BOEING / GoFly contest: Oh, BOEING
Posted 03 August 2018 - 05:44
Posted 03 August 2018 - 07:28
So you aren't going to bother with Phase 2 then?
Setting up a competition is actually more stressful than you might think, and the results of these design competitions are often rather sad. The X prize for cars succeeded in killing off a reasonably practical commercial proposition in favor of a car that was designed to win the comp but was not designed for production.
Posted 03 August 2018 - 13:56
Posted 03 August 2018 - 14:06
The opening specs are blatantly wrong. I'm sure all could achieve 200mph if they fail from high enough.
Posted 04 August 2018 - 03:15
Hello Greg Locock
“So you aren't going to bother with Phase 2 then?”
Quote from http://www.pattakon....GoFly_Forum.htm (it is from the Forum deleted by GoFly three days ago):
Hello Mokren. (9 July 2018)
To participate in the rest phases?
Only when BOEING will decide to take over and to turn this challenge to a decent and transparent one.
The credibility GoFly earned so far is for laugh.
They pretend their goal / vision is to foster thinkers and tinkers make people fly.
The 250 USD I paid them is nothing, but make me a sucker: that some guys, hiding behind a big name (BOEING), have deceived me is frustrating.
It is a shame for BOEING to continue as the big sponsor of GoFly.
To put it simply, what I purchased with my 250 USD is the following info:
“You are not in the ten winners of the Phase I. Period.”
Neither scoring, nor ranking, nor justification of the decision, nor a clue for the weak points the judges find in my solution, nothing at all.
Just that I am not in the ten winners of phase I. . .
And now they try to trap again the contestants with cheap “tricks” of the kind:
"Dear contestant, in order to get a REVIEW of your Phase I submission, you have first to register to phase II; and in order to register to phase II, you have, among others, to create a company, to pay insurance fee, to pay “team” fee and to give equity rights to GoFly.”
The trick / the cheating is double.
By “REVIEW” they do not mean the “fully justified resolution / verdict / decision of the judges”.
They just mean “a” review from “some” guy who is nominated as a “mentor”.
As you remember, they promised to give the scoring and ranking, and they never deliver.
Would you characterize the guy who thought the above “double trick” as a “decent guy whose vision is to foster people fly”, or as a scam?
End of Quote
Posted 04 August 2018 - 07:39
Oh don't worry, i agree, the situation stinks and I wouldn't have anything more to do with them.
Posted 06 August 2018 - 00:26
Develop your flyer. Get them manufactured in China. Sell them on E-Bay.
Edited by gruntguru, 06 August 2018 - 00:28.
Posted 08 August 2018 - 03:23
“Develop your flyer. Get them manufactured in China. Sell them on E-Bay”
Initially the GoFly (BOEING) contest appeared as an opportunity.
The final design (that with the two “coaxial” engines and the two-pairs of intermeshing propellers) was ready a couple of years before the contest.
In hindsight, the GoFly contest proved a deceit, a fraud, a hook with the “BOEING” (the big sponsor) used as the bait / the teaser.
With several internet forums writing about this fraud, BOEING cannot pretend, any longer, that they don’t know what is going on.
Edited by manolis, 08 August 2018 - 03:33.
Posted 08 August 2018 - 04:39
“Some support here for your concept of "torso control". The videos are interesting.”
Yes the videos are interesting (but two of them don’t “play”).
It seems that the intuitive control, used by birds, bats and bugs, is the best when a person is to fly, with the intuitive “torso control” being efficient and easily adapted.
Here is the JB11, the last JetPack of Mayman:
Quote from https://www.digitaltrends.com/cool-tech ... ion-jb-10/
“It’s like a Segway, Mayman explains.
If you want to go forward, you just lean forward.
If you want to stop, you just lean back.
It’s incredibly simple.
If you wanted to fly a helicopter, you’d need 150 hours of training — but with this, you can learn everything you need to know in about 3 hours.”
End of Quote
According Mayman’s experience on training “ordinary people” to fly with his JB10 JetPack,
some 3 hours of tethered tests / training is considered adequate before the initial low height free tests above water.
The pilot can fly at small height over the sea (or over a lake) for as long as it takes to get familiar and confident.
Only when the trained pilot feels ready, the pilot can take-off to the sky.
According Mayman, flying with his JB-10 is intuitive and easy: it is as easy and as intuitive as bicycling.
Here is Zapata’s FlyBoard-Air:
Zapata is not just flying, he is making acrobatics in the air.
