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  • Users: Ryoko
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  1. R

    Automotive Max Power Output with Air-Fuel Ratio

    A richer mixture lowers the exhaust gas temperature. In other words, less heat.
  2. R

    Solving for Angle to Destroy Rocket Launcher

    There's a square root in there, so you need to consider both the positive and negative roots.
  3. R

    Extending an aircraft landing gear that has gotten stuck

    A high positive G maneuver and a sharp roll to the right would take advantage of the gear's linear and angular momentum in an effort to free the gear.
  4. R

    Propeller - Rearward flow of air

    Lift is proportional to the change in momentum imparted to air. This change in momentum (and hence air velocity) is observed as downwash.
  5. R

    Automotive Max Power Output with Air-Fuel Ratio

    I've forgotten much of my thermo from college physics, but I think (at least part of) the answer as to why a richer fuel mixture makes more pressure/power is because you're converting more liquid (the raw fuel) into a gas.
  6. R

    Automotive Automotive MAF sensor vs temperature

    No. I started from scratch. I have a design which uses a pair of PIC processors and a lot of glue interfacing to talk to the various sensors and igniters. The idea is an extension of an earlier design which I made to replace the VAFM in my old 4Runner with a modern MAF sensor. It made a big...
  7. R

    Automotive Automotive MAF sensor vs temperature

    I under the difference between MAP and MAF based systems. The EFI I'm working on is intended to be a MAF system with a MAP fallback mode. The MAP (along with the TPS) will be used as a load sensor to fudge the mixture based on power demands. And yes, I have circuitry for an O2 sensor and dual...
  8. R

    Automotive Automotive MAF sensor vs temperature

    I'm finding mixed info on whether it's necessary to correct for temperature for a MAF. Some data I've read says that they are temperature compensated. But I'm seeing info elsewhere that suggests a correction is needed. I guess it depends on capability of the MAF unit being used. As I understand...
  9. R

    Automotive Automotive MAF sensor vs temperature

    Unfortunately, data sheets don't seem to be available -- at least none that I could find via google.
  10. R

    Automotive Automotive MAF sensor vs temperature

    I'm working on a DIY EFI system for automotive use. I have a question about the mass air flow sensor operation. I know they measure the volume of air passing thru them. But the question is whether that measurement needs to be corrected for air temperature or if the MAF sensor does that by...
  11. R

    Twins Paradox clarification

    Let me ask for some clarification about what it means to be in the same inertial frame of reference -- Does this mean that two observers are experiencing the same magnitude of acceleration or does it mean accel + velocity + direction?
  12. R

    Java Online Javascript courseware?

    Thanks. I'll take a look at the links tomorrow when I get a chance. I've read the O'Really Javascript: The Definitive Guide book ... all 1000 pages. Pretty dry reading. Nice reference, but it doesn't really offer a lot practical use guidance. Just lots of theory.
  13. R

    Time dilation and space ships

    OK, so let's simplify this a bit. Let's say there are only 2 ships. They start out next to each other and synchronize their clocks. Then they move apart for some distance at equal speeds, coast for a while (no acceleration), then turn around and come back together and compare clocks. What will...
  14. R

    Time dilation and space ships

    This has bothered me for a long time. I understand that time varies with velocity relative to the observer. But what about this case -- Suppose we have 3 space ships: A, B, and C. They are spaced widely apart with B in the middle and A and C at opposite sides to B. A and C are moving towards...
  15. R

    Java Online Javascript courseware?

    I'm looking for recommendations for javascript courseware suitable for self-study. Most of what I've found assumes no programming experience and is too basic and not really usable for building skills to a professional level. I'm already proficient in OO languages such as C++ as well as being...
  16. R

    Software for calculating aircraft aerodynamic coefficients

    PanAir is free and will do it. However, getting your model into it is a bit of a challenge. I have a program that allows you to model you craft using Blender3D and then exporting it into a PanAir friendly format.
  17. R

    Identify this aerospace astronomical navigational device?

