Rocker Shaft Orientation

*Not only did I see the article in RH, but I observed the conversation on the forum.
The lack of clarity between when the low pressure system and high pressure system were being rationalized. did not help at all.

Madnorton said:

the hole in the ball end and thus the drilling in the rocker is shut off for a large portion of time in use

Click to expand...

exaggeration?
Each rocker is actively (loaded) about 40% of the time. So the top gap is extra wide at the top since the rocker is loaded on the bottom against the shaft.
60% no load duration: therefore the oil should flow equally around the shaft during this period.

Madnorton said:

The rocker spindle flat was extended along the spindle,

Click to expand...

To me the very simple reason for a flat extension is for an oil reservoir: ( this was offered by Phil Hanam and seemingly rejected by some!)
After a bit of thought , I wholeheartedly agreed for these reasons.
1. It assures an oil quantity on the leading edge of the rocker to be swept under the shaft.
2 Note the flat is directly IN LINE with the diagonal stress axis, which is between the ball end and the valve tip

3. the original HP rockers shafts only had a small hole
4. this was during the early wide rockers THEREFORE the outer aluminum shaft support was short.
5. With such little oiling, I could conceive, when hot, the under oiled rockers would gaul and seize the shafts and ruin the head
Ruined heads from early no flat/small hole HP rocker shafts is occasionally discussed.

Madnorton said:

The rocker spindle flat was extended along the spindle, not wider so as to increase its arc, why? when it faces away from the rocker, anyones guess. The scrolled spindle may have had a flat at one stage, The flat was an addition to the plain spindle, it then change in dimension.

Click to expand...

Can't you be explicit as to HP or LP?

The scrolled LP shafts with flat:
1. IMO flat should also face away from the ball end for the same reason as for the flat/reservoir in the HP shaft.
2. Looking at my new LP shafts w/flats in the sealed bag AN/bsa regal, scrolling is also non symetrical leaving a different oiling pattern if used on RH or LH side. This is poor engineering/production. (junk)
3. Genuine real norton factory take outs are very symetrical and will function identical mounted in RH or LH side. . . and have flats.

L.A.B. said:

May have but it doesn't now, and wouldn't need one with a central groove and scrolling so if there was an earlier spindle with a 'flat' then it would seem to be for the low-pressure rocker feed requiring a different orientation and possibly the reason for the apparent error in the pre-Commando manual.

Click to expand...

Above is nothing I would want to buy for myself or use in a customers engine.
Looks like they would be inferior at adequately oiling the rocker action.

information errors in the MKIII manual? So what else is new. . .

dynodave said:

Can't you be explicit as to HP or LP?

The scrolled LP shafts with flat:
1. IMO flat should also face away from the ball end for the same reason as for the flat/reservoir in the HP shaft.
2. Looking at my new LP shafts w/flats in the sealed bag AN/bsa regal, scrolling is also non symetrical leaving a different oiling pattern if used on RH or LH side. This is poor engineering/production. (junk)
3. Genuine real norton factory take outs are very symetrical and will function identical mounted in RH or LH side. . . and have flats.

Click to expand...

Apparently there are:-

LP scrolled spindles with flats.
LP scrolled spindles without flats.
Early HP plain spindles without flats.
Late HP plain spindles with flats.

DD, are the oil holes actually in the flat area or do they also have the central groove with the hole there and is the flat off to one side (inner?)?

Or, any chance of a photo (anyone?) of an original LP spindle showing the flat (and oil hole)?

L.A.B. said:

Apparently there are:-

LP scrolled spindles with flats.
LP scrolled spindles without flats.
Early HP plain spindles without flats.
Late HP plain spindles with flats.
DD, are the oil holes actually in the flat area or do they also have the central groove with the hole there and is the flat off to one side (inner?)?

Click to expand...

top norton MC LP shafts- best design completely symetrical-wide oil coverage for rocker- maybe poor residual for ball end?
2nd LP shaft, right hand scroll despite RH/LH use, not great ! (in 2 early heads) 1 was out of R12/136
3rd LP NA/BSA regal maybe not so bad..almost symetrical for RH/LH

dynodave said:

top norton MC LP shafts- best design completely symetrical-wide oil coverage for rocker- maybe poor residual for ball end?
2nd LP shaft, right hand scroll despite RH/LH use, not great ! (in 2 early heads) 1 was out of R12/136
3rd LP NA/BSA regal maybe not so bad..almost symetrical for RH/LH

Click to expand...

