Author Topic: A Dangerous Accident (Read 1867 times)

theTinker · « **on:** June 29, 2006, 09:51:58 PM »

today i had my frame, rotors, and laminates all set up.

i put my stator board on and put sum spacers between my stator board and my rotor with 12 2"*1"*0.5" and put my shaft and rotor on.i had it all nicely setup but then it happened. the 20+ strips of 3 meter long steel(sharpish) just flew towards the rotor, my fingers were squished and i was'nt sure if still connected. i had to grab a screw driver(lucky it was there) and then pry it open to get my fingers. it took my entire body to pull it out. i was SO lucky about the placement of magnets/fingers. instead of being popped or chopped off only one finger was badly hurt. the way the laminates were pushing against my knuckles meant, the magnets and laminates were aligned so that they were acting on slightly different parts, if not im sure they would of snipped one off. i had to get stiches(small ones) but i could see right inside my finger.

i payed careful attention to holding my magnets in place but i never considered my laminates being pulled off like bullets. an important lesson learnt. though i think im gonna take a long break from my mill. a pity after so much money but prying my fingers out with a screw driver is quite a discouraging memory.

snuffy · « **Reply #1 on:** June 29, 2006, 03:58:48 PM »

A lesson to us all. These things can hurt you and will if they get the chance. Thanks for sharing and reminding us of the power they possess.

Hope your fingers recover soon so you can "carefully" get back to work on the rotor assy.

Murlin · « **Reply #2 on:** June 29, 2006, 05:02:34 PM »

ouch

....

Thanks for sharing, I was planning to some core experiments also.

Gives us all something to think about.

Hope it all heals up ok...

Murlin

willib · « **Reply #3 on:** June 29, 2006, 07:54:38 PM »

Tinker

i hope it heals quick

WilliB

terry5732 · « **Reply #4 on:** June 29, 2006, 09:26:12 PM »

Thanks for not including pictures

stevesteve · « **Reply #5 on:** June 29, 2006, 10:57:24 PM »

Yow!

Not good. I hope that it doesn't put you off but I can see why you would want a few days away from the thing!

I am only working with small neos in my small projects and I do wonder at how folk build disks with 12 or 24 of these 2"x1"x1/2" magnets and stop steel kit wingng around the workshop.

I hope that you heal up quickly.

DanG · « **Reply #6 on:** June 29, 2006, 11:58:16 PM »

I hope you post the crime scene photos - people know $100 worth of fireworks can ruin a good day but magnet discipline doesn't come easy - I've learned those invisible forces of magnetism just didn't get built in our evolutionary consciousness too.

My magnet accidents (only one of which really drew blood) were with magnets half the size you were using attracting sharp stuff at 1/10th light speed... The "Ooooh, shiney, oops, moving, ouch" realization can and will repeat itself over and over, take my word for it, in the same & next minute too!

Time and motion studies, where the attractor will be and what could go wrong, means alot of mental & physical rehearsing how you will do the magnet dance. And having a special room clear of anything that could launch itself after your magnets isn't very exciting to prepare.

I'm sorry you got got but glad you didn't have any little helpers etc. around at the time. I'm casual about alot of things but my neos get treated like explosives. Thanks for posting Tinker...

~

nothing to lose · « **Reply #7 on:** June 30, 2006, 02:59:56 AM »

Glad to hear you still have the same number you started with! I hope they heal fast and you get working on the genny again. Thanks for posting about it, something I never thought of really was a rotor ripping out the steel bands from a backing plate when I was thinking of building a single rotor gennie. That one would have been used pallet steel banding straps laminated into plywood backing plate. I would probably done the same thing. I still may build the single rotor later, your post may have saved me alot of problems when I do.

I put 2 rotors together today and was worried quite a bit myself, but all went well.

I had no way to hold the hub and first 12" magnet rotor down when I was ready to lower the second magnet rotor down onto the first. I put 2 3' 2x4's over the first rotor and wife and daughter held those down while I lowered the second rotor over the studs and resting on the jacking bolts. Then I simply unscrewed the 5" jacking bolts to lower the rotors together.

