Magnetic Wheels for Wall-Climbing Robots

What Are Magnetic Wheels?

Magnetic wheels are magnetic assemblies designed to provide continuous attraction to ferromagnetic surfaces while allowing robots or mobile equipment to move along them.

They are widely used in wall-climbing robots for inspection, cleaning, and maintenance on steel walls, storage tanks, ship hulls, towers, and other ferromagnetic structures.

For wall-climbing robots, adhesion can be achieved through vacuum, mechanical gripping, magnetic attraction, and other methods.

Among these methods, magnetic wheels are particularly suitable for ferromagnetic structures because magnetic holding and locomotion can be combined within the same wheel system without requiring a separate adhesion mechanism.

Unlike stationary magnetic holding assemblies, magnetic wheels must maintain sufficient holding force throughout movement without creating excessive resistance. Their performance therefore depends not only on magnet strength, but also on the magnetic circuit, wheel geometry, working air gap, steel thickness, surface conditions, and the way loads are distributed between multiple wheels.

Magnetic wheel systems can use complete magnetic wheels or separate magnetic assemblies integrated into customer-designed wheel and tire structures. Specialized magnetic arrangements such as Halbach arrays can also be considered for wheel designs with a larger working gap, particularly when non-magnetic tires are used for improved traction, wear resistance, or surface protection.

Magnetic Adhesion Systems for Wheeled Wall-Climbing Robots

Wheeled wall-climbing robots can combine locomotion and magnetic adhesion in different ways. In conventional magnetic wheel systems, the wheels provide both functions. Another approach uses non-magnetic wheels for locomotion and separate magnetic assemblies mounted on the robot to provide magnetic adhesion to the steel surface.

Magnetic Wheels

Conventional magnetic wheels commonly combine a ring-shaped permanent magnet with ferromagnetic steel wheel discs on both sides.

The steel discs form part of the magnetic circuit, directing magnetic flux toward the wheel circumference and the steel surface. In this configuration, the wheels provide both locomotion and magnetic adhesion.

Magnetic wheels work most effectively with a small working gap. Adding non-magnetic tires increases the distance between the magnetic circuit and the steel surface and can significantly reduce the available magnetic holding force during operation.

This creates a design trade-off when tires are required to increase friction, reduce mechanical wear, or protect the surface being traversed.

Magnetic Circuit in Magnetic Wheels

Separate Halbach Magnetic Assemblies

Another approach separates locomotion from magnetic adhesion. Rubber, polyurethane, or other non-magnetic wheels can be used for movement, while separate Halbach magnetic assemblies are installed on the underside or other suitable positions of wall-climbing robots.

Halbach arrays use permanent magnets with progressively changing magnetization directions to produce an asymmetric magnetic field, with a stronger field on one side of the arrays and a weaker field on the other. In wall-climbing robots, the stronger field side faces the steel surface to provide magnetic adhesion.

Separating the magnetic assemblies from the wheels allows wheel materials and tire structures to be selected primarily for traction, wear resistance, and surface protection. The magnetic assemblies can then be designed around the required working gap and holding force independently of the wheel contact structure.

Magnetic Circuit in Halbach Arrays

What Determines Magnetic Holding Performance?

The holding force required from each magnetic wheel or magnetic assembly depends on robot weight, wheel arrangement, load direction, acceleration, friction, and the required safety margin. These factors determine the magnetic force needed to keep wall-climbing robots securely attached during both stationary and moving conditions.

Magnetic design must also account for the working gap, steel thickness and magnetic properties, surface curvature, magnetic circuit geometry, magnet grade, and available installation space. Together, these factors determine the holding force available at the actual working surface.

The working gap is particularly important. Tire thickness, installation clearance, non-magnetic layers on the steel surface, and local surface unevenness can all increase the distance between the magnetic system and the steel. Holding force decreases as this distance increases, making the expected operating gap an important input to magnetic design.

Wheel and magnetic assembly dimensions are not determined by holding force alone. Robot size, chassis geometry, wheel spacing, ground clearance, and available mounting space can also influence the required dimensions. A large but relatively lightweight robot may therefore need larger magnetic wheels even when its holding-force requirement is modest.

Magnetic Wheel and Halbach Assembly Specifications

The following tables provide available specifications for magnetic wheels and Halbach magnetic assemblies used in wheeled wall-climbing robots. The available models cover a range of sizes and holding forces for different robot layouts and load requirements. Holding performance should be evaluated based on the actual working gap, steel surface conditions, and operating environment.

Magnetic Wheels

Model	D (mm)	d (mm)	T (mm)	b (mm)	h (mm)	Holding force (N)	Unit weight (g)
W25	25	8	16	3	8.6	55	54
W32	32	10	18	4	11.1	80	100
W40	40	12	20	4	13.1	120	200
W50	50	16	25	5	17.3	200	350
W63	63	20	32	6	21.7	330	700
W80	80	25	40	8	26.7	630	1450
W100	100	30	50	8	31.7	900	2800
W125	125	40	62	12	42.1	1520	5350
W160	160	50	80	14	52.6	2940	11400
Notes: Standard magnetic wheels have a maximum operating temperature of 100°C. The listed holding forces are measured at room temperature against a 10 mm thick steel plate. Actual holding force may vary with the working gap, steel thickness, surface condition, and operating temperature.

Halbach Magnetic Assemblies

Model	R (mm)	L (mm)	W (mm)	H (mm)	M	Holding force (N)	Unit weight (g)
HB5040	50	40	76	36.5	M4	490/230/150	550
HB5060	50	60	76	36.5	M4	820/400/260	830
HB5080	50	80	76	36.5	M4	1150/570/380	1100
HB8040	80	40	115	51	M5	730/400/300	1150
HB8060	80	60	115	51	M5	1250/730/540	1680
HB8080	80	80	115	51	M5	1750/1050/800	2200
HB10040	100	40	152	62	M5	850/480/340	1750
HB10060	100	60	152	62	M5	1500/900/650	2550
HB10080	100	80	152	62	M5	2150/1300/950	3400
HB100100	100	100	152	62	M5	2800/1700/1250	4250
HB12040	120	40	172	70	M5	1000/600/420	2250
HB12060	120	60	172	70	M5	1750/1100/800	3280
HB12080	120	80	172	70	M5	2500/1600/1200	4320
HB120100	120	100	172	70	M5	3250/2100/1600	5350
HB15040	150	40	200	77	M6	1200/750/560	2950
HB15060	150	60	200	77	M6	2100/1350/1050	4250
HB15080	150	80	200	77	M6	3000/2000/1550	5650
HB150100	150	100	200	77	M6	3950/2550/2050	7100
HB150120	150	120	200	77	M6	4850/3250/2550	8400
Notes: The table lists overall dimensions only. Contact our team for detailed dimensional information. Holding force values are measured at working gaps of 0, 3, and 5 mm against a 10 mm thick steel plate.

What Are Magnetic Wheels?

Magnetic Adhesion Systems for Wheeled Wall-Climbing Robots

Magnetic Wheels

Separate Halbach Magnetic Assemblies

What Determines Magnetic Holding Performance?

Magnetic Wheel and Halbach Assembly Specifications

Magnetic Wheels

Halbach Magnetic Assemblies

Discuss Your Magnetic Wheel Requirements