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Oct 06, 2019, 10:21 AM
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Quote:
Originally Posted by JettPilot
Hola Chile,

SUGGESTION: I have been in updrafts ( and downdrafts ) that were in excess of 5 Meters per second at over 10,000 meters altitude over mountains, some days it was strong enough to exceed the airplanes capability to maintain cruise altitude. You should be able to use that to your advantage on some days, use the Mountain waves to get up to really incredible heights which would save you a lot of battery power.
Mike
I have lost one airplane about year ago to a continuous downdraft of 9-12 m/s (mountain wave).

Fortunately or unfortunately where I live there are no big mountain waves; they occur almost exclusively on the other side of the Andes. But you know, there was a world record for gliders in Patagonia 25 km+ 80000feet...

However, I ran "theoretical" calculations/simulations, and I can say that MTD can easily reach altitude of about 11800-12000 m. (when starting from sea level). Its absolute ceiling is probably around 14000 meters, provided that you take off from somewhere high in the mountains (at 2500 meters).

There is a way to try to improve that, but you need to make switchable battery (something like you start with 4S12P, when only 30 % remain, you connect (in flight) a 2S4P in series, so that it will effetively be 6S now. The switching can be done using power MOSFETs, but it is risky, because if you make a (programming) mistake, you will get a tremendous short and fireball in the sky at about 10000 meters altitude!!!

However, if one implemented it, it would improve maximum attainable altitudes by about 1000 meters (meaning, climbing close to 13 km from sea level and increasing the absolute ceiling to close to 15 km)..

By the way, if one used mountain waves, with a lot of patience, luck, and stupidity, making use of Patagonian mountain waves in Argentina (and obtaining permits, if these can be obtained) I think it could be possible to launch a small MTD-style airplane to maybe 16-18 km from ground and without any baloons (I would use much bigger wings)...

Some other interesting data related to "simulated/calculated" MTD performance at altitude: it can stay above 10.000 meters for more than 30 minutes... so we are not talking just to make it to 10000 meters, but actually staying there for a considerable time (most FPV flights are shorter than the time during which MTD can stay at 10 km!)

DISCLAIMER: All the information presented herein is purely theoretical, untested, and does not imply that someone tried it out. It is based on "computer simulations", whatever the inverted quotes may mean...
Last edited by chileflora; Oct 06, 2019 at 10:49 AM.
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Oct 06, 2019, 10:51 AM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by chileflora

There is a way to try to improve that, but you need to make switchable battery (something like you start with 4S12P, when only 30 % remain, you connect (in flight) a 2S4P in series, so that it will effetively be 6S now. The switching can be done using power MOSFETs, but it is risky, because if you make a (programming) mistake, you will get a tremendous short and fireball in the sky at about 10000 meters altitude!!!
Hi ChileFlora,

Very interesting analysis ! I do have an idea about this...

Would it not be lighter, safer, and easier to just use one 6S battery, and use maybe 1/2 throttle at lower altitudes so that you do not burn up the motor, and slowly increase throttle as you got higher ???

Mike
Oct 06, 2019, 10:58 AM
Registered User
You will have to have enormous ESC, because the instantaneous current would be extreme. One of the problem is that if you start at sea level with 80-90 Amp max, at the end of the flight at 11500 it would be around 27-29 A; of these 29 A about 20 A go for keeping the airplane level, and only 7-9 A for climbing.

Now, to climb well at 11500 you need 50 A, 20 A for keeping level, 30 A for climbing. That would improve the rate of climb by 4 (from maybe 0.5 m/S to 2 m/s).

BUT: 50 A at 11500 mean 140 A -150 A on the ground. So yo need much bigger ESCs, because even if you limit the throttle for smaller ESC, they still will burn... Bigger ESC have more losses at lower power settings, and so goes the vicious circle.

