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Old Jun 24, 2013, 07:40 PM
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United States, NV, Las Vegas
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This is an area I will need to delve into someday. Thanks Tim, you rock!
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Old Jul 01, 2013, 03:38 PM
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Wichita, Kansas
Joined Jan 2004
276 Posts
Tim,

Where did you obtain your pressure bladder? Are you allowing the pressure build up from the expanding bladder to feed to the aft compartment or keeping it restricted to the forward compartment?

My hat is off to you. Your work here on the brushless motors proves once and for all that they DO have a place in the model submarine hobby. I really like the advantage of being able to eliminate the gear reduction completely, thus opening up a ton of room in the dry space. Also, a huge plus is the ability to program the throttle curve of these motors.

Well done, Tim!!!!

Matt
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Old Jul 01, 2013, 05:36 PM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
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Thor,

Quote:
Originally Posted by ThorDesign
brushless motors.. DO have a place in the model submarine hobby ..a huge plus is the ability to program the throttle curve...
I have always been a brushless bigot, i saw the writing on the wall when they first came out, but the throttle curve is only part of the answer, allowing me to setup a low end bias, giving me the ability to creep along, but the newer ESCs also have the governer which basically caps the top speed of the motor at a percentage of the motor's true capacity, as little as 10% of "real" top speed. there are many other benefits as well, including efficiency, and RFI noise. thanks to the chinese, cost is no longer an issue.

Quote:
Originally Posted by ThorDesign
Are you allowing the pressure build up from the expanding bladder...
there is a tiny 1/8" hole at the top of the endcap between the ballast tank section and the electronics section, so the pressure build-up is spread across the entire length of the WTC, but for "safety", if the bladder leaks, water won't get everywhere.

Quote:
Originally Posted by ThorDesign
Where did you obtain your pressure bladder?
the bladder itself is a very high-tech device, having taken millennia to perfect: r/c submarine bladder
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Old Jul 01, 2013, 06:00 PM
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Wichita, Kansas
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Thanks, Tim. Pretty ingenious use of party city!

Do you have any issues with the increased pressure bleeding out of the shaft cup seal when you submerge? That should be a one time occurrence resulting in a lower pressure in the WTC until you open it up.
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Old Jul 02, 2013, 12:13 PM
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United States, NV, Las Vegas
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Quote:
Originally Posted by tsenecal View Post
Thor,
the bladder itself is a very high-tech device, having taken millennia to perfect: r/c submarine bladder
LOL - funny!

There is merit in what you are offering here with the brushless motors. Can two censored motors be run off of one ESC? There is another sub I want to build, but know little about brushless motors.
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Old Jul 02, 2013, 02:50 PM
Submarines, etc.
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Arvada, Colorado
Joined May 2005
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Quote:
Originally Posted by tchalfant View Post
LOL - funny!

There is merit in what you are offering here with the brushless motors. Can two censored motors be run off of one ESC? There is another sub I want to build, but know little about brushless motors.
i've never tried it. i assume it shouldn't be done, whether the motor is sensored or sensorless...

sensored are using hall sensors to tell the esc what position the rotor is at, while the sensorless models use the emf wave to tell what position the rotor is at. in both cases duplicate but different info from two motors could confuse the esc. I have seen where model airplane guys have successfully done it on the bench with two sensorless motors with no load, but i have not seen that anyone has succeeded in the air, with the motors under load.

lets just say that for the sake of your wallet, with brushless motors, each motor needs its own esc.
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Old Jul 02, 2013, 02:56 PM
Submarines, etc.
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Arvada, Colorado
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Quote:
Originally Posted by ThorDesign View Post
Thanks, Tim. Pretty ingenious use of party city!

Do you have any issues with the increased pressure bleeding out of the shaft cup seal when you submerge? That should be a one time occurrence resulting in a lower pressure in the WTC until you open it up.
one of the pushrod seals was screwed up from initial assembly of the WTC (gouged it with the pushrod stuffing the rod through it), and its tiny cup seal had to be replaced. the main propshaft and other pushrod have not shown any propensity to leak. i do have the propshaft cup seal installed backwards, with the cup side of the seal pointing to the inside of the WTC. it is also a full blown simmering style seal, with the spring, not just a simple cup seal.
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Old Jul 03, 2013, 03:11 AM
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Philippines
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Nice.

Looks like it can also be modified into a vented tank.
BTW, Can you show the placement of your flotation foam.
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Old Jul 04, 2013, 11:16 AM
Submarines, etc.
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Arvada, Colorado
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foam and lead... 35 oz of lead, each front block of foam is about .5"x.5"x1.5", rear block is .5"x.5"x.75"
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Old Jul 04, 2013, 11:23 AM
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Philippines
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See you didn't utilize a Z-cut. How is the hull closed?
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Old Jul 04, 2013, 11:24 AM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
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one more note. i mentioned that in the maiden voyage, i ran the boat for about 45 minutes. recharging the battery, it took in 880mah. the one battery runs both the main motor and the pump motor. 1800mah 2 cell lipo should give me 1.5 hours run time. i have room for a battery as large as 2600mah, which would give me 2.5+ hours of runtime.
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Old Jul 04, 2013, 11:30 AM
Submarines, etc.
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Arvada, Colorado
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Quote:
Originally Posted by redboat219 View Post
See you didn't utilize a Z-cut. How is the hull closed?
the indexing pins molded into the hull give it a lot of strength already, but the front-most index pin has been drilled out on the bottom of the hull, allowing me to use a 1.25" 4/40 bolt to screw the two hulls together. a lip at the rear of the top hull is attached to the front portion, sliding under the rear portion, giving me a solid connection at the rear, with no visible screw or pin. I am investigating the use of several rare-earth magnets in the front, to see if i can't get away with zero screws holding the hull together. as it is, there are no visible screws when it is in the water.

not doing the cut on the front also made it easier to paint.
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Old Jul 08, 2013, 10:43 PM
Submarines, etc.
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Arvada, Colorado
Joined May 2005
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well, technically it is no longer the Moebius Skipjack, it's the Moebius Sculpin. I found photos at navsource.org that showed the Sculpin with what appears to be a haze gray sail.

http://www.navsource.org/archives/08/0859016.jpg

I liked the look, so i sprayed on a final color coat, decals, one coat of dullcoat, and it looks like maybe one more final layer of dullcoat, and i will call her done.

i suppose i should also paint the pedestals gold, and find a piece of wood to mount them on.
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Old Jul 09, 2013, 04:13 AM
Man from Atlantis
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London
Joined Nov 2003
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Quote:
Originally Posted by tchalfant View Post
Can two censored motors be run off of one ESC?
No. That goes for sensorless motors too. One controller per motor. Understanding the basics of how brushless motors work is not hard, do a little reading on how they do work, and you'll soon realise why sharing a controller on two motors is a very bad idea.

These are great articles-

http://www.southernsoaringclub.org.z...-motors-1.html

http://www.southernsoaringclub.org.z...-motors-2.html

http://www.southernsoaringclub.org.z...-motors-3.html

http://www.southernsoaringclub.org.z...-motors-4.html

http://www.southernsoaringclub.org.z...-motors-5.html
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Old Jul 09, 2013, 11:57 AM
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United States, NV, Las Vegas
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Thanks Sub culture! That is a great reference. I understand now why that was a silly question and about back-emf. Something you know about from what generators do, but never put 2+2together.
Thank you again for this reference.
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