Having 3 of the fs-52 engines for many years, the first thing I did was tear down the new alpha before the postman made it down the street to my neighbors and around the corner!

My impression is that this is more than what other mainstream four stroke brands (non YS) do in a "new" engine It's not just "a bigger engine in a smaller case with the same bolt pattern" and it's not just the same technology with a different displacement. Here are some of the differences I see so far.

On my scale it measured 415 grams (14.6 ounces) and the muffler is 40 grams (1.4 Oz).

It will take time to tell how the new lubrication system will work, but I like it so far! Shouldn't be hard to tap a crankcase vent if someone really wanted to divert the system.

The carb is the easy to adjust and very reliable 40N model from the .52, the new intake stack mounts by a set screw... so it can be added to the .52 if you like. And other carbs with a 10mm neck o.d.

The camshaft is listed as the fs40/48 part #. Maybe someday I'll run a profile and see what the difference is.

The crankpin and wrist pin both are a bigger diameter! Though I've never had problems before.

The rear bearing is a completely sealed unit and the front is metal shielded.

Brass head gasket is .007" (.18mm)

The 56a has a noticeably larger intake tract compared to the 52, and the valve springs are MUCH stiffer (will help attain a higher RPM), two things I've been doing to my 52's for a couple years now, a very welcome addition.

The exhaust valve is larger in diameter, intake seems to be the same. However both have longer stems than before. The valve seat angle seems different, or maybe I just need to clean my glasses.

The new muffler looks like the orientation is very adjustable that will be nice. It can also be used on the .52, or anything with a 10x.75 thread.

The head no longer has brass/bronze valve guides and seats. The head is all aluminum alloy, however the combustion chamber shape is the same as before.

Am I missing anything? hehe

Overall my impression is O.S. deserves a pat on the back for always trying to improve on our model engine technology, it seems so far the changes they have made are for the better.

I will probably still use my mix of Marvel air tool oil and ATF into the fuel line while running the starter each time I'm done with it, old habits are hard to break I guess. Sometimes we never know when we're going to fire up a particular model again, some sit around for a couple weeks, some for years... so I just do it to be safe.

It's going to take some time to run through all the props I've got and get numbers on it.

Let's not use this as a O.S. versus the world thread please... no bashing...

Nice detailed analysis so far, More HP. Keep it coming!

More HP.

Great report - thanks a lot!

Thanks HP, if its a smoothy like the .52 it will be a winner. I just checked the Saito .56 stats, the OS .56 has a smaller bore and longer stroke at .945 bore and .811 stroke, the Saito .56 has a .970 bore and .74 stroke. When you run it, I'll try to do a head to head, same prop and fuel, I have two .56 Saito, one with considerable time on it and one barrely broken in. It's inevitable that they will be compared, it might as well be us that does it first.

It's a shootout... High noon in the middle of town!

I'm basically out of fuel stocks right now, been trying to decide for weeks what brand and mix to buy lots of. So for now I'll order up some of what your using Hobbsy, Wildcat 15% right? The premium extra 18% oil in the 80/20?

I was looking at the "Data" for the OS 52 and the OS 56a engines and the stroke is the same on he two engines. The 56a has a 1mm larger bore than the 52 and 48. The older OS 48 had a shorter stroke.

Right, if I remember correctly, the 48 was a bored out 40... then the 52 was the 48 bore with a little more stroke... now same stroke but a little more bore.

Once by accident I put a connecting rod in from a 40 in a 52, didn't realize it until much later and tore it back down (always seemed to run fine)... then saw that the 40, 48, and 52 use the same rod, Doh! Never would have thought with the bore stroke changes that they would have been interchangeable.

Like I mentioned above, the 56a rod is larger diameter on both ends, and the bottom is bushed, the top is not.

The difference in a 48 head and a 52 head is that the glow plug is recessed in the 52 head. All the unthreaded portion of the glow plug is inside the combustion chamber. This gives you about 300 rpm.

The push rod tubes are the same on a 48 and a 52.

The 40 cam fits in the 48 and 52

The 52 carburetor will fit perfect on the 48 with no modifications. So will the Magnum/ASP 52/61 carburetor.

Spot on, on the fuel, I also have PowerMaster, same nitro % and exact same lube %s. We might have to agree on a prop size, I think the OS .56 recommendations are a little heavier than the Saitos.

I just ordered the fuel, won't be here till the 10th or 11th.

I never had a 48 myself.

These are the props I have...

APC

12.5x6
13x6
13x7
14x4W
14x5N

Zinger
12x6-10

K-Series
12x8
13x5
13x6
14x4

Bolly carbon
12x8

I saw what they recomended too, some of these are out of line that I listed as well, but will be interesting to see what it's happiest with.

I gotta get back to work, somebody go flying for me, it's sunday for crying out loud!

