No stress cracks yet - got UAV Bits today

[brianb87]

I got UAV Bits strong arms today. I do not have any stress cracks yet. Should I install them? 75+ flights. If so, any tips on installing them or just throw them on?

 

[D4T_PoM]

Brian I noticed a crack on my P3A after the 71st flight.

I have personally not used the UAV Bits kit but not sure if I would use them or if they work.

I changed my P3A for a P3P today due to a crack showing up.

I'm sure others can give their inputs.

Good luck

 

[III% Streve]

There is nothing in the strong arms setup that would suggest they help anything. If anything they will add stress.

 

[msinger]

If the screws are not pressed against the shell and cannot cause it to crack, then perhaps they would do something. No?

 

[III% Streve]

Not at all. There has to be something to support the "brace" to maintain the motor in the proper position. Extending the screws to be longer only increases the affect of the torque on them from the motor in all 3 axis'. The more direct, consistent, pressure there is between the added plate and the base of the P3, the more that added brace will assist in strengthening.
Put 4 fingers of one hand into the palm of your other hand, separated by an inch or so. Now wiggle your hands in different directions and your fingers give. Now set your palms together and move your hands. There is far less independent movement with palm to palm contact. Same logic in ANY mounting situation of anything. More consistent contact leads to more stability.

 

[beauyoung85]

If the screws are not pressed against the shell and cannot cause it to crack, then perhaps they would do something. No?

This. When used correctly they spread the force of the screws across the flat bottom portion of the shell, rather than being exerted directly on the shell in the weaker, recessed screw holes.

 

[msinger]

Put 4 fingers of one hand into the palm of your other hand, separated by an inch or so. Now wiggle your hands in different directions and your fingers give. Now set your palms together and move your hands. There is far less independent movement with palm to palm contact.

That makes sense. I guess all it really does then is prevent the screws from pulling through the shell.

 

[bobmyers]

That makes sense. I guess all it really does then is prevent the screws from pulling through the shell.

Which is how the motors separate from the mount when in flight-- the screws are pull out of the shell. With the plates or prop guard mounts, the screws cannot be pulled out. So, I would think that is a significant safeguard against a motor coming out which has already been reported in the forum.

 

[msinger]

So, I would think that is a significant safeguard against a motor coming out which has already been reported in the forum.

Agreed. If you already have cracks though, then these reinforcements might not be so useful. It seems they might be most effective if installed before the cracks start.

 

[bobmyers]

Agreed. If you already have cracks though, then these reinforcements might not be so useful. It seems they might be most effective if installed before the cracks start.

True-- I have had the propguard mounts on mine since the first week-- haven't removed them to check for cracks-- maybe I will do that this week.

 

[III% Streve]

Which is how the motors separate from the mount when in flight-- the screws are pull out of the shell. With the plates or prop guard mounts, the screws cannot be pulled out. So, I would think that is a significant safeguard against a motor coming out which has already been reported in the forum.

If the seperation happens you will still crash though

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[bobmyers]

If the seperation happens you will still crash though

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[III% Streve]

View attachment 31452

Is there a point behind that?

 

[redmoe]

If the seperation happens you will still crash though

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Given that reinforcement plate draws the motor into the frame and "sandwiches" it I think you would have a decent chance of landing the phantom if there were cracks completely around the motor. The puzzle piece nature of the cracking will prevent rotation and the motor will not be allowed to travel upward.

Aggressive maneuvers would be the enemy possibly driving the motor down. It seems possible to save it if the operator was aware of the failure due to odd flight behavior.

The reinforcement plates should help spread the load if they are making solid and even contact on the frame. They definitely should not make it worse unless they are loose allowing the slightly longer screw to apply increased force onto the frame.

Without some time spent with modeling software the stress points and mitigation techniques are still up for debate.