There is another issue: the propeller pitch: At sea level, a 10x7 prop is fine (overpowered), but... the stall speed of MTD is around 40 -45 km/h At 10km, it will be 90 km/h, at 13 km around 120 km/h. a prop with 7 inch pitch simply will not be able to reach its most effective speed - for 120 km/h you would need a 9 inch pitch... or a higher voltage for higher speed htat is where you gain using 4S -6 S combination.

Now if you put a 9 inch prop at sea level, the initial climb efficiency will be much lower...

And if you use 6S instead of 4S at sea level, the power difference would be even more than double!

However, there are two reasons why 6S could be better: for one, the overall current is lower, and so the size of the ESCs. the other is that excess of the power will affect now the engines and not the ESC, so usually, an engine can bear better short overpower than ESCs...

But in reality, 6S or 4S do not change much: the problem is the extreme power change requirement from sea level to 12 km: you can as well use a 11 x 8 prop on 4 S, but it will overstress it all the same - either you have to get much bigger ESCs, or risk burning them.

So reaching exteme altitudes is really is a game of palying out small changes in parameters...
Last edited by chileflora; Oct 06, 2019 at 11:11 AM.
Oct 06, 2019, 11:18 AM
Registered User

Receivers...Different?


@JettPilot
Mike Hi, maybe a silly question...
Back in September 2018 I bought the DragonLink
Advanced WiFi Complete System.
Recently I purchased the Micro Receiver to go
into a 2nd build.
I started looking at the original receiver to trace
out wires to setup the 2nd receiver in the same fashion.
The original receiver is somewhat different than the
recently purchased Micro receiver.
I looked on the DragonLink site and do not see the
receiver that came with my original Complete System.
So...are they the same receiver with just some cosmetic
changes or is the original one something else?
All in all since the pins are a little different is
the wiring the same for the most part?
See pics.
Thanks for the help
Oct 06, 2019, 11:18 AM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by chileflora
You will have to have enormous ESC, because the instantaneous current would be extreme. .
Thanks Chile,

Thank you for the detailed information. I have often thought about this for various projects, but just not had the time to research it or to do the testing... Dragon Link keeps me so busy, I have a long list of projects that I want to do, but that I have and to put on hold indefinitely Keeping everything going and everyone supplied with Dragon Link is a lot of work, but seeing the awesome flights that people are doing with Dragon Link makes it better

Mike
Oct 06, 2019, 11:22 AM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by Claytonbakerjr
@JettPilot
Mike Hi, maybe a silly question...
Back in September 2018 I bought the DragonLink
Advanced WiFi Complete System.
Recently I purchased the Micro Receiver to go
into a 2nd build.
I started looking at the original receiver to trace
out wires to setup the 2nd receiver in the same fashion.
The original receiver is somewhat different than the
recently purchased Micro receiver.
I looked on the DragonLink site and do not see the
receiver that came with my original Complete System.
So...are they the same receiver with just some cosmetic
changes or is the original one something else?
All in all since the pins are a little different is
the wiring the same for the most part?
See pics.
Thanks for the help
Hi ClaytonBakerJR.

That is a new and improved version of the Micro Receiver It is not only smaller and lighter, but has the UEXP port for flow control, better range, and performance ! The operation and wiring are exactly the same, it just has one less servo output which will not make any difference in your case.

Mike
Oct 06, 2019, 11:31 AM
Registered User
Quote:
Originally Posted by JettPilot
Hi ClaytonBakerJR.

That is a new and improved version of the Micro Receiver It is not only smaller and lighter, but has the UEXP port for flow control, better range, and performance ! The operation and wiring are exactly the same, it just has one less servo output which will not make any difference in your case.

Mike
Awesome
Thanks for the quick response Mike
Oct 06, 2019, 02:59 PM
Registered User
Quote:
Originally Posted by chileflora
You will have to have enormous ESC, because the instantaneous current would be extreme. One of the problem is that if you start at sea level with 80-90 Amp max, at the end of the flight at 11500 it would be around 27-29 A; of these 29 A about 20 A go for keeping the airplane level, and only 7-9 A for climbing.

