Design frame for first prototype

[MFauzanAP]

This will be a 3D-printed frame with a focus on flexibility of thruster placement. It should be built to fit the electronics hull from the borrowed ROV. The hull should focus on modularity so we can add cameras, sensors, etc. later on for the other subteams/subsystems to experiment with. Sub tasks to be completed:

• [ ] Measure electronics hull dimensions
• [x] Identify CAD model to be used for reference
• [x] Meet to discuss potential ideas
• [x] Create modularity system
• [ ] Create CAD models for prototype hull
• [ ] Manufacture the frame by 3D printing

[MFauzanAP]

Added initial version of the heave plate (plates at the top and bottom), dimensions are all parameterized and can be changed easily from one variable. Next steps are:

• [ ] Change dimensions to match bolts and latch and add tolerances for error
• [ ] Assign a material and 3D print it
• [ ] Design and print placeholder adapter to test how well the modularity functions

[MFauzanAP]

@NazarulYousef what if instead of buying an L-bracket ourselves, we 3d print one? We can design it to be snap-fit so no need for nuts and bolts, just slide it into the hole, see below.

[MFauzanAP]

Since we have some T200 thrusters currently with us in QU, we will need to quickly 3D print a sample frame to check if we need a mounting kit for the thrusters or not.

[MFauzanAP]

Designed some brackets and plates for testing the snap fit design, this will be used as a sort of angle-bracket to connect perpendicular plates. Both have been optimized for 3D printing but are untested so far.

Note that there have been some gaps added to account for 3D printing allowances for a clearance or transition fit. The last image also shows a removable variant for semi-permanent fitting.

[MFauzanAP]

I think we will need to rethink the design of the frame, we overlooked the fact that for the below configuration, the frame is very enclosed and there will be little water for the thruster to propel with.

I'm thinking of redesigning it by using aluminum (or 3D printed with steel rods for strength) T slot extrusions like the below concepts. However, it might be a bit more difficult to manufacture, and we will need to build/print dedicated brackets for each component.

[MFauzanAP]

Purchased a V Slot profile from voltaat, although it's not the one we need and we only have one, it's still useful to check tolerances and fit, turns out for a 20x20 profile, we want around 20.5 mm for a sliding fit, 21 is a bit too loose and rattles too much, 20 is transition fit.

I'll be testing the T slot nuts now and checking which size/clearance we need.

[MFauzanAP]

3D printed another test bracket, this time inner hole size is 20.5 mm which creates a perfect clearance fit. Even with only 1 T-nut attached, the whole thing is very sturdy. I think I will be using these dimensions going forward.

[MFauzanAP]

First major milestone completed for this task (still missing some nuts and bolts but will be done soon).

Created the wings for the frame where you can add whatever modules you want on the black rails. It has an aluminum skeleton with a V-slot profile that makes it very sturdy and hefty. However, it's probably a bit too dense and will sink when put in water, hence we need to either use buoyancy foam or add some low-density modules on there.

Approximate Dimensions: 584x720x200 mm

• The main cylindrical hull will be placed in the middle, drawn in red.
• The black rails are aluminum 6063.
• The white brackets are 3D printed using 100% infill PETG.
• A steel rod will also be embedded inside this bracket for better strength, highlighted in green.
• Carrying handles can also be easily installed on the rails using drop-in T-nuts.
• The angled side allows us to have vectored thrusters, and 3D vectored when using the correct bracket.

 

[MFauzanAP]

Another update on the frame design:

• Added T200 thrusters and colored them maroon to match qatari flag. Currently they are in a 4x 2D vectored + 4x vertical configuration, which seems to be the most common configuration in the RoboSub competition
• Changed dimensions to be bigger, now it is 684x788x200 mm (previously 584x720x200). This was done to make space for the thrusters, batteries, torpedoes, and other modules
• Designed mounting brackets for the thrusters (untested, will check once I get the thrusters), these are supposed to have adjustable angle
  • The holes seen below are divided into 15 degree increments, meaning the thruster can be angled in multiples of 15 (15, 30, 45, 60, 75, 90, etc.)
  • These were supposed to be for the 3D vectored thrusters, but unfortunately I didn't realize how little space there is for two vertical thrusters
  • I'll probably make a variant with space for two thrusters but mounted on the top edges instead of in the middle
  • However I'll still keep them in the design in case they prove to be useful later on
  • There are also mounting holes on the outside of the brackets for light modules, sensors, mounting brackets, etc.
  • Did a quick simulation on the brackets with 70N of force, maximum displacement was around 0.03 mm

Next tasks:

• [x] Add the electronics hull from blue robotics
• [ ] Design mounting brackets for the hull
• [ ] Add battery pod modules
• [ ] Design double thruster bracket
• [ ] Design light modules

[MFauzanAP]

I'll be closing this as done, I'll move the hull CAD work to a new task for next sprint.