BaldEagel

I had trouble starting my 58 today, I have already turned the carb around so that it points up in an iverted installation, the choke was working and closing after every fouth flip, and then it occured to me that when I switched on the ignition I could hear the 1 second burst from the plug, I took the plug out and drained the fuel in the cylinder a couple of times and could still hear the 1 second burst, so I took the cap off agian and noticed the inside of the plug cap was wet, dried it out with some tissue paper, put it back on and when switching on the ignition the 1 second burst was much more subdued and I got a kick out of the prop, obviously I was tracking the ignition to the cap, second flip and away it went, moral of the story is make sure your plug cap does not get fuel in it when you take the plug out.

Mike

pe reivers

Mike,
Thanks for the story, and the warning.
You may have been lucky that the spark did not ignite the fuel in the cap.
With the carb pointing down towards the engine, it is easy to flood the engine. With inverted installation not such a good idea I think.
I like it simple, so I do not use the battery test, nor the choke feature. I have the choke on a transmitter operated servo so I am in command.

BaldEagel

Pe

I think I possibly very lucky the petrol in the cap did not ignite.
Good point on the down facing carb, perhaps a manual choke would be better, simple modification as the choke servo is already in place, trouble is now that I am on 2.4Ghz I am rapidly running out of channels on the DX7 and the Zap only transmitts seven channels on PPM or is it eight anyway its enough at the moment unless I install a smoke system which I doubt I will do.
Still all good fun, and still enjoying the performace of my MVVS engines.

Mike

pe reivers

I have 7 channels too, and none to spare for smoke, unless I make a manual choke.
choke
throttle
elevator (two halves, one servo pull pull wire system)
left aileron
right aileron
flap
tow hook

BaldEagel

My channels are divided:
Throttle
Rudder
2x Elevator
2x Aileron

So that only leaves the one for the choke if I take it off the auto function.
Funny you should mention the dual elevators off one servo and close loop system, I have that on a Weston Hype, pig to install untill you learn the trick of using a small tube from the tail end, but a very slop free way to control two elevator halves.

Mike

pe reivers

In this case, each pull wire (4 of) has a dedicated tube.
In a previous application, I had a branhed single tube, which took up all the wires. These were plastic coated, so I could do that.
In this plane the cable metal is bare, so I cannot run them into one single tube. It is easy to setup though, and provides rock solid neutral with slight play as the control face leaves center position. (cable fastening points behind surface hinge line)

BaldEagel

Pe

I only use a long tube from the rear of the plane to install the wires, I then remove the long tube and replace this with a short one at the tail end, doing this it is esential as you know that the wires do not touch and cause any RF noise, 2.4Ghz not effected obviously, but kevlar thread instead of wire gets over the problem as well.

Mike

pe reivers

same problem, different approach.
The drawback might be the larger free length of the wires. Vibration plays all kind of weird trick that you wouldn't dream of. Tubes can be supported, and will restrain the wires to close quarters.
Come maintenance time; As a side benefit, it is easy to route a new wire into the tube. The lead wire has no place to go except the end of the tube :-)

pe reivers

Back on topic "hard to start 58"

I had my 58 test engine on the test stand for a long time, and abused it a lot to get the power curves I wanted. In the process, the engine lost about 10% power, but always was easy starting. A few bumps against compression with choke on until the carb starts hissing, ignition on, and first or secont flick would get her going. Cylinder upright, carb angled up towards engine crankcase.

Now the engine is in my tow plane, carb orientation to the engine not changed, but the cylinder is down, so the carb is angled downward towards the crankcase.
The engine is not nearly as uncomplicated to start. It needs three full flips with choke on and ignition on to start and die. Then it needs a typical 8 flips to clear the lungs and start. I tried the carb hissing approach, but the engine is cowled in, and I do not hear so well any more. (old age creeps up on me).

At one time, the engine got completely flooded, so now I must be very careful not to move the prop in such a way that the pump operates and pressurizes the fuel inlet chamber. Taking heed prevented flooding from happening again.

Ergo,
With the cylinder in down position (not my favorite), one must be careful, and follow the rules by the book. Trapped fuel has no place to go but into the spark plug, and play havoc there, only to be solved by flipping the plane on it,s back and start the engine. When it does, it spews out the excess , and by now very dirty, gas through the muffler, and as Murphy will have it, onto the operater.[:@]

BaldEagel

Took the 58 Pro in my QQ Yak for an outing, the starting routine I have now addopted is to watch the fuel leave the tank whilst turning the prop, once it reaches the bulkhead I turn the engine over another three times and then switch on the ignition ensuring that I am well clear of the prop and the engine is at TDC, this gives a kick to the prop that occationally starts the engine, if not then a quick one or two flicks gets it up and running, after the first start of the day it seems to only need one or two flicks without any priming to get it stated.

The 58 Pro with the TDK 75K cannister pulling a 21 x 10 three blade seems to be an ideal combination, can't get it to stall in a straight line but when pushed on 3D rates it will flick into and out of manouvres with ease, and because of the excess of power available throttle management means this is the quirtest petrol plane on our patch, will have to take some more rpm figures and Db readings, may be interesting now its run in further.

