Castor blend ==>to==>Synthetic
09-16-2010, 12:43 AM
#27
Thread Starter
RE: Castor blend ==>to==>Synthetic
...that's what I was wondering. The longer and closer I looked at the head, things seemed solid. So perhaps it just is a casting flaw. Besides, I would think that if someone was beating this engine so hard before me, something else other then the pistion head would have given way long before hand (typically the piston ring or the bearings). Good call Jeffie.
09-16-2010, 01:12 AM
#28
Senior Member
RE: Castor blend ==>to==>Synthetic
Ichecked the Saito 100 Ihave in pieces here and it looks machined but yours looks like it is as cast. They probably just figured it was good enough.
09-16-2010, 04:45 AM
#29
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RE: Castor blend ==>to==>Synthetic
Nope thats not normal.
Pistons are cast and machined after for finishing. This piston looks as if the casting may be on the thin side as it shows some defpormation in the centre where the "Strech marks" are.
I'd replace it.
Club mate has a 150 Saito, and it broke a conrod last weekend fortunately it was kind enough to do so after he pulled his ShowTime out of the hover.
I am starting to have some reservations about Saito ...
Pistons are cast and machined after for finishing. This piston looks as if the casting may be on the thin side as it shows some defpormation in the centre where the "Strech marks" are.
I'd replace it.
Club mate has a 150 Saito, and it broke a conrod last weekend fortunately it was kind enough to do so after he pulled his ShowTime out of the hover.
I am starting to have some reservations about Saito ...
09-16-2010, 07:40 AM
#30
RE: Castor blend ==>to==>Synthetic
ORIGINAL: downunder
The difference is that our model engines don't store their oil in a sump so they're not using the same oil over and over again. Sumped engines need all the additive packages to help keep the oil in as good condition as possible. What applies to full size engines has no relevance to our engines, all we need is an oil that remains a lubricant at the temperatures involved and has the ability to handle the loads placed on it in areas like the rod bushings and between the piston and liner. Both synthetics and castor have their good and bad points but a blend of both can bring out both of their good points in what's called a synergy. [link=http://www.go-cl.se/castor.html]Here's[/link] a link to what's probably the very best article on oils ever written for model engines.
The castor/synthetic debate will probably go on forever but suffice to say that I've used castor for over 50 years in all types of engines with never a problem. Admittedly the castor I use (Castrol M) is very good and not available in most countries, like the USA or South Africa, in which case a blend is desireable. My only foray into synthetics was the 5 litres of fuel blended with a gas turbine oil that worked very well but the cost was too high to continue with it.
ORIGINAL: apwachholz
When I was chatting with myfiancéeabout my engine issues she mentioned it seemed odd that I would run aCastoroil fuel in an airplane engine after it's broken in. She's a pilot and mentioned that all piston aircraft engines that need to be broken in are done so with natural oil. But after the engine has been set (per a certain amount of running time determined by the manufacturer) she says they switch and stay to synthetics as they run cleaner and prolong your engine life.
When I was chatting with myfiancéeabout my engine issues she mentioned it seemed odd that I would run aCastoroil fuel in an airplane engine after it's broken in. She's a pilot and mentioned that all piston aircraft engines that need to be broken in are done so with natural oil. But after the engine has been set (per a certain amount of running time determined by the manufacturer) she says they switch and stay to synthetics as they run cleaner and prolong your engine life.
The castor/synthetic debate will probably go on forever but suffice to say that I've used castor for over 50 years in all types of engines with never a problem. Admittedly the castor I use (Castrol M) is very good and not available in most countries, like the USA or South Africa, in which case a blend is desireable. My only foray into synthetics was the 5 litres of fuel blended with a gas turbine oil that worked very well but the cost was too high to continue with it.
Actually in four strokes the oil is used over and over. No you don't have to change it. But the oil from the blow by will remain for some time before it is blown out the breather tube. For that reason and because there is no fuel air to cool the crankcase, it is common for four strokes to build up a good layer of castor varnish on the crank and bearings. More so than on a two stroke.
