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In "Triumph Tuning " by Stan Shenton it is stated that ""The Thackeray spring washers should be replaced with hardened steel distance pieces. It is impossible to lay down a set thickness for these since manufacturing tolerances cause variations in each individual engine. What must be watched is that the rocker,when set up with its spacers and the oil feed dome nut tightened, has its pin directly in line with the centre of the valve stem. This can be checked without the need for assembling the rocker box on the head, for when it is correctly positioned the rocker adjuster will be directly in line with the rocker box 1/4" mounting stud."
"There is no need to allow rocker end float on the shaft because ideally there should be no end float but the rocker should be completely free. Special experiments have shown that when an engine warms up, the rocker end float increases so there is no danger of any locking up ".
Interesting stuff, though much of which has already been said. Both my Triumph road bikes have the original Thackeray set up, but the spacer idea will be considered for my T140 race project. Also, checking should be also done with the rocker boxes assembled to ensure correct pushrod length,so that the aduster is smack on the centre of the valve stem at half lift.

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This is all good food for thought.
Mr. NickL has me wondering where I can find 99999 more 0.00009 improvements to make a full 1%.

I KNOW THEY ARE IN THERE! I'll take anything I can get.

Smooth hand grips! Less drag, and they HAVE to be worth a 0.00009th.
99998 more to go!

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Yep, and drill holes in the soles of your boots, cut your finger nails an d toenails to the quick and leave your socks and jocks off!

Last edited by Triless; 01/20/16 2:05 am. Reason: spelling
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Then the lid, and goggles have to go as well.

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Struth! He's not wearing gloves! Thats taking it a bit too far!

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I made a slight straight groove using a Dremel tool in the rocker shafts and also rearranged the Thackeray and thrust washers on three Triumph 650's. Lacking sophisticated laboratory testing equipment to test the results I unscrewed a rocker inspection cap and it appeared to be "oiler" inside...

On the Thackery waskers; does every little bit help for performance? Maybe, maybe not...I told my rider improvements had been made for more power...In reality I did nothing mechanical but the bike went faster...










79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
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my Beesa motor has a mix of thackeray washers and steel spacers. The steel spacers are much much easier to assemble. Stopping the thackeray washers from dropping into the notches of an A65 rocker spindle is a real PITA.


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Originally Posted by Hillbilly bike
In reality I did nothing mechanical but the bike went faster...


Perception is 99% reality.


Cheers,

Steve


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Originally Posted by Hillbilly bike
I did nothing mechanical but the bike went faster...


I'm gonna try that!


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Now THAT could be the BritBike "T" shirt motto.

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It's the same phenomena as the placebo effect. That sugar pills cures lots of things.....

And sole reason there are thousands of charlatans selling snake oil to the gullible. It does work, scientifically, about 10-25% of the time. Magic! Double blind studies prove it with each and every study. They never bother to try to explain it, though. But they do account for it.

Physicians don't underestimate the power of the mind to heal. They're never going to let on that they make use of the placebo effect every day.

Sorry if I've blown it for anyone. But, it's the truth.

And loud pipes make a bike faster. For real!

Cheers,

Bill


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Quote
I told my rider improvements had been made for more power...


You probably get more gain from skipping the jelly doughnuts from breakfast than solid rocker spacers.

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Jelly doughnut residue provides a slick coating on the imbibed that reduces drag/wind resistance.

another 0.0009%. only 0.00007 more to go!!!


Placebo effect:
Fedoras, and heavy frame glasses are so totally "in" this year.

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The supposed benefit is to the cams and followers, rather than net power at the rear wheel.


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i've never looked at them as anything other than a means of reducing friction in the valve train. they very clearly do this, as the force needed to move the rockers with your hands when using thackery washers is quite noticeable, and is just as noticeably gone with the spacers installed.

but it's only an ounce or two of force. does that reduction of an ounce or two of force at zero rpm translate into a reduction of more than an ounce or two at high rpm? i don't know. does the friction increase with speed?

if the resistance to motion due to friction increases with rpm, then they're worthwhile. if there's still only an ounce or two of additional force from the thackery washers at 7000 rpm, then no.


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well, my wife says i can't leave well enough alone, and she's mostly right. so i've been thinking about these little spacers, and wondering about just exactly how much force it really does take to move a rocker arm with a thackery washer on it.

like everybody else, i have bits and pieces of stuff lying around to mess with.

so here's some old rocker box i have with thackery washers in it, installed the way i mostly see them, against the rocker arm, with the flat washer on the other side against the rocker box:

[Linked Image]

notice how the washer is digging into the oil cutout on the rocker arm:

[Linked Image]

and here's another one, with the steel spacers installed, done before i got it. whoever he was, he also ground the casting flash away a little bit, but didn't polish anything:

[Linked Image]

he installed the spacer against the rocker arm, in the same spot as the thackery washers in the other rocker box. these rockers don't have the little cutout:

[Linked Image]

anyway, i lubed everything up as well as could through the hollow rocker shaft and from the outside with PB Blaster:

[Linked Image]

[Linked Image]

and then stuck an old pesola spring scale on them to see how much tension it would take to make the rockers of each type rock. i used to use the scale to weigh squirrels, but it works okay for rocker arms too:

[Linked Image]

[Linked Image]

in a dozen or so tries, the rocker arms with the thackery washers always took a minimum of 350 grams to start any kind of movement, and never swung fully at under 450 grams of tension. sometimes it took as much as 600 grams to make them move.

