Robbe Seawolf V2

Im starting a thread there just now as i have a lot of ideas and i dont want to start new threads for all of them.

this is the only photo I have of what I bought, it should be here soon


for controlling it all I'm probably going to use a modified version of my ESP32 boat controller with sub functions added on.


I have been mainly trying to work out depth control systems, most of which I have posted before.

the first one will be a pressure sensor, i found this automotive one that had a thread so i should be able to just port it to the outside to get readings.

https://www.aliexpress.com/item/32986724606.html

The second depth system will be a sonar or 2, the first will be a dual transducer version for depth, and im probably going to install another single one in the nose to stop me crashing into anything. I want to eventually put fpv on it and visibility is almost nonextent at the best of times so having something to give me warning of a collision is probably a good idea.. The single transducer has a minimum range of 1.5m so its not ideal for measuring shallow water but the dual transducer will go down to 15cm.

https://www.theassociationofmodelsubmariners.com/t1980-jsn-sr04t-depth-sounder
https://www.aliexpress.com/item/1005001594028046.html
https://www.aliexpress.com/item/1005003199461771.html



Third will be a conductivity probe disguised as a conning tower, this gives an analogue output based on how deep it is and how salty the water is, but it should allow it to just skim the surface to keep the video antenna above the water.

https://www.aliexpress.com/item/1005002748929090.html

And finally il be using the radio RSSI as a depth controller so that rather than it coming up once it fail-safes it should start coming back up before that happens and in theory it should run right at the edge of its range without hitting failsafe.

For leveling and heading hold I will be using a SparkFun 9DoF IMU ICM-20948 board, these are a vast improvement over the older MPU6050 and 9250 boards as it has its own onboard data processor that handles all the calculations and it will just spit out the values you need rather than raw data making integration a lot simpler since you dont need to worry about loop times or interupts messing with its calculations, you just retrieve the latest data from it.

https://learn.sparkfun.com/tutorials/sparkfun-9dof-imu-icm-20948-breakout-hookup-guide/all


for the diving system I have been looking at blood pressure collars , they look much more durable than the drip bags or balloons I have seen people use

https://www.aliexpress.com/item/1005002130699623.html

Based on recommendations I will probably go for a high capacity peristaltic pump and overvolt it to get higher performance, I will be running it from an esc so if i run it at low power for regular operation and just keep max power for emergences it should be ok.

https://www.aliexpress.com/item/32817707131.html

for propulsion im going to convert it to brushless, that video of the seawolf up out the water was too interesting for me not to try it, I belive its running something like a 500kv 3548 outrunner.

https://www.youtube.com/watch?v=GKUx1pkcV8I
Ihave ordered this 750kv motor and 60 ESC

https://www.aliexpress.com/item/1005001394664677.html
https://www.aliexpress.com/item/32769780620.html


for auxiliary propulsion im going to install a bow thruster and possibly a stern thruster if I have space and buoyancy for them, I have seen a photo of them installed in a sub and it was reported back to me that it worked really well.

https://www.theassociationofmodelsubmariners.com/t1979-water-jet-manouvering-thusters



As for a radio system , I have a 1w openlrs 458 system, frsky 868 1w sitting around, Im not sure what one il use for now.

For the video system, its not going to be deep diving, il have to keep a relatively long antenna on it above the surface as 5.8ghz will go nowhere underwater, so its just going to be used for running at periscope depth.

has anyone any other thoughts or ideas or anything im missing.? let me know" />

Good news! the sub arrived today and its in much better condition that i was expecting, I buy a lot of wreckage from ebay so I wasnt expecting much. its already had the bow planes connected to a servo and it looks really clean with no damage as far as i can see

geofrancis wrote:Im starting a thread there just now as i have a lot of ideas and i dont want to start new threads for all of them.




As for a radio system , I have a 1w openlrs 458 system, frsky 868 1w sitting around, Im not sure what one il use for now.

For the video system, its not going to be deep diving, il have to keep a relatively long antenna on it above the surface as 5.8ghz will go nowhere underwater, so its just going to be used for running at periscope depth.

has anyone any other thoughts or ideas or anything im missing.? let me know

given the choice of the two rf modules, i would go with the openlrs 458mhz system. considerably longer range than any of the 915/868mhz systems.


