tag:blogger.com,1999:blog-5854741938955568545.post8999297718123633974..comments2022-05-16T18:43:51.129-07:00Comments on ElectricRCAircraftGuy.com--RC, Arduino, Programming, & Electronics: Propeller Static & Dynamic Thrust Calculation - Part 2 of 2 - How Did I Come Up With This Equation?Gabriel Stapleshttp://www.blogger.com/profile/10071071884455787806noreply@blogger.comBlogger60125tag:blogger.com,1999:blog-5854741938955568545.post-24334416185534308862022-03-03T13:08:35.898-08:002022-03-03T13:08:35.898-08:002nd question you had: how can you measure flight s...2nd question you had: how can you measure flight speed? <br /><br />1. The best way is with a pitot-static tube, which is a little tube you have sticking out the front of an airplane, either on the nose or on the front of a wing, or sticking off the fuselage and aiming forwards. A pitot tube measures total pressure of the air. P_total = P_static (regular air pressure) + P_dynamic (pressure due to moving forwards and ramming into the air). P_dynamic = q = 1/2 * rho * V^2. V is velocity, so you can back out the velocity, accounting for air compressibility effects and shock waves if traveling at high speeds. For < 100m/s (224mph) you can assume air is incompressible and the calculation is straightforward. rho = air density and is about 1.225 kg/m^3, but varies based on altitude and daily fluctuations. Use the standard atmosphere table for estimates based on altitude: <a href="https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html" rel="nofollow">https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html</a>.<br /><br />2. You can also use GPS, but keep in mind you'd need to account for wind to get true airspeed, not ground speed.<br /><br />3. Lastly, you can record the audio (or video + audio) of the airplane flying by you, and using the doppler effect can calculate its ground speed (again, you'd have to account for wind to get true airspeed) based on how the pitch of the sound changes as it flies towards and then away from you. I have a nice writeup of that in my RC Aircraft book for $4.99. You can read how to do that on p67-80. Purchase that PDF book here: <a href="https://gabrielstaples.gumroad.com/l/YBRnP" rel="nofollow">https://gabrielstaples.gumroad.com - The Details of Electric Radio Controlled Aircraft (ebook)</a>.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-4915268311790042602022-03-03T12:54:47.175-08:002022-03-03T12:54:47.175-08:00Raul, I deleted your duplicate comment below. RPM,...Raul, I deleted your duplicate comment below. RPM, pitch, diameter, AND airspeed (V0) are **all** input parameters. The only output parameter is thrust. You see, thrust is maximum when the airplane isn't moving. This is called "static thrust". Since the air starts at a stand-still, it has a lot of acceleration to do, and therefore produces a lot of thrust, as the propeller accelerates the air from zero to some large airspeed. As the airplane begins moving forward, however, the delta velocity (and hence, acceleration) which the air can do is decreased, since it's already moving relative to the airplane, so thrust decreases. Thrust decreases as airspeed increases. They are tied together. The way full-scale airplanes counter this is they have **variable pitch** propellers. They increase the pitch as the airplane speeds up, thereby keeping a constant relative angle of attack of the propeller to the incoming air, which helps them keep thrust more constant as the airplane accelerates. See Figure 4 at the bottom of the article for a depiction of this. Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-28374814033143120472022-03-02T09:39:13.924-08:002022-03-02T09:39:13.924-08:00This comment has been removed by a blog administrator.raulhttps://www.blogger.com/profile/16651578224976071201noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-71265652648742559682022-03-02T09:37:43.620-08:002022-03-02T09:37:43.620-08:00Hello , supossedly isn´t it stated that rpm, pitch...Hello , supossedly isn´t it stated that rpm, pitch ,diameter are input parameters and flight speed and dynamic thrust are output parameters? Or how can i come up with the flight speed of airborne aircraft?Because the plot (Thrust vs Vo) showcase a range of Vo , but should not that Vo be a fixed Vo for the input parameters likewise Thrust? Thanksraulhttps://www.blogger.com/profile/16651578224976071201noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-5686843297662218522022-02-01T14:54:40.917-08:002022-02-01T14:54:40.917-08:00Enter your comment...explain slow how to know the ...Enter your comment...explain slow how to know the pitch and in equation 15 (A part) is it pure multiplication Anonymoushttps://www.blogger.com/profile/00556338518856286445noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-51538338824845229942021-09-29T10:53:27.849-07:002021-09-29T10:53:27.849-07:00Yes, so long as the propellers are in a side-by-si...Yes, so long as the propellers are in a side-by-side configuration, NOT a stacked configuration. Ex: X-4 configuration is fine; just sum the 4 motor thrusts. X-8 configuration will have additional error though, because each arm has 2 motors with the propellers stacked on top of each other, causing thrust interference and meaning my equation is not as accurate for that situation. See also <a href="https://www.electricrcaircraftguy.com/2014/04/propeller-static-dynamic-thrust-equation-background.html?showComment=1632937760930#c257941729645350640" rel="nofollow">my comment here from September 29, 2021 at 10:49 AM</a>.