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Old Jun 10, 2013, 02:50 PM
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Speed measuring devices

I'm looking at getting me a different kind of speed measurement equipment.
Today I use a GPS but it seems that when things go a little faster the GPS does not work god enough.

What works and what does not ?
Is a pitot tube is best for speed measurement ?

Of course, I want a small and light measuring sensor. It may well be compatible with Graupners Hott systems.

I have looked at:
-www.sm-modellbau.de unilog2 with the pitot tube sensor
-www.cb-elektronics.de HSS-460 pitot tube sensor

Are there any other good options ?
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Old Jun 10, 2013, 04:20 PM
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Hi pednor,

Pitot tubes are very accurate provided they are installed correctly. Remember they measure airspeed not ground speed - not sure if that is important to you. Eagle Tree also do a very small Pitot tube:
http://www3.towerhobbies.com/cgi-bin...?&I=LXVEU1&P=M

Radar guns can be accurate, the downside is the plane tends to be flying at the measurer and with certain airframes (e.g. pylon) they are hard to get a front on reading due to their very small frontal area.

Doppler can be also very accurate, so long as you get a nice clean pass.
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Old Jun 10, 2013, 07:04 PM
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Wavoscope doppler works well if you have a screamer for a good sound file but you need video of the passes up and down wind to average. RCSpeedo is great on a smart phone too!
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Old Jun 11, 2013, 02:20 AM
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video of a good pass, put it here, we can doppler it, clean, easy, reliable and cheap
No need putting in stuff in plane and cut holes just to get the speed, as doppler will get you that within1%...

the only downside to doppler is it cant analyze sound from bigger props good, example a 10x23 prop in geared combo is impossible, but I think 7x10 is ok..
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Old Jun 11, 2013, 06:16 PM
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Sebbe,
Geared 10x20+ does make it more difficult, but if the camera is on a tripod and you fly right over it, you can get a measurement. Helps if there's no background noise also.
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Old Jun 12, 2013, 05:35 AM
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Quote:
Originally Posted by Steve C View Post
Sebbe,
Geared 10x20+ does make it more difficult, but if the camera is on a tripod and you fly right over it, you can get a measurement. Helps if there's no background noise also.
interesting, Im sure its possible, but the curve will be weak... never sucseded witn that big props... you are right, if there is dead silence around it is more chance get better readings...
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Old Jun 14, 2013, 10:49 PM
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We use a Stalker Pro gun around here.
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Old Jun 15, 2013, 03:50 PM
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Radar can be risky. I was flying a P5 and it tried to tuck in to the ground at 214mph. With the plane banked slightly away, the tuck brought it way too close to us. I stopped aiming 200mph+ airplanes at my buddies after that.

Pitot can be great, but you need to verify it's accuracy with something else. I had one of the early ET systems and it was way off (showed slow). The ET guy said he could adjust it to make it show higher if I wanted.
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Old Jun 16, 2013, 12:22 AM
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Go with the Unilog2. The cheapest while most reliable option and fully integrated in your Hott/Jeti/Multiplex/Futaba telemetry.
With a measuring range of up to 450km/h its sufficient for most setups.
Cheers Stephan
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Old Jun 16, 2013, 12:30 AM
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Quote:
Originally Posted by schiwo1 View Post
Go with the Unilog2. The cheapest while most reliable option and fully integrated in your Hott/Jeti/Multiplex/Futaba telemetry.
With a measuring range of up to 450km/h its sufficient for most setups.
Cheers Stephan
If you read the first post, he already has unilog and he found the GPS to be not accurate. GPS does not appear to work well with high speed planes.
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Old Jun 16, 2013, 12:32 AM
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read again. He has a GPS, not the Unilog2.
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Old Jun 16, 2013, 03:17 AM
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If you want to impress with high speedreading numbers ,radar or doppler are ok,gps is even better cause it gives higher readings with lower power!

If you want to improve your setup and get the best out of your drive and plane go for
a proper logging system with pitot.

I use unilog 1

Yello
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Old Jun 16, 2013, 03:20 AM
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but doesent the unilog 2 has to be connected to some GPS to read speed? how does it work otherwise?

I think what savneo and many others are saying is: that any gps no matter what brand is not reliable in a fast rc plane..
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Old Jun 16, 2013, 03:49 AM
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Quote:
Originally Posted by sebbe View Post
but doesent the unilog 2 has to be connected to some GPS to read speed? how does it work otherwise?

I think what savneo and many others are saying is: that any gps no matter what brand is not reliable in a fast rc plane..
Speedmeasurement with unilog 1or 2 with pitot:
http://www.sm-modellbau.de/shop/prod...id=76&cPath=11

This system is used by the most competition pilots to setup their drives and planes.
You can easily see how changes effects power and speed , you also can compare acceleration and finaly you can compare efficiency of different prop and drivecombinatins.
You can even see differences in aerodynamical layout.

Accuracy is proven many times by comparing it to speedcup measurements and seem to be recent.
One user checked the calibration with profesional aircraft measurement and came out with about 3-4%.
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Old Jun 16, 2013, 08:56 AM
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I would rather not know the speed in my model then having that ugly pitot in the wing

Do a clean flight in a video, doppler will be as accurate if not even better..
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