Camshaft Trough

[Nourish]

Yes - I like that idea but may be I'm not that creative with my thinking
Picture 1 'Brandis's' Cases with tappet blocks fitted.
Picture 2 Paper template of block pushrod tunnel over crankcase
Picture 3 Bottom of block

[chaterlea25]

HI ALl,
I do not believe that the inlet rocker supply is enough to lube the cam and followers
I think a window/shelf would be essential to catch oil thrown from the crank.
I do not know how feasable it would be to tap into the PRV leak off port so oil could be diverted to the cam?

John

[Swarfcut]

CJ... The early cases vent downwards into the oil pump cavity so to take any feed from the blow off side of the PRV will require major amendment and addition. The window and deflector blade are certainly easier for starters. But a direct feed to the trough (maybe with a needle valve to control the flow) via external pipework hidden under the magneto is also a consideration. I wonder if there is space within the void at the rear of the crankcases to introduce pipework into the base of the trough.

 Swarfy.

[Nourish]

Why is there a problem with cam wear - is it a general lack of lubrication or that on start up the cam is dry? This trough would retain a pool of oil especially if a centre stand was used.
A separate oil feed would certainly help with the bore lubrication though.
There could be space for a small banjo under the magneto above the gearbox and would be quite unobtrusive. Perhaps using some Lumiweld to fix a boss in there to tap.
What would be the point of adding an adjustable jet though - how would you ever know the result of your adjustment?
How much oil would be needed and how much would the return oil line return through say an 1/8th" diameter opening?

[Radlan2]

Another thing, did original parts fail because of incorrect hardening? Newman cams were very helpful to me with additional case hardening when a set of late type pattern followers I bought could be easily filed.
   Can the later pump which has fewer teeth be used and use rocker banjo bolts with more flow?
         Chris

[trevinoz]

Triumph had problems with poor exhaust cam lubrication. The solution, so I believe, was to nitride the camshaft. Maybe have the followers treated the same or have a hard face applied.

[Swarfcut]

  Compared to the later design the Longstroke cam lobes are narrow and the followers equally miniscule to match. The surface loading is higher, the springs are the same on all iron head engines. So whether it was poor engineering or poor  surface treatment, some engines certainly had a high rate of wear. BSA had a think and came up with the trough, and the familiar wide base followers. Early short stroke engines do not have the blow off feed to the trough, so they must have still had a problem.

 The rocker feed can be looked upon as it's own little supply and return loop. However if this supply is too much,  the volume of oil being returned to the oil tank after the T off will  be less than the capacity of the scavenge side and oil will accumulate in the sump, going back to the rockers as a path of least resistance, rather than back to the tank. The size of the holes in the rocker feed bolts are critical to act as a metering function and I am sure this has been featured before. I suggested a needle valve as some sort of control of a trough feed  as an error in size of oil way outlet otherwise means another complete dismantle. So if a feed to the trough was added and the scavenge was overwhelmed, the flow could be reduced until the engine no longer wet dumped, and the cam still got a dose of lubricant. A hard ask to find the sweet spot.

 Later pumps with fewer teeth on the gears are indeed considered an improvement.

Swarfy

[Nourish]

This is my thought at the moment - please excuse the crude picture - but you can see hopefully what i'm imagining. Build up a little boss behind the cam and drill and tap for a jet to just sit over the trough. Putting an adjuster in there might be a bit fiddly so perhaps one up further in the line. I think it will be all too much to try and get it fed from the PRV so it would have to be from the return line that goes up to the rockers.

[trevinoz]

I have several longstroke camshafts lying about. Interestingly the ones with a part number on the end are mostly badly worn. A couple of cams with no number are quite good. In fact I used one of those in the engine which I built several years ago, along with new followers.
This exercise to reinvent the engine is laudable but in the end, how many miles per year is this bike going to do?
You must remember that in the day these bikes were daily riders with probably few oil changes and the oils of the day were not of the same standard as now.
Even the later type engines complete with trough have significant wear on the cam and followers on high mileage bikes.
This is not in any way criticising your efforts, Nourish.

[Nourish]

Yes Trev - these thoughts had been running through my head too!. But as someone had mentioned the idea of a camshaft trough and so as the engine is apart I made one.
Then it was mentioned that this could starve the cam of the splash lubrication so an additional oil feed might be required - but then where does this oil feed come from? - What seems like an easy solution snowballs into as what you described as a re-invention of the motor.
If we were all sat around a table in the design office then we would all know what was required but as is the nature of a forum like this that people chip in as and when they can.
 and so my ignorance and impatience creates a one step at a time approach to this design(?).
Please do not think that this is a criticism in any way as this is what I asked for and indeed wanted so please keep your thoughts coming forward.

P.S. Bowden Engineering here in Bristol worked on such a project but regretfully Gary died some years back and his efforts are not known to me.

[berger]

Nourish the job you doing reminds me of myself doing any job, i think i will just do this job it shouldn't take long , 9 hours later and scores of tools laying about it still isn't done . no offence to you and i hope you sort it to your satisfaction, doing well so far

[Nourish]

EXACTLY!

[Tomcat]

My 2c worth on the subject.
I had a 1948 Longstroke for 18 years and after rebuilding the engine had no cam or valve problems. YA7 engines had no oil feed to the intake rocker shaft (IIRC the first engines had no oil feed to either rocker shaft) so I added a later oil feed to the intake even though it wouldn't win a concours prize LOL. IMHO as a 'toy' motorcycle with limited mileage I think this is all overkill and not something to be worried about. Two things to consider, the oil of 2026 is far superior to oil made in 1948 so oil mist lubrication will be fine and wet sumping lubricates everything inside the engine on start up, something for nothing there!