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-87808769008472540562021-09-29T10:51:27.514-07:002021-09-29T10:51:27.514-07:00Yes.Yes.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-80234623921911044232021-09-29T10:50:50.950-07:002021-09-29T10:50:50.950-07:00See my comment here from September 29, 2021 at 10:...See <a href="https://www.electricrcaircraftguy.com/2014/04/propeller-static-dynamic-thrust-equation-background.html?showComment=1632937760930#c257941729645350640" rel="nofollow">my comment here from September 29, 2021 at 10:49 AM</a>.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-5736628221824841232021-09-29T10:50:42.955-07:002021-09-29T10:50:42.955-07:00See my comment here from September 29, 2021 at 10:...See <a href="https://www.electricrcaircraftguy.com/2014/04/propeller-static-dynamic-thrust-equation-background.html?showComment=1632937760930#c257941729645350640" rel="nofollow">my comment here from September 29, 2021 at 10:49 AM</a>.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-2579417296453506402021-09-29T10:49:20.930-07:002021-09-29T10:49:20.930-07:00Go to the first article, click the spreadsheet lin...Go to <a href="https://www.electricrcaircraftguy.com/2013/09/propeller-static-dynamic-thrust-equation.html" rel="nofollow">the first article</a>, click the spreadsheet link, follow the directions at the top of the spreadsheet, insert your values and view the output thrust at the desired airspeed. Multiply the value by the number of motors you have producing this thrust.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-42363757439428950432021-09-29T03:29:53.189-07:002021-09-29T03:29:53.189-07:00TWIN / DUAL PROPELLER AND MOTOR
DIAMETER = 24 INC...TWIN / DUAL PROPELLER AND MOTOR <br />DIAMETER = 24 INCHES <br />PITCH = 9 INCHES <br />RPM = 3741 <br />Please help me dynamic thrust calculation for this configuration of twin / dual motor Anonymoushttps://www.blogger.com/profile/05027021746368583779noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-7432692340936509452021-09-29T03:26:05.587-07:002021-09-29T03:26:05.587-07:00I want to calculate dynamic thrust for two motors ...I want to calculate dynamic thrust for two motors with two propeller both propeller having same diameter and pitch and rpm <br />diameter = 24 inches <br />pitch = 8 inches <br />rpm = 3741 <br />please help me with how to calculate dynamic thrust with this data ( assume other variables ) <br />Anonymoushttps://www.blogger.com/profile/05027021746368583779noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-69713591634141093432021-09-28T22:32:36.799-07:002021-09-28T22:32:36.799-07:00How to calculate Dynamic thrust of dual motor havi...How to calculate Dynamic thrust of dual motor having two propellers?<br />Jayeshhttps://www.blogger.com/profile/13745189151030795916noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-31494099588996645122021-09-28T09:34:59.536-07:002021-09-28T09:34:59.536-07:00Just use the standard 1x motor / 1x 2-bladed prope...Just use the standard 1x motor / 1x 2-bladed propeller equation above, and sum the thrusts. This assumes the motors are both pulling or pushing in the same direction. If you have 1 motor producing 2.2 lb of thrust and another producing 2.3 lb of thrust, add the two together to have a total thrust of 2.2 lb + 2.3 lb = 4.5 lb, again, assuming their thrust is being produced in the same direction.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-9212436316909759032021-09-28T06:31:47.196-07:002021-09-28T06:31:47.196-07:00What is the formula for dynamic thrust calculation...What is the formula for dynamic thrust calculation for dual / twin motor ( two motor with two propeller )Anonymoushttps://www.blogger.com/profile/05027021746368583779noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-63461277200779846152021-01-19T15:10:48.197-08:002021-01-19T15:10:48.197-08:00Are these equations specifically for 2 bladed prop...Are these equations specifically for 2 bladed propellers? Anonymoushttps://www.blogger.com/profile/15248797801615290467noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-73761662669413993162020-12-24T11:56:30.686-08:002020-12-24T11:56:30.686-08:00Please see these comments about 3-bladed props, mu...Please see these comments about 3-bladed props, multi-bladed props, number of blades, etc.: <a