Rotors

[dandaman]

I'm just now startind this event, I'm also doing the robot am, with just me and my brother. I'm in a 3d design class, with access to a 3d printer, so I can get the pitch to be whatever I want (pending my teacher allows me to do it) my thought was to use balsa sheets, a team in our state did this last year and did really well. Then to glue the sheets onto the rotor supports. what would you guys suggest for a good pitch on the rotors?

[illusionist]

I'm just now startind this event, I'm also doing the robot am, with just me and my brother. I'm in a 3d design class, with access to a 3d printer, so I can get the pitch to be whatever I want (pending my teacher allows me to do it) my thought was to use balsa sheets, a team in our state did this last year and did really well. Then to glue the sheets onto the rotor supports. what would you guys suggest for a good pitch on the rotors?

Well, there is no 'perfect pitch' with helicopters (pun intended). It all depends on the chord length of your blades (how long from the leading edge to trailing edge) and the thickness/torque/winds of your rubber motor. You can try one pitch and then match your rubberband to it by altering the thickness of the rubberband. Basically to optimize flight times, you need to match pitch and rubber. Go back to last year's Helicopter thread. There's a lot of useful stuff in there.

[mrsteven]

I'm just now startind this event, I'm also doing the robot am, with just me and my brother. I'm in a 3d design class, with access to a 3d printer, so I can get the pitch to be whatever I want (pending my teacher allows me to do it) my thought was to use balsa sheets, a team in our state did this last year and did really well. Then to glue the sheets onto the rotor supports. what would you guys suggest for a good pitch on the rotors?

Well thats cool you have access to that (so do I ) but I fail to see how thatll help you in this event. If you intend to make a jig of sorts with the ABS plastic I think youll find that there are much easier methods without designing on autocad/inventor.

Ditto with illusionist.

Additionally, from what I gather, you're making the blades out of a flat piece of balsa wood? there are better designs that yield much better times by making them curve. flat blades have enormous drag. (also really heavy) look at some of the parlor copters of last year or on google. thats essentially the basic design of helicopters most teams will produce that dont go for the multiplier

[jazzy090]

I recently realized that I forgot to balance my lower rotor before mounting it on the drive stick . I was able to balance it last year when it was fresh off the jig and still had the entire upper and lower spar connected with a small pin, but that was prior to mounting it and cutting the spars to fit the design. Does anyone know how to balance the lower rotor/if this is even possible at this point (fully constructed)?

[illusionist]

Additionally, from what I gather, you're making the blades out of a flat piece of balsa wood? there are better designs that yield much better times by making them curve. flat blades have enormous drag. (also really heavy) look at some of the parlor copters of last year or on google. thats essentially the basic design of helicopters most teams will produce that dont go for the multiplier

That's not necessarily true. They may weigh more (depends on your construction ability), but they should have similar, if not less, drag than the typical rib-and-covering design. If you cut them out in a nice curved shape, then you basically eliminate the drag that comes from the 90-degree corners of the standard rib-and-covering type.

[illusionist]

I recently realized that I forgot to balance my lower rotor before mounting it on the drive stick . I was able to balance it last year when it was fresh off the jig and still had the entire upper and lower spar connected with a small pin, but that was prior to mounting it and cutting the spars to fit the design. Does anyone know how to balance the lower rotor/if this is even possible at this point (fully constructed)?

It might be possible depending on how centered you mounted it to your motorstick. Either way, I think it'd be worth it to try to balance even now after you've mounted to the motorstick. But it's not possible to balance just the rotor.

[dandaman]

I'm just now startind this event, I'm also doing the robot am, with just me and my brother. I'm in a 3d design class, with access to a 3d printer, so I can get the pitch to be whatever I want (pending my teacher allows me to do it) my thought was to use balsa sheets, a team in our state did this last year and did really well. Then to glue the sheets onto the rotor supports. what would you guys suggest for a good pitch on the rotors?

Well thats cool you have access to that (so do I ) but I fail to see how thatll help you in this event. If you intend to make a jig of sorts with the ABS plastic I think youll find that there are much easier methods without designing on autocad/inventor.

Ditto with illusionist.

Additionally, from what I gather, you're making the blades out of a flat piece of balsa wood? there are better designs that yield much better times by making them curve. flat blades have enormous drag. (also really heavy) look at some of the parlor copters of last year or on google. thats essentially the basic design of helicopters most teams will produce that dont go for the multiplier

I was planing on setting angle and and such to be printed, then to attach, probably with glue, the balsa pieces to them. I was planning on curing the ends of the blade and end up a eliptical shape. This way I could get a conmsitent angle and perfectly centered holem, they would still need balancing tho.

[34taji]

Hey, i've seen some curved rotors instead of flat and i was wondering how to do that. Does anyone have any idea on how to do this?

[thsom]

If I were to follow the design on sciencenc.com: http://www.sciencenc.com/event-help/helicopters.php would it be beneficial to use curved rotors or would that just increase drag without significantly increasing power or propelling force. I know that curved rotors are effective in other designs, but I am not sure about in this design.

[jander14indoor]

That's a VERY basic design. It works, not very efficient. The rotors aren't helical in pitch so it's really only right at one radius. Everywhere else the angle of attack is to high or low.

First step to improve it is to modify so its helical. Then try curved ribs.

Jeff Anderson
Livonia, MI