Double Helical Gears

Types

Characteristics

Advantages

Double Helical Gears: Product Code: ADHG001 Product Specifications: Materials used in making helical gears: MS or Alloy Steel, Carbon Steel Standards: As per ASTM, BS, IS, AISI, SAE Module: Upto 40 Module Type: With Gap Manufacturing Capacity: 200mm to 8,500mm Outside Diameter Note: Custom orders are also taken by us. » Send Enquiry

Double Helical Gear is of cylindrical form. It has two sections of teeth, right hand and the other left hand. They operate by engaging themselves simultaneously with the teeth of an identically designed mating gear.
In these Helical Gear the thrust loading is effectively eliminated by usage of two pairs of gears. The tooth angles are opposite to each other. This results in the cancellation of side thrust of one Gear by the other one. These opposite gears are made in a manner for having a space between the two opposing sets of teeth.

Types of Double Helical Gears
These helical gears are generally found to be of two kinds. One type is the one that has a gap between the helices. In the other one, opposite hand helices get cut without giving a gap. This is called the Herringbone Gears.

Both the type of helical gears uses a perfect combination of right and left hand helices. This makes the thrust load fully balanced. This balance is a conclusive advantage for selection of supporting bearings. Another advantage is lower loads on the gear reducer housing.

Characteristics of Double Helical Gears
The following are some of the prominent characteristics of a these helical gear:

• Double helical gears incorporates all the plus points of single-helical gears along with cancelling the thrust loads that are internally-generated. This can be utilised for using smaller thrust bearings. (This can be critical in reducing power losses in very high speed units). In Double helical gears Up to35 degrees of Helix angles is normal.
  
  
• In these helical gear there is need for one member to be free to float axially. This is important for sharing of tooth loads between the two helices. This also balances effectively thrust loads that are internally generated. However, it is quite likely that external thrust loads found on the floating shaft tilts the balance by unloading one helix but overloading the other. In absence of proper alignment or lubrication all the shaft couplings can generate huge thrust loads. So to reduce such external thrust loads, Elastomeric and steel-diaphragm couplings that has high axial stiffness may be applied.
  
  
• As it happens that two helices do not match perfectly. The floating member show a tendency to continually shift axially while responding to the thrust loads that are not equal. Now this type of shifting is the cause of axial vibration if there are too much error in the tooth geometry.
  
  
• Double helical gears encompass larger F/d ratios than say a spur or even a single helical gear. This is because of the fact that many of the alignment errors are compensated by the floating member shifting axially.
  
  

Key Advantage of Double Helical Gears
These Helical Gear can offer the same type of advantage and operating smoothness as that of a single helical gear. Further, it offers the benefit of a greater strength in contact of the teeth and elimination of side ways force. Double helical gears provides an efficient and smooth transfer of torque and motion even at considerably high rotational velocities. As there is absence of axial thrust, helix angles are maintained around 30 degree, thereby offering the advantage of a large face overlap. Double helical gears give an efficient transfer of torque and smooth motion at very high rotational velocities.