Heavy AP rig and low headspeed

[TheAdventuresofKarl]

Hey guys,

I'm looking at building a heli from the ground up around a stretched 700 series T-Rex. I already have a 700L Dominator Top (without electronics) purchased and am about to buy the stretch kit to take it to an 800 size.

I was wondering if anyone can help me decide on a motor and battery/gearing combination. The goal is ultimate endurance for commercial inspection and monitoring for which I'd ideally like to reach 45-60 minutes flight time. With all the weight of the equipment, I'm looking at around 5.8-6.0kg without batteries. With batteries - depending on which ones - I'm looking at around 3.0-6.0kg on top of this, which to me seems seriously heavy!

I have a bunch of different battery options I'm looking at from Gens Ace Tattu and some 14S options from Pulse. However I don't have the luxury to experiment with different battery and motor combos to find the best for my scenario at the price they are!

What would you recommend for such a setup?

I planned on the following:
- 800mm asymmetric blades
- KDE 295Kv (12S-14S)
- Low headspeed
- Kontronik 160HV (active-freewheeling)
- 800 stretch with 3-blade tail

I even considered a 3-blade main rotor to improve weigh-lifting performance however I believe this would increase amp draw quite a bit, but I figured a 295Kv should have gobs of torque to handle the increased drag without breaking a sweat.

What would you recommend? Quality is something I do not want to compromise on, so I will be building it using the best you can recommend. The work will mostly be long distance, remote access stuff with top-quality equipment to compete with multirotors (ew ) So I would really like to push for that 45 minute mark.

I've added the battery options and All-Up-Weight (AUW) of the heli + batteries I was looking at - with a 12S or 14S setup I doubt I'll get my headspeeds that low, even on a 295Kv motor but whatever gets me the lowest amp draw and longest flight time would make me incredibly happy!

Gens Ace Tattu
12S 10,000mAh (2x 6S 10,000mAh) = 2,800g total / AUW 8,800g
12S 16,000mAh (2x 6S 16,000mAh) = 4,000g total / AUW 10,000g
12S 22,000mAh (2x 6S 22,000mAh) = 5,000g total / AUW 11,000g

Pulse Batteries
14S2P 10,000mAh (2x 14S 5,000mAh)= 3,600g / AUW 9,600g
14S3P 15,000mAh (3x 14S 5,000mAh) = 5,400g / AUW 11,400g

Your help would really be appreciated!
Thanks guys

[Keyrigger]

If you have the 110t main and the standard 13t pinion, you will be able to get low rpms from either setup with the 295kv motor. I calculated that with the 12s at 92.5% governed with the 12s, you will get 1289rpm and with the 14s setup, you will get 1504rpm. If you use raw numbers, your rpm will be higher but for best flight optimization, 92% or thereabouts, seems to be the best setting. As an example, I run an MD7 with the 295kv KDE motor at 1200rpm (high rpm setting) for about 11 minutes on a 12s 5000 pack and it comes down at 3.8v per cell or around 50% capacity left. I do not do 3D but do the occasional loop, tail slide, or inverted hover, only. This setup is 15lbs. all up flying weight so this is not a light helicopter by any stretch of the imagination.

Remember that after any given point, battery capacity will no longer give you duration as it will take so much power to lift those packs that you will start to reduce the flight time. If you are planning on a 1400rpm range, that is easy to get with the 14s setup. You may find that the extra torque created by the three blade head will require a three blade tail or 120mm tail blades (or longer) on a two blade tail setup to counter it. With a two blade setup of 710mm Rotor Techs at 1200, I am using 115mm Zeals on tri-blade tail and they counter the torque very well. Good luck and hope this helps.

Don

[TheAdventuresofKarl]

Hi Don,

Thanks for your detailed response! I'm glad to finally talk to someone who runs a KDE 295!

Yes, I believe those are the ratios I have out of the box. I'll give 12S a shot then as it seems the best option for starting out. I'll pick up some 10,000mAh batteries and test some dummy loads on it to see what amp draw I get, simulating the equipment and what a larger battery might do to the flight times.

I was somewhat concerned that such a low headspeed would lack enough lift for all that weight, but if yours is almost 7kg and almost the same weight with batteries, I'm sure with a 3 blade main and slightly higher RPM I'll be able to get it there. I'll definitely be looking at a 3 blade tail though, I read some threads on people who stretched their 700s and they recommended that too.

Thanks again for your help, I'll post a build thread once I begin soon!

