To tell whether a new motor will fit, comparing overall length alone is not enough; check together where the shaft end will sit relative to the machine, whether the foot holes line up with the base, and whether there is enough space behind the fan cover for cooling air.

DRG-160L-4 15 kW 1500 rpm cast iron frame DRG three-phase motor – checking whether the motor length fits the machine

The shaft end is the reference point

The coupling or pulley is the fixed point between machine and motor. When the motor is longer, the difference usually shows up at the rear, towards the fan cover. So take your measurement backwards from the shaft end: the distance between the shaft end and the obstacle on the machine must be greater than the new motor's overall length.

Length varies even with the same frame number

FrameExample DRG modelOverall length (mm)
132SDRG-132S-4-GG438
132MDRG-132M-4-GG476
160MDRG-160M-4-GG608
160LDRG-160L-4-GG652

The letters S, M and L denote different frame lengths at the same shaft height. This difference also changes the lengthwise distance between the foot holes; hole alignment on the base should be checked separately.

Why does rear clearance matter?

DRG motors are self-ventilated; air is drawn in behind the fan cover and blown along the frame. If the fan cover is pressed against a wall or a sheet-metal plate, cooling weakens and the motor overheats. Failures due to inadequate ventilation are not covered by the warranty.

Order of checks

  1. Measure the distance from the shaft end to the first obstacle behind.
  2. Compare the new model's overall length and rear air gap with this distance.
  3. Match the lengthwise foot hole spacing with your base.
  4. Confirm that the terminal box does not hit parts at the sides.

You can take the dimensions from the DRG technical drawings page; for example, look at the page of the 15 kW 1500 rpm 160L model and compare it with similar frames in the shop.