Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Speed trap

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Old 06-09-2003, 06:27 PM
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Stuntpiloot
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Default Speed trap

Hello you guys,

I was wondering, is it possible to build your own speed trap?

What are the best options for detection?

If not possible or too expensive/difficult: Where can I buy one and what do they cost?

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Old 06-10-2003, 02:22 PM
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Default Speed trap

Ok, let's make the question easier

How do you guys measure the speed of your planes?
Or are they all just wild guesses
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Old 06-10-2003, 03:39 PM
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Default Speed trap

about a year ago most people guessed meaning anyones dust on a OS46fx went 240 easy.
we ues a video camera here to recored the sound then use a program to work out the doppler.
you can find the program for download via my web site.

240 my ass
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Old 06-10-2003, 04:13 PM
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Default Speed trap

You can measure the length of your field, get three of your buddies, one with a stopwatch, one on each end of the field (maybe near a tree for protection?).

Then, do a high speed pass over your field, have the end of field observers raise there hands when the plane flys by, giving indication to the timer when to start and stop a stopwatch, record the distance vs. time, then do the math.

This is probably the easiest. Not as precise as doplar shift or a radar gun, but it will probably be within 1 or 2 % of actual.
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Old 06-10-2003, 04:14 PM
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Default Speed Traps

Speed traps are really hard to come by. I've been looking for one that would be FAI approved, but so far in my search there equals zero. I've used GPS, but it can vary quite a bit. I'm not sure the doppler provides the 200m span of the trap required by FAI.

I have written to the AMA about measuring speeds of straight line R/C aircraft, but I don't think they have a clue and they are the US authority. At least I haven't recieved a reply back from them in regards to a 200m FAI legal measuring device.

There was a speed trap made back in the mid 90s and the Jet Pilots Organization bought several of them, but that supplier of equipment has since gone out of business.

I would like to find one that uses video or photo images so you have an actual record visually with a date and time stamp in the images. Something you could play over or show for verification. Not just a readout for a speed.

I have had some of my planes shot with a radar gun, and some of the speeds were fantastic! Not realistic! Plus a lot of the really fast deltas are somewhat stealth to a radar reflection. Some mention the prop altering the speed gun accuracy. I think this could be true to a reasonable extent.


If anyone has any ideas, please post them.

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Old 06-11-2003, 04:40 AM
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Default Speed trap

OK, all thanx for your replies.

We've tried the stopwatch thing already, but we were looking for something easier.

I'll take a look at the site of phillybaby about the doppler thing.

I was just wondering if we could build a device that measures the speed. An optical device is rather difficult, because a small plane at that speed is hard to detect, or the position above the two sensors should be very acurate. We we're thinking about an other way to detect the plane passing......
It should be easy to build, and cheap!
We came up with the following:
Setup two position microphones X meters apart, with a cone or other shape on top of it to narrow the measurement surface. The signal that comes from these should be a parabolic signal, as the intensity increases when the planes comes near, and decreases if the plane flies by. All we have to do is detect the top of the signals and calculate the speed. If the height at which the plane flew over both sensors is not the same, or the plane did not fly correctly over the sensors the signal will still be a parabole, but the intensity will drop.

It's all just theory, but we'll build a test setup this summer and see if the signal is detectable.

If anyone else has some ideas to improve this theory (or test is) Please post here so every one can use it.
:idea:
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Old 06-11-2003, 04:24 PM
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all ready came up with that idea, it evolved into camera sound triggers connected to a stop watch, never got that far before i got the doppler shift prog
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Old 06-15-2003, 03:48 AM
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Default Speed ...........

Why not use a chronograph - (did I spell it right?) - these are very precise - used for measuring the speed of a bullet - 0 to 4000 feet per second - you can get one at a gun shop.

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Old 06-15-2003, 04:05 AM
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Default Speed trap

Explain Jackjet,

What is a Chronograph, other than a watch? Can you show us a photo of one and how it works as a speed trap? It's accuracy?

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Old 06-15-2003, 04:31 AM
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Default Chronograph

Blue Sky,
it is a electronic device used to measure the speed of bullets. They cost $100 and up. Just type in bullet chronograph on any search engine and you can look at them.These will measure aircraft speed VERY precisely.

