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Gimbal bubble tests; some observations

Former Member

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I've been busy buying, selling and repairing Mavics, in addition to working my other full time job, but in my spare time I have been doing some testing and trying to prove fact vs fiction. My last test determined that the mechanics of the Mavic are capable of flying full throttle in sport mode for an entire flight on an 88° day with no overheating issues, and now I have done some more testing.

I was always under the (mis)understanding that flying or running the Mavic with the gimbal protective bubble (not the gimbal clamp) on for any extended length of time will cause the internal temperature of the Mavic to rise. I also thought that leaving the protective bubble on will cause undue stress on the cooling fan and it's ability to provide air circulation with the gimbal cover on. I proved myself wrong today.

Using an anemometer, I clocked the fans output on the bottom of the Mavic at 77mph right under the sonar sensor. There is an outlet there where hot air is dispelled. There are 2 ports at the aft end of the Mavic that I thought were air outlets, but they are not outlets.

I turned on the Mavic with the bubble off, and clocked fan output at the bottom outlet at 77mph. I clocked the rear ducts and received no inflow or outflow at all. The internal board temperature of the Mavic after 10 minutes was 98°. The bottom cooling fins were at 110°.

I then started the Mavic with the bubble on. After 10 minutes on the desk, the internal board temps were at 98° and the output at the bottom outlet was identical to what it had been with the bubble on, 77mph, and the cooling fins were also the same temp as with the bubble off. Again, I found no in or outflow from the 2 aft ports.

My last test was folding up the Mavics 4 arms and doing an inflow/outflow test in folded position. This test led me to the same conclusion as the 2 previous tests. With the Mavic sitting folded on a table and power on for 10 minutes, the cooling fan with or without the gimbal cover was able to expel air at 77mph and not increase the internal components temperature at all. The Mavic does not sit flat on a level surface when folded, it is raised by the 4 folded arms almost an inch above the level surface. That was enough to let air get out of the bottom outlet.

In summary, flying with the bubble on will not increase the internal temperature of your Mavic or make the fan work harder. It might distort your images, but wont have an adverse reaction to your mechanics.

In addition, updating firmware with Mavic sitting on a flat table, arms folded, and bubble on will not raise the internal component temperatures, nor will it impede airflow or place undue stress on your cooling fan. I take off the bubble anyway, but that's just me.
 
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dwallersv

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Cool (pun intended), and thanks for testing this.

Now, we need to repeat the experiment (and results) independently to really make the findings solid. Anyone else with a handheld anemometer that could do it?
 
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AlwaysAWOL

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I too am not a bubble boy

After buying the bird, and all that can be involved in getting to a location for some unique shots, the last thing I want is possible distortions or flares!

Fly, be free, if I crash and burn my Mavic it was worth it!
 

Cyberpower678

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I've been busy buying, selling and repairing Mavics, in addition to working my other full time job, but in my spare time I have been doing some testing and trying to prove fact vs fiction. My last test determined that the mechanics of the Mavic are capable of flying full throttle in sport mode for an entire flight on an 88° day with no overheating issues, and now I have done some more testing.

I was always under the (mis)understanding that flying or running the Mavic with the gimbal protective bubble (not the gimbal clamp) on for any extended length of time will cause the internal temperature of the Mavic to rise. I also thought that leaving the protective bubble on will cause undue stress on the cooling fan and it's ability to provide air circulation with the gimbal cover on. I proved myself wrong today.

Using an anemometer, I clocked the fans output on the bottom of the Mavic at 77mph right under the sonar sensor. There is an outlet there where hot air is dispelled. There are 2 ports at the aft end of the Mavic that I thought were air outlets, but they are not outlets.

I turned on the Mavic with the bubble off, and clocked fan output at the bottom outlet at 77mph. I clocked the rear ducts and received no inflow or outflow at all. The internal board temperature of the Mavic after 10 minutes was 98°. The bottom cooling fins were at 110°.

I then started the Mavic with the bubble on. After 10 minutes on the desk, the internal board temps were at 98° and the output at the bottom outlet was identical to what it had been with the bubble on, 77mph, and the cooling fins were also the same temp as with the bubble off. Again, I found no in or outflow from the 2 aft ports.

