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Feb 28, 2018 10:24 am
Feb 28, 2018 10:24 am
Subject: V12 timing gears
I am new to the club and this is the first post on the forum. I have a 1940 V12 SWB saloon with an S2 engine. I have posted photos on the gallery under Charles Milne Atkinson.
The engine is now completely dismantled and we have found it was previously fitted with liners and glacier type shells in the big ends. Nothing horrendous has been discovered but there are questions on the front timing gears.
The large idler gear was aluminium and had to be destroyed to dismantle the spigot it is mounted on as the whole thing had sized up and the gear had been rotating on the bushes rather than the bushes rotating on the spigot.
The spigot is cracked so I need to source or make a new one. (Any thoughts?) The S1 spigot is different and has the thrust face riveted on with Aluminium rivets. It is also thicker. I believe the S1 engine had a bronze idler gear as I have one to compare.
The rotation of the idler gear we need viewed from the front of the engine is anti-clockwise.
I had originally thought the square on the stud that retains the front thrust face would mate with a corresponding square hole in the removable front thrust face. This is not the case and as the stud has a normal right hand thread there is an anti-clockwise force on this thrust face when the engine is running. Although the gears are helical cut and the driving force from the crankshaft will tend to force the idler gear back; under the load of driving the cam shafts it could force it forwards. I am aware these engines suffer from failure at the front end but haven't established exactly what this failure mode is. I suggest modifying the washer so it is held with a key or dowel to take any rotational load so that the rotational load is not applied the the retaining nut.
Any information as to sourcing of parts and prevention of failure gratefully received.
I have tried to upload a couple of photos showing S1 & S2 spigot but I am not sure if they will appear.
Kind regards
Charles
Attachments:
I am new to the club and this is the first post on the forum. I have a 1940 V12 SWB saloon with an S2 engine. I have posted photos on the gallery under Charles Milne Atkinson.
The engine is now completely dismantled and we have found it was previously fitted with liners and glacier type shells in the big ends. Nothing horrendous has been discovered but there are questions on the front timing gears.
The large idler gear was aluminium and had to be destroyed to dismantle the spigot it is mounted on as the whole thing had sized up and the gear had been rotating on the bushes rather than the bushes rotating on the spigot.
The spigot is cracked so I need to source or make a new one. (Any thoughts?) The S1 spigot is different and has the thrust face riveted on with Aluminium rivets. It is also thicker. I believe the S1 engine had a bronze idler gear as I have one to compare.
The rotation of the idler gear we need viewed from the front of the engine is anti-clockwise.
I had originally thought the square on the stud that retains the front thrust face would mate with a corresponding square hole in the removable front thrust face. This is not the case and as the stud has a normal right hand thread there is an anti-clockwise force on this thrust face when the engine is running. Although the gears are helical cut and the driving force from the crankshaft will tend to force the idler gear back; under the load of driving the cam shafts it could force it forwards. I am aware these engines suffer from failure at the front end but haven't established exactly what this failure mode is. I suggest modifying the washer so it is held with a key or dowel to take any rotational load so that the rotational load is not applied the the retaining nut.
Any information as to sourcing of parts and prevention of failure gratefully received.
I have tried to upload a couple of photos showing S1 & S2 spigot but I am not sure if they will appear.
Kind regards
Charles
Attachments: