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OS 46AX II v FORCE 46 ENGINE

Old 07-22-2022, 10:20 AM
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The Force 46(7.45cc) which produces about 1.6hp @ 16000 rpm, however there is another force 52(8.5cc) engine which produces the same power at around 12000 rpm, this tells me that the 52 will last longer than its smaller 46 sibling. Actually, having looked around I find this 52 engine desirable because it will fit my planes engine mount, straight drop in replacement and additionally it is only 20% extra cost on the Force 46 engine.

So there you go, just another diversion to the subject.

Last edited by 2W0EPI; 07-22-2022 at 10:37 AM.
Old 07-22-2022, 10:40 AM
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And having seen and run both, I can assure you it is at the very least the nicer engine... Although I doubt it will do 1,6 hp @ 12K. Maybe with a LOT of Nitro... stock and on more conventional fuels, I'd expect about 1,2~1,3 hp at that RPM, tops.
Old 07-22-2022, 11:00 AM
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Originally Posted by 1967brutus
Although I doubt it will do 1,6 hp @ 12K. Maybe with a LOT of Nitro... stock and on more conventional fuels, I'd expect about 1,2~1,3 hp at that RPM, tops.
Funny you should say but I have come across manufactures exaggerations quite routinely whilst comparing data between engines.But it's all relative, so I doubt the 46 will reach 16000 rpm as stated in the manufactures manual?
Old 07-22-2022, 12:28 PM
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Originally Posted by 2W0EPI
Funny you should say but I have come across manufactures exaggerations quite routinely whilst comparing data between engines.But it's all relative, so I doubt the 46 will reach 16000 rpm as stated in the manufactures manual?
Oh, it will reach that, because that is purely a function of which prop you fit... With an APC 10 x 6 or similar "ridiculous small" prop or so, it most likely will... And IF it does, it will punch out 1,6 hp, but with probably an unacceptable amount of noise, an awfully high fuel consumption, heaps of wear and tear and a prop that will not work very well on most common planes that could use that kind of output. I mean, a Wofgang Matt Saphir is a 180 cm wingspan aerobatic (I fly one, is how I know) would be perfectly powered with about 1,5 hp, but won't go anywhere behind a 10 x 6. That thing wants a 12 x 11 at 10K, works much better.
So the claims are not per se false, they are just outside the envelope of useful RPM and performance.

Whichever the case, 1,6 HP @ 12K, even the famous Hanno Special did not manage that, and that was a near 10% larger engine, WITH a tuned pipe...
(I know... the Hanno was tested by Peter Chinn at 1,8 HP @ 18K but that was without the pipe and on props FAR outside its recommended range. It was however sold with a factory-tuned pipe set up to do 1,5 hp @10K and things stopped there in real life applications. OS never released those numbers because they would hurt their claim of "strongest engine" while the base-engine for the Hanno Special, the RF, went to 2,1 hp)

Last edited by 1967brutus; 07-22-2022 at 12:32 PM.
Old 07-22-2022, 12:51 PM
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Hi Brutus,

Yes, you are right I'm using a 10x6 prop, bigger props reduce rpm because the load increases, so like you say top end rpm depends on prop size and the amount of twist.

Last edited by 2W0EPI; 07-22-2022 at 01:01 PM.
Old 07-22-2022, 01:33 PM
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Originally Posted by 2W0EPI
The Force 46(7.45cc) which produces about 1.6hp @ 16000 rpm, however there is another force 52(8.5cc) engine which produces the same power at around 12000 rpm, this tells me that the 52 will last longer than its smaller 46 sibling. Actually, having looked around I find this 52 engine desirable because it will fit my planes engine mount, straight drop in replacement and additionally it is only 20% extra cost on the Force 46 engine.

So there you go, just another diversion to the subject.
Which engine are you replacing for the Force 52? or Is it a new build your fitting it into?
Old 07-22-2022, 01:43 PM
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Originally Posted by 1967brutus
Oh, it will reach that, because that is purely a function of which prop you fit... With an APC 10 x 6 or similar "ridiculous small" prop or so, it most likely will... And IF it does, it will punch out 1,6 hp, but with probably an unacceptable amount of noise, an awfully high fuel consumption, heaps of wear and tear and a prop that will not work very well on most common planes that could use that kind of output. I mean, a Wofgang Matt Saphir is a 180 cm wingspan aerobatic (I fly one, is how I know) would be perfectly powered with about 1,5 hp, but won't go anywhere behind a 10 x 6. That thing wants a 12 x 11 at 10K, works much better.
So the claims are not per se false, they are just outside the envelope of useful RPM and performance.

