Knuckle H-Quad

[xuzme720]

I think that is a real possibility. Those booms are a very flat surface and act like an air dam right in the wash path. On the knuckle quad, you are looking at 4 square inches more of obstruction to the thrust column.
One other thing to consider, since the knuckle is so much more agile, you might be just a tad freer on the throttle, unless the longevity tests are done at hover only...If so, then it's probably the extra boom killing the flight time.

 

[jackedman]

Im i the only guy that didnt buy the flite test motor mounts??

 

[xuzme720]

Surely not, but they do work well on the smaller motors. I had some flex issues when I tried to use NTM2830's on them...

 

[cranialrectosis]

The pictures of the all black quad at the top of this thread show the same issue I have and it is related to a shorter motor boom. The rotors are over the knuckles as well as the boom.

The amount of 'air dam' in the wash I have is huge.

Solutions: longer boom or skinnier hub.

I'll post what I find when I try the skinnier hub. Gotta get the Anycopter with the MultiWii in the air first.

 

[Bayboos]

Hi all

I just wanted to share a clever idea (my brother's invention, improved by me) for a landing gear. All you need is some left-overs from heavy-duty zip-ties - you don't even need the main "zipping part" - and a drill; and it's mounted using existing screws (the ones holding motor mount in place). Here's how it looks like:



This is one of those "weights noting, survives everything" landing gears; it can be made in no time, is capable of absorbing a lot of energy from not-so-perfect landings and - most of all - it's CHEAP (since it's made from things that you usually throw away).

You can find more photos of this landing gear (and the entire quad, and other models) in the gallery - there is a link under the photo above.



I'd also would like to add two words about reduced flight time on this quad vs anycopter X-quad. There is one factor that is usually greatly underestimated - props cross-interferrence. Please note that when using 8" props in this design, you have less than 2" distance between prop tips front-to-back and just above 3" side-to-side. In low-speed applications, it is practical to assume that the gap should be at least equal to the diameter of a prop to reduce the interferrence below a point where you can notice it. The gap smaller than that will always cause problems - not only with reduced efficiency, but also with increased instability in certain flight conditions (most noticeable during vertical descend).

On the other hand, the motors and props adds up to the significant part of quad's wieght, and having the weight as close as possible to the C.G. makes it much more agile (and less stable). This property is desireable when you are building aerobatic/3D multicopter; but not necessarily good in FPV applications. As always, it's a matter of finding the best cost/benefit ratio.

Good luck and have fun!

 

[RoyBro]

Hi all

I just wanted to share a clever idea (my brother's invention, improved by me) for a landing gear. All you need is some left-overs from heavy-duty zip-ties - you don't even need the main "zipping part" - and a drill; and it's mounted using existing screws (the ones holding motor mount in place). Here's how it looks like:

What motor mounts are you using?

 

[Bayboos]

My brother bought them as a part of Anycopter Quad kit - he broke the hub and legs some time later, but the motor mounts were fine. I've managed to break just one of them. I cut the replacement from single-coated 2mm glass-fiber electric board using one of the remaining mounts as a template The replaced mount is visible on this picture (in the upper right "corner").

 

[jackedman]

looks good i like the landing gear nice idea I have to keep my big zip ties from work. How big is the loop?

 

[jhitesma]

I like the look of that method. I went with the zip tie method I saw in a post on the main site: http://flitetest.com/articles/diy-landing-gear-for-multirotors

They've worked out great for me:


Though I did find if I leave the little zip ties that attach the big zip ties loose then I don't have to replace them when I break an arm. Just slide them off the ends of my arm and back on the new ones. Plus they can shift a bit under overly hard "landings" and help absorb the shock

I like the cleaner look of the screwed on method...but this is my first quad and I'm treating it like an old pickup truck and bashing it around...so being easy to repair trumps looking good for now

 

[Bayboos]

@ jhitesma:
I do see you don't use screws for mounting a motor to the frame - this is something I would never dare to do. For me, everything else may come off, even in mid-air; but the motor have to stay in place at all costs - this is the only thing that can seriously hurt someone or damage something.

I was using the method from this article, too - you can see it in my GALLERY, along with this quad's evolution from Anycopter-like X-quad (when I've got it from my brother) to today. "Further testing" showed that it's not perfect for H- or I-quads. This method was invented for +/X quads, where two arms - and thus legs - are set up perpendicular to the other two. The landing gear described in the article is much stiffer in one direction than the other, which cancells out pretty nice in +/X quads, but adds up pretty bad in H/I quads. Every material - especially the one that takes beating - softens a bit after a while; I've found out that after some not-so-perfect landings this landing gears tends to bend to the side on every landing, even the very soft/gentle one.

If you will take a closer look at my picture (preferably by going to the gallery to see bigger version), you will notice that the ends of each zip-tie don't meet - those are screwed in to different points, by different screws. And that's intentional, solely to eliminate the tendency described above. And believe me, this landing gear can absorb a lot of energy, too - there is no glue used in any place, so the ties can rotate around the screws on impact. And they do. I've never broke anything more than a prop since I have those legs. And after that, you just need to rotate them back (with one finger) to proper place, and they will be as good as new.

