Homebuilt ROVs Forum

Hi All,

Yesterday I finished attaching the lower WTC support cradles to the main cross brace/WTC support. I then trimmed a couple of the lower WTC support cradles so that the main cross brace would sit level on my work bench. The upper WTC support cradles did not need to be trimmed.

Today I plan to purchase the marine quality Velcro straps to hold both of the WTCs to the main cross brace/support cradles. I believe that a 36" Velcro strap with a D ring end so that the strap can be cinched up tight around the two WTC tubes should suffice.

I will cut slots in the main cross brace/WTC support to allow the straps to pass through the main cross brace and loop around each tube for a tight fit.

I then plan to start on mounting the four thrusters to the ROV chassis and then move on to connecting the power/control cables to the end cap cable penetrators.

More to come.

Regards,
SSN626B/TCIII

Hi All,

I purchased the two Velcro Marine grade 36" D ring straps this morning and proceeded to cut the necessary slots in the main cross brace/WTC support to allow the straps to wrap around the two WTCs when they are positioned in their top and bottom support cradles.


Front View of both WTCs strapped into position in their Support Cradles


Side View of WTCs strapped to their Support Cradles


Front View of WTCs strapped into their Support Cradles installed in the ROV Chassis


Side View of WTCs strapped to their Support Cradles in the ROV Chassis


Rear View of the WTCs strapped in their Support Cradles in the ROV Chassis

Tomorrow I will begin the installation of the horizontal and vertical T100 Thrusters in the ROV Chassis. I will mount the horizontal Thrusters, one each, on the two 1/2" thick HDPE support plates that be seen in the picture above. The vertical Thrusters will be mounted on the inside of the chassis side plates at the longitudinal center of the chassis and between the main cross brace and the top of the chassis side plates. Two more horizontal Thrusters can be added to the front of the ROV Chassis, without obscuring the upper WTC's camera field of view, some time in the future.

More to come.

Regards,
SSN626B/TCIII

Hi All,

Today I added two additional horizontal Thruster support platforms, similar to the horizontal Thruster support platforms in the rear of the chassis, except these platforms are cantilevered off of a horizontal support made of HDPE that is attached across the front of the chassis. The addition of these two support platforms to the front of the chassis will allow me to have four horizontal Thrusters on the chassis which, in conjunction with the rear horizontal Thruster, will allow lateral motion without having to have a lateral Thruster on the chassis. Also, the additional horizontal support across the front of the chassis will give me a mounting hard point for the future inclusion of a gripper.

I received the 1 m 16 gage single pair power cable and the 1 m 22 gage two pair control cable along with two 6 mm cable penetrators and one blank cable penetrator from Blue Robotics today. I plan to use the two cables to learn how to correctly epoxy the cables securely into the cable penetrator counter bores for a perfect water proof seal before beginning the process of attaching the actual Thruster power and control cables to their respective cable penetrators.

I should have some pictures of the additional Thruster support platforms and the cables and cable penetrators that I will use for the practice epoxy potting process tomorrow.

Regards,
SSN626B/TCIII

Hi All,

Today was reasonably productive for me. I completed two of the rear Thruster mounts and attached the left Thruster to the left Thruster mount. I also shot a picture of the front Thruster support that I added to the chassis earlier this week.

The Thruster mounts consist of a 1/2" thick HDPE rectangle, which is attached to either the side of the chassis (rear Thrusters) or on a horizontal bar across the front of the chassis (front Thrusters), on which a 1/4" thick HDPE rectangle sub mount has been added. The 1/4" thick HDPE rectangle has been drilled with the mounting hole pattern of the Thruster which consists of holes for four screws in a diamond pattern. The use of the 1/4" thick HDPE rectangle sub mount allows me to adjust the thrust angle and position of the Thrusters without having to remove the main 1/2" thick Thruster support from the chassis.

I will complete the right Thruster mount tomorrow and attach the two vertical Thrusters to the interior of the chassis side plates in preparation for determining the length of the Thruster power and control cables from each Thruster to the rear of each WTC.

Pictures below are of my work in progress:


Rear View of Chassis with Left Thruster Installed on Thruster Mount


Front of Chassis with Front horizontal Thruster support blocks attached to the right and left sides of the horizontal Support Bar

The rear horizontal Thrusters are somewhat slightly shrouded by the sides of the chassis, but at least 3/4 of each Thruster 's face is open to the surrounding water.

More to come.

