SpudFiles

This How to is a multi part, work in progress. This How-to describes how to build this gun here: http://www.spudfiles.com/forums/viewtop ... tml#226999.
I have decided to build another for several reasons, these being:
-A lack of inside/gut photos.
-Not up to my standard of neatness.
-Photos for doing a how to.
-Unhappiness with the fan. (it moved near no air).

So in this, I'm hoping to fix these problems and demonstrate how to build an advanced micro combustion

Part 1: Ignition.

Materials required:
-Small, NON-BRITTLE plastic tube.
-Copper tape or similar. This is commonly used in lead lighting. Basically a flexible copper strip with an adhesive underneath.
-2 small screws or machine screws.

Tools required:
-Scalpel, razor or a very sharp knife.
-Drill (any variation) and a drillbit slightly smaller than your screws.
-Scissors or hacksaw, depending on the strength of the plastic tube you are using.

Method:

Step 1:
After collecting all the required tools and materials, cut your plastic tube into a "C" shape or a "U" shape as you would with a traditional spark strip.


These are the materials being used.

Step 2:
Measure and cut a strip of copper tape that is an equal length to your tube. Stick it on the top (opposite to where the gap of the "C" or "U" is.) and smooth out with a fingernail.



Step 3:
Drill two holes, one in each end of the plastic tube. Try to place them through the middle of the copper tape, and opposite from the gap. Once that is complete take your two screws and thread one into each hole. Only screw them in about halfway!



Step 4:
Take your cutting instrument, and cut VERY THIN gaps in the copper tape. You can place as many as you feel are required. Keep in mind that electricity will ALWAYS take the path of least resistance, and that a sharp point transfers a spark much better. Remember that you only want to cut a slit in the copper tape, and remove a small amount. Don't cut through the tube.



Step 5:
Take two insulated wires OR two wires (insulated) which are already attached side by side. Not sure what that's called. Use a wire stripper or a pair of scissors and remove some insulation from each end. Wrap the wires around the screws, and then tighten them down completely.



Congratulations, that's the spark strip finished.

Part 2: Fan.

Part 3: Chamber.

Part 4: Fueling and metering.

Part 5: Barrel.

Part 6: Firing.

Part 7: FCU (Fan Control Unit)

This is simply a unit to control the fan. It can be as simple or as complex as you would like to build it. If you're a real electronics whiz you could knock up a timer.

Required:
Battery (batteries).
Switch.
Method of connection to fan.

Optional:
LED to indicate operation (or buzzer)
Fan timer
Banana plugs or similar to attach to fan.


Simple diagram. Labeled for the non-electrically oriented.


Open unit.


Control panel, push button switch (bottom left), LED (bottom right), plugs to connect to fan, with removability (center).





My unit houses two AA batteries (in a cradle), a push button switch (press in = on), a red LED, and two plugs to connect to the fan cables.

Note: You can choose to build separate units for each function (ignition, fan etc) or a single combined unit. I would recommend separate units to prevent shocks from the ignition unit and to prevent confusion.

The construction is up to you


Part : Troubleshooting and Q/A's.

For the sake of the general public I will not use 1337/noobspeak.

Q: Why isn't this guide completed?
A: It's a work in progress, it will be finished as I go along and take photos.

Q: Where do I get ___?
A: http://www.google.com - search it.

Q: Why do some of your pictures suck?
A: My camera is of poor quality and does not take good close up photos. You may have noticed that some of my pictures have been quite good. Those ones have been shot by my parent's camera which is around 10 times as expensive.

Yes the pictures are basically unusable. Are you sure your camera doesn't have a macro mode, a "flower" setting maybe. Oh well, you should plan to retake those at your earliest convenience.

I like the general design idea here...this particular spark strip. Your gaps are really too close together to make much difference. They need to be spread more evenly down the full length of your chamber as much as possible. These are too closely clustered together to make a power difference. They may however, offer more reliable ignition.

I also noticed your ignition wire is apparently a twin lead zip type cable...MAJOR bad news. Pull those wires apart and separate them and their path to the strip. This is your ignition problem you are experiencing at the moment.

starman wrote:Yes the pictures are basically unusable. Are you sure your camera doesn't have a macro mode, a "flower" setting maybe. Oh well, you should plan to retake those at your earliest convenience.

I like the general design idea here...this particular spark strip. Your gaps are really too close together to make much difference. They need to be spread more evenly down the full length of your chamber as much as possible. These are too closely clustered together to make a power difference. They may however, offer more reliable ignition.

I also noticed your ignition wire is apparently a twin lead zip type cable...MAJOR bad news. Pull those wires apart and separate them and their path to the strip. This is your ignition problem you are experiencing at the moment.

Nope, my camera is just plain crap.. It's modes include "Off", "Favourites", "Auto" and "Video".

And with the ignition wire, I was thinking that during construction. During testing it was absolutely fine (the mis-sparks were from one of the cords that had fallen off my piezo. ATM it seems fine for piezo use, but that may change with fuel in the chamber. When I get a camera flash ignition together they will definitely be separate, with a much thicker guage wire with good insulation. No way I'm being shocked by that.

As for the spark strip, the length is up to whoever builds it really. I'm aware that at this size it will give little to no performance improvement, but it will give you 3x the chance of igniting the mixture. I can see that helping a lot in a mini.

EDIT: I just finished the FCU. (will add in section). For user friendliness, I'll add a good paint diagram to each part, and at the end I'll get a very good camera and get a high quality shot of each part.

Thanks for the input

I've just looked at numerous camera flash designs, and I'm realising that it will just vaporise the copper tape, so I'm just going to use a heavy duty piezo until I build a flyback or manage to get a stungun in aus.

Apologies for the double post. I attempted to edit my first post but I got a connectivity error from firefox or something, I've had the problem before.

I've taken some better photos (with a different camera) and they're a..bit better .



FCU panel.



Back of FCU.



FCU open.



Spark strip.



On a slightly different subject, I found this piece of circuitboard:



It has many, many capacitors, ranging from what I've seen, up to 2200uf (microfarads). Would these be feasible for building an ignition system with?

you need to look at voltage.

An ignition unit is required to power your spark strip. At this scale, the best method is to use a piezo igniter, but you can use other ignition systems including:

-Stungun
-Camera flash
-Flyback transformer

If you wish to use a different system, please google it..

A piezo generally has a wire and a brass colored contact. The contact is the eart and is required to complete the circuit. A switch should be included to prevent accidental ignition during fueling or transport.

Here are several images, and several others at higher quality.

You still haven't separated those HV lead wires. It will be essential that you do that.

starman wrote:You still haven't separated those HV lead wires. It will be essential that you do that.

And why would that be? It all depends on the insulation... I've had thick wires who's insulation wasn't strong enough to stop sparks jumping through, and thin wires with insulation that the spark simply cannot breach. If it works at the moment, I see no reason for him to separate the wires.

Insomniac wrote:

starman wrote:You still haven't separated those HV lead wires. It will be essential that you do that.

And why would that be? It all depends on the insulation... I've had thick wires who's insulation wasn't strong enough to stop sparks jumping through, and thin wires with insulation that the spark simply cannot breach. If it works at the moment, I see no reason for him to separate the wires.

Because there's no need in tempting fate. You never see HV anything anywhere run parallel like that. He already complained about being shocked and his video indicated the sparks not reliably reaching the gaps. It may work now, but suddenly stop working with a propane filled chamber.

He did say that the missfires were due to a wire falling off the piezo, so I don't think that is the problem. If it were me I would leave it as is to keep things neat, and if it caused problems I'd change it. But that's just what I would do.