Custom Power Train - TMotor P80, 80A ESC, 26", 12S

Power System
1

New to PG and PPG, but planning on getting my cert coming Sept/Oct. I come from the drone industry (I design, fabricate, test a wide range of custom drone technologies) and looking to apply that to a custom power train for a PPG system.

Have done a decent amount of research at this point, though it seems relatively limited when it comes to electric, everyone runs gas (gross!) There are some single electric motor systems out there, but $$$$$$$. Then I came across the OpenPPG project and was instantly in love with the design and method.

I will probably design and fabricate my own carbon and accessories (looks like I wouldnā€™t be able to get an OpenPPG setup until Batch 4 anyways, whenever that would be?) Power train is where Iā€™m looking for input. Sanity checks are good from experienced pilots. I donā€™t usually strap myself to my creations.

Currently specā€™d it out based on a TMotor power train.

  1. Motor: P80 170kV http://store-en.tmotor.com/goods.php?id=424
  2. ESC: Alpha 80A HV ALPHA 80A 12S_ALPHA Series_ESC_Multirotor_T-MOTOR Store-Official Store for T-motor drone motor,ESC,Propeller
  3. Prop: 26x7.8 2 blade (Would post a link but only allowed 2 as a new user :slight_smile: )
  4. Battery: Bonka 6S 22Ah (on OPPG website)

@12S2P itā€™d be pushing ~60kg thrust @ ~220A WOT. Compared to a similar specā€™d gas setup (Black Hawk 100cc), which pushes ~55kg (I weigh about 170lbs after a trip to the bathroom).

@WOT (220A), the 44Ah lipo would give about 10 minutes flight time (considering 80% rule). I assume this only be required at launch or climbing, and would guess cruise would be about 50% throttle? This would give about 20kg thrust @40A. About 53 minutes of flight. Seems like most are getting closer to 25 minutes flight time, which between launch and climb and cruise, seems reasonable.

Black Hawk weighs about 22kg (before fuel I assume). The above setup, about 15kg (no harness, no frame). So on spec there.

This would run about $2600USD (Iā€™m hoping I can get some discounts since I deal with TMotor, also a Canuck and the conversion will hurt at the moment), which is way cheaper than any RTF electric or gas setup. Add harness, frame, accessories, wing, shouldnā€™t require me to eat noodles for months.

Also planning on getting a wing I can PG or PPG with, not looking to do acro (yet!).

Thoughts?

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Thereā€™s a few things about this post that got my attention.

In the future I believe were going to be seeing people playing around with their battery voltages, motor kV and props to fine tune all the efficiency out of their system that they can.

I saw a Y.T a few months back where a couple of local Melbourne Drone Racers went to the T-Motor factory. In the video they indicated that T-motor were open to ideas / mods / further development of their products. My first thought was ā€˜custom propsā€™. You know the quiet ones with winglets on the ends.
Then started dreaming of sine wave ESCā€™s with data logging - how useful would that be? Custom motor winds, battery configā€™sā€¦Mmmm- Then I woke up

Anyway. You mentioned that you deal with T-motor. Show them this project. See what input they have. Would they be willing to supply custom parts for us to experiment with?

Also, max prop size for this frame is 22-23" yeah? guysā€¦

Welcome to the discussion.

And hereā€™s a link to the vid I was referencing; FPV Drone Motor Manufacturing at T-Motor - YouTube

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T-motors are great, Iā€™ve been working with them too in the past and theyā€™ve always been really open and helpful.

Few questions/thoughts:
-Why are you going with the 170kV version. I would have thought the 120 or even the 100kV would have been more adapted to an heavy loadā€¦ Current motors are 180kV but theyā€™re designed for 22" props.

-Prop size recommended for those P80 is 28-30", a 26" prop would probably work but will most likely result in a considerable lost of thrust.
Also like Lukas mentioned the frame is now designed for 22-23" prop.

Edit: 23" is pretty much the biggest props you can go with now.

4

TMotor can and will do custom windings of motors to make specific KV motors. They donā€™t make their own props, and the company that does requires a very large order to make custom designs. If you go with TMotorā€™s alpha escs, you can get their Data link which allows you to change esc settings, log data, and more.

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Hey @MayMayDay, Are you still working on it? Iā€™m also from the drone industry and gimbals (Iā€™m CEO at www.slick.video) and want to build a PPG. Want to get in touch?

Tom

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Havenā€™t had much time to do design work yet unfortunately (been overseas for the past month for work), though Iā€™ve been brainstorming a lot. Aiming to go bigger prop (29-30") and get efficiency up with custom motors and ESCs. Newer high density lipos for more bang for your buck. Itā€™s a slow going process but itā€™ll get thereā€¦

I want 30min to be standard for 4 packs, if not more.

Want to stick a gimbal on it? :stuck_out_tongue:

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Time. It slips by.