HP, here are a few numbers for my newer Saito .56GK
Plug===GloDevil 4c Special
Fuel===Power Master 15/18% lube

APC 12x7========9,300 rpm
Bolly 12.5x6======9,500 rpm
Graupner 12x7====9,550
Graupner 12x6===10,450 rpm

The APC 12x7 made the engine sound "overpropped" from the instant it started. What's up with that?

IIRC, the reason the wrist pin and crank pin journals are larger is because OS skimped on using bushings in the connecting rod. True?


Ed Cregger

Ed, they did not skimp, the bushings serve no useful purpose. They're a total waste of money and material for a "feel good".

They started eliminating the bushings some years ago when they went to the high silicone aluminum connecting rod material.

Jim, how do those #s look when compared to your .56s, Thanks, Dave

I've kinda gotten away from keeping up with rpm's. I just go by sound.

I have three 56's but I also have two 50's and 4 OS 52's. I've been using one of the 50's and one of the OS 52's for a couple years.

I tend to fly the same plane until I wear it out. I've been flying your Ultra Stick 40 since you gave it to me 3 or 4 years ago.

Went flying all day yesterday but it was the Slow Poke with a OS 52 and the the Ultra Stick with a Saito 50.

I havn't run a 56 is two years.

The last time I measured a 56 was in 2001 or 2002 and mine was pretty consistent about being slightly above 10,000 with a APC 12-6

I remember the Magnum 61's being pretty close to the same power as a Saito 56. The OS 52 was down about 300 rpm.

I did finally use a MAS grey 12-6. I think it's going to stay on the plane?

I replaced connecting rod after connecting rod in my late Seventies K&B .40 and Fox .19 PB engines. Our club was on a synthetic oil only kick back then and I didn't have the time to track down a bottle of castor oil.

K&B then changed the connecting rod to include bushings at both ends. The problem went away entirely. Fox never did change, so I got rid of the POS. I don't have time to keep replacing parts that should be built better in the first place.

By increasing the silicon content in the connecting rods and by increasing the journal diameters of the wrist pin and crank pin, I can see how the engine can last a lot longer, even when running low or no castor oil. Still, I just think it is a cheap way out of a serious condition. Yes, I know that Saito changed to that years ago and I have to admit that I haven't heard of any Saito problems that are particularly related to the absence of a bushing. Still, I'd feel better if they were there...<G>

99% of what any of us believe as the truth is just opinion.


Ed Cregger

In our economic system, productivity improvements are continuously necessary for growth. "This means making it cheaper". Take the OS 46 AX for example. The AX does not have more power than the FX. It is a very nice user friendly engine. But it is a lot cheaper to produce with fewer head bolts and other design refinements that provide for fewer steps in production with more accuracy. Some of this is enhanced by CNC and the AX had CNC in mind from the inception. The biggest hit on the P&L balance sheet has always been labor and to eliminate people is another way of productivity improvement. This is brought about by automation. Then OS charges more for the AX and the new 56a being as they are the new improved model?

To use an improved rod material and eliminate the bushings was a method of productivity improvement.

Ed you will also remember the old K&B 61's had a forged connecting rod? Well, the present ones are machined from a billet slab then sliced off like slicing bacon.

Also the old OS Surpass four strokes had forged rocker arms. The 56a and the 200 have billet rocker arms

Ed, the rod doesn't seem to be manufactured any cheaper than the old rods that were bushed top and bottom. Even though the ends are larger, they kept the crank end bushed.

I quit work early today (shouldn't have!) and put it back together... Earlier I forgot to note the rocker arms are beefier in almost every dimension, did not get a chance to see if they would be a straight swap if someone wanted to upgrade, but they do look like real nice units without being too heavy.

Also when putting it all back together today I noticed that the piston ring is really stiff, didn't notice if it was any taller or deeper than normal, but right away it was very obvious how stiff it was.

You know, I get the impression with the bigger rod ends, stiffer springs, stout rocker arms etc. that O.S. has built an engine relating to how we are running them these days... the trend is to use low pitch props and high rpm for 3D type flying. Nice to see a manufacturer realize how the consumer is beating on their products! I think those changes are great, now let me tell you how it ran...

I used the same fuel blend as Hobbsy, and ran three 16 ounce tanks. Had a Zinger 12x6-10 for the first tank and a half then an APC 12.5x6 just to keep the load light. Kept the RPM below 7,000 for the first two tanks. Was able to get the idle down to 1,800-1,900. I really like the muffler, the adjustability is great, and might even be used with the old style 15 degree header if needed for more options in installation. You might want to keep a few of the o-rings as spares, or if you pull the baffle out just remove it entirely and smear some high temp permatex in it's place.

