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May 21, 2014, 06:29 AM
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Question

Revell 1/72 Gato class sub


I have finally been able locate and purchase a Gato sub.Just a bit of advice on construction of the WTC.My previous project was a Revell 1/72 Type vii which was setup as a dynamic diver using brushed motors.
My questions are (1)Has anybody used brushless motors in their WTC?
(2) What type ballast system has been successful .I was thinking of using a bladder system with a reservoir tank and air pump.
I am planning on manufacturing my own WTC as I did in my previous project.At my age it keeps the brain cells active .
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May 21, 2014, 10:56 AM
Doing things differently
Brushless motors are fine, though you may need a gear box or something to slow the propeller down.

Then again they might be making slow brushless motors now.

But they do work and they are better than brushed so sorry for the half assed answer I havent bought a brushless motor for a boat in awhile.

Michael

P.S im using a brushless motor and gear box to slow it down and power two shafts in my 1.7m U-Boat.
May 21, 2014, 04:20 PM
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Quote:
Originally Posted by Subsonic Mike
Brushless motors are fine, though you may need a gear box or something to slow the propeller down.

Then again they might be making slow brushless motors now.

But they do work and they are better than brushed so sorry for the half assed answer I havent bought a brushless motor for a boat in awhile.

Michael

P.S im using a brushless motor and gear box to slow it down and power two shafts in my 1.7m U-Boat.
Thanks for the reply Michael.One of the problems with my Type vii is the heat developed by the brushed motors and thought of trying a inrunner brushless motor with a low KV rating that might possibly fix this problem.
With all the extra room in the Gato compared to the Type vii converting this to a static diver shouldn't be a problem.Initially I am experimenting with a bladder system with a air pump and a storage tank as an emergency blow. I have a B & D Enterprises pneumatic landing gear system that I thought of adapting as it comes with the storage tank and a servo operated pneumatic switch.The pump I was thinking of using was one out of a portable blood pressure monitor.Any thoughts.
May 21, 2014, 04:32 PM
Doing things differently
I have been running this sub for 3 year brushless power. Shes about 40cm long.
40 minutes run time brushless.
3x 5-7 runs with a brushed motor. It got very hot in there!

Tiny motor two, I used to use a speed 400 and the brushless motor is half the length and a slightly smaller diameter.

If you can find a small low Kv inrunner that will probably work well, subs dont need lots of power.
May 22, 2014, 01:25 AM
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Thanks Michael .Yeah I think I will be heading down that road.What type of ballast system are you using?Any thoughts on what I proposed in my previous post.
May 22, 2014, 04:47 AM
Doing things differently
Well I'm not exactly a ballast tank expert. Might want to ask someone else for that..

All I can say is that submarine above is dynamic diving (no ballast tank) and my 1.7 uboat is going to use a piston ballast tank.

Michael
May 22, 2014, 05:57 AM
Man from Atlantis
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Ballast tank considerations aside, I would add that if the brushed motors are generating a lot of heat, it suggests you have them badly matched to your props/drive, because a Type VII shouldn't be very demanding on the power front.

Brushless motors are more efficient especially at higher power levels, so they're ideal for fast scale and sport boats, but when it comes to lower power levels needed for most scale craft the benefits are smaller especially if you use good quality brushed motors (e.g. Buhler Maxon, Pittman, portescap etc.).

Brushless motors do tend to be much smaller than their brushed counterparts, but it's difficult to find lower revving units. Those that are available tend to be pricey. You can of course use reduction either by gears or belts, the latter is virtually silent and although theoretically v-belts are less efficient than gears, they are inexpensive and easily configured to your needs- if you have a lathe you can turn your own pulleys.

One other point to note, most brushless motors are for use with sensorless controllers, and the start up characteristics of these units are rather more aggressive than sensored designs. No brushless system I have used has the low speed running characteristics of a good quality, multi pole brushed system, so if you like to creep around the lake at very low speed, a brushed system still has the edge IMO.
May 22, 2014, 05:48 PM
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Quote:
Originally Posted by Sub culture
Ballast tank considerations aside, I would add that if the brushed motors are generating a lot of heat, it suggests you have them badly matched to your props/drive, because a Type VII shouldn't be very demanding on the power front.

Brushless motors are more efficient especially at higher power levels, so they're ideal for fast scale and sport boats, but when it comes to lower power levels needed for most scale craft the benefits are smaller especially if you use good quality brushed motors (e.g. Buhler Maxon, Pittman, portescap etc.).