I have used the "automotive pressure sensor" myself, but be warned, there are two types of sensors, "absolute" and "differential". an absolute version is sealed, so the reading is based on the pressure from the external port versus a known vacuum, built into the unit from the factory. the differential type have two ports, one "external", one "internal". these type work by comparing the pressure differential between the two ports. it will never show a true depth based on the water pressure outside the WTC if the pressure inside the WTC is also increasing (due to a piston style or bag style ballast tank that also increases the pressure inside the WTC). if your ballast tank is completely separate from the WTC, like an OTW style ballast tank, then a differential style sensor will work.

i was able to convert a differential style sensor like you show to an absolute by sealing its internal port with epoxy, basically making its comparison value whatever the air pressure was when i glued the port shut.

lastly, i prefer the simple analog versions over the more complicated digital style because you use them with a simple analogRead() of a pin in your arduino sketch.

tsenecal wrote:

I have used the "automotive pressure sensor" myself, but be warned, there are two types of sensors, "absolute" and "differential".  an absolute version is sealed, so the reading is based on the pressure from the external port versus a known vacuum, built into the unit from the factory.  the differential type have two ports, one "external", one "internal".  these type work by comparing the pressure differential between the two ports.  it will never show a true depth based on the water pressure outside the WTC if the pressure inside the WTC is also increasing (due to a piston style or bag style ballast tank that also increases the pressure inside the WTC).  if your ballast tank is completely separate from the WTC,  like an OTW style ballast tank, then a differential style sensor will work.

i was able to convert a differential style sensor like you show to an absolute by sealing its internal port with epoxy, basically making its comparison value whatever the air pressure was when i glued the port shut.

lastly, i prefer the simple analog versions over the more complicated digital style because you use them with a simple analogRead() of a pin in your arduino sketch.

I thought this was an absolute pressor sensor as I couldnt see any vents, where are they located?

geofrancis wrote:

I thought this was an absolute pressor sensor as I couldnt see any vents, where are they located?

it is hidden somewhere in the seam between the plastic and metal portions. i wrapped the metal in painters tape to make a wall, and then filled it with 1 hour epoxy,

I have designed a new 433mhz rc system for testing, its basically a Ebyte E32 433 module connected to a Flysky Ibus serial recevier. The reason it works is the flysky protocol is one of the few that runs at a normal serial speed at uninverted levels. meaning you can just send it over any transparent serial radio thats fast enough and it should just work.

preliminary testing is showing a latency just under a second but that could still be improved, as i haven't tweaked the settings much yet.

The Ibus telemetry also runs at the same 115200 serial in the opposite direction so in theory it should have both RC and telemetry but I havent tested that yet.



In theory a system like this could be used with a relay setup where this would be either mounted on a pole next to the pond or on a boat or even aircraft in the centre of the pond or even folowing the sub, giving almost unlimited range.

Has anyone thought about making a working FPV periscope for a sub? I have been making some waterproof cameras for another project when I realized that they could be used to make an FPV periscope system. Rather than needing a tube filled with mirrors and optics, just use a small waterproof camera mounted on the end of the antenna that way the only thing above the surface will be the camera and video antenna.

to seal the cameras I have just been coating them in either epoxy or liquid insulation.








https://www.aliexpress.com/item/1005002910406092.html
https://www.aliexpress.com/item/1005003585503542.html

I have been concerned about overheating the motor in a sealed sub so I have ordered a watercooled motor mount for the 3536 outrunner motor.
https://www.aliexpress.com/item/1005005179341152.html

im waiting for parts to arrive before I can do anything else. motor, bladder and bow thruster pump have arrived but im still waiting for the ESC, pump and motor mount.

I have been busy paying the Bill's that I haven't had much time to do the sub other than print a stand for it.
Waterproof servos, bladder, pump, brushless motor, water pump for bow thruster have all arrived, I plan on making some progress on it soon, i want it in the water before the end of the summer.

I had some time last night so I decided to do some basic testing with what I have before I started modifying it, and from what I have found I dont think this sub has ever been out in the water. the seal for the WTC is obstructed by some of the outer shell so it doesnt seal properly when i had it in the bath for around 5 minutes there was atleast 50ml of water came out when I cracked it open again. so the plan is to try and file back some of the plastic that obstructing the gasket and see if I can get it watertight. I'm going to run it as is for now other than a receiver change and ballast as there is an open day I would like to take it to and I wont get the modifications done in time.

I also totally underestimated how buoyant the sub is, with just a small 3s lipo in it the sub was bobbing on the surface like a cork and rolling over so im going to have to get some lead for ballast just to keep it upright.

After some more testing, I trimmed the shell to give it clearance and tested it in the water again but with just theWTC and a lot of water got In. The seal looked ok, certainly not as bad as the amount of water would suggest. Then eventually I saw a bubble appear when I was holding it down.

