Paramotor Fun
This is just a bunch of random stuff associated with my paramotor.
I did not built it, I just bought it, and that in itself is a bit unusual! My paramotor frame is a Limitless (Spain), with a Dudek Powersport Light harness (Poland), a Vittorazi 185 Plus engine (Italy), a Helix 130 propeller (Germany), the wing is an Ozone Roadrunner 3 wing (UK / Vietnam), and the reserve parachute is a Niviuk Octagon 2 (France / Vietnam). Unfortunately nothing from the US, unless you count the import fees, reselling markup, shipping costs, and a few stickers.
First Photo
2024 October
It is always fun to take pictures while doing things. But, holy cow, what a first major step it was to pull out my phone, not drop it, take a picture, not crash, put my phone away, and not drop it. The following boring shot is my first picture.
Success!
Mixing Two-Stroke Gas and Oil by Weight
For my two-stroke Vittorazi Moster 185 I use Motul 710 oil in a 50 to 1 ratio by volume.
However, the sticker on my fuel tank is horribly inaccurate, and I do not have any other fuel container accurately marked for volume. So mixing accurately by volume is a problem. But I do have a whole bunch of digital scales, and one is rated to 25 kilograms. So it makes more sense for me to mix fuel and oil by weight.
Using an accurate 500 milliliter cup, I found that:
- 500 ml of the fuel I use is 360 grams.
- 500 ml of Motul 710 is 440 grams.
So, the Specific Gravity is:
- The Specific Gravity of fuel is 0.72.
- The Specific Gravity of Motul 710 is 0.88.
By weight, the 50:1 ratio becomes: (50 x 0.72) to (1 x 0.88) -> (36) to (0.88) -> 41 to 1. Which is close enough to 40:1 by weight and that is something I can remember.
For example,
- If I add 6 kilograms of fuel,
- (6000 grams, 8300 milliliters, 2.2 gallons)
- The oil needed is: 6000 grams x (1/40) = 150 grams.
- (150 grams, 170 milliliters, 5.75 ounces)
- Double checking:
- 8300 milliliters / 170 milliliters = 49 to 1 by volume... close enough.
- And, one of those "makes two gallons" oil containers has 5.5 ounces, also confirming the above math.
40:1 by weight -> 1000 grams fuel : 25 grams oil.
Fuel Consumption of a Vittorazi Moster 185
At 130 kg total weight, with a Ozone Roadster-3 26m, trims neutral, a Helix 130 propeller, straight and level flight, the fuel consumption of the Vittorazi Moster 185 is 3.1 kilograms per hour or 4.4 liters per hour. But it depends... if I take my winter jacket off, load less fuel, and put a notch of trims in, it is a bit less than 3 kilograms per hour.
But for practical purposes, it is really close to 3 kilograms per hour. And when planning for a cross-country flight, I use that number and then add two kilograms more.
I always weigh my fuel before the flight, siphon out the remaining fuel after the flight, and calculate the weight of fuel used. Siphoning takes no time at all! I use the freshest fuel in the paraglider, and older fuel goes into the leaf blower, weed wackers, and chainsaws.
Tuning a Two-Stroke
On the Vittorazi Moster 185 the high speed fuel screw is set and locked by the factory (it is a warranty thing). So the only adjustments to make are the low speed fuel screw and the idle speed set screw. My correct idle setting, and in my order of priority, is when:
- It does not die while idling.
- It does not die when it is throttled up.
- It does not engage the clutch and spin the propeller at idle.
- It does not have a noticeable speed "step" at about 6000 rpm.
When the idle is too rich:
- It idles and runs rough. It does what they call "four-stroking"; it kind-of misses every other turn.
- When idling, if you quickly squeeze and immediately let go of the throttle, the engine speed initially drops below the desired idle speed for a few seconds.
- If left idling, it will eventually just die.
- There is a noticeable speed change at about 6000 rpm when the high jet becomes dominant. In other words, as you accelerate up to about 6000 rpm with a rich low jet setting, the high jet (set correctly) takes over, it leans up, and speeds up! It is typically uncontrollable in the range between 5000 and 7000 rpm.
When the idle is too lean:
- When idling, if you quickly squeeze and immediately let go of the throttle, the engine speed initially stays higher than the desired idle speed for a few seconds.
- It is difficult to start; it needs a prime even when warm.
- If it is really lean, if you quickly squeeze the throttle from idle, it immediately dies.
When the idle speed is set correctly:
- It should not struggle or die (because it is too low).
- It should idle without engaging the clutch and turning the propeller (because it is too high).
The above is typically for when it is on the ground. When in the air if it idles faster and the propeller spins, it is not an issue.
Adjustments
The low speed fuel screw is so sensitive that the difference between too rich and too lean is 30 degrees (about 5 minutes on a dial clock). Final adjustments are made with such small movements you can barely notice them. It helps to have a tight fitting stubby screw driver with a fat handle (it makes movements easier to see).
I typically keep leaning until I find that point where it dies when opening the throttle. Then I make it rich until it just idles a bit rough. I then desperately try to find that perfect spot right in the middle of the two.
Once the mixture is correct, get that idle screw adjusted so that the propeller does not spin when idling. The idle screw is also very sensitive. Make small changes. I find it acceptable when coming off of a prolonged full throttle to take several seconds for it to slow down to that point.
When it is all perfect a warm engine should restart with one pull, without opening the throttle, without priming. It should just immediately start and be at a smooth idle speed.
Because of the location of the two screws, you can not (should not, do not) make adjust with the engine running. The last time I adjusted mine, it took a dozen iterations of take-off, adjust, put-on, start, stop. So... Be patient. Maybe get help.
Spark Plug
When tuned correctly the plug should be brown. The tang is brown in the photo, but it seems a little black at the threads. It was running just a little rich, but this was also during the initial engine break-in.
And honestly, checking the plug after a flight really checks the combination of the low and high speed adjustments. It is a way to verify that adjustments are not grossly out of whack, but it is not a primary way to adjust the mixture.
Phone Mount
To mount a phone on my paramotor, I bought a Quad Lock phone case, handlebar mount, the knuckle adapter, and the vibration dampener.
If you go to the Official Quad Lock website the things that I got were:
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A phone case matching my phone (listed under Cases. I got the original version, not the new Mag version with the magnet).
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A basic motorcycle handlebar mount (listed under Mounts), with...
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The vibration dampener (listed under Accessories).
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The knuckle adapter (listed under Accessories).
I would like to list part numbers for you, but they do not seem to have them?! Just search their site. Anyway, here are a couple of photos of the setup:
As a backup, a lanyard loop was stuck in the case (found on Amazon). This item provide a little hoop sticking out of the charging port.
Then I fabricated and bolted a boss onto the end of the left frame arm.
This boss is sized the same a handlebar tube that a mount would otherwise use. The dimensions of this boss is 30 mm in diameter, 29 mm in length, with a 6 mm through hole.
The through hole matches the attachment bolt, which matches an existing hole on the frame arm... 6 mm.
The overall length is determined by the grip length of the attachment bolt: Starting with a M6x50 bolt, subtracting the paramotor swing arm thickness of 12 mm and the washers and nut thickness of 9 mm, leaves 29 mm. Now this leaves no threads extending out past the bolt, and this is bad practice by aviation standards, but to me it is one less thing for stuff to catch on. And, this length provides just enough boss for the phone mount width (otherwise I would select a different bolt length).
