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Jan 18, 2020, 12:55 PM
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Any engine on CDI should tick over reliably around 1200, but that's not a fair comparison to glow.

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Jan 18, 2020, 12:56 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by raleighcopter
800 on 3 blade IS 1200 RPM if there's only 2 blades.

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Yup and that was with a Super Tigre ST3000 running on CDI and Ethanol. The engine will only rev up to 7,800 rpm on the top end. I may even have it on a video on YouTube. I have to check.

I guess it is just like claiming who has a bigger car. A lot of exaggerated claims with RPM. Engines designed to idle and transition smoothly generally don't rev very high at the top end. Engines that are designed to achieve a high RPM at the top end like a ducted fan engine usually can't idle worth a damn. It is rare to have an engine that can run at high RPM and come down to a smooth low idle. That's the reason why I love engines that has the range. For that matter a lot of high revving engines don't even have a throttle to idle.

All these 2,000 to 20,000 rpm claims are just that. Speculations and conjectures. I really love to see some one show me a definitive video with a tach on the engine going from a reliable 2,000 rpm and rev all the way up to 20,000 rpm on an engine.
Last edited by SeismicCWave; Jan 18, 2020 at 01:04 PM.
Jan 18, 2020, 01:03 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by raleighcopter
Any engine on CDI should tick over reliably around 1200, but that's not a fair comparison to glow.

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That is the exact reason why I am doubting SLAM555's claim of a 1,200 rpm idle on glow and 20,000 rpm on the high end with his TT46. Also the some other claim that lots of engines can achieve 10 to 1 rpm ratio. If some one actually takes the time out to do some real life test they will find out that is a very hard milestone to achieve. That engine should be treasured. Any engine that can idle reliable on a glow plug to below 1,800 rpm is really really rare. Everything has to be perfectly tight with no air leaks, a perfect carburetor, nice compression, smooth bearing, perfect design, the proper porting. There are only so much an engineer can do to a 2 stroke engine to get it to idle so low. You can block off the muffler and shut off the fuel to minimum but you still need a flame in the combustion chamber.
Jan 18, 2020, 01:26 PM
Still gassin' it.
Sound can be very deceptive: I thought my heli engines idle very nice and low after CDI conversion, much lower than on glow…

Then I fitted a tach, just because I could….

2-stroke in helicopter, idle. (0 min 22 sec)
Jan 18, 2020, 01:51 PM
AMA 46133
SeismicCWave's Avatar
>>Sound can be very deceptive: I thought my heli engines idle very nice and low after CDI conversion, much lower than on glow…

Then I fitted a tach, just because I could…. <<

Sorry Bert but that did not sound like 700 rpm. I am not sure the read out was correct. At 700 rpm the engine should be just ticking over and you can hear the actual individual explosion. Then you will also have some misses in between. Since the tach is not displaying the full rpm do you think that is really 7,000 RPM idle?
Jan 18, 2020, 02:09 PM
AMA 46133
SeismicCWave's Avatar

Not a fair comparison and not glow.......


......but this is to give you some idea on what a 1,200 rpm idle looks like.

Super Tigre ST3000 gas coversion (1 min 26 sec)


You can hear that even with the CDI on gasoline the engine missed once in a while. There is no way an engine on glow plug can get that low. Secondly Even while the engine is idling pretty low the RPM only dip to 1,200 occasionally. Most of the time it was running at 1,300 to 1,500.

I believe this was the engine that I tached at 800 when I had it on the wrong scale with an hand held optical tach.

So when we talk about RPM ratio let's talk real numbers and not some imaginary numbers.
Jan 18, 2020, 02:19 PM
Still gassin' it.
Quote:
Originally Posted by SeismicCWave
>>Sound can be very deceptive: I thought my heli engines idle very nice and low after CDI conversion, much lower than on glow…

Then I fitted a tach, just because I could…. <<

Sorry Bert but that did not sound like 700 rpm. I am not sure the read out was correct. At 700 rpm the engine should be just ticking over and you can hear the actual individual explosion. Then you will also have some misses in between. Since the tach is not displaying the full rpm do you think that is really 7,000 RPM idle?
The tach reads in units of ten, so it was 7K...
Jan 18, 2020, 02:24 PM
Still gassin' it.
Quote:
Originally Posted by SeismicCWave
......but this is to give you some idea on what a 1,200 rpm idle looks like.
sub-1K...

Idle.... (0 min 22 sec)
Jan 18, 2020, 02:34 PM
Registered User
Monza Red's Avatar
Thread OP
"I hope to maiden a Flair Harvard this weekend powered by an OS 61 FS Surpass."

Nearly three years after I had fitted the engine to the airframe, I finally got round to maidening the Harvard this afternoon. I had been having some problems with the slow speed running of the engine, an OS 61 FS Surpass, but that was only a question of making a few mechanical adjustments and regulating the control throws on the transmitter, a Spektrum DX9.

I tested the running of the engine on the stand and measured the cg. It was 10mms in front of the recommended position but I finally ran out of excuses and decided to fly it anyway! It was fine, calm and sunny this afternoon but cold at about 7C or 45F. I turned up at the flying field at about a quarter past three. None of my club mates were there but I unloaded the van, filled the tank, started the engine, and took it to out runway. The wind had picked up and I began to have second thoughts, but I comforted myself with the thought that I am a competent and experienced pilot, although my experience with low wing models is not that extensive, besides I had a 10cc fourstroke in the nose so the model should be capable of handling a bit of a breeze.

I placed the model onto our tarmac runway and advanced the throttle, initially the model wanted to tip over onto its nose but I held it. It accelerated and then I watched amazed as the model took off and tracked beautifully in a steady climb. It required no more than a little aileron and elevator trim before it flew beautifully. I didn't try any aerobatics just circuits and eights but it flew beautifully. I've only fitted a 6 oz or 180 cc tank to it so I brought it in to a superb wheeler landing right on the "piste!"

As I was all alone I have no pictures of the occasion bit here's a pictute of the model on the stand, and another of our runway.
Jan 18, 2020, 02:53 PM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Quote:
Originally Posted by AA5BY
I'm scratching my head because I don't recall ever seeing an Enya .30. There were a lot of .35's and I still own a .29 and a .40. I was out of the hobby however between '84 and '01 so did miss a lot in those 17 years that included huge changes in RC engines and radios.

In my first ten years from '74 to '84, the most significant changes were mufflers were added to most engines and snurlle porting and the occasional Wankel and right as I exited, a chain saw conversion.

While I was absent, four strokes and gas engines caught on and huge changes in radios.
Enya makes the SS line of engines consisting of a .25, .30, .35, .40, and .50 I believe. The .25 & .30 is lapped or AAC, the .35 is ringed only (originally a heli engine, they have an airplane head for it), .40 lapped, and .50 ringed.
Jan 18, 2020, 04:12 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by 1967Brutus
The tach reads in units of ten, so it was 7K...
Wow, that's what I thought. I guess helicopter clutch will not engage until higher RPM.
Jan 18, 2020, 04:14 PM
AMA 46133
SeismicCWave's Avatar
>>sub-1K...<<

That sounds about right.
Jan 18, 2020, 10:08 PM
Registered User
Quote:
Originally Posted by SeismicCWave
That is the exact reason why I am doubting SLAM555's claim of a 1,200 rpm idle on glow and 20,000 rpm on the high end with his TT46. Also the some other claim that lots of engines can achieve 10 to 1 rpm ratio. If some one actually takes the time out to do some real life test they will find out that is a very hard milestone to achieve. That engine should be treasured. Any engine that can idle reliable on a glow plug to below 1,800 rpm is really really rare. Everything has to be perfectly tight with no air leaks, a perfect carburetor, nice compression, smooth bearing, perfect design, the proper porting. There are only so much an engineer can do to a 2 stroke engine to get it to idle so low. You can block off the muffler and shut off the fuel to minimum but you still need a flame in the combustion chamber.
it was 1200 to 12000 and I have a witness (if he's still alive) that help tack it up,
If you ever had a cloud dancer 60 you know that the idle better be low, otherwise it won't land
Jan 18, 2020, 11:26 PM
Registered User
Quote:
Originally Posted by Monza Red
"I hope to maiden a Flair Harvard this weekend powered by an OS 61 FS Surpass."

Nearly three years after I had fitted the engine to the airframe, I finally got round to maidening the Harvard this afternoon. I had been having some problems with the slow speed running of the engine, an OS 61 FS Surpass, but that was only a question of making a few mechanical adjustments and regulating the control throws on the transmitter, a Spektrum DX9.

I tested the running of the engine on the stand and measured the cg. It was 10mms in front of the recommended position but I finally ran out of excuses and decided to fly it anyway! It was fine, calm and sunny this afternoon but cold at about 7C or 45F. I turned up at the flying field at about a quarter past three. None of my club mates were there but I unloaded the van, filled the tank, started the engine, and took it to out runway. The wind had picked up and I began to have second thoughts, but I comforted myself with the thought that I am a competent and experienced pilot, although my experience with low wing models is not that extensive, besides I had a 10cc fourstroke in the nose so the model should be capable of handling a bit of a breeze.

I placed the model onto our tarmac runway and advanced the throttle, initially the model wanted to tip over onto its nose but I held it. It accelerated and then I watched amazed as the model took off and tracked beautifully in a steady climb. It required no more than a little aileron and elevator trim before it flew beautifully. I didn't try any aerobatics just circuits and eights but it flew beautifully. I've only fitted a 6 oz or 180 cc tank to it so I brought it in to a superb wheeler landing right on the "piste!"

As I was all alone I have no pictures of the occasion bit here's a pictute of the model on the stand, and another of our runway.
Congrats on the maiden....nice field.
Jan 19, 2020, 09:08 AM
Registered User
we' all love engines thats why we still fly with them it's interesting to hear all the stories though


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