And, as Mayman, similarly Zapata is based on the intuitive control.
Yves Rossy with his delta wing and his 4 jet-turbines goes a little further.
He uses his limbs and head for the control of his flight.
No electronics, at all.
Yves Rossy / Jetman "flies with the grace of an eagle, and the subtle body movements he uses to maintain flight - and perform his loops, rolls, and other maneuvers - mimics a bird of prey".
With only an altimeter and timer, Rossy uses his skin and ears as airspeed indicators.
"You feel very well, you feel the pressure," Rossy says, "you just have to wake up these senses. Inside an airplane we delegate that to instruments. So we are not awake with our body."
“I am the fuselage, and the steering controls are my hands, head and legs,” Rossy says.
Besides the “weight shifting CONTROL” (or “vectored thrust” control) of Zapata, of Mayman and of the GEN-H-4:
the PORTABLE FLYER has also the “aerodynamic CONTROL” of Yves Rossy.
In order to achieve “aerodynamic control” over his flight, Rossy needs to move at high speeds (say, above 100mph), otherwise his head and limbs cannot receive significant forces from the air.
In the PORTABLE FLYER the “Rossy like” aerodynamic control of the flight is applicable not only at high speeds, but at all speeds:
The heavy disk loading (thrust to disk area, similar to that of the OSPREY V22) causes a high downwash velocity, with the pilot inside it.
So, either at take off / landing, or at hovering, or at cruising, pilot’s limbs and head are in a high velocity air stream, which allows the aerodynamic control of Yves Rossi.
Posted 10 August 2018 - 10:28
Are we at the point where electric ducted fans could be used as an alternative to a parachute.
I could see someone jumping out of a plane or using a wingsuit and then rather than using a parachute they instead slow their descent using the fans until they can land.
Obviously would be tested at low height , maybe off a swimming pool high diving board, and then progress to landings over water from a greater height.
Not sure if there is any real use for it but it would look cool and be fun.
Posted 24 October 2018 - 13:29
Posted 27 October 2018 - 20:04
Is the little cutout on the top of the piston for the location of the spark plug in the sidewall?
Posted 28 October 2018 - 04:38
Yes, you are right.
Each piston has such a small cutout.
At the TDC (top dead center) the two opposed cutouts make room for the end-nose (say the last 5-6mm) of the spark plug.
In the next cylinder (to be made), the side location of the spark and the thin combustion chamber are changed (corrected) by using a narrowing at the center of the cylinder, like:
With the “narrowing”:
the spark goes near the center,
the combustion chamber gets meaty/thick/compact,
and a lot of squeeze is caused,
while the scavenging is not affected because the OPRE Tilting has “cross-uniflow” scavenging (“independent” in each half of the cylinder).
With the longer piston dwell at the combustion dead center, most of the combustion will complete in the narrowing (more “constant volume” combustion).
In comparison to a conventional single cylinder engine having an external balance shaft (to cancel out the –otherwise unbalanced - first order inertia forces) and a pair of synchronizing gearwheels, the OPRE Tilting appears simpler, is perfectly balanced, has substantially lower piston speed at the same rpm, etc.
With divided load (a propeller on each crankshaft, as in the Portable Flyer) the synchronizing gearwheels of the OPRE Tilting remain unloaded during operation and need not lubrication.
Without reed valves it is saved bulk, weight, cost, noise and problems (what is omitted cannot fail).
The tilting valve is reliable, adds no weight, adds no noise, makes easier the lubrication of the wrist pin, etc.
Tilting valves and gas control:
The tilting valves bring a different control over the gas flow of the 2-strokes.
The scavenging starts with a higher pressure just before the transfer ports (outside the cylinder).
At the beginning of the scavenging the fresh gas bursts into the cylinder (which enables an earlier opening of the transfer after to the opening of the exhaust).
The scavenging starts “positive”: from the opening of the transfer port to the BDC (Bottom Dead Center), the piston (with the tilting valve sealing its back end, and due to the small dead volume in the scavenge pump) displaces the air-fuel mixture into the cylinder positively (it resembles with the exhaust cycle of the 4-stroke engines: no matter what the pressure in the exhaust manifold is, the piston will push positively the burnt gas outside the cylinder).
Things change near the BDC wherein the tilting valve opens.
After the BDC the space inside the piston (i.e. the “crankcase” of the OPRE Tilting) is free to communicate with the cylinder through the open transfer port, and the scavenging turns from “positive” to “inertial”.
