Thrust Tube speed test Worth it? lets test it.
2024 ж. 25 Нау.
3 500 Рет қаралды
Cant say Id rock the thrust tube unless i was hunting for an extra few mph. I think sticking with 98%. just a tiny reduction is the way. keep all the character of the fan.
I just watched a WW2 documentary where painting a B-17 bomber increased performance by something like 2-4 mph. The added weight of paint was offset by increased aerodynamic efficiency due to the paint sealing all the nooks and crannies. This meant a 3% reduction in fuel consumption or 80 gallons fuel. In real world performance, this meant a 80 mile increase in range for the same engine power.
Crazy!
@@hotlapkyleredbull F1 uses matte paint cause the tiny pockets stabilizes the boundary layer just like a golf ball. Golf ball got those dents so it wont knuckle ball. Thats why the africa world cup ball design isnt used anymore cause it was too flat
@@hotlapkylealso maybe lift the intakes a cm or so above the fuselage so it wont intake the boundary layer
Back in the day a rule of thumb was 85% of fan swept area, ie a good exit area was 85% of the area of the fan blades minus the area of the motor. For a 70mm fan -> 58mm outlet.
4 mph here, 2 mph there, another 6 somewhere else. This is the difference between first place and "also ran" or the difference between being an ace or canon fodder.
It’s so very interesting watching you fly your own creations!!! If I’m not mistaken you are 3D printing your aircraft, why not make a cowling for the edf. The one and only edf I have ever used (ima boat guy) 52mm, I made an engine compartment out of 1/4 inch foam rings and fiberglassed it. The intake was 34% larger than the fan swept area and 10% smaller at the exhaust and the exhaust length was very short this made a lot of difference. As a novice flyer I could not handle the speed of my flying wing (stryker ?)
Thanks! I have other designs with fan housings and nacelles. Check out my pocket rocket design 👍🏻
Hi! congratulations on making very nice models! Since you're trying to go as fast as possible, I would like to give you a small tip on the electric motors that might be useful when you're chasing top speed. A short disclaimer here, I have not watched all your videos so I might have missed you mentioning these things somewhere. Anyway, when a motor spins it generates an electric voltage, back-EMF. Most people understand that if you run a motor by turning the shaft by hand you get a voltage out as the motor becomes a generator. What many people don't understand however is that this effect is also true when you're running the motor from a battery (or other voltage source). It's useful in the sense that our speed controllers can detect the rotor position by measuring the back-EMF, but it has a major drawback which is that it limits how fast the motor is able to turn for a given voltage, regardless of load. You can think of it as the battery voltage - backEMF = useful voltage that drives current through the motor and actually does some work. So what happens when your model reaches really high speeds is that the motor might be turning so fast that the back-EMF starts to reach a voltage near the battery supply voltage. At this point your ESC is no longer able to produce any meaningful thrust. To overcome this, you can either select a motor with higher kV, increase the battery voltage or choose a fan with higher blade pitch so that it reaches the motors top speed at a higher airspeed. (This is just form a theoretical view, as it might not be practical to increase blade pitch). But warning is due here, increasing the voltage and the kV usually means you're able to drive a larger current through the motor at lower speeds and the risk of overheating is higher. A way to deal with that if you choose a crazy-high kV motor and lots of cells in series is to be very light on the throttle at low speeds and increase gradually while the plane is accelerating. Good luck with your projects! :)
Love this. I agree with everything you mentioned. Right now I’m about to maiden my V3 speed jet design. I’m chasing the most efficient airframe initially and once I land on a design I’ll build a custom edf. Something exotic at a larger scale. You’ll like to see my next design. I have high hopes
@drdistorzion, you have put into words what a lot of people have been thinking about, thank you for clarifying this. I have often wanted to test these kind of ideas but using batteries to power the equipment is problematic and a device that will provide a constant current is expensive. You are spot on with your statement.
@@nealstarling5422 Thanks, yes active current limit would be nice in ESC’s and not that super hard technically as long as it’s not requiring very high precision. But there is probably not much incentive from the market to include it in reality. I work with electric motors for industry and there it is always used, but it’s a totally different world of course. Speaking of top speeds, this is where the gas turbine really excels as it has such a super high exhaust gas velocity. A Lambert Kolibri turbine on one of these planes would be awesome! :D
This stuff exists on all VESC style ESCs. Constant current mode / current limiting. You even have FOC Field Weakening which can increase motor rpm by reducing top-end torque. This would probably increase your max speed! 👌It could also allow for you to use a e.g. 6S battery on a 4S EDF, and run a max amps instead. Most EDF thrust tables are also generated at 0 inlet speed, whereas here you have 100mph+ inlet which reduces thrust significantly 🎉😊
@@steffensolberg2924 Yes VESC us for sure an interesting alternative to check out! And yes the relative airspeed is the real problem here. That's where gas turbines really excel with their super-high exhaust gas velocity. I would love to see one of Lamberts Kolibri turbines on one of these models! :D
Let me know what you guys think. Worth the thrust tube??
