steelmesh

As the title alludes: would a speed wing be similar to a ground hog in regards to launching the wing and the kiting characteristics?  I like the idea of acquring a used smaller wing to practice with in higher winds and also since it would be a smaller package to bring on a trip or to work for lunch time practice, and also let friends try out kiting on something easier than a 28m wing.  

Top80 Miniplane is a classic

Checking in from USA; however, booked my training through SkySchoolUK while in Spain, total spend is nearly the same as taking the high quality training here in the States so I went with SkySchool because Alex and Europe in general has more history and experience with the sport.

I was curious to see what was out there as far as turn-key electric paramotors:

Like all electronics, ratings are misleading such as flight time so it may be wise to take 80% of the endurance they list as reality.

On 01/11/2019 at 14:31, noddyc said:

 Steelmesh

I would use the propellor hub/pully assembly , use a brushless motor, redesign it and cut grooves on the outside of the motor to run the drive belt over it - use the motor body as my redrive pully.

These  motors work very well as generators, that is how motorbike alternators are design (3 phases with a 3phase rectifier to get it to DC) 

That makes it very compact.

I was looking into building an electric paramotor and gave up after calculated that I need at least 287  lithium 18650 cells to get to at least 30min of flight time, and make it reliable. 

 

That sounds like a clever layout!   Probably shave a little weight off compared to other configurations. 

If someone develops an electric foot launch paramotor with a warranty right now and goes to market, it would be at least $20k and would probably still use off-the-shelf components and would still have an embarassing flight time. Anything cheaper would be some backyard built design that is a project in itself to use, and they probably make you buy your own batteries so they don't have to deal with managing energy storage.

23 hours ago, noddyc said:

The best way to approach this would be to get a small paramotor engine  (belt driven with clutch) and convert the propeller drive pully to a brushless electric motor  then you  could then run this as a hybrid , you could use that motor as a 3phase generator, for charging when you run the engine ( charging would have to be closely controlled or you would overload the engine). 

When the engine is stationery, the centrifugal clutch would disconnect and you could use the motor or you would be able to to use them together as well.  There would be quite a bit of electronic's and separate controllers involved to control and switch everything 

Alternator is around 75% efficient 

Motors is around 80 - 90%max efficiency if you are lucky 

Current draw at 72V   ,  13 kW =185amps

Heat, loss, bearings, electronics, batteries, charging,  etc will add even more losses

Hope this make sense, this is how they are integrating drone engines/motors. They use the motors to help with take-off. 

Just trying to understand your proposed transmission layout.  Are you thinking that a motor/generator could be in parallel with the propeller, where the combustion engine could directly transfer torque to both the propeller and the motor/generator?  Then the clutch would allow the motor/gen to drive the propeller with the engine off.  Sounds like the way to go if I assumed right.

In general how will you address problems with the power-to-weight ratio when going to a hybrid?  Long range full electric and hybrids are totally realistic if you wheel launch, but it sounds like no one cares about wheel launch electrics and only want long range foot launch electric paramotors.  

What is the maximum foot launch paramotor weight limit that is within reason?  30 kg?  Tesla battery cells have an energy density is about 0.25 kWh/kg.  Running 10kW continuous for 2.5 hours is about 25 kWh of energy.  25 kWh / 0.25 kWh/kg = 100 kg + [enclosure] kg + [bms] kg + [copper wire] kg + [contactor/fuse] kg + [reserve cell capacity] kg + [forgot about that] kg.  This doesn't consider losses so range would be lower or battery weight increases.

It's depressing I agree.

I think this has been evaluted by 100's of engineers.  They'll need to know a few characteristics to design against such as: 1) Maximum weight, 2) Minimum flight time, 3) Minimum climb rate.  These things will have a significant impact on hardware component selection.  Right now I think characteristic #1 is the deal breaker.

On 21/02/2018 at 18:18, Chance Waite said:

Something I have been thing about lately and may very well do, if I can figure out the particulars...I wanted to somehow acquire  a used paramotor frame on a trike and use a 2000W generator to provide a direct A/C current to a 80kv brushless motor. Seeing as how the power supplied from teh generator is 120v, I am not sure if I need to "step-down" the voltage, since the motor is rated at 70v, using a step-down device (power supply) or if I can just use a heavy duty ESC to do this for me, along with a servo to meter the power and thus the speed to the motor. Any thoughts on how I could accomplish this or is it even possible? I am looking to extend the flight time by mounting a "super-quiet" or some other variety of generator to the paramotor frame rather than a standard gas engine, or batteries in the case of an elec motor,  to power the prop. Is there some kind of "supply and demand" law I am violating or some other reason people resort to using batteries in this sort of an application rather than a generator?

