Backstop Selection

Information courtesy:

How to select Falk NRT backstops

1. Determine Drive Arrangements from Drive Arrangement link

Refer arrangements in Figures 4 & 5 (Drive Arrangements) to the Factory for selection.

2. Determine System Torque

• Fig. 2 -Tandem motor, single backstop arrangements.

• Fig. 3 -Tandem motor, tandem backstop arrangements.

Combine the horsepower from both motors.

System Torque = Power/(2*PI*RPS)

Power - Motor(s) Nameplate power
BP - Brake power (Calculated load)
LP* - lift power (Calculated Power to lift the load Vertically)
RPS - Revs per second
*LP can be calculated as follows:

(Tons Per Hour (TPH) x Lift in Meters) / 3.6

3. Determine Required Backstop Torque

Required* Backstop = System Torque * (Motor Stall Torque%/150%)

*For Figure 3 - Tandem motor, tandem backstop arrangements Select each backstop to hold 60% of the total Required Backstop Torque.

1. Select backstop with a torque rating equal to or greater than the required torque rating determined above.

2. Check the maximum bore. If a larger bore is required, select the next larger size or turn the headshaft down'.

3. Check the maximum overrunning speed.

4. Check backstop reaction force at torque arm stirrup.

5. Backstop and torque arm dimensions are listed following allow space for installation.

6. Only use heat treated keys furnished.

If the backstop is mounted on the double ended extension of the reducer shaft, check shaft stresses and use dual path (safety lock) couplings or a minimum 2.0 service factor on the combined power for the coupling on the NRT side.
Indexing requirements must be referred to the Factory for selection.

Engineered Selection Method For Inclined Conveyors -
It is possible to fine tune the selection and possibly consider the selection of a smaller size backstop, if detailed loading and conveyor profile information is known.

The following data is necessary:

• Power to lift the load (vertical)

• Power to move empty belt (friction)

• Power to move loaded belt horizontally (friction)

One can calculate these values if the following data is provided :

• Conveyor length (L) -m

• Belt speed - m/sec

• Tons per hour - tph

• Total lift (H) - m

• Belt width -mm

• Material weight - kg/m³

Selection Examples
The seection examples below show the benefits gained from obtaining the required information to select by brake or lift torque vs motor torque
Shallow Slope Conveyor	Steep Slope Conveyor
200 Motor HP	200 Motor HP
155 Brake HP	180 Brake HP
68 Lift HP	150 Lift HP
200% Stall	200% Stall
68 RPM	68 RPM
4(15/16) Dia.	4(15/16) Dia.
Motor HP and Stall % Known
((200MPH * 5250)/68RPM) * 200%/150% =	((200MPH * 5250)/68RPM) * 200%/150% =
20,588 lb-ft Motor Torque	20,588 lb-ft Motor Torque
1095 NRT	1095 NRT
Brake HP Known
((155BHP * 5250)/68RPM) * (200%/150%) =	((180BHP * 5250)/68RPM) * (200%/150%) =
15,956 lb-ft Brake Torque	18,529 lb-ft Brake Torque
1085 NRT	1095 NRT
Lift HP Known
((68LHP * 5250)/68RPM) * (200%/150%) =	((150LHP * 5250)/68RPM) * (200%/150%) =
7,000 lb-ft Lift Torque	15,441 lb-ft Lift Torque
1075 NRT - Rating Selection 1085 NRT - Bore Selection	1085 NRT