Karl

[amphibia]

I stretched both my JR E12 and forza700 to 800size with align 800 torque tube and a few custom parts. I learned a few things. Here is the JR E12 post
for example. At 5.2kg take-off weight, it consumes about 6s6500mah energy every 20-25minutes. That translates to about 400-500watt power.
https://www.helifreak.com/showthread.php?t=766455

1. please make sure you get the NEW align 800 torque tube.
See here
https://www.helifreak.com/showthread.php?t=767840

2. You cannot go wrong with kontronik. But you will be surprised that a 10kg low rpm machine running 12s does not need the 160A rating kosmik. A jive 120HV will be more than enough. But better be safe than sorry. Add a heatsink and glue it with arctic silver thermal adhesive. I use it on all my jive ESCs.
http://www.arcticsilver.com/arctic_s...l_adhesive.htm

3. Since I imagine you will carry some very heavy and expensive gears, I strongly suggest you get the reliable futaba BLS 172 or 177 for cyclic and BLS276 for tail. You can power them with 2s LiPo directly. No ESC is absolutely safe. For my 5.2kg low rpm E12 during sports flights, every 20minutes of flight consumes about 300mAH of capacity. So a 2s3300mAH lipo should probably keep your machine in the air for more than 60minutes with a safety margin of more than 3x.

4. futaba sbus system (futaba 14sg/18sz + R7008SB receiver) is most likely the best system to resist interference with many telemetry capabilities. I suggest you connect channel 3 on r7008sb to your ESC directly without going through your gyro unit if you decide to go FBL.

5. Make sure all your critical bolts are properly tightened with loctite 243 or equivalent. All critical bolts should be replaced during maintenance or disassembly.

6. If this machine falls from the sky for any reason and hits animals/people, it will kill them. So are you sure you know what you are doing?

[TheAdventuresofKarl]

Thanks for the link to your build thread, Amphibia, it was an interesting read and it looks great with the blue canopy Your amp draw is awesome, I'm aiming for something similar, but as you can imagine the weight will make this a challenge.

1. please make sure you get the NEW align 800 torque tube.
See here
https://www.helifreak.com/showthread.php?t=767840
Thank you, that is the one I intended on getting - H80001A I believe the kit part number is

2. You cannot go wrong with kontronik. But you will be surprised that a 10kg low rpm machine running 12s does not need the 160A rating kosmik. A jive 120HV will be more than enough. But better be safe than sorry. Add a heatsink and glue it with arctic silver thermal adhesive. I use it on all my jive ESCs.
http://www.arcticsilver.com/arctic_s...l_adhesive.htm
Yes I very much doubt I'll drawing anywhere near enough to 160 amps haha, I mainly was looking at the Kosmik as it has a self-contained case which I can easily mount solidly when compared to the Jive, but this is not a major - if my budget doesn't stretch to the Kosmik, I'll go with the Jive

3. Since I imagine you will carry some very heavy and expensive gears, I strongly suggest you get the reliable futaba BLS 172 or 177 for cyclic and BLS276 for tail. You can power them with 2s LiPo directly. No ESC is absolutely safe. For my 5.2kg low rpm E12 during sports flights, every 20minutes of flight consumes about 300mAH of capacity. So a 2s3300mAH lipo should probably keep your machine in the air for more than 60minutes with a safety margin of more than 3x.
That is also what I had in mind. I'm going with Futaba servos and a separate battery to control them and other equipment. I don't like the idea of my flight controls relying on a BEC and the same battery the motor is drawing on. Thank you for the information on amp draw on the servos, that is something I still needed to get a figure on until now

4. futaba sbus system (futaba 14sg/18sz + R7008SB receiver) is most likely the best system to resist interference with many telemetry capabilities. I suggest you connect channel 3 on r7008sb to your ESC directly without going through your gyro unit if you decide to go FBL.
I did plan on the Futaba S.Bus, but due to needing video links I will probably be using a DJI Lightbridge 2 link for video and gimbal control which uses the 2.4GHz band, so flight controls will be on 900MHz via a DJI Datalink Pro 900 which is supposedly highly EMI resistant or RFD 900X controlled via Mission Planner and a joystick for manual control. There will be some slight lag I'm expecting on the RFD900X, but the flights will be automated for the most part and flight should be slow and smooth enough that this slight lag will not make a critical difference, however I'll be testing this further. If it comes to it, I have no issues using the 900 band just for autopilot control, a 2.4 Futaba for flight control and 5.8 for video - range will just drop quite a bit

