multicasting

Bob

w8ye

My Feedback: (16)

Sounds as though the low speed needle is in too far and restricting the action of the high speed needle

jaka

Hi!
First get ride of that 10% nitro fuel!!!
Use 0-5% nitro!!!
Use an 10x6 or 11x4 APC prop.
Use a 240cc tank, set up with uni-flow. Or better, a Tettra "Bubblelesstank".
Tank mounted according to "the tank mounting rule"! (The Tettra could be mounted further back though)
Use a Rossi 3-5 glowplug (or Enya 3-4 or OS 8, or Nova Rossi 3-5).

Check!
That the ball bearings are good (turning freely)!
I would have replaced them if the engine have sat for a long time (and have previously been run on Castor oil fuel.

C185Pilot

My Feedback: (25)

Get rid of the nitro...my Rossi's are really sensitive to it.

Mr Cox

Everything points to an obstruction of fuel, smoke and oil in the exhaust is not a good measure of anything...

Check the the low speed needle as suggested, otherwise take the carb apart and clean it. I have never had any dirt that could simply be flush out...

multicasting

Jaka,

Thanks for the tips. This is the same grade of fuel I ran in it successfully in the past. I actually keep a seperate fuel supply for my Rossi engines. I run 15% synthetic on all my other engines. I did switch to an 11X4 prop which made a desirable amount of thrust. I originally wanted a 12.25X3.75 but thought that might be too heavy of a prop. the 11X4 is a zinger which is very light. So I don't think it is the load. I would like to learn more about the Uni-flo and tettra tank. I amnot familiar with those. Running an OS-8 plug.

Bob

multicasting

This is what I am thinking.I guess I am going for the carb overhaul. Any thoughts on dopping a nice perry carb on there?

Bob

Turk1

It seems either a dirt in carb or an o ring leak in the carb.

Sport_Pilot

He is running it with a head shim. Does he need two?

blw

My Feedback: (3)

Why replace perfectly good bearings if the engine ran fuel with castor? I think this shows a misunderstanding of fuel lubrication. If an engine has been sitting after being run with castor, I either crank it up and run it a few minutes on the ground or put a little glow fuel in the crankcase overnight. Conversely, I would trust bearings with castor over those with pure synthetic lube.

DarZeelon

Quote:

ORIGINAL: multicasting

...I am running a 10% nitro with the extra head gasket and one extra glow plug gasket. This is my third Rossi and the other two run wonderfully with the same fuel and gasket set up.

Bob,


As others have told you, forget all you learned in good old USA about model fuel. This is a European engine.

Also, forget about the notion to use the same fuel in all your engines...
Different engines may have different needs in fuel. You would not use AvGas LL in your daily beater car, nor would you use Exxon auto unleaded regular in your Cessna Centurion...

Rossi engines run on fuel with 0-5% nitro and even for 5% you need the second head-shim (that you use). The extra glow-plug gasket will just make the medium OS #8 plug you are using 'bite' on less threads... You are risking your Rossi's head by adding that extra washer. Also, the plug is recessed as it is in the head, because this engine needs a 'long' plug.

This practice is just making it even more recessed... What did you try to solve by doing it?


Even if you have another Rossi that can be made to run on 10% concoction, stop doing it in this engine.

Quote:

When the engine is shut down, the case is between 330-350°F.

This is an unimportant piece of information.

With glow engines; if it runs right, IT IS at the correct temperature and its numerical value is of absolutely no importance...


Go to your LHS and trade that "worthless newbie trap" (your IR thermometer) for a good tachometer, or any other useful item.

Quote:

ORIGINAL: jaka

Use a Rossi 3-5 glowplug (or Enya 3-4 or OS 8, or NovaRossi 3-5).

Jan,


Rossi only recommend the R4 for this engine, but the R5 works very well, especially if a tuned exhaust is used.

The Enya #3 is too hot, but the #4 is excellent. The OS #8 is about the same heat range of the R4, but it is a 'medium length' plug and this engine needs a 'long' plug.
The Novarossi 3-5??? No way! This engine needs the Novarossi C-6S, which is the 'long', cold plug supplied by MVVS with all their 6.5 cc and larger engines.

jaka

Hi!
It's a fact that if an engine has been running on Castor oil fuel and sat for several years the ball bearings is so gummed up with oxidized (congeled ?) Castor oil that the crank can hardly be moved due to hardened oil.That's one of the reasons why racers change their ball bearings in their engines.

It is also a well known fact that too much nitro makes an engine very sensitive to needle settings! Remember this is an European engine and as such has high compression and run best on 0-5% nitro.

I admit that adding a head shim would make it run well on more than 5% nitro, but you cannot be sure! So why 10% nitro when the engine runs so well on just 5%...??

As for glow plugs ! I have run the Rossi .40 on many different glowplugs and have personal experience that the the OS 8 and Enya 3 works good when you run 0-5% nitro!

Using the the Uni-flow tank set-up is recommended for best engine performence(next to the Tettra)! It's just one more clunk in the tank! Nothing could be more easy to fix.

