Wire firer

[Dr.EM]

I mentioned this in a previous post, but I have a digital camera now so I thought i'd get some shots of it.

It uses compressed air from the lego pnumatic system to fire :shock:. In fact, it is all lego apart from the barrell which is two empty ink tubes from ordinary biro pens (1mm diameter internal approx). The triggering is important here, so i've used two valves in parallel, operated by a fairly powerful spring, it goes off by pressing a button. The highest measured speed was 74m/s, though it tends to be 50m/s.

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My new digital camera has a 1/2000th second shutter speed which, with some difficulty, allowed me to capture these images of the wire projectiles in mid flight. I couldn't do it at full speed (I was basically pressing the shutter button and the fire button at once and hoping for the best) so there is a shot of 3 at once, and of a projectile just exiting the back of a folded sheet of paper.

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Thought you people might find this intreresting

 

[Someone Electro]

Its easyer to catch it on mid air whith an video camera and then find the frame.

Even wen filming whith my webcam i had truble catching it in mid air wen going at 30km/h(and 30 fps).If if the webcam did make an pic at that moment it was realy blury becose that cameras CMOS sensro is not fast enugh.

You cod do it well whith an high speed camera that makes about 1000 frames per second.

 

[Dr.EM]

Yeah, the pics I tried in movie mode were pretty hopeless. I hade a frame with nothing, then a frame with a hole in a sheet of paper :lol: . The way its usually done is with something like a sound activated trigger, and about 1/1000000th second shutter. You need a blindingly bright lighting rig to do that though. My photos were illuminated under the built in flash and whatever light I could get.

Check these out for real ones: **broken link removed**

 

[Someone Electro]

Hers one i got in mid air.

Its an 11cm X 4mm nail going at about 24km/h

I dont have not one video of the 7cm X 2 mm iron rod at 27km/h in vich you can see it in mid air.

I did it whith an webcam making 30 fps.This is rare to see.On most videos one frame is unfired an the next frame the projetile is aredy in the target.

As you see the nail looks realy long and blury.

Nice job.

How did you mehure the speed of your "LEGO air powerd wire shoter"?

Did you test how far the projetile goes?

 

[roboticmisinfo]

Errr..... Would be very expensive to be able to get a video camera with such capabilities. I think I'd stick with his original method. Unless you fancy forking out a few grand just for the sake of pressing two buttons at the same time. No offence Someone Electro, but I find it very hard to read your posts. :?

Regards,

Mike

 

[Dr.EM]

I was quite amazed when I captured this shot, it was only my 4th attempt too! In movie mode, there isn't enough light for me to get a fast shutter (no flash), and hence a clear image of fast events, not to mention the unlikelyhood of it actually being there with only 30f/s. Your lucky to have got that shot yourself.

I measure the speed the same way you do Electro, I think. A microphone is placed between the nozzle and target, and the distance between the two "bang" rising edges is read off from the wave editors scale. Measurements were taken at 50cm and 1m. The range, hard to tell, but it is quite a lot despite the small wieght of the payload. I'd definately need to take it outside somewhere to find out, and then it'll be difficult to find it again. It'll reach any place indoors without any noticeable trajectory arc, thats over 7m some places.

Yeah, those professional rigs are very expensive, but the sound trigger alone isn't really.You'd need a camera that can use an external trigger though.

 

[Someone Electro]

You must be having real truble of meshuring that.Since even i had the fire and hit sounds prety close togeter while meshuring speeds up to 30km/h in an 60 cm path.

You also have to make shure that your not ending meshuring at a click in the mechanisem(Like the sprng geting stoped).I dont have that problem becose the only sound you get from a coilgun is the tup sound of the coil geting pushed out by the magnetic force.

Did you try fireing it at somting else than paper like an apple or grape.Or did you try card board (at that speed it might go trough).

Oh i have an idea.Why not stick in on laser pointer.

Its posibe to caculate how far it wod go by knowing the speed (50m/s) and the gravitational acseleration(1 m/s2).But i dont know how.It think it has somting to do whith free fall.

My coilun sucks at distance. It goes about 7 m wen fired from the ground at 45°.Thats becose it goes prety slow at about 24km/h but it can penetrate becose it has way more mass.Its somting like aming whith a canon.There is that trejetory arc.

 

[Dr.EM]

I have a fairly good wave editor, so it was just about possible. Its quite a distinctive sound when it fires, and suprisingly loud. I usually put a drip of water in the barrell which creates an airtight seal around the projectile, at least at the start, but that makes is a lot louder.

Yeah, i've shot grapes and apples before. It goes through one and a half grapes and gets stuck around the core of an apple :lol: . It also goes through those processed cheese triangle things and yeah, some types of card, but not very thick card.

