Blimp Drive dual motor, frameless paramotor

Builds
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Hello all,

I am an aspiring paramotor pilot, and after seeing the price of $7000+ for a typical gas unit, Justine Haupt’s blimp drive caught my eye - BlimpDrive Electric Paramotor I have already started building a blimp drive setup, so this first post is something of a catching up one. I am documenting this on a newly minted youtube channel: (https://www.youtube.com/channel/UCtMiqZYw7ZN9X2fNQxNuz2A)!

This design stands out to me as ideal for electric paramotors, sticking the props out in clean air and taking advantage of the smaller motor footprint. It’s also significantly lighter, the pole with motors and ESC’s will weigh in around 10-12 lbs, freeing up a lot of weight for batteries. Flight times will be nothing to write home about of course, but it’s interesting to see how light and affordable this setup will be.

I am building mine with an expectation of powered flight, not just a launch/boost for gliding. To that end, I needed more battery capacity. I also had costs on my mind, so I aimed to save money wherever possible. To achieve more air time and less financial commitment, I decided to build my own battery. Using Molicel P42A in a 12s6p fashion, I built a 25 Ah, 50 volt, 1.1KWh Lithium ion battery, weighing in at 10.5 Kg. Slightly heavier that Justine’s original, but with more capacity and the lower cell discharge voltages of Li-Ion, I expect 20 minutes. I plan on flying with more than one pack in the future for longer flight times, but this should get me in the air. Battery cost was about $400 USD. I had to buy a spot welder for it, but that’s something I will use for a long time. I have just now charged this 12s for the first time, internal resistance is below 2 ohms per cell, and it has taken every drop of the 25 Ah expected. I am excited to try it out.

As for the overall design, 2 major flaws stood out to me: Lack of pilot protection, and riser twist upon motor failure. The first will be solved with CNC machined carbon fiber frames that I will stretch a fine net or wire mesh over to guard the pilot from propeller shards and FOD. I am also attaching a 1/2" diameter, 24" long carbon rod to protect the prop from ground strikes. For the second point, I plan on mounting an arduino with a 6 dof gyro/accelerometer to measure rotation of the pole and shut both motors down if the rotation exceeds a threshold. This will need to be tested. I also opted for a pole that would not require reinforcing, a 1/8 inch wall thickness should give me a safety factor of more than 3 considering one side of the tube might need to support my weight.

That’s where I’m at so far.

A lot of my decision to pursue this was cost related, so here’s a run down of everything I’ve paid. No sales, no specials.

as of 1/16/21:

Actual costs after Shipping & Tax, USD: $4,109.69

Harness & Carabiners (glidersports): $347.39
Motors, props, ESCs: $1457.68 (t-motor seems to be unreliable, no updates in shipping after 3 weeks. I am leaving this cost here because buying from a retailer should be close to the same price. 130 kv U13II motors, 200A ESCs, 32x11 props)
Battery cells and supplies (18650 battery store): $444.02
Charger/PSU (buddy RC): $341.14
Spot welder (Keenlab): $255.59
Electronics (adafruit): $121.01
Electronics (amazon): $37.15
Electronics (ebay): $11.56
Hardware (McMaster Carr): $175.20
Carbon Fiber Tube (Forte Carbon): $544.00 (1.75" ID, 0.120" wall, 96" long)
QS10 electrical connectors (maxamps): $50.52
Carbon Fiber Parts (cnc madness): $253.00
M4/M5 hardware (Amazon): $35.97

More info to follow as I progress. I am open to constructive criticism.

About me: 26 yo, USA based paramotor pilot in training, I’ve been kiting for a year. My first flight will NOT be on this blimp drive, but on a moster 185 powered unit. I work at a hobby store, battery and motor/controller wiring are second nature to me. Both of my parents are hot air balloon pilots and I’ve been surrounded my aviation my whole life.

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just a tip: if you extremely overload the molicell with only 6 cells in parallel, as you intend, you can only expect a usable amount of energy of around 0.6 kilowatt hours. a very large part is converted into heat. the insidious thing is that the cells still appear as if everything were in order after 1-2 such loads. From the 3-5th cycle, you can already see a significant reduction in the possible capacity.

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Thank you for the warning. I will keep an eye on battery draw, I suspect I will want something closer to 12s10p in the future, but this should get me in the air at least once.

