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Old Jul 11, 2011, 07:50 AM
13brv3's Avatar
Navarre, FL
Joined Mar 2002
3,827 Posts
Morning all. I'll try to make this a group reply to keep from running up my post count too high

Pug398,

I haven't received many requests for 1/2" round blocks, so I'm afraid they're not really on the to-do list right now. If it were as simple as plugging 1/2" into the program, I'd make some for you, but finding the best size becomes a trial and error procedure, which it fairly time consuming. Once I get close, I have to make a bunch of blocks a few thousandths different in size to see which works best on average.

Daign,

Thanks for finding all those pictures. Enjoy the Rev-8 kit.

Larry,

Glad to hear the old frame is still flying. Someone told me about losing one on a mountain, then getting a call a few months later from someone who found. He said the frame looked just like it did when he lost it.

Which picture were you asking about for the GoPro mount and legs? I see a couple with GoPros, and both have my CM-1 gear legs. The one on the gray table is mine, and just has a simple GoPro tripod mount attached to the bottom of the CM-1. The other pictures are customer frames, and it looks like they made their own plate.

Koolkiwikat,

You may have been the one who sent me a link to someone with blocks that allow the tubing to snap in place? It was neat, and still a possibility some day. I'll be doing a lot more thinking about folding options in the near future.

Jim,

As always, thanks for all the copter documentation!

Cheers,
Rusty
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Old Jul 11, 2011, 08:44 AM
It wasn't me
r0sewhite's Avatar
Augsburg, Germany
Joined Mar 2010
428 Posts
Quote:
Originally Posted by Morphin View Post
Hi Rusty

I have seen another nice frame:
http://www.microcopters.de/artikel/d...ite-sport-quad

Can you also build like this one?


Andy
Quote:
Originally Posted by Joecnc2006 View Post
I got away from the Flat arm designs, imo that is the weak part of that style of quad without some thick carbon fiber.
My ambition was to create a frame that is almost unbreakable. I like to fly wild and accidents are common. Though this frame is not unbreakable as I already found out, it's much more solid than a normal frame with aluminium arms.

I was able once to break one of the arms by hitting the ground with full speed. I'm still sure it was a bad accident because I've had a lot of similar crashes where nothing happened. Probably I hit a stone on the ground.

The disadvantage of this frame is the aerodynamic drag. There is a noticeable difference between these two frames:





However, I prefer this quad for trying new aerobatics because usually a hard crash only means to mount new props. At 10:08 you can see a typical crash that only cost me one prop:

Flugtag r0sewhite und x4FF3 (10 min 44 sec)


Another disadvantage is the price. I used 3mm CFK for the arms and that's the minimum thickness you need for a 20cm arm. Unfortunately high quality CFK is not cheap. A plate for 4 arms cost me about 50 Euro.
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Old Jul 11, 2011, 09:23 AM
Z06 Tony's Avatar
Rochester NY
Joined Sep 2008
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Quote:
Originally Posted by r0sewhite View Post
My ambition was to create a frame that is almost unbreakable. I like to fly wild and accidents are common. Though this frame is not unbreakable as I already found out, it's much more solid than a normal frame with aluminium arms.

I was able once to break one of the arms by hitting the ground with full speed. I'm still sure it was a bad accident because I've had a lot of similar crashes where nothing happened. Probably I hit a stone on the ground.

The disadvantage of this frame is the aerodynamic drag. There is a noticeable difference between these two frames:





However, I prefer this quad for trying new aerobatics because usually a hard crash only means to mount new props. At 10:08 you can see a typical crash that only cost me one prop:

http://www.youtube.com/watch?v=msZwcLUc71I

Another disadvantage is the price. I used 3mm CFK for the arms and that's the minimum thickness you need for a 20cm arm. Unfortunately high quality CFK is not cheap. A plate for 4 arms cost me about 50 Euro.

