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Sep 13, 2021, 08:56 PM
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Otakar's Avatar
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Magnum / ASP 61/65


I just picked up one of each of these gems. I do realize that they were built by the same manufacturer when they were available. I just wanted to know a bity about the specifications for these engines so I did some research on the www. The Magnum 61 is based on the same engine as the Magnum 53 and the ASP 65 is on the 70/80/90 engines. Here is the kicker. the two things the Magnum 61 and the ASP 60 have in common besides the factory are the bore and stroke. They both have a 24.8mm bore and a 20.6mm stroke. If you do the math then the displacement is 9.951cc (.607ci). So the 65 is not even close to the .65ci (10.65cc). I have been reading where people are comfortably running 16x6 and 16x7 props on the 65. I had a discussion on a different thread where I was being warned about running a 15x6 on a 65. I need to achieve a blade tip speed of +/- 350MPH on the 15/6 I would even be happy with 300MPH. This would mean an RPM of between 7K and 8K. I will have to do some testing but I might even be able to do that with the Magnum 53 or the RCV 59CD for sure. This is to power a 1/6 scale Fokker D-7 (58") On the other thread everyone is attempting to tell me to run a 11x8 or 12x6 on it. Heck, I run a prop that size on a 45 2-stroke. A K&B 45 loves a 12x6 prop. This one shmoo is trying to tell me that I should be running a 11x7 at 14K RPM. Why bother with a 4-stroke if you are running revs that high. I run my 2-strokes at 10K absolutely max. So according to factory specs, these two engines are the same displacement. I will measure them empirically to verify.

I guess what might determine which engine I will use is how much mass I will require in the nose. I definitely have enough room to hide completely any of these engines under the cowling.
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Sep 13, 2021, 09:12 PM
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Otakar's Avatar
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So all three of these 4-strokes are the same displacement. The RCV is a bit less on the bore and a bit more on the stroke. Mass wise the RCV falls between the two conventional engines.
Sep 13, 2021, 09:44 PM
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downunder's Avatar
Go to http://sceptreflight.com/Model%20Eng...sts/Index.html and you'll find tests on the ASP 61 (from 1990), Magnum 61 Pro (from late 1993) and the RCV 58-CD. For the ASP and Magnum, note the differences in the transfer port bulges.
Sep 13, 2021, 10:01 PM
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dan culv's Avatar
These engines require a lot of love.
Sep 13, 2021, 10:32 PM
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Otakar's Avatar
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I just pulled the heads off of both the engines and measured the bore & stroke. The 61 is correct in the instructions and specs but the 65 is not. The bore indeed is the same but the stroke on the 65 is 22.0mm This increases the displacement to 10.63CC which is just under the .65ci.
Sep 13, 2021, 10:34 PM
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Otakar's Avatar
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Quote:
Originally Posted by downunder
Go to http://sceptreflight.com/Model%20Eng...sts/Index.html and you'll find tests on the ASP 61 (from 1990), Magnum 61 Pro (from late 1993) and the RCV 58-CD. For the ASP and Magnum, note the differences in the transfer port bulges.
I am talking about the 4-strokes not the 2 strokes. There are no transfer ports on 4-strokes. The only 4-stroke from either Magnum or ASP is the little 32. Otherwise they are all two strokes in the reviews. I think you can tell that I am talking about 4-strokes from the pictures I provided. The irony about the RCV is that it was also built in the same factory.
Last edited by Otakar; Sep 13, 2021 at 10:47 PM.
Sep 14, 2021, 12:06 AM
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fiery's Avatar
I have a RCV 58 CD but have never run it. How does it compare to the ASP .61 FS?
Sep 14, 2021, 02:52 AM
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Quote:
Originally Posted by Otakar
I am talking about the 4-strokes not the 2 strokes. There are no transfer ports on 4-strokes. The only 4-stroke from either Magnum or ASP is the little 32. Otherwise they are all two strokes in the reviews. I think you can tell that I am talking about 4-strokes from the pictures I provided. The irony about the RCV is that it was also built in the same factory.
ASP was a bit fuzzy about their measurements and specs anyway: their Heli version .91 had according to specs a different stroke compared to their .91 aero version, which would suggest a different crankshaft. Now that crankshaft was indeed different, but ONLY with regard to the length of the threaded part (way shorter on the heli version). I know because I replaced the crank in order to fit a Heim clutch, and the stroke remained the same. Port timing (induction port in crank) also was identical.

