Parallel-Shaft vs Right-Angle Gear Motor: Which Fits Your Machine
Right-angle vs inline gear motor compared with real allowable load tables: efficiency, torque, the self-locking myth and how to decide in five steps.
Read MoreGearmotor selection looks like an engineering task and is usually finished as a commercial one. The engineer picks a ratio and a power rating; the buyer then has to compare three quotes that describe the same drive in three different ways, accept a sample that may or may not represent production, and commit to a lead time that decides whether the machine ships on schedule. This guide covers that second half — what to put on the enquiry, how to read competing quotes, how to test a sample properly, and what actually drives lead time.
The Enquiry Is the Specification
Most quote problems start with an incomplete enquiry. A supplier who receives “AC gear motor, 60 W, 1:50” will quote what they assume, and the assumptions are where cost and delay hide. Twelve items remove almost all of the ambiguity, and all twelve are things you already know or can measure.
| # | Specify | Why the supplier needs it |
|---|---|---|
| 1 | Required output speed (r/min) and tolerance | Fixes the ratio; tolerance decides whether a standard ratio is acceptable |
| 2 | Required output torque (N·m) at that speed | The actual sizing number; power alone does not define the drive |
| 3 | Duty cycle and starts per hour | Drives service factor, motor duty class and thermal margin |
| 4 | Supply: phase, voltage, frequency | Determines winding; 50 Hz and 60 Hz are different motors |
| 5 | Mounting: foot, flange, or shaft-mounted | Decides housing and flange machining |
| 6 | Shaft detail and keyway drawing | The most common custom item, and the usual cause of lead-time surprises |
| 7 | Brake: required holding torque and cycle rate | Brake size and wear life depend on both |
| 8 | Enclosure and environment: IP, washdown, ambient | Sealing, paint, lubricant and cooling all change |
| 9 | Orientation of installation | Oil level, breather and drain positions are orientation-specific |
| 10 | Overhung load, if a pulley or sprocket is fitted | Bearing and shaft rating must be checked against it |
| 11 | Noise, backlash or ingress limits, if the application has them | Otherwise unstated and unmeasured |
| 12 | Annual volume, first order quantity, required date | Decides whether the drive is a stock item or a production batch |
Send this as a table with a drawing attached, not as prose. Two suppliers quoting from the same table are comparable; two suppliers quoting from a paragraph are not.
Reading Three Quotes That Look Different
Price differences of 30–50% between quotes for nominally identical gearmotors are normal, and they are rarely explained on the quotation. The usual causes, in order of how much they matter:
- Torque quoted at a different speed. A “60 W, 1:50” unit rated at the motor’s own speed is not the same as one rated at the gearbox output. Ask for rated output torque at the specified output speed — this single question exposes most optimistic quotes.
- Gear material and process. Hardened and ground gears, or a different gear type entirely, cost more and last longer. A quote that does not state the gear type is quoting a category, not a product.
- Bearing and lubricant grade. Generic bearings and grease-filled-for-life housings are cheap; branded bearings and synthetic lubricant for high ambient are not.
- Actual ratio. A 1:50 nominal ratio may be built as 1:49 or 1:52. If your process depends on speed accuracy, state the tolerance on output speed rather than the ratio.
- Motor efficiency and winding. Copper mass and winding design differ between suppliers at the same rated power, and that difference shows up as temperature rise and life, not on the datasheet.
Comparison is easier when every supplier quotes against the same twelve items, and when you ask each one to state what is not included: brake, capacitor, terminal box, mounting bolts, cable gland and documentation all appear later as line items if they are not on the quote.
