Low-cost DIY e-ppg

Hello everyone.
First of all thank you all for this forum. I’ve been reading your posts for few months now and there are some gold informations here.
I intend to build and fly my own e-ppg, and am trying to keep in mind low-costs (and low thruts) options to motorize my Miniplane frame :

First option, based on the X4, cheaper : 4 Hobbywing’s X6 arms at 150$/piece (they include motors, folding props and ESC), each powered by its own 12S battery (either homemade 12S4P Li-ion batteries or 6S Bonkas connected in series). Each motor is rated for 11kg therefore a total of 44kg (97 lbs). Based on numbers given on an another post, 12S4P made of Samsung 40T should provide me ~30min flight time (at ~700€/$ total for the 4 batteries).
Hobbywing confirmed me by mail that these arms can run at 13S, therefore providing each 13.7kg according to my calculation (x4 = 55kg, or 121lbs) at 65A per motor. Flight time should be more or less the same as for the 12S batteries (+3min).

Second option, based on the SP140, a little pricier : A single MAD M30 100KV (830€/$ with taxes), paired with a 40x13.1 prop (350$/€). This combo is stated by MAD to provide 45kg of static thrust. As such motor is rated for 236A max, some options seems doable for the ESC :

  • MAD 300A 14S (800$)
  • APD HV 14S, rated for 240A continuous (800$).
  • Turnigy dlux 250A HV 14s (300$)
    Battery wise, Li-ion cells on a 14S configurations, or 4 7S Bonkas (similar prices compared to the ones above). I should expect a bit more flight time with a single prop configuration (+20%ish ?)

What do you think of such options ? May such low thrust be a problem for me ? (70kg/155lbs). I usually try to stick with KISS, but in this case I’m not sure to each one the acronym could correspond to.
I understand tight budget and reliable aircrafts don’t usually mix, but I’d think you might have good ideas on this. :slight_smile:

Hi, basically you will be able to fly with both variants if the wing is relatively large in relation to the total weight, such as when flying from a mountain. However, the technical efficiency of both systems is only good for ultra-light applications such as rc model flights or unmanned copters because the motor speeds are too high for long range eppg . there is nothing wrong with trying it as an attempt to gain experience with eppg in general . :slight_smile:

Hi, I am… was trying to go the same low cost route myself because…well because in the rightness of this world, if you’re from certain parts of it, doesn’t matter how passionate you are, if you don’t have lots of money you will only fly paper planes.
So in order to follow your dreams, that were given not chosen, you end up flipping things until they’re prices start looking less ridiculous.
That being said, I’m no expert so can only share what I’ve read lately and what I’ve learned in 20 years of flying rc airplanes.
I’m 68kg so I thought from the start that I might take advantage of that and not need the MAD M50 with 90kg thrust! I looked for lightweight frames in Europe, where I’m from, and found only the titanium one from Simplify at about 1150 euro, not that cheap, and the magnesium one from Air conception at 1500 euro! But found out from Miroslav from Scout paramotors and his paramotor geometry youtube series that a straight back frame is unadvised because if it doesn’t have that bump on your lower back, the thrust angle will be to downside in flight so the simplify (is too simple :grinning: and drops) and that the magnesium can crack and is hard or almost impossible to repair…at least locally.
So…another thought was to buy a used gas paramotor frame and this might have been the lowest cost version. But since I wanted the MAD M50 34kv like on the Sp140, so at least I’d have the engine of what big boys do :sunglasses: my only option was the SP140 frame because it has a large enough prop cage to fit an 140 cm prop. Then I saw Miroslav’s level flight power need formula H=WxS/V H-horizontal flight, W-weight, S-Sink rate, V-velocity(m/s). So in my case 16,5kg. Let’s say 20kg because I have an EN-A beginner 26m2 glider. So if I need 20-25kg thrust for level at 3,6kw like Paul had in his video and let’s say 35-40kg for 1ms climb, where does the 90 kg thrust come in handy for a 68kg pilot? In the 5 sec to see how it feels…that’s it :slight_smile: But I was stiiilll after the M50 just because it looks sooo good :smiling_face_with_three_hearts: That is until I’ve eagerly and full of hope contacted MAD from Poland and discover to my despair that the 1120 euro the motor and 1170 euro 300A ESC, the prices were without VAT, go figure. The VAT alone 530 euro it’s a medium monthly salary here. In the end they come at the modest price of 2800 euro! :face_with_spiral_eyes:
I have to say that after many ears of using 100A - 60$ esc’s from Hobby King without a single problem, It’s a mystery to me how a 200-300 esc is 10 or 20 times the price, having no brake and being capable of destroying themselves in a millisecond for no other logical reason other than bad luck just like any other one.
So…after deciding to go that route in spite of resembling like a soft madness to me (not to mention if I will be asked by others), your post made me rethink (only to end up with the same options in the end I’m sure).
The multi engine eppg from what I understand is inefficient. And the batteries being where they are, even 5 min +/- matters. And this is where I can relate to my rc models. If I take a 1,5kw 430kv 17 inch prop motor that gives about 4kg of static thrust by comparison the MAD M50 34kv at 1,5kw input generates 15kg thrust in their test with the 63inch prop. Maybe some 12kg with the 140 prop in eppg case but still…three times! This brings me to the M30 motor that has an 45kg attractive thrust at first sight. Then if you look closer there are at least to concerning things: 1. At 3,6 - 4 kw needed for level flight for a 70kg pilot you get into the short term operation already… And 2. The short term operation…it’s REALY short!! 10-30sec c’mon!..not 3-5 min as I would have thought. And the M40 has the price near the M50…
It seems to me that these ‘‘high tech’’ motors and technologies are more marketing than facts. I mean, we’re at the middle of what the motor is stated for and we should use it only for 15 sec.or it will burn out!
What a wacum cleaner advertisement would sound following the same concept: ‘‘It has an powerful 1800w motor but working at 100% you can use it for 15 seconds’’ :rofl:
The same for these 13kw (MAD 30) and 20 kw (MAD 50) motors. They are 13-20 kw but after 3 and 6 kw, you should use them for 15 sec :neutral_face:
Otherwise if they would be as stated, like the MAD 30 and hold 7-8kw (75% throttle 30-34 kg) for 5 minutes and get a 1m/sec climb without the motor getting hot, an 250$ esc from hobby king and would not think further.

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a simple reference without typing on brands. an esc that can be used for man-carrying can already be recognized if you take a closer look at the connection cable or the ports diameter etc… as well as the cross-sections on the board of the mosfets. if it is designed for rc models or unmanned copters, the esc is relatively cheap to manufacture and a mass product that is on the market, regardless of whether it lasts a long time or fails earlier. an esc for man-carrying is a completely different class and is built and tested according to industry standards. the components are partly opposite rc. another quality class. If you want absolute safety when flying, this is impossible with rc material because rc never has the parameters in the esc that you need for aviation. aviation is much more complex overall. However, this is not difficult to use, but even easier because you don’t need any experiments that can lead to total failure as with rc material.

That is exactly the kind of headache I had with comparing manufacturer’s data sheets…
According to M30’s specs, I should not even expect that kind of power during a continuions use, but something more like 4kW (21kg / 46lbs). Same goes for some others motors (Rotomax 150, Freerchobby ones…).
A 8kW continuous (35kg/77lbs thrust) rating would have been enough I guess (as some pilots seems to enjoy such thrusts on their DLE170, like the one on the Minimot by RBparamotors).

In the end, cooling seems to be the major problem here. Maybe should I consider other manufacturers, that offer motors with a liquid cooling options. For example, both RV-120Esm and RV-120Em seems to fit these power rating. They’re not that pricey too (700$ish), but they come at an hefty weight (respectively 4,8kg/10lbs and 6,3kg/14lbs). It seems that they were designed for small EVs, and can be sold with interesting KV options (that could enable the use of larger and more efficient propeller). I need to make further investigations on them.

As for the X4-alike idea, there are plenty of motorization option :

  • As stated above, Hobbywing X6 arms. By far the cheapest option (150$/p that includes motor, motor mount, ESC and foldable prop). Reviews on them are hard to find though, but they seem to work well on some agricultural drones.
  • T-motor’s V605 (150$/p.). Additional ESC need to be taken into account ; T-motor’s AT 115A 14S (110$/p.) seems to be the best one as they have an included BEC). X4’props could be use with them.
  • MAD’s M10 (the one used on X4). Pricier (300$/p.), but offer the advantage of a rather positive feedback from X4 users. Again, ESC and props needs to be purchase separately.

At that kind of price I guess I could offer to buy a motor of one of the three options above, and test it. If thrust, temperature, and efficiency don’t reach my expectation I could move on without spending all I could afford on this project.

There is also an other architecture that seems to work with others : the dual motors.
Minnie sell one, and Justine Haupt made a strange one based on two T-Motor U13 attached to a long pole. If I go with such idea I would keep a more traditional architecture though (motor attached to a frame, aligned vertically), in order to prevent any twisting scenarios.

Nevertheless, i am not 100% confident on such design. Avery Flies made some videos few month ago about building one. As he never published again on this, I am not sure how I should interpret that concerning the viability of such eppg.

Thanks ! I’ll try to investigate further on that. I plan to use my hike&fly wing (a Dudek V-King ES). At 18 squared meters (monosurfaced ^^') it isn’t the best wing in term of efficiency, but it still offers me what seems to be a comparable glide ratio to other B- ones.
In the future I’ll test in calm conditions the wing with my motor-less frame (with weights attached), to try to find if the 1.2 m/s stated by Dudek is relevant or not. Then it will help me reconsider thrust.

hi, yes i know the dudek v king from test flights. unfortunately absolutely not comparable with modern enB wings like advance, nova, ozone etc. but a nice hike and fly wing as it is very light and easy. the revolt motors can be used, for example, for simple go-karts etc. I would not use 14 pole motors for flying. (I myself have 2 revolt motors in the large DIY e lawn mower and in the motor boat.

bratwurst, what would be your personal approach towards an modest, budget limited motor-esc combo max 40-50kg capable for a lightweight pilot?

in which country. United States, Europe? it is important because the customs and taxes matter a lot. in the usa there is currently only the openppg setup as with the sp 140, which makes sense because the high voltage there is no problem from the set, as I often read. for light pilots, a 130 cm (better, of course, 3 blade 140 cm) and a 3 kw/h battery is enough to enjoy it for a long time. in europe there are motors and escs from Rotex, MGM, Geiger, Hacker Industrial, all of which have been tried and tested for years and weigh around 3.5-4 kg for the motor. A good branded motor costs around 1300-2000 euros without tax. an esc around 800 to 1200 euros without taxes. the parts lose little in value. it’s more like that you get almost the same money for it in 5 years if you sell it. the myth that mass production will eventually make everything cheap is true only for video recorders or cordless screwdrivers. real high-end e-bikes or aviation material will certainly be more expensive in the future because production costs are rising here rather than falling. also a sp140 motor will certainly be more expensive in 1-2 years than cheaper.

I know there are many projects with cheap motors and esc that are advertised on the internet as “working well”. that can be, but the point of view also depends on what is “good” i am of the opinion that an eppg, even if only for thermals, must be able to start on a meadow with zero wind without any problems.

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Thank you Thomas! Your knowledge in this area is very welcomed! I hear you about taxes, I had to talk to my brother in law from Germany to pick up my openppg frame as shipping is 300 euros cheaper there. Glad to hear it will be an investment that keeps it’s value, I hope the mad ampx 300A will be a good match for the Mad M50 'coz that’s the route I think I’ll go.