- #36
Cyrus
- 3,238
- 16
Brian_C said:The torque required to spin the conveyor belt will generate a pitching moment, which would have to be corrected.
Hah, you're right. The question is how much.
Brian_C said:The torque required to spin the conveyor belt will generate a pitching moment, which would have to be corrected.
MotoH said:It seems to me that the lift to weight ratio would be very low, as all of these equipment to make the belt spin will have more effect on the aircraft than the lift generated.
or is this just proof of concept?
WCOLtd said:Pitching moment? Of all the trivial concerns that takes the cake.
The belt is made out of metallic wrapping paper for goodness sakes! Even at 120 mph tangential speed how much of a moment could that possibly create?
Pitch would only be effected while the belt is accelerated or decelerated! Pitch is the only axis which is unaffected by rotation of the belt and pipe. My concerns are the gyroscopic forces, yaw and roll and I don't anticipate that to be such a problem - but I could be wrong - I haven't done the calculations.
The wrapping paper and roller is super light, I don't see why a 1 inch pipe rotating at 15,000 rpm will generate that much of a pitching moment, especially when you consider that on a real plane, it will be accelerated as the relative windspeed increases. There is no way in the world that the pitching moment would be anything in comparison to the anti pitching resisting forces of the wing and tail wing.
Also magnus sail boats don't steer through the magnus effect, they steer through the rudder like all boats. And the boats do move through the water, even when a small sailboat is filled with 3 people! also the tangential speeds on those sailboats are 25 mph maximum with the wind, my belt will have relative speeds anywhere from 50 mph - 120 mph! The amount of force needed to lift a remote control airplane vs the amount of force to move a sailboat with 3 people is dramatically less.
On top of that, the belt is in the shape similar to a NACA 4 series airfoil, the geometry of the belt itself will generate part of the lift, I am not going for creating lift via the magnus effect. Unlike a back-spinning ball I am mainly focused on reducing the viscous forces over the top of the wing - maybe it won't produce all that much lift, I don't know, but as far as I know, my design has never been tried.
The design is not perfect, I will have a bunch of challenges making the thing work, but I am pretty sure it's going to fly.
If the design is successful anyway, scaling up to reduce the weight will not be terribly difficult - carbon fiber rollers ceramic bearings, and some yet-to-be-discovered-by-me suitable belt likely already inside a DuPont catalog will all add up to reduced weight. Of course I'll cross that bridge if and when I get there.
that's analogous to saying "I'll cross that bridge if and when I get there" which basically means "lets not get ahead of ourselves - let's worry about that if we ever will need to."...let's not put the cart before the horse
WCOLtd said:I wrote it in the same erroneous way so that he could better understand it. I think you understand what I mean though, it won't have any effect on the aircraft's ability to pitch up and down. You said it yourself better than I did. Except I disagree when you inferred that there might be some legitimacy in the concern, it's really trivial.
WCOLtd said:To me, this just seems so absurd, the main propeller engine on the front will be producing far more torque than the rotors along the belt. According to this way of thinking I should be far more concerned with the plane doing perpetual barrel rolls through the air than I should be concerned with pitching.
WCOLtd said:The biggest problem I could think of with this design was how I was going to center the rotor to the roller pipe - I figured that in order to prevent a wobbling I would need to somehow perfectly bind the rotor into the exact center of the roller pipe. However I think I have come up with a solution to that problem of rotational stability. It will be achieved by making a special mold for the 1 inch outer diameter bearing. The propeller engine will be behind a wall, with a hole drilled in it. The rotor poll will stick out of the fusalage or will be partially encased in the pipe itself, and the bearing will fit around the rotor, it will have a mold on it to attach the inside bore of the bearing to fusalage, and the outer bearing will be attached to the inside of the pipe - along with the rotor. Looking into the rotor, the mold will have to look something like one of those depictions of space-time curvature around a black whole.
The issue will be whether or not I will be able to get a bearing to fit inside the pipe and 2) whether or not I will be able to strongly bond the rotor to the wing pipe.
A third problem will be the whether or not the prop engine will be able to handle the increased torque of the pipe.
Well, there's a lot to be said for his putting his money where his mouth is...Cyrus said:My point is that you need to stop "this way of thinking", and dig into a textbook on flight dynamics because a lot of what one may think and what really happens is counter-intuitive.
He is resetting context. Simply saying "engine" in the context of a discussion about wings might be confusing. Nitpicky at best, cheap shot at worst.Cyrus said:Also, a course correction: what is a "propeller engine"? There is a propeller and an engine, not a propeller engine.
DaveC426913 said:Devil's Advocate:
Well, there's a lot to be said for his putting his money where his mouth is...
What is wrong with him building his prototype? So he learns some things along the way. Far better that he follow it through than that we discourage him and he drops it.
He is resetting context. Simply saying "engine" in the context of a discussion about wings might be confusing. Nitpicky at best, cheap shot at worst.
Cyrus said:I am simply correcting him Dave, relax.
Would you prefer that he goes on using incorrect terminology?...
DaveC426913 said:I don't agree that he is using incorrect terminology.
If you can have a jet engine and a steam engine, you can have a prop engine.
Appeal to authority. That does not make him wrong. Or me.Cyrus said:Find me an aerospace book that uses that term and I will concede to you.
Cyrus said:The angular momentum of the propeller lies along the longitudinal axis of the aircraft, the rollers are on the lateral axis. Why do you think these two are directly comparable?
Cyrus said:My point is that you need to stop "this way of thinking", and dig into a textbook on flight dynamics because a lot of what one may think and what really happens is counter-intuitive.
Also, a course correction: what is a "propeller engine"? There is a propeller and an engine, not a propeller engine.
WCOLtd said:I thought that critique might come up, the reason I think It's not a problem is because;
1) the fact that the engine powering the belt is far less powerful than the main engine - I don't know exactly how much less because they don't keep track of the torque of the RC propeller rotors as far as I know.
2) Using mathematics it is indeed possible to relate the two axis to one another. Using just intuition - the forces normal to the longitudinal axis of the aircraft is equal to 4pi times the integral of the resistance across the surface area over the upper surface from the fusalage to the tip of the wing. (To calculate the resistance forces I assume I will need a more complete understanding of fluid dynamics)
Ok. you know more than I do - I'll concede that - so name a book and I'll buy it and I'll read it.
A propeller engine is an engine that powers a propeller.