Tarot 650 quadcopter - fragile skid bars

Tarot put woven carbon fiber 10 mm tubes with 0.7-0.8 mm wall as skid bars. They are connected to 16 mm vertical tube by T-join. To keep skid bar in place it suggests to use M3 inner bolt which actually make whole construction even more fragile. I broke them in very first land when copter was not perfectly straight and "dropped" from about 2-3 cm.

I had cheap landing gear from F-450 like quad decided to use.

Set contains four 8 mm carbon fiber rods, so wrapped with tape it perfectly fit inside.

As can be seen it still working well with broken outer tube.

Tarot 650 quadcopter - folding joints

What is good in Tarot 650 frame  - light (~450g), strong, foldable and relatively cheap.

Foldability is goodnes but it's a weakness at the same time. 

Joins

There are two M2.5 bolts screwed from both sides. Holes in CF plates are exact diameter to hold bolt tightly. BUT! Not forever and not all of them. When you fold/unfold it bolts start to loose. Vibrations helps in that also.

You can say, Okay, tighten them before each flight. Agree if they are accessible. Since main plate design allows to put electronics on top or bottom, most likely bolts will be covered.

I looked at Tarot's Hex and Octo frames and they had joints designed slightly different. Why not to make same thing here?

What you need is enlarge hole to 3-3.2 mm so M3 - 30 mm bolt will go through. 30 mm is perfectly fit with nylock nut. This will keep all pieces together and no need to tighten every time.

Landing gear

Copter with such frame will weigh at least 2kg, most likely 2.5kg and stock legs can hold it only if landing gently and straight down. Any deviation - need spares.

Each leg has three connection points and moderate landing may result with bent metal parts and broken CF.

After it happened with me I decided not to order replacement, next time same thing happened. Instead I ordered 16 mm CF tube to cut segments. Found some old glass fiber boards and cut parts from them.

I'm using two small pieces of 16 mm tube, it looks steady and reliable but in case of mistake, it can be replaced by one long one, there is space inside frame for it.

New legs folds only 2/3 way or so. May be later I'll make these green parts longer to fold legs in full.

Now I need to reorganize surfaces and put all electronics back.

Tarot 650 quadcopter - quick overview

Hi All!
I built Tarot 650 quadcopter. It's nice frame but still not as good as it can be. Even for it's price engineers had to spend some time flying it.
Weak points:

1. There is not too much space to put electronics.
2. Folding joints are bad, after some time bolts starting to fall off. I lost two from arms during flight and one form leg.
3. Legs are fragile, especially 10mm horizontal piece. I broke them very in first landing when started to tune flight controller.

Let's go over all these weak points and try to enhance them:
Fragile landing skid
Joints and Landing gear