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[1967Brutus]

Well... I have to admit defeat...

The engine DOES need cooling.
I really don't get it, actually, because I have not seen this engine running significantly over 100 deg C (maybe 110 or so) while I have an identical engine in a plane (also running gasoline BTW) that happily chugs away at 135 deg C all day long, holds full throttle indefinitely and delivers approx 10 times the horsepower this thing does.

So I fitted a 42 mm computer fan (with a pro forma temperature control range from minimum speed at 70 degrees C to full speed at 100 degrees, but I have the strange feeling it will run full speed all the time, so... ).






The fan is currently powered by a separate 3S LiPo, current draw approx 90 mA so a very tiny battery allready suffices, but I intend to change that to a single 3S LiPo supplying fan directly and ignition and RX/servos via a voltage regulator.



Also a tiny modification done to the carburettor (a restrictor in the intake, "calibrated" to do nothing at low loads, but increase intake vacuum at high loads, increasing fuel draw when the engine has to work harder, a necessity for engines running a constant RPM). It looks ugly, nay HIDEOUS, but it works a treat.
It is a simple 1 1/4th" length of 1/8" diameter brass tubing, glued into "something to hold it in front of the (now useless) velocity stack".





And WHAMMO... suddenly the needle could be closed a fair bit more, smoothing out the engine, reducing the torque-roll and full power is now "endless" (it had a very strong tendency to cut out at full pitch, no real problem because it would run OK up to about 90% and I could live with that).

https://www.youtube.com/watch?v=j0Z5EHk_r7I


Prior to starting the camera there was a 4 minute warm-up run, where I also leaned the needle a bit.
After the vid I continued for about 4 minutes (all four of them full ahead) and then I checked fuel consumption: 7 ml... on a total tank content of 17 ml, meaning there's about 30 safe minutes in that tank.


I'm happy... I think... 

[JimG]

The engine in the plane will not overheat as it has a big cooling fan in front of it. Fully cowl the engine and block off the airflow round it it will rapidly overheat, open up openings in the front of the cowl and behind the engine it will then run at normal temperature. Cars and helicopters which don't have a propeller have much larger cooling fins on the head to try and keep them cooler with much less airflow. Your boat installation would need these larger cooling fins or a water jacket to stay at the temperature you want.(It's a little known fact that the propeller at the front of a plane is actually a cooling fan for the pilot, if it stops you will see him rapidly start to sweat. )
Jim

[1967Brutus]

Expectations met and exceeded, here's the maiden:


https://www.youtube.com/watch?v=Hfr7a31O0Tk

[1967Brutus]

The engine in the plane will not overheat as it has a big cooling fan in front of it.

I know how those things work,


the thing is that the aircraft version of this engine runs all day long at 135 degrees and full chat (200 Watt approx), this thing did not accept 110 deg C (while producing at best 20 Watt).

That's what I don't get. Cooling or not, temperature is temperature... And the cooling effect of this tiny little fan is minimal, I mean, the air movement is barely noticable, but the effect on the engine is disproportionally big. From barely adjustable, irregular running and requiring an overly rich mixture to nice smokefree, lean and as regular as a swiss clock. That's what I don't get...

[1967Brutus]

Dang... I just realized: This was a 13 day build, from bare hull to maiden voyage...

Still a lot of detailing to do, but neverhtheless... Crazy two weeks...

[1967Brutus]

Today I tried to determine fuel consumption a bit more accurate.


On the pond, so far it looked like about 24 ml/hr


Apparently (I did not expect that) propellers turn easier in a bathtub, because 15 ml filled to the tank, lasted for more than one hour at basically continuous full pitch...

Hmmm...

[1967Brutus]

Just for fun, AND a little bit to check if there ain't anything funky going on with the engine internals, a slow down of the engine sound (1/8th of original speed).

https://www.youtube.com/watch?v=5N2cbjF6nbQ

Suddenly it REALLY sounds like the real thing...

[1967Brutus]

Today I tried to determine fuel consumption a bit more accurate.


On the pond, so far it looked like about 24 ml/hr


Apparently (I did not expect that) propellers turn easier in a bathtub, because 15 ml filled to the tank, lasted for more than one hour at basically continuous full pitch...

Hmmm...

This fuel consumption seems to be consistent... that first test took 65 minutes to go through 15 ml of fuel, the 2nd test, 2 clicks richer, burned 16 ml in 61 minutes

[1967Brutus]

An impression of yesterday afternoon.

40 minutes on 10 ml of fuel, engine ran non-stop and never skipped a beat, despite having a bit of trouble to get warmed up (it was pretty chilly). Once it runs, it runs until either the fuel runs out or the prop tangles in waterplants.


The boat manouvres extremely well with the variable pitch propeller. Good fun!

https://www.youtube.com/watch?v=N1i9OioMMFw

[Backerther]

1967 Butus,The engine sound and speed seem matching very well for me and generating nostalgic atmosphere by the scene .
And the environment around the water way is also impressive as if I were in Huis Ten Bosch, so called theme park in Japan.
Well, this forum has become very international, hasn't it ...?? 

[1967Brutus]

1967 Butus,The engine sound and speed seem matching very well for me and generating nostalgic atmosphere by the scene .
And the environment around the water way is also impressive as if I were in Huis Ten Bosch, so called theme park in Japan.
Well, this forum has become very international, hasn't it ...?? 

