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[Martin (Admin)]

  Paint or Hull crack? .... 

[1967Brutus]

  Paint or Hull crack? .... 

Paint and maybe the bondo, but the wood is intact as far as I can see...
But despite sanding down, the cracks kept sucking up paint.
So I applied a first pretty heavy coat, kept the cracks "wet" with paint for a while, and after 2 hrs applied a 2nd heavy coat, and the 2nd coat the cracks did barely draw in any paint.

With a bit of luck it'll be allright. If it isn't, I'll have to gouge out the cracks and fill them with 2 component glassfilled bondo.

While I was at it, I corrected the horribly misplaced "waterline".

Not bad, even if I say so myself.

[1967Brutus]

OK... the ignition parts landed this morning, so they could be on my doorstep as early as Tuesday (but probably not... :p ).

So I need to get the testbed ready...

[1967Brutus]

Apologies, I let posting here slide a bit in the last couple of days...

Monday around noon, to my amazement a courier knocked on my door, and there it was....

First of all those elusive tiny sparkplugs...

For those of you guys familiar with glow engines: On the right is a sparkplug in the standard thread for glow-engines (1/4"-32) and on the left is the amazingly tiny things this engine requires...



The nasty thing was that the kit as received, still basically was intended for the "large" sparkplugs In fact, it was a kit containing 4 large plugs, and the new smaller plugs were added in. Have to hand it to them chinese, no extra cost so I have 4 plugs 1/4"-32 for free basically), so the rubber caps supplied were loose on the new tiny plugs.
Also, for RF supression, 4 resistors 5K were supplied. Regular resistors, and how you want to install them is left to the imagination.

So here's what I did:

I cut one of the pins to half length, and ground it sharp using the Dremel.

This sharp end is stuck in the end of a HT lead


The other pin is coiled up using a small needle-nose pliers


Now I cut about 5 mm of silicone tubing (3 mm inner dia, 1 mm wallthickness) to make the plugboot fit snug on the porcelain of the plug, and stick everything together.






Now I had the issue, that the instructions (not supplied with the ignition kit, but on the vendor's website) still mentioned a ground cable, but this info was valid for a previous version. The new version did not have a groundcable, but silly me, it took me a day to figure out HOW that would work, and why.
Since I am slightly autistic (fo'realz) I did not dare powering up the ignition until I was sure I would not blow up the Hall sensor arrangement.

Next step was fitting that arrangement on the engine, and I've got to say, this all went together perfectly. Pretty nice design!


I was initially dissapointed that Cison does not use the RcExl (another chinese manufacturer of Model engine ignitions) standardized connectors, because I have a timing gadget for that brand...
But to my great surprise, the Hall sensor arrangement was fitted with LEDs, so this thing really is a doddle to set the timing right.
https://www.youtube.com/shorts/nz96OEWUXA0

Soo yesterday evening, I mounted the engine on my teststand, with just a tank for the coolant, no radiator yet (I have one, supplied in the ignition/starter kit) because that radiator has connections totally different from the connections supplied with the engine. So I have to first figure out how to fix that.
But I was guessing it would take a minute or two to warm up 250 ml of coolant, so for short runs, no problems.

Well... No more beating around the bush, no more delays:

https://www.youtube.com/watch?v=-GnA-3U9ap8

[1967Brutus]

I was counting on the heat capacity of the coolingwater tank to run the engine for short periods, but 250 ml of cooling water reaches about 70 dgrees within 2 minutes, and takes forever to cool down.

So I did include the fan and radiator in the cooling circuit. Basically, this radiator is laid out for just the heat generated during no load operation at very moderate RPM. It sure as heck won't be able to dissipate the heat generated when the engine is under load.

"As is" with zero regulationg or temperature control, the fan at full power will stabilize the temperature of the idling engine at about 60~70 deg C at the engine outlet.
https://www.youtube.com/watch?v=-kXbG0_pZ3A
This allready results in a delta-T over the engine of approx 25~20 deg C, so the cooling water flow is marginal as well.
Oil temperature seems to stabilize at about 60 degrees under these conditions, which is fair enough.

Although I most likely will run the engine with original pump set-up during the break in period, but will change to electrically driven pumps for the final installation. Because the first set of belts allready have snapped...

I ordered NBR 90 shore O-rings from a local supplier, 50 pieces, soi I can break a few...

Edit: just a few additional remarks...

-The engine is pretty much vibration free, starts extremely easy and is smooth. With a decent muffler, the sound is at very acceptable levels and I have the feeling a decent exhaust system also affects running behaviour in a positive way. Throttle response can only be described as "snappy" and "enthousiastic"

-The engine delivers an unbelievable torque allready at low RPM, if I had to estimate it might not beat a Robbe Power1000, but it darn well comes pretty close. In all fairness, I was amazed, especially given that the engine is yet a long way from being broken in.
It now has about 20, maybe 25 minutes of runtime, but compression also allready is really impressive.