My last test was folding up the Mavics 4 arms and doing an inflow/outflow test in folded position. This test led me to the same conclusion as the 2 previous tests. With the Mavic sitting folded on a table and power on for 10 minutes, the cooling fan with or without the gimbal cover was able to expel air at 77mph and not increase the internal components temperature at all. The Mavic does not sit flat on a level surface when folded, it is raised by the 4 folded arms almost an inch above the level surface. That was enough to let air get out of the bottom outlet.

In summary, flying with the bubble on will not reduce the internal temperature of your Mavic or make the fan work harder. It might distort your images, but wont have an adverse reaction to your mechanics.

In addition, updating firmware with Mavic sitting on a flat table, arms folded, and bubble on will not raise the internal component temperatures, nor will it impede airflow or place undue stress on your cooling fan. I take off the bubble anyway, but that's just me.
I'VE LITERALLY BEEN SAYING THIS TO EVERYONE CLAIMING OTHERWISE ALL ALONG!!!!! Thank you for presenting these cool facts, to prove what I've been saying.
 
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Big Fil

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Here's what makes this interesting. Your results say there is no heat difference yet another guys testing shows an increase in temps when the bubble is on. I don't have a horse in the race either way but I think without further testing the jury may still be out on this one.

 

mamayda

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It comes down to basic thermodynamic principles. If the air flow volume at the exhaust remains unchanged with the bubble attached, the system's ability to exhaust internal heat is also unchanged.
 
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rydfree

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I don't make videos but right after getting the Mavic I posted that testing with a thermometer there was no difference with the bubble on or off . Yes it produces lens flares but there are good uses for the bubble when new pilots are learning .
 

tkinva

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In summary, flying with the bubble on will not reduce the internal temperature of your Mavic or make the fan work harder. It might distort your images, but wont have an adverse reaction to your mechanics.

In addition, updating firmware with Mavic sitting on a flat table, arms folded, and bubble on will not raise the internal component temperatures, nor will it impede airflow or place undue stress on your cooling fan. I take off the bubble anyway, but that's just me.
I think that the tests would be more meaningful if you could find a way to do this comparison while the Mavic is in flight.

Both hovering and moving around. Flying generates a lot more heat than sitting on a table.

I suspect that there would be a ram air effect while the Mavic is moving forward, and the bubble might block this.

Also, there might be data on the internal temperature in the flight log.

--
- - Art from the Air - -
 
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Jaysjob

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In summary, flying with the bubble on will not reduce the internal temperature of your Mavic or make the fan work harder. It might distort your images, but wont have an adverse reaction to your mechanics.
I appreciate your testing and time to report your findings. However, bench testing is much different from actual flight so I'm just not sure the findings are enough to make your summary assumptions. A wind tunnel and/or ability to test the Mavic "in flight" would be needed before the summary conclusions could be made.
 

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I think that the tests would be more meaningful if you could find a way to do this comparison while the Mavic is in flight.

Both hovering and moving around. Flying generates a lot more heat than sitting on a table.

I suspect that there would be a ram air effect while the Mavic is moving forward, and the bubble might block this.

Also, there might be data on the internal temperature in the flight log.

--
- - Art from the Air - -
No, I have tested this in my previous thread. Hovering and moving around does not generate more heat than sitting on a table.

There is no ram air effect because there was no change in velocity with the bubble on or off. If ram air had any effect, it would have been realized as the difference between bubble on and off. There was no difference.

The effects of heat on Mavic; Some good news
 

Former Member

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I appreciate your testing and time to report your findings. However, bench testing is much different from actual flight so I'm just not sure the findings are enough to make your summary assumptions. A wind tunnel and/or ability to test the Mavic "in flight" would be needed before the summary conclusions could be made.
My previous flight test.

The effects of heat on Mavic; Some good news
 
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Former Member

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Here's what makes this interesting. Your results say there is no heat difference yet another guys testing shows an increase in temps when the bubble is on. I don't have a horse in the race either way but I think without further testing the jury may still be out on this one.

Yes, he says the temperature did go up but his test was extremely limited. He keeps saying the globe makes a temperature difference of 1-2°. That is not a temperature difference, it's an anomaly. Same test, same location, same ambient temperature, no noticeable difference between globe on and globe off. Not to mention that 60 - 90 seconds is not enough time to make a judgement on temperatures especially when the ambient temp is 40° lower than the temp results of heat sink after the first test. The boards and heat sink take time to warm up, he started at 64 and flew for 1 minute. The sink might not have reached full temp by then. In the second test, the sink was already warm and would take less time to get to the 101° he measured. No proof and not a good test. All this is moot, because the Mavic components, motors, battery, ESC, gimbal can all withstand temperatures up to 120° and not cause any adverse affects.