    I'm guessing it's part of a gun turret.
  18. R

    Calculating Loads for Static Fan of 6,060kg: Help Needed

    There's almost enough information, but I think you may have missed the point that it's a set of 11 simultaneous equations that need to be solved. That isn't something you want to solve by hand. It's usually easier to treat the load as a point load and assume a worst case loading arrangement...
  19. R

    Calculating Loads for Static Fan of 6,060kg: Help Needed

    It's still a tough problem to solve by hand since you have a big list of unknowns. You have the load at each point plus the resting height and angular rotation of the fan assembly.
  20. R

    Calculating Loads for Static Fan of 6,060kg: Help Needed

    The problem is statically indeterminate. To illustrate the problem, suppose that one of the mounts is sitting up a little higher than the others. Much of the weight would then be carried by that point while others did nothing. Of course in reality, the frame will have some give to help balance...
  21. R

    Synchronization of a camera with a rotating shaft

    It's not so much that each pixel might have different timing, but rather that microbolometers are in essence tiny thermometers and like thermometers, they don't respond instantly. So a spinning shaft will likely be seen as just a blur even if the camera is timed correctly.
  22. R

    Torque vectoring:why does the inside front wheel also have same torque

    One other point is that having unequal torque on the front wheels is unpleasant to drive because it causes torque steer.
  23. R

    Turbocharging Gas Engines

    Intercoolers are not there to improve the volumetric efficiency, per se. They are there to reduce the temperature of the compressed air to improve the air density and because charging the cylinders with heated air can produce excessive combustion temps and high EGTs. EGR systems are there to...
  24. R

    Could hydrogen rigid air-ships return?

    IIRC, it wasn't the hydrogen that brought the Hindenburg down. But rather it was the flammable dope used to paint the outer fabric that led to the disaster. The hydrogen just added fuel to the fire. The early aircraft dopes used to protect the fabrics were accidents waiting to happen.
  25. R

    Calculating Drag Increase with Airbrake: Semi Span

    Semi span is half the wing span.
  26. R

    Synchronization of a camera with a rotating shaft

    One thing that needs to be considered is the speed of the camera. The models cited use microbolometer arrays which are not all that fast to respond to temperature changes. A spinning shaft may be a bit too fast for them to capture in any detail.
  27. R

    Understanding the divergence theorem

    Almost. Not through the volume, but rather being sourced or swallowed by the volume. For example, you cited ∇E which is often seen as part of one of Maxwell's equations. In this case, ∇E = q, which says the flux leaving a volume (the divergence) is equal to the amount of charge q contained in...
  28. R

    Understanding the divergence theorem

    Divergence is not the strength of the field at a particular point. Divergence is the total amount of flux going into or leaving a volume at that point.
  29. R

    How to analyze a wing spar?

    I use a rectangular distribution for lift forces when working with spar loading. It gives conservative results and is a reasonably good approximation to wing loading.
  30. R

    Damping ratio from Eddy current breaking

    Eeks. That's a tough question. I wish I still remembered more of my e-mag coursework. The answer depends on the magnets shape, spacing, and how the magnetic flux flows around them and thru the disk. In short, you need to solve for the B-field that passes thru the disk. You could cheat and...
  31. R

    Should I Use A Microcontroller Or A Microcomputer?

    As much as I love the Z80, it is a bit dated now. The newer microcontrollers are far faster and smaller. Most include internal EEPROMs and have inexpensive development boards available with prototyping areas on them. You can get a complete development system (including a dev board) for under $100.
  32. R

    How many gears to rotate a 34mm dial 28.07 degrees?