Whichever the case, 1,6 HP @ 12K, even the famous Hanno Special did not manage that, and that was a near 10% larger engine, WITH a tuned pipe...
(I know... the Hanno was tested by Peter Chinn at 1,8 HP @ 18K but that was without the pipe and on props FAR outside its recommended range. It was however sold with a factory-tuned pipe set up to do 1,5 hp @10K and things stopped there in real life applications. OS never released those numbers because they would hurt their claim of "strongest engine" while the base-engine for the Hanno Special, the RF, went to 2,1 hp)
The Hanno Special was only produced as a 61 Right??
Old 07-22-2022, 11:45 PM
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Originally Posted by Eastflight
The Hanno Special was only produced as a 61 Right??
Correct... It was a bit of a "mystery engine", that OS never published any output specs on, and therefore it became more or less a mythical object. Like "The most powerful engine mere mortals can buy" or something like that.
Reality was that it was not particularly powerful, the only thing it did really well, was produce relatively lots of power in the lower RPM ranges. And the only reason it had to, was that back then (end '80's, early 90's) noise level was also taken into account in international competition, to such an extent that no matter how good a pilot, a noisy plane would wreck all chances of ending high at the end of the day.

NOT saying that Hanno was a mediocre pilot that won thanks to his quiet engine, don't get me wrong... He simply was the best pilot out there at the time. But he simply did not take any chances having a good score ruined by a noise limit penalty.
Realistically, two identical planes, one with the Hanno Special and the other with a standard RF, performance-wise the RF would run circles around the HannoSpecial hands down, but the noise penalty would make it extremely difficult to win competitions with the RF.

Most people buy an engine, see the specs and think "great, my plane has XX horsepower installed", but it does not work that way. Not even close. Those are just numbers of what is theoretically possible. Not of what is practically availlable. What is practically availlable depends on the RPM the prop allows.
Old 07-23-2022, 12:41 AM
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Originally Posted by Eastflight
Which engine are you replacing for the Force 52?
I've bought 2x Force 46 engines so far, but I should have gone for the Force 52 because it will fit my plane and it would last longer than the 46, also its price is right.
Old 07-23-2022, 05:25 AM
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So true!
Old 07-23-2022, 10:36 AM
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Actually, I have just checked my boomerang 2 manual and it explicitly states 40-46 only, so a 52 is going to be too big unfortunately.Originally I had my heart set on Fairchild pt19 by Seagull models( I see Seagull models as basically quite good) the problem I have is the Fairchild PT19 is both complex to build and fly as it consists of 5 servo's for total control, the extra servo is needed to control ailerons independently giving separate control for each wing aileron. So the flyer gets an extra 2 functions. This plane can take 46-52 engines so the Force 52 should fit perfectly, but the engine has to be mounted upside down(due to its cowl), making glow start adapters mounted from the ground up would be a bit awkward.
Old 07-23-2022, 10:40 AM
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Originally Posted by 2W0EPI
Actually, I have just checked my boomerang 2 manual and it explicitly states 40-46 only, so a 52 is going to be too big unfortunately.
Nah... it will fit.... I have this VQ SpaceWalker, and it was seized for .45, or .70 fourstroke. Trust me, where a .70 fourstroke fits, a .52 2-stroke will fit as well. (And I went ahead and fitted a .90 fourstroke anyway).

The power won't hurt the plane, and if you don't trust it, a layer of glassfiber/epoxy on both sides of the firewall and you're good to go.
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Old 07-23-2022, 10:50 AM
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Originally Posted by 2W0EPI
the problem I have is the Fairchild PT19 is both complex to build and fly as it consists of 5 servo's for total control, the extra servo is needed to control ailerons independently giving separate control for each wing aileron. So the flyer gets an extra 2 functions.
Not sure what you mean by that, because those two ailleron servo's only serve to avoid long mechanical linkages. They are however both simultaneously controlled by the same ailleron stick, so they won't place ANY additional workload on the pilot, NOR make the plane more complicated to fly. Most people simply use a Y--harness to connect both servo's to a single RX output. Some use a separate output and connect both outputs in the TX programming.

Originally Posted by 2W0EPI
This plane can take 46-52 engines so the Force 52 should fit perfectly, but the engine has to be mounted upside down(due to its cowl), making glow start adapters mounted from the ground up would be a bit awkward.
There are very affordable "remote glow connections" that allow for a fuselage mounted socket connected to the glowplug. Very simple, and absolutely no issue.

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Old 07-23-2022, 11:11 AM
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Well, Brutus, thanks for the input, you have provided some solutions to my concerns, thank you much appreciated, will have to have think about it.
Old 07-23-2022, 11:30 AM
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You're welcome! That is what a forum is for...
Old 07-23-2022, 01:56 PM
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Originally Posted by 1967brutus
Correct... It was a bit of a "mystery engine", that OS never published any output specs on, and therefore it became more or less a mythical object. Like "The most powerful engine mere mortals can buy" or something like that.
Reality was that it was not particularly powerful, the only thing it did really well, was produce relatively lots of power in the lower RPM ranges. And the only reason it had to, was that back then (end '80's, early 90's) noise level was also taken into account in international competition, to such an extent that no matter how good a pilot, a noisy plane would wreck all chances of ending high at the end of the day.

