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ROCKER SHAFT END CAPS ADVICE


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Yeah I know.

I have been told about the overflow from a TR3 friend already years ago.

Knowing this I realized yesterday the oil supply of the rocker shaft could be low pressure

and the oil on a extra pipe to the valves would be missing a high pressure system of the crankshaft (my question).

The low pressure on the rocker shaft would makes sense because I guess the bushes of the rockers and the end caps are not realy sealed.

Will have a closer look this evening, my wife is out, this will be some relaxing hours in my garage :rolleyes:

Edited by Z320
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16 hours ago, BlueTR3A-5EKT said:

if the shaft has no internal plugs or if the replacement shaft has internal plugs that seal the shaft;   the end caps can be secured by split pins or roll pins as they are not required to form part of the shaft oil seal with the end caps. 

Peter, there are 'closed' roll pins you know! They won't form a perfect seal, but near enough for this application.

Pete

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On 12/11/2019 at 1:03 PM, Z320 said:

Sorry, allow me 2 questions:

- in the rocker shaft the oil is full or reduced pressure?

- isn't there a pressure reducing small drill in the cylinder head?

Ciao, Marco

The pressure of oil within a closed system (barring milliseconds delay from the pump) is equal in all 3d directions of the chamber.  That 'chamber' in the scenario of a car's hydraulic braking system is not spherical, but the same principle of physics applies throughout different cylinders with pipes interconnecting them. 

The pressure within a partially opened system (calculated tolerances / designed to restrict the size of all openings) is likewise equal in all directions of the chamber.  Likewise this 'chamber' in the scenario of a car engine's lubrication & cooling system is not spherical, but again the same principles apply throughout different galleries with drillings to interconnect them. 

The result of this is that when you loose pressure from one part of the system - then you loose pressure from all of it.  For instance if your big end bearings are shot, then the system will loose pressure everywhere else, even though it is most obvious to think immediately of the main bearings.  The 'physics' is apparent (and even measured) at the end of a very long and very small bore pipe to your oil pressure gauge.  

Similarly if part of the chamber's seal is lost, in this scenario we are talking about the gap around a split pin versus a mill pin, or around the end cap of a rocker shaft - then again the pressure in the whole pressure system will be reduced.   The question then is by how much.?  This simply comes down to ; what is the difference in the gap around a well-fitting split pin and that of a split dowel.  or in a latter example between one cap or washer and the next ?  

As has been suggested, the losses around a spilt pin -v- a dowel is negligible  in comparison with the many designed / controlled flow out of the plain bearings (which are there to provide splash lubrication and dissipate heat from the pistons n' cylinder bores and camshaft),  and those of the rocker shaft (which are there to lubricate and dissipate heat from the valve gear) ..the 'gap' around each of and every one of these are many times greater

Pete.

 

Edited by Bfg
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While we are on inspecting engine parts.....these are the original TR2 steel rocker pedestals from the engine currently in work.

can you spot the problem?

I thought the move to aluminium pedestals was to keep valve clearances all the same.  Nothing about likely to crack.

Cheers

Peter W

836CBF49-4CA6-46AA-9465-CF0510E878F9.jpeg

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1 hour ago, stillp said:

Pete, you're ignoring the effect of flow through the various restrictions. There will be  a lower pressure downstream of any restriction, otherwise there couldn't be any flow!

Pete

Yeah

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1 hour ago, stillp said:

Pete, you're ignoring the effect of flow through the various restrictions. There will be  a lower pressure downstream of any restriction, otherwise there couldn't be any flow!

Pete

The restrictions will control the ' flow ',  but the pressure in the system is very much the same.  Think about a sprinkler system across a field, if your appraisal were correct then you'd see the first hole shooting water furthest, and then with each next hole - the distance the jet of water carried would be less and less. The drop in pressure downstream could be measured as a linear distance the water carried. But that is not the case.

images?q=tbn:ANd9GcTR3OrsIfyaa4Rh1FsQlt8

The engine's pump is designed to provide xx psi pressure throughout the whole system ..when the assembly tolerances are correct.

Why then the different size drillings and galleries.?  This comes down to the amount of flow through the many clearances and jets ..and the size of galleries needed to deliver that amount of oil *.    Each clearance / jet is designed to allow a certain amount of oil flow passed them, and when fit is poor or wear is excessive - then the flow increases and the oil pressure drops.  It doesn't matter where that occurs in the system.  If you were to start the engine without the rocker shaft's end cap on you'd still see the oil pressure gauge reads much less.

