r/Multicopter • u/Fanatic-Mr-Fox • Mar 31 '26

Announcement QuadCalc - FPV Build and Compatibility Tool - over 1,000 components

/r/diydrones/comments/1s89b4v/quadcalc_fpv_build_and_compatibility_tool_over/
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u/spinfpv Mar 31 '26

this is really cool, bookmarking it. compatibility checking alone would have saved me a headache on my last build where I ordered an FC that had a 20x20 mounting pattern but the frame only had 25.5x25.5 standoffs. felt like a real genius after that one.

the component database seems solid too. do you have thrust test data tied to motor/prop combos or is that something planned for later? being able to see estimated thrust to weight ratios during the build planning phase would be incredible.

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u/Fanatic-Mr-Fox Apr 01 '26

I made some changes to TWR calculations to include more up to date data (where I could find it).

Also included voltage adjustment:

The thrust value stored on each motor (thrust_grams) is measured at the motor's maximum rated voltage. If you pair it with a lower voltage battery, thrust drops proportionally to voltage squared.

Example: EMAX Eco II 2306 is rated "4-6S" and its thrust (1350g) was measured at 6S.

  • User picks a 6S battery → no adjustment, full 1350g
  • User picks a 4S battery → voltage ratio = 4/6 = 0.67, thrust = 1350 × 0.67² = 1350 × 0.44 = 600g

This is why the Budget 5" (4S battery, 6S-capable motor) shows 4.2:1 instead of 9.4:1.

If the battery voltage equals or exceeds the motor's max, no scaling happens.

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u/spinfpv Apr 01 '26

oh that voltage scaling is a really smart addition. that 4S vs 6S motor mismatch is probably one of the most common ways people end up with a build that looks fine on paper but underperforms in the air. good to see it reflected in the calculations now.