NOT saying that Hanno was a mediocre pilot that won thanks to his quiet engine, don't get me wrong... He simply was the best pilot out there at the time. But he simply did not take any chances having a good score ruined by a noise limit penalty.
Realistically, two identical planes, one with the Hanno Special and the other with a standard RF, performance-wise the RF would run circles around the HannoSpecial hands down, but the noise penalty would make it extremely difficult to win competitions with the RF.


Most people buy an engine, see the specs and think "great, my plane has XX horsepower installed", but it does not work that way. Not even close. Those are just numbers of what is theoretically possible. Not of what is practically availlable. What is practically availlable depends on the RPM the prop allows.
Nice bit of info on the Hanno & RF Thanks
Very true on the RPM/Prop Comment.

Old 07-23-2022, 02:07 PM
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Originally Posted by 1967brutus
Not sure what you mean by that, because those two ailleron servo's only serve to avoid long mechanical linkages. They are however both simultaneously controlled by the same ailleron stick, so they won't place ANY additional workload on the pilot, NOR make the plane more complicated to fly. Most people simply use a Y--harness to connect both servo's to a single RX output. Some use a separate output and connect both outputs in the TX programming.


There are very affordable "remote glow connections" that allow for a fuselage mounted socket connected to the glowplug. Very simple, and absolutely no issue.
Brutus is correct with the separate servo connection with or without Y-Leads. It's a better configuration and the plus side is being able to fine tune them using your TX program as opposed to a single fit aileron set-up.
All my models are configured this way or have been adapted (on older designed wings) to operate like this. You'll find the aileron throw/responce is much more 'crisp'.

Last edited by Eastflight; 07-23-2022 at 02:15 PM.
Old 07-23-2022, 03:49 PM
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Originally Posted by Eastflight
Brutus is correct with the separate servo connection with or without Y-Leads. It's a better configuration and the plus side is being able to fine tune them using your TX program as opposed to a single fit aileron set-up.
All my models are configured this way or have been adapted (on older designed wings) to operate like this. You'll find the aileron throw/responce is much more 'crisp'.
It is one of the most used methods nowdays.
With separate channels it also provides options like spoilerons or flaperons.


So.... YES, the two servo setup can provide added functions.



Last edited by Jesse Open; 07-24-2022 at 09:24 AM.
Old 07-23-2022, 04:43 PM
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Originally Posted by Eastflight
Brutus is correct with the separate servo connection with or without Y-Leads. It's a better configuration and the plus side is being able to fine tune them using your TX program as opposed to a single fit aileron set-up.
All my models are configured this way or have been adapted (on older designed wings) to operate like this. You'll find the aileron throw/responce is much more 'crisp'.
I still have one or two planes with a single servo set-up, and indeed, the difference is noticable. Even where an Y lead is being used, the reduced slop in the linkage and the fact that it is relatively easy to set u for differential throw (can be done with a single servo set-up too, but is a LOT more of a puzzle to get right) allready more than make up for the additional cost.
Old 07-23-2022, 04:46 PM
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Originally Posted by 1967brutus
You're welcome! That is what a forum is for...
It is wonderful to have you here posting such quality material Brutus. This site is lucky to have you here posting your immense knowledge and helping so many with it.
Old 07-23-2022, 05:53 PM
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At the price of today's servos, the return on the extra servo is a bargain.

The two servo setup is popular for so many reasons.

Last edited by Jesse Open; 07-23-2022 at 05:55 PM.
Old 07-23-2022, 10:25 PM
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Red face

Originally Posted by TheEdge
It is wonderful to have you here posting such quality material Brutus. This site is lucky to have you here posting your immense knowledge and helping so many with it.
You're making me blush....
Old 07-24-2022, 04:34 AM
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Originally Posted by 2W0EPI
Funny you should say but I have come across manufactures exaggerations quite routinely whilst comparing data between engines.But it's all relative, so I doubt the 46 will reach 16000 rpm as stated in the manufactures manual?

Exaggerations indeed!
Good entertainment, lucky to have them
Old 07-24-2022, 06:48 AM
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This one turned into a train wreck far earlier than I thought it would. I wonder if those that don’t know will actually listen to those that do and actually absorb the advice given.
Old 07-24-2022, 07:18 AM
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Originally Posted by 1QwkSport2.5r
This one turned into a train wreck far earlier than I thought it would. I wonder if those that don’t know will actually listen to those that do and actually absorb the advice given.
So far, the discussion has been very focused and remained very friendly. Not seen anyone trying to start something

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