Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by jthunt, Mar 17, 2012.
We're doing the our best and hoping that will payoff.
-back in Volgograd...
Way to go Malish!
You are famous!
I was thinking about motorcycle drive belts earlier and thought maybe it might be useful for a future PJ III or PJ-IIB
Driving each blade with 2-3 belts from the rear would GREATLY simplify design and may increase performance.
It would allow the drive system to be a single shaft to the rear without gears or bends. The belts would then pass through the wall BEHIND the blades and connect to a gear on the REAR of the blades instead of front.
This would allow the system to be very simple, but also allow more clean airflow to the blade and reduce obstruction to intake, which is far more disruptive than minor disruption to exhaust. It would also allow FAR easier inspection of the gearing system, and allow modification of fan gear ratios simply by replacing the sprocket on the drive shaft.
Just a thought for future designs.
What do you think, what will last longer - metal drive shaft or flexible belt turning fan at 7000 rpm? What is about extreme airflow will do to the belt in air duct?
Look what strong NE wind did to a new metal bridge over Volga river in Volgograd a few years ago.
Looks like we've returned to the Wright Flyer
It's the Tacoma Narrows bridge all over again!
I understand your concern, but with a cowling over the belts that shouldn’t be a problem.
Remember how many of our members have had gear failures on PSRUs. They are VERY prone to failure.
The belts are actually used on very reliable motorcycles FAR in excess of 7000rpms. That should not be a problem at all. They are very reliable.
It also makes maintenance much easier and less expensive as the belts can simply be replaced every 1000 hours or so, and are also easily inspected.
I see your Russian bridge and raise you an American bridge:
Following the collapse of the Tacoma bridge, work on long suspension bridges around the world stalled for some years. Until engineers working on a truss bridge (a suspension bridge would have been too long) over the river Severn in the UK found they had some left over wind tunnel time. So, they had a play with ideas for suspension bridge structural and aero fixes. It worked, they stabilised the model at a previously unheard of span. The design for the Severn bridge was subsequently changed to a suspension bridge, at a great cost saving over the original. Sadly, some genius decided to save a few more pennies by reducing the size of the end bearings. That resulted in greatly increased long term maintenance costs.
The Severn bridge still stands though it has been supplanted by a cable stayed bridge. To drive over it, take the M48 to Chepstow. It has a great view, unlike the new bridge with its wind barriers.
Back on topic. If Malish as a working redrive, he's going to be very tempted to stick with it. I would. While they look simple, redrives are not simple to engineer. Both belts and gears can have issues and break, if the whole system is not well designed.
Am I the only one trying to guess which one of the people in the news report was Malish?
I guess it's not the cute brunette, but happy to be proved wrong!
I'm one with gray hair talking with cute blond hair reporter next to aircraft.
I'm rely appreciate your advice's, but what is my concerns:
Cowling over belts should be very strong and heavy and it's will create some disturbens to airflow too.
The distance between engine and the fan's about 5', so it will require some drive shaft and support housing for pulley which will hold 4 to 6 driving belts.
I'm still not sure that belts will be able to hold 7000 rpms at 200 hp per side.
Malish - ignoring reliability questions and the possible need to redesign the gearbox etc, have you done any calculation as to what sort of performance you would get from the Dreamer if you had 800 shp?
-probably hybrid system ?
(iff yes=two electric motors in conter rotating arrangemant + ejection duses,
in place of Nastia cat...)
I have been following this thread for a long while, and I think Malish should implement all the suggestions in this thread.
Who needs a working aircraft undergoing final flight trials anyway, when you could have an electric turbine belt-driven 800 hp model. Perhaps make it a canard too.
You forgot roadable part 103
VTOL or STOL?
First: All belt manufacturers try whatever they can to keep their products out of aircraft.
The best belt on the market at the moment is the GT3. It has superior power capability and in addition higher lifetime, still it is limited to where it can be used.
Belts are categorized in pitch, meaning the length between two teeth, and width. The 8mm pitch is limited to 5500rpm and the 14mm is limited to 4000rpm (on the smaller gear!). In terms of power, the 8mm would only handle 200hp at maximum width, so it would be wise to use the 14mm in the first place.
The values can be exceeded for short time (if other parameters allow it), but at this deviation I don't see how you could put this in your aircraft (at least not for the 2x200hp version).
BTW I wasn't suggesting that Malish go to an 800 hp motor, but rather was interested in his thoughts on what (if any) benefit could be gained by combining his design with a much larger motor - curious to know whether more hp would benefit given that they are relatively small fans (look to be about 24 inches in diameter).
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