Top 7 Industrial Gear Reducer Series: R, F, K, S, P, H/B, ZDY

An industrial gear reducer sits between the motor and the driven machine, cutting speed and multiplying torque so that a standard 4-pole motor can drive a conveyor, mixer, mill or hoist at the speed the process needs. This is our ranking of the seven gear reducer series we build at Yanfeng Group, ordered by torque and power range multiplied by application breadth, with the catalogue figures for each on one page. Our recommendation in short: for general factory drives up to 160 kW buy the R series coaxial helical geared motor; for a right-angle drive or torque up to 49,400 N·m buy the K series; for heavy industry above 200 kW choose the H/B series industrial gearbox, or the P series planetary when the output turns slower than 60 r/min. We have left out our two single-purpose units, the T series spiral bevel steering box and the SWL screw jack, because each is built for one task (turning a shaft line through 90 degrees at ratios of 1:1 to 5:1, lifting a load of 1 to 100 t) rather than for general speed reduction; both remain on the gear reducers page.

Key definitions

• Geared motor: a gear reducer with an AC motor flanged directly to its input, so the two are ordered and installed as one unit (our R, F, K and S series).
• Permissible output torque: the highest torque a frame size may deliver continuously under steady load; the reducer is chosen so this figure is above the driven machine's demand multiplied by the service factors.
• Ratio (i): input speed divided by output speed; as an illustration, an input of 1450 r/min at ratio 30 gives an output of roughly 48 r/min.
• Service factors f1, f2, f3: multipliers for the driven-machine load character, the prime mover and the number of starts, applied as T_N >= T2 x f1 x f2 x f3.
• Mounting position M1 to M6: the orientation the unit is installed in; it fixes where the breather, oil sight glass and drain plug go, so it must be stated on the order.
• Hardened tooth flank: gears in alloy steel that are carburised, quenched and precision ground, which lets the H/B and ZDY/DBY series carry heavy loads in a compact housing.

Comparison table

Figures are the range across all frame sizes of each series, taken from the catalogue selection tables. Power and torque ends belong to the smallest and largest sizes; ratio ends can come from mid-range sizes. Where the catalogue gives no single figure for a series, the cell says so.

Rank	Series	Shaft arrangement	Frame sizes	Motor / input power	Ratio range	Max output torque
1	R series (YFR)	coaxial helical, in-line	13 (R17–R167)	0.12–160 kW	approx. 3.37–289.74	17,700 N·m
2	K series (YFK)	right-angle helical-bevel	12 (K37–K187)	0.18–200 kW	approx. 5.36–197	49,400 N·m
3	F series (YFF)	parallel-shaft helical	10 (37–157)	0.12–200 kW	approx. 3.77–281.71	16,800 N·m
4	H/B series (YFH / YFB)	parallel-shaft or right-angle, 1–4 stages	22 (1–22)	2.52–5366 kW	1.25–450 nominal, assembled from per-type tables (H1SH 1.25–5.6 to H4/B4 80–450)	470,000 N·m
5	P series (YFP)	planetary, 2–3 stages, optional bevel or helical input stage	sizes 9–36	0.4–1293 kW	no single catalogue range (YFP2N table: 25–40; output speed 0.19–60 r/min)	2,600,000 N·m
6	ZDY / DBY series	parallel-shaft cylindrical or bevel-cylindrical, 1–3 stages	ZDY 80–560; ZLY 112–710	approx. 5–6666 kW nominal input (ZDY table)	1.25–100 (ZDY/ZLY/ZSY); 8–50 (DBY/DCY)	no torque figure in catalogue; rated by nominal input power
7	S series (YFS)	right-angle helical-worm	7 (S37–S97)	0.12–22 kW	approx. 6.8–290	3,990 N·m

1. R series helical gear reducer (YFR)

The R series is our coaxial, in-line helical geared motor and the general-purpose unit of the range, which is why it heads the list. Thirteen frame sizes from R17 to R167 span input powers of 0.12 to 160 kW, ratios of about 3.37 to 289.74 and permissible output torques from 87 N·m (R17) to 17,700 N·m (R167); the mid-range R87 is rated 1,310 N·m and R107 4,380 N·m. A single-stage YFRX variant in sizes 37 to 107 covers low ratios of about 1.3 to 6.63. It is ordered foot-mounted, B5 flange-mounted or foot-plus-flange, in six mounting positions with the terminal box at 0, 90, 180 or 270 degrees. Buy it for general-purpose drives wherever the motor can sit in line with the driven shaft.

2. K series helical/bevel gear reducer (YFK)

The K series puts a helical input stage in front of a spiral-bevel output stage so the output shaft is at 90 degrees to the motor. It carries the highest torque of our four geared-motor series: twelve frame sizes from K37 to K187, input powers 0.18 to 200 kW, ratios of about 5.36 to 197 and permissible torques from 156 N·m up to 49,400 N·m at K187 (K107: 7,210; K127: 13,000; K157: 17,800; K167: 31,500 N·m). Foot, flange, hollow-shaft and hollow-shaft-with-flange mounting are available, with the output shaft on side A, B or both. Because the spiral bevel gears bear load in one direction only, state the rotation direction viewed from the output shaft when ordering. Choose it for any layout where the motor must sit at 90 degrees to the driven shaft, or where an in-line unit does not reach the torque.

3. F series parallel axes helical gear reducer (YFF)

The F series carries its input and output shafts on parallel axes in a flat housing, with the motor flanged directly to the gear unit. Ten frame sizes from 37 to 157 cover 0.12 to 200 kW, ratios of about 3.77 to 281.71 and permissible output torques from 196 N·m to 16,800 N·m. Its strength is the mounting range: B5 and B14 flanges, a hollow output shaft (YFA, YFAF, YFAZ), foot and foot-plus-flange versions, single-stage YFX units and an extended-bearing-housing version, all in six mounting positions. Buy it for conveying and other drive duties where a compact parallel-shaft unit, or a hollow shaft mounted on the driven shaft, suits the layout.

4. H/B series high power speed reducer (YFH / YFB)

The H/B series is our modular industrial gearbox for drives beyond the geared-motor range. YFH is the parallel-shaft helical type and YFB the right-angle bevel-helical type; both use carburised, quenched, hardened tooth flanks and are built with one to four stages in 22 frame sizes. Motor powers run from 2.52 kW to 5366 kW, output speeds from 1.7 to 1200 r/min and output torque up to 470,000 N·m; the per-type tables give nominal ratios from 1.25 to 5.6 for single-stage H1SH units up to 80 to 450 for four-stage H4/B4 units. Output is a solid shaft, a hollow shaft or a hollow shaft with shrink disk, mounted horizontally with or without feet, or vertically. Dip lubrication is standard; forced lubrication, fan cooling and cooling coils are available, with thermal-capacity tables for each. Choose it for large belt conveyors (the catalogue's worked example is a blast-furnace feed conveyor) and other heavy drives that must carry large axial and radial loads.

5. P series planetary speed reducer (YFP)

The P series planetary reducer delivers the highest torque in our range, up to 2,600,000 N·m, from a unit that is light and small for its rating because involute planetary gearing splits the power across several planet wheels. Two- or three-stage units (YFP2, YFP3) in sizes 9 to 36 take motors from 0.4 to 1293 kW and give output speeds of 0.19 to 60 r/min; a bevel, helical or bevel-helical input stage can be added for right-angle or offset input. Output shafts are hollow with shrink disk, hollow with involute splines, solid with parallel key or solid with splines, foot- or flange-mounted, horizontal or vertical. The catalogue's worked example selects a YFP3N-AZ-17-225-B500-96 for a 75 kW, 1500 r/min belt conveyor at ratio 227. Buy it for slow, high-torque duties in metallurgy, mining, hoisting and transport, power and energy, construction materials, light industry and traffic.

6. ZDY / DBY series cone-column gear reducer (YFZDY / YFDBY)

The ZDY/DBY series is our hardened-gear reducer designed and built to Chinese national standards: centre distance and nominal ratio are optimised at the design stage and the main parts are interchangeable. Parallel-shaft cylindrical types are YFZDY (single stage, ratio 1.25 to 6.3), YFZLY (two stage, 6.3 to 20) and YFZSY (three stage, 22.4 to 100); right-angle bevel-cylindrical types are YFDBY (two stage, 8 to 14) and YFDCY (three stage, 16 to 50), each with a K hollow-shaft version and a KD shrink-disc option. ZDY sizes run from 80 to 560 and ZLY from 112 to 710, with nominal input powers in the ZDY table from about 5 kW to about 6666 kW at 750, 1000 or 1500 r/min input. Choose it for conveyors, mills, mixers, cranes and metallurgical, mining and chemical equipment where a national-standard reducer is specified.

7. S series helical gear/worm reducer (YFS)

The S series closes the list because it is the smallest in power, but it earns its place with a wide ratio range, roughly 6.8 to about 290, in a single compact unit. A helical first stage drives a worm and worm wheel, giving a compact, quiet right-angle unit: seven frame sizes from S37 to S97, input powers 0.12 to 22 kW, ratios of about 6.8 to 290 and permissible torques from 93 N·m to 3,990 N·m (S67: 520; S77: 1,170; S87: 2,130 N·m). Foot, flange, hollow-shaft and hollow-shaft-with-flange mounting are available, with the output shaft on side A, B or both. Buy it for compact, quiet, high-ratio right-angle drives up to 22 kW.

How to choose

1. Start from the driven machine's torque and speed. Convert the required output speed into a ratio against a 4-pole motor and note the torque at that speed.
2. Apply the service factors. Multiply the torque by f1 (driven-machine load character), f2 (prime mover) and f3 (starts per hour); the reducer's permissible torque must be at least the result.
3. Pick the series by power band. Up to 22 kW with a high ratio in a small space: S. Up to 160 to 200 kW: R (in-line), F (parallel shaft, hollow output) or K (right angle, highest torque). Above 200 kW or above 49,400 N·m: H/B or ZDY/DBY, or P when the output is below 60 r/min.
4. Fix the shaft arrangement and output. In-line, parallel or right angle; solid keyed shaft, hollow shaft or hollow shaft with shrink disk; output on side A, B or both.
5. State the mounting position and orientation. M1 to M6 for geared motors, horizontal or vertical for the industrial units, plus terminal box position and, for K units, the rotation direction.
6. Check thermal capacity for the big units. For H/B, P and ZDY/DBY, compare the thermal rating for your ambient conditions with the transmitted power and add the cooling or forced lubrication the series offers if needed.

Send the driven machine's torque, speed, daily hours and starts per hour through the enquiry form and we will help you arrive at a type designation. For the method behind those factors, read our guide on how to select a gear reducer from the R, F, K and S series.