Hello all.
I'm sorry if this is in the wrong place - I couldn't see a place for it to go.
Some friends and I are planning to design and build a multicopter from the ground up. We're heading down the route of full computer control, rather than R/C control - it's the nerdy software development side that interests us the most.
However, because I've built model planes and heli's before, I have been volenteered to build the quads themselves. I've been looking at the basics of the design - aerodynamics, different layouts, pro's/cons of different layouts etc and been reading a number of papers.
I have some questions that I'm hoping to bounce around if I can and get some responses from people who have already gone through the pain if possible?
1) Nacelles
A lot of the power of a jet comes from the Nacelle design - it proves about 40% additional air capacity. I haven't seen any aero nacelles around blades in most quads - although it would seem it would protect from damage a lot and also improve performance. Has someone looked at this and decided it's not worth it? Are there any papers about this?
<<edit - there are a number of quads with a nacelle design, but these seem to be used for either protection or just looks, as opposed to allowing the props to access a lot more air - i.e for performance reasons.>>
2) Ducted fans - has anyone ever looked at building multirotors with ducted fans, as opposed to regular props? If so, how did it turn out? Pros? Con's?
3) I have read a number of papers about all the benefits of building multi's with a single large prop right in the middle - like a helicoptor main prop - which takes around 90% of the AUW, which then allows the outlying motors to be for direction control. Benefits seem to be much improved aero, 15% better battery life, more agile, much easier to programme against. Downsides are dealing with torque.
Seeing as there seem to be so many benefits regarding this design it's the pattern I'm giving most thought to. However, I can't find anyone who has built this pattern in the real world..... But... I'm not sure what this pattern would be commonly known as either so not sure I am searching for the right keywords. Has anyone looked at these designs? built them? any feedback?
4) Purely from the point of view of programmability, has anyone looked at moving the arms of a multi, rather than changing motor speeds? I.e on a quad, where the arms are spread 90 degrees to each other, has anyone experimented with moving the arms themselves to induce pitch/yaw etc, rather than motor speeds? If so, how did it turn out? Was the extra weight and complexity worth the benefits?
5) Has anyone written any good papers or posted anything to this form about leg design for landing? I've not been able to find out much about them and, at least initially it seems easier to build flexible legs rather than write code to make a safe landing.
6) What are the reasons that motors point upwards on multi's, with puller props? Obviously needed if the multi doesn't have landing gear, but if they do, then having the motors point downwards would seem to make the dynamics of the multi a lot more easy to work with, and there should be a slight area advantage as the air is fully "clean" and not impinging on the motor spar.
7) When you have your multi pretty much built, and it comes time to balance it - i.e balancing the multi itself, rather than the props, which is done right up front, what is the most common method? Do you move the motors, use ballast or make small changes to the props? My guess is either motors or ballast is prefered, as the prop thrust is a dynamic, rather than a static, but not sure of what the usual approach is?
Many thanks indeed - and apologies in advance for asking a lot of really basic questions.
Many thanks
Steve
I'm sorry if this is in the wrong place - I couldn't see a place for it to go.
Some friends and I are planning to design and build a multicopter from the ground up. We're heading down the route of full computer control, rather than R/C control - it's the nerdy software development side that interests us the most.
However, because I've built model planes and heli's before, I have been volenteered to build the quads themselves. I've been looking at the basics of the design - aerodynamics, different layouts, pro's/cons of different layouts etc and been reading a number of papers.
I have some questions that I'm hoping to bounce around if I can and get some responses from people who have already gone through the pain if possible?
1) Nacelles
A lot of the power of a jet comes from the Nacelle design - it proves about 40% additional air capacity. I haven't seen any aero nacelles around blades in most quads - although it would seem it would protect from damage a lot and also improve performance. Has someone looked at this and decided it's not worth it? Are there any papers about this?
<<edit - there are a number of quads with a nacelle design, but these seem to be used for either protection or just looks, as opposed to allowing the props to access a lot more air - i.e for performance reasons.>>
2) Ducted fans - has anyone ever looked at building multirotors with ducted fans, as opposed to regular props? If so, how did it turn out? Pros? Con's?
3) I have read a number of papers about all the benefits of building multi's with a single large prop right in the middle - like a helicoptor main prop - which takes around 90% of the AUW, which then allows the outlying motors to be for direction control. Benefits seem to be much improved aero, 15% better battery life, more agile, much easier to programme against. Downsides are dealing with torque.
Seeing as there seem to be so many benefits regarding this design it's the pattern I'm giving most thought to. However, I can't find anyone who has built this pattern in the real world..... But... I'm not sure what this pattern would be commonly known as either so not sure I am searching for the right keywords. Has anyone looked at these designs? built them? any feedback?
4) Purely from the point of view of programmability, has anyone looked at moving the arms of a multi, rather than changing motor speeds? I.e on a quad, where the arms are spread 90 degrees to each other, has anyone experimented with moving the arms themselves to induce pitch/yaw etc, rather than motor speeds? If so, how did it turn out? Was the extra weight and complexity worth the benefits?
5) Has anyone written any good papers or posted anything to this form about leg design for landing? I've not been able to find out much about them and, at least initially it seems easier to build flexible legs rather than write code to make a safe landing.
6) What are the reasons that motors point upwards on multi's, with puller props? Obviously needed if the multi doesn't have landing gear, but if they do, then having the motors point downwards would seem to make the dynamics of the multi a lot more easy to work with, and there should be a slight area advantage as the air is fully "clean" and not impinging on the motor spar.
7) When you have your multi pretty much built, and it comes time to balance it - i.e balancing the multi itself, rather than the props, which is done right up front, what is the most common method? Do you move the motors, use ballast or make small changes to the props? My guess is either motors or ballast is prefered, as the prop thrust is a dynamic, rather than a static, but not sure of what the usual approach is?
Many thanks indeed - and apologies in advance for asking a lot of really basic questions.
Many thanks
Steve
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