miniature 2 stroke gasoline engine

[Zephyrin]

Thanks for the appreciations...
MJM460 :
This engine don't overheat, up to now, about 15 min of uninterrupted run, up to the end of the whole gas tank, 7-8 ml
he could run longer, but looking at an engine running unloaded is rapidly boring...and more noisy than watching paint drying.
so as soon as an engine run, I have to find something to drive...
truly, I don't know yet !

To change myself from live steam locos, I'm making plans for a gauge 1 little diesel shunting loco that I thought I would equip with a small 4 stroke of a similar size, 12mm bore & stroke, as space is scarce on such a model, but maybe I already have the engine !

[Roger B]

That's a nice runner    unloaded two strokes seem somewhat unstable but settle down under load.

One of the members on here, Gail in NM, has made some gauge 1 IC locos:

<a href="https://www.youtube.com/watch?v=xXnWSJOSuE0" target="_blank">http://www.youtube.com/watch?v=xXnWSJOSuE0</a>

<a href="https://www.youtube.com/watch?v=a-csJ3As7dc" target="_blank">http://www.youtube.com/watch?v=a-csJ3As7dc</a>

[Zephyrin]

i'm well aware of these great "diesel" shunter loco...this exactly the kind of model I'm planing to do...
about 2 years back I've emailed with Gail about this project, and he gave me very useful advices, a very helpful gentleman and a outstanding modeller!
for this project, I first thought of a small 4 st, "tiny -like" as suggested by Gail Graham, with a more realistic noise for a model of locomotive, but if this mini 2st is reliable, it could very well take its place!

I hope to be able to do this project during the year 2020, but the years pass so quickly ..

[Zephyrin]

I also finished the 2nd engine, made it a new cast iron piston, and both are now running “at their best” and easily reaches 5000 rpm without load, noise and fumes are there, everything is fine.

I give them small differences in the height of the port simply “to see “, but in fact I see no difference in the running…!

But I have only one contact breaker that works, yet identical : I simply grinded one spring, which seemed too strong, and the engine, being launched at speed with the dremel, refused to start, as sparks die as speed increases, whereas the contact breaker gives a nice spark turning the engine by hand. It took me a while to see the problem!!

video of the 2nd engine, which of course looks like the first one!

<a href="https://www.youtube.com/watch?v=BDey2ERMJT4" target="_blank">http://www.youtube.com/watch?v=BDey2ERMJT4</a>

I clearly felt the ramp up with the advance of the ignition , not as clear on the video, (never easy to film during the action!) but the frequencies on the soundtrack confirm it ...

Maybe a power measurement, and tests with a propeller instead of the flywheel, but I consider this project as finished ...

[Jasonb]

Runs even better than the first

[Dave Otto]

That's pretty cool!
Nice work.

Dave

[Don1966]

Awesome work....



 
Don

[Zephyrin]

thank you all for the appréciations and feedback...

Yes Jason, I also think the second one is better, but I'm not impartial, because it's my preferred !

In fact, these small engines seem to be unable to idle, they only know the maximum rpm, I guess it's due to their small size and power, and that limits their use a lot...

[Roger B]

As far as I can see your carburetor doesn't have any form of throttle. You will probably get a better rpm range with a throttle carb that by adjusting the ignition timing. I would hope for at least a 4-1 rev range. My 12cc twin will run from 2000 to 8000 rpm with a simple barrel carb.

[Zephyrin]

Yes, I put a simple mixing valve as drawn in the plan...
these old timer models are made to run at max rpm only, far from modern standard of today model engines, with full RC control, much more pleasant I agree.
I adjust the timing as speed increases, inducing further increase in rpm, up to an optimum, but at this setting the engine doesn't start easily !

I learned also that I can't get high speed without a quite stiff spring and a very small gap (less than 0.5mm) in the contact breaker.

[Zephyrin]

I can't stop making 2 stroke engine...
here is a third one, made using the tooling and some left-overs of the previous...As I also did lot of changes in the plan, I dare to call it a personal design !
This model runs well, at 4500 rpm unloaded, but refuses to start with a propeller.

<a href="https://www.youtube.com/watch?v=hJMx6hcSGGw" target="_blank">http://www.youtube.com/watch?v=hJMx6hcSGGw</a>

more pictures in this album:
https://photos.app.goo.gl/8wX7sXmDjmBYSYJF6

I learned a lot with these exercises, but the time has come to move on to other models...