Helical geared

Helical geared

MRH Helical geared

The MRH serie helical geared engine reducers are characterized by the position of both coaxial input and output shafts and are made up of two helical geared sets. The main particularity of the helical geared reducers is their great compactness and silence when working.


Structural Features

The MRH serie consists on a coaxial helical spur gear reducer, made of F-1540 case hardened steel (58-60 Rockwell C hardness), with ground- on teeth sides and DIN3962 quality.

The shafts are made of F-1550 chilled steel (56-62HRC).

The carcasses are made of GG-25 grey cast-iron, and are available for all gear reducer sizes. This makes them perform efficiently under stressed conditions, vibrations or any kind of setback that cannot be avoided during assembly.

The oil seals, made of Nitrile Butadiene according to DIN 3760, high quality bearings, an EPOXY-impregnated finish (two components), and a grey-coloured (RAL 7672) SINGLE LAYER ENAMEL finish (two components), provide the most competitive gear reducer on the market.


In order to set up a gear reducer and to make it work efficiently, the following instructions must be taken into account:

  • If has to be fixed onto a flat surface to avoid either vibrations or tautness.
  • If undistribuited loads or continued start-ups are foreseen, it is recommended to insert compensating couplings, connectors, torque limiters.
  • If the gear reducer had to be painted, the detents must be covered to prevent them from drying and losing their seal.
  • The machine work of the fittings set up in the output shafts need an ISO H7 or H6 margin for the hollow shaft.



MRH-71, MRH-80 and MRH-90 gear reducers are constantly lubricated and do not need any kind of maintenance.

For the remaining size, that is, those that are not constantly lubricated, it is advisable to change  for the first time and to wash with cleaning oil after the first 300 working hours. (RENOCLEAN HISTOL DE FUCHS LUBRICANTES S.A.). Levels must be controlled and changes carried out every 4.000 hours. (See lubrication section). Do not mix mineral oil with sinthetic one.



As regards MRH series, sizes MRH-71, MRH-80 and MRH-90, are the only ones that are constantly lubricated, but this comes as standard, with high quality refined oils, non-rusting products, non-wear products, with Fe and Cu protectors and mixed metals with CLP DN 51517-3 quality, level 12 FZG, AP GL-4, US 224, AGMA 250-04; therefore not requiring any kind of maintenance.

The remaining sizes (for transportation purpose) are supplied without oil, and the CUSTOMER must lubricate them, using the appropriate quality of oil, before putting them into operation. In order to do this, the gear reducer is supplied with fillers, level caps and drainage caps.
The exact measure of lubricant is achived when the liquid reaches half of the level cap, the gear reducer being in its running position. This position must be indicated when the order is placed, so as to arrange the fillers correctly.




N.B: It is advisable to use oils such as RENOLIN MP-460 by FUCHS LUBRICANTES, S.A., or MULTIGRADO 80W/90 extreme pressure by CAMPSA, or similar.


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