cudaboy_71
Elite Veteran
Location: sacramento, ca, u.s.
| i was just digging through some old (really old) posts and came across this one by Augusto.
http://www.runryder.com/helicopter/t55473p1/
take a minute to let all that sink in, then read on:
i'm no engineer, but what he says about the basic function of a sprague clutch/oneway bearing makes sense. The only difference between the issue with the Freya bearings and the issue with the 600N bearings is one fundamental design of the autorotation case, changing the problem from one of bearing slippage in the Freya to lockup in the 600. But, in both issues it seems that there's a failure of the sprague system to engage as designed. In the Freya instance, failure of the oneway to self-align during engagement caused microfratures in the auto case, causing the auto case to expand and prohibit the clutch from engaging. in the instance of the 600N, there is an upper and lower bearing (on the main shaft) preventing the sleeve from self-aligning; and, because of the pressfit nature of the oneway bearing in the case, it cannot self-align, thereby creating a failure of the roller bearing retainers in the clutch itself.
of course, in Augusto's post, he provides a remedy in greasing the outside of the oneway bearing before going into the autorotation case. But, this is not a solution for the 600 because of the press fitting.
so, it would seem that the 600N hubs have a bit of a design flaw --at least according to the concepts outlined in Augusto's post. And, unless i'm just completely missing the point (which i very well could be) i'm having trouble coming up with an easy fix. the way i read it, one of the two components of a sprague bearing, either the roller casing or the shaft/sleeve that fits into it, need some lateral self-adjusting room to properly engage. if neither are allowed to self-align, undue forces are exerted repeatedly on a disproportionatly small area of the oneway--ultimately causing failure.
like i said, i'm no engineer. so, i still have one lingering question: why is this not an issue in the 600E with such a similar if not identical design? i have some theories already...but, still half baked. as i continue to think about this throughout the day, i'll probably start shooting holes in my own argument. but, maybe this can start some intelligent conversation about the actual problem, a fix, a mod, a workaround or outright solution. or perhaps understanding the problem can help suss out the subtle setup differences between the people having lockup issues and those not (main gear to pinion mesh leaps to mind off hand--as this could be the few thousanths of an inch self-aligning freedom the main gear needs to self align to the oneway?????)
if it ain't broke…break it. |
from Esprit and installed it yesterday. I was surprised to find the sleeve appears to be identical to the stock part as both have a 0.473" OD.
. I replaced them after every lockup. I'm getting a Boca replacement.
