Author Topic: This is the future. (Read 1800 times)

Lauri Malila · « **on:** May 12, 2020, 12:55:22 PM »

The best of both technologies? 🤔

Jim Carter · « **Reply #1 on:** May 12, 2020, 04:30:10 PM »

WOW!! that is truly a marvel to behold! Any idea what the performance specs are like? I assume this is a specialty one-of-a-kind isn't it versus something for the mass market. It must be incredible to hear it running!!

Brett Buck · « **Reply #2 on:** May 12, 2020, 09:03:49 PM »

Quote from: Lauri Malila on May 12, 2020, 12:55:22 PM

The best of both technologies? 🤔

Make it with 2 Fox 35s, and I am on board.

It's hard to keep even one ST46 running properly, getting two of them to do it at the same time is not a task I would want to undertake.

Brett

Massimo Rimoldi · « **Reply #3 on:** May 13, 2020, 01:13:54 AM »

Quote from: Brett Buck on May 12, 2020, 09:03:49 PM

Make it with 2 Fox 35s, and I am on board.

It's hard to keep even one ST46 running properly, getting two of them to do it at the same time is not a task I would want to undertake.

Brett

The engines are two G21/29, the system was not dedicated to the stunt.
The construction dates back to 1967 and was designed to power the reproduction of a Macchi MC 72.
The manufacturer is Italo Magrotti who, among other things, is the father of the Kosmic K.15 engine.

Massimo

Fredvon4 · « **Reply #4 on:** May 13, 2020, 09:09:40 AM »

Just because you CAN do a thing does not mean you SHOULD...except for specific Scale representation of some unique design

HP to weight ratio.....there are literally hundreds of other multi or single engines-- gas-- glow-- or diesel that have significantly higher power to weight ratios

Jim Carter · « **Reply #5 on:** May 13, 2020, 09:52:28 AM »

Quote from: Massimo Rimoldi on May 13, 2020, 01:13:54 AM

The engines are two G21/29, the system was not dedicated to the stunt.
The construction dates back to 1967 and was designed to power the reproduction of a Macchi MC 72.
The manufacturer is Italo Magrotti who, among other things, is the father of the Kosmic K.15 engine.

Massimo

Massimo, Lauri, Personally, I want to thank you for sharing these kinds of finds. I had no idea they even existed and whether they are practical or not and whether they should or should not be made ... to me, is absolutely irrelevant!! Personally, I am amazed and in awe of folks gifted with such imaginations and the skills to create such works of engineering and art. Again, thanks for sharing!

Tim Wescott · « **Reply #6 on:** May 13, 2020, 09:54:33 AM »

I showed this to my kid and he asked "why not one engine driving a gearbox?".

Jim Carter · « **Reply #7 on:** May 13, 2020, 10:09:20 AM »

Quote from: Tim Wescott on May 13, 2020, 09:54:33 AM

I showed this to my kid and he asked "why not one engine driving a gearbox?".

Hi Tim! Now please know that I'm not an engineer, by no means. But from the looks of the design, these engines are driving counter rotating props and the gearbox allows the engines to sync in rpm, somehow. The article states that the two engines are not connected and must be started individually. Than could be a real challenge!! From the size of the propellers (14"), I'm not sure a single engine would swing both of them and still be able to provide any usable horsepower for flight speeds. Now I recognize I could well be wrong but my thoughts take into consideration what I've read about the engine technology of that period versus the greater efficiencies obtainable today. Jus' sayin' without knowin'!! $:-\$ $:-\$

Tim Wescott · « **Reply #8 on:** May 13, 2020, 10:30:06 AM »

OK. Point. So, at the time there weren't any .90 engines available, at least from the big names in model aviation. (Assuming that .46 + .46 = .90).

Certainly I recall that for a while in the 1980's (late '70's?) Hanno Prettner was winning RC aerobatics shows with a plane that had two .60's geared to one prop. It's probably no coincidence that about one development cycle later a bunch of engine manufacturers had 1.20 and .90 engines available.

