Rotorway Forums

When you back the power off for an approach or practice auto the main belts will oscillate wildly and will slap against the frame tube. Check your frame tubes for black rubber transfer from the belts. Adding a back side idler will keep the belts running true without contacting the frame. Here are some examples.

Check the weld on the bracket in the first picture.
It looks like it is starting to break...

These are hisorical photos from over the years. I’m pretty sure that is dirt showing but no way to verify now years later.

who first started manufacturing the backside idlers?

i havnt seen any instructions for them regarding spacing from the belt, placed with any belt deflection or not or slightly off the belts. or where the best place is biased towards primary drive, secondary drive, or right in the middle of the two. any advice Orv?

Hi Lyle, the first back side idler that I had I fabricated and installed from a piece of spare skid tubing with high speed bearings installed. I got the idea from Steven Lewis who made one out of 1/4" steel bar stock to keep the belts from hitting the frame. With discussion from others in our Sierra Rotorcraft Club that included several engineers, we determined that the best setup was to mount a roller that was placed just off the tight belts so that it would only contact the belts when they began to oscillate. 

Several of our early Rotorway Execs were experiencing significant wear on the back sides of the main belts and leaving a lot of residue and paint worn off of the frame tubes that the belts were contacting. We fabricated any number of designs to hold the idler pulley in place just in line with the clutch pivot bracket that is welded to the frame tube. At this position the idler pulley could be installed clearing both the belt and frame tube. 

Years later Al B. began to manufacture and sell a back side idler and bracket that placed the roller further back toward the secondary and in that position it would continually deflect the belts in toward the center line of the helicopter. This meant that with every engine pulse the idler would transfer some of that force back into the frame tube laterally. When inspecting George T's helicopter I noticed that the frame tube was cracked both fore and aft of the Al B. roller mount points and brought this to the attention of AL B. He denied that his set up would cause any problems. I elected to modify the mounts to move the roller forward to clear both the belts and the frame tube. We had a welder do a repair on the frame so that we could continue George and his son Peter's flight training.