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Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Looking for a decent engine

Old 05-24-2005, 08:55 AM
  #26  
bob27s
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Default RE: Looking for a decent engine

Personally, I still prefer wood props Ive never gotten seriously injured from a wood prop. I have, on the other hand, cut my finger badly simply removing an APC from its package. And, I once used a Master Airscrew 11x7 to slice up a watermellon at the flying field.

Master Airscrew blades are pretty well designed. I think, however, anything above their 11" size - I will avoid. I tend to prefer MA for seaplane use - they seem to hold up to water spray the best. The MA 9x6 was the standard prop for years in NEPRO Q-500 racing (K&B .40 engines).

APC offers the advantage of moredifferent sizes and blade profiles. Allows for matching the application better. Both the APC and Master Airscrew props (and other molded designs) offer consistancy as well.... the next prop will perform the same as the one you just broke (a characteristic flaw of wood props)

As was noted in the T-34 performance example above, prop selection is key. It is much like selecting a gear in a truck or car - allows the engine to perform best depending on whether you are driving up hill, over sand, in the woods, stop and go in city traffic, or cruising on a flat highway.

Matching an engine/airframe/prop for a given requirement is not always necessary. We all know the general rules of thumb as to what prop tends to work well with each engine. But when you wish to optimizes for max speed - take-off performance - lower flight speed - downline braking - landing braking - scale cowl - high drag - low drag - 3D - aerobatics - vertical climb ---- it is nice to have a wide variety of props to select from.

Good example ----- two very similar engines, very different jobs...
My SS-40 Q-500 sport engine runs at 21,000 rpm with an APC 8.5x7.25 prop. Provides the best take-off dash, and top end lap speeds.

My SJ-46 installed in my P-51 mustang with the turbo-jett exhaust, is turning a 12x4 14,000 rpm. Launches at 13,600. Provides outstanding take-off and landing performance with great airflow over the tail surfaces - LIMITS my top end speed and downline speed a bit for more consistant flight speeds at all throttle settings (more scale like) - and it provides a 1900 rpm idle This prop selected after trying everything from a 9x7, 10x6, 10x7 and a 11x5.... simply proved to be the best.

Also, where the APC/MA line also crosses, is the recommended max RPM the blade will see. In many cases, APC offers props better capable of the higher rpm and dynamic loads. Do your homework, and select properly for the engine and application.

Ok....... im done
Old 05-24-2005, 03:31 PM
  #27  
DHG
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Default RE: Looking for a decent engine

Gentlemen,

I wasn't talking about aerodynamics; I was talking about the material. I did NOT say Master Airscrews are poorly designed, inefficient, useless except as paint stirrers, or any of that. I simply said, do not spin them at high rpm because the MATERIAL they are made of cannot handle stress or vibration as well as the MATERIAL the APCs are made out of -- and especially at the hub, which, if you notice, has hollows in the back. You might assume (as I did) that those hollows are carefully engineered and that the tensile strength of the remaining material still gives plenty of safety margin, but you would be wrong.

Aerodynamically, they're fine. In fact, I chose a Master Airscrew for a cut-down bench prop because the airfoil and blade area at the hub looked better than any of my wood or APC props for what I wanted it for, namely moving air to cool the crankcase. But if I had known then what I know now about the length and composition of the fibers in the material, and the way glass-filled nylon will instantly fail when it reaches that magic combination of load, flex, and vibration, I would've thrown that thing as far away as I could.

You can happily run Master Airscrews for combat, or aerobatics, or as a replacement for the little cooling fan that came with your beach hat and water bottle for all I care. But you should NEVER, EVER use one for bench break-in or any other high-rpm/high-power application. If you do, you are looking at a bomb waiting to go off in your face. They can sue me for saying it, but truth is a defense. I have photos and witness statements to back me up.

Over and out.
Old 05-24-2005, 05:27 PM
  #28  
Flyboy Dave
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Default RE: Looking for a decent engine

That's all fine and dandy....but I have never heard of a MAS prop failing.....

....ever, ever. Every guy that has posted on these Forums that sliced his fingers,
hand or arm to ribbons....has done it with an APC prop. Every prop that has
thrown a blade is an APC.....never, never an MAS.

I turn MAS props to 18.1K static, and over 20K in the air....never, never a
problem. I can't understand why Guys try these scare tactics about MAS props.
The dangerous props are the APC's....they break easily, they throw blades, they
are way too sharp....and are just flat dangerous....plain and simple.

I won't stand for the premise that MAS props are somehow dangerous, more
so than any other plastic prop. I have been using them since they first came out
around '71 or so....they are strong, efficient, and reasonably priced.

I have taken MAS props off airplanes and replaced them, because they were so
beat up....and had been thrashed upon so many times they became unsightly.

MAS props are way, way stronger than their APC counterparts....

....anyone who has been to the field knows that. [X(]

Flyboy Dave....out.



Old 05-25-2005, 08:40 AM
  #29  
bob27s
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Default RE: Looking for a decent engine

Without going into detail, I have seen a number of the MAS props come apart. Yes, and elevated rpms that most r/c pilots do not see. Kinda something you end up seeing now and then with engines and testing stuff. Prop makes a god awful sound just before it lets go.

I have seen a few prop failures at the local fields over the years. They are rare.
In some cases, ambient air temperature may have had to do with it (plastic / nylon does weird things when cold)
In other cases, folks over-tightening the prop likely cause the failure.
In those cases, RPM was not a factor - all sport engines.

I think Duane has seen this too..... on APC props, you can visibly see fatigue in the blade. When one of the props develops a white haze look on the blade surface, usually toward the tips, its time to toss it into the garbage. They can and do fail, but they tend to give fair warning .
Old 05-25-2005, 10:26 AM
  #30  
Flyboy Dave
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Default RE: Looking for a decent engine

Well said ,Bob....and thanks for the input. It's no secret that only the special
racing props are rated for....and are safe for the higher rpms of the pylon
engines. I'm not a competition pylon racer. I do have club racing pylon racers
with "sport" 40's, .45's, and .47 engines. They turn in the 16-17K range, not
anywhere near the rpm of the racing engines.

bob27s
The MA 9x6 was the standard prop for years in NEPRO Q-500 racing (K&B .40 engines).
Don't the K&B's run up in the 18-20K range ? It seems obvious that if that prop
was selected for spec racing in AMA, that it is a safe prop.
__________________________________________________ ___________
Let's look at this "load" by our friend DHG, shall we ?

Aerodynamically, they're fine. In fact, I chose a Master Airscrew for a
cut-down bench prop because the airfoil and blade area at the hub looked better
than any of my wood or APC props for what I wanted it for, namely moving air
to cool the crankcase.
A cut-down bench prop ? What manufacturer recommends cutting down props ?
Answer none. They do not recommend "shaving, cutting down, or modifying
their props, anyone who ever read the prop instructions knows that.

You might want to "look again" at the APC prop. Does it not have extreme pitch
from the hub, out to about 2/3 the distance of the blade. Would it not "move air
to cool the crankcase."

But if I had known then what I know now about the length and composition
of the fibers in the material, and the way glass-filled nylon will instantly fail when it
reaches that magic combination of load, flex, and vibration, I would've thrown that
thing as far away as I could.
What kind of a load of bull is this ?....

"....glass-filled nylon will instantly fail when it reaches that magic combination."

Oh really ? What is the dreaded "magic combination"?

Should we all fear then, that maybe our Master Airscrew propellers will fail ?

You gotta love this "Domesday Report....
You can happily run Master Airscrews for combat, or aerobatics, or as
a replacement for the little cooling fan that came with your beach hat and water
bottle for all I care. But you should NEVER, EVER use one for bench break-in or
any other high-rpm/high-power application.
Oh, please....gimme a break.

If you do, you are looking at a bomb waiting to go off in your face. They
can sue me for saying it, but truth is a defense. I have photos and witness
statements to back me up.
Well, we certainly wouldn't have any "bombs" going off in our faces, now would
we ? I like the bit about the "witness statements" too....funny stuff.

Look Fellas....here's the bottom line. I'm a Moderator in this Forum, along with the
others. The trust of RCU has been placed upon me to insure that the messages
and statements posted on these boards is indeed factual and forthcoming.

You can quote me on this....I will not stand for kind of bull on my watch. These
kinds of lies and scare tactics about a perfectly good product will not fly around
here. Unless otherwise directed....I WILL take issue with anyone posting this kind
of bologna on the boards of RC Universe....

....I can promise you that.

Flyboy Dave.





Old 05-25-2005, 12:07 PM
  #31  
Paternguy
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Default RE: Looking for a decent engine

I firmly stand behind my wood props, If I need a plastic prop MA is my choice. The damn APC props are only good for removing fingers. LOL
Old 05-25-2005, 12:19 PM
  #32  
HighPlains
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Default RE: Looking for a decent engine

You might be the modertor, but you don't know much about the MAS failure that DHG is refering to. Had he not been wearing eye protection, it is most likely that the blade that gave away would have been embedded in his brain through the eye socket. As it was, he nearly lost use of the eye.

Cutting down props is often done to achieve a higher rpm for break-in. I recommend using a 10-6 WOOD prop cut to about 6" diameter for this application, so you have plenty of meat at the hub to hold it together. This is for when you need that 40 sized engine to turn in the 25k to 30k range.

Treating any high performance engine/prop combination like your sport engines is a great way to suffer injury or death.
Old 05-25-2005, 01:50 PM
  #33  
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Default RE: Looking for a decent engine

18-20K ?? If they did we would still use them !

The engines used for ages as the standard for Q-500 were the box-stock K&B 8011 and 4011 (torpedo .40 type). A REALLLLLLY good one would turn the MA 9x6 up at 16,000 rpm during the correct phase of moon. It wasn't till a few years ago that NEPRO jumped to the TT40 as a standard. A properly prepared TT40 turns an APC 9x6 on average at 16k - 16.5K rpm completely stock.
Old 05-25-2005, 02:27 PM
  #34  
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Default RE: Looking for a decent engine


ORIGINAL: HighPlains

You might be the modertor, but you don't know much about the MAS failure that DHG is refering to. Had he not been wearing eye protection, it is most likely that the blade that gave away would have been embedded in his brain through the eye socket. As it was, he nearly lost use of the eye.

Cutting down props is often done to achieve a higher rpm for break-in. I recommend using a 10-6 WOOD prop cut to about 6" diameter for this application, so you have plenty of meat at the hub to hold it together. This is for when you need that 40 sized engine to turn in the 25k to 30k range.

Treating any high performance engine/prop combination like your sport engines is a great way to suffer injury or death.
Yeah, what he said....

I too had one close encounter with one of the MAS props ..... just a 10x6 on a Rossi .40. Bounced off my field box, and took the hat off my head. fortunately I flinched just enough. As noted, I will not go into extream detail. Duane's experiences should not be taken lightly.

I too often modify props. You have to if intending to match the rpm setup for an engine, and it is frequently done for break-in. My tach and break-in props are all cut-down APC props these days.
Old 05-25-2005, 03:59 PM
  #35  
Flyboy Dave
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Default RE: Looking for a decent engine

ORIGINAL: HighPlains

You might be the modertor, but you don't know much about the MAS failure that DHG is refering to.

Cutting down props is often done to achieve a higher rpm for break-in. I recommend using a 10-6 WOOD prop cut to about 6" diameter for this application, so you have plenty of meat at the hub to hold it together. This is for when you need that 40 sized engine to turn in the 25k to 30k range.

