This calculator balances an offset vertical load between two ideal supports. Enter their spacing, payload mass and load offset to find weight, overturning moment and the larger support reaction. A separate friction estimate assumes the total normal force acts at radius D/2; it is not an established upper bound on turntable drive torque.
Iron Frame Turn-table Interactive Calculator
Explore a static eccentric point-load balance across two supports and an upper-radius Coulomb-friction torque proxy.
Equation Used
- Payload is a vertical point load W at horizontal offset e along one diameter.
- Two ideal vertical reactions act at positions plus/minus D/2 on that same line.
- Rigid platform/frame with no self-weight and no other supports or anchors.
- Friction coefficient is applied to total normal force at selected radius D/2; actual bearing friction is not predicted.
- No bearing internal load distribution, race stiffness/contact angle, bolt/anchor tension, frame/plate deformation, self-weight, acceleration, shock, radial load, drive geometry, strength, fatigue, stability, guarding or safety model.
The larger ideal reaction is Rmax=W/2+M/D and the smaller is Rmin=W/2−M/D. If e>D/2, the smaller reaction becomes negative. Compression-only supports cannot provide that downward reaction, so this assumed support arrangement cannot balance the load.
Two-support equilibrium
Resolve an eccentric vertical point load onto two ideal supports spaced D apart. Force balance gives Rleft+Rright=W; moment balance gives the larger reaction W/2+We/D.
The static cross-section labels both reactions and flags a negative value for the smaller one. It does not simulate turntable rotation.
Use as a preliminary statics check
The reactions can check sign and order of magnitude for a simplified support line. They cannot select a slewing bearing, frame, drive, anchors or foundation.
Reaction and uplift condition
Rmax=W/2+M/D and Rmin=W/2−M/D. Since M=We, Rmin reaches zero at e=D/2. Beyond that, a compression-only two-support model tips; an actual structure needs anchors, a wider support polygon or other load paths.
T=mu W D/2 is only a Coulomb-friction proxy at the outer radius, not a bearing manufacturer's starting/rolling torque model.
Worked example
For 500 kg, D=600 mm and e=100 mm, W=4.903 kN and M=0.490 kN·m. Ideal maximum reaction is 3.269 kN and minimum is 1.634 kN. With mu=0.03 at radius 0.3 m, friction proxy is 44.13 N·m.
Limits of the support model
A real turntable distributes load through its frame, bearings and foundation. Their geometry and stiffness determine local loads; a two-support line cannot reproduce them. Starting friction, seals, acceleration and the drive mechanism also affect torque. The calculated reactions and friction estimate do not specify bearing, motor or structural capacity.
Questions
Is maximum reaction a bearing race load?
No. It is one ideal support reaction in a two-point line model.
What does negative minimum reaction mean?
The assumed compression-only supports would require uplift resistance or a different geometry.
Is friction torque a motor-sizing result?
No. Actual starting, rolling, seal, gear and acceleration torques are absent.
From torque to drive force
A drive-force calculation needs the actual connection geometry and resisting torque. This static support calculation does not include an actuator mount or its changing moment arm.
References & Further Reading
- Wikipedia contributors. Slewing bearing. Wikipedia
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