get the steel brackets off and mounted the magnets with small screws. The next "small" minibot used (1) 28 Lb. magnet from KJ Magnets. The last mini that we built has 2 magnets from KJ --a 28 LB and a 16 Lb. The third minibot is less likely to fly off the pole and damage itself.
My favorite is still the first. As for speed, it is hard to tell, I think the first one is the fastest but when it hits the top, it flies off the pole.

[Cynette]

The first "small" minibot that we built used 2 hard drive magnets and worked very well. We used nail polish remover to get the steel brackets off ...
Nail Polish Remover? We milled the steel backing off of ours. I wish we'd thought of nail polish remover! :ahh:

[spacepenguine]

We used hard drive magnets in our 4th revision minibot. We had to use 5 of them through due to how thin they are. It held well since the minibot was just about 2lbs (~1sec). I just used a screwdriver and hammer to tap the magnets off the bracket =P

[Jeffy]

I just used a screwdriver and hammer to tap the magnets off the bracket =P

Did you do any constructive testing before and after removal to see if the tapping decreased the magnets effectiveness?
Next to extreme heat, hitting magnets repeatedly is the worse thing you can do to a magnet. I wouldn't advise this to anyone.
(but if it worked for you, well done!)

[Ether]

a single 40lb magnet spaced approximately 1/16" from the pole

Here's (http://www.kjmagnetics.com/largergraph.asp?CI=1&pName=BY0X04-N52) a curve of K&J's 44 pound BY0X04-N52 magnet. At 1/16" (0.0625") it's only 2 pounds.

Could you post a part number for your magnet please.



~

[Brandon Holley]

Here's (http://www.kjmagnetics.com/largergraph.asp?CI=1&pName=BY0X04-N52) a curve of K&J's 44 pound BY0X04-N52 magnet. At 1/16" (0.0625") it's only 2 pounds.

Could you post a part number for your magnet please.




You've read the chart incorrectly. At 0.6" it's 2 lbs, it's considerably stronger at 0.0625".


K&J offers a calculator online as well to help determine pull force based on magnet size and distance from the pole.

-Brando

[thefro526]

Here's (http://www.kjmagnetics.com/largergraph.asp?CI=1&pName=BY0X04-N52) a curve of K&J's 44 pound BY0X04-N52 magnet. At 1/16" (0.0625") it's only 2 pounds.

Could you post a part number for your magnet please.




McMaster-Carr Part Number: 7061T11

The magnet was spaced approximately .0625" away from the pole and was more than strong enough to hold our 2.3lb minibot on the pole, though I'd suggest decreasing the spacing to approximately .04" to make the attachment to the pole a little stronger, our minibot liked to fall off on it's way down - sure was fast though.

[Ether]

You've read the chart incorrectly. At 0.6" it's 2 lbs, it's considerably stronger at 0.0625"

Yup, you're right. That's what I get for multitasking.

[Mike Betts]

Be careful about using hard drive magnets. If they are encased in some other material designed to mount it to the drive that isn't a legal mini-bot part, you might have trouble.

I believe I also read somewhere here early on in the season that technically using a hard drive magnet means you are using a COTS component (the entire hard drive or the device it came from) and then modifying it (stripping it down to just the magnets) and that technically is not allowed, because Hard Drives are not permitted on the mini-bot. I know it sounds weird, but if you want to be uber-safe, buy a magnet alone, rather than scavenging one out of something else. I doubt a nickel coating or other similar coating that comes with a COTS magnet would be an issue, just because its not entirely a magnet.

There is a chance approaching 1 in 4 that I'll be inspecting your mini bot in St. Louis. I'll be asking deferring to my LRI about questionable minibots, however, (especially if you ask me to!)

John Vriezen
Team 2530 "Inconceivable"
Mentor, Drive coach, Inspector

John,

The rules do not specify where the magnet comes from. Also, the GDC ruled on hard drive magnets specifically here (http://forums.usfirst.org/showthread.php?t=16822).

Regards,

Mike