-There are lots of small issues with it, but the basic design absolutely has potential. Those issues are a challenge to fix (if you're into that kind of thing. I know I am...) but once those fixes are done, it is pretty clear the design allows for to use this engine as a serious power plant for practical application, anywhere where "racing" or "speed" are at the bottom of the priority list. This thing seems to be made for pulling stumps. This thing can drive large boats.

[1967Brutus]

Since I cannot run the engine due to lack of "belts", and I had to do something due to lack of a better thing to do, I wasted a little bit time on an oil cooler of sorts.

I do not have the faintest clue it would need one in the first place, but given that virtually anyone running this engine is is either running it on the bench (no load whatsoever, or in a car model (exposed engine, air flow when at speed), but my application is in the enclosed space of a boat hull, I can imagine that there is very little empirical information availlable about oil temperatures and such.

The thought was that if it won't help, it won't hurt either, so first a little bit of figuring out how to arrange it, I came up with this:




Temperature controller is trying to keep enigne outlet temp constant, so increasing load will result in lower inlet temp.
I can select the coolingwater pump speed, so I can determine the range of inlet temperature (this is a fixed setting to be determined on the testbed)
By connecting the LO cooler in series before the cylinder block, and optimizing the waterflow through the engine, theoretically the oil temperature will also be around that range. It won't get colder than the cooling water inlet temperature, and it won't get much hotter either.
What is more: At increasing load, the inlet temperature is lowered by the temperature controller, so oil cooling is "controlled" without adding a 2nd control loop.

Again: No idea if it is needed, but it is just fun in itself figuring out stuff like this.

So I bought some brass tubing 6, 5, 4 and 3 mm OD, wall thickness 0,5 mm.
The outer shell is 6 mm tubing, the oil tube is 3 mm (2 mm ID like the rest of the oil tubing), the water connections are 4 mm OD (so 3 mm ID like all the coolingwater tubing) and the "bulkheads" are short rings of 4 mm and 5 mm tubing




The water connections are silverbrazed to the shell, the oil tube and bulkheads are Epoxied in with UHU Plus E300, oven cured.

In front of the engine for an impression of size:



And installed:



Cooling surface is approx 10 cm2

[1967Brutus]

So...
The wait was long and frustrating, it always is when you really REALLY want something, but the belts arrived early in the afternoon.

The good news was that I measured correctly, the bummer was that apparently I overestimated the quality (hardness) of the originals.
I ordered 90 Shore hardness, and although both string diameter as well as length were spot on, the new rings were extremely tight.
So instead of both belts driving both pulleys simultaneously, I let one belt drive the waterpump and the other drive the oil pump.
Due to the tighter fit in the pulley grooves, there was no visual slippage, so off we go, fuel, water, oil, electricity and fire it up.

The engine had about 20 or so minutes of runtime previously, and those were a bit interrupted with issues with the cooling pump (leakage, and when fixed the pump turned a bit stiff which killed the original belts).
This first run of today (3rd run overall), of about 20~25 minutes, burned 100 ml of fuel (still 50:1 ratio), and starting with clean sump oil, at the end of this run the oil appeared a bit too dark for my liking, so I changed the oil. There was no noticable oil consumption. The old oil was dark but not black and I did not see any sign of wear particles
The waterpump remained completely dry, and the belt had no issue with the stiffness of the pump, so that was a good thing.
I saw a minor leakage on the oil pump, it's not from the shaft seal but so far not yet identified or remedied.
The oil cooler seems to work, the oil temperature (measured on the oil pan) appeared to closely follow the water inlet temperature. So that is good also.
Total Runtime at this point about 45 minutes.

https://www.youtube.com/watch?v=zrU1uKIq4sY


The 2nd run of today (4rth overall) was about 30 minutes on 100 ml of fuel, because I leaned out the engine quite a bit.
Now the carb started to show the same nasty habits as the one on my gasoline powered Krick Alexandra (see "pleasure and sports boats"), very poor fuel metering capability: Fuel/air ratio remains nowhere near constant over the throttle range, forcing the user to set a slobbering rich idle in order to be able to rev or deliver power. But since I don't want to rev, and I wanted to brak in the engine as clean as possible, I set the mixture as lean as it wanted to go.
Resulting in fairly smokefree running, firing on all 4 barrels and a decent run quality (regularity).
This run brought the total runtime to 1 hr and 15 minutes, and the oil appeared clean enough that I decided to do another run with the same oil

https://www.youtube.com/watch?v=nIBzI1fCJ48

The lrd run of today (fifth overall, totalling 1hr 45 min) was not filmed, and nothing noteworthy happened.

At the end of the day I still had a tiny dash of mixed fuel, which brought total runtime to 2 hrs.
During this run I tried to get the lowest consistent run with the leanest possible mixture.
Take a look at the carb opening size... That's a 20,5 cc engine drawing air through that tiny opening...

https://www.youtube.com/watch?v=Yh-zcVJ9ohE

I am absolutely happy with how slow the engine wants to go without any modification whatsoever, and it still allows for some static load at this RPM.
Pretty sure it will pull the submerged prop at neutral pitch at this RPM...

