I, like you, have been really concerned about how much oil my Birnigham Scott needs and have talked to several people about it and have planned to read right through the Technicalitites. You post has now made me read throguh them. I suggest you do also, but let me give the run down on what I have got out of it:
There are three approaches to oil feed:
Note: all rates are to each side
1) total oil feed from the Pilgrim (with possibly a very minor oil addition to the petrol) which was the original design.
This is the method preferred by many including Glyn Chambers. But what is the rate. Glyn intalking to me suggests setting the pump up at 4 spits to the drop (4 to 1) though in the Technicalities he has said as low as 6 to 1. However, he notes (vol 18 No 9 Apr 1994) that 1 in 10 is OK for normal use IF YOU COULD rely on it. This is a common theme i.e. the Pilgrim pump is not relyable at the low dosage rates required by the Scott. In the Technialities, Glyn (7/9 Jan 72) has said that 6 to 1 is about as low as you can go with the pump and still expect it to be reliable. Brian Marshall (20/9 Apr 98) says that 4 to 1 is about as low as it will go. I assume that all of these are at tick-over speed.
But how does this relate to oil rate? Some others use drips per minute (dpm) which to me is a better measure. Goeff Milnes back in the ’60’s gave the instruction for my first Brum as “check it gives 15 dpm each side with the engin idling and add an eggcup full of oil to each gallon of petrol”. In those days this was, of course, ‘straight’ engine oil, probably SAE 30 for summer use.
The Book of the Scott notes the oil rate should be 20 dpm when running slowly for the running in period (1500 miles) and then 10 – 15 dpm for normal use thereafter. It also recommends addition of upper cylinder lubricant 1/2 oz to 2 gal.
However, I have not been able to relate ‘spits to a drop’ to dpm so cannot relate how the Technicalities compares to the dpm of the BotS.
The purpose of working through this is to illustrate that the Pilgrim needs to be set to minimum flow that is too much anyway and that dpm with old fashoned oil is about 10 – 15, so we could summise that 10 dpm is OK with modern oil.
2) The next method has been described as ‘half and half’ (and is what I use). It was stated by several contributors that the mains and glands need less oil than the big ends or top end and that petroil does not lubricate the mains/glands. This means that petroil can be used for the big ends and top end, and a reduced oil rate for the mains. In fact, most commentators simply refer to a fxed dpm in this case.
It should be noted that the standard Pilgrim cannot be adjusted down far enough to give the correct low rate of oil feed. It is therefore recommended that either a reduction gear is used (as I have) or the Pilgrim is converted to dripper operation (as you have). Bother were offered by Gerry Howard from the early ’80’s up to when I bought mine in 1999. (For those interested in the reduction gear, there are a couple of articles on how to do this by others).
So, what are the right settings and oil (which is the anwer to your question). Using modern synthetic pre-mix 2-stroke oil plus drip rates, the numbers suggested are:
i) Brian Marshall (20/9 Apr 98) 50 – 60:1 petroil plus no more than half a dozen dpm (which CANNOT be achieved with a standard Pilgrim)
ii) Ged Rumble (20/11 Aug 98) 50:1 plus 5 dpm (and provide heat insulation for the Pilgrim converted to dripper to avoid excessive temp veriations due to heating form the engine as the oil rate will be sensitive to temperature)
iii) Dennis Wray (7/10 Mar 72) 50:1 plus Pilgrim at min setting (4 spits to a drop) driven by a 3:1 reduction rear (‘equivalent’ to 12 spits to a drop at normal speed)
iv) Gerry Howard (17/8 Feb 92) 50:1 & cut Pilgrim down to min possible – if converted to dripper mode then use 4 dpm
v) Brian Marshall (19/1 Dec 94) 40:1 and 4 or 5 dpm is plenty for the main bearings and glands
vi) Dan Hewitt (19/5 Feb 95) 50:1 and has to use 10 – 12 dpm as does not have reduction gear i.e. min setting
vii) Richard Duffin (2007 conversation) 40 – 50:1 plus 6 dpm
So, this is a good indication of the sort of setting that is being used
3) The third option is full petroil as Titch recommends, but this needs a ‘cross-over’ conversion as petroil does not lubricate the mains and glnads. However, this is a significant mod.
There have been a lot of other ‘one-offs’ like Mavro & Lofty Lube, but are outside this post.