Of course there could be a hole in the tank, in the fuel line or a dirt particle in the high speed needle. Check this first!

multicasting

Darzeelon,

Thanks for the info. The extra plug gasket was installed back during the first time around. I had issued withburining outa plug on every couple of flights. The extra gasket stopped this from happening. If I understand this forum correctly, it seems the nitro may be the culprit for burning out plugs as all I did was reduce compression with the extra gaskets.

It is an old Rossi, so I will go pick up a bottle of FAIfuel. That's ironic that the least expensive fuel will give me the best performance in a high performance engine. I seriously doubt the bearings are damaged. I am very good about soring my engines. They are oiled and the ports plugged when in storage. I have had an engine bearing fail in flight on a YS-45 at full throttle. It was very violent.

I included the temperature because I was caught off guard by how how the engine was. The temp sensor is actually a highquality Fluke sensor. I don't think I will be taking this back to trade for anything anytime soon. But thanks for the reassurance on the temp. I thought anything above 300 was dangerous to these little engines. Perhaps I am not so familiar with the Rossi lines, but I respect the reputationof the brand, especially those from previous decades.

Thanks again.

Bob

multicasting

Jaka,

Thanks for the infomation! The bearings on the engine were not gummed up. It turned very freely when I brought it out of storage. I use a synthetic lubricant to store my engines. I have a shelf full of old engines. The tank and lines were the first thing I replaced. I am going to look into this uniflow thing. Also I will try some Nitro-free fuel.

Thanks!

Bob

DarZeelon

Bob,


OK. I get you on that Flukeâ„¢ temperature probe...
It is just that an IR sensor gives you redundant information; and has lately become an item 'shoved' by hobby shops to beginners that just don't know better...

Your old Rossi was not running right (obviously), so there was a possibility it was either too hot, or too cold...
Nitro rich fuel in a high-compression engine will cause detonation, which at first will cause the engine to overheat and ultimately to suffer permanent damage.

A temperature of 300°F may actually be rather hot, but at 149°C, is not close to the melting point of aluminium (660°C) and not close to the temperature that will weaken the metal either. Don't worry about it.


Glow engines will simply tell you, by changing their running characteristics, if they are too hot, or not.
A glow engine cannot run properly AND be too hot, at the same time...

Different engines run at different temperatures and the location of the reading changes it drastically too...

But again, this can be known without taking any measurements, so why bother.


As to the carburettor; the older Rossi type is 'an on-off switch'...
It can be adjusted to run perfectly at full-throttle and at idle; and to transition perfectly between these extremes...

But if you try running it at part-throttle, it will be rich to the point of stumbling and quitting on you...

This carburettor can be modified to run better in the mid-range, but I cannot give you more details.
Or you can change to another that will fit the 16 mm hole in the crankcase...

The new Rossi carburettor (much better) is way too dear, at over $100...

Sport_Pilot

Our engines cannot really be damaged from overheating. They could run at much hotter temps, such as when running on gas when converted. When we overheat them its is usually from a lean run, and its the lack of oil that kills them, not the heat. Although the friction heat may add to damage, the damage is not from the heat alone. When we overheat them in a cowled installation, its usually detonation that is doing the damage.

DarZeelon

Quote:

ORIGINAL: Sport_Pilot

Our engines cannot really be damaged from overheating. They could run at much hotter temps, such as when running on gas when converted. When we overheat them its is usually from a lean run, and its the lack of oil that kills them, not the heat. Although the friction heat may add to damage, the damage is not from the heat alone. When we overheat them in a cowled installation, its usually detonation that is doing the damage.

This is incorrect, Hugh!

It is NEVER *lack* of oil that constitutes the problem.


The needles in glow engines control the ignition timing. Yes, the ignition timing...

A lean mixture is quicker to ignite and the flame-front will propagate faster through it, than if it was a richer mixture.

Lean it a bit too much and the maximum pressure will arrive before the piston has reached TDC, causing the engine to slow down from peak RPM...
Lean it a little more and the advancing flame front raises the pressure prior to TDC, to the point of causing the yet unburnt remainder of the mixture to detonate...


Detonation will cause the lightest part; hence the piston, to heat and expand more than the sleeve, which has a greater mass and is cooled better by the cylinder and head fins.
The previous clearance between the piston and the sleeve, is taken-up by the now larger piston... The oil-film collapses and metal-to-metal contact occurs between the piston and the surrounding sleeve. Galling happens next and this means metal transfer.

This will happen even if the engine is run on fuel containing 35% oil! Even 35% castor oil...


The key words are 'detonation' and 'overheating'; not insufficient lubrication.

blw

My Feedback: (3)

A good reason to use castor if you have hot runs. Castor may gum up bearings a bit, but not enough to worry about unless you are using FAI fuel. Then, that should be 20% castor. A good mix of synthetic and castor, such as Morgan's Omega, would be a good idea.

MJD

My Feedback: (1)

Detonation? Don't you mean preignition?

MJD

DarZeelon

Quote:

ORIGINAL: MJD

Detonation? Don't you mean preignition?

No, MJD.

I do mean detonation...

Preignition is another phenomenon, which is caused by a hot-spot in the combustion chamber (of a spark ignition engine).

