Postby Merlyn » Wed May 04, 2016 3:48 am
Giving the matter further thought, ( as you do ) and thinking back over the years another method of measuring gear train back lash has sprung to mind. I will call it the MMM System ( Merls Magical Measurement System ) for I have never seen or heard of it being done before, however with care and utilising ( for me anyway ) the 1960's era technology concerning the taking of leads I feel it could maybe prove successful.
For those of you not overfamiliar with this subject I will attempt to explain as follows.
Should you not have any rolls of bearing leads then some 80/40 % electrical solder will suffice. ( 80% lead and 40% tin content )
Be sure you Mike up the OD of the solder to ensure it is slightly over the top limit stated.
Timing case cover off and degrease all gears, using maybe Mr Loctite glue carefully cut lengths off the roll equating to teeth width. Carefully attach the cut lengths of the solder to the exact PCD circumference diameter on all exposed teeth to run from the front of the teeth to the back face. Scribe the PCD onto the gear face with a pair of dividers.
Taking one of the Wartsila engines on this model I refer to we have a crank drive gear of 54 teeth driving an intermediate gear of 54 teeth whose other end has 29 teeth ( all cut from one parent metal ) which then drives the cam gear of 58 teeth.
Now we have already got a large no of teeth from which to take measurements from and in order to ensure no teeth are to be left out we have to ensure many turns of the crank are carried out.
Taking perhaps a photo of the end elevation of all the timing gear and we can then cut and make up out of stiff cardboard copies of each gear and teeth to ensure that when we place each and every bearing lead on it we have the correct setup displayed, it as per the timing gear, we can make use of any timing gear marks as a reference start point.
Applying Mr Loctite glue to the exact PCD diameter attach each and every lead across each and every tooth and fuel shut off wind the engine over slowly to obtain the maximum no of teeth readings.
Marking the teeth not done apply Mr Locktite Let Go Fluid and carefully detach every lead and place apon the cardboard cutouts you have made up making sure you duplicate each and every tooth, as per the engine.
Winding the engine over to expose all teeth you have not done repeat the process.
Now having superimposed all your cardboard cutouts with your leads out with your micrometer and start the long process of evaluating your resultsand carefully recording same.
Lot of work, I normally only do timing gears when doing piston liner/ crank grind overhauls although I do note the pitting and spalling present and damage to the gears shown on my previous write up caused possibly by the additional spring loaded gear forced against the other gear it's driving reducing at least the necessary oil clearance gap.
This reminds me of a demonstration by Wynns Oil Additives some 35 years ago, one roller bearing ( just one roller, no tracks ) detached from a large gas turbine rotor bearing in a jig, held by a counterbalance weight and driven by an electric motor. A few turns with engine oil splash lubed against it and Lo and behold, it's just like you held it against a grinding wheel and a big flat appears on the face up against the grinder.
Out of the jig with the bearing roller, in with another one, on with Mr Wynns and rev her up and 20 minutes later hey presto, no flat present!
That poor old timing gear shown on my last posting clearly shows that by being forced against the other tooth with no room for lub oil clearly shows how aged the gear has become before its time.
So TTTT for now, off to file for my patent in case someone else steals my idea.
In conclusion allways remember what your dear old Mum taught you " The Old Songs Are The Best " ie in this case The Taking Of The Leads Lives Forever. "
PS Don't forget to get the correct handed bearing lead substitute when purchasing , ( rotation wise that is )
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.