Camshaft Trough

[Nourish]

Much has been said about the lack of a trough for the camshaft and the resulting weak point in the lube system but has anyone built in a trough to tackle this problem? Id be wary of welding the cases but would there be another way to fix something in there?

[JulianS]

The A65 also did not have a cam trough. So like the long strokes the cam gets lubricated by mist, throw off from the crank etc and by oil draining down from the rocker box.

For the 1967 season A65 BSA made a small mod to the lubrication system, to improve cam lubrication they said, by moving the rocker  feed from the oil tank end to the crankcase end of the oil return line. I wonder if a similar mod could be engineered for the long stroke?

First page of the September 1966 bulletin attached shows what BSA said.

[Nourish]

Mmmm - I wonder if that really made any difference?

[Black Sheep]

Norton twins had a trough up until the Commando was introduced - at which point camshaft failures became relatively common.

[Triton Thrasher]

Mmmm - I wonder if that really made any difference?

Yes it’s hard to see the fluid dynamics theory behind it.

[Radlan2]

     There is a mod which I and others have done to later pre unit twins which have the trough though at some revs/oil pressure it might not be filled so this is a bit belt and braces.
      Plug the push rod tunnel oil return drain holes which means oil must return past the followers, leave the exhaust drain holes clear.
      Cut a shallow groove along the length of each follower on the rear face which will now allow more oil to pass. I have made a simple jig guide and cut the groove with 1mm slitting wheel in the angle grinder.
       As the cam turns a wave of oil will now be drawn across the follower/cam wipe area.
       Also of course use high zinc ZDDP oil.
       I don't know if this can be applied to the long stroke motor but hope you get the idea.
      Cheers
          Chris

[Swarfcut]

 This modification was featured in one of the mags years ago, in an article  "How to fettle BSA Twins" written by Cake Street Classics very own Roger Sharman. It would be difficult to replicate on the Longstroke without compromising the cam followers which are thin and long rather than short and fat.

  A Ford Pinto OHC  type spray bar arrangement fed by some devious means from the rocker feed line crossed my mind, but a fabricated trough is a far simpler solution. Having said that, space is a bit tight owing to the crankcase shape and internal clearances between the moving parts.

 Swarfy.

[Nourish]

Well I've been playing out in the workshop - Anyone see any drawbacks with this?

[berger]

i see thought and dedication  going to have a black&tan for your effort .

[berger]

the only drawback i see is oil drag on the cam reducing your speed from 105 to 104mph

[Nourish]

 

[Swarfcut]

 I reckon that is quite remarkable. In the later cast in trough engines, the lowest point overflows oil to the drive side of the flywheel and this gives that bore an extra dose of lube..... Probably why some bikes smoke more on that cylinder. So maybe a small cutout at that end as an addition.

  Looks as if the ensemble locates on the camshaft bushes and the support web will be welded on. Very clever solution with no major surgery to the castings, and the cases will split easily as and when required.

  Make sure that cam drive gear is on nice and tight to start with..... It will be impossible to hold the cam when all is assembled.... but of course you knew that all along.
 
  Getting lubricant replenished into the trough needs further consideration. Is there a wide enough passage to allow rocker box oil to come down the pushrod tunnel and past the tappet guides?  Would this be adequate in any case? This engine relies more on oil thrown up from the crankcase to lubricate the cam faces but now the cam will be effectively shielded from this oil, without an adequate supply to maintain the trough level that's another conundrum. May need an extra direct feed from the rocker return and a bit of external plumbing.

 Swarfy.

[chaterlea25]

Hi Nourish,
I forsee an issue or 2 with your very neat idea 
On the later engines the trough is "primed" by the PRV bypass drillings mostly on start up when the pressure is highest,.
Then when running oil is thrown from the big ends and some gets into rhe trough, next oil gathers in the head and drains down the pushrods / followers to the cam. I do not believe enough oil will be available from the head for the cam?

As far as I know the long stroke does not have  drillings from the PRV ? So no oil from that on the longstroke
As your trough is closed on the crank side no oil will get to the cam from the flywheel or big ends?

What about this for an idea 
Cut a window on the crank side of your though  and add a "scraper" / deflector  wing that would gather oil from the flywheel/ big ends to  feed the trough

1930's BSA's and Royal oilfields used the scraper principle to return the oil to a seperate crankcase compartment

John

[Nourish]

I thank you all for your replies and  hope we can keep it going. I do like the idea of directing the overflow towards the drive side cylinder and that's easy.
Munro in his 'Twins' book talks of the oil mist lubrication and the consequent adoption of the oil feeds to the rockers because of dry start ups.
The Long-stroke middle tappet block has an 1/8th" drilling to pass oil down to the cam but I suppose this is thought not to be enough but slots could be cut down the backs of the outer tappet blocks to aid this but would this be at the expense of lubrication to the tappets themselves - or/and open up that 1/4th" drilling? Could an external feed be added to the pushrod tunnel in the barrel - would this help? - as the magneto is in the way to add an oilway into the cam from the rear of the crankcase.
* Just realised the Crankcase/Barrel Pushrod Tunnel is not sealed and any excess oil just runs down into the crankcases!

[Swarfcut]

 Looks like time for a bit of creative gap filling, The tappet guide retaining plate  could be substituted for a plate that fills and blocks completely the remaIning narrow aperture between the cylinder base face and the crankcase where the tappet guides sit. Then all the rocker oil has to go into the trough.

 Swarfy.