Engineering Sizing

Determine Belt Length

The first thing needed for any spiral is to find how long the belt has to be.  Use the questions below to help gather the information you will need.

Ok now it is time to use the information you have just collected above.  Put the information into the formula below.

Belt Length Formula:

Example:
This example will be used throughout the Spiral Help steps.
 

Notes on This Example:

• The Collapse factor of 1.45 is a standard mathematical number based on a standard spiral belt running on a standard cage diameter. If you are running on an oversize cage, contact us for the collapse factor.  This 1.45 factor will apply to more than 90% of spirals made.  

Belt width selection is made by determining how the products will be loaded onto the spiral, what type of belt is being used and whether the spiral is an upgo or downgo.  For downgo spirals add 2" to the belt width for hold down rail.

Spiral Loading:

Belt Types:

Hold Down Rails:

Hold down rails are commonly used on descending spirals and require and additional 2 inches of belt width.

Belt Width Details

This section gives you information on all widths and belt lengths per tier, outside frame dimensions, and will assist in the overall size of the spiral unit.
Belt Width Charts

Notes on Example:

In this example, a 38" wide belt could easily be used if you chose a flex or plastic belt.  A rod type belt would be more difficult, assuming a horizontal loading pattern.  A 40" wide rod type belt could be a good choice.  This example assumes and ascending spiral.

Tiers are determined by taking active feet needed and dividing by feet per tier. Feet per tier can be seen on the attached charts showing all belt widths for a given radius. In this example, if we use a 38" wide belt with a standard 2.2 radius type belt, we see there is 63.88 ft per tier.

1450 ft needed = 22.7 tiers needed
63.88 ft per tier

Determine belt radius to be used

2:2 to 1 radius   Most standard used
1:7 to 1 radius
1:5 to 1 radius
1:1 to 1 radius
Other (contact us)

If this is a straight through spiral, round out to 23 tiers
If this is a 90-degree discharge spiral, round to 22.25 tiers
If this is a 180-degree discharge spiral, round to 22.50 tiers

 
The exact final number of tiers can be determined when the final layout of the spiral is made, but typically the layouts change to accommodate the line layout, so this will suffice to go out and get quotes.

 Determine Tier Pitch

3.75" allows for air movement above the product plus belt support structure and belt thickness. For critical sizing and space considerations, contact us for specific manufacturers support design dimensions.

Taking our 12" pizza crust example, use 1" thickness for the product

Based on this, we have a tier pitch requirement of at least 4.75". From a practical side of design, a more typical tier pitch would be 5.5" or 6", especially if you are using wider belts, which require a person’s arm to extend into the spiral for maintenance or clearing out products.