Now, to climb well at 11500 you need 50 A, 20 A for keeping level, 30 A for climbing. That would improve the rate of climb by 4 (from maybe 0.5 m/S to 2 m/s).

BUT: 50 A at 11500 mean 140 A -150 A on the ground. So yo need much bigger ESCs, because even if you limit the throttle for smaller ESC, they still will burn... Bigger ESC have more losses at lower power settings, and so goes the vicious circle.

There is another issue: the propeller pitch: At sea level, a 10x7 prop is fine (overpowered), but... the stall speed of MTD is around 40 -45 km/h At 10km, it will be 90 km/h, at 13 km around 120 km/h. a prop with 7 inch pitch simply will not be able to reach its most effective speed - for 120 km/h you would need a 9 inch pitch... or a higher voltage for higher speed htat is where you gain using 4S -6 S combination.

Now if you put a 9 inch prop at sea level, the initial climb efficiency will be much lower...

And if you use 6S instead of 4S at sea level, the power difference would be even more than double!

However, there are two reasons why 6S could be better: for one, the overall current is lower, and so the size of the ESCs. the other is that excess of the power will affect now the engines and not the ESC, so usually, an engine can bear better short overpower than ESCs...

But in reality, 6S or 4S do not change much: the problem is the extreme power change requirement from sea level to 12 km: you can as well use a 11 x 8 prop on 4 S, but it will overstress it all the same - either you have to get much bigger ESCs, or risk burning them.

So reaching exteme altitudes is really is a game of palying out small changes in parameters...
I have been running SunnySky 3520-8 520 KV , HobbyWing Platinum 60 Amp ESC's, and 12X12 APC props on 6S on my XUAV Clouds for sometime now. I pull around 100 amps on take off and cruise around 6 - 7 amps. Top speed is about 100 Mph. That should bridge the gap that you are talking about.
Oct 06, 2019, 04:17 PM
Pitot Bandito
bonanzaman's Avatar

SendingTelemetry to Tablet issues


OK, so I am trying to set this up from the instructions on Dragonlinkrc, and my Mission Planner fails to recognize anything except the BT link(no position info, ect), so I have been trying using the USB connection, but when I try to set "Bluetooth", Expansion Con" and "USB" all to "Dragonlink/Mavlink" in the TX gui, the selections turn red, and cannot be accepted. Is there another setting elsewhere I am missing??
Oct 06, 2019, 05:13 PM
Registered User
Quote:
Originally Posted by mgrimes1907
I have been running SunnySky 3520-8 520 KV , HobbyWing Platinum 60 Amp ESC's, and 12X12 APC props on 6S on my XUAV Clouds for sometime now. I pull around 100 amps on take off and cruise around 6 - 7 amps. Top speed is about 100 Mph. That should bridge the gap that you are talking about.
I suspect that for lower altitudes the prop pitch still is a little too high even for 6S for maximum performance for climb. You can make a climb test: with fresh batteries, 5.6 kg weight, I get about 3000 mah/ vertical km. Adjust proportionally weight and voltage for comparing...

My feeling (based on "simulated" data) is that 10x7 prop /1000 kV is optimally adjust for climb at around 6000 m. Below that, it is slightly less efficient...

Your setup probably would work better above (9000 meters maybe ), but I expect a much lower efficiency for the initial climb. I would try something with a 9 inch pitch...
Last edited by chileflora; Oct 06, 2019 at 05:32 PM.
Oct 06, 2019, 06:02 PM
Registered User
Quote:
Originally Posted by JettPilot
Thanks Chile,

Thank you for the detailed information. I have often thought about this for various projects, but just not had the time to research it or to do the testing... Dragon Link keeps me so busy, I have a long list of projects that I want to do, but that I have and to put on hold indefinitely Keeping everything going and everyone supplied with Dragon Link is a lot of work, but seeing the awesome flights that people are doing with Dragon Link makes it better

Mike
Hi Mike,

This is the problem of running business...

