Author Topic: a very small 4 stroke engine : 1.35cm3  (Read 1727 times)

Offline Zephyrin

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a very small 4 stroke engine : 1.35cm3
« on: May 23, 2020, 09:48:27 AM »
I present you my last engine almost finished and running; a mini 4T of 1.35cm3, (0.08cu in) (bore and stroke: 12mm).,
I wanted a 4 stroke engine, spark ignition, with a reasonable noise level, good power and not running too fast. The goal was to get an engine capable of moving a small mechanical diesel shunter for the 45mm,  gauge 1 track at 1/32 scale more precisely.
So I designed a model inspired by some early engines with a camshaft parallel to the cylinder driven by helical gears, with also a low compression ratio, about 4.3; the cylinder head having a large combustion chamber with face to face valves, quite in the style of the Wyvern and Centaur from ET Westbury, from which I also copied the rocker arm style. The cylinder head has 2 valves controlled by rocker, but I reserve the option to test an automatic intake valve if all goes well.
I also put a water tank for cooling, rather than a water jacket and its associated pump, radiator and fan owing to limited space.
There is also a large flywheel (relatively!) for the smoothness of operation for such a small engine, leaving me the possibility to put a second one on the future drive side.
There is for the moment a traditional ignition with breaker and HT coil; I  had to make some home made spark plugs, mini too, the 1/4 x32 being too bulky on this tiny cylinder head, especially with the carburettor too close to the spark plug, not easy to adjust air intake without receiving electric shocks!
After a rather long running-in, mostly because of my "shop-made" helical gears, it has no more stiffness and started easily, responds well to settings for air, fuel and ignition timing, and runs like a clockwork, but alas, far too fast for my taste, between 2500 and 5500 rpm, the noise being not the expected "put-put-put", but in an acceptable range.
I’ m actually doing an electronic ignition and rebuilding a more advanced carburettor than the simple mixer, and do some power tests to see if the rest of the program is feasible.
but I'm currently making an electronic ignition from a gas lighter as shown in the Jan Ridders website.
I’m also drafting a final version of my plans, but I’m not expert in this field !
I will post some pictures of the building of my engine, after the final result, I agree that this is not the usual way to proceed, but I have to select lot of pictures in my computer…




Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #1 on: May 23, 2020, 10:27:13 AM »
Excellent  :praise2:  :praise2: Fitting a spark plug and valves into a 12mm bore is not easy. Did you use piston rings?
Best regards

Roger

Offline MJM460

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #2 on: May 23, 2020, 01:00:37 PM »
Congratulations Zephyrin on a great runner.  It is a really neat and compact design.

MJM460

The more I learn, the more I find that I still have to learn!

Offline fumopuc

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #3 on: May 23, 2020, 02:12:10 PM »
Hi Francois, very nice.
I should put something similar on my retirement list.

Kind Regards
Achim

Offline nj111

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #4 on: May 23, 2020, 04:15:15 PM »
That is fabulous! Thank you for sharing here.
Nick

Offline awake

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #5 on: May 23, 2020, 05:16:42 PM »
Wonderful sound - so even and consistent. Congratulations!
Andy

Offline Admiral_dk

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #6 on: May 23, 2020, 07:30:44 PM »
Impressive that you got it running so well with such a small design  :praise2:

Offline Art K

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #7 on: May 23, 2020, 11:25:39 PM »
Zephyrin,
You have built quite a nice running engine. I hope it works for your shunting engine!
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Craig DeShong

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #8 on: May 23, 2020, 11:27:43 PM »
Not a lot of room for miss fit machining with a displacement so small.  Runs and sounds great!  Superb job :ThumbsUp:
Craig

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #9 on: May 24, 2020, 08:19:01 AM »

Thanks for all these appreciations and comments,
My engine is not as small as the famous "tiny" published some 10 years ago by putputman, with its 3/8" bore, and its superb hit & miss versions by Gail Graham and Georges Britnell, unsurpassed...

You are right Craig, but you can note that I left some length on the camshaft for a centrifugal regulation, I read and learn avidly on this forum...

A hit & miss control would certainly make the sound more realistic for a small shunting loco, between idle and loaded...but as I have difficulties with the carb, I hesitate to add further trouble with a hit & miss control !

