My wife died over Christmas and I needed a project to see me through a difficult time. It could, of course be anything but the Beatles song came to mind and so the project turned out to be a yellow submarine, or more accurately an under water, remote operated vehicle or ROV.
Rather than develop a design myself, I decided to make a copy of the Seafox. My version is 14” square and 8” deep. My first problem was to locate suitable materials in UK. All of the tubing and PVC fittings were purchased from Screwfix and the black plastic grill from a ‘cheap’ shop. Stainless steel nuts, bolts etc were purchased on EBAY.
This was enough to allow me to assemble the basic frame as shown below.
I still have to drill a load of holes in this frame for drainage and also four more for the 32 mm pipe clips that hold on the ballast tubes. The black grill was not really rigid enough to mount the vertical thruster on, so I have included a extra 21 mm tube on the centre line to add the missing rigidity. As seen the parts have not been cemented together because I yet have to work out an acceptable method for painting it yellow. At the moment I am thinking I will have to disassemble it, sand all fittings to get a key for the finish, which I will probably do last.
I have a 1100 bilge pump on order from China (a mistake) which is taking forever to arrive, so I have orders two 750 bilge pumps from UK for the lateral thrusters. Originally I thought I might have to fit two vertical thrusters in order to lift any weight with the manipulator, but now intend to try detachable CO2 powered lift bags.
If sediment becomes a problem I have a five bladed 40 mm diameter Graupner prop, otherwise I will use the three bladed 50 mm Graupner props on all thrusters, for extra thrust. I only intend to use the ROV on the med, so sediment should not be a problem.
The control gear.
As I am an ex-electronic engineer I thought I would leave the control gear until last.
I guess the design of the manipulator depends upon what you are going to use the ROV for. Some of the applications I have in mind require far more lift than a small ROV has, so I decided to tackle this in a different way, which means interchangeable manipulator arms for different applications.
1. Detachable CO2 gas powered lift bags for 550 para cord. Since they only have to lift the weight of the para cord they could be quite small. On the business end I need a large detachable carabineer for one application. The lift bag can be hooked at the surface and heavy objects hauled up manually.
2. A detachable neodymium magnet attachment for the lift bags.
3. A wire mesh scoop.
I have actually bought a robot gripper as shown below, but I am not too keen on it …
The water in the Med is always sparkling clear, so for most uses lights will not be required and if they are, the the CCTV camera has LED lights. At the moment I do not have any night time applications.
That is about it for the moment, any progress will be covered in diary form.
27th January 2014
Eventually I want to add a detachable pulse induction metal detector, so I had better provision some means now for attaching the search coil to the front of the ROV. Probably make the search coil housing out of the same type of 21 mm, or 16 mm PVC pipe and the same kind of fittings. I must do some thinking about the effective diameter of the coil. Depth penetration is proportional to the coils diameter but the detection sensitivity for small coins is inversely proportional to the diameter. Pulse induction detectors do have the advantage that the search coils are simple to build and of course they work in salt water. Where to put the non-metallic scoop ?.
One 1100 bilge pump arrived from China.
31st January 2014
I now have all three bilge pumps, a 1100 gallons per hour version for the vertical thruster, and two 750 gallons per hour, for the lateral thrusters. I have cut the white impeller case off all three and removed the plastic impeller, which will be replace by Graupner 50mm three bladed props with prop adaptors. The adaptors will have the effect of raising each prop at least an inch above the motor which will help a cleaner water flow downwards. The same effect will also be seen on the horizontal thrusters.
I have made little progress with making the buoyancy tank at this stage, because of a lack of suitable end blanking caps for 110 mm pipe. I did manage to find a length of white PVC pipe.
4th February 2014.
I gave up trying to find 110 end caps locally and ordered four from EBAY, which arrived today. It was difficult to see from the EBAY image how deep these were and I was aware that some are only 12 mm deep, which would have made water proofing a bit ‘iffy’. However the ones I got are 43.0 mm deep which should make the water pressure proofing a little easier. These end caps simply seal the end of a plain tubes to make the two buoyancy tanks. I will have to do some thinking about how I am going to secure the end saddle clips to the tanks so I do not affect the integrity of the water proofing.
To complete the tanks, I need to now find a source of 21.0 mm saddle clamps as the ones I already have are snap in clips, not saddle clamps.
12th March 2014
I finally got my hands on the original design plans and find I made a boo-boo in estimating the diameter of the buoyancy tanks, which are 3” and not 4”. It appears that 3” is an American pipe size that is not used in UK so maybe I will have to import it. It is a pity, because otherwise the build was going OK.
To be continued ……