    That all depends on how much force will be applied and how fast you want to turn it. Maybe if you explained what you're trying to do.
  33. R

    Explain my capacitor discharge math discrepancy

    You need to keep in mind that there are losses in the transformers, the diodes, and the capacitor itself.
  34. R

    Zin of a circuit with independent sources

    Your equation (s(Lg + Ls) + 1/(gg + sCgs)) is the impedance. Someone please confirm, but all you need to do is replace 's' with 2*pi*f*i where i is the imaginary number sqrt(-1) and f is the frequency in hertz. Then solve the resulting complex equation into real and imaginary parts.
  35. R

    Fixing My Old Heath Kit Oscilloscope

    heh. I think I got one of those up i my attic. As far as I know it still works.
  36. R

    Antisymmetric modeling for panel method solver

    This is a section from the Pan Air user's guide (Pan Air is a aerodynamic panel-method flow solver). I'm confused by the symmetry and anti-symmetry. The first one is easy enough: mirror about the XZ plane (Yimage = -Y, Ximage = X, Zimage = Z). The third one is no symmetry applied. Also easy...
  37. R

    Humans relate acceleration of a car with change in pedal angle over t

    I never paid much attention to the pedal angle, unless I run out of travel mashing it to the floor. I think the seat of the pants feel and engine noise are more informative in terms of feedback.
  38. R

    Solving Exchange of Momentum by Conserving Energy & Momentum

    There's a video of this very problem on YouTube. The results are not exactly what you'd expect. The video does compare two wooden blocks, one shot thru the CG and the other shot off-center. Both went the same height into the air. Of course, this raises the question of what happened to the...
  39. R

    What is this HF comm mode?

    Don't know if this is the proper name for it, but I'm guessing it's single-tone multi-frequency encoding.
  40. R

    Engineering Do electrical engineers only work with circuits?

    I graduated with an EE, but most of my career has been in programming.
  41. R

    High order panel modeling units?

    I understand that the coefficients are technically non-dimensional. But the program asks for things like span and area which is causing the reported numbers to change dramatically. It's pretty clear it's deriving the coefficients by dividing the forces by the area & span as needed, but the...
  42. R

    Wing Span Efficiency Factor

    Short answer is yes, you can have a >1 efficiency factor. But you have to cheat. It's accomplished by using tandem wings or boxed wings. Winglets also allow for a >1 factor.
  43. R

    High order panel modeling units?

    I have a copy of Pan Air (A502) which is a high-order panel method used for modeling 3D airflow around arbitrary bodies. I've read the manual, but I'm not clear about the units used. As I understand it, the free stream velocity is normalized which implies that all the other geometry is scaled by...
  44. R

    Is free (or very cheap) FEA software really available and worth it?

    This looks interesting (but their website is lacking):
  45. R

    Motor Powered Generator

    Short answer: no. That would violate conservation of energy. The gear box losses alone would prevent that from working.
  46. R

    How to build a good voltage regulator

    Not sure if you're going to be able to do that. Oxygen sensors work by charge balancing. The voltage output is a side-effect from that. Your ECU may not like a raw voltage being fed into it because the charge balancing circuits are not going to behave properly.
  47. R

    How to find neutral point?

    You need to do wind tunnel testing or use numerical methods. You can also use a cookbook approach, which requires you to know the pitching moment of the wing and the amount of downwash on the stabilizer. But the easiest method is to set the CG at 25% chord and move it aft a little at a time a...
  48. R

    Connect High/Low Level Alarm Circuit with 6 LM741 Op Amps

    U3 and U4's function has me scratching my head. I haven't seen that particular arrangement before. It looks like it might be a variation of an ideal diode feeding a peak detector.
  49. R

    Need enginering help - lifting 1000 lbs 16 feet

    Make a pole climber using a rack and pinion drive. Attach the rack to the side of the pole and have the pinion drive attached below the rafters. The pinion drive walks up the rack lifting the roof.
  50. R

    Phase detector for PLL with low SNR

    I have to ask, why are you using a PLL for this? If all you want is to provide stimulation to a resonant device, all you need is a simple signal generator tuned to the resonant frequency.