Another version of how not to build a model engine

[sorveltaja]

No strobe light or any other measuring devices were used. First I adjusted the spark timing just by listening the engine(just as I did before).

Then was camshaft adjustment. It was made by the same procedure.

Next I probably have to make a wooden base, as the engine has kept my machining vise occupied .

New version of the engine? It's possible, but can't say yet about that.

[NickG]

Just wondered what the red flashing light in the vid was, or was that getting the speed?

[sorveltaja]

Flashing red light came from the camera. I just wonder what its purpose is .

[Bernd]

Flashing red light came from the camera. I just wonder what its purpose is .

The light looked blue to me, but that doesn't matter. I think it's to remove "red eye" from humans in the picture, but on a video? Maybe for focusing?

By the way S, nice running engine. Starting to sound like a nice Swiss watch ticking away. 

Bernd

[dsquire]

sorveltaja

We are definitely going to have to give you an A++ for dedication and determination. A lot would have given up or put it aside by now but every day you kept trying something new. Watching it run now you have a very sweet running engine. If you decide to build another one I can only imagine how much sweeter it would be after having learned so much from this one. Thanks for letting us look over your shoulder as you built this one. 

Cheers 

Don

[Darren]

It deff looks red to me, but no matter 

It's so you can't secretly film people without their knowledge 

[Darren]

You have certainly had perseverance with this little engine ... top marks on the development 

[sorveltaja]

Thanks again  .

This project has teached me a whole lot about how to make a four-stroker run .

Especially the sidevalvers have always fascinated me, so the next project is most probably a small flatty twin four-banger.

Current engine has became kind of reference, and I'll continue the testing with it once in a while.

[sorveltaja]

The sparking plug, and especially its ptfe insulator, has became a bottleneck, when testing the engine, as it erodes away too fast.

I have made few rings out of ceramics, that are to be used on the business end of the plugs. Hopefully that eliminates the insulation wearing -problem.

[madjackghengis]

As a matter of course, I would suggest the nut would work just fine, but only needs a drop of locktite to keep it retained.  I've been building Harley engines for some thirty odd years and the only thing that keeps all their parts on the engine is locktite or self-locking nuts, cotter keys, bunged up threads and the like.
    As a rule of thumb for an engine, a carb bore of a quarter the cylinder bore is usually a good size to start with.  This works well with multi-cylinder engines as well, as only one cylinder is fed at a time.  A smooth venturi with a good taper leading up to it helps keep a consistent vacuum to pull fuel in as well.  For what its worth,
mad jack

[sorveltaja]

I've tested sparking plugs with those ceramic rings, and they definitely don't wear out as easily as ptfe.

On the other hand, as this engine is on the experimental state, even the spark plugs need to be easily disassembled and cleaned, if needed.

Using ceramics doesn't make that easier. Not to mention, that it's quite delicious delicate job to make parts from it, that fit.
Plaster anyone?

Big white is the resistor body, that was originally attached to an automotive ignition coil, that I use. Next is one of the spark plugs.
And the marble looking thing is just one of the rings, that I managed to hack out of that big white. Bluish colour comes from felt tip, that I used to mark, where the cut was made.


Conclusion at this point is, that the engine still runs at too rich fuel mixture, causing contamination on the sparking plug rather easily.

--------------------------------
Mad jack, somehow that cyl.bore/4 = carb bore makes sense, as it says, that I'd need to enlarge current carbs throat from 1.9mm(~0.075") to 2.6mm(~0.102").

Anyways, the engine already runs too fast with that 1.9mm carb bore, if allowed.

[sorveltaja]

Today I disassembled the engine, and whole combustion chamber was again coated with bituminous black dirt .

It is now cleaned, and before going back to ordinary carburetor, I'm going to make the vapor carb, to test if it gives cleaner combustion .

[NickG]

S,

Somebody over on HMEM just finished an i.c. engine and used the vapour carb with really good results. He also tried the same tank / carb on his hit & miss engine and that ran really good too, so much so that he is making another jan ridders vapour carb for that too!

http://www.homemodelenginemachinist.com/index.php?topic=6352.105

Nick

[sorveltaja]

Nick, thanks for the link .

