Rotor Strikes and Rotor Bearings - do not fly after a rotor strike.

[MadMuz]

My thoughts on the tapered roller bearing, is that the tapered roller needs to be set correctly.... we all know what happens to front wheel bearings on a RWD car when the bearings are a bit worn or dry.... you can jack the car up and grab the wheel and feel the play in the bearing.... so you should remove the pin, undo the nut, inspect the cone, wash the bearings, repack the grease and reassemble.... then comes the tightening..... how tight? Ok, you nip it up lightly, spin the hub, back off, nip up again.... spin the hub.... then you go to pin the castle nut..... but it is half way between? So, you should get a thicker washer so you can pin it right, but most just tighten a bit more to get the pin in..... works on cars So you do this on a gyro, imagine you have a gyro with the typical tapered roller bearing.... the only thing stopping the nut undoing (unless you use left hand thread) is the split pin and washer with the tang into the stub slot.... I am sure it would work, if the bearing is a bit tight, there might be a bit much drag to begin with, but shouldn"t be a problem.... should be good.Compare that to buying a $36 quality brand washing machine bearing and putting it in (correct way up if slot type) and torqueing the main bolt/nut to spec.

[gyroo]

I agree with all that you"ve written Muz.My original post in support of the possibility of using tapered roller bearings had one extremely important qualification - that "obviously it would take much more care to seat and fit a set of taper roller bearings"I"ve actually experimented with this on the workshop bench and came to the conclusion that the only way you would be able to reliably use an opposing pair of taper roller bearings is to - with extreme care and precision - machine a spacer to jam between the inner races, so that as you torque up the "Jesus Nut" to the proper rating, you also happen to be setting the right "pre-load" that the bearing manufacturer specifies. Having an extremely closely machined inner race spacer will achieve that.This is probably making it sound all-to-hard, when in real life it"s not that complicated. Most of us will have quite a bit of experience at replacing wheel bearings in trailers or caravans and in cars. Most of us will simply torque up the outer split-pin nut to the point where the wheel is obviously getting hard to turn, then we back off just a tad. Then a week of so later we do a final adjustment of the split-pin nut after the bearing has had time to bed-in (by tightening the split-pin nut a tiny bit more, again by "feel"). Remember that our automotive bearings don"t use spacers between the inner races (except good old British Leyland, who actually specified that the inner races of Leyland Mini wheel bearings have a protruding stub collar so that when the wheel bearings are tightened each stub collar butts against its opposite number or that a thin shim-ring gets squashed between the stub collars if a shim-ring is needed - see photo).My suggestion of using a precision spacer between the opposing inner races is simply a means of ensuring that it will be possible to properly tighten the "Jesus Nut" to the full torque rating before inserting the split pin, without any risk of the outer races being too compressed and the hub being made very hard to turn.There is one other down side to the possible use of opposing taper roller bearings - they are potentially much more difficult to seal effectively. Remember that car and trailer hubs simply have an outer bearing cap, and that the oil/grease seal is running on the stub axle inboard of the inner-most bearing. Such an arrangement would need to be repeated in a gyro hub using opposed taper roller bearings.After this mini-essay, I have arrived at the same conclusion Muz has - given that Dr Bensen"s industrial washing machine bearing has had a 50+ year "history of safe operation" (when fitted correctly), I really can"t see any compelling reason why we should move away from the double row ball bearings we use.Mark R

[RossM]

http://www.skf.com/mena/products/bea...5007206Looking at the the link, looks like each row of bearings are put in from the side the sit on.Therefore (filling notch) would be on both sides.Post a photo Nic when you get them!, or pull seals out of old ones and photo of them.Mark, you can play with the Bearing Calculator in the linkRoss

[MadMuz]

A couple of things re wheel bearings that I have also noticed... is at some time in the late 80"s, even car manufacturers went away from tapered roller bearings on the non drive end of cars. My 81 Lancer had tapered roller front bearings, but my 87 Barina had ball bearing rear bearings and from what I have seen from modern vehicles, very few use tapered rollers any more? I am not sure if this is for cost reasons, or simplicity (not having to set up). I know rear tapered roller bearings on rear diffs of old rwd cars, the single tapered bearing is always trying to pull itself out of the bearing... that is why some folks tack welded the collar to the axle.... others circlipped them..... to me, the fact that car manufacturers seem to have gone away from tapered

[gyroo]

Howdy Ross,Thanks for that - from memory, for bearings that do have a filling notch, it usually is visible only on one side. This must have something to do with how they"re assembled, but that"s completely outside my knowledge - I"m just guessing. Only a bearing assembly technician would be able to detail what mechanical trickery is used in the final assembly sequence.I"ve pried enough of these bearings out of salvaged hub blocks I"ve bought or collected over quite a few years to know that some have notches and others don"t, but I have usually immediately destroyed and chucked them in much the same way as Muz suggests for much the same reasons. In fact, it is my own personal policy to never re-use any rotor hub component that has been in a tip-over, even if it looks undamaged or not damaged or distorted. I use them as patterns and/or paperweights. There is always the possibility that the tip-over has resulted in internal cracking - this is particularly important in relation to tower blocks and side plates.Mark R

[birdy]

Iv never ever fitted a bearing of any sort in anythn without first lifting the seals off n packn with proper ( high temp) grease. Unless its oil lubed of corse.Also, iv never lifted a seal off and found anythn but shippn grease.This is not grease, its only there for preservation.Iv taken rotor bearings to 800 hours ( working) after packn with HT wheelbearing grease, and they are still like new.I use high temp grease coz anythn else simply melts out wen parked in the sun for abit.Lubrication is everythn.The highest quality zillion dollar bearing wont last 2 mins without grease.

[tonydenton]

obviously the big guys do have cup / cones,[ I stand corrected ] my experience was from the school of hard knocks, the boat shaft bearing was a failure.it had the same vibrating engine too , no one died cause it was a boat. the design and parts were changed with a single ball bearing . it got out of the creek and went to sea and for years.

[MadMuz]

Mark, from memory the ones with filling slots have the slot on the inner ridge/cone but not the opposite outer, so all balls are fed in to both rows from the slot side. Once all the balls are in the groove line, the cage is put in to spread them evenly and a small amount of grease is added..... too much grease just makes it harder for the balls to freely move (like us trying to run in mud) excessive grease will also just push the seal off one side or the other. Many people who add extra grease

[MilesW]

Where does one buy a quality bearing for around 30 dollars? SKF stiff me closer to 120 for one of their finest.A good test for your bearing is to every now and then when the urge strikes, immediately on landing, stick forward, engine off, not rolling and sit there with the rotor winding down from near flying speed. You will hear/feel anything untoward. Best with your headset still on or a set of foamies in your ears. Miles

[MadMuz]

True Miles, or if it is safe to do so,

[NiqueNaque]

If hearing what your bearing is doing is a risk, you could tape a microphone on to the torque tube or bearing bolt (if it can be reached) and record it on a phone or small digital recorder. Of course taking care the cable, microphone and recorder were safely & securely attached.

[Russell]

Well bugger me.....ol mate nicky nack.........you"ve been on one long honeymoon son, you worn " it" out.. ;D

[MadMuz]

Or you could tape a stethoscope to your mast .... then you could play doctors while you fly?

[NiqueNaque]

Ha, at least it didn"t go "Russty"...