In addition to the test that he did, in another test, I measured the internal temperatures of the boards, he tested only the heat sink, which is insignificant compared to the temperature of the boards. He is guessing that the ram air would make a difference in reducing temperature of the heat sink. Yes, it does, but that has no relation to the temperature of the internal boards in the Mavic. The heat sink temperature during my sport mode test rose to only 115° and the internal components only 96°.

One last fact. The gimbal blocks most airflow into the fan inlet. The fan turns at a much higher RPM and generates a 77mph force at the outlet on the bottom of the heat sink. A 25 mph flight would have no affect on the speed of the fan or circulation of air caused by ram air. In effect, there is no ram air.

Gotta go repair some more drones. Later everyone!
 

Former Member

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It comes down to basic thermodynamic principles. If the air flow volume at the exhaust remains unchanged with the bubble attached, the system's ability to exhaust internal heat is also unchanged.
You sound like a bright guy so can I ask you a question?

Let's say a floor fan is sitting stationary, facing and blowing north, and the air coming out is traveling at 77mph. There is still wind. All of a sudden a 25 mph wind comes from the south (behind the fan), and blows into the fan. Will the fan speed increase because of the wind coming from behind it? This will answer some questions about how ram air can or cant affect the Mavics fan.
 

rydfree

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LOL , people are going to believe what they wish to believe . Discussing Ram Air effects on a camera drone is pointless . Not enough speed to ever matter and the gimbal will disrupt the airflow much more than the dome . The dome would actually probably help the fan due to causing a low pressure area that the fan could more easily draw from the slot opening . I've designed successful ram air systems before on bikes and dyno tested a 3-5 HP increase but only attained at high speeds . With 60mph winds being forced fed into the intake the gain was not even measurable . 120-140 + mph yes but not worth the effort .
 
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Former Member

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LOL , people are going to believe what they wish to believe . Discussing Ram Air effects on a camera drone is pointless . Not enough speed to ever matter and the gimbal will disrupt the airflow much more than the dome . The dome would actually probably help the fan due to causing a low pressure area that the fan could more easily draw from the slot opening . I've designed successful ram air systems before on bikes and dyno tested a 3-5 HP increase but only attained at high speeds . With 60mph winds being forced fed into the intake the gain was not even measurable . 120-140 + mph yes but not worth the effort .
That's helpful information.

I could use a little science lesson. Let's say the dome is in place, and the fan is on. Drone is sitting still for this example because as you and I have determined, ram air in this case is irrelevant. I clock the outlet air flow on the bottom at 77mph. Then I put the dome on and the outlet is still clocking at 77mph. You mentioned that air might be able to draw from the slot opening. Do you think the air it could draw from that slot could equal the air it could draw from the front grill without the dome on? Could it create a low enough pressure situation to make the fan draw more easily from the slot? It has to be drawing air from there or somewhere else, because how could the outlet air flow speed not decrease when the dome is applied, with no other air source.

Another source for air that I thought about was the 2 ducts in the aft of the Mavic. I clocked zero air being sucked into or being pushed out of those vents, so Im not sure what their purpose is. Could they be there just to dissipate heat?
 

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... Will the fan speed increase because of the wind coming from behind it? This will answer some questions about how ram air can or cant affect the Mavics fan.
A simple test to gauge any noticeable RAM effect might be to fly the Mavic around a course forwards and backwards comparing the difference in temperature. Any ram effect would show it running cooler flying forwards I expect. Could also do it gimbal cover on/off as well. Easy enough to do in Waypoint mode.
I reckon it will make no difference though.
 

dwallersv

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It comes down to basic thermodynamic principles. If the air flow volume at the exhaust remains unchanged with the bubble attached, the system's ability to exhaust internal heat is also unchanged.
Not quite, Kemosabe :D Don't forget that the air has to flow over the hot components, so the flow pattern is critical too.

It's entirely possible that when the bubble is on, air enters elsewhere on the body, closer to the exhaust, failing to flow over and remove heat from components further "upstream".