Brushless motors do tend to be much smaller than their brushed counterparts, but it's difficult to find lower revving units. Those that are available tend to be pricey. You can of course use reduction either by gears or belts, the latter is virtually silent and although theoretically v-belts are less efficient than gears, they are inexpensive and easily configured to your needs- if you have a lathe you can turn your own pulleys.

One other point to note, most brushless motors are for use with sensorless controllers, and the start up characteristics of these units are rather more aggressive than sensored designs. No brushless system I have used has the low speed running characteristics of a good quality, multi pole brushed system, so if you like to creep around the lake at very low speed, a brushed system still has the edge IMO.

Thanks for the info Subculture.Food for thought.My Type vii is a dynamic diver so with the small dive planes it requires a bit of speed to submerge .The motors I chose were the biggest that would fit into the WTC and at 50 mm diameter is a little cramped.Any motor due to the inefficiency of their windings will create heat.The problem I did have which created most of the problem were the seals that added more load on the motors.I think that problem has been cured and the last run was successful without any leaks.There is heat generated from the motors not as much as on previous runs.
I am retired and not too flush with money so as with the Typevii the Gato WTC will be a self design and build.At least with it the WTC will be a larger diameter with more room for motor selection.Could somebody recommend suitable size motors for this sub.
May 23, 2014, 05:44 AM
Man from Atlantis
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Sounds like a Robbe U47 or a Type VII of equal proportions.

A boat that size will need a fair amount of power to remain submerged under dynamic force with a fairly high freeboard. Even if you went brushless you would find the motors generate heat.

Motors for the Gato are somewhat subjective as it depends on props used and speed you want. I would look at 400 size motors for brushed, and CD-ROM size motors if you want brushless. Also this boat has been converted many times so plenty of experienced people out there who can recommend a good set-up.
May 28, 2014, 05:23 PM
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Thread OP

WTC material


Sorry another question about the type of material used for the WTC.In the Type vii I used polycarbonite (lexan) tubing but was wondering if acrylic tubing could be used as a substitute?The polycarbonite tubing in the length needed would be very expensive.I can purchase 60mm X2mm thick acrylic for a quarter of the price and was wondering if that would be suitable?
May 28, 2014, 05:30 PM
Doing things differently
Acrylic will work fine, as long as you dont cut it or drill it. Its very brittle and cracks easily.
Unless you have experience with working with it then your the boss.

There are many places where they cut it to length for free when you by some tube.

Michael

P.S. Dont be afraid to ask more questions!
May 28, 2014, 11:12 PM
Man from Atlantis
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PVC pipe has similar qualities to polycarbonate e.g. easy to cut and very tough. However it's about the cheapest material in cylindrical form. The chief disadvantage is that it's usually filled, which makes it opaque, and secondly it's not always available in the wide range of sizes that polycarbonate and acrylic pipe is. Personally I feel transparent cylinders are a bit overrated, after all you can't see leaks in a cylinder with the top on, and besides which clear cylinders go a silvery opaque once submerged anyway.
May 29, 2014, 06:32 AM
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Thread OP
Quote:
Originally Posted by Sub culture
PVC pipe has similar qualities to polycarbonate e.g. easy to cut and very tough. However it's about the cheapest material in cylindrical form. The chief disadvantage is that it's usually filled, which makes it opaque, and secondly it's not always available in the wide range of sizes that polycarbonate and acrylic pipe is. Personally I feel transparent cylinders are a bit overrated, after all you can't see leaks in a cylinder with the top on, and besides which clear cylinders go a silvery opaque once submerged anyway.
I was thinking of using 65 mm PVC drainage pipe and cutting a large window in the top of the WTC to inspect for leaks.I think that will full fill my requirements.
May 29, 2014, 09:20 AM
Registered User
Suggestion for PVC users.

Might try using clear end caps.
Then no need to cut in to the cylinder to place a window and weaken it's integrity.

Or make very small float switches that will light up small LEDs on end cap, running lights or on masts so you can see them while running and avoid disaster by coming t shore.
May 29, 2014, 09:34 AM
Man from Atlantis
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If you build a decent cylinder it's very unlikely you'll experience leaks anyway.

The modellers I see having problems with leaks are invariably the ones with box style pressure hulls, or they've bodged the job.


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