Sounds heavy and inefficient out of the gate, I didn't see any focus on these issues (mass and power efficiency).  The most efficient route if you decide to use an internal combustion engine is:

[engine] -> [propeller]

Compare that to what you're proposing:

[generator] -> [dc-dc] -> [inverter] -> [motor] -> [propeller]

I've done some high level ideation to realistically design a traditionally configured electric PPG with 2 hours of flight time and reserve power.  You would need ~200 lbs of lithium batteries, so foot launch is out of the question it would need to be wheel launch. 

Most LiPos are rated for 3.7V/3.8V nominal, which makes it challenging to add to a lead acid charging system.  I think the paramotor manufacturers are selling are LiFePO4 lithiums, which have a lower nominal voltage at 3.3V and are more tolerant of abuse (aka safer) when added to a lead acid charging system.

With LiPos you are required to run a BMS to ensure safe operation, you cannot ensure safe operation of a LiPo battery without a BMS.  The bandaid is to use a balance charger in balance charging mode which will catch a bad cell (and prevent charging) before the battery is put back into service.  LiPos are most dangerous when they are fully charged, this is when they will release the most energy during a 'rapid disassembly' event.  A reliable way to set off a lipo pack is to overdischarge it then puncture it. Most of the gas released is very flammable which can reach 1000C at the source if ignited.

On 19/09/2019 at 18:39, GerardTC said:

Thanks for your response.

Today I replaced the reed valve and changed the main jet to a smaller one (140). Fortunately the engine revs up better and reaches 7800 rpm. Spark plug colour looks good.

However the idle is still very rough... between 1500 and 2500 rpm (is it normal?). I tried bigger and smaller pilot jets without noticing major differences.

Next I will measure the piston squish clearance and compression but I have no references. Does anyone know these values?

Thanks in advance!

BTW, thumbs down for Polini's information and documentation on their engines. I only found a couple of PDF with very little information. 

Do you have a pop-off valve and if so have you checked it?  I know pop-off in mikuni carbs works with the low speed jet, so if you're pop-off is way off then your changes to the low speed jet might not have enough impact to compensate for an out-of-spec pop-off pressure.

On 20/09/2019 at 21:02, GerardTC said:

I am tuning the carb at about 200m altitude and most of the times I fly between 200 and 500m. Spanish climate, currently it's 20-25ºC but in winter season we fly at 5-15ºC.

Since this carburetor is very sensitive, in colder temperatures I will probably need to go for bigger jets. On the contrary, in higher altitude flights (+1000m) I'll need to go for smaller jets.

My experience with carbs is from tuning 2T ground vehicles and watercraft. I am pretty new to the 2T aircraft engines, in theory they are pretty much the same as any other low displacement 2T engine, but as you pointed out new variables are introduced from a relatively extreme change in operating conditions on-the-fly pun intended.

My only thought is to reference manufacturer settings then make adjustments from there for your application and location.  That sounds good on paper; however,  my experience with reality is that manufacturer specs aren't always right for your application or at least aren't always fully optmized (because emissions or dumb people for example).    

I hope to hear from some tuners who have experiences with these aircraft carbs, always something to learn.

The air screw should be used to set your idle fueling and the idle adjustment is used to crack open the barrel or butterfly.  Assuming your pilot/low jet is correctly sized you should be able to adjust the air screw until you get a smooth idle.  If you're air screw is way off then that means you might have to adjust the pilot jet.  

How many meters above sea level are you tuning your engine?  Is it hot out too?

Better check the reeds or replace them since it looks like you're doing a complete refresh.  If the reeds are good then sounds like maybe an air leak somewhere or your carb is not setup right.  Is there a pop-off valve in your carb?  Down the road you might need to pressurize the crankcase to check all the seals.

Also, is compression within specifications?

Comes to mind now because last night I finished fabricating the exhaust for my racecar and for the wastegate dump pipe (dumps to atmosphere), I used a 1.5"/38mm diameter flex joint before hard mounting the end of the pipe.  I wonder if something like a flex joint would be beneficial where maybe the flex joint wears out and starts leaking, but prevents cracked pipe joints in the long run.  The braided stainless would keep the joint from failing completely because you would obviously hear it leaking before it gets that bad.

Reading your first post again: "Leading up to these two engine outs I was cruising/maintaining altitude and then wanted to gain height.
Applied more throttle and felt like I wasn't getting the power. 
About 5 seconds after trying to apply full throttle the engine died, like it wasn't getting the fuel or air in the line."

