Figuring Auger RPM

A very common problem. How do I figure my auger's RPM?
Use these formulas to figure auger RPM.

For straight pulley reduction:
Drive pulley x motor RPM = SUM ÷ driven pulley diameter = auger RPM

For auger with a reduction gearbox:
Drive pulley x motor RPM = SUM ÷ driven pulley diameter = SUM ÷ gearbox reduction ratio = auger RPM

To use the auger RPM you've figured to figure capacity, click here.

Thickened Edge Flighting Review

I recently took a look at some testing done by an accredited agency in Canada regarding the durability of thickened edge flighting versus traditional helicoid style flighting. Following is an article I wrote in regards to that.

The Myth of Thickened Edge Flighting

"Up to 50% thicker", "longer life augers", "improved wear resistance", are the features the manufacturers of thickened edge flighting tout as advantages over traditional helicoid style flighting. However, are these features actually fact and advantage, or is thickened edge flighting simply marketing hype?

First one has to understand what traditional helicoid ribbon style flighting is. Traditional helicoid style flighting is flighting rolled from a rectangular piece of steel to create the flighting, or "auger part" of the auger in a long, unbroken, ribbon. To produce this flighting, the traditional method of production rolls flighting that is thicker at the base, or core, than it is at the outer edge. So, if you say, "10 gauge flighting," generally speaking, you are talking about the flighting thickness at the base, where it is welded to the center flighting pipe. This is how flighting has been produced for the grain handling industry for many years.

Recently, thickened edge flighting, also known as Super-Edge or Dura-Edge amongst other names, has been introduced and promoted as an improvement on this process. Thickened edge flighting is helicoid style flighting rolled in such a manner as to leave a thicker strip of material at the outer edge of the flighting. The intended purpose of this thicker strip along the edge is to give you more material where flighting wear is normally most apparent. Sounds like a good idea right? Add more material to the edge for more wear? Unfortunately, it seems, this is not necessarily an advantage.

A study conducted by an independent, accredited, agricultural testing agency compared traditional helicoid style flighting and thickened edge helicoid style flighting. The findings were somewhat surprising.

A metallurgical report on the steel of both respective types of flighting was done. Breaking down the numbers into a manageable format that the average person can understand, the traditional helicoid style flighting tested as using a harder base material than the thickened edge flighting's material. Additionally, the report refers to differences in the "work hardening" at the edge of both flightings. The thickened edge flighting product showed less work hardening at the outer edge of the flighting than the traditional flighting. Specifically, the thickened edge tested at a softer 91-91, versus the traditional flighting at 95-95. Presumably, to accomodate the manufacturing process of leaving more material at the edge of the flighting, the thickened edge flighting has to be rolled from a softer grade of steel, and because it is "worked less" at the edge to leave the remaining thickened band, it is less dense at that point.

A mechanical test to identify differences in the durability of the traditional and thickened edge flighting was done by running identical flightings, with the exception of the edge type, in aggregate for 85 hrs. Visually, after running for the same amount of time, it was very difficult to tell the difference between the two flightings. Beyond the visual, weighing the flightings showed that the thickened edge flighting actually lost material 10% faster than the traditional flighting when compared on a weight basis.

So, what does all this testing mean? Essentially, this is a case of perception, marketing perception. Considering the information mentioned above, thickened edge flighting offers no real, definitive advantage over traditional helicoid style flighting. Realistically, one could point to subtle points of superior wear characteristics for the traditional flighting. So, if you are paying more for, and expecting more life out of your thickened edge flighting, you may be disappointed.

Auger Flight Rotation and Material Flow

The above diagrams are a simple means of determining screw rotation. When the material flow is in the direction away from the end being viewed, a RIGHT hand screw will turn counter clockwise and a LEFT hand screw will turn clockwise rotation as shown by the arrows.

How to Identify Right Hand or Left Hand Flighting

A picture is worth a thousand words. Below is a picture of how to tell if your auger has right hand, or left hand flighting.

A conveyor screw is either right hand or left hand depending on the form of the helix. The hand of the screw is easily determined by looking at the end of the screw.

The screw pictured to the left has the flight helix wrapped around the pipe in a counter-clockwise direction, or to your left. Same as left hand threads on a bolt. This is arbitrarily termed a LEFT hand screw.

The screw pictured to the right has the flight helix wrapped around the pipe in a clockwise direction, or to your right. Same as right hand threads on a bolt. This is termed RIGHT hand screw.

A conveyor screw viewed from either end will show the same configuration. If the end of the conveyor screw is not readily visible, then by merely imagining that the flighting has been cut, with the cut end exposed, the hand of the screw may be easily determined.

Useful Grain Handling Sites

-Purdue University Post-Harvest Grain Quality & Stored Product Protection Program.
-Mycotoxins in Cereal Grains
-Grain Storage Management (Univ. of Neb. Lincoln)
-Iowa Grain Quality Initiative (Iowa State University)
-Univ. of Minnesota Post-Harvest Handling of Crops
-Oklahoma State Univ. Stored Products Research
-North Dakota State Univ. Grain Drying, Handling and Storage
-USDA ARS Grain Marketing and Production Research Center
-Kansas State University Grain Science Industry Extension Program
-Multistate Project NC-213 (Management of Grain Quality and Security)

Auger Horsepower and Capacity Reduction

Horsepower Interpolation

Example by Length:

Given: a 34’ horizontal auger, 8” diameter running at 430 rpm, (15% corn) 2,160 bph.

Per the chart, 30’ takes 2.8 hp in 15% corn.

34 / 30 = 1.13

1.13 x 2.8 = 3.16 hp required

Example by Capacity:

Given: The above auger, 8” x 34’ at 430 rpm but instead of 2,160 bph, we need 2,500 bph.

2,500 / 2,160 = 1.16

1.16 x 3.16 = 3.67 hp required

Capacity Reduction Factor

	CAPACITY REDUCTION FACTOR
ANGLE OF INCLINE	CORN & WHEAT	SOYBEANS & SUNFLOWERS
0	1.0	1.0
5	0.98	0.97
10	0.96	0.94
15	0.94	0.90
20	0.92	0.87
25	0.89	0.84
30	0.87	0.80
35	0.85	0.77
40	0.83	0.74
45	0.80	0.70
50	0.77	0.65
55	0.74	0.63
60	0.70	0.60
65	0.67	0.57
70	0.64	0.54
75	0.60	0.50
80	0.57	0.47
85	0.54	0.44
90	0.50	0.40

The horizontal capacity of the equivalent diameter and length of auger can be multiplied by this number to determine the incline capacity at the same horsepower and rpm.

Auger Capacity Per 100 Revolutions

The capacities listed below are based on clean, dry corn at approximately 90% load on a horizontal operation. Grain conditions, grain type, and loading methods will change capacities listed below. (bph = bushels per hour)

Auger Diameter	Capacity Per 100 rpm (90% load)
4”	60 bph
6”	240 bph
8”	480 bph
10”	1200 bph
12”	2000 bph

Grain Handling Knowledge

It is difficult to find a place where one can look up all the math, and theory, and layout ideas for grain handling systems. So, in response, I am beginning this blog. I will post as much "free domain" info as possible on this site. Check back often, I hope to update frequently. Also, I'd love to hear from those of you out there that have new ideas or experiences that apply to this area of need in the agricultural industry.

Thanks for visiting! I hope you find this site useful.