tools / frc-tipping-calculator
Rigid-body statics for a drivetrain: the sideways acceleration that lifts two wheels, the cross-slope and ramp angles that do the same, whether it slides or tips first, and how hard it can push.
Geometry and weight defaults track the 2026 REBUILT manual, R103, R104 and R408. Friction figures are community estimates, not vendor specs, and they are yours to overwrite.
measure the CoG, don’t guess it
what is on the wheels
The highest-traction common FRC tread. Community values cluster from 1.1 to 1.3. The AndyMark blue-nitrile page lists no number at all.
verdict / stable
1.04 g sideways and 46.1 degrees of cross-slope before two wheels lift. The tread grips harder than the geometry, so it tips before it slides.
1.04g sideways before two wheels lift
1.04static stability factor
46.1°of cross-slope before it goes
the robot / five numbers decide it
lengths in
weight in
Side to side, wheel contact patch to wheel contact patch.
Front to back, wheel contact patch to wheel contact patch.
The number that dominates every result. Two inches out moves everything by 10 to 20%, so run a balance test.
Robot, bumpers and battery. 125 lb is a starting estimate, so weigh yours.
Roughtop or wedgetop sits at 1.1 to 1.3. Editing this switches to your own measurement.
1.0 for all-wheel drive. Lower it when some wheels are omnis or free casters.
CoG height is an estimate, not a rule value. Find yours with a balance-point or tip-angle test before you trust anything on this page.
the geometry / drawn from the front
front view / to scale with your numbers
The dashed line is the restoring lever. Shortening the track or raising the centre of gravity swings it upright, and once it passes vertical the robot is already going over.
what gives out first
how hard it can push
138lbf, 612 N
Force is the coefficient times the driven fraction times weight, so it is only as good as a number nobody publishes. Treat it as a range across 1.1 to 1.3, not as a figure to quote.
the working / nothing hidden
| what | formula | with your numbers |
|---|---|---|
| Static stability factor | SSF = track / (2 h) | 27.00 / (2 x 13.00) = 1.038 |
| Sideways lever arm | d = track/2 - sideways offset | 13.50 - 0.00 = 13.50 in |
| Tip acceleration, sideways | a = g d / h | 1.038 g = 10.18 m/s² = 33.4 ft/s² |
| Tip acceleration, fore and aft | a = g (wheelbase/2 - offset) / h | 1.038 g = 10.18 m/s² = 33.4 ft/s² |
| Cross-slope tip angle | theta = arctan(d / h) | arctan(13.50 / 13.00) = 46.08 degrees |
| Ramp tip angle | theta = arctan(d / h) | arctan(13.50 / 13.00) = 46.08 degrees |
| Slide or tip, sideways | slides when mu < d / h | 1.10 is at or above 1.04, so it tips first |
| Traction-limited push | F = mu x driven fraction x weight | 1.10 x 1.00 x 125.0 lb = 137.5 lbf |
which half of this you can trustTip accelerations, angles and the stability factor are exact rigid-body statics, so they are as right as the numbers you fed them. The push figure and the slide-or-tip verdict both hang on a friction coefficient that is empirical and varies with carpet age, wheel wear and dust, so read those as a range.
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