href="https://www.electricrcaircraftguy.com/2014/04/propeller-static-dynamic-thrust-equation-background.html?showComment=1401497360928#c4348409272506596959" rel="nofollow">comment 1</a>, <a href="https://www.electricrcaircraftguy.com/2013/09/propeller-static-dynamic-thrust-equation.html?showComment=1380029669095#c839465916124560787" rel="nofollow">comment 2</a>, <a href="https://www.electricrcaircraftguy.com/2013/09/propeller-static-dynamic-thrust-equation.html?showComment=1508737294388#c2046412342224088407" rel="nofollow">comment 3</a>.Gabriel Stapleshttps://www.blogger.com/profile/10071071884455787806noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-28185788034586758322020-12-24T02:37:11.980-08:002020-12-24T02:37:11.980-08:00hi, im designing an airboat. i look the catalog of...hi, im designing an airboat. i look the catalog of airboat propeller. There variety type which is the size of the blade and the number of blade. can you explain me more how can i relate this equation with size of blade and number of blade in 1 hub ?<br />Anonymoushttps://www.blogger.com/profile/07155777636162085216noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-78263458779121089112020-10-19T22:21:51.732-07:002020-10-19T22:21:51.732-07:00Awesome job man! I've been looking for this k...Awesome job man! I've been looking for this kind of equation for a long time (and the explanation and logic to go along with it). I'll be applying it to quadcopters for now, and try to make my own extensions. Thanks for sharing your findings and research!Anonymoushttps://www.blogger.com/profile/00789711066086491404noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-64454078279191433302020-09-08T20:31:27.883-07:002020-09-08T20:31:27.883-07:00Yes that was really very clever approach😇👍Yes that was really very clever approach😇👍Devhttps://www.blogger.com/profile/01298787152511407159noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-28821203828542794232020-09-08T20:26:05.030-07:002020-09-08T20:26:05.030-07:00Absolutely genius bro....I literally found that ju...Absolutely genius bro....I literally found that just knowing simple equation may take some efforts but it's worth it....thanks for motivating me😇Devhttps://www.blogger.com/profile/01298787152511407159noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-74756190000938170492020-08-27T07:37:38.971-07:002020-08-27T07:37:38.971-07:00WOW! I sat down to start finding prop test data i...WOW! I sat down to start finding prop test data in order to basically do exactly what you've just awesomely shared with us all - YAY!!!<br /><br />I've written a tool to create ideal propellers (I called it "Airfoil Tools" - it's a free plugin for Fusion360). Right now, it's creating turbines beautifully, because we know betz law, so I was able to work the math. The problem with creating a perfect driven propeller, is that in order to know the correct pitch angles*, I need to know the flow rates, which are determined by the pitch angles... catch-22... or it was, before you came along :-)<br /><br />In reality, we actually also need to know the speed and chord at each station along the blade, so we can select the ideal airfoil shape to suit that, and these ideal shapes actually perform best at their own specific angle-of-attack, which needs to be added on as well - plus the entire result then needs to be "bent" in a circle around the axis (these airfoil sections go in circles - not straight lines).<br /><br />Similar to you, I used excel fitting on my (8 years worth) of particle-swarm optimiser results to try and give the optimiser a head-start when finding ideal shapes (and to avoid them being too raggedy) - I posted my research in comment 16 here: https://forums.autodesk.com/t5/fusion-360-api-and-scripts/add-in-announcement-hydrofoil-and-airfoil-tools-seeking-your/m-p/9638061#M10707Chris Drakehttps://www.blogger.com/profile/11378548000217150780noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-61747670437305989652020-08-12T01:47:59.406-07:002020-08-12T01:47:59.406-07:00No I think it will be lower than that. It'll o...No I think it will be lower than that. It'll occur when thrust is equal to drag. For quadcopters it will be dictated by a combination of angle of attack and the vertical component of thrust/weight. Metal Suckers of Dreamlandhttps://www.blogger.com/profile/00570504756608093158noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-73540953594772579342020-08-02T06:54:25.665-07:002020-08-02T06:54:25.665-07:00when i get 0 thrust at a speed, does this means th...when i get 0 thrust at a speed, does this means this is my maximum attainable speed of aircraft.Anonymoushttps://www.blogger.com/profile/06437238298903595291noreply@blogger.comtag:blogger.com,1999:blog-5854741938955568545.post-41825058263656661452018-11-13T02:35:23.492-08:002018-11-13T02:35:23.492-08:00This equation is applicable for multi rotors?This equation is applicable for multi rotors?Anonymoushttps://www.blogger.com/profile/17361655634197128597noreply@blogger.com