InstroTek FAQ / Rainhart Soil Compactor FAQs

Rainhart Soil Compactor FAQs

Most issues with the Rainhart Soil Compactor stem from improper setup. Before addressing specific problems, please review the Proper Setup section to ensure everything is properly adjusted and aligned.

Installation/General Information

Guide Rod Plates – Keep Them Tight

The guide rod plates should be tight against the rods with no movement. If there’s any play, replace the plates.

To replace: 

  1. Remove both bolts.
  2. Slip the plate off the bottom.
  3. Reinstall by reversing the steps.

When reinstalled, the distance between the plate and the guide rod disc should be 0.016”. If not, the compactor may need recalibration.

Upper Guide Bushing – Stay Within Spec

The upper guide bushing wears over time. Measure the inside diameter:

  • Good: Less than 0.87"
  • Replace: 0.87" or larger
Tamping Head Rotation – Check the Drop

If the tamping head doesn’t drop properly—or stutters, or hits a guide rod—the rotation is likely off.

To correct:

  • Adjust the angle of the spacer rod at the back of the grabber.
  • Measure from the frame to the outside of the engager handle block: it should be 4-¼”.
  • At this distance, you should get 10–11 blows per rotation.
Adjust Grabber Height – The ½” Gap

There must be a ½” gap between the grabber body and the releaser body. This is adjusted using the grabber cable.

  • The u-bolt closest to the flywheel pulley = fine adjustment.
  • The u-bolt further away = coarse adjustment.

How to Adjust Grabber Height:

  1. Disengage the grabber by flipping the tripper arm down.
  2. Rotate the flywheel handle to bring the grabber to its highest point.
  3. Measure the gap between the grabber and releaser.
  • If not ½”, adjust the fine u-bolt up or down.
  • Use a gauge block for accuracy.
  1. Once correct, tighten the fine adjustment bolt and recheck.
Guide Disc – Watch for Wear

The guide disc’s outer curve wears flat over time. The flat area should never exceed 5/32”.

Grabber Teeth – Check for Wear

The brass teeth inside the grabber slowly wear down.

To inspect:

  1. Without resting on anything, engage the grabber by flipping the tripper arm up.
  2. Look from the side to check the inner angle bar.
Counter Setup – Sensor and Tape Position

The counter relies on correct spacing between the sensor and reflective tape.

Key checks:

  • Use only the paired reflective tape (other types may not register).
  • Sensor should be mounted on the bracket as shown.
  • Keep tape clean and positioned correctly.

Errors/Common Questions

Why is the counter skipping or Not Counting?
  • If using an SCA, refer to the SCA troubleshooting guide.
  • Clean and realign reflective tape.
  • Verify sensor-to-tape distance.
  • Confirm sensor is plugged in and undamaged.
  • Check counter power.
Why is the Counter Not Powering On?
  • Check wall power and ensure motor is plugged in.
  • Confirm blow count is set to desired number.
  • Inspect the fuse on the back:
  • Twist the fuse cap to pop it out.
  • Stretch spring inside if over-compressed, then reinsert.
Why is the Tripper Arm Breaking Repeatedly?
  • Verify grabber height—too high may smash the tripper arm.
  • Check rotation angle—tripper arm may be striking a guide rod. (See Proper Setup section.)
Why is the Grabber Not Grabbing?
  • Inspect grabber teeth for wear.
  • Verify engager height is correct.
  • Clean shaft with denatured alcohol. Do not lubricate.
Why is the Grabber Stuttering or Not Releasing?

This is usually a setup issue. Excess vibration can cause misalignment and prevent proper grabbing.

Recheck all setup steps above.