I would think that your coilgun has far more actual energy, but being a heavier projectile, its bound to suffer from quite pronounced arcs. I imagine the short range impact is pretty large.

 

[Someone Electro]

And its probobly safer becose it dosent bounce off.

The nails bounce off wood like it was ruber.(I almost hit me in the head becose of that)LOL :lol:

Its realy realy hard to hit somting from a distance with a coilgun..

 

[Dr.EM]

They will bounce, not sure how, but after hitting that sheet of metal, I found them the other side of the room, but yeah, they are quite safe speeds after deflection.

You probably want to wear a hard hat using your coilgun :lol:

Aiming can be tricky yeah. This would seem accurate, but notice the spead in the first shot. Its not very accurate as they arn't rifled (and such a modification would be near impossible :lol: )

 

[Someone Electro]

But certanly much easyer to aim than a coilgun.

I also found out its NOT a gond idea to shot at the celing.The projetile can land on your head at high speed and i almost hit the light bulb.LOL

I do such stupid stuff whith an nail that has its tip cut off (the tip is flat).So if i do get hit its not that bad.(But hurts if hit in certan places)

I just got an idea! Why not make it trigerd by an person wlaking around.Like an switch on the door or an IR interupter.Someone walks by and pof.

Its also prety easy to make an auto reload feture.Since it just has to slide in an nother nail in the back.And conect the caps to the charging transformer.

 

[bryan1]

When I was a kid we used to get small berries and put two of them in a slug gun. The first one was put in where you put the slug with a bit of saliva to help seal it, then the second one was placed at the end of the barrel the same way. Anyway when the gun fired the compression of the berries made for one loud bang and the berry that flew from the barrel bloody hurt when it hit you. But that was our version of war games, you get the noise of a real gun and a nice bruise when you hit a target(ya mate) but the berry would just splatter and not break the skin or clothing. Maybe a similar setup could be used with your coilgun setup.

Just a Thought Bryan

 

[Someone Electro]

LOL berrie war! :lol:

The ting whith a coilgun is you can only fire feromagntic materials.And a berrie is not feromagntic.

But whith a larger barel Dr.EM cod fire them.But this will reduce peorformace

 

[Dr.EM]

Perhaps you could magnetise one :lol:

Electro, I recken it'd be possible to make your coilgun fully automatic, using a circuit to operate a relay, charging the capacitors, then after a set time, operate the firing SCR, then some kind of motor and mechanical rig to load the next round. That would be quite amazing, how long do the caps take to charge?

 

[Someone Electro]

I estimate it at about 7 to 12 s(never meshured it)

The reloading mechanisem can be probobly simple enugh to make at home.Im thinking of an pin that is puled backwards by a motor and then a spring pused the proketile in then the pin goes back agen and pused the projetile in the back of the barel.

It cod be funy to wire this up whith an door! So evrytime wen someone opens it he gets a nail.I wod call it a securety sistem.LOL

It wod be next to imposible to fuly automate your gun.Becose you have to have an good pump to fill up the tank,an way of wsitging the valves and ther tirckyest part hot to put the wire in it.

I beter make the coilgun run on baterys.I have 2 litiums laing around, an 6V batery pack,an 9V batery... All refilabe.

Or i cod forther inprove it by puting an photo interuper on the nozle to disconect the caps wen the projetile is out.And i dont need that delicate balacing of capacitance,inductance,rasitance,projetile mass and length...

Dr.EM cod you make an video of your LEGO gun?

 

[Dr.EM]

Yeah you should try and do it, it would be cool.

Your right, it would be essentially impossible to automate my lego thing, thats the most annoying thing about it, the long loading times.

A photo switch sounds like a good idea, it could well improve efficiency, and possibly save some capacitor charge too.

I can make a video, but theres not very much to see. On one frame, you can see the valve, quite blurred, half opened, and thats about it :lol: . Something I want to try though is taking a photo/video of it entering water, that will slow it down a lot and hopefully leave a cool looking trail 8) :lol:

 

[Someone Electro]

Water cod be cool.

Or if you fire it at somting hard to move it

Im not in the mood of deigning somting now.But i will probobly do it wen il will be bored.

 

[Dr.EM]

Looking at my first photo, i'm now pretty convinced its actually only the ricochet, not the direct shot (ie, they are travelling left to right after hitting the metal plate). I have some cool photos of some fans on at high speed that actually appear off because of the fast shutter (a little computer one ran at 16v, and a big 18" one on full). Also, photos of the rather slower lego crossbow firing :lol:

I also like the macro mode, as per my new avatar:

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