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Model engine extravaganza

If you're interested in more model engine stuff, you may like this site by John Bentley.

A couple of my favourite projects of his are his Naphtha launch engine build from scratch from the original patent drawings... these are very cool engines, they use naphtha as both the fuel and the replacement of water as the medium that expands and condenses, and his steam tug.

https://modelengines.info/
 
From what I gather in other model engineering forums, Find is the Yoda of true diesel engines, meaning mechanically driven micro squirt injectors/system. There are every few on the planet that are working on this & fewer still with what can be nicely running model diesel engines. Unfortunately Find isn't really volunteering revaluation of the secret sauce, not being malicious, just politely refuses.

 
PeterT said:
From what I gather in other model engineering forums, Find is the Yoda of true diesel engines, meaning mechanically driven micro squirt injectors/system. There are every few on the planet that are working on this & fewer still with what can be nicely running model diesel engines. Unfortunately Find isn't really volunteering revaluation of the secret sauce, not being malicious, just politely refuses.

Click to expand...

I spent an inordinate amount of time studying diesel engines, and model diesel engines in particular. I owned a diesel model engine in the past I bought from a member of a forum that I bought to study and use in a project. I sold it because it didn't work well for me. It had a flow thru simple injector.

I've viewed Find's website about 1000 times over the years and I studied his details as closely as it is possible given the little details and image sizes.

I'm pretty sure that Find's diesel engines use a very simple spring actuated injector mounted directly in the center of the cylinder head. Like a poppet valve.

The secret sauce to his fuel systems are the calculations for fuel flow and pressures for paired injector pump, fuel lines and the remote nozzle. The injector chamber and nozzle sizes are critical as is the spring tension in order to get the perfect atomization of tiny amounts of fuel.

Then he governs the fuel flow with a governor that controls the injector pump via a cam rod...

Then he makes dual cylinder engines and has to double everything, and get the flows to be symmetrical.

Oh and the real secret sauce is Find's pump assembly, because I believe that to atomize the fuel in the tiny distance and volume of a model diesel engine requires very very high pressure. Over 2000 psi is a figure I've heard used in the past.

His assembly technique is to use high heat assemble the pump housing and to fit the piston tightly in the tiny bore with minimal clearance. He does this by heating the housing, melting solder in the housing and then fitting a heated piston rod that has been dipped in oil.

The oil serves two purposes. It provides a thin film for the piston clearance, and it prevents the solder from sticking to the piston. You mass produce the small parts and assemble them in batches because there is a assembly failure rate as many will become fused solid despite the oil barrier.
 
PeterT said:
Hopefully you followed this one. Many hours of experimentation. Some neat 'squirt' videos along the way. I'm waiting for 'the plans' haha

Fuel injection systems

Fuel injection systems
www.modelenginemaker.com
Click to expand...
That thread is one of the places Chuck Fellows spilled the beans on how Find makes his injector pumps,... Chuck was a very open guy who believed in sharing what he knew. He shared a lot of info with me for which I am very thankful.

Oh and before I forget, I think the piston Find uses is a purchased needle bearing roller that is precision ground.
 
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