Here's one that might provoke some thought -

I (along with 2 others) have to produce a project for the University.

Broadly it is as follows -

We are required to design and produce a device which can accurately throw a magnetic dart at a dartboard.

The device must be free standing.

The device must have a sight and be indexable to achieve the full range of shots on the board on request.

The device must be capable of throwing a dart at a board set to a standard height and distance for the mens game

The machine must have an adjustable sight that can be calibrated to the landing position of the darts.

All ideas and thought welcome :thumbup:

Desktop railgun

Here's one that might provoke some thought -

I (along with 2 others) have to produce a project for the University.

Broadly it is as follows -

We are required to design and produce a device which can accurately throw a magnetic dart at a dartboard.

The device must be free standing.

The device must have a sight and be indexable to achieve the full range of shots on the board on request.

The device must be capable of throwing a dart at a board set to a standard height and distance for the mens game

The machine must have an adjustable sight that can be calibrated to the landing position of the darts.

All ideas and thought welcome :thumbup:

Roman ballista with 'arc' plates (with markings) for vertical and horizontal calibration and adjustments ? :confused:

My mind keeps thinking of something based on a crossbow! Does this dart have to travel in the same kind of manner as when thrown by a human, as I'm not sure if you've seen slo-mo on the TV but they don't half wobble in flight, and even Eric bristow can't hit treble 20 time after time.

Not sure if the Ballista will be accurate.

I am thinking pneumatics.

Some sort of firing barrell which will grip/hold the dart in position. The pneumatics would hopefully be able to give a short sharp burst of power to eject the dart switftly and would also be adjustable to achieve the correct amount of force.

The directional system could be something similar to a camera tripod.

I should have added that we are limited to a budget of £300 but we are able to use the a variety of workshop machines, lathes milliing machines and welders.

Not sure if the Ballista will be accurate.

:(

Used to 'pick off' defenders at distances of up to 300yds

Romans in Britain - Roman Artillery

Sounds to me like fabricating something to mimick how a hand works when throwing a dart is way too complicated?

The thing with "firing" a dart is that the end of it has a flimsy *** flight so could not be realistically used as a platform for a launch.

On the other hand, anything used to fire it from the barrel of the dart would need to get out the way fast as the flight comes through.

I don't know if you can imagine a tube with slots cut into it to accept the blades/wings of the flight. Slide the dart into the tube a little so it is supported and then use the air on the end of it.

We can if required manufacture our own design of dart.

All this cos 3 guys get too P**d to stand 'up and straight' to throw a dart :(

I ask you.....

I am thinking pneumatics.

Some sort of firing barrell which will grip/hold the dart in position. The pneumatics would hopefully be able to give a short sharp burst of power to eject the dart switftly and would also be adjustable to achieve the correct amount of force..

For this I think you'd need a consistently reproducible pressure - and some sort of valve to prevent over pressure.

I don't know if you can imagine a tube with slots cut into it to accept the blades/wings of the flight. Slide the dart into the tube a little so it is supported and then use the air on the end of it.

We can if required manufacture our own design of dart.

A 'Sabot' round then! Cool!

From my time as a student - K.I.S.S - play safe to get a good percentage of marks.

Off the top of my head, I'd be looking at a crossbow type device. As you've suggested, you can adapt the launch channel to accept the dart 'fin'. Seeing you're on a budget, I'd look at elastic propulsion first unless of course you've got a ready supply of one of those pneumatic kits (the name escapes me).

I don't know if you can imagine a tube with slots cut into it to accept the blades/wings of the flight. Slide the dart into the tube a little so it is supported and then use the air on the end of it.

Would it not be better to make the body of the dart hollow, such that the end of it with the flight would fit over the end of the airline? That way you get a good decent air seal and so should be able to build up some pressure to get decent flight.

If you also had it so your airline went a short way into the body of the dart, you could experiment with cutting a thread into the airline/dart - so that when the air is forced into the dart and it moves down the airline, it spins to improve accuracy (rather like rifling).

Rob.

Not sure if the Ballista will be accurate.

I am thinking pneumatics.

Some sort of firing barrell which will grip/hold the dart in position. The pneumatics would hopefully be able to give a short sharp burst of power to eject the dart switftly and would also be adjustable to achieve the correct amount of force.

The directional system could be something similar to a camera tripod.

I should have added that we are limited to a budget of £300 but we are able to use the a variety of workshop machines, lathes milliing machines and welders.

Would agree on the pneumatics & 3 legged tripod for stability. It needs to be very stable, you dont want firing it to cause any movement or fine adjustments for accuracy will be lost every time it fires.

To vary the force have a prechargeable reservoir for the gas with a pressure gauge then you can accurately measure the force for each shot.

If you go the dart & barel route then dart & barrel design will be the most critical point, you need as long a barrel as possible to give a straight shot but the inside needs to be super smooth & a constant dia, likewise the dart needs to be a snug fit, the edge of the dart in contact with the barrel must also be something that wont wear easily but must be softer than the barrel. As well as metal I would research hard nylon or plastic tubes for the barrel, If you can find something odds are the manufacturing technique will give a constant bore. Silicone or something similar will also act as a bore lubricant / seal. Possibly also look at thermal issues, if the fits too tight you might find on a hot day the dart sticks. Dont use steel as the darts magnetic, likewise avioid steel in anything close to the barrel

Dart needs to have a circular disc at the head which seals to the barrel & carries the magnet, a thin stem, reosnably long but the tail fins need to be very fine so as to cause min interference with the air firing the dart, 3 fins would be ideal & from a hard material as the tips need to just touch the bore to keep the dart straight & true in the barrel. Not too heavy or it might have trouble sticking to the board. Calibration can be by a horizontal & vertical calibrated plate with fine adjusters, might be worth looking at or even canabolising an old fashioned Theodolite

Loading needs to be quick & easy & thats where a lot of thought will be required, also you need a quick opening valve to act as the trigger & release the charge of gas, You might find the "boss" can source a commercial electronically operated valve for that

Robs idea of a hollow dart is also well worth looking at & might offer a simpler to engineer solution, many of the points above apply but it would easily overcome the loading problem. Having watched Owen its amazing how far you can blow the plastic sleeve they put over straws in the MuckY D type establishments, with high pressure & a decent seal that a smear of silicone would give you dont need that big a bore & the fins can be designed purely to give good flight, in fact the more I type the more I am convinced thats the way to go

Other idea is a blowpipe/airgun type effort - get a solenoid garden valve, an air tank to about 125psi. You'll be able to hit a bullseye every time....

Use a commercial blowpipe and darts...

Its a magnetic dart so velocity will be an issue, its not going to work if it gets spat at the board too hard.

Time to start watching the mythbusters re-runs

Desktop railgun

yep why would the dart being magnetic get mentioned if they weren't after building a railgun

Velocity is a big issue as you say Colin, it is very easy to over cook it and cause the dart to bounce back and hence why I arrived at pneumatics.

Some good for thought there though, thanks very much everyone - Keep thinking :P

Velocity is a big issue as you say Colin, it is very easy to over cook it and cause the dart to bounce back and hence why I arrived at pneumatics.

Some good for thought there though, thanks very much everyone - Keep thinking :P

Some sort of sprung loaded head on the dart might help reduce the "bounce effect"

yep why would the dart being magnetic get mentioned if they weren't after building a railgun

I wouldn't be walking in front of that!!

On a slightly cheaper scale:

TechEBlog » Hammerhead - The Lego CD Thrower (YouTube - The Hammerhead - The Lego CD Thrower)

or

ULTIMATE Lego Chaingun -- not your parents' rubberband gun - Engadget

In order to guard against recoil moving the tripod, hang a heavy weight from it.

If you go the pneumatic route, use wadding behind the projectile to prevent "blow-by". For a good design, look at the wadding used in shot-gun cartridges.

lots of knex stuff on here

Instructables - exploring, knex - DIY & How To

The Ultimate Knex (Autoload) Rifle - Instructables - DIY, How To, knex