x8 650 vs 720 vs 850

jfro

jfro

Aerial Fun
I have a x8 w/ kde 3520's which runs around 9kg or 19.8lbs AUW.

I'm getting ready to put some retracts on it and finding I don't want to extend them to get outside the props @ 860mm or so. They are pretty tall now and I can either lengthen them, extend my bottom plate out so the retracts mount farther out on the frame or cut it back to 650mm or 720mm.

I like how it flies and it is pretty stable in moderately high winds.

My question is if I cut the arms back to say 720mm or even 650mm, and everything stays the same (20lbs ) with same 15" props, will I lose any of the stability or wind worthiness of the quad at 860mm?

I do have another quad with same motors that is 650mm and it flies pretty nicely, but does not handle the wind as well as the 860, but it's AUW is a lot less.

Any experience or thoughts are appreciated.
 

Pumpkinguy

Pumpkinguy

Member
Your explanation is somewhat confusing. For me anyway. Lol. When the legs are retracted you don't want them sticking out any further that the tip of the prop swings?
 

jfro

jfro

Aerial Fun
Ummmmm.... Have to rethink this. I was thinking they have to clear just the motors, but maybe I'm not right on that. I need to keep the cross piece out of the lower props. But you are probably right, I'd have to go out past the motor plus 1/2 the length of the props...

On a coaxial quad, (x8), I guess the end piece on the retract needs to stay underneath the lower props, not outside them?
 

Motopreserve

Motopreserve

Drone Enthusiast
Jim,

How far down would the retract's need to be mounted so they clear the lower props? Could you rig up a mount (like the extension of the plate you mentioned) that would put them low enough to be safe?

Would that put them in view of the video?

Seems like the stability you get now would be worth saving - so modifying the retract's somehow would be my vote.
 



jfro

jfro

Aerial Fun
To get the cross piece under the props, the retracts would have to mount underneath my antivibration mounting a Wssembly that the gimbal hangs off. Not sure if they would be in camera view or now. Will have to check.

From the video, it looks like the solution is to go with longer arms, which is the exact opposite I'd like to do. Guess this was a dual question post. Is a narrower quad/x8 as stable in heavy winds as a wider frame? Then, the 2nd part is what to do with retracts....

Would look at rotating legs like on Cinestar, but not sure the Centerpiece based gimbal can handle this....
 

Motopreserve

Motopreserve

Drone Enthusiast
The phobotic at this point is definitely not working consistently (if at all) with rotating landing gear. That would certainly be the easiest fix to eliminating the LG in the video, but it looks like it might take some time for the CP to handle it.

I don't know for sure how the diameter of the MR motor-motor effects handling in wind - but I would assume if you are getting good stabilization with the current X8 size, better not to mess with that. Can you just shorten the length of the runners so they fit between the booms like in the video Pumpkin posted???
 

jfro

jfro

Aerial Fun
Look like if I shorten each arm 2", the legs would clear on 15" props. Maybe 16", This would take my quad down to a 780mm, which is still pretty wide.... I need about 1/4" more clearance under the bottom plate to the anti-vibration plate to mount the retracts, so longer standoffs would be in order, which is should be ok. Will probably go to a stronger standoff for that.

So, I'm back to the question, what will 4 inches or so on the frame do to stability?
 

Motopreserve

Motopreserve

Drone Enthusiast
Do you have a photo of the retract's sitting at the sides the way they'd be if in in up position?

The answer to your question is: removing 4" would change it :).

And considering you have been so happy with the performance - that's why I suggesting modifying the retract's as opposed to the booms. I guess if you have extra booms you could try and go back. But it seems there must be an easier answer that wouldn't disrupt a perfectly functioning X8.
 


jfro

jfro

Aerial Fun
Edit. I'm going to extend the legs 2" and see how that works.... Was going to order new ones but I forgot I have more than enough 25mm and 22m cf tube, so I'll sleeve an extra couple inches on to end that goes into the retract. Give it more stiffness and strength. Cost me nothing other than a little expoxy and 10 minutes in the shop.
 
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Motopreserve

Motopreserve

Drone Enthusiast
If extending the retract's down-booms works it could have the added advantage of giving you more ground clearance for the larger gimbal.
 

Pumpkinguy

Pumpkinguy

Member
Exactly.

I'm using 520mm legs on my retracts. Those gimbals hang quite low. Once I get the gimbal and mount it, I bet there is not much clearance even with those long legs.
 

jfro

jfro

Aerial Fun
Went with 3 " extension, figuring I could cut em back a bit if they are plenty long. I'm using 15' props, but need 16" if I add heavier camera.

Big winds today and tomorrow, but should get this up Sunday during the day. Probably will start with the gimbal on after seeing if they work at 50 yards while holding it off the ground....
 


jfro

jfro

Aerial Fun
Looks like I'm going to be about 460mm to 465mm from the axis. My stationary legs were already a bit higher than they needed, so now I will be even higher. Might get them mounted tomorrow or late tonight, so will know what my final length will be then.
 

jfro

jfro

Aerial Fun
Dumb Dumb Dumb, or stupid me if you prefer.

I lengthened the legs and it looked good. Had to modify the anti-vbration plate a bit to fit between retracts and that worked well.

Then, much to my chagrin, find I'd have to drop my gimbal about 4-5 inched to fit between the retracts. A, oh boy, I didn't think of that moment.

Look like I"m going to make 2 new plates and widen the plate on the left and right side about 1 to 1.5" to get the legs out farther. I'll leave the legs longer for the moment, but will probably be able to shorten them back or pretty close to what they were before. Just need to clear the 16" props although I fly 15" most of the time.

Good news is when I took of the old legs and weighed them, then weight the new retracts, I'm only adding 3-4 oz. overall.

Giving up and watching the masters..... Deflated.... Missed a nice day for testing. Blue sky and mild winds.....
 

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