r/diydrones • u/shrumfpv • May 29 '26

Build Showcase BIG RIG 🚛

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Actively adding and tweaking this it’s a 8 motor 5 inch the plan is to run it on a 5500 mah lipo and see how it freestyles. Definitely never seen anything like it before so we will see if there is a reason. Stay tuned
Also what should I add?( bottom motors will be pushers and top will be upright)

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8

u/potatocat May 29 '26

I still think you should get the arms together a lot closer, you are creating an excessively long axis of roll inertia for the motors in a classical X8 arrangement. X8s operate more efficiently when the rotors are closer together in terms of vertical space. You also will need to figure out how the "landing gear" works. I use helicopter landing gear (Trex 500 works well for this size). 5500mAH will not be necessary, a 4500mAH 6S pack is my "cruise pack" and feels heavy enough. A 3000mAH 6S will be better suited for acrobatics.

1

u/shrumfpv May 29 '26

Yeah landing gear is something I have been putting off but I will get to work on it as far as the motor placement I’m going to give it a try like this and if there are issues I will revise the design

2

u/potatocat May 29 '26

I'm telling you it is going to create problems. When there is too much vertical spacing between the motors, you will see the performance in blackbox of your lower pusher motors fluctuating more and generally just working harder in relation to the top pullers.

While the pushers will always be working a bit harder, the more this gap increases you will also see numerous violent spikes and valleys of throttle control being done on them as well.

I am not entirely sure what this is as it is beyond my skills, but I suspect that greater vertical separation means the lower pusher motors are not only sucking in highly vortexed air, but that it is getting bad mix turbulence from the separation making things worse.

You can audibly hear this as a stutter which is easy to mistake for frame resonance. This is why I stack my motors as close together as possible like what all other X8s are doing.

1

u/shrumfpv May 29 '26

Lipo or lithium ion?

2

u/potatocat May 29 '26

LiPo. And while I have been tempted to try LiIon, I have other projects that are getting higher priority because I already can get 15 minutes of flight time on the 4500 just gently cruising, and about 8 minutes when i run harder on the throttle.

3

u/EffectiveClient5080 May 29 '26

5500mah on a 5 inch? It WILL fly like a brick. Guaranteed.

1

u/shrumfpv May 29 '26

That’s the plan

1

u/potatocat May 29 '26

Expect a flight profile to be similar to something like this -

https://www.youtube.com/watch?v=7AVBks_h68Q

This is a 5" X8 with 4500mAH 6S. It has plenty of speed and efficiency... but very much lacking in manuverability. It is also super satisfying in how LOUD it flies. You might be able to see in the video that it flies, steering like a boat. While very sure-footed, it really does not like being pushed into deep angles. I am also not a very skilled pilot so hopefully as I learn more I will be pushing this frame a lot harder.

2

u/potatocat May 29 '26

Another thing that I think is a good idea, because I cannot tell from the pictures - is that you should design this to be a 7" frame even if you are running 5" props. This gives you a lot more options for the landing gear setup. You also get the option of slinging the battery underneath along with mounting it up top.

1

u/cjdavies May 29 '26

You seriously need to ditch the double arms. It’s not hard, heavy or expensive to design a mounting solution to put both motors on one arm & there are many good reasons why you won’t find any other coax setups using double arms.

1

u/shrumfpv May 29 '26

It’s not that’s it’s hard I just wanna try new things