speed recording
 

Hey all,

I am putting together a composite electric speed plane and need to know what is a good way to record maximum speed. I saw one device but it requires drilling holes in wing for air tubes. I rather not drill holes in this beautiful plane. I have heard some do it with handheld GPS units which are accurate but not sure how small they come and probably wont be an abundance of room inside sleek fuse. Any ideas?

Thanks

Z

RE: speed recording
 

I have read here on RCU about people using a GPS unit in their aircraft to record speed but do not remember the details. You might try a search for more details. Other then that you could use Doppler, radar or stop watches to get speed.

RE: speed recording
 

As far as I am aware (although I may not be fully aware, so set me straight if I'm not!) the refresh speed on GPS is not high enough to get a good speed reading at the speed/ distance equation that we would typically fly at. Interested in this problem too!

Z

RE: speed recording
 

I did read there are now small watches, not to pricey, that have gps and will record highest speed but havent found them in a search.

RE: speed recording
 

the gps is an iffy.. I had put a small Garmen gps in my GP minnow w/jett90lx. One one run I was full throttle high dives and a lot of hard banking the gps read 256mph. Then i did another run with no hard banking and some smaller dives that registered 163mph. Next run NO dives NO banking just a lot of straight and level it read 142mph all of these are MAX speed. It is hard to say but we think somehow the hard banking was throwing off the gps, and since it is measuring max speed a high enough dive will give you the 163mph.At 256 for a prop plane I know somethihng very very very bad would have happened(wings folding and massive flutter) LOL
That is my experience with the gps
Pete

RE: speed recording
 

good to know, sounds like that might not be the answer. i wonder who sells cheap radar guns <G>


Z

RE: speed recording
 

I had the same results as phjoker.I bought a Garmen fitness gps that we could use at the field in q500 and deltas.It seemed accurate a couple of times.But we got a lot of 250 and up readings.A few of us in our club are looking into chipping in on a radar gun.Unfortunately from what I've read anything that is going to be accurate isn't cheap.

RE: speed recording
 

What airframe are you building? You will find most cheap radar guns will not detect the smaller planes. The 'How Fast' device is probably the best and easiest device you can use and it's really small. It's also accurate. You don't have to drill holes in your wing... you could conceivably tape the tubes on temporarily.

A past article I showed on here about it on a really small (24" span) pylon plane.

http://www.rcuniverse.com/forum/m_63...tm.htm#6331929

RE: speed recording
 

Has anyone tried modifying this so that it transmits down to the ground the speed and can allow several passes with the speed being known each time.
Maybe a voice synthesizer on a computer would be the ideal and it could also record the data and show on the screen.

RE: speed recording
 

Don't forget the guy holding the radar gun gets "Danger Pay".

RE: speed recording
 

Does the doppler speed method work on electric aircraft ? I tried it with a gas turbine and found there were just too many frequencies to be able to pick the correct ones to compare. With gliders I have heard of people using an electric speaker to make a steady tone.
So much for silent flight :)

RE: speed recording
 

Yes, If they have a prop.

RE: speed recording
 

FWIW, I've used a small Garmin with success, but you have to do a couple of things. First, go into the programming and set the sampling interval to the minimum - I believe it is one second. Second, fly large race track laps. If you fly vertical maneuvers, you get crazy speed readings. Apparently the vertical resolution isn't sufficient to accurately calculate speed in the vertical. The "how fast" device is smaller and pretty cool, but with the gps you don't have to poke holes in your plane.

RE: speed recording
 

Someone figured it out for the How Fast Device. Simple, easy, effective. No poking holes in your plane.:D

http://www.rcgroups.com/forums/showthread.php?t=789142

RE: speed recording
 

I have the prospeed radar gun and it works great but it misses alot of passes when you get around 200+mph. I got it refurbished for around $450. I've never come across a less expensive gun that can consistently clock fast small planes.

RE: speed recording
 

Can I get model numbers?

RE: speed recording
 

I use the Garmin Foretrex 201, but other of the Garmin models may work. It has a lot of capabilities - can even download speed and position data to your computer. As I mentioned above, set the sampling interval to the minimum, fly big smooth race track laps, and avoid vertical maneuvers.

RE: speed recording
 

i got a sr 3600 sports radar gun it will clock planes but it seems like you have to get it real close to the gun. kind of scary having a 120 mph plane zip by real close to your head. i have clocked a few planes with it seem to work ok but not what i would have hoped for. i didn't think you would have to get that close. i am working on trying to set it up on a tripod and doing flybys with it on its constant setting. its not working out real well i am not as accurate bringing the plane to a target away from me then bringing the plane to me.

RE: speed recording
 

i got a sr 3600 sports radar gun it will clock planes but it seems like you have to get it real close to the gun. kind of scary having a 120 mph plane zip by real close to your head. i have clocked a few planes with it seemed to work ok but not what i would have hoped for. i didn't think you would have to get that close. i am working on trying to set it up on a tripod and doing flybys with it on its constant setting. its not working out real well i am not as accurate bringing the plane to a target away from me then bringing the plane to me.

RE: speed recording
 

The sports radar works best if you have a good one, and it is has remote-display capability.

That way you can set it up on a tripod, and the display will be visible from a safe distance.... rather than having to be in the line of flight.

Takes nerves of steel to sit there with something heading at you. eeek!

RE: speed recording
 

It is cool of you guys with GPS's to admit they get funky numbers. I was going to create a thread about it. We use GPS's in the real airplanes I fly and we learned about some variables (sattellite deviations, refresh rates, processing rates etc) that they often don't often like to advertise, most handhelds are for in your car, hiking, biking, etc.
That's why I bought a Prospeed radar gun. It has performed GREAT. What is the negative.......PRICE, the good radars cost a bit.
The eagle tree systems GPS that just came out looks to me to be the first one I have seen that may have addressed a lot of the GPS issues. I will probably get one.
BTW....I have no affiliation with Eagletree.

Erik