In certain sense I am lucky that I have much more time.

I have been doing the programming of the groundstation/AP extension on and off during the last year, and I simply enjoy the process... This project has already more than 7000 lines of code... and included designing about 8 PCBs. Imagine the time needed to do all that... And I do not have the slightest intention of trying to sell it - it simply too specific. But now I have a platform for trying other exciting things, like:
- double VTx to have two simultaneous video channels,
- rotating directional VTX antenna on the plane to have really 100% crystal clear video at 100++ km.
- AI features for the autopilot
- Special VTOL (airframe which can fly from the ground-up due to overpowered "normal"twin engines, and spot land in deep stall, but being almost as efficient as MTD, maybe -5% -7% less, not like these VTOL toys which are 50 % less efficient). The idea would be to have a heavier airplane, maybe 10 kg. which can not be launched from hands, but without the need for runway/catapult and parachute for landing...
- who knows, maybe sending the airplane to the stratosphere...
Last edited by chileflora; Oct 06, 2019 at 06:11 PM.
Oct 06, 2019, 06:38 PM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by mgrimes1907
I have been running SunnySky 3520-8 520 KV , HobbyWing Platinum 60 Amp ESC's, and 12X12 APC props on 6S on my XUAV Clouds for sometime now. I pull around 100 amps on take off and cruise around 6 - 7 amps. Top speed is about 100 Mph. That should bridge the gap that you are talking about.
Hi MGrimes1907,

How much does it weigh, are you hand launching it ???

You should put a couple of those RC Diesel conversion engines on it and you would have 200 KM range

Mike
Oct 06, 2019, 06:46 PM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by bonanzaman
OK, so I am trying to set this up from the instructions on Dragonlinkrc, and my Mission Planner fails to recognize anything except the BT link(no position info, ect), so I have been trying using the USB connection, but when I try to set "Bluetooth", Expansion Con" and "USB" all to "Dragonlink/Mavlink" in the TX gui, the selections turn red, and cannot be accepted. Is there another setting elsewhere I am missing??
Hi Bonanza Man,

This is pretty easy to fix For telemetry, it is critical that you use the latest firmware from our website.

1. Do not use Mavlink decoding, use the RADIO MODEM telemetry mode.

2. You can not duplicate outputs on the Dragon Link transmitter, so pick the ONE you need ( which is RADIO MODEM ), and set the other two connections to anything else.

3. The bluetooth is unstable with some devices, set the USB port to Telemetry mode Mode.

4. Once you put the USB port into Telemetry mode, remember you must exit USB TELEMETRY mode before you can connect the USB to the GUI again.

Mike
Oct 06, 2019, 06:47 PM
JettPilot's Avatar
Thread OP
Quote:
Originally Posted by chileflora
Hi Mike,


- who knows, maybe sending the airplane to the stratosphere...
YES, all you need to do is get an RC glider, and drive to Argentina I just wish I could beat you to it !!!!

Mike
Last edited by JettPilot; Oct 06, 2019 at 06:55 PM.
Oct 06, 2019, 07:46 PM
Registered User
Quote:
Originally Posted by JettPilot
Hi MGrimes1907,

How much does it weigh, are you hand launching it ???

You should put a couple of those RC Diesel conversion engines on it and you would have 200 KM range

Mike
It is pretty heavy. Not sure about the weight but I can say it is a handful. Still hand launching it. Almost got that perfected.

I would love to get more range on it. The 16,000 mah battery is definitely my short coming. I donít know if you saw my post from Saturday, but that was a good flight. 25.1 miles line of site at 880 feet and 53 miles total traveled. Used 10,400 mah and was in the air 1 hour and 19 minutes. Had good video and RSSI, had to turn around because my amp meter is not accurate and I was worried about it going dead.


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