(Yet another) Attempt to make sense of gyro angles - Page 3

Von Due · 02-28-17, 05:28 AM

Just noticed something peculiar.

I set up the gyro for a 90 degree turn. Which side doesn't matter.

With the auto update on, I make sure the periscope doesn't move and that nothing else on the TDC is altered. Still there is some small movement for the gyro angle in rough weather. With the auto update off, I couldn't notice any change in gyro angle.

This is odd indeed and I'm wondering if the reference points for a fireing solution are floating around much like the bridge/deck gun sight cameras are not fixed to what they should be fixed to. The end effect is, the SH3 submarine might very well have its torpedo tubes not attached to the submarine at all but floating around freely in proximity of the submarine. In that case, all bets are off and angled shots would be impossible to work out.

makman94 · 02-28-17, 10:18 AM

Quote:

Originally Posted by Von Due

..... the challenge is to find out exactly how to find the lead angle as seen from the periscope.

as i told you the ''broken tdc methods'' are for those who doesn't want to use the tdc. i also said that are not taking in account the parallax correction so expect inaccuracies at close shots. these methods work fine at long shots.they are not EXACTLY at the point you aiming just becuase the parallax is not in play but at long shots you hit the target. (i have made many many shots with success becuase the difference is not so critical).
But , i see what you are aftering at , and for extreme accuracy these methods are not for you.
The best accuracy you can get,as things are, is to use sh3's tdc becuase it is taking in account the parallax correction.i am afraid that without the use of sh3's tdc you will not be able to get extreme accuracy at your shots becuase it is impossible to solve the firing problem without the use of a computer.there is no single formula for giving you the shooting bearing with the parallax correction in play.
trying to find a workaround for the shooting bearing (with parallax in play) is the same problem with a workaround for getting the gyroangle and this is just not possible without a computer.

my two cents though, i will be huppy if i proved wrong

Von Due · 03-01-17, 04:52 PM

Test procedure and results so far:

I mark on the map a representation of the periscope.

Due north of this mark, 135-136 meters north I mark the advance line for a 90* gyro angle. This line is extended west and east so that it intersects the 87.4* and 272.6* marks at the 3000 meters circle on Pato's bearing tool.

I fired torpedos at slow speed setting with 90* turns and timed when the torpedo reached each of the 100 meter marks out to 3000 meters.

Plotting the range from periscope vs time, I did a linear regression and found the expressions for torpedo run time for 30kts, 40 kts and 44 kts for distances between 200 and 3000 meters from the periscope.

t(30) = 0.06543472906*R + 1.683743842
t(40) = 0.0490760468*R + 1.262807882
t(44) = 0.044614588*R + 1.148007165

These regressions had an r^2 apprx = 0.9999 which is very good. Still it should be mentioned that the times can be off by apprx 1 second but for targets 70 meters long, 1 second is within limits even for target speeds of 12 kts.

I then drew a line L from the periscope mark to the advance line and used the distance from the periscope in the above equations to find run time. I noted down the true bearing of this line.

Set target speed to zero in the TDC, and adjusted the range until the attack map displayed the time I calculated while keeping the gyro angle locked at 90*, the actual periscope bearing now matched the measured true bearing of L

I calculated how far the target would travel at 8 kts before reaching the intercept point and drew the target course line for this calculated distance, to find the aim point.

Now I drew the lead angle line from the perscope to the aim point and measured the true bearing to get the lead angle bearing for the periscope.

This bearing did NOT match the TDC suggestion. The two disagreed by several degrees.

I will attempt these manual plots for 90* shots and see if they will give me consistent results.
After setting distance and gyro angle, I will disengage the auto update and set the perscope to the measured bearings.

03-01-17, 04:52 PM	#33
Von Due Sea Lord Join Date: Jul 2012 Posts: 1,690 Downloads: 30 Uploads: 0	Test procedure and results so far: I mark on the map a representation of the periscope. Due north of this mark, 135-136 meters north I mark the advance line for a 90* gyro angle. This line is extended west and east so that it intersects the 87.4* and 272.6* marks at the 3000 meters circle on Pato's bearing tool. I fired torpedos at slow speed setting with 90* turns and timed when the torpedo reached each of the 100 meter marks out to 3000 meters. Plotting the range from periscope vs time, I did a linear regression and found the expressions for torpedo run time for 30kts, 40 kts and 44 kts for distances between 200 and 3000 meters from the periscope. t(30) = 0.06543472906R + 1.683743842 t(40) = 0.0490760468R + 1.262807882 t(44) = 0.044614588R + 1.148007165 These regressions had an r^2 apprx = 0.9999 which is very good. Still it should be mentioned that the times can be off by apprx 1 second but for targets 70 meters long, 1 second is within limits even for target speeds of 12 kts. I then drew a line L from the periscope mark to the advance line and used the distance from the periscope in the above equations to find run time. I noted down the true bearing of this line. Set target speed to zero in the TDC, and adjusted the range until the attack map displayed the time I calculated while keeping the gyro angle locked at 90, the actual periscope bearing now matched the measured true bearing of L I calculated how far the target would travel at 8 kts before reaching the intercept point and drew the target course line for this calculated distance, to find the aim point. Now I drew the lead angle line from the perscope to the aim point and measured the true bearing to get the lead angle bearing for the periscope. This bearing did NOT match the TDC suggestion. The two disagreed by several degrees. I will attempt these manual plots for 90* shots and see if they will give me consistent results. After setting distance and gyro angle, I will disengage the auto update and set the perscope to the measured bearings. Last edited by Von Due; 03-01-17 at 05:04 PM.

02-28-17, 05:28 AM	#31
Von Due Sea Lord Join Date: Jul 2012 Posts: 1,690 Downloads: 30 Uploads: 0	Just noticed something peculiar. I set up the gyro for a 90 degree turn. Which side doesn't matter. With the auto update on, I make sure the periscope doesn't move and that nothing else on the TDC is altered. Still there is some small movement for the gyro angle in rough weather. With the auto update off, I couldn't notice any change in gyro angle. This is odd indeed and I'm wondering if the reference points for a fireing solution are floating around much like the bridge/deck gun sight cameras are not fixed to what they should be fixed to. The end effect is, the SH3 submarine might very well have its torpedo tubes not attached to the submarine at all but floating around freely in proximity of the submarine. In that case, all bets are off and angled shots would be impossible to work out.