Brett Buck · « **Reply #9 on:** May 13, 2020, 10:33:55 AM »

Quote from: Jim Carter on May 13, 2020, 09:52:28 AM

Massimo, Lauri, Personally, I want to thank you for sharing these kinds of finds. I had no idea they even existed and whether they are practical or not and whether they should or should not be made ... to me, is absolutely irrelevant!! Personally, I am amazed and in awe of folks gifted with such imaginations and the skills to create such works of engineering and art. Again, thanks for sharing!

There are tons of similar sorts of projects. If you can think of it, someone, somewhere, has probably already done it - modelers, as a group, can do almost anything you can think up. Most of them are one-offs, but that doesn't make them less wondrous.

Brett

Massimo Rimoldi · « **Reply #10 on:** May 13, 2020, 10:57:15 AM »

Quote from: Tim Wescott on May 13, 2020, 10:30:06 AM

OK. Point. So, at the time there weren't any .90 engines available, at least from the big names in model aviation. (Assuming that .46 + .46 = .90).

Certainly I recall that for a while in the 1980's (late '70's?) Hanno Prettner was winning RC aerobatics shows with a plane that had two .60's geared to one prop. It's probably no coincidence that about one development cycle later a bunch of engine manufacturers had 1.20 and .90 engines available.

This realization was not intended for the F3A competition but it was a one-off realization with a specific purpose, to motorize a reproduction.
There were many original solutions for these purposes, I think the AERO .35 made in the USA and its Soviet counterparts were born for this reason.
In this case some advantages could be exploited:
- Small front size
- Possibility to operate (really) two counter-rotating propellers
On the other hand, the difficulties encountered for the construction and the limits of the system are evident, one for all the engines was started manually (first the front one and then the rear one)
As I believe Brett means, I am convinced that the realization should be understood as an exercise in "mechanical art" applied to modeling.

Massimo

Brett Buck · « **Reply #11 on:** May 13, 2020, 11:16:39 AM »

Quote from: Massimo Rimoldi on May 13, 2020, 10:57:15 AM

As I believe Brett means, I am convinced that the realization should be understood as an exercise in "mechanical art" applied to modeling.

Stuff like this makes modelers a fascinating bunch to be around.

Brett

Lauri Malila · « **Reply #12 on:** May 13, 2020, 12:39:44 PM »

At least it’s an acceptable way to use a double amount of head shims.
But semi-seriously, it would be interesting to think and do it really well, from scratch. L

dennis lipsett · « **Reply #13 on:** May 13, 2020, 01:42:42 PM »

Quote from: Massimo Rimoldi on May 13, 2020, 10:57:15 AM

This realization was not intended for the F3A competition but it was a one-off realization with a specific purpose, to motorize a reproduction.
There were many original solutions for these purposes, I think the AERO .35 made in the USA and its Soviet counterparts were born for this reason.
In this case some advantages could be exploited:
- Small front size
- Possibility to operate (really) two counter-rotating propellers
On the other hand, the difficulties encountered for the construction and the limits of the system are evident, one for all the engines was started manually (first the rear one and then the front one)
As I believe Brett means, I am convinced that the realization should be understood as an exercise in "mechanical art" applied to modeling.

Massimo

I believe that Webra made a geared twin based on
Hanno Pretners design it was a 120 IE 2 60's

Massimo Rimoldi · « **Reply #14 on:** May 13, 2020, 02:50:36 PM »

Quote from: dennis lipsett on May 13, 2020, 01:42:42 PM

I believe that Webra made a geared twin based on
Hanno Pretners design it was a 120 IE 2 60's

I'm sorry but I don't think the comparison holds up. A lot of painters have made a large amount of works but few can be compared to the Monna Lisa.

Massimo

Brett Buck · « **Reply #15 on:** May 14, 2020, 10:30:58 AM »

Quote from: Massimo Rimoldi on May 13, 2020, 02:50:36 PM

I'm sorry but I don't think the comparison holds up. A lot of painters have made a large amount of works but few can be compared to the Monna Lisa.

That seems like a bit of a stretch in this case. But it's pretty neat.

