The Robbe Type XXI Refitting With A New Casing

[AQUASUB]

Its a beautifully day on this Sunday AM and she is going on another mission .
With the Lipos I have been getting phenomenal run times so much that I have to change out the TX battery every 2 and half hours !
I run her on a large public park lake where one can go completely around ,its the place I have ever run as there are many man made harbors and ,docks and drainage pipes that the sub can completely park into just like a German sub pen and it makes it super easy to launch the sub as one needs not to get wet ,just hoist her in to the water and out.I wish you guys could come run at this great lake!
So far I have run this sub since the refit 12 times with no malfunctions just allot of fun the way it should be.

Dave

[AQUASUB]

She Gets Hot!

Its been a while since I have posted as I have running a lot of missions, but this one is, to say the least, very interesting.

Previously, I could only guess at just what temperature the drive motors on my Robbe Type XXI, (a 73 inch monster) were running at after a long run. walking some 2800 yards around a big lake.

Usually I make the mission for 3 trips around the lake with a 2 to 3 rest stops and to practice docking and sub pen maneuvers in the underground pens (culverts). They make perfect pens for a couple of 2 subs as long as the water level is adequate.

Well as one can imagine, that's a lot of distance and running time, but with Lipos its so easy to go the distance. But one has to watch out for the enemy of electric motors - heat. You won't believe how hot they get, not accounting for the air space which also gets heated up and expands inside of the casing. A seal or plastic wall could burst causing a catastrophic failure of the casing and consequent flooding. One day I will make a pressure reading of it at peak temperature.

After running the sub on the surface for some 1000 paces the reading on the Telemetry screen read 123 F on the port motor and 128 F on the starboard motor. No water cooling at all except for the motor coming into contact with the casing which is plastic, not the best conductor of heat but some dissipation does occur.

I did same run again but submerged this time. It gets even hotter as the motors must work harder to go at the same speed because more surface area of the sub is in direct contact with the oncoming water stream.

The temp reached 145 F on the starboard and 142 F on the port .
The air temp was a 85 F and the water in the 70's.
Imagine how much hotter it will get in the peak of summer!

So now we know just how hot it gets inside of a normally set up sub of this size.
The motors are 2 Mabuchi 550 can motors on 11.1 Lipos and 2 3.5 to 1 ball bearing geared boxes and 2 Viper 20 amp ESCs turning the stock 3 bladed props with very little friction on the hole drive, so its set up very well .

That is why I water cool all my subs and have done so for many years now no regrets just good long runs.

Now comes the fun part of installing water cooling to this sub as it was not done for this test. It will be a challenge in that the casing is 3 inches in diameter and those 2 motors are side by side. With the offset of the gearboxes it gets too tight with the cooling coils ,so I have to figure out a different approach, maybe a epoxy that conducts heat ,placed around the motor and then a screw or brass shaft exiting the casing at the rear into the water just might do it.


Anyway I have to figure out something that will extract that heat and keep them cool, as already there is a faint smell of hot windings - and that I do not like.


If one goes for any decent distance and run times on their sub, to me it would be a good idea to keep them cool.

I know I brought this up before but now I have some hard evidence and thought I would share it.FYI.

Dave Amur Sub Yard

[AQUASUB]

Another item I would like to mention is the new gear pump I use works very well,it uses about .66 of an amp at 12 volts the reason ,a geared down small 12 v motor and yet it pumps a good quantity of water at a steady rate of flow that makes for very scale like dives and surfacing .I can do my long runs and still have plenty of power to dive several times without having to be concerned about the power level.With the original pump it used allot more power so I will only use that one for hydraulics.
Also with this ballast system the casing is automatically pumped dry each time the sub surfaces ,I nice feature to have encase there is a leak and is done by simply placing the end of the internal air pickup tube at the very lower aft corner of the casing as the sub moves forward or with a stern down the water is collected and pumped out automatically to the ballast tank.

My next sub the Engel Gato a beuty at 6.5 ft,same basic internals but water cooled most definatly and full Telemitry!
Time to go again ,in the am is the best cool and Serene.