So although I am amazed about the IMHO huge deviation (1,4 mm is quite a bit to be off), I am not surprised about the sloppy specs.

That heli engine, by the way, it was sold for 50 bucks brand new through HobbyKing, is an amazingly good running engine. Friend of mine had a Rossi 65 in a rather heavy scale ship, and replaced it for the ASP, lots more power and even better starting and handling than the Rossi, which frankly, is impressive because Rossi basically was the Rolls Royce among heli engines. Genuinely surprised.

Sorry for the off topic. Bottom line: don't be surprised if ASP/Magnum is a bit off in their specs. The engines themselves are solid. period.

On the bold: never knew that... I thought RCV was made in England?
Sep 14, 2021, 03:19 AM
Diesel Danny
danny mz's Avatar
Quote:
Originally Posted by Otakar
I just picked up one of each of these gems.
Not exactly gems, just cheap and reliable workhorses

With a bit of care they can row your boat and fly your plane

* danny *
Sep 14, 2021, 03:30 AM
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Quote:
Originally Posted by danny mz
Not exactly gems, just cheap and reliable workhorses

With a bit of care they can row your boat and fly your plane

* danny *
You're selling them short, Danny... Agreed, calling them gems is a bit too much, but to just call them cheap workhorses that need a bit of care also does not do them justice. They simply are fine engines for an excellent price, and I'll tell you what: I prefer them over the "gems" anytime, since lately (last 6~7 years or so) my experience with them is that they survive abuse an OS can't handle...
Sep 14, 2021, 05:47 AM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Quote:
Originally Posted by 1967Brutus
You're selling them short, Danny... Agreed, calling them gems is a bit too much, but to just call them cheap workhorses that need a bit of care also does not do them justice. They simply are fine engines for an excellent price, and I'll tell you what: I prefer them over the "gems" anytime, since lately (last 6~7 years or so) my experience with them is that they survive abuse an OS can't handle...
These engines ought to be able to handle a 17x8 or 18x6 prop, donít you think? Maybe a 20x6? That should keep the revs down to where the OP wants be I would think. Heck, I would put a 24x12 in it just to see what it would do. Inquiring minds want to know.
Sep 14, 2021, 06:23 AM
Diesel Danny
danny mz's Avatar
Quote:
Originally Posted by 1QwkSport2.5r
These engines ought to be able to handle a 17x8 or 18x6 prop, donít you think? Maybe a 20x6? That should keep the revs down to where the OP wants be I would think. Heck, I would put a 24x12 in it just to see what it would do. Inquiring minds want to know.
The con rod bearings might also want to know
Sep 14, 2021, 07:09 AM
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Quote:
Originally Posted by 1QwkSport2.5r
These engines ought to be able to handle a 17x8 or 18x6 prop, don’t you think? Maybe a 20x6? That should keep the revs down to where the OP wants be I would think. Heck, I would put a 24x12 in it just to see what it would do. Inquiring minds want to know.
Quote:
Originally Posted by danny mz
The con rod bearings might also want to know
I would not do that on glow ignition, but with a sparky box, no issues... I lug one of my engines down to 1500 RPM and so far, no issues.
Conrod on that one is fine...

I would have zero issues running one of these with a 14 x 6 or so, at least, when it is done the way I do it.