Another advantage came to my mind when I was looking at your picture - the landing gear from the article can have sharp edges at the bottom end (from cutting the tie), that can - if not covered or flatened enough - damage the paint job on your car's hood. I know that the plastic from zip-ties is not the hardest material in the world; but sharp edges tends to do damage anyway, no matter what they are made of. My version have sharp edges hidden close to or even under the boom where they can do no damage at all, leaving the "surface meeting" side flat as much as it can be.

And the last word about repairs: if I'd break the arm/boom and I'd need to replace it, I would unscrew the motor mount anyway, right? The legs will come off at the very same moment, and will be mounted back to the new boom the same way. This is the only part of my quad that I'm sure I'll never have to replace with new ones EVER

@ jackedman:
Each loop is approx. 2" in diameter, made from a strip that is approx. 7" long; the strips themselves are 1mm thick and 8mm wide (metric system is more popular on this side of the universe). Those are approximate numbers, since they were never measured in any way. The only important thing is to keep all the strips of the same length, and the diameter will become equal for all of the loops "by itself".

Note that the longer strip you use, the softer the landing gear will be. In my opinion, 2" diameter is a bit too small for the quad of this size/weight - it should be a touch bigger (2,5 to 3"); but the funny part is - the heavier quad you have, the smaller (and better-looking) this landing gear can be.

 

[jackedman]

Thanks man that was some good info

 

[jhitesma]

Mounting motors with zip ties scared the heck out of me as well at first. But after seeing it promoted on just about every FT multi build and many many others I figured I'd give it a try. The way mine are done is honestly the worst possible way to do it, but the holes on the HK BW motors mounts are too small to pass a zip tie through for the method I'd rather use. The reason for using zip ties instead of screws is as explained in the FT videos and David's videos is that in a crash the zip tie will break instead of damaging a motor. Get big enough with a motor and there's no way I'd trust a zip tie. But with fresh decent quality zip ties they've proven completely reliable on these little motors and just about every FT/RCE multi build has used zip ties to hold DT750's.

As for the ties softening - yes, they have softened up a bit but still work just fine on my H setup. Every couple of landings I just have to adjust their position a bit and with them being loosely mounted with zip ties it's super quick and easy.

The sharp edges at the bottom I covered with hot glue since I was filling the locking mechanism with glue anyway to keep them from moving. So it's got nice rubbery hot glue bottoms. And even so...I think you can tell from the photo that paint is the least of the concerns about my hood

I've seen several other ways of doing zip tie landing gear as well - and I think they're all great! When I eventually build a nicer quad or hex that I don't plan on crashing every other flight I'll probably do something like yours because I love the look of them. But on a basher like this which is outright abused daily....the quick on/off of the zip tie mounts outweighs most other concerns

 

[Bayboos]

@ jhitesma:
It's very nice to know that somebody actually likes how it looks - it's not so often that my creation looks at least in part as good as it works; and it wasn't made to look nice anyway. So thanks for the nice words.

One last thing about zip-mounting: I'm affraid this is the place where my past experience as aircraft mechanic (so-called "full scale", which is not entirely correct since those are not build to any scale; they just are this big and that's all) comes to play. I would never use anything that even remotely can cause the engine to fall off; and I'll avoid using glue of any type and in any application where It's reasonable. After all, my landing gear was designed to meet just two goals: reduce the disadvantage of different stiffness in different directions while being as cheap and easy to build as possible. And I believe those two goals are met; and especially the second one is met the best way possible (because of re-using materials that usually are considered useless and thrown away; and nothing else). All other advantages are extra.

@ jackedman:
You're welcome!

 

[tophe75]

OK, so here is mine.



All my parts are 3D printed and after test flight I can say that I am more then satisfied how the printed parts perform.
They also serve as "the week" part, so if you crash the plastic brakes and all you need is to print a new part.



I am using the hobbyking Q Brain quad ESC (4in1)



The motor mounts and legs is my design and I thing it looks better then FT's as they keep to the same pattern as the rest of the copter.



If you have your own 3D printer (or want to order from your local 3D print shop) all the files can be found here:http://www.thingiverse.com/thing:163794

 

[jackedman]

nice mounts

 

[Fbords]

I was wondering how this quad handles given it's considerably smaller than the Anycopter quad. I'd expect it to be a little more agile and twitchy at times. I know both can flip and roll, but I'm looking for something that can get smooth aerial video footage. Looks like a lot of the good aerial shots in the video were from a go pro on a hex

 

[Mustang7302]

If your goal is a smooth aerial video platform, the Knuckle H is not ideal. You want a wide foot print which is more resistant to changes in orientation, a well dialed in flight controller, and reduce as much vibration as you can before getting to the the isolated gimbal and camera. The Anycopter with 14" booms and lower KV motor swinging larger props would be more ideal; it will fly mushy but should be much smoother for videography.

 

[Hasi]

I am making a european version of the knuckle, with 10x10mm booms:

 

[gunkaaac]

I am making a european version of the knuckle, with 10x10mm booms:
View attachment 16265

View attachment 16266

great that someone post measurements of knuckles and everything.

 

[cranialrectosis]

"great that someone post measurements of knuckles and everything"

FT provides plans for all their kits. You don't have to buy anything from FT. Check the links on the page for the product. You will find the plans so you may print them and paste them to 1/8" plywood and get cutting.