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Old Oct 25, 2010, 05:30 AM
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Letchworth, Great Britain (UK)
Joined Jul 2004
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When do bearings wear out?

I've been flying my T-Rex 500 for 18 months or so, and have replaced the main shaft, feathering shaft, boom, main gears maybe 3 or 4 times due to crashes. But I've never replaced any bearings because I've had no suspicion that any bearing is going bad.

A couple of times now heli buddies at the flying field have suggested it's about time I changed my bearings. I know that putting new bearings in can't be a bad thing, but I don't want to do it unless it's absolutely necessary. They all feel smooth at the moment, and I don't feel any looseness in any of them.

The heli has had about 200 8-minute or 7-minute flights in its 18 months. What's the concensus about replacing bearings, please? Wait until they feel bad, or get noisy, or replace them after xx hours as a matter of course?
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Old Oct 25, 2010, 06:02 AM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
22,300 Posts
Regular bearings I would replace when you can feel or hear them going bad. How ever with my brother's heli or one of them he had several crashes and then after replacing everything he stil lhad couple more crashes that were attributed to the oneway bearing. The LHS guys of fly heli said anytime the you get a crash where the rotor head will stike and the force is strong enough to stip the main gear and stuff like that then the oneway bearging should be inspected and or replace and of course the last two unexplained crashes were because of this.
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Old Oct 25, 2010, 08:19 AM
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United States, TX, Round Rock
Joined Dec 2004
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Quote:
Originally Posted by freechip View Post
. . .
The LHS guys of fly heli said anytime the you get a crash where the rotor head will stike and the force is strong enough to stip the main gear and stuff like that then the oneway bearging should be inspected and or replace and of course the last two unexplained crashes were because of this.
The job of the LHS guys is to sell parts.

How can a one-way bearing cause a crash?

Abenn, I'm still new to helis but I'd say "Don't fix it if it ain'n broke!" I'd replace bearings when they become noisy or feel sloppy.
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Old Oct 25, 2010, 09:29 AM
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Canada, ON, Rockland
Joined Aug 2008
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Originally Posted by ivanc View Post
How can a one-way bearing cause a crash?.
Simple it has enough bite for proper start up and regular flight but then when more power/ head speed is added for 3D flight and at the first demanding move the oneway bearing lets go of it hold on the shaft you are now left with a heli that no longer as motor power since the motor is free spinning and unless you have been practicing auto-rotation landings then its going to land are and or crash.

I know this cause the last 2 for my brother were because of this.
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Old Oct 25, 2010, 01:31 PM
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Letchworth, Great Britain (UK)
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Thanks. The consensus so far seems to be don't change them until they're broke/noisy/sloppy, which is generally my philosophy anyway.

As for the one-way bearing, experience of crashing my T-Rex thus far is that the main gear is made of such soft plastic (nylon?) that it's teeth strip long before it can do any damage. I've always assumed I'd be able to detect when the one-way starts slipping, by holding the gear and trying to rotate the head. Or are we saying it can let go suddenly (other than by crash damage, that is)?
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Old Oct 25, 2010, 02:42 PM
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Canada, ON, Rockland
Joined Aug 2008
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We also taught that by grabing the head and preventing the gear from spinning we could get it to slip BUT it prove to be harder then we taught OR the Scorpion motor used in my brother's T-Rex 700E as alot more power then what we can imagine. What was happening was the rotor head would losing speed but the motor was still spinning full speed. Depending how quick you are to react or how good you`re auto rotation landings are its either going to be ok or not and for both time it happened it ended up costing some money from the LG breaking and then blades striking the ground or just other damages.

It think its good pratice to atleast inspect the oneway bearing one in awhile.
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