Treating any high performance engine/prop combination like your sport engines is a great way to suffer injury or death.
HighPlains....let me see if I can make this perfectly clear. This thread started out
about a GMS sport engine turning about 16K.

I do not recommend the Members of RCU to cut props in half and then turn
engines to 30 thousand rpm with a whacked props. Is that what the safety
manual said to do....that came with that prop ?

I don't think so. That in my opinion is STUPID. If you and your racing buddies
want to act irresponsibly with your engines, and do all that crazy racing stuff,
that's fine too....I believe the safety manual states that injury can occur from
the missuse of the propellers. There are hazards involved with racing engines
and propellers....this is not a secret.

Was DHG running his equipment within the safety parameters set forth by the
manufacturer ? You Guys give us no facts....just blanket statements about
MAS props "blowing-up in your face".

I am sorry that DHG was injured, but there has not been any indication that
he was operating his equipment in a proper manner.

Again, I will reinterate....making blanket statements like...."MAS props should
NEVER, NEVER be used in a test stand"....is just plain phony, misleading, and
disingenuous.

Flyboy Dave.






Old 05-25-2005, 04:52 PM
  #36  
HighPlains
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Default RE: Looking for a decent engine

Hmm,

I thought the Forum was "Extreme Speed Prop Planes"

Having the knowledge on how to properly operate high performance equipment with the minimum risk should be your goal.

Perhaps you can scan one of these so call manuals and stick it to the top so we can all see.

When you have engines that operate at RPM's exceeding 25K in the air and you want to break it in on a test stand at the same RPM or slightly above, you use a special test prop. Plainly, Duane made a near fatal mistake in his choice of test club. I was exposed early to people who knew enough about these procedures to show me the correct methods. They had designed, built and operated high RPM engines for decades. I also worked for a propeller manufacturer that made a rather large line of speed props starting back in the 50's, so I think that perhaps he knew a thing or two about the subject.

Putting a smaller diameter and lower pitch prop on an engine to achieve the high break-in RPM is not safe. Why? Because the hubs are not sized to withstand the loads. Cutting down a larger wood prop is. Cutting down a plastic prop is not.

I'm not too concerned about my racing buddies. They operate under a pretty tight rule structure developed with safety in mind. What does bother me is the extreme speed mentality that does not have much experience and sometimes rather poor judgement
Old 05-25-2005, 05:43 PM
  #37  
DHG
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Default RE: Looking for a decent engine

Flyboy Dave,

Apparenty I was unclear on the concept of a "moderator."

The thread starts out with talk about breaking in engines at "extreme" rpm, with statements like "let it scream" and references to running BIG engines on "toothpick" props (I'll bet that's not in the manual) while guys' buddies holler at them to "shut it down, it's gonna blow" and they grin about it ... you encourage them by saying things like "You're a man after my own heart" and personally admitting to exceeding the manufacturer's own stated rpm limits -- not just once but habitually, and with pride. Then I show up and say watch it, that's dangerous, these things can let go suddenly, it happened to me -- and you call me an idiot with a "load of crap."

Who was it that was going to run a GMS .47 on an 8 x 6 propeller? Was it you, or one of the contributors? -- I guess it doesn't really matter. If you want "extreme" rpm with a prop in that size range, your choices are to (a) use a larger prop with a beefier hub and cut it down so it will spin, or to (b) just grab some tiny nylon thing off the shelf, with an even SMALLER hub, and trust it with your life. How am I stupid because I chose (a) ... and why am I a jerk to say that at least one, maybe all, synthetic props have a limit, and YOU HAVE NO IDEA HOW CLOSE YOU ARE TO IT?

Instead of passing along this friendly (although anxious) warning to your readers, or maybe asking for a few more specifics, instead you pound your chest and proclaim that you're going to "hammer down" the messenger who brings anything but sunny news.

