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steelmesh last won the day on November 29 2019

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  1. For people diagnosing this: In the Walbro Manual, Page 12 has a few things to look at regarding "Poor High Speed"
  2. Maybe your high speed circuit is too lean for the weather, because there are certain circuits in the carb that come on at different air flow demands (throttle position) where yours is unhappy with lots of throttle. See attached chart to get the idea (from the mikuni sbn manual). Since you're flying in cold weather, it's probably a lean condition. Also, check for air leaks (crankcase may be leaking 2t fuel) and check the reeds.
  3. I've worked on similar diaphram pump carbs in watercraft where the common issue is hard starting and the common practice to solve it with these old 2T engines is to install a stand alone priming system (not just a bulb on the fuel feed). The priming system has it's own fuel pickup (using a T on the fuel feed/return hose) and squirts liquid fuel into the carb throat directly. Here is a $35 USD primer kit for a single carb: https://rivaracing.com/i-17284794-riva-primer-kit-single-carburetor.html
  4. 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.
  5. 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.
  6. When I was ready to purchase and had the funds, I started checking ebay every day, yes every day. I searched "paraglider" and "paramotor", then sort by Newly Listed. You get to see everything related to the sport being posted daily. The secret to find a great deal be it eBay or "craigslist", it's being one of the first people to read and act the advertisement when it's posted. You don't see the fantastic prices because the ads get taken down right away because the sale has finalized. I got a low hour 28m Universal 1.1 for $1600 shipped (1250 gpb) for example. It's not a beater wing so I do care for it. I think there are some heavily used wings on ebay from Bulgaria or Poland for cheap, others may chime in on the heavily used wings, but if the lines are stretched out of wack then you might be fighting a lot more with it.
  7. I was curious to see what was out there as far as turn-key electric paramotors: https://files.catbox.moe/72ovh6.JPG 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
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