[Linked Image]

in contrast, the rocker arms with the spacers would fall under their own weight, either way, whenever i twisted the rocker box. i never bothered to hook up the spring scale to them at all.

so here are some thoughts and observations:

-- neither of the rocker shafts had any looseness or any apparent binding in their travel.

-- i didn't take anything apart to inspect the insides, but the box with the thackery washers didn't feel like it took any more or less force to move than they always do.

-- according to what i've learned about friction, sliding friction doesn't increase with velocity, so the 300-450 gram force needed to start the rocker moving at the top and bottom of its travel won't increase with rpm.

-- this only measured static friction, the force necessary to start the rocker rocking. as soon as it started to move, it moved too quickly for me to see what the spring scale might have been showing. so i don't know what the resistance of the moving parts might have been, after they started moving.

-- i didn't try to see whether it's harder to move a rocker from the absolute end of its travel than it might be from a little less than that. so in hindsight it's possible that the rockers might take less force to move if you start them closer to where they actually sit on top of the valve at zero lift. forgot to control for that . . .

-- this was done with cold parts, not warmed up, with no oil pressure inside (such as it is in a triumph), and with absolutely nothing else held constant. smile

-- the boxes are different kinds-- one is from a later head (hollowed out for the two-piece head bolts, and drilled for dowels), with the little oil cutout. the other is the earlier style, not milled out inside, and has the drilled rocker arms, which you can see from the holes in the pushrod ball ends.

and here are the guilty parts in question:

[Linked Image]

so it's clear that some friction exists, and that the friction is measurable at the point where the rocker arms stop moving, reverse direction, and start moving again. once they're moving, the force needed to keep them moving is way less.

but is this significant? i don't know. i suspect not, because with valve springs that might be pressing on these rocker shafts with way over 100 pounds of force, each, a few hundred grams of friction doesn't seem like a lot. but i'm not an engineer.

i have bikes with them, and bikes without them. i haven't ever noticed a difference, but i am not particularly sensitive and haven't pushed rpms to the limits, either.


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Boy, I wish I had that kind of time on my hands! grin

Interestingly, the box with the spring washer has the end of the spring in the machined divot which diverts oil flow away from the valve tips. The box with the spacers has no machined divots (not good for valve tips), but it looks like the ball pins are drilled (good for the push rods). Pictures aren't terribly clear, but it sure looks like in both cases the adjusting pins have taken a hammering.

When I rebuilt my top-end a few years ago, I took a look at the face of my adjuster pins with a powerful magnifier. They looked like the pock-marked far side of the moon! I put new adjusters in and did the thrust/thackery washer mod advocated on here by others. Because, as we all know the top end doesn't need much oil, but it sure needs it in the right places!

Steve


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Originally Posted by JubeePrince
Boy, I wish I had that kind of time on my hands! grin


it's nasty snowing and my new job hasn't started yet.

it better soon, though, my bank account is headed for the infra red


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so why use the springs? Quieter? You'd think at some point in time during 50+ years of production some guy at Triumph Engineering Company probably uttered...."hey what if we just use a spacer instead of that spring"

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Strictly speaking you should machine the solid spacers to fit each of the positions with a suitable running clearance as there is some variation in the gap due to machining tolerances etc.
The Thackeray spring effectively compensates for differences in clearance and so is a cheap pretty effective way of keeping the rocker arms in position.
HTH

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Originally Posted by jurbanec
so why use the springs? Quieter? You'd think at some point in time during 50+ years of production some guy at Triumph Engineering Company probably uttered...."hey what if we just use a spacer instead of that spring"


They did.

But they didn't want to mess about with feelers and alternative shim thicknesses on the assembly line.


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Kevin...400 grams....And when the rocker is trying to compress a 180 pound spring at 7000 rpm...Does the 400 grams,a bit less than one pound, really matter? Does the friction of the Thackeray washer help to "dampen" harmonics when the valve is closing? You need to do a before an after on a Spintron machine to make a real comparison....
I believe racers use spacer to eliminate a potential failure of spring .......


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
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i really don't think the sliding friction of the thackery washers matters, for exactly the reason you point out -- the actual friction at speed is no more than at idle. and i don't think 450 grams could really provide significant spring damping, but maybe it could? certainly friction dampers in suspension systems were obsolete as soon as anybody had anything else.

and maybe they make less noise, but i run 0.010 valve clearances in the bike i have them in, so i probably couldn't hear them anyway.

the spring washers are certainly more fragile, but then i've never had one break. if you're running later rockers, the spacers do prevent you from putting a leaky spring washer against the cutout, but that's not a dissassembly i do very often.

so i guess i can provide a great big cosmic: don't know . . .


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Originally Posted by kevin

so i guess i can provide a great big cosmic: don't know . . .



Hey Kevin -

Certainly not for lack of trying, thanks.....and good luck with the new job!

Cheers,

Steve


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I'm about to make my own spacers. What would be a good running clearance between the spacer and rocker arm?


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