Worked fine so I can test the coils now with both rotors in place, but I can't do that when the stator is in place after I cast one! So I'll have to build something.

Odd how you can't buy a 6" bolt threaded all the way, only the first 2" maybe is threaded then 3" or longer shaft is not threaded. I'm sure they make long threaded bolts, but I could not find any today! I had to get 1/2" 6"long carrage bolts to use for jacking bolts, was worried about those also. They worked today, but I'll be looking for better bolts!!!

dinges · « **Reply #8 on:** June 30, 2006, 04:09:43 AM »

Hi NTL,

It's not that odd that the entire 6" bolt isn't threaded. If it were, most part of it wouldn't be able to up load anyway. Has to do with elasticity of the steel bolt and how it deforms while under load. That's why it doesn't make sense to completely fill it with thread. There may be other reasons as well.

Don't know if you have any thread cutting dies, but you could try to completely fill with thread. Since the end of the bolt already has thread, it would provide a good starting point for the thread cutting die; it'll be easier to cut a straight thread that way.

Peter.

theTinker · « **Reply #9 on:** June 30, 2006, 05:41:53 AM »

i use threaded rod for all mine and just cut the lengths i want. about 5$ for 2 meters of it.

ye it was a surprise myself that it ripped out, its the same as dans wood AX, i used the steel strapping too if i didnt mention it. i didnt use epoxy so i could of been safer. i made the mould and varnished the inside, i then varnished the strips and put them in. after they were drying i poured lots varnish in, took a few days to set in this thickness but it was hard enough so i could not move it by force. the banding came in groups of 3-4 per 1/4 sec so it was like slicing through the varnish rather than been pulled out in a block....from what i saw i think....

finnsawyer · « **Reply #10 on:** June 30, 2006, 08:23:27 AM »

Re the bolt: Try to find a Fastnal outlet near you. It seems they can get any kind of bolt that you want. They may have to order it.

ghurd · « **Reply #11 on:** June 30, 2006, 03:38:18 PM »

I fingered... I mean 'figured' ... you read it when I warned skipp!

http://www.fieldlines.com/story/2006/6/14/22374/9086

I am down to 7 digits that funtion properly, including thumbs. But I can still count to 10, after several surgeries. None were due to magnetic flux.

It is less amusing when you live through it with damage and Dr. bills!

G-

Countryboy · « **Reply #12 on:** June 30, 2006, 09:00:40 PM »

Make your own bolts.

Buy some allthread rod and cut it to size. Weld a nut on the end of the piece you cut.

If you don't have a welder available to weld a nut on the end of the allthread piece, use 2 nuts jammed together on the end. (Tighten the nuts against each other.) They lock in place and you have a bolt.

chinsettawong · « **Reply #13 on:** June 30, 2006, 10:01:16 PM »

I broke one of my finger bones on my left hand 2 months ago. I was carrying the magnet rotor and I tripped and fell. The rotor hit my fingers agaist the ground. I had to go to hospital and got a few stitches and cemented.

Then 2 weeks ago, while trying to pull off magnets which sticked together, another acciident happened. The magnets were the same size as what DanB used for his big mill. When I tried to pull them apart, they snapped. My right index finger was in between. I had to go to hospital agian for a few stitches. Luckily this time, my bone wasn't broken.

Now I don't really know how to handle these magnets. I have many of them laying around, but I dare not touch them anymore. Anyone can share with me how to safely take the two big magnets apart.

All I can say that, these Neo magnets are extremely powerful and they can be very dangerous if not handle properly (well, even when you think you are handling them with extreme care). Be very very careful.

Wachara Chinsettawong

Bangkok, Thailand

dinges · « **Reply #14 on:** July 01, 2006, 02:26:30 AM »

Wachara,

When you tripped and it broke a bone in your hand, I assume this was due 'only' to the weight of the rotor, not the magnets? If so, here you are, being very careful to keep the rotor away from anything made of steel, walking through the shop but ignoring that piece of carpet that crept up and made you trip (just using my imagination here). Where would we be without mr. Murphy...

As far as safely taking magnets off: I don't think it can be done. I try to handle the magnets only once: when they are to be glued on the rotor plate. Am doing my best to not make mistakes here (triple checking polarity etc.) A bit of extra time spent on this part can literally mean hours saved by not having to remove magnets again.

When the rotor plates are finished, they are stored safely until needed for final mounting. I try to do my trial-fittings of the plates without the magnets present. These things are just too dangerous to mess with.

Oh yeah, for a rotor conversion I'm building, I will have to build a 'fake' magnet out of steel, for trial fittings. Because once I would trial-fit a round magnet in its recessed hole, I have no way of getting it out again (without resorting to temporarily glueing a steel rod to it to extract it again). So, a fake magnet of identical size will be used for trial fittings. (these magnets are just 15x8mm round, BTW...)

Peter

(who's wondering how long it'll take for OSHA to step in and start making laws to protect us from these evil, dangerous magnets. No wait, not OSHA, make that BATF)

Countryboy · « **Reply #15 on:** July 01, 2006, 07:33:03 AM »

Anyone can share with me how to safely take the two big magnets apart.

It can be next to impossible to pull magnets apart once they are stuck together. Your best chance is sliding them apart. Try placing the bottom magnet against the side of a board, and then slide the other magnet onto the board.

dinges · « **Reply #16 on:** July 01, 2006, 08:22:12 AM »

That would be a way to get two magnets apart. But, the fact that they've clashed together at high speed and with great force probably means there's a crack in the (brittle) magnets. You can't see (beneath the nickel plating) nor can you feel it (the two parts of the magnet attract eachother with a lot of force too, just like two independent magnets).

But, there's possibly a crack that you don't know about. And it may show up once the magnet is installed and under high RPM.

Anyway, my point being: if two magnets crashed together at great speed, don't use them for gennies anymore.

I've had it happen to two of my 2"x1"x.5" magnets. I've marked them with a big black 'D' (Defect). They will never end up in a genny. Maybe used in some other, less critical application.

Just my opinion.

Peter.

pepa · « **Reply #17 on:** July 01, 2006, 08:38:35 AM »

hi chinsettawang, take two pcs. of 2x4x12" wood and inlay a magnet into the center of the flat side of each piece to the depth of one magnet. mount one piece of wood in a large vice with the indent facing up and insert the double stacked magnet in tne dado. place the other piece of wood over the top of the other board so that the magnet fits into the dado from the bottom. you can now twist the top board and rotate the top magnet to ease some of the fux bonding and either slide the board toward you or use a clamp to help pull the magnets apart. this worked for me when my grandson desided to look at some 1x2x0.5 n50 magnets that he was giving me. he was lucky that he only received a blood blister and a very big supprise when several lost their plastic spacers and snapped togather. hope this helps, pepa

.

nothing to lose · « **Reply #18 on:** July 04, 2006, 05:52:34 AM »

You may be correct, but I would figure if I want a solid 7/16" shank use a 1/2" threaded bolt, under the cut threads it's still a solid shank

I can see a solid shank for alot of reasons also, like if you want somewhat of a pin type fit etc.. structural stuff too. I geuss most the time strength was not all that important and I used long carrage bolts I got cheap and just cut the threads to length like allthread rods.

I had some dies, 2 different 1/2" threads, one fits the carrage bolts correctly but niether fit the bolts I bought, I did buy some to try re-threading the rest of the way.

I may try cutting a few on the lathe, haven't tried turning threads yet on anything, should be fun.

nothing to lose · « **Reply #19 on:** July 04, 2006, 06:22:49 AM »

Hope the fingers are well now.

Did you use sections of banding like short strips or long ones wrapped around the diameter. Not sure if right or not, I was gonna do mine with a long band wrapped around a few times with a paper insulator between the bands. Use however many bands needed. then encase the hole thing in fiberglass.

That was before knowing about eddy currants and such.

Probably good for me that I got into motor conversions instead of building that one back then.

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Author Topic: A Dangerous Accident (Read 1867 times)