Why would the top frame have more aerodynamic drag than the bottom frame?
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Old Jul 11, 2011, 09:38 AM
It wasn't me
r0sewhite's Avatar
Augsburg, Germany
Joined Mar 2010
428 Posts
Because the frame is not horizontal while flying (except if you hover). The top side is forward-facing when you're flying. Since the shape of the frame drags it back to a horizontal position in fast forward flight, I need to pitch a little more. The aerodynamic drag is especially noticeable in fast flights, lifts and tight loops.
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Old Jul 11, 2011, 09:42 AM
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United States, CA, Los Angeles
Joined Feb 2011
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Guys I'll be using the DT700s or KDA 20-22L, is it worth playing with a 4s battery or two for extended flight time or should I play with a hexa config.
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Old Jul 11, 2011, 10:28 AM
13brv3's Avatar
Navarre, FL
Joined Mar 2002
3,827 Posts
Quote:
Originally Posted by r0sewhite View Post
Because the frame is not horizontal while flying (except if you hover). The top side is forward-facing when you're flying. Since the shape of the frame drags it back to a horizontal position in fast forward flight, I need to pitch a little more. The aerodynamic drag is especially noticeable in fast flights, lifts and tight loops.
Completely logical reasoning for using the sturdy CF frame. It sure does look tough.

Drag is one of the reasons I don't like flat arms, and there's a small loss of thrust as well due to the propwash being partially blocked.

Another reason is that it will transmit more vibration from the prop pulses that hit it. The same (probably worse) goes for all the built-up arm designs that are out there as well.

I've always thought an airfoil shaped arms would be best, but they aren't readily available, and I'm sure not planning to make them out of fiberglass or CF.

Cheers,
Rusty
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Old Jul 11, 2011, 10:52 AM
It wasn't me
r0sewhite's Avatar
Augsburg, Germany
Joined Mar 2010
428 Posts
Hi Rusty,

vibrations are less at the center plates, not more. The cf arms are a little flexible but I have built a tricopter and this quad from cf and in both cases I noticed that the flexibility of the cf absorb vibrations.

I just plan a quad frame with/for warthox which will have cf tube arms. We hope to get a frame with least drag which is still solid. I have had a few crashes with my tricopter and though the arms are quite long, I never had any damage.

The only problem is that if I use T-Rex 450 tail boom holders like on my tricopter again, the center plates have to be very strong. That means, I can't shape big holes into the center plates to reduce drag.



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Old Jul 11, 2011, 11:53 AM
13brv3's Avatar
Navarre, FL
Joined Mar 2002
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Originally Posted by r0sewhite View Post
Hi Rusty,

vibrations are less at the center plates, not more. The cf arms are a little flexible but I have built a tricopter and this quad from cf and in both cases I noticed that the flexibility of the cf absorb vibrations.
Vibration is a very complex subject, and any change makes a difference. I tell people "everything changes everything".

One thing that's certain is that reducing the vibration at the source is always good. That means balancing props and motors which is obvious, but it also means using a relatively streamlined material for the arms, so you don't transmit large pulses to the arms from the props. A round tube isn't the greatest aerodynamic shape, but it's better than square, or flat.

BTW, where's the yaw mechanism on that tri-copter? Funny thing is that I've never made a tri-copter in all the years I've been flying these things. For me, having a mechanical yaw control just spoils the whole multi-rotor concept.

Cheers,
Rusty
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Old Jul 11, 2011, 11:58 AM
13brv3's Avatar
Navarre, FL
Joined Mar 2002
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Quote:
Originally Posted by daign View Post
Guys I'll be using the DT700s or KDA 20-22L, is it worth playing with a 4s battery or two for extended flight time or should I play with a hexa config.
I'm afraid you'll almost certainly have to determine the most efficient combination by experimentation. I'd recommend a reliable watt meter, like maybe the EagleTree logger.

Unfortunately, everything is a compromise, so if you find a configuration that gives really good flight time, it may not be the best flying configuration. Most likely you'll choose something in the middle.

Cheers,
Rusty
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Old Jul 11, 2011, 12:08 PM
It wasn't me
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Augsburg, Germany
Joined Mar 2010
428 Posts
Quote:
Originally Posted by 13brv3 View Post
Vibration is a very complex subject, and any change makes a difference. I tell people "everything changes everything".

One thing that's certain is that reducing the vibration at the source is always good. That means balancing props and motors which is obvious, but it also means using a relatively streamlined material for the arms, so you don't transmit large pulses to the arms from the props. A round tube isn't the greatest aerodynamic shape, but it's better than square, or flat.
Of course, you're right: Reducing vibrations at the props and motors is the best thing to start but unfortunately it's almost impossible to totally eliminate them.

There would be a better shape than a tube if there is only one direction. But since a multicopter arm needs to be areodynamic in almost any direction, the round shape is the best choice in my eyes.