29" prop setup is currently in the works. Got the entire power system ready to rock, finishing frame design. (FYI power system is not the above stuff, been heavily modified from there. Theoretical 1 hour flight times, but theory is a fickle beast.)

Funnily enough Iā€™ve never flown paramotor. Iā€™m almost a P3 paraglider at this point, but never had the opportunity to learn a paramotor setup. So I have a question for those that do fly:

How important is it that your swing arms can pivot down? I assume itā€™s just for ease of getting into / out of, because once in flight, theyā€™re not going to move. It allows my design to be stronger if they donā€™t have to pivot. Yay/nay?

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The gooseneck bars do pivot during flight to allow weight shift. Probably best to fly a paramotor before designing your own so you donā€™t make any assumptions. :slight_smile:

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Hopefully going to get a flight or three next weekend, though on a gas setup.

Can you unload a swing arm enough for it to pivot? The only time Iā€™ve had a carabiner go loose (ie enough for an arm to swing down) is during an asym. Between your weight, the paramotor weight, and wing loading, Iā€™d expect them to always be locked up. Anyways, I shall find out for myself soon.

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You donā€™t have to do acro to make the arms move. You donā€™t have to unload the carabiners to move the arms. Press down with one leg and lift up with the otherā€¦ thatā€™s all it takes. Itā€™s just like weight shifting a normal harness except the hookups are a little higher so you canā€™t get as much movement. In a way the bars are an extension of the harness and float with the seat board.

2 Likes
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Well said glider pilot

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Went for my first paramotor flight over the weekend, and now I understand. Lots of things make more sense now, including why I want to go electric. :smiley:

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Glad it went well!
Iā€™m curious to hear your initial impressions of flying with a motor coming from a paragliding background

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Hi Guys,
I come from a drone background too. Woohoo!
Recently I have been testing coaxial 36" prop setups for our large custom builds.

The open ppg project looks really cool. Quite similar to the big drone stuff.

Perhaps something like this may workā€¦
I know from testing that you can get around 17g/w of efficiency with the sub 5kg thrust motors. Unfortunately I havenā€™t found any 10kg motor with anything near that. The best I can see is the T Motor U8II. Max thrust is 7kg thoā€¦

For some reason efficiency of the motors drop right off between 100kv and 90kv (or 85). Unfortunately the grams of thrust per watt go to shit. I donā€™t know why, perhaps someone else does?

Anyway if you go KDE /T Motor, 60kg for coaxial octacopter letā€™s you have slow fly props and at a guess probably around 10 g/w during cruise. I donā€™t know the flight profile for PPGs really but put on a nice VTol prop and youā€™ll be laughing :slight_smile:

Couple this with a custom made 18650 Li-ion pack and I think youā€™d have a nice system.

Although 8 x 29" props might be a bit cumbersome to handleā€¦

Anyway sounds like a cool project. Iā€™m keen to get involved it looks super cool!!!

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hi, what does 17 g / w mean? or 10g / w cruise? I know a lot of drone from volocopter, ehang, agronator, etc. the values tell me, however, nothing? your question about low kv and loss of efficiency. This only happens if the number of poles and torques is not in good shape. Thatā€™s why all the efficiency projects need the right motor for the project. Do not use a serial standard motor from another application. that does not work successfully. in principle, the motor manufacturer has several options to fit the system by windings numbers, stator height, etc. only if the project is calculated completely wrong brings nothing synonymous.

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Thatā€™s the thrust in grams per watt of energy.
I know for forward flight you need a higher pitch as the angle of attack is reduced with incoming airflow.
The 22x10 inch props rotating at 3000rpm+ seems like they are designed for max thrust, amongst other reasons. Still could flight time be increased using larger diamitet, lower pitch, lower rpmā€¦

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that means 17 times 1000 = 17 kg thrust. and 1 watt times 1000 = 1 kilowatt = 17 kilo thrust with 1 kilowatt of power? In short, the propellers have a threefold performance than anything on the world so far, practically 150% efficiency? how does it work? can you show the project?

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I have a magcad propeller that works in low speed / pitchspeed. at 42 inches. It is a watt / gram size up to 1: 6.5 possible with good air tightness and temperature and humidity. 1: 17 I can not do. https://magcad.de/ the Motor is used has a eta of 93 % on the prop hub.

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http://store-en.tmotor.com/mobile/goods.php?id=325

Thatā€™s just manufacturer data but Iā€™ve tested some prop/motor combinations and the data shows that they indeed output around that stated efficiency .

Drone thrust is ā€œusuallyā€ from static air so V-infinity is essentially 0. I am yet to real word test these motors but I assume itā€™s around 14g/w

20

How slow is ā€œslowā€?
26" 50% throttle for hover is 1200rpm.
Up to 19g/w