31-10-2012, 03:10 PM
An app that gives the RPM and speed would be very handy and give a quick result,
but I do like having the video to look at as well, It just adds some extra information when you have the picture too. You know what plane it is and where it was taken and you also get an idea of the distance that the plane passed by the camera. You can see how straight the approach and departure were so you have a bit of a handle for the accuracy of the measurement. When you pick a pass out of a bunch of video you can pick the best one to analyse, You can pick a video of a pass when there was little background noise from wind or other models or talking on the flight line.
Thanks for the link to that app Claudio, I’ll have a look at it when I get a chance.
The GPS option at first glance looks good but you only get a peak reading and the GPS probably only updates every 10th of a second if it’s a very fast one. A lot of cheap ones only update every 5th of a second. The positional accuracy of a GPS is not that great so when you want an accurate speed measurement over a short distance your going to get errors. Because a cheap GPS reader only remembers the top speed recorded then it’s just going to keep the largest error.
You’ve got to remember that the GPS is using satellites that are a very great distance form the model and the fact that the model is moving also adds in timing errors. It would probably not be so bad if the model travelled for a km in a straight line or if the unit recorded the average speed or recorded all the points and you did some other analysis of that data later on.
(30-10-2012, 08:52 PM)Skidz Wrote: I am pretty sure there is an RPM app for the iphone. I have seen heli guys using it some time ago.
I'll have a look for that as well but you need to do some averaging of the aproach and departing frequencies to get the RPM of a motor that it moving at speed through the air. Staticly it would be OK. It's nice to look at the spectrum and see which is the frequency you want to use tho', There are quite a few harmonics which can be ruled out by comon scence.
“The knack of flying is learning how to throw your machine at the ground and miss.”
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