Vernier adjustment of Cam timing

[aussie bruce]

Hi all

I am finding it hard to nut out this one so here goes ???

I need to time a gear on a poppet valve steam engine and have it open 5 degrees BDC

i have some meat on the crankshaft to fly wheel area id 5/16 to 5/8 OD so can fit in a 1/16Th drive pin

Now the ticklish area is it 10 holes and 9 or 10 holes and 11 gives you vernier adjustment ???

Oh Great Gurus help is required :bow:

All the best gentlemen

Bruce

 

[gbritnell]

I'm not quite sure what you're asking. Do you want to make it so you can adjust the timing by 5 degree increments or just pin it at 5 degrees? What are the 9, 10 or 11 holes?
gbritnell

 

[kf2qd]

9 & 10 holes will give you 4 degrees adjustments. 1/10 * 1/9 = 1/90 (* 360 = 4 degrees) 9 & 8 holes will give you 5 degree adjustment. (1/9 * 1/8 = 1/72) I think you just want to be able to set the cam 5 degrees from TDC which means you can just pin it.

 

[aussie bruce]

Thanks for your replies Gbritnell and kf2qd

I am working on replica of Pisces II from a plan by Bob Kirtley its a flash steam hydroplane motor

The cam sits behind the crank and is buried deep in the motor rear end.
As its a Uniflow engine the cam runs at engine speed in bobs design he uses round pins to set the timing with a shroud over them to stop them ejecting at 15k rpm

I have modified his design slightly to use common metric bearings and have a bit more room so to speak so i was looking at modifying the design to utilise vernier pins at five degree intervals

from an manufacturing / assembly view point it would be easier to drill the holes in alignment and then using 9 and 8 holes set the timing to 5 deg BTDC

Many many thanks gentlemen you have set me on the path
:bow: :bow:

Best Regards Bruce