ASP 36

I just bought one of these on eBay. Does anyone have any experience with this engine?

It looks like the Magnum 36XL. Is it really just a Magnum under another name? It has an unusual venturi - I believe from Just Engines in England. Will this work OK or should I change it to something more normal?

Leonard: Do you have a venturi that will fit. According to Granderson's Magnum set-up he used a .250 to .260 ID.

It probably is the same as the Magnum. I will e-mail you on the rest, but the new ASP (and Magnum) engines take a standard venturi. Why they made this change, I do not know, but all they are concerned about is holding the carb in.

That said, I am not a fan of the raised venturi/needle valve location. It may not be too bad up right or side mounted, but inverted they are hard to prime, not to mention they require a lower mounted tank.

I can't comment on the engine, but the NVA is the type I created for my Merco 64(bored out 61). I find it advantageous for several reasons. First, once the tank is set to the right height, it is easy to swap out the insert, complete with NVA for another insert of different size. This is useful when traveling to distant contests at different density altitudes. For higher altitude, just install a bigger venturi and I can nearly duplicate home field conditions using the same fuel. Second, let me call it an R/C spray bar, because I steal them from R/C carbs. The R/C spray bar can be screwed in or out from the baseline position to vary the venturi opening. Just loosen the jam nut, turn one full turn in or out, and tighten the jam nut. Again, I can nearly duplicate home field conditions. Third, the fuel draw is superior to a conventional spray bar. I refer you to Frank Williams article Mar/Apr, '95 when he was the power train man in Stunt News. And fourth, for an inverted engine, the needle is on the outboard, so you don't have to burn you fingers on the muffler and exhaust. Very convenient to needle with your left hand and hold the tach with your right.
If there is a drawback, Leonard, its in the choking. I usually turn the plane over to choke and prime the venturi. Flip a few times, then set the plane on the ground to start. As I recall at my last Nats, I had three one flip starts and one two flip start, so the actual starting isn't a problem.
Happy Landings

Where can I get one of these???
I'd like to try one out.

BobM

>I can't comment on the engine, but the NVA is the type I
>created for my Merco 64(bored out 61). I find it
>advantageous for several reasons. First, once the tank is
>set to the right height, it is easy to swap out the insert,
>complete with NVA for another insert of different size.
>This is useful when traveling to distant contests at
>different density altitudes. For higher altitude, just
>install a bigger venturi and I can nearly duplicate home
>field conditions using the same fuel. Second, let me call it
>an R/C spray bar, because I steal them from R/C carbs. The
>R/C spray bar can be screwed in or out from the baseline
>position to vary the venturi opening. Just loosen the jam
>nut, turn one full turn in or out, and tighten the jam nut.
>Again, I can nearly duplicate home field conditions. Third,
>the fuel draw is superior to a conventional spray bar. I
>refer you to Frank Williams article Mar/Apr, '95 when he was
>the power train man in Stunt News. And fourth, for an
>inverted engine, the needle is on the outboard, so you don't
>have to burn you fingers on the muffler and exhaust. Very
>convenient to needle with your left hand and hold the tach
>with your right.
>If there is a drawback, Leonard, its in the choking. I
>usually turn the plane over to choke and prime the venturi.
>Flip a few times, then set the plane on the ground to start.
>As I recall at my last Nats, I had three one flip starts and
>one two flip start, so the actual starting isn't a problem.
>Happy Landings

John's comments above are all valid. Once the engine is running, the venturi should work fine. He for got to mention, also, that the high needle will better accomodate a plastic tank, if that is what you like. If you are wanting to change out venturis, however, to accomodate different density altitudes (which includes temperature as well as actual height above sea level), changing out a "normal" venturi using a PA (Nelson) style needle valve is even easier. These needles have the nut on the opposite side of the needle. So remove the nut, slide out the needle, and change venturis.

I would also point out that these venturis are more complicated to make and will take a dedicated needle valve assembly for each venturi if you want several to swap.

It is true that you can adjust the RC type needle in or out to adjust the coke area (a plus) but you also need to make sure you are mounting them at the same depth if you have a range of venturis, otherwise the range becomes meaningless. Matt, for instance, has a number 12, 10, and 9 venturi that he swaps in his PA engine. But there is no spigot or needle protruding into the venturi at all.

The one disagreement I might have is with the greater efficiency of the spigot type venturi. The protrusion of the needle itself (or post, on a "true" type venturi) will disrupt the flow of air, so there is no such thing as placing this into the "clean" flow through the venturi. I have also read/heard that the greater flow is at the edges, not the center of the venturi. I would leave that point, at best, moot.

The biggest problem (the "ugly") in both what I and John have stated is the need to flip the plane over to more easily prime the engine. That is a hassle at worst, and a near impossibility if you are flying alone and using a stooge.

The good:
1) Easy change out of venturis with needle in place.
2) A higher needle location which better accomodates a plastic tank
3) The venturi is taller and easier to choke if using a large spinner. (Of course, if you need this, you can lengthen a regular venturi and place the needle in the normal locaton.)
4) The needle can be placed on the side opposite the muffler.

The bad:
1)If you use multiple venturis for changing sizes to meet conditions, you need a dedicated needle for each venturi.
2) A higher needle location which makes mounting of a metal tank more difficult.
3) The venturi is taller and sticks way out of a cowl if using a standard 2 inch spinner. Oh, and the needle also get closer to the prop, if that is a concern.
4). There is none. If you want to place the needle on the opposite side of the muffler, just bring the pick up out to the inside of the tank and reverse the needle.

The ugly
1) Higher cost per unit. (More work to make. Need a dedicated needle for each venturi)
2) Difficult to choke, and/or prime without flipping the plane over each time.

Will they work? Yes, most defnintely. Do you want/need one? That is up to you. Do you go for The Good, the Bad, or the Ugly? (Hey, this could make the title of a good spagetti western. I wonder if it has been tried?)

An Asp engine should go nice in an upcoming kit of the Cobra. Snake power.

I put the ASP in my Ringmaster to get some run time and flight time on it. It fits Fox 35 mounts, so the change was easy. It is a couple of ounces heavier than the Fox, so I added some stick-on weights on the tail.

The engine starts easily and runs smoothly. I was using a 10X4 APC prop to let it run high revs without much load to complete the break-in. I made one flight with it set very rich. Too rich to try any significant maneuvers, but it did break from 4 cycle to 2 cycle on climbs and dives. I left the muffler off to simplify starting and to limit the amount of weight added to the Ringmaster. I has a nasty sounding crack to the exhaust even in a 4 cycle. Engine is stock with the Just Engines venturi except for the addition of a .010 head shim.

So far, it looks interesting and will work some more next week with a tongue muffler and an APC 10.5X4.5 prop to see how it works. This may turn out to be the first supersonic Ringmaster! What the heck, in the "good old days" we flew them with Torp Green Heads and 9X7 props and no landing gears and thought they were trainers.
Steve