S3HD

My Feedback: (1)

Spent all day at the Toledo show yesterday. Met Selwyn, and purchased 2 JR8411's for my Whiplash at his great price. He's a very nice chap. The servos were brand new, in the factory sealed plastic containers. The real deal.
Looked around for sydclement all day, and when I wasn't looking, ran into him as I was just about to leave the show. He's a very friendly gentleman too. Syd showed me this super small GPS unit that will record max speed - sounds like just the ticket for onboard speed readings. He said to write if I ever need help or have questions - like so many of the wonderful folks in this hobby.
Toledo was as good or better than the only other time I went 2 years ago. I spent all my allocated funds, and then some.
I don't think most people need to spend more than one whole day there. (If you do, you better brings lotsa $$$, there are too many great things to buy!)
There was a guy there with a giant scale tank that had a 25HP Koehler engine in it - for sale: $35K!
The other giant scale planes were awesome as usual.
Met and thanked Dub Jett for his help with my Jett 50 BSE FIRE.
I highly recommend attending this show at least once in your modeling hobby days - kinda like I think everybody should go to the Oshkosh EAA Fly-In at least once as well.
I'll go again.

sydclement

My Feedback: (1)

Toledo was a good one this year, I agree..
Thanks S3HD. To bad it couldn't have been longer.
I'll let you know when I get ready to test the GPS.
Sure works great on the dash of my van..

Syd

Blue Skyy

My Feedback: (3)

What model GPS were you looking at? Garmin Etrax, or did you run across something smaller?

Blue Skyy

sydclement

My Feedback: (1)

Blu Sky:
It's the Garmin Geko 201. Bought it at getagps.com
and is about the smallest complete unit on the market.
Pull the 2 ea. AAA batteries out and hook up a small
single cell litho-polli and you end up at less than
2 & 1/2 oz. Plan to tie it down between the fins
on the Whiplash...
Hope it ends all the arguments about measuring
the speed of these small deltas.
They list for $150.00 with a getagps.com price
of $116.00. Sure less expensive than a radar gun...

Syd

S3HD

My Feedback: (1)

I found the Garmin Geko 101 at:http://www.thegpsstore.com The price is $99.95
"getgps.com" didn't work for me for some reason.

This unit only measures speed up to 999mph! Hope that's fast enough! Ha!

BruceDana

The controversy will still exist. Here is why...

The specs on the Geko are:

update rate: 1 second
position: <15 meters, 95% of the time - Subject to accuracy degradation to 100m 2DRMS under the U.S. Department of Defense-imposed Selective Availability Program.

With the war going on, SA is going to make these units very unreliable for instantaneous position updates. Since velocity is calculated as distance (position fix 2 - position fix 1) over time, and your distance can be off by as much as 200 meters between any 1 second time interval, how can this be relied upon?

Even without SA, the position(s) could be as bad as 30 meters or more (you are only sure it is less than 30 meters 95% of the time), which translates to a speed in error of up to 67 miles per hour under ideal conditions.

Unless you were travelling in a relatively straight line where repetitious observations could be made, the errors are just too random to make any reliable conclusions (how many seconds can you fly a straight line at 150+ mph to get good readings)?

Blue Skyy

My Feedback: (3)

Brucedana,

What do you suggest then?

Blue Skyy

Blue Skyy

My Feedback: (3)

sydclement,

Thanks for your input on the GPS, Obviously a gps reading is going to be a lot more accurate than a wild guess. I hadn't seen the Gecko yet, only the E-trax version. Thanks for bringing this to my attention. Lithium is certainly the way to go on this too.


Blue Skyy

sydclement

My Feedback: (1)

Bruce;
I under stand what you sent, the war effort and the
update time but when its all said and done I was
going 85 MPH on the Pa. Turnpike coming home
yesterday and my car speedometter was reading
84.5 MPH. The GETO 201 was holding the 85 MPH
and updating the heading very well.

Thats good enough for me to try some runs with
the 201 mounted on the Whiplash.

The max stored speed on the 201 should get it
averaged out..

