Someone needs to try them!  I suspect that the 46 will be all you ever need, and that the 35 (32?) will be enough for planes up to 550 squares, if they'll work at all.

This subject has been mooted about in other threads.  This is what I recall reading from the likes of Brett and Randy, tempered by what little I know about engines.

• You'll need to run them where they 'like' to run, which probably means a 3-pitch prop
• They may not be as versatile as the 46LA -- that engine is damned near magic
• They may benefit from a tuned pipe -- their timing is probably more like the first "tuned pipe" engines that were used in the mid '80's than the 46LA or any of our other current muffled engines
• It'll probably take some messing around to find a good combination, so you should probably figure on dedicating a contest season just to finding out the answer

Tim, I guess I need to take the plunge.

Interesting your observation about the pipe.  We've discovered the shorty pipes (Mac's, etc.) work really well with the .46, and that's one of the more interesting aspects of them.  The stock PowerBox muffler isn't too bad. For CL flying with no throttle we could remove the baffle and enlarge the exhaust hole, but the mini-pipe is lighter.

Maybe we should build one with a stunt venturi and and do some bench testing with different props and venturi sizes to get a feel for how it compares to other engines. That way I can be closer on the right sized squares for a ship.

Tim, I guess I need to take the plunge.

Interesting your observation about the pipe.  We've discovered the shorty pipes (Mac's, etc.) work really well with the .46, and that's one of the more interesting aspects of them.  The stock PowerBox muffler isn't too bad. For CL flying with no throttle we could remove the baffle and enlarge the exhaust hole, but the mini-pipe is lighter.

Maybe we should build one with a stunt venturi and and do some bench testing with different props and venturi sizes to get a feel for how it compares to other engines. That way I can be closer on the right sized squares for a ship.

Keep in mind that a good stunt run isn't about getting the highest power all the time -- it's about getting the best controlled power, that results in the aircraft speed staying relatively steady.  The best setup for RC, where you have your thumb on the throttle lever at all times, is almost certainly not the best setup for CL.

In fact, the major discovery that enabled the "tuned pipe revolution" in the mid '80's was that you wanted to use a "too long" (for RC) pipe with a small venturi and a "way too rich" (for RC) needle setting.  With that combination when the motor is unloaded some from level flight it will actually go slower, and when it is loaded up it'll go faster.  It's basically doing the same thing as a 2-4 run, only it's less sensitive to all the various external influences out there.

Personally I'd ask Randy Smith.  I'd tell him that I fully understand that I'm experimenting, then if he didn't hang up on me I'd just buy whatever he told me to get and try it on the engine.

I read some of the RC forums about the ASP engines.  The assessments were that they were pretty good engines but the bearings were cheap and wore out quickly.  Better aftermarket bearings look to be available.

I made contact with the guys at Just Engines since their website shows CL versions of the ASP engines.  The guys at Just Engines said the ASP is suitable for CL out of the box since the timing is conservative.  All that is needed if you don't want to mess with the carb is a venturi and needle, which they can supply.

I thought I would take a chance and bought an ASP 46 from Hobby King.  The needle and venturi I bought from Just Engines.  I could have bought both engine and needle/venturi assembly from Just Engines but I wanted to see if, by chance, I might already have what I needed to make it CL worthy without the carb.  But, since I had nothing on hand for the ASP I got the venturi and needle from Just Engines.

The ASP 46 is more like the ST 51 in outside dimensions.  It weighs 12.6 ounces with the venturi and needle assembly but without any muffler.  It is longer and wider than the LA 46 so nothing in my fleet is a suitable test bed aircraft for testing the engine for CL use.  I can't remove the LA 46 and install the ASP without some structural mods to existing planes.  If I think about it more I can probably come up with something but I have other projects to finish first.

