Of interest to all those with later engines, information about ball and roller race damage.
Regards,
J. Kim Siddorn,
Of interest to all those with later engines, information about ball and roller race damage.
Regards,
J. Kim Siddorn,
We once supplied some pillow block bearings to a manufacturer of (large) portable generators. They failed rather sooner than they should have and this was put down to 'false brinelling' caused by the weight of the shaft and cooling fan which they carried together with vibration while being transported.
Could conceivably happen to rolling element mains of an engine with a good heavy flywheel being bounced about in a trailer for extended periods. But I suspect that with the easy life that most of our lumps lead it would take a very long time to develop into a full blown failure - condensation and the resulting possibility of corrosion are probably bigger enemies of the 'preserved' engine.
Paul Evans tells me that Proteus Gas Turbines have the starter removed & an electric motor inserted, thus rotating the shaft at 12 rpm during transport to avoid this problem.
Gosh ..........
Regards,
Kim Siddorn,
Not quite sure I follow that. If the damage is to the (static) bearing due to the interia of the shaft/flywheel/turbine as the bearing is forced up and down by external movement how is having the shaft rotating going to make any difference? It will even out damage to the shaft but not the bearing surely?
I'm guessing it has more to do with avoiding any shaft bending than bearing damage.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
=============================== It will take more than a little jiggling to bend the shaft. The bearing balls/rollers impacting on the same spot on the track can and will over a period of time causedamage. . A trip on a truck for a couple of hundred miles will do no harm.In fact engines are transferred between Bristol and East Kilbride on a regular basis,both turbojet(Pegasus) and turboshaft (Gem) I must admit I have never heard of let alone seen the Proteus motor mentioned although the sleeve valve piston engines had a barring over motor fitted when installed in the aircraft to slowly turn the engine over to clear the bottom cyls of any excess oil prior to starting after an extended shutdown.On test we had to use a b****y great bar on the dyno shaft,on a cold morning it took two people to complete the op. Mike.H.
Paul Evans has a Proteus generating set & the info came straight from him.
Dunno Mike ;o))
Regards,
Kim Siddorn,
"Mike.H."
It will take more than a little jiggling to bend the shaft.
I remember seeing a turbine hall full of Proteus sets when I was on a CEGB familiarisation course at age 15, 34 years ago :-(. We were told then that the sets were turned over on a pony motor to stop the shafts "hogging" or taking a permanent set due to gravity.
Regards
Pete
I was told this years ago about large steam turbines, hence my previous comment.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Concorde had to keep her engines turning 20mins after landing till the engine had cooled down some so nothing hot started drooping...
Joules
Most high speed engines/turbines need to be run down properly. You shouldn't switch the engine off in my car until it has idled for 10s so the turbo has run down.
But this isn't the same a bearing damage due to bumping or shafts sagging under their own weight.
I've always considered it good practice to allow the engine to tick over for a few minutes having taken it off load - ie, arriving! The coolant will carry the extra heat away from the head & even up the engine temperature. At least in theory, it should make your head gasket last longer.
I learned this whilst working with Rolls-Royce cars in the 1970's.
I'm only mildly surprised to hear that shafts can sag under their own weight, after all, my tyres take a flat set overnight & it is very noticeable after a fast run followed by a cold night on concrete.
Regards,
J. Kim Siddorn,
Ex Rolls engineer that used to build the engines....
Joules
I think you have been mis informed I spent many hours on the Oly 593 and even after running on reheat for an hour or more 5 mins at ground idle was considered sufficient to cool before shutdown. Shaft bow could occur and was rectified by carrying out a 5 min dead crank ie rotate engine on starter with fuel shutoff c*ck closed and ignitors off. Shaft bow also occurred occasionly on the Pegasus engine and was rectified by running at low speed until the vibration level dropped to normal usually
15-30secs. Mike.H. Ex RR main engine test BristolFair does, it was relayed word of mouth to me.
Joules
We used to come across the problem of fatigue cracking in whitemetal bearings of marine genset diesels & in some cases the cracking was initiating in non-running diesels. Because they would typically be installed as a set of three on the same deck plate - and 1 or 2 would run as needed with a third as standby - the non running set would get a lot of transmitted vibration but no lubrication - hence fatigue cracking. Phil
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