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Alfa V2

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Alfa V2

Postby petn7 » Tue May 13, 2008 5:21 pm

I rebuilt my 1/200 Alfa Submarine after its WTC had a leak. I built a new WTC with Skip's custom made endcaps and some Lexan tubing from McMaster. Here are some links to the older version of my Alfa

http://s181686668.onlinehome.us/phpBB2/ ... highlight=

http://www.rcgroups.com/forums/showthread.php?t=256185

Here are some pictures of the rebuilt Alfa. It's a dynamic diver and you'll notice some anhedral fins that I hope will reduce the roll while turning.



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Postby Rogue Sub » Tue May 13, 2008 6:39 pm

Looks like fun. How does she handle?
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Postby petn7 » Tue May 13, 2008 6:58 pm

I haven't run Alfa V2, but the older version handled, OK. She rolled into the turns like mad (but turned very tightly). Also, she wasn't easy to keep level, although making her ride lower in the water made her much easier to keep level (hence she sits unrealistically low in the water). Another reason the Alfa V2 sits low in the water is to make it easier to dive when surfaced.

I meant to add a pitch leveler in the new WTC, but cut the WTC tube a tad too short. I think I could make some space, but that would mean more WTC buoyancy and therefore higher tendency to roll in the turns since I'd have to use less foam.
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Postby Rogue Sub » Tue May 13, 2008 8:08 pm

you could try loading more weight in the bottom and then countering it with foam in the top to increase stability.
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Postby petn7 » Tue May 13, 2008 8:40 pm

Nuke Power wrote:you could try loading more weight in the bottom and then countering it with foam in the top to increase stability.


I know, but then the sub gets sluggish (slower acceleration and deceleration) because of the extra weight.
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Postby Rogue Sub » Tue May 13, 2008 9:31 pm

How fast you trying to make it?
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Postby petn7 » Tue May 13, 2008 9:48 pm

Nuke Power wrote:How fast you trying to make it?


I dunno, but faster, the better. The motor is a modified SWM S300-sized motor for extra torque in return for fewer RPMs. I'm using a 6 cell 400mah NiMH battery pack. Needless to say, I would love to run 8 cells, but I highly doubt I have room for 8 cells and my APC-4.

The last run w/o a leak went very well since I made my Alfa sit much lower in the water. As long as I don't have to fight the sub to keep it submerged, she runs level enough for me. Maybe I'll enlarge the WTC in the future and add the APC-4.
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Postby redboat219 » Wed May 14, 2008 12:52 am

What seals are you using there? Doesn't look like the regular Subtech seal. Also, is that a couple you got there connecting the motor with the prop shaft?
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Postby petn7 » Wed May 14, 2008 1:19 am

redboat219 wrote:What seals are you using there? Doesn't look like the regular Subtech seal.

I'm using 1/16" pushrod seals that Caswell sells.


redboat219 wrote:Also, is that a couple you got there connecting the motor with the prop shaft?

That's silicone fuel tubing
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Postby redboat219 » Wed May 14, 2008 1:54 am

Ooops. I meant the one inside the WTC.

How big is your WTC?
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Postby petn7 » Wed May 14, 2008 11:33 am

redboat219 wrote:Ooops. I meant the one inside the WTC.

How big is your WTC?


The WTC is about 185mm long and about 37mm wide

The coupler inside the WTC is fuel tubing as well. The propeller shafts are 1/8" all around, but the motor shaft is much smaller. I had to use some skinny fuel tubing over the motor shaft, then regular tubing over that. It's a pretty effective adapter.

EDIT: Fixed my decimal mistake.
Last edited by petn7 on Fri May 16, 2008 12:48 am, edited 1 time in total.
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Postby redboat219 » Thu May 15, 2008 10:48 am

Anymore space to put in a micro airpump? Then you can make her a static diver instead. Just get the smallest blood pressure cuff and stick it on the outside of your WTC and presto.
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Postby petn7 » Thu May 15, 2008 6:22 pm

The smallest airpump I know of won't hold a seal. I could probably make this a static diver by using a forward only ESC, lithium battery pack, and a few other "shrinking" measures, to make room for the airpump and tubing, but maybe I'll do that later.

For now, I want more room for a bigger battery and a pitch leveler.
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Postby Warpatroller » Fri May 16, 2008 12:26 am

Petn7,

What is the diameter of the drive motor in your WTC?

Also, your stated WTC dimensions seem to not be possible. You said, "The WTC is about 18.5mm long and about 37mm wide" The length dimension would appear to be impossible based on the width, which would make your WTC less than an inch long..

What is holding your drive motor in place inside the WTC?

Steve
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Postby petn7 » Fri May 16, 2008 12:46 am

Warpatroller wrote:Petn7,

What is the diameter of the drive motor in your WTC?

Also, your stated WTC dimensions seem to not be possible. You said, "The WTC is about 18.5mm long and about 37mm wide" The length dimension would appear to be impossible based on the width, which would make your WTC less than an inch long..

What is holding your drive motor in place inside the WTC?

Steve


Hahahaha, oops. The diameter is 37mm wide and 185mm long. I'm not great with decimals, and that's the metric system's greatest drawback...yet greatest advantage, but anyhoo...

The motor's diameter is...I don't know. This is the motor I'm using:

http://www.geocities.com/smallworldmode ... otors.html

It's the SWMM-1 (300-sized motor). I assume it has the same dimensions of a S300 motor. I have yet to run the sub at 100% throttle, so I can't say if using this specialized motor is ideal or not. It's replacing a Mabuchi motor like the one:

Image

I assume it will be an improvement, if not in performance, at least in efficiency.

The drive motor is being held by friction. I glued plastic tabs to the motor directly. I slid the motor into the "rails" glued to the inside of the WTC. I then glued a few pieces of plastic in the "rails" so the motor can't slide back and hit the servo/electronics tray (probably wasn't necessary, but just in case). The motor can't slide forward since the fuel tubing adapter would hit the 1/8" oilite bushing and shaft seal. Here's a close up:



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