Maybe. Do both tests in zero wind conditions. Also make sure the inlet area measured for the formula does not include the area of the nose cone spinner deal.
I love your video style, it's so candid and very genuine. Adds to how epic these planes are 🔥
Thanks 🙏 same to you!
It's so quiet as well, nice. 👍💪✌
A F1 team would spend millions of dollars for a 4 mph gain in top speed.
Absolutely. I prefer the punchy torque 😁
@hotlapkyle has the torque reduced, or is it perceived? The additional swirl in the tube may be countering it?
A thrust cone is better than a exhaust tube. The static thrust actually drops with the exhaust tube. On the other hand a thrust cone can yield about 25 % more thrust and thereby increase the air speed . World Model has one of the most efficient and lightest 70mm edf power pkant with a thrust tube as oppose to an exhaust tube.
I'm still saying that the recess in front of the fan isn't right. The sharp angles as it goes from fuselage profile to the hollow before the fan have to be causing a lot of disrupted airflow. Fair it in smoothly or just put more of a radius instead of the sharp edge and try it please.
If you look at the frontal view you’ll see half the fan. It’s getting more air then it needs. I don’t think that’s limiting it too much. Possibly a little
@@hotlapkyle what it is definitely doing is creating all sorts of turbulence right in front of the duct entrance. you may not have laminar flow anyway, but 100% not with that lip, and so you're almost certainly introducing inefficiencies. how much is hard to say, but surely at least some.
@@hotlapkyle is it that hard to edit the print file and eliminate the sharp transition between behind the cockpit and the fan? It's an interesting experiment. What you've got there is a classic Nono in aircraft design. Now I haven't done your type but I did study design and construction for human aircraft including general aviation and I have an A&P aircraft mechanic license and used to participate in building experimental category aircraft. I'm just basing my comment on my experience HOWEVER, the caviot is that air is funny, what happens at a micro scale doesn't always happen at full scale. I've seen models that flew that if they were full size would never get off the ground. But I'd bet your fan, although giving you lots of power, is ingesting flow seperated turbulent air into its lower half and losing (some) thrust as a result. If your trying to build the fastest plane it's something to address.
I was thinking the same thing, a lot of turbulence at the inlet.
@@bobjoatmon1993 If max performance is the goal, the plane should not look like a full scale supersonic jet. It should look like a glider with long, high aspect wings with unrestricted flow entering and exiting the EDF with no compromises such as a canopy. Basically a flying thrust tube. Aerodynamic efficiency is much more important than the mass of the aircraft.
Came across your channel. Great work! Amazing flights. Been "binge" watching. I fly turbines and EDFs. Sponsored by Banana Hobby. BUT I have 3d printed a cobra and Flys great! Love that printer lol. You might get a few more MPHs with a tube doesn't need to be long prob 2 to 3 inches. Maybe work maybe not worth a try! Will these files be availiable to the public and or for sale? Hmmmm?hmmmm? Lol KEEP UP THE GOOD WORK! Noonz out! 👊🇺🇲
Thanks!! All my files (once the bugs are worked out) are available on Cults3d. Link on my KZhead profile 👍🏻
Great updates geez
Try a -20% and see if what happens. Take a few data points and look for a pattern
Others have said to alter the intake area for the edf and I do agree. What I would start with first is the exit diameter of the thrust tube. It may be a little too small. The length looks about right.
Many say the exhaust is too large lol. It’s currently an 8% decrease. The plane was never meant to be a speed plane. I’m currently finishing up version 3. This was purely an experiment to see if I can increase the top speed with the thrust tube
with no inlet duct, you should be able to easily go 80% FSA to get the speed up
Love these videos! Meant to ask you what’s your preferred filament to use when printing the different airframes?
Active foaming LW PLA from any brand
Very nice test. I guess everything comes down to personal preference of what you want to do. These are toy airplanes designed for fun, not winning races or surviving war. I personally like the looks of the thrust tube. Perhaps you can do more tests on different airframes going as low as 85% FSA? A simple efflux tube made out of an old soda bottle is a cheap and easy way to change parameters for testing. Maybe invest in a pitot tube to measure true airspeed? I am just happy to have discovered your channel. It's refreshing to watch a non "review" channel that's not an infomercial designed to drive traffic to affiliate links or for the channel to get more freebies from manufacturers. I especially hate KZheadrs that promote gambling like Raffal.
I prefer thrust tubes for speed. And if you want static thrust to launch easier and do acrobatics, ditch the tube and add thrust vectoring.
OooooooSooooooNIIIIIIIIIICE! 😱😁🤪👍👍🇺🇸
does it actually make a difference?
Have you considered running a dual edf set up? It would add wight and complexity but really increase the available thrust. I think once you hit the 100mph range the induced drag is so high it's going to require great deal more power to overcome it and see substantial gains.