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Old 06-15-2003, 03:04 PM
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Default Speed trap

anyone wanna fly through these triangles

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Old 06-16-2003, 11:00 AM
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I've been playing with the analysing tool and I cant wait to record the sound of my plane's flyby......
It works great!, the only minus about is the part that you'll still need to do the calculations seperately in exel, If that could be integrated ass well it would be more nice

I'll see if I can record my plane this week (wednesday probably) and I'll post my findings here.
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Old 06-16-2003, 11:15 AM
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Default Speed trap

try this german doppler shift program.

There are pics, and example files so that you can figure it out by yourself without reading the german text :-)

http://www.sprut.de/electronic/soft/scope.htm


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Old 06-16-2003, 11:38 AM
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Hey now I have 2 programs
Once I have my plane recorded I'll try them both to see if the outcome is the same.
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Old 06-16-2003, 03:44 PM
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there was a guy working on that, no news since..
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Old 06-17-2003, 06:04 PM
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Default Speed trap

Any Rifle Shooters out there?

I've been looking at the bullet chronographs and I'm not sure still how they actually work. I know they essentially see the bullets shadow, but how would you be able to use something like this in association with a flying aircraft. Sounds like an excellent concept for what we want to do if it is adaptable.

I do know the old "Speed master units" see the shadow of the plane against the sky in the same manner and use narrow slits to view straight up. The spread in width is pretty wide, but very narrow the direction of the A/C path of flight. They have an adjustable switch to calculate the speed based on 50', 100', or 300' as I recall.

Looking for someone to explain the "Bullet Chrongraph" who doesn't have limited knowledge like me.

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Old 06-18-2003, 12:00 AM
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Walt Hiester
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Default Speed Trap

Here's how I made a simple, accurate speed trap

I bought an inexpensive stop watch that had a large start/stop button on the side. I opened the s. watch and located the contacts for the switch. I then soldered two wires to the contact and then terminated the wires to a deans female plug which I epoxied the the side of the watch case. I made a cable up with speaker wire (220 feet long with a plug for the stop watch on one end and on the other end made up a handle out of a 6 inch piece of PVC pipe. On one end of the pipe I epoxied a push button switch. Here's how it works: plug the one end into the s. watch, lay out the wire until you have a true 200 feet of wire. I put wire wraps at each end of the 200 feet and left the extra 10 feet on each end for slack. To operate you need two people, one holds the zeroed s. watch, when the plane enters the trap he starts the watch and when the plane passes the end of the trap the other guy hits his switch and stops the watch. I find it more accurate if each person holds up his thumb with arm extended and uses it as a sight across the field. You can now get an extremely accurate timing of the plane through the trap. You can use any length wire, but the longer wire will increase the accuracy. You will be surprised how little the variance is with multiple passes. We tested the accuracy of this trap by timing a car going down our field at a steady 50 miles an hour and using an average of three passes were only off by 1 mph. This is very simple and it WORKS every time!!!! Any questions please let me know. Walt
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Old 06-18-2003, 12:09 AM
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Default Speed trap

That's a great idea Walt. I had a similar idea..take 2 stopwatches, zero both, set 2 guys a set distance apart. Start the 1st watch when the plane went by watch A, leave it running. Start the second watch when the plane goes by watch B, leave it running. Bring both watches to a single guy who stops both watches at the same time. Subtract the time of Watch B from the time of Watch A. This is your time thru the set distance. The advantage is no wire, the disadvantage is 2 watches.

It sounds simple enough, but I have tossed it out here a couple of times and nobody seems to give it much thought.
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Old 06-18-2003, 01:22 AM
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Chuck and Walt,

You both have great ideas on this. Actually Chuck I saw your posting went out and bought another stop watch to do this and it does work great! Actually it's the best system I've seen that you can do for less than $30.00.

I've been trying to get a setup that will work with the AMA for timing that is acceptable. What I'm trying to do is get Steve Kaluf at the AMA who in actually in charge of the FAI event records to open up various classes of straight line speed like 3.5cc 7.5cc 10cc 15cc and etc. Then actually hold speed events that are AMA sanctioned and start keeping records. One major hurdle is in the timing and anything they say over 150 mph has to be timed electronically and not hand activated to elininate the error variances inherit in such a system. I agree with them on that principal too.

The Russians hold the straight line speed record with a speed plane that is .60 size which has the wing rubberbanded down. believe it or not the record stands at 213.5 mph! How much do you think that rubberband stretched on pulling out of the dive? Plus you know how much drag there is with a rubberband hold down. 213.5 mph? I don't think so! I think somebody had a very nervous thumb. They used stop watches for timing. Anyway it stands at 213.5 like it or not. The new record holder must fly up wind and down wind at 217mph to break that record with a 10cc engine. Not likely to be done since their aren't any decent engines out there to fly on that are 10cc or less. On top of all this it has to be done on a 200 meter course. 600' is a mighty long run to keep the speed up through with an average of 217mph.

