What is the difference between direct drive and belt drive?

Where the power crosses the machine

Every floor machine has to get rotation from a motor to a pad, and there are only two ways to do it. Directly — the motor sits over the pad and drives it through a gear reduction on the same axis — or across a gap, with a belt running over pulleys to a spindle somewhere else on the chassis. Everything else about the two arrangements follows from that one choice.

POLIVAC's own catalogue splits cleanly along the line. The single-disc machines — PV25, C25, C27, A23 and the Sandivac sanders — are gear drive: an offset motor over a sealed, oil-filled Polidrive gearbox, or on the Gen2 machines a triple-planetary helical gear drive. The burnishers are the opposite: the SL1600, SL2000 and the whole LPG range list their drive system as belt-driven, and so do the low-profile Shark and Gas Shark.

Why each ends up where it does

Gear drive transmits torque without slip, which is what a low-speed machine needs when a pad loads up in stripper or a sanding disc catches. It also removes a consumable and a tensioning adjustment from the machine entirely. The cost is that the layout is fixed: the pad has to sit under the motor.

Belt drive buys freedom of layout and a deliberate weak link. A burnisher spinning a pad at 1,500–2,500 RPM off a petrol or LPG engine wants something that can slip rather than transmit a shock straight into the crankshaft, and the Gas Shark pairs its belt with an electronic clutch for exactly that reason. It is also how the Shark gets its 14.5 cm low profile — the motor can sit back from the brush instead of on top of it. The trade is a belt to check, tension and eventually replace, which POLIVAC treats as a feature: the GAZ 16 Gen II lists belt drive for easy access and low maintenance, and the Gas 38 lists easy access to belts and pulleys.

When it matters

This is worth asking about when you are comparing two machines of the same size and one is noticeably lighter or lower. A low profile almost always means a belt somewhere, and that is a fair trade if the job is scrubbing under gondolas and checkouts. On a general-purpose polisher or scrubber that will see stripping work, gear drive through a sealed gearbox is the arrangement that does not care.

It also changes the parts conversation over a machine life. A belt is a cheap, stocked consumable and a ten-minute job; a gearbox is neither, which is why the sealed ones carry their own warranty. Neither is better in the abstract — a belt on a burnisher is doing a job, not saving a manufacturer money.

One caution on terminology: "direct drive" is a trade term, not a POLIVAC one. POLIVAC describes its own machines as gear-driven through the Polidrive gearbox rather than as direct drive, so when a competitor advertises "direct drive" it is worth asking what the reduction actually is before treating the two claims as comparable.