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After about 6 gallons my main gear stripped in flight. The noise it made was incredible. I thought a bearing in the engine had self destructed initally. Anyway, I put another main gear in, and the same happened a gallon later. I know this happened to Duncan Osbourne at a competition. I believe he put it down to the bearings in the pinion bearing block moving. Assurance RC (the US align Distributor) have advised to modify the backlash between the drive pinion and the main gear. There is a chap producing a metal bearing block which he claims will fix the problem. And now I hear align is producing a beefier main gear......all in all it a bit confusing ! Does anyone here have any advice? All I know is I need to fix this problem and stop it happening again, and again!
http://www.helifreak.com/showthread.php?t=94692
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Also, I received an email from Kyna at Assurance today stating this about the main gear stripping issue:
Quote:
We have had reports of main gears stripping on the T-Rex 700 and have noticed on some models that the gear mesh between the main and pinion gear is too loose. The easiest way to resolve this is to move the pinion gear (clutch bearing block) closer to the main gear. First remove the clutch bearing block and remove the plastic ears from each side with a sharp hobby knife. Second drill the 4 holes in the frames where the clutch bearing block bolts go through to a diameter of 5.0-5.5 mm. Third re-install the clutch bearing block and adjust the mesh so that the clutch bell has only the smallest amount backlash.
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It looks like it's the plastic in the pinion gear bearing block compressing over time and obvoiusly the more power you have the quicker this is likely to show up if at all.
The plastic compresses and allows a little sideways movement between the bearing and block so that the pinion can just move a little out of alignment.
Note we are talking about sideways movement developing here not front to back, the torque reaction would cause the pinion to want to push away from the main gear!
Wayne's solution was to skim the faces of the bearing block so they clamp the bearings a little tighter, he also shortened the two hex spacers which pass though this just a fraction so again everything would clamp up tighter.
As I said Duncan flew the model a lot over the weekend and it seems to be holding up fine, to be fair Duncan had well over 150 flights on this model (and you know they wouldn't have been gentle flights!) before the gear went so it's not like the model is under engineered.
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http://www.helifreak.com/showthread.php?t=94692
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Also, I received an email from Kyna at Assurance today stating this about the main gear stripping issue:
Quote:
We have had reports of main gears stripping on the T-Rex 700 and have noticed on some models that the gear mesh between the main and pinion gear is too loose. The easiest way to resolve this is to move the pinion gear (clutch bearing block) closer to the main gear. First remove the clutch bearing block and remove the plastic ears from each side with a sharp hobby knife. Second drill the 4 holes in the frames where the clutch bearing block bolts go through to a diameter of 5.0-5.5 mm. Third re-install the clutch bearing block and adjust the mesh so that the clutch bell has only the smallest amount backlash.
------------------------------------------------------------------------
It looks like it's the plastic in the pinion gear bearing block compressing over time and obvoiusly the more power you have the quicker this is likely to show up if at all.
The plastic compresses and allows a little sideways movement between the bearing and block so that the pinion can just move a little out of alignment.
Note we are talking about sideways movement developing here not front to back, the torque reaction would cause the pinion to want to push away from the main gear!
Wayne's solution was to skim the faces of the bearing block so they clamp the bearings a little tighter, he also shortened the two hex spacers which pass though this just a fraction so again everything would clamp up tighter.
As I said Duncan flew the model a lot over the weekend and it seems to be holding up fine, to be fair Duncan had well over 150 flights on this model (and you know they wouldn't have been gentle flights!) before the gear went so it's not like the model is under engineered.
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