Vance's Comments Pertinent to ME
Vance's Comments Pertinent to ME
Thanks Vance,
When you speak of your motorcycle exploits...I LISTEN! You know what you are talking about because you worked very closely with the experts in these fields and proved out what they said with actual experience.
The Mini-500 I am building uses this same type Cog-Belt as the one above. I had one fail on my Mini-500 in 1997 because at the time, deliberate shaft mis-alignment was the method used to make the belt ride in the center of the pulleys. Tension was set by adjusting the idler once, and using a spring scale to measure deflection and tightening it there. It didn't throw off teeth like the one in the picture. It actually shredded perpendicular to the teeth like it had been cut with a slitter. When I landed normally after I heard the machine-gun sounds back there, There was less than 1/2" of the belt width driving the rotor. The Revolution helicopter factory had me elongate one of the idler pulley axle holes and experiment with tilting that pulley to track the belt. I had no problems in the next 50 hours until I sold it.
Now I have the newer "Bravo" style idler setup which involves the engine crank and MRGB input pinion being in perfect alignment. Then the new style idler is spring-loaded with a dampener to keep belt tension constant at manufacturer spec., under all operating conditions and as parts wear or warm up.
Tracking of the belt on the cogs is accomplished by a micro-precision axle adjuster that slightly tilts the idler pulley.
Seems good to me, but I have never flown the new setup. I don't remember anyone having any problems with it after the re-design.
Now my NEW 15 year old kit came with a "WOOD'S" brand belt (PRINTED ON THE BELT) that was made somewhere in Europe. (Can't remember where) My 1997 Mini-500 came from the factory with a Gates brand one. I know that rubber degrades over time so even though my new belt had been in a vacuum pack for 15 years, I wanted a new one.
My first contact was with an engineer at Gates. I sent drawings of the drive system to him and he was very helpful for the first 30 minutes ...UNTIL HE REALIZED IT WAS AN AIRCRAFT APPLICATION. Then "POWWWW!" He slammed the door in my face.
My second contact was with an engineer at "WOOD'S." I was very careful to NOT provide any info to her that would give a hint of aviation use.
She ran the calculations and roughly determined that the drive system could go to 2000 hours of constant 6500 RPM operation while transferring a constant 36 horsepower, with a safety factor of two.
Ouch! We all know the Mini uses 70 to 80 HP to hover and about 50 HP to cruise.
The engineer provided me the correct part number for the most current replacement belt that matched my tooth profile and identified my local distributor.
I ordered it through Applied Industrial Technologies, DIRECTLY FROM WOOD'S. $83.00 later, I had the new. modern belt in my hands...
GUESS WHAT? IT WAS A GATES BRAND POWER-GRIP GT BELT! The engineer at Wood's said "Oh...we don't MAKE them. The Gates Power-Grip GT is sold under our product name _ _ _ _ _ _ _ _." Can't remember the name.