Validating a Sample in Six Tests
A sample that runs on the bench proves little. These six checks, most of which need no laboratory, separate a good drive from a marginal one before the purchase order is placed.
| Test | Method | What a failure looks like |
|---|---|---|
| 1. Speed and ratio | Measure output r/min at no load and at rated load on the intended supply | Slip much greater than the datasheet implies; speed outside the process window |
| 2. Temperature rise | Run at rated load for two hours, measure housing temperature above ambient | Rise above the supplier’s stated figure; a hot housing under rated load means the rating is optimistic |
| 3. Starting under load | Start the drive against a representative or slightly heavier load, several times | Failure to break away, or audible struggle, on a load it should start cold |
| 4. Brake function | Measure stopping distance and holding behaviour on the actual load, repeated | Creep after stopping; stopping distance that grows over repeated cycles |
| 5. Noise and vibration | Run at several speeds and listen at the gearbox, not the motor | Tooth-frequency whine, periodic knock, or resonance at a working speed |
| 6. Dimensional check | Verify shaft diameter, keyway, flange register and mounting hole positions against your drawing | Anything that requires reaming, shimming or filing at installation |
Record the results. A sample test that produces numbers becomes the acceptance criteria for incoming inspection, and it turns a subjective argument about a failed unit into a comparison against a documented baseline.
What Makes a Gearmotor Custom, and What That Costs in Time
Standard frames ship from stock or short production runs. The features below push the order into a batch build, and each one adds both lead time and minimum quantity:
- Non-standard supply voltage or frequency — the winding changes.
- Non-standard shaft diameter, length, keyway, or a hollow/splined shaft.
- A non-catalogue ratio, or a tightened backlash or speed tolerance.
- Special flange geometry or a mounting interface unique to your machine.
- Brake, encoder or connector configurations outside the standard option list.
- Special paint, washdown finish, or a lubricant for an unusual ambient.
Two design habits keep a project in standard territory: dimension the machine around a catalogue frame rather than around a bespoke shaft, and accept the nearest standard ratio with the resulting small speed error, compensating in the machine’s control rather than in the gearbox. Where a custom item is unavoidable, put it on the first order rather than the second, because tooling and process changes at scale are far more expensive.
The Cost That Does Not Appear on the Quote
A drive that fails in the field costs its price several times over in service labour, warranty administration and downtime, and the multiplication is much larger for a component buried inside a machine than for one on a shelf. That asymmetry is the argument for buying on documented torque margin rather than on unit price — and for keeping one spare per machine family rather than per machine model.
For applications where the drive is replacing a European brand, the comparison is rarely like-for-like on mounting dimensions alone; the SEW gear motor series overview and alternatives covers what to check before treating a unit as a drop-in replacement. Where the duty is genuinely pre-defined, such as small machine actuators, the range of small AC gear reducer motors can be matched from the catalogue rather than engineered from scratch.
Conclusion
Gearmotor selection ends when the specification is complete, the quotes are comparable, and a sample has been measured rather than admired. Write the twelve items, demand rated output torque at the specified speed, test the sample against your own load, and treat lead time as a function of customisation rather than of supplier goodwill. The practical gear motor selection guide covers the engineering sequence that feeds this commercial one.
FAQ
What information does a supplier need to quote a gearmotor?
Output speed, output torque at that speed, duty cycle and starts per hour, supply voltage and frequency, mounting type, shaft drawing, brake requirement, environment, installation orientation and annual volume.
Why are gearmotor quotes for the same power so different?
Usually because the torque was quoted at different speeds, or because the gear material, bearing grade, lubricant or motor winding differs. Compare rated output torque at your actual output speed before comparing price.
How long should a sample test take?
A day is usually enough for the six basic checks. A two-hour loaded run, a set of loaded starts, a brake cycle test and a dimensional check will reveal most of what a longer trial would.
Is a cheaper gearmotor acceptable for low-duty applications?
Often yes, provided the torque margin is documented and the drive is not buried inside a machine where replacement is expensive. On intermittent, accessible, light-duty equipment the price difference is genuinely worth taking.
What shortens gearmotor lead time most?
Staying on catalogue frames, ratios and voltages, and ordering the custom features at the prototype stage rather than after the machine is released to production.