Thanks, Back...

I had to google "Huis Ten Bosch" in that context of themepark in Japan... I was amazed, I was not aware of that.
But it goes to show that the Japanese have apparently built a VERY realistic themepark! For which I salute you guys!

[ChrisF]

Really nice result there. I have a river cruiser that runs nice and slowly with an electric motor but a model running slowly certainly benefits from an engine noise and if that's from a real IC motor than so much the better.

Chris

[1967Brutus]

Thanks, Chris!


Managed to get the governor response a bit mellower, reducing torque roll, and as I type, busy painting on the waterline.
Every day a little bit detailing.

[1967Brutus]

Thanks, Chris!


Managed to get the governor response a bit mellower, reducing torque roll

Here's a vid of that mellower governor response:

https://www.youtube.com/watch?v=EeExUNp7Gus

I also managed to determine that the controlled cooling fan actually controls... The fan speeds up if load on the engine is increased, balances at a constant given load, and slows down again when the engine unloads.

I have no idea what the actual running temperature (metal temperature, I mean) of the engine is, but the control range of the fan is from 70 deg C (minimum speed) to about 100 deg C. The probe is stuck between the fins of the head, approximately between intake and exhaust port, no idea what the misreading of the probe is... OTOH, I do not think the exact temperature is critically important for an aircooled engine, more important is that cooling supply follows cooling demand.

[1967Brutus]

reducing torque roll...

Anyone can judge for themselves...

Before:
https://www.youtube.com/watch?v=t8S6NmNbQz4




After:
https://www.youtube.com/watch?v=c9dG6fheH48

[Backerther]

Wow!! Certainly, greatly, realistically, stably, neatly, nicely, decently, dexterously, marvelously much improved,1967Brutus,!!
I don't now any other adverbs except the above to express my impression on the above awesome progress.
Well done with your tenacious efforts for the improvement.   But take much care not to drop her.!!

 

[1967Brutus]

But take much care not to drop her.!!

Sometimes I think people are claircoyant...

By accident I actually DID drop her a few days back, after painting on the waterline... Broke the portside bulkhead of the cabin in the process...

I nearly blew a gasket and an artery or two... [size=78%] Ooofh![/size]

[1967Brutus]

Last round before going back to sea. First real-world test of the new RPM control adjustments.

Increased maximum rudder deflection a bit as well.


https://www.youtube.com/watch?v=20EiBJfWSSo

I'm happy... See y'all in the next year!

[Kmot]

I remember your experiments with the ASP 30 FS over on RCG years ago. Nice to see it going in this lovely model boat! 

[1967Brutus]

I remember your experiments with the ASP 30 FS over on RCG years ago. Nice to see it going in this lovely model boat! 

Thanks Tom,


It has been an adventure for sure.
7 years ago or so I did a lot of work getting it to run in the first place, but back then the hull I had turned out to offer no more room for development.

The whole thing kept simmering in the back of my mind, and because of changes in my life I decided to take on boats for a while, and with that also resurrected the low speed engine project.

I think it turned out nice, and truth be told, technically I think I'm pretty much as far as I will get this project, but cosmetically, there still is a fair bit to do. And I have to say, every time I add a bit to that, it is as if I'm taking a new boat out. Pretty satisfying to be honest. And.... No stress...

[ChrisF]

That's what's keeping your interest going. Often once a model is finished the interest can lessen.

For many of us the research and building is the best part.

Chris

[1967Brutus]

Absolutely!


Although "operating a system" also has its charms, which is why I don't do electric main power, but something like this gasoline engine, or he steamboat I built a few months back. It keeps the mind alert when you have something to listen to and supervise. Piloting the boat around is not that challenging...

[1967Brutus]

The other day, I bought an exhaust gas tester (CO meter) for working on my bikes, and since the little fourstroke is VERY tricky to tune (the engine is governed, therefore it does not change RPM or exhaust note when changing the mixture) I was wondering if CO measurements would be of assistance.

Well, whaddayaknow... it does! I fired up the engine,as well as the meter, and found that it was running horribly rich at about 10% CO...
Previously, leaning out would not give any visible, audible or otherwise noticable change except that at some point the engine would start stalling.

But with the meter I could "relatively easy" dial it down to about 3,5% CO which turned out to give best RPM and governor stability without stalling the engine.

Hooking up the exhaust to the meter was a bit of an improvised mess (no vid or pics unfortunately, I needed both hands), but I managed to video the governor response with a properly adjusted carb. I could, thanks to this, remove the servo-slowdown on the pitch servo to zero.

The vid is narrated in dutch (sorry about that) but every time you hear me saying something, I am shifting the pitch from either neutral to full or from full astern to full.

https://www.youtube.com/watch?v=O4Mg61lg12w

The exhaust is also noticably less smelly and smoky...

[1967Brutus]

Slowly, VERY slowly, also some cosmetic work is being done...


https://www.modelbouwforum.nl/attachments/20240223_102911-1-jpg.572737/


It took a while, but the windows have finally been fitted (still need a bit of cleaning up of the sills) and the cabin door (not yet in place in the pic) has its latching magnet keeping it closed.

It ain't much, but it's progress at least...

[SteamboatPhil]

Looking good and getting there, tres bon