Anyway that's why I'm trying to find an acceptable electronically activated timing device. It would be fun to have several events for speed competition where we could get together for national records in different classes of speed planes.

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Old 06-18-2003, 01:38 AM
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Yeah, there has to be some sort of electric beam something out there to use. Drag races have a great system, but it uses a light beam that has to be broken with the front edge of the front tire..just too hard to hit with a plane.

I figure to just try to get as great a distance as possible to help the ratio of time in the trap to clock click error. 660ft seems about right, and is right on the 200meter FAI length. Of course I'm not trying to set a verifiable record, just get a clue as to my speed.
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Old 06-18-2003, 01:45 AM
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Chuck and Walt,

You both have great ideas on this. Actually Chuck I saw your posting went out and bought another stop watch to do this and it does work great! Actually it's the best system I've seen that you can do for less than $30.00.

I've been trying to get a setup that will work with the AMA for timing that is acceptable. What I'm trying to do is get Steve Kaluf at the AMA who in actually in charge of the FAI event records to open up various classes of straight line speed like 3.5cc 7.5cc 10cc 15cc and etc. Then actually hold speed events that are AMA sanctioned and start keeping records. One major hurdle is in the timing and anything they say over 150 mph has to be timed electronically and not hand activated to elininate the error variances inherit in such a system. I agree with them on that principal too.

The Russians hold the straight line speed record with a speed plane that is .60 size which has the wing rubberbanded down. believe it or not the record stands at 213.5 mph! How much do you think that rubberband stretched on pulling out of the dive? Plus you know how much drag there is with a rubberband hold down. 213.5 mph? I don't think so! I think somebody had a very nervous thumb. They used stop watches for timing. Anyway it stands at 213.5 like it or not. The new record holder must fly up wind and down wind at 217mph to break that record with a 10cc engine. Not likely to be done since their aren't any decent engines out there to fly on that are 10cc or less. On top of all this it has to be done on a 200 meter course. 600' is a mighty long run to keep the speed up through with an average of 217mph.

Anyway that's why I'm trying to find an acceptable electronically activated timing device. It would be fun to have several events for speed competition where we could get together for national records in different classes of speed planes.

Blue Skyy
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Old 06-18-2003, 01:49 PM
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I used the stopwatch before, and now I was looking for a way to verify those measurements

I agree at the point that an international way of measurement should been made, to make a speed event possible.
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Old 06-20-2003, 07:11 PM
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Hi all,

I have been playing around with the doppler speed program for about a week and have had pretty good success measuring speed and in-flight rpm at our field. Comparing my figures with a radar gun on the same planes generally agreed within 2 mph, as long as the flight path was straight and level (not coming out of a dive, etc), and people weren't running up their loud planes in the pits behind me (those unmuffled YS 91 4 strokes on 30% nitro are LOUD!)

I had some fun today downloading audio files of the 1999 Unlimited Gold Reno race (you can find them here: http://www.pylon1.com/multimedia/reno99/ ) This particular file was of Dreadnaught, Dago Red and Strega passing by on lap 2. I don't know what order they passed, but the doppler analysis gave me 482.8 mph @2894 rpm, 496.1 mph @ 2827 rpm and 467.6 mph @ 2764 rpm for the first 3 planes to pass the microphone. I wonder if these figures are representative of these unlimited racers (considering that the Rare Bear speed record is 532 mph running 2900+ rpm).
I would be curious if anyone can replicate these numbers. I made the assumption that the air temp at Reno on Sept 19, 1999 was approx 30 C and I used a correction factor of 2 for the microphone placement (seemed to give most realistic speeds).

I have been trying to figure out how to load all the software onto my Compaq IPAQ 5455 pocket PC and record thru the built-in mic and then analyze the files while still standing on the flight line! However, the few spectrum analyzer demos available for the PocketPC2002 platform and are too frustrating to use to measure the approaching and departing freq shifts. Does anyone know of a good spectrum analyzer for the IPAQ's?

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Old 06-20-2003, 09:03 PM
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i've always used a correction factor of 10, it was what i was told, but i have no idea what it corrects for. im glad you got good results. as for the low speeds, these are race conditions, and you cant go as fast as an all out speed record.
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