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How fast do they go?

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How fast do they go?

Postby Ramius-II » Fri Mar 28, 2014 4:47 pm

Hi All!
Just wondering if any knows the speed of our model subs?
Such as, has anyone used something like a GPS system to measure the speed in actual Miles Per Hour and not scale speed?

Thanks, Ed
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Re: How fast do they go?

Postby Sub culture » Fri Mar 28, 2014 5:33 pm

I've used Eagletree loggers. Chiefly for current draw and measuring RPM. The ability to measure these aspects with the vehicle whilst under way is an absolute boon of modern microprocessor technology.

I do have a plug-in GPS module, which can measure speed, but haven't used that part on a sub, only in aeroplanes, cars and boats. Sadly the signal won't penetrate through water, which would mean surface running on, or fixing it on a separate pontoon.

You can always measure speed the old fashioned way with a stop watch timing over a measured section of pond/lake/pool. Accurate enough for me.
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Re: How fast do they go?

Postby Ramius-II » Fri Mar 28, 2014 7:02 pm

Thanks Subculture!
Eagletree uses a pitot tube system for speed for both airplanes and boats and the output from their sensor is in actual MPH as in your car. The lowest speed is 9 MPH and top speed is 350 MPH way too fast for our subs. Their pressure sensor is a 0-2 psi sensor. My guess is our subs may max out at maybe 15 MPH? Just thought maybe someone had actually measured the speed either on the surface or underwater?

Best, Ed
Just one more wire!
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Re: How fast do they go?

Postby Sub culture » Sat Mar 29, 2014 1:45 pm

Most scale subs tend to max out at less than half that figure.

My Eagletree can measure speed via pressure as you said and also via GPS, which of course gives true ground speed for aeroplanes.

I tend to use it mostly for measuring RPM and wattage, when trying different prop/motor combinations.
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Re: How fast do they go?

Postby Ramius-II » Sun Mar 30, 2014 2:52 pm

Thanks!
Have you used the pressure sensor on your sub? The reason I ask is that the eagletree pressure system will only start reading at 9MPH! If our subs max out at 7 MPH then it would seem you cannot get any reading? Maybe next time you are doing a test you could use your GPS? The way I am looking at this is if a 0-2 psi sensor shows 350 MPH at 2 psi full scale then at 1 psi it would be maybe half that speed? So:
PSI MPH
1.00 = 175.00
0.50 = 87.50
0.30 = 26.25
0.15 = 3.94
0.07 = 0.28
0.03 = 0.01
Just trying to use a correct pressure sensor.

Best, Ed
Just one more wire!
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Re: How fast do they go?

Postby Scott T » Sun Mar 30, 2014 9:54 pm

Is there a phone app for runners that records distance and speed you could put on a phone and drive around on your sub?

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Re: How fast do they go?

Postby Ramius-II » Tue Apr 01, 2014 9:15 am

I wish that there were such an app! I don't have a sub I can put in the water yet which is why I am asking the good people here.

Best, Ed
Just one more wire!
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Re: How fast do they go?

Postby Sub culture » Tue Apr 01, 2014 9:24 am

No I haven't tried a pressure sensor with the eagle tree on a submarine.
'Why are you staring at an empty pond?'

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