But that was not the abuse I mentioned... The beautiful HZ37 that crashed where the ASP HR36 remained whole, was not even used that far outside its parameters. Ran at normal loads and normal RPM, just had a sparky box installed and it could not handle the 20 deg C additional temperature...
Sep 14, 2021, 08:30 AM
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Otakar's Avatar
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Even though I still refuse to use gasoline and will always use alcohol, I might just try out a spark ignition with this model. You can now buy them for around $50 so it is not an issue. I will refuse to use it on my 1/6 cub with the Magnum XL30FS because it is tiny and I only plan on running a 11" prop on that, but this is a larger model with a larger engine and might just be the right "testbed" to try the spark ignition on. One thing I do not understand about the aspect of switching to spark. Most guys also switch to gas and use the 30:1 or even 50:1 oil mix. Why in the world should I be using my 10:1 mix? For glow, most people would consider that too little oil (I have been using it for years) but for gas it is way too much. The engine still requires the same lubrication so why the huge difference. 4:1 or 5:1, sometimes as little as 6:1 is considered normal for glow Fuel. This is why I never told anyone that I use 10:1. Just to avoid the comments and criticisms. I set my timing with the heat rating of the glow plug and compression. I like alcohol because I can replace some of the nitro with one of my secret additives, which will mix with alcohol but not with gas. This additive has as much oxygen as nitro and most people don't know about it and others never considered it. Plus you can buy this solvent for under $20/gal at retail in 1 gal containers. One other advantage of this additive is that it is 100% non toxic.
Last edited by Otakar; Sep 14, 2021 at 09:50 AM.
Sep 14, 2021, 10:34 AM
Registered User
Quote:
Originally Posted by Otakar
Even though I still refuse to use gasoline and will always use alcohol, I might just try out a spark ignition with this model. You can now buy them for around $50 so it is not an issue. I will refuse to use it on my 1/6 cub with the Magnum XL30FS because it is tiny and I only plan on running a 11" prop on that, but this is a larger model with a larger engine and might just be the right "testbed" to try the spark ignition on. One thing I do not understand about the aspect of switching to spark. Most guys also switch to gas and use the 30:1 or even 50:1 oil mix. Why in the world should I be using my 10:1 mix? For glow, most people would consider that too little oil (I have been using it for years) but for gas it is way too much. The engine still requires the same lubrication so why the huge difference. 4:1 or 5:1, sometimes as little as 6:1 is considered normal for glow Fuel. This is why I never told anyone that I use 10:1. Just to avoid the comments and criticisms. I set my timing with the heat rating of the glow plug and compression. I like alcohol because I can replace some of the nitro with one of my secret additives, which will mix with alcohol but not with gas. This additive has as much oxygen as nitro and most people don't know about it and others never considered it. Plus you can buy this solvent for under $20/gal at retail in 1 gal containers. One other advantage of this additive is that it is 100% non toxic.
For these small engines, 30:1 is WAY too dry, your bigend will last less than an hour. Larger engines with a roller bearing conrod are a different story, but these small thingies, they most definitely need more oil than that.
But you can use 10:1 even in as small as a .30, despite that being only 1/4th of the oil it would receive when running glow, because of two (actually three, but two are dominant) factors:
-First of all, the fuel (gasoline) itself has some lubricity, but what is more, it does NOT reduce the lubricity of the oil,
-Second, the oils as used for gasoline are a different league, compared to most oils used for glow fuel
-Third, the engine remains hot enough for water formed during combustion to not condense as much, AND the water and oil are not miscible (they are when glow fuel is being used).

When using alcohol, you can go safely down to about 15% oil when using spark, because whatever the case, the fuel still reduces the lubricity of the oil, and the alcohol causes the water formed on combustion, to still mix with the oil, reducing lubricity even further.
Alcohol is a mediocre engine fuel IF the engine uses a total-loss lubrication (oil mixed in the fuel), and even in circulation lubricated engines, using alcohol requires a bit of attention to lubrication details.

All that said, Otakar, just use the fuel you want. Use the type of ignition you want, not trying to talk you into anything here.
But whatever kind of non-toxic cheap oxidizing solvent you intend to use, from the list that I am aware of, and assuming you stick to class 1 or 2 and not higher, there are quite a few I would not want to pour into any kind of engine, unless I hated it... To be honest, ALL of them, achtually...
Last edited by 1967Brutus; Sep 14, 2021 at 11:34 AM.


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