Thanks for the photo!

And so it becomes clear (clearer).

The flat on the low-pressure spindle should face inwards as it is the flat that's intended to align with the rocker arm drilling and not the oil hole! With the hole in the groove, its actual position would seem to be of less importance.
Edit + Image:


I'd say this was the reason why the Atlas manual states "flat inwards" as it was referring to the low-pressure spindle flat and not the oil hole and was an error carried over from the low-pressure system information!

The article in Roadholder not only plays down the difference between the low and high-pressure rocker feeds but completely overlooks the fact that the low-pressure spindle oil hole isn't in the flat when comparing it to the high-pressure spindle.

So potentially there could well be engines out there with the incorrect spindle design fitted.
Is is possible to assign the correct photo & design against model/year/ cc etc.??

olympus said:

So potentially there could well be engines out there with the incorrect spindle design fitted.
Is is possible to assign the correct photo & design against model/year/ cc etc.??

Click to expand...

There seems to be two part numbers for the low-pressure scrolled spindle, D12/97 and T2237 but which could be the same or interchangeable parts?

The recent production scrolled spindles don't seem to have the flat, at least I can't find any of the very few images of the T2237 spindle that shows a flat which might suggest that some time in the past the flat was deemed unnecessary.

An LP head with flat to ball end, fed with HP oil could be a over oiling mess...
I still have a few very old heads 49 & 53 that may have never been pulled apart. I may have a final look as to flat orientation.
I can also assemble a mock LP head and measure on my oil pump test rig if different flow for different flat alignment.

olympus said:

So potentially there could well be engines out there with the incorrect spindle design fitted.

Click to expand...

You could feel well assured that every incorrect combination has been assembled and exists

olympus said:

Is is possible to assign the correct photo & design against model/year/ cc etc.??

Click to expand...

Not practical to make a childish assumption to assign an internal parts configuration in a free world where the "know it all" upgrade crazed owner does what he/she wants.
How would that play out with "your" bike and the front end you used on your frame?

A data table with LP-HP-3start-6start for all NHT with original and suggested components might be the best that can be done. The suggestions could be supplemented with engineering rational to substantiate the suggestions.

dynodave said:

A data table with LP-HP-3start-6start for all NHT with original and suggested components might be the best that can be done. The suggestions could be supplemented with engineering rational to substantiate the suggestions.

Click to expand...

What was originally speced as OE is all I'm suggesting

olympus said:

What was originally speced as OE is all I'm suggesting

Click to expand...

Nothing wrong with that except part number in a part book does not show a description to allow visual verification of the desired component.
So the 66 small hole/no flat HP shaft is NOT desireable and the parts book PN would be undesireable.

dynodave said:

Nothing wrong with that except part number in a part book does not show a description to allow visual verification of the desired component.
So the 66 small hole/no flat HP shaft is NOT desireable and the parts book PN would be undesireable.

Click to expand...

Or simple photos (as you posted earlier) with a line of text indicating to what variant you are referring and what model, year, engine number etc it relates to..??

I can do the part numbers and drawing dates and subsequent dates of changes made to the drawing if that helps.

Madnorton said:

I can do the part numbers and drawing dates and subsequent dates of changes made to the drawing if that helps.

Click to expand...

A full pictorial of the full NHT LP-HP-3start-6start rocker shaft series with correct original use (heads & engines) applications would seem to be useful. Additional well researched pro's and con's of each should help one select the best combination of components.
Bad information is unfortunately too readily available.
Unfortunately here in NA (north america) pre commando stuff is almost disappeared or hiding and research is very difficult.
It is not "luck" that I own over 30 NHT engines from 49-75, but I still do not have every NHT version...I don't do hybrids
I think, I am short only the "daytona" cam of having all the production cams profiles
I probably have all the NHT heads except the short stroke head.

