{"id":1978,"date":"2026-06-29T06:35:42","date_gmt":"2026-06-29T06:35:42","guid":{"rendered":"https:\/\/speed-reducer-gearbox.com\/electric-hoist-worm-reducer-torque-ratio-and-duty-cycle-guide\/"},"modified":"2026-06-29T06:35:42","modified_gmt":"2026-06-29T06:35:42","slug":"electric-hoist-worm-reducer-torque-ratio-and-duty-cycle-guide","status":"publish","type":"post","link":"https:\/\/speed-reducer-gearbox.com\/en\/electric-hoist-worm-reducer-torque-ratio-and-duty-cycle-guide\/","title":{"rendered":"Electric Hoist Worm Reducer: Torque, Ratio and Duty Cycle Guide"},"content":{"rendered":"
\n

An electric hoist sits at the intersection of duty cycle engineering and mechanical precision: the motor and gearbox together must handle hundreds of lift cycles per shift without overheating, while the load must be positioned accurately and held safely between lifts. This guide focuses on the three numbers \u2014 torque, ratio, and duty cycle \u2014 that define whether a worm reducer is the right choice and what specific variant to specify.<\/p>\n

Torque at the Drum: Starting Point for Every Selection<\/h2>\n

The gearbox output torque requirement for an electric hoist is frequently underestimated because engineers focus on the motor nameplate rather than the drum geometry. Output torque equals hook load (including block and slings, in newtons) multiplied by the drum radius at the outermost rope layer. For a 2-tonne SWL hoist with three rope layers on a 160 mm core drum (maximum radius approximately 200 mm after layers): load torque = 2 000 \u00d7 9.81 \u00d7 0.2 = 3 924 N\u00b7m. If the gearbox connects directly to the drum shaft, it must produce that torque \u2014 confirm the reeving arrangement before calculating.<\/p>\n

\"Electric<\/p>\n

Ratio Selection for Lifting Speed<\/h2>\n

Standard electric hoists lift at 4\u201312 m\/min. A 6 m\/min lift with a 150 mm effective drum radius requires the drum to turn at about 6.37 rpm. If the motor runs at 1440 rpm, the required ratio is 1440 \u00f7 6.37 \u2248 226:1. Single-stage worm ratios go only to 1:60, so either a two-stage EA double-stage worm reducer<\/a> or a single worm stage combined with a rope-drum reduction achieves the target. The EA series covers ratios to 1:900 in one housing \u2014 combining this with a 3:1 rope reeving gives a total mechanical advantage over 2 700.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Lift Speed (m\/min)<\/th>\nDrum Radius (mm)<\/th>\nRequired Drum RPM<\/th>\nGear Ratio Needed<\/th>\nWP Solution<\/th>\n<\/tr>\n<\/thead>\n
4<\/td>\n150<\/td>\n4.2<\/td>\n~340:1<\/td>\nWPE 1:300 + 1.1:1 pulley<\/td>\n<\/tr>\n
6<\/td>\n150<\/td>\n6.4<\/td>\n~225:1<\/td>\nWPE 1:200 + chain stage<\/td>\n<\/tr>\n
8<\/td>\n180<\/td>\n7.1<\/td>\n~203:1<\/td>\nWPE 1:200<\/td>\n<\/tr>\n
12<\/td>\n180<\/td>\n10.6<\/td>\n~136:1<\/td>\nWPE 1:100 + 1.36:1 chain<\/td>\n<\/tr>\n
20<\/td>\n200<\/td>\n15.9<\/td>\n~90:1<\/td>\nWPA 1:60 + 1.5:1 stage<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Input speed 1440 r\/min assumed throughout.<\/p>\n<\/div>\n

\"Double<\/p>\n

Duty Cycle \u2014 the Factor Most Often Ignored<\/h2>\n

Duty cycle is the ratio of on-time to total cycle time. An electric hoist running 5 minutes in every 10 operates at 50% ED. Worm gearboxes generate heat from mesh sliding friction regardless of load; at high ratios (1:30\u20131:60), efficiency can drop to 65%, meaning 35% of input power becomes heat in the housing. The equilibrium temperature is reached when heat loss through the surfaces equals heat input. If that equilibrium exceeds 95\u00b0C, oil degrades rapidly and seal life collapses.<\/p>\n