BTW with the dual motor setup you cold move the motors off the fuselage and under the rudders, getting the center of thrust closer the the center of mass, potentially making it slightly more efficient.
More optimize the intake of the impeller.
what torque.? do you mean p-factor.? the cross-sectional area of the exit opening should be equal to the effective swept area of the impeller. the edf could be mounted farther forward, if there would be a benefit. the shape of the area forward of the edf intake is Deflecting air away from the edf. and the amount of air Increases with the airspeed. i would suggest that you INCREASE the symmetricalness of the the NOSE. cuz it's very Asymmetrical now. d as you may know, cg should be located at THIRTY percent of mac. control surfaces should extend to the wingtips/stab tips. BECAUSE, non-moving outboard-located areas INTERFERE with/ damp responses to stick inputs.
If you are looking for an easy to launch, easy to fly and easy to land jet model, well your search has come to an end. I build the 50mm version and us a 4s setup with a 2200mAh Lipo. Just a little push ans its airborne. No bad behaviour at all. Just a stable, and if you like, a very fast flight. If you don´t like topspeed: No problem. Just 1/3 of thrust is far enough for flying and you can easily reach 6 min of flight time with a 2200 lipo. I use the 4s tattu 45C Lipos. And with a "normal" flight, they wont even get warm during flight. For landing: Just cut down thrust and let it glide to the ground. It´s just fun. Nothing else. Just one thing: you need pretty good eyes, because you soon reach a distance where it´s not easy to see. Well, I´m almost 56 years old. Should not be a problem for a younger pilot. When you push the throttle stick forward, the little thing almost explodes. Vertical flight almost unlimited, a roll at the top point and back down, flying 10 feet above ground at full throttle is amazing. Kyle, you did a great job. I can really recommend the little plane for all the people who want a fast flying EDF for just a little money. Just put it in the trunk of your car or on the backseats, and you can have fun everytime you want to. Greetings from Germany !
Thank you!!! 😄😄😄
Lower/remove the canopy.
It will reduce drag and let the EDF see cleaner air. Plus it should be easy. I doubt the change would be visible in flight.
I didn't notices, what FSA do you set here? You know that FSA is not just a outlet diameter. You set 10% of what What is it mean? For example, for 64mm EDF a 100% FSA is 57mm, 90% is 54mm. And 100% FSA is a good start point for further tests. GL&HF
You take the area of the inlet minus the area of the nose spinner deal to get actual swept area then subtract 10% IIRC.
This is a interesting test. For one I’m surprised a raw EDF actually achieved that kind of thrust at all, and that modest peak performance gains were seen on a thrust tube. Based off all I could research on EDFs and advanced basics on Jet engines I could find, the purpose of thrust tubes is for encouraging said thrust from the fan to go laminar at the exit, thus improving both its exit speed and the power to thrust ratio. A similar purpose is intended by inlet designs, in that an inlet helps the intake air go laminar before entering the fan, giving even load of thrust across its surface. Most thrust tube design is very rule of thumb in RC and even less refined for inlet design; basics being exhaust nozzle being equal to actual swept area of the fan (approximately 90-80% of the fan area) and the thrust tube length needing to be 2.5-3 times the fan Diameter. The most for inlet is that it should be equal in opening to total fan area, but I’ve observed on actual business jets that alot of inlet depths are roughly equal to the exhaust diameter. Regardless of convention you’re getting great results out of your builds already.
Wonder how fast it would go with my custom worlds most powerful 64mm edf unit?
Print it and tell us
Please tell me more about this fan
@@megatesla Can't unfortunately
@@rcplanepirate What impeller are you using and how many watts are you pushing through it on the bench?
@@megatesla it's a 5 blade 68mm fan rotor cut down to fit the 64mm unit. Running about 1600-1700 watts
Assuming temp was 70F. Doppler speeds: 2:56 96.6 mph 3:08 108.2 mph 3:17 sound not good 4:32 sound not good
I think it was 55F. Is there a App? How did you do that?
@@hotlapkyle Then the speeds were 95.3 mph and 106.7 mph. There should be apps, but the ones I tried many years ago weren't good. I open the video file in Audacity and look at the spectrogram of the audio. I can then get the coming and going frequencies and do the math with an excel sheet I got on RCgroups many years ago.
The thrust tube is printed? Wonder how much thrust is loss from skin friction dragged to the semi-rough surface. It could be interesting to compare with a smooth liner (perhaps posterboard) on the inside.
I just watched a WW2 documentary where painting a B-17 bomber increased performance by something like 2-4 mph. The added weight of paint was offset by increased aerodynamic efficiency due to the paint sealing all the nooks and crannies. This meant a 3% reduction in fuel consumption or 80 gallons fuel. In real world performance, this meant a 80 mile increase in range for the same engine power.