This hot-spot, which could be a sharp edge, or a spark-plug electrode, causes the mixture to ignite, before the actual spark.


A slightly over-advanced ignition in a glow engine, from slightly too lean a mixture, is similar to this.


Preignition, which occurs, will cause your car's engine to 'ping'. Your glow engine will also make a slightly audible 'frying egg' sound, if slightly too lean.


When preignition occurs very early, it could cause the onset of detonation.


In a car engine, it could result in heavy knocking and ultimately, a perforated piston, a broken con-rod, a blown head gasket and other damage.

In a glow engine, it causes a lean-run...

MJD

My Feedback: (1)

Fair enough.. I was wondering in glow engines if it actually progresses to the point where the reaction becomes true detonation. I only asked this, Dar, because of the hot topic that "pinging" and "detonation" are amongst motorheads. The explanations one finds are sometimes comical.

MJD

DarZeelon

This is true, MJD. Some explanations are rather hard to fathom.


While in my explanation describes how preignition can cause detonation, I ran into an article on the Internet, claiming detonation causes preignition...

It reminds me of how accidents cause trafic violations...

multicasting

Wow, lots of extra information here. My Mechanic friend also noted that preignition is usually referred to in engines with an ignition system. All glow systems (diesel, methanol) simply detonate when the pressure is great enough for the current mix. That helps me understand how the needle is responsiblefor timing. Simply put for my sake, Leaner = advanced.

OK, now back to my Rossi. I'll get some fuel this weekend and give that a shot. I still think I may have a fuel delivery problem as well. I haven't had time to look up the uniflow tank yet. It's back to school time, and I am busy both as a parent and a teacher! That's why I was really trying to get this worked out in early August when I still had flying time. Now I have a Super Chipmunk waiting for an engine as well. It's most likely getting a Rossi 60. Unfortunately I may have to go Pitts muffler onit to keep it in the cowl. It's worked so far on the Corsair.

Bob

DarZeelon

Quote:

ORIGINAL: multicasting

...All glow systems (Diesel, methanol) simply detonate when the pressure is great enough for the current mix. That helps me understand how the needle is responsible for timing. Simply put for my sake, Leaner = advanced.

Bob,


Let me illustrate this more clearly for you.

You have probably not been active enough in this forum, to see all the threads; where the glow-ignition process was elaborated upon.


The mixture in Diesel engines is ignited by high compression, which heats-up the air in the cylinder, beyond the spontaneous ignition temperature of the fuel.
Once the fuel is injected into the searing air in the combustion chamber, it self-ignites.
Glow-plugs are used in some true Diesels, only for cold-starting, since when the engine is cold; and especially at low ambient temperature, the fuel's spontaneous ignition temperature is much harder to reach by compression alone.
Once the engine is running on its own, the glow-plugs are no longer energized and they don't glow as a result of combustion either.

Ignition is achieved purely through the heat of high compression. A Diesel IS NOT a glow engine; it's a 'compression ignition engine'.

Model Diesel engine fuels, contain a large percentage of Di-ethyl Ether, which has a very low spontaneous ignition temperature.
So the required C/R for an engine using such a fuel, is not much higher than that of a glow engine.
No glow-plug is used, but an ignition improver (Amyl-Nitrate, Iso-propyl Nitrite, MEKP and similar materials) is frequently used in small percentages, to further increase the volatility of the fuel.


In a glow engine, the glow element is kept 'on the boil' by the break-down of methanol, when it comes into contact with the platinum in the coil.
This chemical process is exothermic and it's intensity is accelerated, as the temperature is increased.

If you dip a model engine glow-plug in methanol, nothing will happen, but at the temperature conditions inside the combustion chamber of a glow engine, the element glows bright orange and is hot enough to initiate combustion.

If a different fuel (without methanol) is used in a glow engine, or the glow element contains no platinum; the engine would only run as long as the plug is energized.
Unlike what many think, combustion heat is NOT sufficient to cause the element to continuously glow hot enough.

MJD

My Feedback: (1)

Being a propellant/explosives guy by trade, I always questioned the term "detonation" because in detonation, the reaction is propogated by a shock wave which travels at the local speed of sound in the media involved. I always figured the mechanism in IC engines was adiabatic compression and ignition in unwanted areas of the mixture causing drastic pressure spikes - as opposed to shock initiation. But one source says that shock waves have been recorded in gasoline engines. I was doubtful because I figured that true detonation would result in such severe pressure spikes that parts would start flying.. but I never have bothered to calculate the impetus of one fuel/air charge in the volume of a chamber and do the rest of the figgerin'.

This versus preignition which I understood as ignition somewhere else in the chamber from a hot spot or whatever, not necessarily transitioning into detonation or simulataneous ignition of the mixture all over the chamber.

Just thinking and wondering out loud - no arguments from me here. However, no question that the term "detonation" is misunderstood and misused 98% of the time. I even saw one of those Wiki motorhead "experts" say that explosion and detonation were the same thing . Luckily they are not, because otherwise everyone that ever tried to fire a handgun would have their hands blown apart.

MJD