As this site is supposed to be amateur/experimental activities, I thought I would highlight some projects and components that would be of help to others in the area.
The first thing I will highlight is, how to make your own igniter for your liquid rocket engine project.
If you were wanting to delve into the realms of liquid rocket engines for your next project, a good starting point is to make the igniter for it. Although the engine could be lit with a solid-fueled cartridge up the nozzle (as Copenhagen Suborbitals do, to name one) this has the implication of having to insert a new cartridge every time you want to restart the engine.
Now this may not be a big deal but once you have a working engine you probably would like to perform multiple tests in a day, and having a system that can be activated at the press of the button and one that does not require personal to be close to the test setup would make things a little easier.
The most common form of the igniter for an amateur liquid rocket engine is a spark torch igniter. This is essentially a mini rocket engine that takes a gaseous oxygen feed of your liquid oxygen tank along with a fuel feed and has it injected past a spark plug, which ignites the mixture and directs the flame into the main combustion chamber for engine ignition. A version of this I made can be seen in the video below.
This was my second attempt at the igniter, using gaseous oxygen and propane, it worked but not very well. Since attempting to make this there have been more and more people documenting their projects on the internet and there are 3 out there right now that have all the info you need to make copies of their own spark torch igniters.
Rocket Moonlighting has been building 3D printed rocket engines for a number of years now and he has recently been kind enough to publish his design and code files for his PR56 igniter. The PR56 should be capable of igniting rocket engines of up to 1000lbf right up to 5000lbf (4.4kN-22.2kN), this would fit well within the means of most amateur rocket engineers.
A full description plus all Rocket Moonlighting’s projects can be found on the above link.
Graham has also been building 3D printed rocket engines and igniters, his page describes in detail of the process and experiences he has had to make a liquid-fueled rocket engine.
Grahams current igniter, V3, burns gaseous oxygen and ethanol and produces a max thrust of 2.5lbf (11.12N)
Graham has meticulously detailed his experience in making and firing this igniter, making his website a must to read through to gain knowledge of what not to do and what to do.
Roberts Rocket Project
Robert has been building a 250lbf (1112N) lox/kerosene regeneratively cooled rocket engine made completely from aluminium. Final testing of the engine has been completed and Robert has started work on the rocket that it will power.
And of course Robert has built his own spark torch igniter, as shown below.
Like most of the other igniters, fuel and gaseous oxygen are obtained from the run tanks to light the igniter. The V6 produces 1.1lbf (4.9N) of thrust and operates at 130psi, Robert has extensively tested this latest version of the igniter and has documented this on his website.
Although his drawings are not dimensioned he has provided the excel spreadsheet with the design calculations in it, this will make it more fun and hands on for you, having to learn and understand the calculations. Lots of his knowledge and experience can be found in his news section of his site that will also be of help to get you going.
The stated projects should put you in the right direction to making a working spark torch igniter.
Other documents worth reading to help you get on your way are,
NASA SP-125 (Design of Liquid Fueled Propellant Rocket Engines) – Book or pdf.
Rocket Propulsion Elements – Book