Regards,
SSN626B/TCIII

Hi All,

In a 6 Thruster design the front and rear Thrusters are angled at around 45 deg such that the right and left side pairs can provide lateral movement either right or left.

If I stay with the 4 Thruster design, which I plan to do at this time, I will orient the rear horizontal Thrusters back to the 90 deg ahead position.

Regards,
SSN626B/TCIII

Hi All,

Yesterday I completed the installation of the T100 Thrusters in the ROV chassis in the four Thruster configuration.

Two additional horizontal Thrusters can be added to the front of the chassis for a six Thruster configuration, but will require mounting the four horizontal Thrusters at a 45 degree angle to the horizontal center line of the chassis and will cause some shielding of the Thrusters.

The next step in the ROV chassis construction will be to determine the correct lengths for the Thruster power and control cables so that they can be potted into their respective cable penetrators. Then the cable penetrators will be attached to their respective WTCs end plates.

Following below are a couple of shots of the four Thruster configuration ROV chassis:


Rear View of ROV Chassis with four Thrusters


Top View of ROV Chassis with Thrusters


Front View of ROV Chassis showing Mounting Pads for two additional Horizontal Thrusters

Since I have had only limited experience potting cable into cable penetrators, I purchased 1 meter lengths of power and control cables and two 6 mm bore cable penetrators from Blue Robotics to experiment with. If the potting process was successful I could use the cables to provide power and instrumentation signals from the battery WTC to the navigation controller WTC.

Lucky me, the cable potting process went very smoothly and I now have to very usable power and signal cables though I still have to pot the output side of the cables. To keep the cables from falling over from the vertical center of the cable penetrators while the epoxy cured, I clamped each cable penetrator in a small vice and used my steel do all block to hold the cables vertically upright in the center of each penetrator's bore.

Based on my first try at potting the cables into the penetrators I have the following suggestions in relation to the Blue Robotics Cable Penetrator Assembly Tutorial:

When using CA to anchor the end of the cable into the second counter bore I suggest cleaning the second counter bore with 91 percent alcohol and then applying a coat of CA Kicker to the end of the second counter bore. The addition of the CA Kicker will ensure that the CA quickly hardens in the end of the second counter bore.

Prior to inserting the cable into the second counter bore after the CA Kicker has dried, I recommend using 91 percent alcohol to clean the walls of the upper counter bore so that the epoxy will adhere to the anodized surface of the upper counter bore.

All cable jackets and individual wires that will come in contact with the marine grade epoxy should be cleaned with 91 percent alcohol to ensure a grease free surface that the epoxy can readily adhere to.

I increased the circumference of the end of the 3.5 mm control cables using three layers of 5/32" dia shrink tubing followed by one final layer of 3/16" dia shrink tubing. The addition of the shrink tubing brought the circumference of the cable end up to approximately 5.5 mm which allowed the cable end to stay very stable in the end of the second counter bore while the CA cured.

I recommend clamping the cable penetrator/cable assemblies in a small vice while the epoxy is curing. The vice allows the cables to stay centered vertically in the penetrator upper counter bore otherwise the cables would tend to sag off to one side and not stay vertically centered.

Below are a couple of shots of the cable penetrators/cable assemblies curing in the vice I mentioned above:


Top View of Cable Penetrator/Cable Assemblies clamped in small Vice for stability


Side View of Cable Penetrator/Cable Assemblies clamped in small Vice

More to come.

Regards,
SSN626B/TCIII

Hi All,

While I was preparing the Thruster power and control cables for potting in their respective cable penetrators, I noticed that the inner diameter of the power cable stripped jacket looked very close to the diameter of the outer jacket of the control cable.

Sure enough, I cut a 0.2 inch long piece of the stripped power cable jacket and found that it was a nice push fit over the outer jacket of the control cable. So instead of using shrink tubing to build up the circumference of the control cable to align it in the 6 mm counter bore of the 6 mm cable penetrator, simply use a 0.2 long discarded piece of the power cable outer jacket.

Also, I found it more effective to soak a cotton swab with Kicker in order to coat the bottom of the 6 mm counter bore instead of trying to squirt the Kicker into the counter bore which can be a little messy and wasteful. The cotton swab puts the Kicker right at the end of the counter bore without it going all over the place.