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So you will be running 2 ESC’s? How do you sink them for same RPM?
What BMS are you using?
I often though I should have kept my X4 to try and mount my Flexwing Trike so that I could have the folding aspect.
Looking at Electrifying my rig(not this year) I am now more concerned with fail over redundancy and having 2 smaller motors and ESCs could do that at a lower cost. Have 2 outboard motor/props on my set up would be easier to implement than on a PPG rig, with also being able to mount behind me and setting them up for folding them in so for trailering - I think the set up will be sightly heavier but I can live with that for the redundancy aspect if one side of motor or controller fails and I think the Delta trike would better allow for easier flight control in such a scenario.

TrikeMotor 2
TrikeMotor 23456×4608 3.13 MB

Cheers

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Yes, two speed controllers, two motors. I will not be attempting to synchronize their speeds. Similar to my experience in RC planes, a matched pair of motors and speed controllers will be close enough in power/RPM to not require some intricate system to monitor and adjust individual` speeds. Justine has not mentioned any noticeable twist from one motor running faster than the other.

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I’ve seen another site where a Paraglider created a similar system. The results are up in the air at this time, no pun, but she only wanted a few minutes thrust for lift anyway.

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You’re referring to Justine Haupt, who I have been in contact with while building this. She is not using variable thrust or attempting to sync the speeds in any way as far as I know. I am adding a gyro for emergency cut off, I could program my microcontroller to adjust thrust according to that. I will try flying first.

Along with cost, I don’t have the storage space for a typical gasser in my apartment. It won’t be replacing my gas unit, but supplementing it on days when I know I won’t have a lot of time to fly (morning/evening before/after work). Beats driving an hour to get my moster 185 for a 30 min cruise.

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Well there other model has 4 open props behind the pilot, loss of an engine/prop can make the flight interesting but it won’t come down in flames. Nice that you can lose power and just land, isn’t it?
I didn’t dig deep into the other “Zeplin” powered glider but she says it works for her.

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Stay away from that - it will kill you for sure. Something, (like esc/motor failure, bird/line-strike, MCU fault, lose prop, … too many to name) will eventually cause one side to fail, which rotates you 180 degrees, which immediately slams you into the ground.

There’s some videos around on Youtube of how fast those crashes are - so yeah, death is almost assured.

Something always goes wrong when paramotoring - so rule #1 is to pick solutions with the smallest number of fatal outcome possibilities. Like just one in-line prop.

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Your reply shows me that you did not read much of my original post, just looked at the image.

I agree, the image I posted is a very dangerous design. That’s why I am adding prop guards made from carbon fiber and steel. Riser twist is a real risk from one side suddenly losing thrust for whatever reason, which is why the motors will be shut down with a gyro/accelerometer in a matter of milliseconds if it senses an acceleration of twist on the bar. And now that you mention it, I will go ahead and add a second gyro for redundancy, thank you for your suggestion.

The motors are rated for 1000 hours. The ESCs will be capable of nearly double the current the motors require to run at full throttle.

No setup is foolproof, and I recognize this one is riskier than basically all others. But bird/line strikes, loose propellers, random failures, these happen to ALL paramotors, regardless of design, and they will ALL lead to an immediate slam into the ground.

Context is important. I will be using this deathtrap on perfect days when I can squeeze in 20-30 minutes before or after work. Just cruising. No acro, no XC, nothing dumb.

And when it’s all said and done, yes this is a riskier design. I am working to mitigate these risks. Is it enough for you? Clearly not. You even made a post about moderating ideas like this immediately after commenting here. Message received. Rest assured, I will be testing everything extensively, including destroying propellers and recording prop strikes on a pilot cutout. I’m not going into this blind.

That probably won’t be enough to convince you, but there it is.

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I love this – I would love to go back in time and see the sh!t talk back and forth with the Wright Bro’s and naysayers. :grin:

I am on both sides and both have merit – risk is higher, but without risk there cannot not be progress.
Cheers

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Thanks. I Don’t think this deserves a comparison to the wright brothers, more like Curtis, taking the idea and running with it lol. I agree, there is huge risk. I’m all for constructive criticism, but just saying I’ll die isn’t much help. I know it’s dangerous, this is all about what I’m doing to try to make it safer. That’s why I have life insurance. :rofl:

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Check youre policy – extreme sports may not me covered. my fellow pilots have instructions in case of an accident where I dont survive to drag my body out to the road to make it look like I was hit by a passing car :rofl:

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In all honesty, the Hindenberg type of propellsion seems so clumbsy and appears as it will get in the way and cause a lot of problems on a lot of scenarios.
This would work strapped on your back and not sticking so far out, 4x comes to mind.
Just saying.

