A coupling in a drive rarely warns you of failure in advance: first runout appears on the shaft, then noise and vibration grow, and eventually the pins break up and the line stops. Rubber elastic inserts age from oil, ozone and thermal load within months, so the maintenance technician is forced to stock them by the box. A polyurethane coupling from the TIMOL plant delivers 2-5 times the service life of rubber, holds its elasticity across a wide temperature range, and turns the replacement of the elastic element from an emergency into a planned job. Let’s look at how such a coupling is built, why polyurethane beats rubber and steel, and how to order an insert to your drawing.
What polyurethane couplings are and what problem they solve
A polyurethane coupling transmits torque between two shafts while damping shock and torsional vibration in the drive. The elastic polyurethane element, whether pins, a spider, bushings or a solid insert, deforms under load, stores the energy of an impact and releases it smoothly, protecting the motor, gearbox and bearings from abrupt loads.
Thanks to its elasticity, polyurethane compensates for shaft misalignment: the axial, radial and angular offset that always arises during assembly and thermal expansion of equipment. This is the core working function of an elastic coupling. Steel does not perform it, and rigid polymers such as cast nylon crack on impact.
TIMOL’s open-cast technology lets an elastic element of any profile be reproduced: pin, jaw, spider or bushing type. Hardness, shape and dimensions are set at the casting stage for the customer’s specific hub, so a new insert seats into the standard mounting location without any rework of the assembly.
Why polyurethane beats rubber, steel and cast nylon in couplings
TIMOL polyurethane combines the qualities that matter most for a coupling: high wear resistance, rebound elasticity and oil resistance, none of which any classic material offers all at once. Abrasion loss per DIN 53516 for polyurethane is 38-39 mm³, whereas for SBR rubber it reaches 100-200 mm³ and for NBR rubber 80-150 mm³. A polyurethane elastic insert wears several times slower than a rubber one under the same load.
Rubber loses out on more than wear. Tensile strength is 8-20 MPa for SBR, 10-25 MPa for NBR, and 39-87 MPa for TIMOL polyurethane. That means polyurethane pins withstand higher torque without rupturing. Natural rubber has higher rebound (40-75%), but its upper working temperature is only +70 °C and its oil resistance is poor, so in an industrial drive next to a gearbox it ages fast.
Cast nylon (polyamide PA6/PA66) is sometimes used in rigid jaw couplings. Its abrasion loss (30-90 mm³) is decent, but its rebound elasticity is only 5-15%: under shock load it does not cushion, it chips. Polyurethane at 70 Shore D delivers comparable wear resistance while still damping the impact and returning to shape. Steel simply does not work as an elastic element: it does not damp, does not compensate misalignment, corrodes, and is 6-7 times heavier than polyurethane.
Engineer’s tip: don’t chase maximum hardness. Balance is what matters for a coupling: too soft an insert overloads and creeps under torque, too hard an insert stops damping impacts and passes them through to the bearings. For medium drives, start at 85-95 Shore A and adjust to the actual wear. And always degrease the seating surfaces before assembly: an oil film on the pins accelerates their pull-out from the sockets.
Comparison of materials for elastic couplings
The table below shows the difference between polyurethane and common alternatives using real reference figures. For an elastic element, the key parameters are abrasion, tensile strength and rebound.
| Material | Abrasion DIN 53516, mm³ | Working t, °C | Hardness | Tensile strength, MPa | Rebound elasticity, % |
|---|---|---|---|---|---|
| TIMOL polyurethane | 38-39 | -60 to +100 | 85A-95A | 39-87 | 34-61 |
| NBR rubber | 80-150 | -30 to +100 | 40A to 90A | 10-25 | 20-45 |
| SBR rubber | 100-200 | -40 to +80 | 40A to 80A | 8-20 | 30-55 |
| Natural rubber NR | 60-130 | -50 to +70 | 30A to 80A | 20-30 | 40-75 |
| Cast nylon PA6/PA66 | 30-90 | -40 to +100 | 75D to 85D | 60-85 | 5-15 |
| Carbon steel | n/a | -40 to +500 | 120-250 HB | 370-700 | n/a |
Polyurethane has the lowest abrasion loss among elastomers while keeping an elasticity that cast nylon lacks. This exact combination explains why a polyurethane insert lasts 2-5 times longer than a rubber one and does not chip like a cast-nylon one on a shock-loaded drive. For the range of elastic elements and related parts, see the catalog of polyurethane products.
Which industries use polyurethane couplings
Polyurethane couplings work in drives wherever there is shock or cyclic loading and misalignment compensation is required. The plant’s overall product line covers 12 industrial sectors, and couplings are in demand in most of them.
The mining and mineral-processing industry uses elastic couplings in the drives of conveyors, crushers and feeders, where impacts on the transmission are constant. Metallurgy fits polyurethane inserts into the drives of rolling and transport lines. Pump and compressor equipment, where the motor shaft is coupled to the pump shaft, needs a coupling that damps pulsations and tolerates contact with oil.
Agricultural machinery and the food industry value polyurethane for its resistance to moisture and washing solutions and for the fact that the part does not corrode. The automotive and repair segment uses polyurethane elements in the elastic couplings of drivelines and drives, where a rubber equivalent quickly loses its elasticity. In all these cases the deciding factor is the same: polyurethane holds torque longer and calls for line stoppages less often.
How polyurethane couplings are made and installed
Manufacturing begins with the customer’s drawing or a sample of the coupling hub. The process engineer determines the type of elastic element, the hardness for the calculated torque, and the polymer formulation for the working medium. The element is then open-cast into a mould, cured at a controlled temperature for several hours, and, where needed, machined to the exact seating dimensions.
Installing a polyurethane insert is simple and does not change the coupling’s design. Pins or bushings go into the standard sockets of the hub, and a spider is clamped between the jaws. Before installation the surfaces are cleaned and degreased, and the fit is made without hammering, so as not to damage the element. When worn, only the polyurethane part is replaced; the metal hubs stay in service.
This approach delivers the main saving: instead of buying a complete coupling, the enterprise restores the assembly by replacing a single inexpensive insert. The casting and surface-preparation technology is described in more detail in the reference information section.
How to order couplings to your drawing
To order polyurethane couplings, provide a drawing or a sample of the elastic element with seating dimensions and describe the operating conditions: torque, load character, working medium and temperature range. This data is enough to select the hardness, shape and polymer formulation.
The TIMOL plant produces both single inserts for repairs and serial batches, as well as non-standard elements to a sketch. Once the technical specification is agreed, the lead times and manufacturing terms are set. For a consultation, a calculation for your assembly and an order, get in touch through the TIMOL plant contacts.