Recent content by Roger B

Small diesels are interesting. There are many different possibilities starting with the model aircraft type using compression ignition of a carburetted mixture of kerosene (paraffin), oil and ether. There was the Lohmann commercial moped engine that used an 18 cc carburetted compression ignition...

Did you heat treat them to get the 'spring'?

Using a rack to rotate the sleeve is quite feasible. I have made a helix pump using a MOD 0.4 rack with a 20 tooth pinion.

I would suggest that you look at a suitable drive dog or free wheel so you can turn it over with an electric drill, especially in the early stages. This allows you to adjust settings whilst the engine is turning.

Pump diesel will not be a problem, many common rail engines circulate the fuel through the injectors. Plant oil based fuels can be a problem as they break down at high temperatures. Using cooking oil as a fuel for a conventional jerk pump system is ok, for common rail expect problems.

0.2mm in brass is ok, in stainless steel it is more difficult. Getting adequate compression pressure and temperature in small engines is difficult. The cam timing, specifically the closing of the inlet valve, can significantly effect the compression at low/cranking speeds. Gardener used a...

I think that this maybe the early Vickers common rail fuel injection system. There is a separate engine driven pressure pump delivering 100-200 bar. The injector is held closed by the spring right at the top and is opened by a cam and rocker. There is a brief reference on Wikapedia dating this...

Thank you for starting this thread 👍 A few comments/thoughts. Ball inlet valves are a problem with fuel volumes that are less than the volume of the ball. The ball has to move and as it returns to it's seating it effectively increases the volume of the pump chamber. This is why I have chosen...

My compression gauge fits in place of the injector. It has a non-return valve as close to where the injector nozzle would be as possible so as not to affect the combustion chamber volume. The valve currently doesn’t seal as well as I would like. In the video clip the pressure is reaching more...

Excellent 👍 👍 👍

20-1 compression ratio will work with a compact combustion chamber with minimal heat loss. My diesel has, I think, a higher ratio. The compression pressure is around 30-35 bar when cranked at 2000 rpm with the drill. For volatile fuels you will need a feed pump for the injection pump. For...

I have used that material on several engines without problems. The compression pressure on my 25mm bore four stroke diesel is around 40 bar and the cylinder head is fixed with 5 M4 studs.

I use an industrial pipe gasket material, VALQUA No.6500. It was available in small sheets for model RC car engine exhaust sealing. I am using a 1mm thickness. https://www.valqua.com/product/sg6500/ I am sure there are many similar materials available.

Here is a run with the needle injector: The original Eisfeld model aircraft diesel engine used an open injector having also tried needle types. He then moved on to the current carbureted design. I have attached a translation of the original article.

Glad to hear you have got some runs from the engine :) Shame about the missing bolts but that is a relatively easy fix. I have been expermenting again with needle style injectors. They seem to run quite well but you always have the problem of fuel leaking past the needle. On one test run the...