Albacore continued

[greenman407]

One thing that I have noticed is that the difference in turning ability between the single prop Albacore and the dual prop Albacore is that the new configuration doesnt turn on a dime like the previous configuration. Now it turns on a Quarter. Perhaps and most likely because of the pivot point, which I would think are the stern planes is now a greater distance from the propellers. The Props are further away. The distance went from 1" to 3". So now we have an overall length of 42 1/2".

[greenman407]

Look at that Dashing, handsome Gent. This is my youngest, Nathan. Part time camera man for me. Poor Kid. Cares nothing for this Hobby, he just humurs the old man. He does enjoy driving my 1/8 scale gas buggy. There is still hope for him yet.

[greenman407]

A Week! Wow, you got a severe case! Oh well, you can catch up on the reruns of Space 1999 and Star Trek

[He Who Shall Not Be Named]

Good report, Mark. Good luck.

This damned flu has me out of the shop for nearly a week now!

David

[greenman407]

OK, so to recap what has transpired. In order to get the Pitch control to work, it became necessary to install it in the forward dry space. This because of the vibrations being picked up in the rear compartment. After installation in the forward compartment , the Subdriver and APC worked well, sitting on the bench. After installation of the subdriver into the submarine, new vibrations were entered into the equation. Two propellers and my home made twin shaft produced vibrations that the Pitch controller picked up. The solution to this was to reduce the sensitivity of the pitch control, in this case , the ADF2. Since its maiden voyage was successful but the second voyage was not, it seems most likely that this particular ADF2 changes sensitivity settings on its own. Therefore, as part of the on site, pre sail checklist, a new req. for this sub is to check and reset that setting. No Rocket science here. Tuesday, January 1st will be my next opportunity to test it and confirm. I am also hoping to get some better video of her that day.

[greenman407]

Thanks Dave. I think you missed my earlier post about discovering that the ADF2 had, by itself, changed its sensitivity setting. I turned it back down to where it was before and the flutter is gone. Got to get it back into the water to make sure that was it. Thanks.

[He Who Shall Not Be Named]

Have you changed the 'sensitivity' of your ADF2 yet, Mark?


Every item that has the property of mass has a natural resonate frequency and harmonics of that about which that mass readily oscillates if excited. A system of different masses rigidly held together (no such thing, I know ... humor me, damit!) has a specific natural frequency unique to that system. Look on your ALBACORE as such a system. You've got a regenerative system vibration feeding the sensor of the ADF2. You're in a feed-back loop, pal!


We don't kneed to know what the frequency is... anyway, we don't know how to measure it (well, maybe Andy and Norbert do). But, we do know that by changing the mechanics of the system: rigidity-elasticity of the system (your bubble-wrap for example); distance of the sensor from the center of rotation (jamming the poor ADF2 into the bow compartment); circuit response time, or circuit response amplitude (sensitivity setting), we can eventually create the environment where the sensor response to system vibration is degenerative rather than regenerative. The objective is to get away from system induced oscillations. Change one variable at a time and test, observe, and analise. Do that till the boat stops chasing its tail at all throttle positions. (Easily said!)


You are now at that happy-space where all you need suffer is pilot induced oscillations.

David

[MFR1964]

Mark,

Remark noticed about the ADF, i'll check her up tomorrow, and yes i still have the instructions, i use a different system to clamp the SD inside the 212, but your remark about the soft rubber is right, if compressed too much the effect will be gone.

Manfred.

[greenman407]

The problem with soft rubber to isolate the subdriver from the hull is that after you rubber band your subdriver down so that it wont move, your soft rubber has collapsed into hard rubber. Unless I devise a way to hold it in place by other means. (Evil laugh) as he slowly fades away.

[greenman407]

NEWS FLASH!! NEWS FLASH! I feel so much better............................................ .................................................. .......................OH! Why do I feel so much better? I checked the sensitivity setting on the ADF2 and found that ,somehow it had , apparently reset itself to setting (3) three, for the most sensitive. Preliminary tests on my work bench show that if I back it down to setting one, it doesnt pick up any vibrations. I posted a note on KMC designs section and see what Kevins take is on this. Do you have to reset the sensitivity setting every time you power it up? was my query. Manfred , you might check your setting on your ADF2. If you have lost your instructions, I can post it here tomorrow.

[greenman407]

Thanks Manfred, perhaps. I think that the props are not balanced, setting up a vibration. At certain rpms there is barely any movement of the planes at all, and at other rpms,WILD GYRATIONS! This fix will probably envolve a lot of little things together.

[greenman407]

I just tried bubble wrapping the shelf but by the time you put the endcap back on you have the battery wires jammed against the shelf, negating your attempt at isolation. I wonder if there is an APC out there that is not so affected by vibration?

[MFR1964]

Mark,

You can also try to make some soft rubber insulation between the hull and your SD, i removed the dogbone and replaced it by a silicone hose to couple the SD to the shaft, lesser noise and offcourse lesser vibrations.


Manfred.

[greenman407]

Manfred, thanks for the feedback. I havent noticed any change in gear noise. Inside the front compartment, on the back of the ballast bulkhead, there is a screw in the center of the bulkhead that is touching the panel that the pitch control is mounted to. Perhaps its transferring some vibrations. Ill probably take the screw out and seal the hole up and then try to insulate that panel from everything else.

[MFR1964]

Mark,

I've encountered the same issue with the 212, but allready had from the start the ADF2 inside the front compartment, on the bench it will pick up the vibrations as expected, normally it would be less when in the water.
Insulating the ADF with some bubble rap could be a solution, however it maybe catches up a oscillating vibration from your gears running both shafts, did the sound from your gears alter from your previous runs?
For me the only solution was, reduction of the topspeed by 60%, which gives me a stable run at the scopes, higher speeds means more yanking at the sticks by hand, it's possible, but the easy ride is gone.

Manfred.