Upgrades to rebranded JJRC H25G quadcopter

[Chuck]

As I previously suspected, there are some common mechanical parts between the JJRC H25-series quads, and the Syma X8-series quads. I recently recieved two sets of three-blade rotors that I ordered online, listed as replacements for the standard two-blade rotors, for Syma X8C, G, HG, and HW quads. Just as they appeared in the online ad, these rotors along with standard two-blade replacement rotors for the Syma X8 quads, have the exact same attachment sockets, as standard two-blade rotors for the JJRC H25 quads. I have installed these rotors, which are slightly smaller in diameter than the two-blade rotors. Hopefully, I will see an improvement in the quad's performance.

 

[Jackson]

Probably less flight time.

 

[Chuck]

I anticipated that with the original 7.4v 1800 mAh lipo battery. I upgraded with a 2500 mAh replacement battery.

 

[Jackson]

the original 7.4v 1800 mAh lipo battery. I upgraded with a 2500 mAh replacement battery.

The 2500 may be heavier.

 

[Chuck]

The 2500 may be heavier.

Slightly, but it does fit within the same compartment. What I have found to my puzzlement, is a tendency for the quad to on liftoff, tilt abruptly over to the right, and attempt to flip over. I made sure that the three-blade rotors are in the correct orientation according to the original two-blade rotors, and that they all turn freely. Yet it still happens. I have reinstalled the original two-blade rotors, until I figure out whst is going on. That restored normal flight control, though I still have the issue with it stalling during landing attempts, and dropping like a rock. I was hoping that the three-blade rotors with their additional lift capacity, would help to slow decent on landings to a more controllable rate.

 

[Jackson]

is a tendency for the quad to on liftoff, tilt abruptly over to the right, and attempt to flip over. I made sure that the three-blade rotors are in the correct orientation

Doesn't sound like it. Should not make a difference. Double check the orientation of the leading edge.

 

[Chuck]

If this reaction occurs with the rotors in proper orientation regarding their leading edges, what else could contribute to this happening? I not only double checked the rotor orientation, I also did the motors to make sure that when I installed the replacement FCB, that they were wired properly to turn in the correct directions under power.

 

[Chuck]

I've had a couple of cracks reappear in the lower body of my rebranded JJRC H25G, that were previously repaired. I'm going to try a different approach to repairing them this time. Using Krazy Glue to repair them as before, only this time, patching over with aluminum sheet from a soda or beer can, held in place with a thin layer of epoxy and a couple of tiny screws. The aluminum sheet is strong enough to prevent the cracks from widening again, yet thin and light enough that it shouldn't affect the weight balance.

 

[Jackson]

patching over with aluminum sheet from a soda or beer can, held in place with a thin layer of epoxy and a couple of tiny screws.

Sounds like unnecessary overkill.

Maybe a less brittle adhesive would be a better choice.
https://www.amazon.com/IC-2000-Rubb...&qid=1475947111&sr=8-2&keywords=rubberized+CA

A quick story. When I was young my father had a 47 Harley Knucklehead that had been bored and stroked. Quite fast but with an insane amount of vibration. He was always shearing motor bolts. A guy at work gave him higher grade, probably case hardened replacements. These did not break, now he broke the frame's motor mounts instead. Stronger was not the solution, isolation by using rubber (which became standard eventually) was.

 

[Chuck]

Sounds like unnecessary overkill.

Maybe a less brittle adhesive would be a better choice.
https://www.amazon.com/IC-2000-Rubb...&qid=1475947111&sr=8-2&keywords=rubberized+CA

A quick story. When I was young my father had a 47 Harley Knucklehead that had been bored and stroked. Quite fast but with an insane amount of vibration. He was always shearing motor bolts. A guy at work gave him higher grade, probably case hardened replacements. These did not break, now he broke the frame's motor mounts instead. Stronger was not the solution, isolation by using rubber (which became standard eventually) was.

I tried isolation back in late spring, using rubberized chair leg/furniture leg cushions cemented to the bottoms of the landing struts. The result was that when landing, it would bounce around like a basketball. Clearly, some form of cushioning for landings to reduce the impact on the body is necessary. Perhaps something that is spring-loaded like a shock absorber.

 

[Jackson]

I tried isolation back in late spring, using rubberized chair leg/furniture leg cushions cemented to the bottoms of the landing struts.

So it's the landing struts you've been talking about?

 

[Chuck]

So it's the landing struts you've been talking about?

The landing struts are firmly attached. The problem being that because they are solid and there is no cushioning between them and the lower body, a hard landing results in lower body cracks forming. Either the throttle, or the FCB, has a hair trigger sensitivity. When I reach a certain point of throttling back for a landing, the motors cut out abruptly, causing an immediate drop, and a hard impact.