Magnetic Assemblies / Magnetic Wheels
Magnetic Wheels: Adhesion, Rolling Torque and Surface Adaptation
Magnetic wheels combine a rotating magnetic circuit with a tread, hub and drive interface for climbing or traction on ferromagnetic surfaces. Adhesion must remain stable through rotation, curvature, seams and dynamic loading.
Standard Round Magnetic Wheels — GDM-MW Series
The GDM-MW series offers nine standard round magnetic wheel sizes for wall-climbing robots, magnetic crawlers and inspection platforms operating on ferromagnetic steel surfaces. Outer diameters range from 25 to 160 mm, with listed pull forces from 55 to 2,940 N under the reference test conditions below.
Each wheel uses a two-pole NdFeB permanent-magnet arrangement: an axially magnetized N–S disc pair and steel yoke rings form the magnetic circuit. An H7 bore with a keyway provides a defined interface for shaft mounting. Compare the standard dimensions first, then review adhesion, traction and drive requirements for your application.
Standard Magnetic Wheel Specifications
Compare the nine standard models below. D, d, W, b and h are in millimeters; pull force is in newtons and wheel weight is in kilograms. Scroll the table horizontally on smaller screens.
| Part No. | D (mm) | d H7 (mm) | W (mm) | b (mm) | h (mm) | Pull force (N) | Weight (kg) |
|---|---|---|---|---|---|---|---|
| GDM-MW-25 | 25 | 8 | 16 | 3 | 8.6 | 55 | 0.054 |
| GDM-MW-32 | 32 | 10 | 18 | 4 | 11.1 | 80 | 0.100 |
| GDM-MW-40 | 40 | 12 | 20 | 4 | 13.1 | 120 | 0.200 |
| GDM-MW-50 | 50 | 16 | 25 | 5 | 17.3 | 200 | 0.350 |
| GDM-MW-63 | 63 | 20 | 32 | 6 | 21.7 | 330 | 0.700 |
| GDM-MW-80 | 80 | 25 | 40 | 8 | 26.7 | 630 | 1.450 |
| GDM-MW-100 | 100 | 30 | 50 | 8 | 31.7 | 900 | 2.800 |
| GDM-MW-125 | 125 | 40 | 62 | 12 | 42.1 | 1520 | 5.350 |
| GDM-MW-160 | 160 | 50 | 80 | 14 | 52.6 | 2940 | 11.40 |
Dimension key: D = wheel outer diameter; d H7 = bore diameter and tolerance designation; W = overall wheel width; b = keyway width; h = the bore-to-keyway dimension shown in the drawing. Use the dimension drawing to interpret h; it is not the keyway depth. Confirm the mating shaft, key and fit against the final drawing.
How to Choose a Standard Magnetic Wheel
1. Match the installation dimensions
Start with your shaft diameter and keyway, then check the available wheel diameter D and width W. The model suffix identifies the wheel diameter: for example, GDM-MW-50 has a 50 mm outer diameter, a 16 mm H7 bore and a 25 mm width. Also check wheel weight against the platform mass budget.
2. Check the working surface and contact gap
The listed pull forces are measured in direct contact with a 10 mm mild-steel plate. Paint, rubber running surfaces and other layers increase the magnetic gap and reduce effective pull force. Share the steel grade, plate thickness, coating thickness and surface curvature so the reference values can be assessed for your actual contact conditions.
3. Review adhesion and drive performance together
Use pull force to compare models under the same test conditions. It is not a payload rating or a guaranteed climbing capacity. Selection also depends on the number of wheels in contact, load distribution, friction, rolling resistance, travel orientation, acceleration and transitions over welds or seams. Check the motor, gearbox, shaft and bearings together with the wheel.
4. Confirm the model for your application
Send your preferred GDM-MW part number, platform weight including payload, wheel count, shaft drawing, travel speed and orientation, steel surface details, operating temperature and required quantity. GDM can review whether a standard model fits your requirements or whether a different bore, tread or wheel configuration should be considered.
For dimensions or operating conditions outside the standard range, include your drawing and application details in the enquiry. The engineering notes below explain the additional geometry, surface and dynamic factors to review.
Geometry and Dimension Definition
Use functional datums and define the magnetization reference on the drawing. The table below provides the minimum geometry information for a practical manufacturing review.
| Parameter | How to define it | Why it matters |
|---|---|---|
| Wheel OD | Tread outside diameter | Controls obstacle clearance and drive torque |
| Wheel width | Axial contact and magnetic width | Influences stability and available attraction |
| Hub interface | Bore, key, spline or bolt pattern | Transfers motor torque |
| Tread thickness | Rubber or protective layer over the pole system | Balances grip, wear and magnetic air gap |
Design Considerations
Dynamic adhesion
Evaluate the minimum attached area during rolling, not only a stationary full-contact force.
Surface curvature and seams
Wheel geometry and pole pitch must tolerate welds, steps and curved structures.
Drive torque
Magnetic normal force increases traction but also rolling resistance and motor load.
Manufacturing and Assembly Notes
- Loss of power does not guarantee a controlled stop on every orientation.
- Debris accumulation changes the air gap and can damage the tread.
- Sharp curvature may reduce contact to a small region.
- Strong attraction increases bearing and drivetrain loads.
Typical Applications
Climbing robots
Inspection of tanks, ships and steel structures.
Pipeline inspection
Traction on ferromagnetic pipe surfaces.
Cleaning equipment
Stable movement on vertical steel panels.
Remote NDT platforms
Carrying sensors over large structures.
Engineering Questions
How is wheel adhesion calculated?
Use the magnetic circuit at the worst rolling contact, then apply dynamic and safety factors.
Why add a rubber tread?
It improves grip and protects the surface, but also increases the magnetic gap.
Can one wheel suit flat and curved surfaces?
Sometimes, within a defined curvature range. Pole geometry and tread compliance must be evaluated.
What happens at weld seams?
Momentary gap growth and impact can reduce force; the wheel and suspension should bridge the discontinuity.
For a focused design review, share your drawing, operating temperature, air gap, target magnetic performance and annual volume through our enquiry page. You can also return to Magnetic Assemblies for material-level guidance.