Brett

jerry v · « **Reply #16 on:** May 14, 2020, 12:01:26 PM »

This is the future... Who knows. Positive features of this counterrotating design are slower rpm because gear ratio is something like 1 : 1.5 or 1 : 1.75 by the picture. Bigger prop can be used more efficiently. And bigger torque of each prop is compensated by counterrotating. Each engine runs independently, making setup easier.
Negative side of this design is extra weight and difficulty of starting.
Dave Lockhart is successfully flying RC pattern with electric setup- one motor and planetary gearbox with counterrotating props. It sounds unusual in flight. But there is no torque, just equal trust from each prop.
Counterrotating coaxial or twin setup as usual is proven to fly normal and inverted pattern more accurate in control line. It’s just more complicated to make.

Jerry V

FLOYD CARTER · « **Reply #17 on:** May 14, 2020, 12:17:55 PM »

Model plane success has always depended on a workable power to weight ratio. Unless any unconventional propulsion system can exceed the p/w of our present glo or e-power, it is just an exercise in the laboratory.

The real future is in e-power. We are getting there slowly, but battery development is the pacing factor.

Massimo Rimoldi · « **Reply #18 on:** May 14, 2020, 12:33:09 PM »

Quote from: Brett Buck on May 14, 2020, 10:30:58 AM

That seems like a bit of a stretch in this case. But it's pretty neat.

Brett

I certainly did not want to compare the propulsion system with Leonardo's masterpiece, only to underline the difference between a standard industrial product and something unique that stands out against the others. Here in Italy it is said that "he is out of the choir".

Massimo

Brian Hampton · « **Reply #19 on:** May 14, 2020, 07:50:40 PM »

I think what's being overlooked here in the design of this engine is its intended use which was for F4B control line scale. Under FAI rules the maximum engine size is 10cc hence the two ST 29's. The full size plane used two counter rotating props. It would have been possible to have one of the props just windmill in the breeze of a driven prop but by having two contra rotating driven props then the static scores would have been much higher due to the ingenuity of making it follow full scale practise. In world championship events particularly, every extra point matters.

The use of the 1.5:1 gearbox would allow the ST's to run at ~15,000 revs (pretty much peak HP) while the 14" props would run at ~10,000 revs.

GERALD WIMMER · « **Reply #20 on:** May 15, 2020, 06:27:13 AM »

Hello
Now the effective engine size limit for F4B is 250cc a rework with much larger engines is possible but the 7kg limit is the real engine size limiter now.
Personally a Saito multi 3 cylinder is about as flash as I could ever hope for

Regards Gerald

NB the FAI should really change the F4B rules to allow for 2.4ghz throttle control as the rules allow it to start and stop an electric motor and look at the new electric speed class where motor control can be outside the circle by another person other then the pilot

Brett Buck · « **Reply #21 on:** May 15, 2020, 05:49:41 PM »

Quote from: GERALD WIMMER on May 15, 2020, 06:27:13 AM

Hello
Now the effective engine size limit for F4B is 250cc a rework with much larger engines is possible but the 7kg limit is the real engine size limiter now.

That limit, at one point, was going to be across the board, which means it was going to be 250cc for stunt, too. There was a minor flap about it on SSW, wherein there was concerned expressed at how dangerous that might be, and how everyone would be at a severe competitive disadvantage if they didn't get giant engines.

All it really means is that you have no limit, a lot of ST60 airplanes were FAR too large to be competitive, as long as you limited it to 70' lines. No one has yet (or is likely to) suggest allowing more than 70' lines - that really would change something.

But no one is going to be flying 250cc control line airplanes, now, or in the future. From my motorcycle days, we are talking something up to 85-90 hp!

Brett

Steve Fitton · « **Reply #22 on:** June 05, 2020, 11:04:33 AM »

Quote from: Brett Buck on May 15, 2020, 05:49:41 PM

But no one is going to be flying 250cc control line airplanes, now, or in the future. From my motorcycle days, we are talking something up to 85-90 hp!

Brett

Banjock would try it....

Olli-Matti · « **Reply #23 on:** June 05, 2020, 12:20:34 PM »

Man I was afraid that there would be a picture of an electric motor in the first post when I first saw this topic, but phew