Thermal check:<\/strong> after one hour of normal operation, touch the housing near the worm shaft bearing. If the surface exceeds 60\u00b0C \u2014 uncomfortably hot to hold for 5 seconds \u2014 the unit is running warmer than desirable. Upgrade to VG 460 oil or the next frame size before continuing production.<\/div>\n

Choosing Between WPA and WPDA for Hoist Installations<\/h2>\n

The DKA hollow shaft series<\/a> with torque arm mounting eliminates the separate drum shaft and coupling hardware \u2014 the gearbox hollow bore slides over the drum shaft directly, which is the cleanest arrangement for small monorail hoists where every kilogram of dead weight reduces payload. The WPDA motor-flange series suits compact hoist frames where the motor mounts directly on the gearbox without an intermediate bell housing. The WPA foot-mount is preferable when the motor must be replaced independently in the field without removing the entire drive assembly.<\/p>\n

\"DKA<\/p>\n

Frequently Asked Questions<\/h2>\n
\n
\n1. What duty cycle is a WP worm unit rated for on hoist duty?+<\/span><\/summary>\n
The WP catalogue does not publish a direct duty cycle rating. A practical guideline: below 30% ED at full rated torque is manageable for most frame sizes in 25\u00b0C ambient. Above 50% ED, reduce load to 60\u201370% of rated or specify a frame one size up to increase heat dissipation surface area.<\/div>\n<\/details>\n
\n2. Can the self-locking property hold the load if the motor brake fails?+<\/span><\/summary>\n
At ratios of 1:30 and above in normal operating temperature conditions with clean oil, yes. However, this should be treated as a backup characteristic, not the primary safety mechanism. Australian crane and hoist standards require a rated brake independent of gearbox locking.<\/div>\n<\/details>\n
\n3. How do I prevent rope drum wobble affecting gearbox bearing life?+<\/span><\/summary>\n
Keep misalignment below 0.1 mm parallel offset and 0.1\u00b0 angular. Use a flexible jaw or disc coupling \u2014 not a rigid flanged coupling \u2014 unless the shaft alignment is confirmed within these tolerances after installation.<\/div>\n<\/details>\n
\n4. What happens if I run the hoist faster than rated by over-speeding the motor?+<\/span><\/summary>\n
Over-speeding the worm shaft above 1 600 r\/min increases sliding velocity and heat generation non-linearly. The bronze wheel surface temperature rises faster than housing temperature, and the oil film collapses locally before any alarm triggers. Wheel scoring and rapid wear typically follow within hours of operation above rated input speed.<\/div>\n<\/details>\n
\n5. Is a worm gearbox suitable for a VFD-controlled positioning hoist?+<\/span><\/summary>\n
Yes \u2014 worm gearing has essentially zero compliance backlash at the load holding position because the mesh is under constant load from gravity. The positioning accuracy is limited by rope stretch and drum geometry, not gearbox backlash. VFD ramp-up times of 2\u20134 seconds reduce shock torque on motor startup.<\/div>\n<\/details>\n<\/div>\n
\n

Get a Sized Recommendation<\/h3>\n

Share your load data and target speed \u2014 our team at Condell Park NSW returns torque calculations and a stock check within one business day.<\/p>\n

\n
\n
ADDRESS<\/div>\n

27 Harley Crescent
Condell Park NSW 2200<\/div>\n

\n
PHONE<\/div>\n

+61 2 9708 3322<\/p><\/div>\n

\n
EMAIL<\/div>\n

sales@speed-reducer-gearbox.com<\/p><\/div>\n<\/div>\n

Send Enquiry →<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

An electric hoist sits at the intersection of duty cycle engineering and mechanical precision: the motor and gearbox together must handle hundreds of lift cycles per shift without overheating, while the load must be positioned accurately and held safely between lifts. This guide focuses on the three numbers \u2014 torque, ratio, and duty cycle \u2014 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[2904],"tags":[],"class_list":["post-1978","post","type-post","status-publish","format-standard","hentry","category-hoisting-lifting"],"_links":{"self":[{"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/posts\/1978","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/comments?post=1978"}],"version-history":[{"count":0,"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/posts\/1978\/revisions"}],"wp:attachment":[{"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/media?parent=1978"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/categories?post=1978"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/speed-reducer-gearbox.com\/en\/wp-json\/wp\/v2\/tags?post=1978"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}