The carburettor is going to be a challenge (but I have seen those before) but all in all the engine appears to be quite a strong one.

[JimG]

Could the carb problems be partly due to it's position at the end of the intake duct, this gives uneven distances between the carb and the cylinders. Therefore fuel takes longer to get to the end cylinder than the near one. Full size 4 cylinder engines will have the carb in the center of the intake duct giving a more symmetrical feed.
Jim

[1967Brutus]

Not as far as I can tell. Although the shape of the intake manifold to me also seemed a bit strange, as far as I can tell all four cylinders fire pretty even. There is no irregularity in the powerpulses and the echaust headers seem fairly evenly hot.

What I do know is that this specific type of carb has zero tendency to maintain a constant fuel/air ratio. Any change in parameters (throttle position or RPM or the relation between those two) the fuel/air ratio changes also. This forces the user to set the needle for the leanest practical condition (which is full throttle and high RPM) making ALL other throttle positions and RPM's rich to extremely rich. This in turn will cause the engine to load up.


There is a relative simple way to improve this, but the (for me irrelevant) downside is that the usable throttle range narrows considerably, which is OK, because I do not need 9K RPM and 3 horsepower. I need 1500 RPM constant, at varying load, and within this small sub-range of parameters, I need an as consistent as possible fuel/air ratio, in order to keep the exhaust as clean as possible: Nobody is going to like a boat that belches out blue foul smelling exhaustgasses and trails oil all over the pond.

That adaptation consists of a carefully calibrated  air restriction upstream of the throttle valve. Ideally that restriction does not have any effect at no-load condition, but when load is increased it should be large enoug to allow for that load, but small enough to create just a tiny pressure drop. increasing fuel draw in ratio with the increase in air induction.

It works on the single cylinder fourstroke in my Alexandra, it should work here.

[1967Brutus]

Last week I wrote:

This allready results in a delta-T over the engine of approx 25~20 deg C, so the cooling water flow is marginal as well.

I ordered NBR 90 shore O-rings from a local supplier, 50 pieces, soi I can break a few...

Yesterday I noticed that the delta-T was only about 8~10 degrees C and I can only conclude that the original belts, that were pretty stretchy and loose, allowed for some serious slippage on the pulleys. I see more signs of an increased waterflow, but they are circumstantial at best, not rock-hard proof or such...

[DHutch]

Lovely little engine! Love it.

[1967Brutus]

Lovely little engine! Love it.

You can own one too if you want...

[1967Brutus]

First  logistical announcement: The last video I posted, of the engine idling, I have finally been able to measure that RPM and it is below 750 RPM.
It actually amazes me.


Meanwhile I noticed that heat transfer to the carb affected running, and a heat insulating sleeve made out of Teflon improved things significantly. I need to re-do that with POM as working material.

Also, something I noticd was that the reockerbox basically was only lubricated by the smell of oil, and I don't like dry moving parts.
So I thought I might be able to fit an oil gallery over the rockers. Measurement confirmed that there was 2,7 mm clearance between rockers and cover, enough to fit a 2 mm brass tube in the cover.
In this tube, careefully aligned to run directly over the fulcrum shaft, 4 tiny 0,8 mm holes were drilled, located centered above each pair of rockers. The oil will drip on the shaft and spread from there.
This would look a bit like this:


Oil supply was branched off from the main line, by silvrbrazing a "T" out of 2 cm of 3 mm tubing and 8 cm of 2 mm tubing. After brazing and quenching brass gets as soft as copper. So easy to bend the 2 mm line such that it connects with the oil gallery.


And if you look closely, when I pull the filler cap, you can see some oil flowing over the rocker arm, oil that was not there before...
Valve lubrication for CISON OHV L4-205 (youtube.com)

[Martin (Admin)]

 
"only lubricated by the smell of oil"   

[1967Brutus]

Well, the valve lubrication was a bad idea: Heavily smoking engine and rapid drop of oil level, so that idea can be discarded.

Next issue will be carburettor temperature control.

The way the carb is fitted, direct metal to metal in the intake manifold, results in massive heat to the carb as soon as the hot engine stops, making a delayed restart impossible: Either immediately, or wait until things have cooled down completely.
When running, things tend to get inconsistent bcause of this: Every time the throttle position is changed, the balance between heat supply through metal-to-metal conduction, and the heat removal through evaporating fuel is disturbed, leading to wandering RPM.

A thermal isolator has an immediate positive effect on this, but the downside is that today (miserable cold weather with high humidity) I saw signs of carb freezing.
I don't expect this to become an issue in the boat (enclosed space, nice warm and comfy) but for benchtesting most definitely I need to adress this.
So next step will be active carb heating (piece of brass tubing epoxied to the carb body, cooling water return routed through this). Can be easily connected or disconnected, and the great thing about it is: when the engine runs, there is virtually immediate carb heating, when the engine stops, so does the cooling water flow, and heat soaking of the carb should be a non-issue.

Now I can hear you guys thinking: If you won't need it in the boat, why bother? but I can assure from exoperience that it is pretty imperative to go through all this in order to end up with a reliable engine as a final result.