No Roger, no piston rings, a long and plain cast iron piston with 4 oil grooves.
I will post some pictures of the parts.

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #10 on: May 28, 2020, 09:28:15 PM »
I put some pictures of the building of my little engine on my Google album

https://photos.app.goo.gl/aDQ5aQCqALkuMuGs9

I tested the electronic ignition made with a gas lighter as shown by Jan Ridders on his website, and it worked a treat,
I will do a neat lttle ignition box to replace the ugly coil and cable...


Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #11 on: May 29, 2020, 07:52:49 PM »
At the end of this link there are some pictures of Johan van Zanten's Gauge 1 Deutz mining locomotive with a 2cc engine.

https://www.model-engineer.co.uk/albums/member_album.asp?a=6778

It was also written up in MiM,

https://www.vth.de/maschinen-im-modellbau/unsere-beitraege/minenlok-mit-verbrennungsmotor


Best regards

Roger

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #12 on: May 29, 2020, 09:17:36 PM »
Thanks for the links Roger, spot on.
magnificent model, impressive work, a tiny Hit and miss to drive this little Deutz shunting loco, very akin to the models of Gail Graham.
A hit and miss engine is probably more comfortable to use...
but as my engine is running now, I will have a go with my version of the shunter, making a H&miss version of my engine would be a spare wheel, just in case...

Here  is the link for the PDF of the plan my little 4St engine.

https://ti1ca.com/7dzxwa8z-Gedeon-4T-v2-Gedeon-4T_v2.pdf.html

FM

Offline MJM460

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #13 on: June 01, 2020, 11:48:01 AM »
Hi Zephyrin, a beautiful little engine which will look and sound fabulous in your locomotive.

I have been thinking about the issue of governing the hit and miss action, and can understand that the tiny size might mean that governor weights will have too little mass to operate the valve latching mechanism.

Hidden in your locomotive body, a little electronic governor might be able to operate a mini-servo for the valve operation to get the miss part of the action.  You might be able to get pulses for a “count” for rpm by shining an infrared LED through holes in a gear wheel, or special wheel, onto a photo transistor.

There would be no need for a complex PID algorithm, simply a switch between two servo Positions based on high and low rpm limits with some hysteresis.   

The electronics can be made quote small, and you already have a battery on board if the processor power can be separated from the ignition system, otherwise a separate 4.5 - 4.8 V battery pack.

It could be easier to implement and more reliable than a conventional mechanical governor in such a small size.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #14 on: June 04, 2020, 02:50:27 PM »
Hi,
Thanks for advice MJM,
electronics, well, actually, I just dropped my homemade electronic ignition, really unreliable in my hands, I'll work on that...later.
But there are example of working " tiny" H&M regulated engine, by G. Britnell & Gail Graham, 3/8" bore size, that small!

I've rebuilt a new carb for my "Gedeon" engine, I don't receive electric shock anymore during the tuning of air and gas...phew!
I could add a tiny hole for air bleed when idling, to limit smoke, or make a new carb, in steel and longer to prevent vapour lock
my engine run fine, I'm having fun with it : I will do tests for a gear train for transmission...


But I find the torque a little bit just to move a loco forward, she will stall constantly...but I'm only at the beginning of the tests.

Cheers

Offline Admiral_dk

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #15 on: June 04, 2020, 09:19:30 PM »
I'm pretty sure Gail had a transmission with a gear reduction between his Tiny and the Loco's they are mounted in. This helps with the torque  :cheers:

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #16 on: June 09, 2020, 11:50:07 AM »
I've  tested my  little engine at work ;
 
somewhat better than at first, as he drives the bike dyno and produces light at the end, but if the rope (a large Oring) is just a little bit too tight, the engine stalls immediately upon switching the bulb on; it is due to few things !


Offline awake

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #17 on: June 09, 2020, 06:04:20 PM »
Very nice! I appreciated your use of a pump as well as a dynamo - haven't seen that before, but it gives me ideas!
Andy

Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #18 on: June 09, 2020, 06:28:48 PM »
Good stuff  :praise2:  :praise2: What output do you think you got?

