the unused boss

vibrac

Well Known and Active Forum 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

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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

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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

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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

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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

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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

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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

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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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