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You should chew-out everyone who’s wasting their time telling you about your own mistakes in an attempt to save your life, and then tell a bunch of lies to yourself to mitigate the risks.

I’ve seen (and in my time personally experienced) line strikes, cage strikes, and props come off on regular paramotors, none of which resulted in anything other than a soft landing. I’ve also seen a riser twist: which was an immediate slam-into-the-ground. You said " , these happen to ALL paramotors, regardless of design, and they will ALL lead to an immediate slam into the ground." - that is a blatant and ignorant lie. A riser-twist is what happens in your risky (your words, not mine) design when your design gets one of those things - and mark my words - you WILL eventually get one of those things.

Which do you want to hurt - your feelings, from us pointing out your mistakes, or your family and loved ones who have to go to your funeral because you were too arrogant to listen to common sense?

It’s really simply to fix. Use 1 prop, like everyone else does.

I’ve watched a pilot die from his mistake, and it was a major suck-show. Hours of police interviews, abuse from hysterical loved ones, site shut-downs, negative publicity, and followup enquiries and regulations and increased restrictions.

Please don’t be stupid, because you are not the only one who is going to suffer.

I started the other safety topic because we all need to find a nicer way to politely try to educate idiots like yourself not to do risky things, and I’m trying to find out a better way to do this than by forum replies like this - which are creating toxic resentment, and causing me to have to endure the disgustingly disrespectful abuse that you are firing back at me for daring to try and look after you. You’re supposed to say “gee, thanks mate - I’ll change my design” - not argue about why you think you’re entitled to kill yourself and jeopardise our sport and sites in the process.

DO NOT REPLY. This is not an argument, it’s an education to you: and I’m not going to read this topic again.

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Well, there we have it. No more blimp drive. not replying to gitcnd or others on this topic. It was a fun conversation.

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I wish you much joy and success with your project. I also understand your joy in working. I also wrote justine my positive opinion on her blimp project on youtube back then. my opinion in relation to the possible performance of the molicell rechargeable batteries relates to technical aspects, since i know these cells very well from many of my own projects. I will give people tips to save money whenever it makes sense so that no components break. I don’t stop anyone from doing research or trying something as long as it’s not “completely crazy” all the best and don’t let others discourage you.

all over the world there are people trying to do things their own way. And that’s good :slight_smile:

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Riser twist is completely preventable. They are counter-rotating, so as long as they are both running at approximately the same RPM, there is no torque, and in this respect it is actually safer than a single prop. Anyone building their own system from scratch also likely has pretty good knowledge of microcontroller code which can monitor motor current from both ESC’s and kill the entire system in milliseconds if they measure a mismatch beyond 1 or 2%. (not motor speed, since we want to protect against a lost prop incident). If one doesn’t trust a single microprocessor, then one can implement multiple processors that must be in agreement at all times to allow thrust. As was done Circa 1969 on Apollo missions. This isn’t rocket science. I like Justine’s system and would like to see improvements. Clearly two medium sized propellers in clear air can be more efficient than a larger single propeller that is blocked 30% by the pilot.

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Brah this a is a forum… discussions/arguments are the whole point.

Progress, science and innovations is built on competition and challenging ideas of others. Just saying “if you don’t like my frame of thought and the lens i look at it with then you are an idiot” isn’t going to sway people. If you are looking to do that you have to make compelling arguments, make it more scientific and less name calling and emotions.

When it comes down to it if the goal is just to be safe as possible, never leave the couch at home. The world is a “scary” place and there are tons of risks out there. The thing is with all innovations and endeavors comes risk “high risk, high reward” kinda sums it up. @thisguyaves is willing to take a risk and stick his neck out and post his project online for others to critique or potentially bash and say its an idiotic design. That takes more courage than never posting any designs or projects of your own for others to critique and call “idiotic”.

This forum is really a place for actual projects and less theoretical talk. Talk is cheap and it’s up to every person to take in ideas of others and reason them and see if they stand up. There are a lot of dumb comments around the forum but i don’t remove them because i think it’s up to everyone to reason them over and come to their own conclusions. So ya i’m not going to make some sort of highly moderated “safety” section or forum with only ideas i deem safe.

Since @gitcnd is not going to read this if for the other here, actions are valued over words. So please share projects we would really like to see them and help make them the best they can be.

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There is a great new electronic device that measures the motor current. This could work when it does not see current at the motor it can cut the power. You’d manually need to start the remaining good motor up to limp home. cool stuff.