Labradar

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Trevor Rhodes
Posts: 148
Joined: Mon Feb 03, 2014 8:31 pm
Location: Woodbrook Vic.

Labradar

#1 Postby Trevor Rhodes » Wed Mar 27, 2019 7:44 pm

I find my labradar l can check speeds one day then next day same time and temperature speeds are 20fps different. Do any one else have this problem?

ben_g
Posts: 166
Joined: Sun Apr 24, 2016 7:37 pm

Re: Labradar

#2 Postby ben_g » Wed Mar 27, 2019 10:11 pm

Hi Trev.

I do not own a lab radar. But have used them and being a sonographer who performs Doppler ultrasounds all day everyday I can tell you that Doppler velocity readings will be dependant on the lab radar being positioned as close to the barrel as feasible and the radar being aligned (ie aimed at the target) as best as possible to reduce any angle difference between radar beam and bullet path.

Any angle between the flight of the bullet and the line of the radar beam will induce error. The greater the angle difference the lower your velocities will read. If you know the angle a correction can be made, but the greater the angle the less resolution you have.

I would experiment with intentionally angling the labradar a little off axis one day and see what difference you get.

Remember angling side to side AND up down will lead to errors

AlanF
Posts: 6909
Joined: Wed Jun 15, 2005 8:22 pm
Location: Maffra, Vic

Re: Labradar

#3 Postby AlanF » Thu Mar 28, 2019 5:44 am

And there are other possibilities independent of the Labradar e.g. did both sessions start with a clean cold barrel, was the rate of fire about the same?

Trevor Rhodes
Posts: 148
Joined: Mon Feb 03, 2014 8:31 pm
Location: Woodbrook Vic.

Re: Labradar

#4 Postby Trevor Rhodes » Thu Mar 28, 2019 6:41 am

AlanF wrote:And there are other possibilities independent of the Labradar e.g. did both sessions start with a clean cold barrel, was the rate of fire about the same?

Yes Alan i try to repeat each testing exactly the same and not just 2 sessions. l fired 3 fouling shots then shot a minute apart.

Trevor Rhodes
Posts: 148
Joined: Mon Feb 03, 2014 8:31 pm
Location: Woodbrook Vic.

Re: Labradar

#5 Postby Trevor Rhodes » Thu Mar 28, 2019 6:45 am

ben_g wrote:Hi Trev.

I do not own a lab radar. But have used them and being a sonographer who performs Doppler ultrasounds all day everyday I can tell you that Doppler velocity readings will be dependant on the lab radar being positioned as close to the barrel as feasible and the radar being aligned (ie aimed at the target) as best as possible to reduce any angle difference between radar beam and bullet path.

Any angle between the flight of the bullet and the line of the radar beam will induce error. The greater the angle difference the lower your velocities will read. If you know the angle a correction can be made, but the greater the angle the less resolution you have.

I would experiment with intentionally angling the labradar a little off axis one day and see what difference you get.

Remember angling side to side AND up down will lead to errors

Ben you might have something here, the angle tilt up and down on the labradar.

6.5x55ai
Posts: 201
Joined: Mon Mar 18, 2013 4:21 pm
Location: Waikato NZ (Ex Tyabb)

Re: Labradar

#6 Postby 6.5x55ai » Thu Mar 28, 2019 12:48 pm

How many bars on the bar graph on the left hand side of the screen are you typically getting? Low bar count indicates poor alignment and affects the tracking of the projectile.

I am not happy unless I get 4 or 5 (max) bars. If I don't get 4 or 5 with the 1st shot I recheck the alignment thru the sighting notch. Achieving accurate alignment is one of the poor points of the Labradar.

Some people have 3 D printed aiming devices that fit over the notch to make aligning easier. I use a 223 case with the primer pocket drilled out. It sits nicely in the notch.

You can also check the raw data (cannot be done on the range though) and compare where the projectile is first detected. Maybe some differences will show up there which may point to an alignment issue. Will also tell you signal strength as the projectile goes down the line.

I also set mine up exactly the same distance each time out to one side the barrel and the same height.

When I got my LR I checked it against a Magnetospeed and there was only very low fps differences.


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