I would bet that the power of the ASP 46 would come close to that of the ST 51.  The largest plane in my fleet now is about 570 squares and 55 ounces total weight.  The LA 46, with some minor mods, hauls it around just fine.  So, I think something like 600+ squares might be an appropriate size plane for the ASP.  Until I get around to making the mods to an existing plane I will never know for sure how it will perform as a CL engine.

Someone in my area might have a plane that they are willing to use as a test bed and if so I would be willing to have them install the engine and we can see how it goes.

I thought of getting the .53 but settled for the middle one, the .46.  According to the spec sheet, the 40, 46, 53 share external dimensions.  The 53 is 8 grams heavier than the other two, not enough of a difference to matter.  I think the 46 would be all I need.  If I can ever get it mounted on a plane and tested I will know more.

The ASP 36 might be a replacement for the Magnum 36 XLS.

Not so much with the  OS, but I have a lot with the Magnum Blue Head 52 ABC, real hard chrome, great quality and very powerful, more so than a ST60 by far
I have sold many of them, they fit the footprint of the OS SF 46, take the same size muffler also

Randy

From what I can see, the ASP .52 and Magnum .52 are indeed the same engine (different head).  Sanye (the mfg.) must put a different insert in the casting mould for the name.  My initial tests with the ASP .52 would confirm Randy's comment that it is more powerful than the Tiger .60 as mine pulls a 68oz Strega with authority.  It swings a 12.25x3.75 APC and I'm using one of Randy's tube mufflers.
I have several Magnum and ASP labeled engines (.15, .28, .36, .52) and these do appear to be very high quality (all true ABC).  I ran a .36 for years until a front bearing finally siezed.  They are quite reasonably priced and with Randy's or JE's setup are a great value.

Fred

Fred, how big a fuel tank do you need for your ASP 52?  This would give me some idea as to how big a tank the ASP 46 will need.

Are you guys still doing the Fermi Lab event?

Nearly three years ago (I think) I set up an OS55AX with a .284 dia venturi, an Aeroproducts needle valve assembly and a Tongue muffler from RSM.

I ran it on the bench and the results seemed to be very good, so I put it in an an ARF SV11.  It proved to be a very good flying duo but did need a little less venture area to soften the break a bit.  Actually I put a couple layers of pantyhose material on the venture with an o-ring and it proved to be just about perfect.  It's a fairly heavy engine so it required about 1 oz of tail weight to put the CG in the proper place.
A number of folks here in Tucson flew it including Bob Whitely and all were impressed with the capabilities of the combination.  It worked very well with a 13-5 APC prop.  A true powerhouse and would likely turn just about anything you put on it within reason.

I flew it for a while then went back to flying my GeoXL.   Around that time Chip Hyde had decided to get serious about CL stunt and came to Tucson to fly with the group here.  He was flying a very tired old ARF Nobler which he handily crashed because something failed on it ...pushrod maybe or something else in the controls.  To keep him flying and interested I gave him the SV11 with the 55AX and he flew it and flew and ended up taking it back to CA with him with the understanding that I would get the engine back when and if he wasted the airplane.  He continued to fly it until he got a couple of Crossfires from Mr Hunt.  At least that's the story as I heard it.  I did get the engine back and have it still.  It still runs very well even with a considerable amount of air time on it.  No appreciable wear.

It used around 5 1/2 oz of fuel to fly the pattern on 15% nitro 20% oil (yeah half and half)  Remember Tucson is high and hot!

I have so many projects working right now that I doubt I'll get back to it any time soon and I have a lot of engines.

At any rate the 55AX and probably the 46AX (although I have no direct experience with it) can be easily turned into an excellent Stunt Engine for largish airplanes.

You will notice that no grinding or replacement of parts of any kind except replacing the carb with a venturi and needle valve and a piece of mama's panty hose which could be avoided I think with a venturi diameter about .005 smaller than the one I used.  I suspect the engine would run a tad more powerful with the stock muffler but it's such a Boat Anchor I didn't try it.  Besides it ran as close to perfect with the little tongue muffler that it wasn't worth trying it.

Randy Cuberly