With the inertia of the fast moving gas “column” in the transfer - cylinder - exhaust, the transfer continuous strong till the closing of the transfer port, sucking gas from the space inside the piston.
At the end of the transfer, with the flow of the fresh gas from inside the piston towards the “scavenge pump” (and from the inlet port towards the space inside the piston) already strong, the filling (or overfilling) of the scavenge pump space with fresh gas continues uninterrupted till the closing of the tilting valve near the TDC. After the TDC the already established flow of fresh gas from the inlet port into the “crankcase” (i.e. the space inside the piston) continues uninterrupted, while at the same time the gas trapped into the scavenge pump undergoes a compression by the outwards moving piston.
The bigger the tilting valves, the better the breathing at high revs.
The over-square design enables bigger tilting valves to be used (look at the openings between the tilting valve and the back end of the piston):
In the prototype (opposed piston) there are two big tilting valves (one per piston), each serving 333/2=166cc of cylinder capacity.
The over-over-square design (84mm bore for 30mm piston stroke in the prototype) besides enabling big tilting valves, it is also enabling a “cross” (not loop) scavenging (you can call it “cross uniflow” and is normal to the cylinder axis) that prevents the mixing of the burnt gas with the fresh gas (say, similar to the through scavenging along the cylinder axis of the “long-stroke” Junkers Opposed Piston Air engines).
The tilting valve is actually an extension of the connecting rod small end.
With its “pulling-connecting-rod” design, the gas and the scavenging feels, around the BDC, as working into an engine running at, say, 30% higher revs:
which augments anything related with the inertia of the gas.
Timing / Asymmetry:
While geometrically the transfer and the exhaust are symmetrical, in practice the transfer appears strongly asymmetrical because it starts true positive (at the expense of some energy for the compression of the gas in the scavenge pump) and continues inertial after the BDC.
The intake is heavily asymmetrical (the inlet port is permanently open, the tilting valve makes the difference).
Edited by manolis, 28 October 2018 - 05:23.
Posted 16 April 2019 - 21:11
You machined the cooling fins rather than casting them to shape? I always found designing cast parts was (too) exciting.
Posted 16 April 2019 - 21:36
I think they are cast.
Congratulations Manolis - very impressive concept and execution.
Edited by gruntguru, 16 April 2019 - 21:37.
Posted 17 April 2019 - 02:44
Thank you Greg Locock and Gruntguru.
Everything in the three photos of my last post is cast (and only the piston with the piston rings on it, is machined after cast).
In this photo:
you can see the casing after the removal of the refractory material (plaster / silica) and before the removal of the "gating" system. The cooling fins are ready without any machining.
The casting is EPC (Evaporative Pattern Casting).
The material used for the two casings (the parts with the cooling fins) was taken from the casings of an old Nissan Micra 1,000cc engine and from an old Yamaha 250cc engine.
The material used for the pistons comes from melting several Smart engine pistons.
I would prefer to use LM25 (A356, AB42,000) aluminum alloy for the casings, but this material is not available in the local market.
By the way, if anybody knows, or can find, what type of aluminum alloy was used for Nissan MIcra and Yamaha casings, as well as for the Smart pistons, it would help in choosing the proper Heat Treatment (required to imrpove ductility and fatigue strength).
Edited by manolis, 17 April 2019 - 02:51.
Posted 17 April 2019 - 08:30
LM25 (or A356) is a very common heat treatable aluminum alloy used for sand castings. I can't imagine it is hard to find a source to buy a small quantity somewhere on the internet. Reasonable choice for a sand cast cylinder head or crankcase.
For cast aluminum pistons, a hyper-eutectic alloy (LM30 or A390) is often used. This type of high-silicon alloy requires a controlled die/permanent mold/investment casting process, which is only practical with large production applications. But the alloys do provide the excellent hot strength capability needed for recip engine pistons. Consider machining the pistons from a wrought forging alloy bar stock if possible.
Be careful about using production aluminum castings as your raw material. If they are permanent mold or die castings, they are possibly made from an aluminum alloy that will require a carefully controlled foundry process to obtain good metallurgy. If they are sand castings, the material can probably be re-used without any issues. You should be able to look at the parts and determine what casting process was used to make them.
The process for most heat-treatable aluminum alloys is to first give the castings a stress relief, then solution heat treat and aging (-T6 is common).
Posted 18 April 2019 - 04:18
The T6 is the case.
A problem is that the temperature and the time required for the solutionizing (before quenching) and for the aging are quite senstive to the alloy used.
But if you can't find the proper alloy locally, you have to compromize.