Rundquist Propeller Tools, Inc.

Operation of the 36" Gauge - Checking propeller pitch, rake, tracking and diameter

 

Determine the pitch of the propeller

1. Mount the propeller on the gauge shaft between the cones with the pushing face of the propeller up.  Slide the two set collars provided on next, one will be used to hold the prop down tight, the other will be used if need to hold the indicator at a desired height. 

2. Set the pitch gauge to the radius that you wish to check by sliding the gauge assembly along the horizontal shaft.  Each hole in the shaft corresponds to a radius on the direct reading faceplate.  Radius "A" is closest to the faceplate.
   
   (click on a photo for a larger view)

3. Set the needle on the faceplate of the gauge to the correct scale that corresponds to the radius being checked.
   
   

4. Touch the gauge to the trailing edge of the propeller and slowly check the pitch down the blade to the leading edge. The needle will show exactly what pitch the propeller has and indicate right or left hand rotation. ALWAYS check all three blades and mark the pitch and rotation directly on the blade using a marker. Example: If the propeller reads 18" pitch, right hand, mark the blade 18R.
   
   

 

Check the Rake of the propeller to determine the correct rake angle.

1. To find the rake angle of a propeller, use the rake gauge. Slide the rake assembly into the back of the 36''IND., Using the machine handle lock on the flat of the 1/2'' shaft, this locks the IND. on center of the shaft. Slide either the 6'' or 12'' rake blade into the rake foot. Set the blade on the propeller. Slide the blade out so that it stays about 1" from the hub.  Set the gauge against the propeller and look for the straight line. At first you may find it easier to use a 6" scale to find the straight line, draw a pencil line along the 6" scale to find the straight line, draw a pencil line along the 6" scale, then check the rake at this point. ALWAYS check all blades.
   
   

2. The angle of the blade can be read on the faceplate of the rake gauge. This is the rake of the propeller. EX: Propeller reads 16" AFT rake.
   
   

3. Mark the rake on the propeller behind the pitch and rotation. Example: 18R16 - This shows the pitch block to use on the propeller.
   The example above is how each pitch block is marked. Pitch, rotation and rake. On most standard propeller designs the straight line cuts through the shaft center.

4. To check parabolic rake - the straight line referred to will be found to miss the center of the shaft from 1/4 to 10-1/2 inches. A propeller of this type can be thought of as consisting of straight sections arranged tangent to a short radius from the shaft center. This propeller, if cut directly through the center will show a parabolic curved section instead of the conventional straight section. This is intended to produce a better stress pattern in operation and also to add to the gripping quality of the propeller. The Federal Equipoise propeller is designed this way. To check the rake on this type of propeller, loosen the machine handle that is locked against the 1/2'' shaft this allows you to set the rake blade off center to check the propeller. Once you set the rake blade to the straight line, tighten the machine handle. Check all blades to determine the rake.  Gauge and mark all propellers to be worked. This eliminates the possibility of using the wrong pitch block for the repair.

         Check the tracking of the propeller

1. Lock the second set collar on the shaft so when the indicator is placed on the shaft it will spin freely without hitting the propeller. With the rake Ind.  and shaft removed insert one of the provided lasers in the top of the hole pointing down.
   
   

2. Attach the second laser assemble to the body of the indicator.
   
   
   

3. Position the laser on the body of the indicator to point to 0 on the scale that is on the base. Slide the indicator in so that the second laser is pointing to the trailing edge of the propeller, you will have to turn the propeller until the laser shines on the trailing edge. Once this is set up, you can then begin to rotate the indicator. On a three bladed propeller each blade should be a 120 degrees apart.  Ideally, when the laser on the body reaches 120 degrees the second laser should be touching the trailing edge of the propeller.
   
   

         Checking diameter of the propeller

1. With the rake assembly removed from the back of the indicator, insert the laser into the top of the hole.
   
   

2. Slide the indicator out until the laser just makes contact with the edge of the propeller.
   
   

3. With this set, you can then directly read the propeller radius from the scale. The measurement is read from the edge of the block.  Multiply the radius by 2 for propeller diameter.