Pump Water Tank Payload Design

Task Description

In order to deliver water, we’ll need somewhere to store it, this task is to design what we use to do so. We’re open to ideas for how we do this, but it needs to be fully sealed other than the pump inlet and outlet.

The tank can be made by us somehow, or can be a modified existing water tank of some kind, but you’ll need to figure out how this mounts to the drone.

If you have ideas to be able to “dump” the water from this (ie don’t need an exit pump) that will not leak, please write them out and we can discuss, but the initial scope of this will be just a tank solution.

Constraints

Tasks

• Research

• Tank design

• Component sourcing

• Component testing

• Manufacturing / mechanical installation

• Integration testing

Task Progression/Updates

Author: @Alison Thompson Date: Sep 25, 2024

Initial Ideas

We can experiment with how water-tight various 3D print materials are at different infills, then pick the lightest.

Ideally light weight PLA would work for this if we’re 3D printing, but off the shelf tanks should be investigated as well.

Research

@Megan Spee

Really liking the idea of an OTS container because it’ll be more reliable than 3D printing things, from my first look. Amazon link that I’ve been searching: https://www.amazon.ca/s?k=plastic+water+storage+tank+2.5L&crid=2XY0SQTAAPRKO&sprefix=plastic+water+storage+tank+2+5l%2Caps%2C149&ref=nb_sb_noss. Uline also a good place to look.

Tank requirements

• watertight

• able to install a pump/valve

• lightweight

Tank nice-to-haves

• baffles in the interior to prevent sloshing

Some COTS options:

• https://www.uline.ca/Product/Detail/S-22889/Jugs/Jerrican-1-1-4-Gallon-Natural (4.731765 litre, 410 g)

  • must buy 4x at a time, 13$ each. 52$ base

• https://www.uline.ca/Product/Detail/S-22920/Jugs/Square-Utility-Jugs-1-Gallon-Natural (3.78541 litre, 440 g)

  • must buy 12x at a time, 3.80$ each. 46.60$ base

Could install baffles in a COTS jug by cutting a slit into the side, pushing a flat piece of plastic in (about 50-75% of the way), and sealing the base of this piece into the cut exterior with epoxy.

Re: Oct 3 mech meeting, will be trying out 3D printed tank before buying COTS tanks.

Calculations for tank volume in PLA: https://docs.google.com/spreadsheets/d/13ZkewgjBpSqwBHvnumQ3UP_YPBGpoKL36r2nGgX6v9E/edit?usp=sharing

Assumptions for this tank:

• Cylindrical

• Fillet top and bottom 1 cm

• full area filled-in top and bottom

• thickness 4 mm

Rebower 12 x 12 Inch UHMW Polyethylene Sheets, 1/16 Inch Thick Ultra High Molecular Weight White Plastic Sheet [for Home, Industrial]

10 Pcs 1/4" OD Tube RO Water Straight Bulkhead Fittings Quick Connector RO Water System

1/4” tube activity

water tank fitting 4 Pcs PVC Bulkhead Fitting Double Threaded Bulkhead Water Tank Connector for Rain Barrels, Aquariums, Water Tanks, Tubs, Pools, Spigot, Black, 3/4 Inch Male 1/2 Inch Female

water tank fitting <> tube ZYAMY 2pcs Straight NPT Thread Adapter 3/4" FNPT to 1/4" Tube OD Push Fit Quick Connect Plastic RO Fittings Water Purifier Accessories

tube itself EZ-FLO 98560 PVC Clear Vinyl Tubing, 1/4 inch OD, 20 Ft

tube <> aquarium pump (1/2” female BSP to 1/4” OD push) uxcell 1/2 Inch BSP Female to 1/4 Inch OD Straight Quick Connect Water Purifiers Tube Fitting Push in to Connectors Water Hose Joint for RO Reverse Osmosis System 5pcs

Tank Design

Objective is a tank that holds 2.5 L of water securely and can infeed/outfeed water at request.

Nice-to-haves include vaguely aerodynamic design, easy to manufacture, assembles and disassembles quickly. Uses parts we already have/ are easy to get.

Captured in 2024-10-10 Mechanical Meeting Minutes

Open

Open

Idealized connection architecture shown above.

CAD shown below.

This screenshot does not have an o-ring groove. The printed one in ABS shown below includes that update. Bambulabs 0.20 mm white ABS

Component sourcing happening concurrently with design process.

Bunch of issues with parts arriving wrong/ not arriving.

With reference to purchase threads https://discord.com/channels/776618956638388305/1299101413342843011 and https://discord.com/channels/776618956638388305/1301328298659418112

I was looking at options with @ravoik, we can replace both fittings that did not arrive / arrived wrong with some tomfoolery (epoxy) we can throw the BSP 3/8"<>push-to-connect 1/4"OD directly into the tank. this connector:
uxcell 3pcs 3/8 Inch BSP Male to 1/4 Inch OD Straight Quick Connect Water Purifiers Tube Fittings Push Connector Water Hose for RO Reverse Osmosis Systems

action plan would just be to return the 1" (wrong size) o-ring connectors, Sarah goes ahead and gets a refund on the ones that didn't arrive, and we order another 15$ connector (and maybe buy some epoxy).

CAD Review

Notes from 2024-11-06 Pegasus Payload & Landing Gear + Eclipse CAD review

Water tank solution:

• 2.7 L internal volume > 2.5 L

• Change bolts attaching the top plate and the tank to M3 instead of M5s

• Polycarbonate for the top plate

  • look for gaskets instead of a funny o-ring

• Float sensor to measure water level for payload

• Chamfer the tube piece

• flip the counter-sink screws

• Maybe countersink the top plate, maybe not. Easier to manufacture if no countersink. ALso need to add space for the socket heads at the drone center block.

Standalone assembly (TANK_ASSY)

Unsuppressed on main assembly

Getting floats to check water levels - Micro Traders 2pcs Liquid Level Sensor PP Float Switch Float Sensor Switch with Wire Plastic Small Float Switch for Water Dispensers Water Heaters Humidifiers

Debate between this or current sense. issue with current sense is that tank must be full to generate a current feature. Requires a current sense shunt resistor on the water control board.

this table is kinda throw tbh but see https://discord.com/channels/776618956638388305/1112817387734057020/1307368097547812875 https://uwarg-docs.atlassian.net/wiki/spaces/Meetings/pages/2838495233/2024-11-14+Comp+Arch+Sync#Mechanical

Worksession 2024-11-16

Testing again. somehow failed to realize that the pump is NOT N/C (normally closed), and there needs to be a resolution to close the opening so that the water won’t drain out during inoperation.