* of course practicalities of the size of very long drillings and other production issues, such as aligning oil ways where assemblies are bolted together, also come into play.

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Good morning!

I had a look on the sketch of the engine at the workshop manual.

The oil for the rocker shaft has to pass a small drill to the rear camshaft bearing,

some of that oil flows out there back in the engine, another part of it flows up to the rocker shaft.

So the volume of oil is limited while the rockers on the shaft are very unsealed.

It's up to you to get to your own conclusion, I think it's low pressure in the rocker shaft and doesn't matter what pin you fit.

I fit mills pins as original, conviniece is not the matter to me.

Ciao, Marco

Edited by Z320
added: to me
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Looks like we have drifted from the original topic, just a bit:)....

(Static) Pressure can only be “the same” in a system if there is no flow. Even then the static pressure varies with elevation, think of a water tower.

Once there is flow, the pressure drops downstream the line, due to friction losses of the moving liquid (or gas).

This has little to do with Bernoulli (static pressure + dynamic pressure + head = constant) because its not about conversion of static to dynamic or vice versa but it’s just pressure loss by friction.

Cheers,

Waldi

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Pete / Waldi,  I do not disagree with your argument that there is friction in the system &/or even that static pressure varies with elevation.  However my reply sought only to answer the OP's question ..with the hope of not  getting sidetracked and bogged-down in matters of friction, back pressure at the point of restriction, number and tightness of bends in the route, how things vary with viscosity at different temperatures, lift height, etc. etc.  etc  ..in a rather crude engine - where the total routing distances are all within a few feet (a single metre) of the pump and the lift height is half that figure, and the pressure the pump supplies is in great surplus to oil flow ..which is why there is a steady pressure (albeit relative to engine revs) in the system ..as recorded by the oil pressure gauge. 

When you consider oil @ 60psi  (let's assume a sp.gravity of 0.80) has the equivalent head of about 173 feet !  ..you can see why I was not concerned about these things. They do not alter the conclusion I offered.  

On 12/13/2019 at 11:08 AM, Bfg said:

. . . if part of the chamber's seal is lost, in this scenario we are talking about the gap around a split pin versus a mill pin, or around the end cap of a rocker shaft - then again the pressure in the whole pressure system will be reduced.  The question then is by how much.?  This simply comes down to ; what is the difference in the gap around a well-fitting split pin and that of a split dowel,  or in a latter example between one cap or washer and the next ?  

As has been suggested, the losses around a split pin -v- a dowel is negligible  in comparison with the many designed / controlled flow out of the plain bearings (which are there to provide splash lubrication and dissipate heat from the pistons n' cylinder bores and camshaft),  and those of the rocker shaft (which are there to lubricate and dissipate heat from the valve gear) ..the 'gap' around each of and every one of these are many times greater

I leave it there. 

 

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Good day All, back to my original approach for advice!

I have succeeded in removing the rocker shaft end caps and I have achieved fitting of split pins [1/8" x 1 1/2"]  by rubbing them down with emery paper to be a snug fit with no movement. I thought the front double coil end cap spring had broken. This is not the case, but I did discover that these springs are out of stock everywhere and Moss currently have not found a supplier.  TR6 springs are smaller in diameter, but having purchased a couple of TR6 items, I succeeded in drilling the TR6 washer out to 16mm plus a bit of filing to slide on to the TR4 shaft. Pic attached to show the remarkable difference in size, the TR4 item being the larger.

 Now I have the new rocker shaft put together using spacer kit instead of springs, my son & I have been assessing where the shims supplied with the kit should go before the rocker gear is bolted back on. At the site of the loud clicking noise pre-disassembly - the front of the engine - #1 rocker looks to be slightly too far to the left, but the double coil spring [the proper TR4 one] prevents appropriate adjustment.  Question - can I leave the double spring washer off at the front and use shims instead?  Shot attached showing how firmly the washer is compressed with #1 pedestal on the stud.

Best wishes     Willie

Double spring washers.JPG

4. Front end cap & spring.JPG

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Thanks Tom. The reason for asking is that on my engine the double spring washer is firmly compressed yet the rocker arm needs to move slightly into the space taken up by said double coil spring! Shims are 0.010"; double spring is at least 0.25" in relaxed state I am hoping someone has experience of leaving the spring off and using a washer or shim instead.

Willie

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Maybe the spring washer has an additional function: to compensate for differences in thermal expansion between head and rocker shaft. It will be minimal, less than 1mm, but if thermal movements are restrained high stresses are the result.