The previous owner has drilled into the internal water tight compartment for the screws rather than the flange around the outside so there are 6 holes in the sub from screw holes used for holding the shell on.

Found some more problems, basically the rear bulkhead has not been attached straight, its very slightly tilted. This is causing the interface between the 2 halfs not to line up properly allowing water to get between them. Plan A is i have ordered some thicker gaskets to try and take up the space hopefully its enough because plan B is I will need to break the sub, straighten it then glue it back together again.

would it not be possible to trim the mating surface of the cylinder to match the angle of the endcap?

I figured out that I could realign the rear bulkhead by breaking the lower support free from the bulkhead and moving it to there was around a 2mm gap between them and re gluing it. 

I just done it. And have done some testing in the water and its vastly improved, I think worth a new gasket and some grease it should be good to use.

I have ordered a Schrader valve with a 1/8 thread on it, my plan is to mount it to the front bulkhead and add a little pressure to the WTC so i can find the bubbles. I assume it's the gasket leaking but it's hard to be sure, there could be some more hidden holes for all I know.

so I managed to add some pressure to the WTC, and bubbles start....from the end of the prop shaft, I'm starting to suspect there is no grease at all in the propshaft as it does sound a little squeaky. due to the geared drive unit you cannot see the inner end of the propshaft and there is no easy way to get to it. from reading the manual there should have been a grease nipple installed to the propeller shaft for greasing.

I have managed to find a clamp on oiler for the propshaft. I would have preferred a metal one or to drill and tap one in but im not thrilled about doing that if i cant take the shaft out. with this I can just drill a small hole, il probably put some jbweld marine around it to be sure.


https://www.cornwallmodelboats.co.uk/acatalog/Caldecraft-Propshaft-Oiler-for-6mm-Propshaft--C4302.html#SID=438

I have fitted the oiler with some waterproof high strength adhesive around it and drilled a small hole for the grease to go in.  I also added the schrader valve on the rear bulkhead so I can pressurise the WTC to find leaks.




done some pressure testing and its not as bad as I expected. i put 3psi into the WTC and looked for bubbles,

The larger bubbles were coming from the propshaft grease port and the hole in the front bulkhead where the threaded rod goes through to secure the front of the sub on.  I blocked the grease port and the bubbles started coming out from the end of the prop shaft.

Interestingly there were a lot of bubbles coming out from around the gasket but they were very small and from all around it so i suspect that is just a lack of grease and the rubber being too hard. I have a soft silicone gasket ordered but its not arrived yet.

so the fixes im looking at are basically just grease for the shaft and around the main seal interface, change the gasket to silicone and I need some way of ensuring the threaded rod at the front is sealed, I think all it needs is a soft washer behind the nut.

Sorry to add a cupful of cold water (as opposed to throwing a bucket!) but I really would look to O rings or, better still, oil seals for prop shaft seals. The technology is really well developed for these and quite cheap. Grease and oil filled prop shafts are OK for surface ship models but always tend to leak under pressure.

Interestingly I was recently looking at renovating a Graupner Shark (must be a 30 year old model, I think) and this has twin oil filled prop shafts and a flat hatch (another pet hate!). The model has currently gone back on the shelf!

David

david f wrote:Sorry to add a cupful of cold water (as opposed to throwing a bucket!) but I really would look to O rings or, better still, oil seals for prop shaft seals. The technology is really well developed for these and quite cheap. Grease and oil filled prop shafts are OK for surface ship models but always tend to leak under pressure.

Interestingly I was recently looking at renovating a Graupner Shark (must be a 30 year old model, I think) and this has twin oil filled prop shafts and a flat hatch (another pet hate!). The model has currently gone back on the shelf!

David

do you have any links for what I should be looking at? the reason I was looking at silicon grease was I could apply it without taking the shaft out but im open to better options.  

To get access to the inner end of the shaft would require disassembling the rear of the sub to get the motor out and gearbox apart to get access. so any solution can only require access to the outer end of the shaft.


would some rubber washers on the end of the propshaft be enough?

geofrancis wrote:
...

do you have any links for what I should be looking at? the reason I was looking at silicon grease was I could apply it without taking the shaft out but im open to better options.  

...

something like this, for what ever diameter your propshaft is

https://engel-modellbau.eu/shop/en/Sub-Components/Spare-Parts/Shaft-Sealing-Ring-4-11-6-for-shaft-4mm.html

Thank you, I have ordered a few.