5. Make sure all your critical bolts are properly tightened with loctite 243 or equivalent. All critical bolts should be replaced during maintenance or disassembly.
Will do, my thoughts exactly

6. If this machine falls from the sky for any reason and hits animals/people, it will kill them. So are you sure you know what you are doing?
This is my first time going into aerial work, however I can say with confidence that safety is something I won't be compromising on in any way. I have seen people with el cheapo servos, questionable flight controllers and disregard for regulations, slap on a gimbal and go fly over a city skyline. This is absolutely not how I intend to do things. I'll be building this with the best components I can manage and following best practices to a tee including servicing and designing the heli to be as reliable as possible. I specifically am looking at the Pixhawk 2 due to triple-redundancy. I would have gone with a Micropilot 2128, but it is a much, much, much more expensive controller.

Our regulations on flying envelopes and permissions are quite stringent here. You cannot fly above any person (even if it's a public place) or property, streets etc. without permission from the person/s themselves, council, owners etc. Since the work is commercial and mostly remote-area inspection, the chance of this is low. I will still have failsafes, and put a lot of practice behind my unit before I go present myself as a service provider. Not only would it be dangerous, but with my specialisation being in marketing - a terrible idea for a company image haha. I've been looking at parachutes, and need to see whether I can get one fitted if my weight allows. The requirements on any work to be legal BVLOS would fill a folder quite quickly haha - you need to be CAA certified beyond the standard requirements and prove your equipment reliable with proper measures in place to manage the risk so there is no chance of being a cowboy operator haha.

Karl

[nightflyr]

I understand your requirements.
But you need to look at some realities...
Take the worse case:
A 700 stretch electric, 12Kg machine with a flight window of 45-60 minutes may not be feasible.

I've tinkered with long endurance flight ..


There is a fine line you need to walk.
But even that may well not be enough.

The.first rule:
Get the weight down as low as possible.
As to freewheeling ESC's.
Never used one, I've always set my Castles up to run @ 100% output.
First through gearing, then by voltage going from 12S to 6S.

It's a trial and error game according to your setup

I managed a few heavy lift machines:






BTW, you do not need much head speed for stable flight.

1000E maiden (4 min 29 sec)

I do nicely just under 800rpm.

As to lift capabilities....
Slinging a 13.65Kg (28 lb) lead weight for a total AUW of 19.1 Kg (42lbs)
@1000 HS

But for your flight time requirements
I might consider a gasser rather than electric.

One other consideration is your camera equipment.
Be it stills, video.... quality of the output needs to be considered.

I personally use raw footage straight out of the camera, don't use post production software.

GOPR0 Clean Raw Footage (6 min 33 sec)

[Wargamer]

There are one or two guys who've gotten flight times in the 45+ min range on electric, but I don't think they were doing heavy lift!

[Koopyetz]

Originally Posted by nightflyr

I understand your requirements.
But you need to look at some realities...
Take the worse case:
A 700 stretch electric, 12Kg machine with a flight window of 45-60 minutes may not be feasible.

I've tinkered with long endurance flight ..


There is a fine line you need to walk.
But even that may well not be enough.

The.first rule:
Get the weight down as low as possible.
As to freewheeling ESC's.
Never used one, I've always set my Castles up to run @ 100% output.
First through gearing, then by voltage going from 12S to 6S.

It's a trial and error game according to your setup

I managed a few heavy lift machines:






BTW, you do not need much head speed for stable flight.

1000E maiden - YouTube

I do nicely just under 800rpm.

As to lift capabilities....
Slinging a 13.65Kg (28 lb) lead weight for a total AUW of 19.1 Kg (42lbs)
@1000 HS

But for your flight time requirements
I might consider a gasser rather than electric.

One other consideration is your camera equipment.
Be it stills, video.... quality of the output needs to be considered.

I personally use raw footage straight out of the camera, don't use post production software.

GOPR0 Clean Raw Footage - YouTube

Nightflyr

Which GOPRO model do you use .
Thanks

[nightflyr]

Hero 3 that's mounted.

[Koopyetz]

Originally Posted by nightflyr

Hero 3 that's mounted.

Thank you Sir.

[Mapoff]

I commented in the asap section for your same question. I'm getting 16 minutes with a large camera. Id say it's actual heavy lift. My GH2 gives me about 18 minutes.

Check out the website in my signature to see a picture of the rig on the homepage and a demo reel below that.

That's 10,000ah, 800mx (440kv), 112/11t, 12s