After the first tank and a half I pulled the valve cover off to check the valves, the intake only needed a tiny adjustment. What I was really interested in was how much oil was in there! The new lube path seemed to be doing it's job very very well. It's obvious that the cam, and followers get a lot of oil as it travels past and then up the pushrod tubes. I blew all the excess oil out of the head then put the cover on and ran it again for two minutes, pulled the cover and it was drenched again. It was impressive. Never seen that much oil in the top of a head before, not even in my ys-63s. (It has 4 holes around the intake valve guide)

Now here's what I didn't expect, I slowly started leaning things out a bit and playing with the throttle, at times it was running really well, but mostly I wasn't happy at all. So I kept tuning and playing and things got better, but worse at the same time. Idle was awesome for having such little time on it, but the midrange was pure crap, very rough and smokey. The top end was knocking and detonating like crazy so I richened it up and it blubbers, lean it out anything less than blubbery and it pings like mad again.

It was time for me to stop for the day, but as I was cleaning up I decided to try a quick compression test... 105 psi!!!! My jaw dropped, I said a few words that made my son gasp and I cranked on it again, yup, it was 105 psi. Normally everything I have runs from 60 to 75, sometimes 80, the exception being my FA-60t (I have three!) which always gets 40 psi no matter what I've done to it.

So my powers of deduction went to work again and this is what I came up with, let me know if I'm going in the right direction here... I've been reading for some months about piston ring design and function as well as how to make them. If a ring doesn't provide a good seal yes compression will be low no matter what the combustion chamber volume is (too much blow-by), but a good seal is also needed to provide ample vacuum to suck in the next intake charge, the better the seal then more vacuum is created, that's a good thing.

Just a few of the factors of an efficient ring design are...

1. The pressure the ring exerts on the cylinder wall, must be high and equal around the bore, but too high creates too much friction and that means too much heat, more heat means expansion of the material. Drastic examples of expansion would be end gap closing and touching, or ring thickness expanding and taking up all the clearance in the ring groove.

2. Clearance in the ring groove on top and bottom as well as the depth of the ring in the groove.

3. It's actually a good thing to have pressure go back across the top of the ring towards the bottom of the ring groove and get behind the ring during compression, and the theory is less leaks around that last corner at the bottom of the ring groove. That's what I've been reading but don't know how to explain very well.

I'm guessing the stiffness of the alpha ring is creating all this compression, it surely isn't the end gap, that measured somewhere between .007" and .008" which is huge for such a small bore. All that oil up in the head all over the rockers and an 1/8th of an inch deep in the "galley" means plenty of oil is blowing past the end gap. Maybe O.S. found that they needed high ring to cylinder wall pressure to create a larger vacuum in order to suck in the fresh intake charge as well as the oil returning from prior blow-by. I could be completely wrong about all this, would like to hear what you all think. If someone else out there has an alpha let us know what you experience!

I don't have any lower nitro fuel than 15% on hand to see if it runs better/smoother. Maybe if I can find the time in the next week or so I'll make up a thicker head gasket and try that, wouldn't that prove if my thinking is right or not? Maybe it's my thinking that is over compressed! hehe

Could it be early on in the production run that the ring just happened to turn out this way? My experience in trying to make my own rings has been a futile one, the tolerances, the heat treating/annealing, gap... it's crazy.

I've read elsewhere on this site that some think 100% recirculation of oil could be cause for pre-mature wear in the engine, after seeing how it works in the alpha, I tend to think if there is a problem in an engine creating alot of metal, that's a bigger problem than any lube path type could ever fix. If that's the case, any engine won't last long enough to worry about any recirculation of material through out the engine.

So for now dear Hobbs the only # I have for you is 9400 with that 12.5x6 knocking and rocking the whole time, it peaked at 9650. I'll have more later!

Hmm....$250 for this guy doesn't seem like such a great deal when you can get a saito 62 for $209 and get 9900 rpm on a 13x6. Thanks for the info MoreHP, I'm looking forward to hearing more on your findings. I want to like this engine so I'm hopping things get more positive.

Huh? Didn't mean to sound negative! I like this engine, It's going to be great, just need a bit more time to find what it likes for my tastes. Someday people are going to reminisce about the "old" surpass II engines.

What I think is overcompression on this one will be easy to deal with, rather than my FA-60t trying to go the other way for example.

I got my ultimate for less than $250, I found the Alpha for less than $209 (not much less).

This WILL be a great engine. It's going to be competitive with the 62a considering it has a little less displacement. I need more time cap'n!

Great reports MHP! Thanks.

Keep 'em coming.

Thanks Harry.

I just got my hands on an Enya .41 4 stroke diesel recently, it's completely NIB and I'm not feeling very comfortable about running it yet... Maybe I should try to run this alpha as a diesel instead!

Anyone else out there run an alpha yet?

---------------


Finally, someone mentioned the ridiculously high price. That was the first thing that I noticed. I generally like OS four-strokes just as much as Saito four-strokes. But the new styling and higher price will keep me from buying one of the alpha .56 engines. It isn't the money, it is the principle of the higher price being gouging.


Ed Cregger

Now I see that they raised the price, didn't take them long did it! Geez...