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Who is John Galt? -
I see Bart has followed the same route as me, removed the stock conduit tube for a bigger one, this way you've got more room for cables, if i've seen right he also has placed his ADF in the front compartment away from al those pesty electronic noises and vibrations.<br />
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David, we europeans like to annoy you americans by altering a very good product into a perfect product, you teached us well.<br />
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ManfredI went undergroundComment
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Bart,<br />
<br />
If that's a SAS SD, you better hook up a hose to the inlet near your ADF inside the SD, and lead this to the lower part under the battery.<br />
Sometimes you can suck in some droplets of water stuck to the rubber of your inletvalve, not much, but enough to damage you electronics nearby, made inside my XXIII SAS SD a provision to catch up those droplets, works like a charm.<br />
<br />
Manfred.I went undergroundComment
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My intention was to post an “overall view” picture, so nobody would notice that I raped the SD.
Now that I’m busted I will tell the story behind it.
I did had to make some adaptions not because the SD wasn’t good enough but because circumstances left me with no choice.
I had already purchase some electronic parts before I ordered the SD an ESC’s for a brushless motor was such a thing lying around.
I took the SD apart to convert it to Brushless. It was a hard job to find a brushless motor with a 2.3mm shaft though, but I succeeded. Why I bothered? I did that because I wanted the reuse the max amount of the parts, and not jeopardize the design of the SD. I even managed to use the original bold holes for fasting the motor. There was no need to wide them up. I will run the motor at 50% max. as the SD was not designed to take the power of a 300W E-motor.
Also grinded out the slots of the servo carrier to take slightly longer servo’s but here again I had purchased them already.
No sweat so far, but here is the point where it got really messy.
I have a Subtech depth controller and a KM “depth cruiser” (DC). I tried to enclose both in the Fwd compartment along with the battery. I tried to squeeze all the necessary wires in the conduit tube but it didn’t work. I had to make a compromise, I would only use the DC as this is the smallest of the two devices. All the necessary wires fitted in the conduit tube this way.
Here comes the part that Manfred pointed out.
Everything was installed all tested to satisfaction until I turned on the pump, the servo witch was connected to the subtech ADF2 started to jitter. I tried everything I knew, ferrite cores,…… you name it I tried it (I HATE ELECTRICAL NOISE). I doubted the pump was the issue as it is filtered. I tried running the propulsion motor and guess what….. samesame……ADF2 servo started to jitter.
Normally brushless motors do not give any interference. So my conclusion is that the subtech ADF2 is very sensitive to noise.
I removed the ADF from the engine room pack, placed it 2inches away from the pack and the jittering stopped. You feel it coming I had to place the ADF in the fwd battery room…..feeding two additional servo cables trough the already cramped conduit tube…..that was impossible.
The only solution was to install a conduit tube with a larger diameter. So I lined up all the issues that I would come across:- Existing seals would not fit anymore
- I have to enlarge the holes in the bulkheads and drill holes off center from the existing holes, the servo to blow the ballast tank is to close.
- I have to dismantle the SD, without breaking anything
- Make a new conduit tube with a 8mm bore, without adding to much weight
- Provide a new sealing arrangement
- A larger conduit tube meant less ballast tank capacity resulting in an above waterline structure displacement that will be less.
I made a new crossover out of aluminum, started with an outside diameter of 10mm, and drilled a 8mm hole in it. Turned it down to an outside diameter of 9,5 mm. A hole of 9.5mm was drilled in both bulkheads eccentric from the existing ones. Next the new bores were partly drilled out to 12mm so they would take the new O-ring. Everything turned out well to my relief. Everything was re-assembled The water tightness was tested without remark.
The weight of new crossover was 5gr more than the original, the loss of displacement was also 5gr…..the total deviation of the “factory SD” is 10gr that’s 0.35 ounces. (yes I’m good too).
I also added a tray to the Fwd battery compartment so everything will be kept in the same place, in addition it is also used as a platform for the ADF2 and DC.
I’m not going to blow sunshine up his holiness arse , but the process of executing all a.m. works resulted in the fact that I dismantled almost the complete SD. I know craftsmanship when I see it, and I saw the result in every part I handled. And if you are not a CB like me you will buy all the necessary parts from the subdriver site everything will fit perfectly together.
But as I’m a SOB I don’t want to end this story with those words, so I will end it with Manfred’s quote.
Grtz,
BartLast edited by bwi 971; 02-08-2016, 03:56 PM.Practical wisdom is only to be learned in the school of experience.
"Samuel Smiles"Comment
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Some details of the ER arrangement
Grtz,
Bart
Practical wisdom is only to be learned in the school of experience.
