# Topic: Re: Is there a formula for outer and inner ribbon pitch for a ribbon mixer?

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Technical books are not going to give you mixer geometry and design in most cases. Some articles may give information about the specifics of laboratory tests, but that information may not be helpful for production equipment.

The following information is general, but can be used for your specific situation:

Housing dimensions: Diameter 2,200 mm Height 2,300 mm Length 4,000 mm

Typical relative dimensions: Diameter 100 units Height 120 units Length 200 units
Typical rotating ribbon: Diameter 95% housing diameter = 95 units Length 2 x ribbon diameter = 190 units
Gap = 2.5% of housing diameter 2.5 units
Ribbons - Two outer ribbons (double flight helix) at 180 degrees from each other for balanced loads
Ribbon width - 5% of ribbon or housing diameter = 5 units
Inner Ribbon - 10% of ribbon or housing diameter = 10 units - center at 0.5 x diameter of ribbon = 50 units
Outer ribbons - Pitch = Diameter = 100 units - pushes toward discharge
Two double flight ribbons pushing toward center for center discharge
Inner ribbons - pushing in direction opposite to outer ribbons.

For specific housing:
Ribbon diameter – 2,090 mm Gap - 55 mm
Outer and inner ribbon pitch – 1,900 mm
Outer ribbon width - 104 mm Inner ribbon width - 209 mm
Precise dimensions are not critical as long as they are good approximations
The answers by this expert are based on the best available interpretation of the information provided. The consequences of the application of this information are the responsibility of the user. If clarification is needed, please submit a further question.