Quote:
Originally Posted by 13brv3 View Post
BTW, where's the yaw mechanism on that tri-copter? Funny thing is that I've never made a tri-copter in all the years I've been flying these things. For me, having a mechanical yaw control just spoils the whole multi-rotor concept.

Cheers,
Rusty
Between the center plates. On the first picture I had a cf lever on the yaw rod but it wasn't solid enough so I had to replace it with an aluminium lever.





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Old Jul 11, 2011, 06:16 PM
Registered User
VA
Joined Nov 2009
2,628 Posts
Quote:
Originally Posted by 13brv3 View Post
Morning all. I'll try to make this a group reply to keep from running up my post count too high

Pug398,

I haven't received many requests for 1/2" round blocks, so I'm afraid they're not really on the to-do list right now. If it were as simple as plugging 1/2" into the program, I'd make some for you, but finding the best size becomes a trial and error procedure, which it fairly time consuming. Once I get close, I have to make a bunch of blocks a few thousandths different in size to see which works best on average.
Thanks, Rusty. I kind of figured. Trying all the different undersizes is what has held me back from boring them out but I guess I will start small and work up gradually. I have the landing gear blocks to play with.
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Old Jul 11, 2011, 06:39 PM
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Canada, NL, Division No. 9
Joined Mar 2011
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Rusty: Just curious whether I should go with the 1/2" square tube or the TREX 500 booms for my Rev-8 Kit. I can likely source the 1/2" square tube alot easier locally and would have to order in trex500 booms from ebay everytime I have an issue.
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Old Jul 11, 2011, 08:01 PM
My RC builds in my profile.
daign's Avatar
United States, CA, Los Angeles
Joined Feb 2011
2,553 Posts
Quote:
Originally Posted by r0sewhite View Post
Hi Rusty,

vibrations are less at the center plates, not more. The cf arms are a little flexible but I have built a tricopter and this quad from cf and in both cases I noticed that the flexibility of the cf absorb vibrations.

I just plan a quad frame with/for warthox which will have cf tube arms. We hope to get a frame with least drag which is still solid. I have had a few crashes with my tricopter and though the arms are quite long, I never had any damage.

The only problem is that if I use T-Rex 450 tail boom holders like on my tricopter again, the center plates have to be very strong. That means, I can't shape big holes into the center plates to reduce drag.



that sure is purdy
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Old Jul 11, 2011, 08:09 PM
My RC builds in my profile.
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United States, CA, Los Angeles
Joined Feb 2011
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Quote:
Originally Posted by Grips View Post
Rusty: Just curious whether I should go with the 1/2" square tube or the TREX 500 booms for my Rev-8 Kit. I can likely source the 1/2" square tube alot easier locally and would have to order in trex500 booms from ebay everytime I have an issue.
or you could order a bunch of 5/8 spares at one time and save a ton of money.

TREX 500 booms = $20 per boom

I just ordered 2 x 60" 5/8 carbon pultruded rod from goodwinds.com. They even cut it into 15" sections for me for $80 shipped. I'll keep the spare sections for crashes or expansion.
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Old Jul 11, 2011, 08:41 PM
13brv3's Avatar
Navarre, FL
Joined Mar 2002
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Grips,

Totally up to you on the arm type. I've never used the 1/2" square arms myself since I prefer round tubes, but people wanted them, so I made the blocks. Round vs square is sort of a Ford vs Chevy decision, with Chevy being round tubes


Quote:
Originally Posted by daign View Post

TREX 500 booms = $20 per boom

I just ordered 2 x 60" 5/8 carbon pultruded rod from goodwinds.com. They even cut it into 15" sections for me for $80 shipped. I'll keep the spare sections for crashes or expansion.
I've ordered the aluminum Trex500 tubes for $12 per pair here:
http://www.readyheli.com/search.asp?keyword=h50040

I'm working on another odd little experiment using these, which is the first time I've used the actual Trex500 tubes.

It's also good to know that Goodwinds will cut the tubing. This is more important than most people realize, because if you make a ragged cut, then clamp too close to the end of the pultruded tube, it will split. I typically leave 1/8"-1/4" sticking past the far end of the block so I'm not clamping right on the end, and I've never had problems with them splitting from the clamps. I have split a couple that were too tight, and I tried to twist the motor to align it

BTW, that is a nice looking tri-copter yaw mechanism. Seems like a lot of trouble to keep from adding the 4th motor though

Cheers,
Rusty
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