Syd

jlong34016

My Feedback: (1)

This has been discussed before on here. Its not the same as driving in your car at near constant speed in a straight line for hours at a time. The last data posted by someone using one of these small units varied by several hundred miles per hour. He figured he would throw out the highs and lows and keep the middle figures. Voodoo. A jetcat user was claiming very accurate and precise data with the built in unit. However no data was ever posted. Lets see what data comes from this unit in flight. Maybe good, may be not. Time will tell. For now radar is the best i have seen.

Mike Connor

My Feedback: (5)

Couldn't you simulate an aircraft path in your car? How about a large mt parking lot. It seems like I remember the speeds being fairly accurate during turns or even driving a clover leaf.

jlong34016

My Feedback: (1)

What kind of car do you drive? I dont think you could simulate an airplane flight of a few seconds at 200 mph. Even in a full scale plane these units work just fine. But nothing matches the acceleration of these models and the course is relativley short.

Mike Connor

My Feedback: (5)

I didn't think accuracy degradation was because of the speed being traveled. I thought course changes were the big problem. You could fly a half mile ovel pattern with out significant speed changes. This would be easy to simulate in a car but at lower speeds then a model.

While I doubt the accuracy would be good enough for the record books, this test may let you know if it is good enough for ball park fugures.

jlong34016

My Feedback: (1)

I was referring to acceleration as changing direction at constant velosity.
Only way to find out it to try it. Looking forward to results. If its good to _+ 5 mph its worth it.

Dustflyer

My Feedback: (13)

Another great Toledo show. Seemed like the crowd was a bit smaller than last year. I was waiting in line when the doors opened at 9AM and had pretty much seen everything on the main show floor by 12. For the first time in a few years I could actually get up to the displays to buy stuff or talk to the exhibitors.

Dubb Jett had some great show prices on his engines so I ordered one of his new 60 BSE FIRE engines that is the same size as the 50. He also offers it as a 65 but after discussing it we decided the 60 was the best way to go. Today I sent him 9X10 and 10X10 props for tuning.

I am hoping this engine will be just the ticket for a Patriot or Whiplash. Can't wait to see what I get back.

Have some Magnum 15 and 20 percent fuel I can't wait to try out.
My buddy Syd had some great results with it so I will have to try it for myself.

Hey Syd, was looking for you at Toledo! I'll be off next week and the weather should be nice for a change. Maybe we can get together!

Will call ya...

BruceDana

The GPS units compute accurate velocity in "steady state." The R/C airplane is anything but.

There are posts on these boards about using doppler shift to determine speed and RPM. Has anyone built a speed trap with accoustical switches?

The easiest way I can think of is use a camcorder (video).
Video is accurate if you have a frame of reference in the scene shot by the video. Say you erected two markers spaced a measured fixed distance apart near the center and parallel with the flightpath, then shot video of the aircraft passing through the scene from a fixed point offset a known distance perpedicular to the line created by the two markers. (the reason for the fixed point offsett perpedicular midway down the flightpath is to account for the "parallax" effect that the plane will appear to travel just a little further than it really has.

When the video is captured at a know framerate (say 30 frames per second which is typical of most capture/conversion software) using your computer, you could count the frames (thus measuring the time) it takes to traverse the known distance. There you have it, reliable measure of speed with the picture evidence to prove it.

At those framerates (30fps), a 200 MPH plane would traverse 293 feet/ sec. or 9.78 feet per frame. A good distance then would be to place markers spaced 200' apart (if you count 20 frames your video at 30 fps, you are going about 200 MPH).

jlong34016

My Feedback: (1)

I have a jett fire 60 but not the bse. I have not ran it since dubb reworked it. Did he tell you what to expect with the 9x10? I know its got the power but im not convinced it can turn the rpms. So far the best numbers i have seen on here are for the destroked jett fire 50 (a jett fire 45).

Dustflyer

My Feedback: (13)

jlong,

Nope, he really has no idea what it will do. I'm one of the few guys who likes to turn high pitch props with Jett's so it's kind of an experiment for Dubb. I plan to put the engine in my Whiplash for starters. I'll let you know what kind of rpm's I get.