Well, obviously, nothing will penetrate your thick skull except maybe a chunk of glass-filled nylon. Have fun, I'll watch for you on the local news!

Just Some Jerk
Old 05-25-2005, 06:33 PM
  #38  
Flyboy Dave
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Default RE: Looking for a decent engine


DHG

Instead of passing along this friendly (although anxious) warning to your readers,
or maybe asking for a few more specifics, instead you pound your chest and
proclaim that you're going to "hammer down" the messenger who brings
anything but sunny news.

Just Some Jerk
I'll tell ya what...when you Fellas figure out how to operate your equiptment
in a proper and safe manner....won't you come back and share that information
with us. Until then, I hope you will continue to enjoy RCU.

Have a nice day,

Flyboy Dave.
Old 05-25-2005, 07:59 PM
  #39  
daven
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Default RE: Looking for a decent engine

I am also a moderator of this forum, and I will side with DHG on this issue. The MA props perform fine and have some nice characteristics for props spinning less than 18,000 rpms. The racers out there consistently break 20k and the MA props just aren't up to the task.

If your happy with a 120 mph "extreme speed" patriot with Jett .90 it may be fine at 17k, but at 20+ you are asking for trouble with a MA prop. There is a reason that they are not allowed in even our lowest levels of racing classes.

You can say what you want about the speeds of either props, but I'm not aware of too many APC props failing at standard racing rpm.
Old 05-25-2005, 08:58 PM
  #40  
Ed Smith
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Default RE: Looking for a decent engine

Dave and Duane, you are wasting your time trying to educate these people. There are none so blind as those that will not see. They are all speed wannabees. As evidenced by their posts their knowledge of REAL high performance equipment is zero. The speeds they dream of would get any one of us last place at any decent racing contest!

Ed S
Old 05-25-2005, 09:57 PM
  #41  
Mike Connor
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Default RE: Looking for a decent engine

Both APC and MAS have their place in RC. I am sure they both have their good and bad points when used in different applications. It is starting to sound like the blind men arguing about the Elephant. Maybe it is time to close this thread. I see no winners.
Old 05-25-2005, 10:09 PM
  #42  
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Default RE: Looking for a decent engine

I agree Mike,

Consider this closed unless higher powers deem it necessary to re-open.
Old 05-25-2005, 10:30 PM
  #43  
Flyboy Dave
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Default RE: Looking for a decent engine


ORIGINAL: Ed Smith

They are all speed wannabees. As evidenced by their posts their knowledge of REAL high performance equipment is zero. The speeds they dream of would get any one of us last place at any decent racing contest!

Ed S
Thanks for stopping by, Fellas....us wannabes already know you hot-shot racers
are really big stuff. Remember to read the instructions that come with the really
fast engines, OK ? We don't don't want anyone else to get hurt from not knowing
what they are doing.

Hail to the racers....
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Old 06-06-2005, 12:12 PM
  #44  
Flyboy Dave
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Default RE: Looking for a decent engine

Here's some info from the MAS site....

C. RPM Operating Limits -
One of the differences between wood and glass-filled nylon propellers is that glass-filled nylon props have suggested RPM limits for mechanical considerations. This will vary according to diameter. For Master Airscrew props, we suggest the following formula: RPM Operating Limit = 160,000 divided by Diameter in inches. In our .40 size engine example, a 10" diameter g/f nylon prop has an operating limit of 16,000 rpm, well above the requirement of a .40 engine.
__________________________________________________ _____________________

The safe operating rpm for a 9" prop would be 17,777 RPM's, therefore it would NOT
be suited for racing engines in any case.

Flyboy Dave.
Old 06-06-2005, 12:16 PM
  #45  
Flyboy Dave
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Default RE: Looking for a decent engine

Here's the scoop here from the manufacturer....

http://www.masterairscrew.com/techbull.asp

Note: I added this info to this thread so Members could find out the facts.

Flyboy Dave.

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