"Samuel Smiles"Comment
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My hurt feelings aside ... what a wonderful job, Bart. You and your fellow partner in crime from the other side of the equator have taught me a thing or two over the years. Is is, very much, a two-way street we have here. You both took a good product and made it unreasonably good.
Now, that's what a WIP should look like, Bart: big pictures; call-outs within the pictures for clarity; and a classic problem identification- problem solution-fix presentation. An excellent job, sir.
Where did you get that clear plastic wrap you use to get all that wiring spaghetti under control? I like it.
Who is John Galt?Comment
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Bart, looks really good! Its been my experience that automatic pitch controls all seem to have one Big disadvantage, and that is they pick up mechanical vibrations from propellers, electric motors drive shafts even from a servo. By moving your APC up front youve distanced it from the source of the vibrations. However.......you may find that they come back. You may need to insulate the APC by mounting it on a bed of silicone or rubber or both. Also ive noticed that reducing the sensitivity of the APC helps tremendously. All of the submarines that I have do not need max sensitivity. In fact most of them run well on the least sensitive setting. Thats assuming that your APC is adjustable. I dont recognize that particular model of the Subtek APC. I dont know if you can adjust its sensitivity.IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!Comment
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Mark is right, we call that harmonics, we also have to account the fact we do our testing dry on the bench.<br />
The most ideal place to pick up vibrations, i would go for a foamrubber stand to imitate the surrounding water.<br />
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Manfred (european partner in crime)I went undergroundComment
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Grtz,
Bart
Practical wisdom is only to be learned in the school of experience.
"Samuel Smiles"Comment
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After installing all components x times, shortening all servo leads, installing 15 servo connectors,…..For the moment my sensitivity is on max..........so if the SOB servo start to jitter again...........I guarantee you will see a real flying sub
Serious now, I'm a newbie on this subject so all this advice is very useful thks I will keep it in mind.
Grtz,
Bart
Practical wisdom is only to be learned in the school of experience.
"Samuel Smiles"Comment
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Bart,<br />
<br />
<br />
First start on a low level sensitivity and work your way up.<br />
The moment you're getting jitter is the moment harmonics sets in, you can search like hell, but that's wasted time, it can be anything, starting with vibration from your drivetrain, electronic noise, voltage variations from your BEC, or much more.<br />
All you can do is using some soft rubber underneath your ADF and keep some slack into your cables, when wrapped tight they also transport vibrations to your ADF, when done, follow the same path with setting the sensitivity higher and higher, on more tip, place your SD on a soft surface, imitating that you are floating in the water.<br />
When the jitter starts again,go one step back, and see for the result, this setting will be the highest you can run, beware, in the water it can be totally different, but that you have to test live.<br />
<br />
Manfred.I went undergroundComment
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An observation about the angle-keeper 'jitter' issue. First my credentials:
I've operated a wide array of mechanical and 'solid state' sensor based angle-keepers. I've even constructed my own by modifying helicopter rate gyro amplifiers -- as instructed by Skip Assay. I know my way around these things. The jitters experienced -- once all possible electrical 'noise' has been mitigated -- is a consequence of the non-mechanical sensors used today -- most are air-bag accelerometers that measure the direction of movement and amount of acceleration of air within. I suspect that their velocity measurement is not linear to the change observed as a consequence of velocity change -- I bet if you scoped out these little accelerometer outputs you would find spikes rather than curves following velocity changes to the sensor. Over time those spikes translate to reasonable response curves. Kevin: Help!
These types (all the rage today) all get the jitters. Don't sweat it -- once the model is in the water, the water acts as a perfect damper (Ron Perrott's beautiful little SailCon featured a pendulum damped in an oil bath -- SMOOOOOTH!) and you'll see less jitter in the stern planes once you let it go.
The old mechanical (pendulum and liquid) angle keepers operate smooth as silk and only jitter because of servo, motor, and pump vibrations.
David
Last edited by He Who Shall Not Be Named; 02-09-2016, 08:28 PM.Who is John Galt?Comment
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Interesting stuff David.
I have Norbert bruggen's book "technik der u-boot modele" I studied it in the years before I actually started the akula project. I think it's a must have for beginners. All the things you must know are described in it. Even how to make angle keepers and depth keepers yourself.
He also mentioned the pendulum with two phototransistors and a diode, filled with oil to damp the oscillation. Wonderful stuff.
Probably everybody in this house has it in their collection.
grtz,
Bart
Practical wisdom is only to be learned in the school of experience.
"Samuel Smiles"Comment
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