Most first enquiries to a motor factory contain two questions: price, and lead time. Both are worth having, and neither can be answered properly until a third thing exists, which is a defined specification. A quotation against an undefined specification is not a price, it is a number attached to a different product, and comparing two of them is how projects end up with a motor that meets the drawing and not the machine.

The questions below are the ones whose answers change what you build. They are worth asking before the sample stage, because most of them are cheap to answer and expensive to discover later.

Ask for Your Operating Point, Not the Rated One

A catalogue torque figure is quoted at a speed. Your machine runs at its own speed, which is almost never that one.

The gap is not small. In the published configurations of the ZGB37RG, the 12V version is listed at 60 rpm with no load and 42RPM at rated torque, and the 24V version at 30RPM and 21RPM. Both lose exactly thirty percent of their no-load speed by the time they reach rated torque. So a motor described as delivering a given torque is delivering it at a lower speed than the headline suggests, and a machine designed around the catalogue speed will run slower than planned.

The question to ask is therefore specific: at my output speed, what torque is available, what current does it draw, and what is the drop from no-load to rated? A supplier who can answer that from measured data is a different kind of supplier from one who forwards a PDF.

The same applies to the gearbox. Ratio range, backlash, duty cycle, mounting orientation and bearing type all have to be settled together, and none of them is a separate decision from the others. Once the ratio is fixed, the mounting orientation is still open, and the orientation changes how the bearing carries the load.

Ask Which Tolerances Are Actually Guaranteed

Nominal dimensions are easy to agree and rarely the source of trouble. Tolerances are the contract, and three of them cause most of the disputes.

Shaft extension length is quoted with a minus-only tolerance in the relevant standard, so a shaft shorter than nominal is compliant and a longer one is not. A customer who measures a new motor and finds it a fraction short has found a conforming part. Knowing this in advance prevents an argument and prevents the real failure, which is a shaft long enough to bottom out inside the mating bore.

Backlash is quoted either in degrees or in arcminutes, and one degree is sixty arcminutes, so the two units are not comparable at a glance. It is also measured at a stated torque, and a figure taken at no load describes clearance rather than what the axis sees under load. Ask for the unit and the measuring torque together.

Ingress protection is a static laboratory test of the assembly as it was built. It says nothing about condensation, and it does not survive a changed connector or an upward-facing terminal box. A rating quoted without the test conditions is a label rather than a specification.

Ask What a Sample Proves

A sample proves that the drawing can be built once. It does not prove that the next thousand will match it, and treating it as proof of the second thing is the most common error in this process.

What a sample can show is fit, function, noise character and whether the performance data describes the part in your hand. What it cannot show is process stability. For that, ask for a run of measurements from a single batch rather than a single certificate, and ask what the spread is on the two or three parameters that matter to your machine. A manufacturer who can produce that has a process. One who can only produce a sample has a sample.

Ask also for the conditions behind any figure you are given. A torque quoted at 20 °C and a nominal voltage is a different number from the same motor at 60 °C in a closed housing, and a noise figure without a distance and a load is not a figure.

Ask for the Documents, and the Revision Number

Test records, a material declaration, and insulation resistance results are the three that arrive with a shipment and are worth reading. But the document that prevents the most expensive kind of surprise is the drawing revision the parts were built to.

A motor can be changed without anyone intending to: a different brush grade, a substituted magnet, a bearing from a second source, a gear mould re-cut. Any of these can keep every nominal dimension and change the life of the machine. If the shipment carries a revision number and the purchase order names the same one, a silent change becomes a conversation instead of a warranty claim.

Questions a Trader Cannot Answer

Photographs and videos of a building are not evidence, because they can be supplied by anyone with a website. The questions that separate a manufacturer from a reseller are about process, not premises. Can you change the winding for a different voltage, and what does that cost in tooling and lead time? Who owns the tooling if we stop ordering? What is your incoming inspection on magnets and on bearings? What happens to a batch that fails your outgoing test, and can I see the last corrective action you raised?

Each of those requires a factory to answer honestly. A trader can answer the first two by asking someone else and can rarely answer the last two at all. That asymmetry is more reliable than any certificate of factory ownership.

What to Put in the Enquiry

Five items make the first round productive. The output speed and the torque required at that speed, with the tolerance on the speed. The duty in a repeating cycle, stated as running time and rest time rather than as a proportion. The mounting orientation and how the load is attached. The ambient temperature the motor will see rather than the room temperature. And the two or three dimensions whose tolerance actually matters to your assembly, so the supplier knows which ones to hold.

With those, an answer can be measured rather than estimated, and the price that comes back applies to the machine you are building.