MetalworkingFun Forum

Bugger! I just saw that you had replied Bill and was expecting a progress report. I had a weekend where everything else got in the way of my plans, so I understand your situation!

Hi Bill
May I use your thread to ask a Radial engine question, that I am sure you will know the answer ,But this is aimed at the head scratchers of the group.
As I understand it the valve and ighition timing of no 1 cylinder on any bank is different to all the other cylinders on that bank.
this is taken care of by re positioning the cam followers on No1
and altering the cam on the magneto.

WHY.

Brian

Where did that info come from ? Here is what I used to time my radials. But then mine are not magneto fired. I was and still am unaware of any differance.

http://digital.library.unt.edu/ark:/6753...807/m1/78/

"Billy G"

(10-13-2012, 02:12 AM)Bill Gruby Wrote: [ -> ]Where did that info come from ? Here is what I used to time my radials. But then mine are not magneto fired. I was and still am unaware of any differance.

http://digital.library.unt.edu/ark:/6753...807/m1/78/

"Billy G"

Yes Bill the info you have is is perfectly correct, and will work perfectly. But the remaining cylinders may have a slightly different timing built in by the maker. its a case of 'Need To Know' as far as the mechanic is concerned.all the parts only go together in one order.
What is different about No1 on your engine?

Brian.

#1 is the only piston one connected directly to the driveshaft. The others are conected to it via slave rods.

"Billy G"

(10-13-2012, 08:18 AM)Bill Gruby Wrote: [ -> ]#1 is the only piston one connected directly to the driveshaft. The others are conected to it via slave rods.

"Billy G"

OK Bill you are on the right track,

So how will this alter the timeing??

Brian.

I LOVE old aircraft and of course seeing a 1/6 scale P&W thread I had to open it. I lost about 40 minutes of sleep and it was worth every second! This is absolutely amazing Bill! Keep the pics coming

Because of the connecting rod geometry, the cylinder with the master rod is the only one where the piston TDC is the same as crank TDC. The others lead or lag by a small amount. In P&W 14-cyl engines the master rods are in #6 and #9 cylinders, but ignition timing is set from #1 cylinder. At one time, compensated magnetos to correct ignition timing were optional, but the later engines did not have them. Compensated mags were only used on the 14-cyl engines, the R-1535 and R-1830 series.

Regards,
Bob

That's it Bob
The big end of the master rod is the only one that follows the true circle of the crank.
The slave rod big ends have a elliptical path, so piston position per degree of crank angle varies.

Brian.

(10-14-2012, 02:20 AM)Brian Wrote: [ -> ]The slave rod big ends have a elliptical path, so piston position per degree of crank angle varies.

Brian.

The things you learn on this forum are amazing.
It makes sense, after the fact of course.

Thanks Brian!