This issue is one of the most common mistakes home hobbyists make when building their own PC. They think that CFM flow of the cooling fan(s) is all that matters, when in fact how the system is ducted to direct airflow is more important to keep things from overheating.

Now, all that said, I doubt very much the MP is leaky in any significant way like this. It looks pretty tight and well-designed. Someone was responsible for engineering the cooling.

Still, it would be interesting to do a smoke test and see where the air's flowing in with/without bubble.
 

Former Member

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The dome would actually probably help the fan due to causing a low pressure area that the fan could more easily draw from the slot opening
Amazing that this is true. I just did a smoke test, held the smoke under the gimbal with bubble off and got a good incoming stream of smoke flowing out through the heat sink outlet on the bottom of the drone. The air that was being inducted into the fan grill was widespread and random, but still got a good stream out the bottom heat sink.

I then tried it with the bubble on, and the incoming smoke stream grew very narrow and actually looked like it increased in velocity. The stream out the bottom of the heat sink looked about the same.

My conclusion is just what @rydfree had said. Low pressure sucking the smoke into a smaller area increased the velocity of the air inflow.

Anyone know what physics principal this would be? Bernoulli's? Newton's second law of motion?
 
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Cyberpower678

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Amazing that this is true. I just did a smoke test, held the smoke under the gimbal with bubble off and got a good stream of smoke flowing out through the heat sink outlet on the bottom of the drone. The air that was being inducted into the fan grill was widespread and random, but still got a good stream out the bottom heat sink.

I then tried it with the bubble on, and the smoke stream grew very narrow and actually looked like it increased in velocity. The stream out the bottom of the heat sink looked about the same.

Anyone know what physics principal this would be? Bernoulli's?
I should be able to answer this since being an EE required me to study all the disciplines of physics including quantum, but lacking the use for such information, I can't say. :/
 
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mig25

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I've been busy buying, selling and repairing Mavics, in addition to working my other full time job, but in my spare time I have been doing some testing and trying to prove fact vs fiction. My last test determined that the mechanics of the Mavic are capable of flying full throttle in sport mode for an entire flight on an 88° day with no overheating issues, and now I have done some more testing.

I was always under the (mis)understanding that flying or running the Mavic with the gimbal protective bubble (not the gimbal clamp) on for any extended length of time will cause the internal temperature of the Mavic to rise. I also thought that leaving the protective bubble on will cause undue stress on the cooling fan and it's ability to provide air circulation with the gimbal cover on. I proved myself wrong today.

Using an anemometer, I clocked the fans output on the bottom of the Mavic at 77mph right under the sonar sensor. There is an outlet there where hot air is dispelled. There are 2 ports at the aft end of the Mavic that I thought were air outlets, but they are not outlets.

I turned on the Mavic with the bubble off, and clocked fan output at the bottom outlet at 77mph. I clocked the rear ducts and received no inflow or outflow at all. The internal board temperature of the Mavic after 10 minutes was 98°. The bottom cooling fins were at 110°.

I then started the Mavic with the bubble on. After 10 minutes on the desk, the internal board temps were at 98° and the output at the bottom outlet was identical to what it had been with the bubble on, 77mph, and the cooling fins were also the same temp as with the bubble off. Again, I found no in or outflow from the 2 aft ports.

My last test was folding up the Mavics 4 arms and doing an inflow/outflow test in folded position. This test led me to the same conclusion as the 2 previous tests. With the Mavic sitting folded on a table and power on for 10 minutes, the cooling fan with or without the gimbal cover was able to expel air at 77mph and not increase the internal components temperature at all. The Mavic does not sit flat on a level surface when folded, it is raised by the 4 folded arms almost an inch above the level surface. That was enough to let air get out of the bottom outlet.

In summary, flying with the bubble on will not reduce the internal temperature of your Mavic or make the fan work harder. It might distort your images, but wont have an adverse reaction to your mechanics.

In addition, updating firmware with Mavic sitting on a flat table, arms folded, and bubble on will not raise the internal component temperatures, nor will it impede airflow or place undue stress on your cooling fan. I take off the bubble anyway, but that's just me.
I think its correct. I say that by watching dji own video on the mavic. It shows it in flight with the dome in place. Why supply a cover to protect the dome in the first place. You hit on it
 
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