Author Topic: a very small 4 stroke engine : 1.35cm3  (Read 1682 times)

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...