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the unused boss

vibrac

Well Known and Active Forum Website User
VOC Member
On the bottom of the reasonably early twin crankcase I have there is a plain projection underneath the chain case at the bottom of the clutch housing at the back.
It looks more like a projection for a drain plug than a sprue stub
Was this ever used by the factory for a drain? and I guess unless the intention was an elaborate one it would drain the chain case not the clutch housing.
(You see I can do minutiae as well;-))
 

clevtrev

Well Known and Active Forum Website User
VOC Member
On the bottom of the reasonably early twin crankcase I have there is a plain projection underneath the chain case at the bottom of the clutch housing at the back.
It looks more like a projection for a drain plug than a sprue stub
Was this ever used by the factory for a drain? and I guess unless the intention was an elaborate one it would drain the chain case not the clutch housing.
(You see I can do minutiae as well;-))
It`s on the bottom of most cases, it is probably there to enable the engine to stand on its own feet, without rocking.
 

john998

Well Known and Active Forum Website User
VOC Member
Hello, I believe it was for a drain plug, but proved to be too vulnerable to being damaged on bad surfaces,so was left undrilled. John.
 

clevtrev

Well Known and Active Forum Website User
VOC Member
Hello, I believe it was for a drain plug, but proved to be too vulnerable to being damaged on bad surfaces,so was left undrilled. John.
No way. The boss is immediately below a bolt hole, and also if it were to be a drain, there would still be a lot of oil left in the chamber.
 

vibrac

Well Known and Active Forum Website User
VOC Member
I normally agree with Trev but this time I will take a punt. Although the boss is on same horizontal as the flat bottom of the engine. all the gearbox towards the sprocket is a good half inch below that level so rocking does still occur if pressure is applied on that side. If it was a bench steady would not a further boss would be under the gearbox?
my preference is still on a drain plug that was never used - any more ideas?
 

Comet

Well Known and Active Forum Website User
VOC Member
HAHA, yeah, I'll go with Ossie.
I can just imagine the conversation in the drawings office/snug bar now.
"and if we cast a nob in here, those chaps will be baffled in 50 years time by what it was for. Now who's for another pint?"
 

jim burgess

Well Known and Active Forum Website User
Non-VOC Member
HAHA, yeah, I'll go with Ossie.
I can just imagine the conversation in the drawings office/snug bar now.
"and if we cast a nob in here, those chaps will be baffled in 50 years time by what it was for. Now who's for another pint?"
This I could easilly believe...
Jim Burgess
 

vibrac

Well Known and Active Forum Website User
VOC Member
HAHA, yeah, I'll go with Ossie.
I can just imagine the conversation in the drawings office/snug bar now.
"and if we cast a nob in here, those chaps will be baffled in 50 years time by what it was for. Now who's for another pint?"

At 3D a pint and no breathaliser they could afford to
 

ray vinmad

VOC Drawings Manager
VOC Member
My guess is that it is to stabalise & level the rough casting for marking out prior to initial machining & they found it useful to leave it on to stop the assembled cases falling over.

Initial maching lugs are quite common, but usually get machined off & polished out. eg How would you mount the timing cover casting to machine the mating face & oilway recesses etc.

Ray... Sorry, got serious there for a minute!
 
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