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Registered Member #3258
Joined: Wed Sept 29 2010, 06:25PM
Location: Ascot, UK
Posts: 25
Navrit - Just so you know that wire is really, really hard to wind. I just used exactly the same one and wound it round a allen key of the same diameter - i have a feeling it will crush any plastic tube you wind it round.
Registered Member #3323
Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116
Alex, I know what you mean, I was trying to bend the wire a few days ago and it really was hard, i think you could solve the plastic crushing problem by temporarily inserting a metal rod and then wrapping it around. Which size did you find best for your wire? Just so you know, I'm doing this for my A level Extended Project. Are you doing it for an Extended Project as well?
Registered Member #3258
Joined: Wed Sept 29 2010, 06:25PM
Location: Ascot, UK
Posts: 25
Alex Smith wrote ...
...and wound it round a allen key of the same diameter...
;)
Nope this is for my A2 coursework actually, I didnt really have time to do an EP (and my college does its own version which dosent count as an AS - long story). Im using a 5mm diameter ink cartridge from a pilot g1 pen or something to that effect, i reckon it'll be a good fit for nails.
Basically when winding i used and allen key (with a 90 degree bend) and started by doing a couple a turns. Put the first bit of excess across the perpendicular part of the allen key so that the coil dosent slip when you wind. Then hold the reel along way away from the allen key and wind tight in a sort of pedalling motion with your hands. If this makes no sense I completely understand. But in general just GO SLOW! once your bent it, it really is difficult to alter it again.
Registered Member #3323
Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116
I didn't think coursework could ever be that good
I think I just about understand what you are suggesting, as in the whole pedalling motion thing. i think I'll find a plastic tube, then put an allen key (for example) inside
Registered Member #3323
Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116
I know I have kind of already said this before, but I am going to try and make an aluminium 'V shaped' mechanical switch, I would use copper, but it really is too expensive, and I can't obtain the datasheet for my SCRs, even from the company who made them... so I'm not risking them all blowing up in my face
The limit for the height of the switch will be determined by my DT departments capabilities, since aluminium is relatively soft, I hope it isn't too much of a problem. Alternatively I could go for a more scrap based approach and get 3 aluminium blocks that overall have 3 slots.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
That ghetto diode seems a recipe for disaster, unless your plan is to burn half until only well matched diodes remain ... most modules can handle that surge current outright. Or if it has to be cheap at least use some P600x or 10Axx diodes.
Registered Member #3323
Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116
Is there any way to make the current sharing more ideal? Isn't one way to add equal value resistors to one side of each diode and solder all of them to one point, that point is then the contact point. Please correct me if I'm wrong, but if you do it would be nice if you explain in detail
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
A ~0.1 ohm series resistor per diode would ensure static current sharing, but not dynamic ... but that's probably not important here since dV/dt is relatively low.
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Coilgun Questions