I got around 16W from my 3cc 4 stroke single but at rather higher revs:

https://www.modelenginemaker.com/index.php/topic,2093.210.html

How the dynamo matches the engine can have quite an effect on what you measure.

Best regards

Roger

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #19 on: June 11, 2020, 08:14:50 AM »
Hi,
the power output of this bike generator, just an electrical alternator of poor quality, is not easy to calculate; I could maybe convert it in DC…
I would say about 2-3 W at most, for my little engine, working hard with this test.
with my little centrifugal pump, about 0.36 l of water were raised of 0.1 m in 1 min, we have : 0.36x9.81x0.1/60 = 6 mW, but obviously the engine was not overloaded…
« Last Edit: June 12, 2020, 07:06:38 AM by Zephyrin »

Offline MJM460

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #20 on: June 11, 2020, 12:56:39 PM »
Hi Zephyrin, I am another interested to see your engine driving loads to do something useful.

The problem with trying to calculate the engine power output in each case is the efficiency.  I am thinking about perhaps 50% for the pump, but the bike alternator, I really don’t know.  But at 50% the engine output driving the pump is certainly double that first estimate, and as you say it’s not working hard so certainly has lots more to give.

Another great video of a delightful engine.  Now for the locomotive body, some gears and off to the track.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #21 on: June 12, 2020, 07:28:56 AM »
thanks for the comments, greatly appreciated !
the locomotive, yes, I started to cut metal, progresses could be slow, as I should admit that I'm not fond of model making as long as it is not an engine...some nudge is welcome !

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #22 on: September 18, 2020, 09:35:04 AM »
Hi,
I have just finished a kind of gear box for my small 4 stoke engine, aimed to drive a gauge 1 little loco, with a diesel shunter aspect...

Instead of a centrifugal clutch, like the one found in RC cars, I installed a variable friction drive plate model, which allows to start the gear very gradually without stalling the engine as a driven roller moves from the center (neutral) to the periphery of a driver clutch plate (top gear). 
the result is more bulky than a traditional gearbox, but much simpler to build...
A set screw adjusts the pressure of the clutch plate on the roller. The O-ring is very stiff and the plate is well polished, which seemed counter-intuitive but works best; too soft rings were stretched under the pressure which can be very strong, and teared quickly.
This variable friction drive works satisfactorily, with neutral, forward and reverse gears.

But I have to add a positive lock of the speed control, which moves on its own towards top speed. 

The power available at the output shaft, which rotates at a speed of 1/10 of that of the engine and which will drive the wheels with a belt or a chain, is quite satisfactory, I am very pleasantly surprised even if it is in the range of 5 watt...


Offline MJM460

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #23 on: September 18, 2020, 11:10:36 AM »
Hi Zephyrin,

That a very impressive demonstration, and a great basis for your locomotive.  And the engine sounds like it could give a lot more if required.

It might be easier to control that variable speed drive than the winch!

It also looks like good progress on the locomotive chassis as well.  It will be running before you know it.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Admiral_dk

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #24 on: September 18, 2020, 11:37:31 AM »
Great demo Zephyrin  :ThumbsUp:

I might be overthinking it, but if you compare to a small scooter - you got the transmission 'in the wrong order'. On the scooter the centrifugal clutch is directly on the crank, followed by the variable transmission, followed by a reduction gear box. This ensures that you got very little tourque where you might otherwise have the biggest slippage, in order to reduce it. Well only time will tell if it will be a problem or not ....

Best wishes

Per

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #25 on: September 18, 2020, 08:42:56 PM »
Hi,
thanks for the comments !

Per:
What worried me was to see the engine stalling as soon as the clutch is engaged, I thought that this risk would be reduced with an already reduced speed, and a slightly higher torque...hence my first reduction stage.
I hesitated a lot, because you are right about the order of the transmission layout, I agree...
Anyway, the final system works well, but I find it very cumbersome, I have some modifications to do to make it more compact and to make it fit under the bonnet of the loco...and I am not satisfied with its style "Meccano" like, but it is true that my engine too, with a rather "agricultural " look is not well suited for its "industrial" destination either.!
I’m planing another tiny  engine more suited to this destination, once my loco will have made its first laps...