I may be wrong but I thought the Roadholder article related only to Commando engines. I quote:-
But the 1970 manual for the Norton Commando States: ... rocker shafts fitted with the flat facing rearwards on the inlet and forwards on the exhaust...
Therefore mention of low pressure / high pressure and scrolled shafts are not relevant. I believe all Commando engines had plain shafts.
When Norton changed the way the shafts were fitted, did they say it was because the oil pressure to the big end shells was insufficient and this was a way to increase pressure? Or did they do it to prevent flooding of the head and subsequent smoking?

tombstone said:

I may be wrong but I thought the Roadholder article related only to Commando engines. I quote:-
But the 1970 manual for the Norton Commando States: ... rocker shafts fitted with the flat facing rearwards on the inlet and forwards on the exhaust...

Click to expand...

If the first two paragraphs and the following paragraph of the quote from the article are not included then it could be read that way.

tombstone said:

Therefore mention of low pressure / high pressure and scrolled shafts are not relevant.

Click to expand...

In my opinion, it is, considering the article is attempting to compare low-pressure rocker spindles with high-pressure spindles by saying.
"The issue..." [perceived issue] appears to be that if they are fitted the way the factory built the bikes in the '60s, then there is too much oil in the head and the engine might smoke excessively." Too true "the engine might smoke excessively" as that's comparing low and high-pressure rocker feeds and different rocker spindles but completely fails to mention it. Talk about comparing apples to oranges would be an understatement!

tombstone said:

I believe all Commando engines had plain shafts.

Click to expand...

Yes, but the high-pressure rocker feed was officially introduced in 1966 from engine number 116372 so well before the Commando, therefore, the reference to "the '60s" is not only misleading but inaccurate.

tombstone said:

When Norton changed the way the shafts were fitted, did they say it was because the oil pressure to the big end shells was insufficient and this was a way to increase pressure? Or did they do it to prevent flooding of the head and subsequent smoking?

Click to expand...

They didn't simply change the way the spindles were fitted. What they did was to double the speed of the oil pump (by fitting the 6-start gear) and changed from the previous low-pressure feed from the scavenge side of the lubrication system to a high-pressure feed which basically dictates there has to be a restriction to maintain oil pressure as it says "4. Positive oil feed to the rocker gear - taken from the blanking plug on timing cover. Plain rocker spindles restrict oil feed" something that would have been immediately obvious yet the article states: "It soon became apparent that these modifications could result in more oil being fed to the head than could drain away, so the head would flood and smoking resulted. The 'solution' to this problem was to rotate the rocker shafts by 180° ...." which if "Plain rocker spindles restrict oil feed" is true then it would have been done from the very beginning and not turned around sometime later as it suggests so wasn't a 'solution to a problem' in my opinion.

Even with the plain spindles and flats facing away from the head I would think the high-pressure rocker feed pumps more oil to the head than the earlier 'spit and dribble' scavenge feed which is why I don't agree with the following statement:

"Rotating the rocker shafts in order to reduce flow to the head and thus to prevent flooding is a very poor solution as it reduces oil flow to the pushrods."

Once again it is suggested that it was 'a solution to a problem' but I don't think there's any evidence to suggest the high-pressure feed "reduces oil flow to the head" in fact flow is probably increased over the low-pressure feed, or that the spindles were fitted the opposite way to begin with and subsequently turned 180° as I believe the reference to "flats face inwards" in the later Atlas manual was for low-pressure spindles.

I wonder if anyone knows what rocker shafts Dunstall used ? Inhis tuning notes I think he advised reducing the width of the pressure side gears so that the pressure side of the pump balanced the scavange at 3000rpm on a 6start pinion...

The scavenge side is already over the capacity of the feed with the standard gears in the pump, making the feed side gears narrower will increase the margin not balance it.

oldmikew said:

I wonder if anyone knows what rocker shafts Dunstall used ? Inhis tuning notes I think he advised reducing the width of the pressure side gears so that the pressure side of the pump balanced the scavange at 3000rpm on a 6start pinion...

Click to expand...

I'm with kommondo on this one, Dunstall got his bikes/engines straight from the factory. The fact that he sold a six start worm for the oil pump in his catalogue was separate from the bikes he purchased.

oldmikew said:

In his tuning notes I think he advised reducing the width of the pressure side gears so that the pressure side of the pump balanced the scavange at 3000rpm on a 6start pinion...

Click to expand...

Dunstall tuning notes say that the earlier narrow gear pump was "the better unit for racing..." but modified to take the wider later pump scavenge gears.