Hello again guys!
Sorry for the late update, the report for the project was handed in 2nd May and we got the best grade possible for doing it. (MVG as it is called in Swedish)

And by the way, we corrected an error in our excel program. We had accidentally used the diameter instead of the radius ...

I tought it would make the projectile more aerodynamic. I was wrong. According to the sound it made, I think it had a lot of drag.

If you could make it more streamlined that would probably help, otherwise golfballs have quite low Cd as they are anyway. My friend found a graph that shows that the ...

Labtecpower wrote:

What kind of projectile is it?

A golfball with a cardboard tube strapped to the back

I see, out of curiosity, why don't you skip the cardboard tube?

It is quite plasuable you overshot the field. I get almost 400 yards with a golf ball on only 50 PSI. I always lose full pressure shots for distance.

Yay! Glad to hear that, I thought we might just had lost them in the dirt. Ok, I can imagine we are not the only ones with problems finding the ...

We tested the cannon this Saturday.
It went surprisingly well. Unfortunately we had made the sabot too weak, and it broke after two shots. However we had a taped styrofoam cylinder under the golf ball instead so it worked anyway.

To our misfortune, we could only retrieve one ball. That was after ...

Today we went low-tech.

We now suspect that we have actually broken the ignition coil in some way. Tried to wire it again today with no succes.
Therefore we unscrewed the spark plug and installed a piezo lighter sealed with electrical tape instead. I know some of you will facepalm, but since we ...

When we were about to test the cannon again yesterday with the fan we failed tremendously.

First off, since the fan runs on DC we thought that if we would switch the cables from plus to minus or vece versa we would be able to run it both ways, and therefore we didn't take much notice of which ...

That won't be terribly good at venting, but will work perfectly well for stirring and creating turbulence during combustion.

Styrofoam may work for a sabot, but I'd be worried about the friction in the barrel and making a good seal with something that's difficult to compress or deform temporarily ...

Is the fan positioned so that its flow is parallel to the axis of the chamber? For an atmospheric combustion, the fan matters little except that it creates turbulence during combustion, stirs the mix, and can help vent combustion gases.

I don't really know where the direction of the flow will be ...

Today we have mounted a 80 mm cpu fan in the chamber, we placed it on the opposite side of the spark plug and fuel intake, slightly above the bottom. Does that sound ok, and do you think epoxy glue will hold it in place or will it eventually come off?


Thanks for the link of the kettering ...

If the tank puts out 2 bar gauge, there is 3 atmospheres of air. Eventually the air that was in the meter when you constructed it will be purged out.

At this point, you can fill it up to 2 bar gauge, and the amount that will come out under its own pressure will be 2x the volume of the meter. The ...

I would try a shot with only 1 bar in the fuel meter. This will give a leaner mix, and may prove to be a better mixture than with 2 bar in the meter.

Since we did that nice miscalculation with the pressure. (thinking it was 2 bar that went out, and therefore thinking that we would get 1 bar of ...

A momentary connection of touching the two wires together and then separating them will do fine in place of the points. The points is just a switch operated by the cam. A connection of just a couple milliseconds is all that is required to build the coil current. The spark is when the wires ...

Chances are, the 2 bar is the gauge pressure. When you first fill the meter, you will get 1 bar of air (from the atmosphere) and 2 bar of propane (essentially).

Once you expel that, you will have 1/3 bar of air and 2/3 bar of propane in the meter. This continues until the meter is almost ...

The spark will be weak (thin and very faint) with that ignition set up. Add a proper condenser from the ignition system to make a vast improvement.

The ignition will be weak without it because as you break the connection with the battery, the resulting arc at the switch prevents the high voltage ...