Mike

pe reivers

Hmmm. That is the first time I heard of an advantage of the test sparks of the ignition, apart from refusing to start on weak batteries.
You are a brave man Mike. Don't forget to stay clear of the prop! I know how hard this engine can hit you when least prepared.

glofuel

Hi Mike,

Any prop readings on the 21x10 yet (RPM and noise), what make of prop are you using ?

I've been flying my YAK 54 86" for nearly 1 year now and after starting with the DA50 found it OK but was not particually impressed with the pull out from hover, so put the 58 Pro in and can't be more impressed with the setup. 99% of the time, easy to start and reliable with plently of power using the TDK75.

Been using a Beila 24x10 carbon which is about the max Dia 2-blade the YAK will take for clearence. Although not checked, I sure it is over reving at max throttle something around 7K+ which might explain why it is on it's third set of bearings and the gudgeon pin thru the piston is wearing, also noticed wear on the crank bearing journals, anyway after just breaking said prop (windy landing) was looking at using a 21x10 3-blade as Pe recommends but not sure if it would be suitable for 3D ?

Ian

pe reivers

The mvvs 58 has no max rpm limit that I know of. 7000 rpm certainly is not the upper limit. At 8000 rpm, the reeds start to be the limiting factor, and they start "snoring"
Your experience with wearing out bearings must have an other reason, that is unless you take the loose play bearings of MVVS for a worn bearing. Mvvs bearings have more internal play than the standard over the counter bearings, so the shaft feels like "floating", especially in a hot engine.
Can you please comment on fuel, oil used, cooling setup like cooling air baffles, air guide plates, air exit assistance etc. ?

glofuel

Hi Pe,

Petrol/gas is UK premium unleaded, Oil is Comma semi synthetic mixed 40:1 and cooling is good due to being mounted in a Yak 54 with front of cowl completly open, I can hold onto the cylinder after landing for some time.

Difficult to measure bearing play/wear, the front bearing seems to have more play than the rear, If I grab hold of the prop and rock it back and fourth viewed from the front, I would say that the prop tips move approx 1/16" when cold and when rocking the prop in rotation about TDC there is a lot more slack compared when it was newer, making a metalic rattle which sounds like conrod bearing at the piston end (gudgeon pin).

I have noticed when replacing the crankshaft bearing's that the crankshaft does show sign of the bearing's spinning on the shaft. Replacment bearing's used were good quality SKF/FAG and understand that some play is acceptable for good running but it does seem excessive.

Must admit having flown her yesterday she was running spot on !

glofuel

Oh and just for interest the engine has now had approx 10-12 gallons thru her and the gudgeon pin through the piston does have some wear seems to be wearing more at one end/side of the needle roller bearing ?

BaldEagel

..................

BaldEagel

ORIGINAL: BaldEagel

Glowfuel

As you know the weather has not cooperated recently in the Uk, so no readings yet, I am using a Mejzlik 22 x 10 Three blade, will try to get to the field this week and take readings.

Pe

Thanks for the quick delivery of the ignition unit for my 45, all up and running. The Hall sensor cable was detached inside the unit, I had obviously strained it somehow?

Mike

Supposed to be an EDIT, but I clicked on the wrong button.

glofuel

Mike, Yep know what you mean about the weather, sitting here looking out of the window wishing!!!

pe reivers

I do not agree with you on the cooling. A large opening up front means nothing, if the cooling air cannot exit well, and the airflow is not forced through the engine cooling fins.
In landing, temperatures drop so quickly, that decent in flight conditions cannot be judged anymore.

On the oil:
MVVS prescribes fully synthetic two stroke racing oil.
The Comma semisynthetic is quite a cheap oil for scooters, and also is quite thin, see
http://www.commaoil.com/MSDS/English...0synthetic.pdf
It has only 35 cStokes at 40 degrees, which is very thin. The MVVS oil has 90cSt at 40 degrees! The oils I tested all had 60 or more.

glofuel

Pe, I'am sure there's enough ventilation with a large exit aswell, but your comments on the comma oil does worry me and will change to a better brand, the only reason I went for semi-synthetic is because I have read and been told by reliable sources that fully synthetic can be too good and will not let the piston ring bed in properly in the piston bore but just polish the mating surfaces ?

Ian

pe reivers

I know that the large round cowls provide insufficient cooling if the engine is not baffled. This may be against your opinion, but that is how it is. The engine mounted on a test stand will also not be cooled well, and a large open cowl is no better. This is not my opinion, this is my experience after cylinder head temperature measurements.

The added metal salts in mineral semisynthetic oils provide some kind of lapping compound to get a smooth micro-surface, that you can do without. Good synthetic oils have sort of restructuring of the surface high spots without tearing metal parts out. The engines I inspected had a very nice pattern all around the ring, and no wear to speak of. The ring gap increased only 0.1mm after about 80 liters of fuel (~20 gals). his accounts for 0.03mm ring thickness wear, using synthetic oil from day one.
For engines with sloppy finish, this "lapping" may be needed. Not so with the precision finished MVVS engines.