I occasionally visit HMEM, but somehow I've missed that excellent thread.

[sorveltaja]

I have started testing with vapor carb, and also discovered the blowback -phenomena.

Not a new thing, as the very first running test were made with same kind of carb.

Back then I tried the ball valve to prevent blowbacks, but couldn't get it to work.

But this time I'll be using adjustable spring loaded valve:



Valve needs to be lapped, and spring added. Also the bigger brass part needs some brass tube, as the whole thing is to be installed between the engine and fuel tank.

[NickG]

I think you need to find where the blowback is coming from and get to the route cause - there must be something leaking on the compression stroke for that to happen. I would try submerging the engine in water, turning it over past the compression cycle and look for the bubbles.

Nick

[sorveltaja]

Nick, most probable source of leak is the inlet valve, but as the engine has tight springy compression, leak must be quite minimal. But even that is enough to cause flowback.

I guess that the air in the fuel hose "lives" between intake strokes. Don't know how to explain it, must be one of those hunch things .

In the meantime, I have made primitive vapor carb:


Upper brassy thing is simple air/fuel mix adjustment, and it is to be modified, as it's bit too touchy to adjust.

The inlet tube goes below the fuel level, causing bubbles, as Jan Ridder's carb does.

Then there is the spring loaded valve combo, that was mentioned earlier.

With it, flowbacks are gone . Even the short running tests have proved, that it works very well.

Therefore, I strongly encourage to test that, if flowbacks occur.

[NickG]

S,

On Jans later version he stopped the inlet tube short of the petrol. Can't remember why  but he said it improved matters!

Good work, it only needs to be primitive to test the concept out. Does it solve your over rich mixture and sooting up problems?

[sorveltaja]

Nick, the spark plug stays dry, and that hopefully makes it last longer, and keep the engine cleaner, than with recent carbs. I could even pass that ceramic rings -session .

[sorveltaja]

I attached that spring loaded valve thing straight to engines inlet. But the engine ran poorly after that.

So I went back to setup, that is shown in the previous picture.

There is about 5cm(~2") hose between the valve and engine. Strange, but with that the engine runs much better .

But for example, on backpressure valves, that are used on gas welding equipment, the valves aren't attached to handle, are they?

There is most certainly a piece of hose between handle and backpressure valves.

Conclusion is, that backpressure valves require some matter, be it oxygen, acetylene or air, between them and the source to work.

[NickG]

Another strange phenomonen. I know I keep banging on about Jan Ridders engines, but this is because he has build a lot and done a build log of his findings with all of them. I noticed on a couple of his engines he has some sort of additional chamber with check valves in line. Not quite sure why they are needed without reading through it again but they are!

Nick

[sorveltaja]

Well, the unlucky sparking plug saga continues.. Any spark plug, that I've made, doesn't seem to last in use.

I have considered purchasing commercial ones, as they have ceramic insulation. Smallest size available here is NGK CM-6.

Anyways, I suspect, that 12V/2.5A, that my current power supply gives, isn't enough, causing sooty contamination.

[jim]

CM-6 are 10mm thread, NGK do spark plugs down to M8 thread, don't know how long they are though

[sorveltaja]

In the meantime, I took the ignition system under inspection. Especially the ignition cam caught my eye (finally).

The flat part seems to be too large, as it causes two sparks. First being weaker one, when the ignition points close, and second being the desired one, when the points open.

So I turned the ignition cam's diameter ~0.5mm(~0.019") smaller, thus making the flat part smaller also, just to see, does it have any effect on that double sparking -problem.


Shame on me, as it might be too hasty to tell any results yet .

But it seems, that faster close/open sequence works better. Earlier, same amount of test running got the spark plug(s) sooted badly.

Now the plug stays cleaner anyway, for some reason .

[Bernd]

S,

Wouldn't a lobe like on a car engine cam work better that a flat spot? Just wondering out loud.

Bernd