For “alignment” of the rockers to the valve stems, check that the valve stems tips are not bearing on worn and unworn area of the rocker tips, if there is some wear on them. It will make proper valve clearance setting impossible.

Waldi

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What an interesting conundrum. 

As far as I'm aware the springs are there simply to stop the rocker arm rattling along the shaft.  And in production, such springs are very much quicker to fit than individually shimming each arm to fit exactly where you'd like it to be,  ie., (very approximately) centrally placed over the valve stem. 

If the head was in aluminium then I would concur with Waldi's suggestion, but I understand the thermal expansion of all the iron & steel bits (at this scale) would be close to proportional.  

I've just been out to the garage to look at my own engine's rocker shaft,  but it doesn't help me understand how yours is like this ..as the issue is in needing a spacer to move the rocker arm away from the pedestal.  BTW., my rocker shaft's front spring is also noticeably more tightly compressed than the rear one ..but its arm is over the valve.

10 hours ago, Willie said:

Question - can I leave the double spring washer off at the front and use shims instead? 

If it were mine, I'd just move the spring and fit it between the pedestal and the arm ..and get the rocker better centered over the valve stem  ..as long as that push-rod cannot possibly rub against its tube.

I'll sleep on it, to see if anything occurs,  but for the time being I really can't see why that would be in any way detrimental to the operation or longevity

Pete. 

 

Edited by Bfg
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Hi all - can you not grind some metal off the bottom face of the cap to give you more clearance  -there looks to be enough metal to do this before hitting the split pin hole.

Alternatively, if the caps are the same both ends, have you tried swapping them around to see if that makes any difference.

Cheers

Rich

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Thanks again for those recent posts.  The reason why I examined the rocker gear in the first place was to find the cause of a loud clicking which is louder than the tappet noise and quite obviously emanating from top front of the engine. The timing chain was renewed earlier this year, to no avail.  The only questionable part I found was that the front double coil spring looked to have lost its spring tension. Whilst still in situ, I thought I would find it to have broken but it hadn't. As mentioned earlier, these springs are currently unavailable from all the major suppliers, hence me looking at alternatives. One option might be to add a thin 5/8 washer with the weak spring and put it next to #8 rocker. I can't imagine that will move the noise to the rear!!  The #1 rocker is covering the valve stem, but is obviously biased to the side nearest #1 pedestal. I would like to have it better aligned, hence yesterday's question about shims.

Willie

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On 12/21/2019 at 12:32 PM, Willie said:

Good day All, back to my original approach for advice!

I have succeeded in removing the rocker shaft end caps and I have achieved fitting of split pins [1/8" x 1 1/2"]  by rubbing them down with emery paper to be a snug fit with no movement. I thought the front double coil end cap spring had broken. This is not the case, but I did discover that these springs are out of stock everywhere and Moss currently have not found a supplier.  TR6 springs are smaller in diameter, but having purchased a couple of TR6 items, I succeeded in drilling the TR6 washer out to 16mm plus a bit of filing to slide on to the TR4 shaft. Pic attached to show the remarkable difference in size, the TR4 item being the larger.

 Now I have the new rocker shaft put together using spacer kit instead of springs, my son & I have been assessing where the shims supplied with the kit should go before the rocker gear is bolted back on. At the site of the loud clicking noise pre-disassembly - the front of the engine - #1 rocker looks to be slightly too far to the left, but the double coil spring [the proper TR4 one] prevents appropriate adjustment.  Question - can I leave the double spring washer off at the front and use shims instead?  Shot attached showing how firmly the washer is compressed with #1 pedestal on the stud.

Best wishes     Willie

Double spring washers.JPG

4. Front end cap & spring.JPGHi Willie, has that front rocker been running in that position for thousands of miles, if so check it hasn't worn a step on the surface which would result in excessive valve clearance and your rattle. 

Chris

 

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To end this topic, here are shots of the final springs layout.  Good rear double spring relocated to front.  Drilled out TR6 double spring located on front. I am awaiting a further supply of 0.010" shims to complete the alignment of all rockers. As I am renewing all rockers, I am going to test all of them in different positions tomorrow to see if I can improve overall alignments. I will report further if anything of interest emerges. There is evidence of tempering on the arms suggesting heat to achieve final shape.The findings might be useful!! Sorry all the labels are upside down!

Willie

8a. Opened out TR6 spring on rear.JPG

8b. TR4 spring relocated from rear to front.JPG

9a. Modified TR6 spring on rear of shaft.JPG

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