09-16-2010, 09:42 AM
#31
Thread Starter
RE: Castor blend ==>to==>Synthetic
Jeffie / TimBle -
Ohkay, I'm confused now. I was on Horizon Hobby's website searching for a new Saito FA-72 piston head and noticed that their pic of a new one, well...... looks like mine cleaned up! I'm not saying that I'm going to continue to use my current piston but, I emailed HH (i.e. the Saito experts) and asked them to determine if my head needed to be replaced or not. Look for yourselves. To me, the top of the piston head looks cast (as Jeffie said):
http://www.horizonhobby.com/Products...rodID=SAI8006B
EDIT:
Woah... ok, now i'm thinking it must be a cast.
Ohkay, I'm confused now. I was on Horizon Hobby's website searching for a new Saito FA-72 piston head and noticed that their pic of a new one, well...... looks like mine cleaned up! I'm not saying that I'm going to continue to use my current piston but, I emailed HH (i.e. the Saito experts) and asked them to determine if my head needed to be replaced or not. Look for yourselves. To me, the top of the piston head looks cast (as Jeffie said):
http://www.horizonhobby.com/Products...rodID=SAI8006B
EDIT:
Woah... ok, now i'm thinking it must be a cast.
- Open up a new browser window & click on the picture of my Saito piston head up close.
- Open up another browser window & click on the link above
- Click on the piston head photo to enlarge it
- Compare pictures
- Note the lower left of each pic - identical markings, especially the 'grooves'
09-17-2010, 03:57 AM
#32
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RE: Castor blend ==>to==>Synthetic
I would guess that the casting is intended to be thin. Thinking about it, the dome shape and stretch marks would disappear once the engine is up to temperature.
Idoubt if theres any advantage to having a piston crown that acts like a drum skin since this would just create nodes in the detonation shock wave and results in attenuation of the flame front (Energy lost to flexing the piston skin).
Will do some digging through old notes over the weekend and see if theres an engine out there somewhere that uses a similar design and why
Idoubt if theres any advantage to having a piston crown that acts like a drum skin since this would just create nodes in the detonation shock wave and results in attenuation of the flame front (Energy lost to flexing the piston skin).
Will do some digging through old notes over the weekend and see if theres an engine out there somewhere that uses a similar design and why
09-18-2010, 08:24 PM
#33
Thread Starter
RE: Castor blend ==>to==>Synthetic
Hey All -
I decided to reassemble the Saito FA-72 and take a little bit of a chance on running it for a weekend event at our flying club (see attached pics). Needless to say, it runs extrememly smooth and has an idle that is by far the best tuned idle for me to date. I am very pleased. After much consideration regarding the integrity of the piston, I double and triple checked the engine over and made a decision.
So now, I'm trying to work out the kinks. Primarily it seems that this engine needs to be run very rich.
Currently I'm not too concerned, but the amount of oil coming out the the exaust is the most I've ever seen. Of course, perhaps I could be running it very rich (right now I'm at 2 3/4 turns on the high speed needle) and need to work on the tuning. I'm running Wildcat 2&4-stroke fuel that is a 15% nitro / 18% sythetic oil (no castor).
Again, I'm not a fuel man and am learning so if anyone has any advice on possible other fuels to optimize my engine,I'm listening. Thanks all....
I decided to reassemble the Saito FA-72 and take a little bit of a chance on running it for a weekend event at our flying club (see attached pics). Needless to say, it runs extrememly smooth and has an idle that is by far the best tuned idle for me to date. I am very pleased. After much consideration regarding the integrity of the piston, I double and triple checked the engine over and made a decision.
So now, I'm trying to work out the kinks. Primarily it seems that this engine needs to be run very rich.
Currently I'm not too concerned, but the amount of oil coming out the the exaust is the most I've ever seen. Of course, perhaps I could be running it very rich (right now I'm at 2 3/4 turns on the high speed needle) and need to work on the tuning. I'm running Wildcat 2&4-stroke fuel that is a 15% nitro / 18% sythetic oil (no castor).
Again, I'm not a fuel man and am learning so if anyone has any advice on possible other fuels to optimize my engine,I'm listening. Thanks all....
09-19-2010, 10:44 AM
#35
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RE: Castor blend ==>to==>Synthetic
Andrew, try Model Technics DynaGlo. Its 10% synthetic, no castor and available in 10%, 15%, 20% and 30% nitro.Just be careful on the tuning side.