Regards,
SSN626B/TCIII

Hi All,

Today I completed the assembly of the four WTC End Caps. Two of the End Caps have no penetrator holes and will be mounted on the front of the WTCs while two of the End Caps have 10 penetrator holes each for the Thruster ESC power and, control cables, and auxiliary power and instrumentation cables. The End Caps with the penetrator holes also have Enclosure Vent Plugs installed to vent trapped air when the End Caps are inserted in the ends of the WTCs and to equalize the pressure in the WTC with the atmosphere when an End Cap needs to be removed. The Blue Robotics WTC assembly document can be found here.

The End Caps consist of a clear Acrylic Plate (with or without cable penetrator holes) that is attached to an O ring Flange which will be inserted into the ends of the WTCs. The Acrylic Plate is attached to the O ring Flange with six M3 x 16 ss machine screws and compresses an O ring, which is mounted in a groove in the face of the O ring Flange, for a watertight seal.

After assembly of the End Caps I installed an Enclosure Vent Plug in each of the 10 hole End Caps. The Enclosure Vent Plug is much like a Cable Penetrator except that it has a dual O ring screw in sealing plug where the Penetrator cable would normally be inserted.

I then temporarily attached the two cable penetrators, that I had previously potted with a 1 meter 6 mm dia power cable and a 1 meter 3.5 dia control cable, to one of the 10 hole End Caps to get an idea of how the Cable Penetrator spacing would look like.

Shown below are a plain solid Acrylic End Cap, a 10 hole End Cap with the Enclosure Vent Plug attached, and finally a 10 hole End Cap with the Enclosure Vent Plug, and the two Cable Penetrators installed:


Forward End Cap with solid Acrylic Plate


Ten Hole Rear End Cap with Enclosure Vent Plug installed


Ten Hole End Cap with Enclosure Vent Plug and two Cable Penetrators installed

Tomorrow I will remount the WTCs in their respective Support Cradles on the ROV chassis Main Cross Brace/WTC support so that I can determine the correct power and control cable lengths for the ESCs. The ESC power cables will go to the rear End Cap on the lower WTC (battery compartment) while the ESC control cables will go to the rear End Cap on the upper WTC (navigation controller compartment). I will also determine the correct length for the power and instrumentation cables that go from the the battery compartment WTC to the navigation controller compartment WTC.

More to come.

Regards,
SSN626B/TCIII

Hi All,

Today I attached a 10 hole End Cap to the rear of each WTC and then mounted the two WTCs in their Support Cradles in the ROV Chassis.

I then proceeded to determine the best routing of the Thruster power and control cables that would minimize any interference with water flow through the Thrusters.

The first picture below shows the 10 hole End Caps in their respective WTCs mounted in the ROV Chassis:


WTCs with10 hole End Caps

The next picture shows a mockup of a Thruster power and control cable mounting scheme:


Mockup of WTC End Caps with Thruster Power and Control Cables

The final picture in this group shows the Thruster cable routing from the top of the ROV Chassis:


Top View of Thruster Cable routing

I am trying to keep the Thruster power and control cable routing from becoming a rats nest in the rear of the ROV Chassis. Where there is wire holding up the cables, I will use cable clamps to route and retain the cables in the positions shown in the pictures. I will also add additional cable ties to help confine and route the cables away from the Thruster water flow.

Since this is my first cut at routing the Thruster cables, I am open to suggestions if anyone can spot any obvious flaws in my cable routing scheme. I plan to have long cable pigtails inside the WTCs to allow the battery and navigational trays to be removed from the front ends of the WTCs.

More to come.

Regards,
SSN626B/TCIII

Hi All,

I spent most of today completing the routing of the Thruster power and control cables.

It turned out that I needed 3/8" dia cable clamps, which I was fresh out of, to position the power and control cables to the ROV chassis so I was off to my local Home Depot. While I was there I also purchased #6 x 1/2" ss button head sheet metal screws to attach the cable clamps to the chassis.

Once I had routed and clamped the cables into position to my satisfaction, I adjusted each cable for a little slack and marked it with my trusty Sharpie marker where it entered its respective hole in the 10 hole End Cap. I then pulled each cable out and made sure that the marked length of both the right and left horizontal Thruster power and control cables were close to the same as the wiring route for each horizontal Thruster is the same. I then did the same for the and right and left vertical Thruster power and control cables. Once I was satisfied that the power and control cable marked lengths were virtually the same, I began planning how I would remove each Thruster and pot each Thruster's power and control cables in its respective cable penetrator.

More to come.

Regards,
SSN626B/TCIII