# Motor and weight screen (R7)

## Direct result
The present 2216/10x4.5 lift setup does not meet the selected 1.5 thrust-to-weight screening target at any current estimated takeoff mass. The printed custom geometry sums to 3,627 g solid-equivalent after excluding duplicate test forks, fit coupon and hinge pin/sleeve pieces. A 65–100% structure factor plus 650–1,000 g avionics/battery and 450 g booms/spars/fasteners produces 3,458–5,077 g estimated AUW. These are explicit assumptions, not measured print or scale weights.

Four lift motors should each demonstrate at least 1.5 × AUW / 4: 1,297–1,904 g across that range. At the 1,200 g per-prop limit T-Motor publishes for AIR2216II/T1045, maximum total thrust is 4,800 g. This implies a 3,200 g aircraft limit at 1.5:1 before altitude, temperature, battery sag, control margin, rotor interference, or motor-out considerations. Thus the current 2216 selection fails the screen.

## Replacement candidate
T-Motor U3 KV700 with T-Motor 13x4.4CF is the stronger documented candidate for a redesigned lift module. Manufacturer data gives 1,800 g at 14.8 V, 19.4 A, 287 W per motor; motor mass 128 g with cables; compatible 3–4S, 25 A continuous motor current and stated 500 W max. Four tested motors imply 7.2 kg peak static thrust and 1.5 TWR only through 4.8 kg AUW. That barely includes the lower estimated mass and fails the upper estimate; no margin remains at the threshold. A 40 A ESC is listed as relevant by the manufacturer, but must be confirmed against exact chosen voltage/prop data and cooling.

The U3 13-inch prop raises diameter from 254 to 330 mm. At existing rotor centers x=90/650, y=±400, pairwise disk-center spacing is 560 mm fore-aft and 800 mm across. Nominal disk edge gap is therefore 230 mm longitudinal and 470 mm lateral; center-to-body clearance is 400 mm transverse. This is only a plan-view rigid-disk check. It does not cover blade flex, mounting vibration, wing/boom deformation, prop adapters, blade planform, mount failure, or rotor wash.

**Decision:** keep the 2216 choice rejected for current estimated mass; treat U3 KV700/13x4.4 as a candidate requiring a much lighter structure, exact CAD mounts, measured AUW, calibrated thrust stand, and battery/ESC thermal validation. Do not buy based only on this screening. A 1.5 ratio is not a substitute for design/flight qualification.

## Sources
[T-Motor U3 product, test table and technical drawing](https://store.tmotor.com/product/u3-motor-u-power.html). [T-Motor AIR2216 combination](https://store.tmotor.com/product/air-gear-450II-combo-set-no-esc.html). [Official Holybro X500 CAD downloads](https://docs.holybro.com/drone-development-kit/px4-development-kit-x500v2/download). No physical rotor spin, thrust, structural, thermal, electrical, flight or CFD test was performed. Published static thrust points are manufacturer laboratory data, not measurements on this aircraft.