If the engine struggles/sputters to stay running with full throttle it's probably rich, if it just dies/stalls while full throttle it's probably lean.  This could be related to an issue with the high speed circuit of the carb or a fuel flow problem were high power demand requires more fuel flow.  Also, be sure to pull the reeds and inspect the reeds when you pull the carb.

As you're already doing, I would suggest a carb rebuild and check your jetting.  

Does the engine just cut out or is there a bog involved before it dies?  If there is a bog, at what RPM does the bog occur?

Paraflyer, yes you launch the wing with just your hands, but don't do it in high winds.  Recently someone was on a hill hand kiting and got lifted 100 ft (33 m) off the ground and it ended in the worst way possible.  See paraglidingtalk.com episode 86 (last night).  Just do it in low winds without a storm coming.

Skip to 17:45 to see one-way to hand kite, he talks a lot so skip to 17:45 to see it: https://youtu.be/qEqzwyofkyo

At least get familiar with setting up the wing and hooking in to start as they show in Aviator PPG.  I'm looking at SkySchool and they teach a very similar method for reverse kiting hook-in so I was confident to practice that method.    As you get comfortable, try to launch it with by hand kiting it, a little wind in an open field without obstructions around.  See PPG handbook page 145 (Fig. 15.12) of the 5th edition Chapter 15.  I figured this out on my own, by holding the front A riser with your right hand and grasp the riser/brakes with your left hand: just remember to run sideways towards the side of the wing falling while pointing your left hand towards the falling side of the wing (because it brakes the right side). 

Run towards and point your left hand (D's/brakes) towards the falling side of the wing...the wing will want to point into the wind that's why you got to move with it, then use your left hand to keep it centered. Next the controls to make the wing go up/forward and down/back is the fact that if you pull on the Front A's the wing will go up/forward (forward means that you're standing still and the wing goes too far forward over-shooting you, so brake it by pulling the D's/brake side).

You already got the wing so "Send It".

I'm not training until next spring, but already have logged 10 hours of ground handling practice with a used 1.1 28m wing. There is nothing like seeing the wing and risers in person. I got the basics down, but still a lot to learn so I can't wait to work with an instructor to get the whole shooting match.

I watched the aviator ppg and skyschool resources on ground handling and stick to what they demonstrate exactly, this is my argument against the "bad habits" warning.  The first thing I did was setup the wing/risers outside and with a mobile phone watched the section on hooking up the risers and the safety checks. All I did was practice clipping in and out of the harness, referencing the tutorial on this every 5 seconds (it seemed) to make sure I do it exactly as they show it without missing a step. Even though I didn't understand why you need to flip stuff around and grab things at weird angles, once I did it in person I could see why they teach you these things.  Before even thinking about clipping into a practice harness, I started with "hand kiting" and wall building until I was consistently successful, these two skills are used every time I setup the wing before clipping into the harness to make sure the wing is untangled and pointed in the right direction. Hand kiting is an elementary skill you should learn first. 

You'll need a wing available to practice with.

I am also assuming that people who have never handled a wing will become physically and mentally exhausted trying to learn the basics of ground handling on the first days of training.  I think investing in ground handling practice before training will ensure you can focus on the advanced techniques and even be "that student" who makes the most flights because they are ahead of the class.

Smoke might be a counter-measure here

I was just thinking to start off with a small moving dolly (flat wood frame with 4 caster wheels) and a way to secure the motor to the frame like a tight bungee cord.  My cylinder is on top of the engine so I think it would be good enough to service it on the dolly stand.

If you got money to burn on luxury, a motorcycle lift would be sweet.

Thanks for the explanation and warning about the brake line length.  It is a high hang point harness and my glider is a Dudek Universal 1.1. 

APCO has some pretty limited instructional materials for their SLT harness...

Do pop rivets secure the harness grommet to the J-bar? See image with green arrow.

How else does it look? See other images

In addition and in general: injecting something in the exhaust will change the acoustics of the expansion chamber changing the way the engine performs.  I learned about this when I was looking to modifying a gp1200r 2 stroke waverunner.  Details here:  http://greenhulk.net/forums/showthread.php?t=13613

The Dudek Universal 1.1 manual says to trim out in strong turbulence (pg) and suggests with the trims all the way out it is very resistant to frontal collapse and the rear risers have almost no pressure on them so you'd need to tip steer.  In general with a reflex wing in reflex mode, are pilot inputs reduced when in turbulence?

Give me some adderall please!