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Curiouser and curiouser.

I marked the flywheels at positions I to VIII as per the attached pretty pitcha.

They measured

drive dide
I - 1.1910"
II - 1.1905"
III - 1.1910"
IV - 1.1913"
V - 1.1912"
VI - 1.1910"
VII - 1.1904"
VIII - 1.1907"

timing side
I - 1.1874"
II - 1.1874"
III - 1.1875"
IV - 1.1876
V - 1.1881"
VI - 1.1876"
VII - 1.1874"
VIII - 1.1882"



The collet has gone the way of cunning plans which didn't quite work, to be replaced by the boring old 4-jaw chuck.
Despite that, there is 0.04mm difference on the inner rim of the timing side flywheel Taking the crankpin as 12 o'clock, 12 and 6 read the same, but 3 and 9 are 0.04mm higher.

The drive side flywheel is next.

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Originally Posted by Shane in Oz
........I marked the flywheels at positions I to VIII as per the attached.........They measured.......
I must not be explaining very well. The measuring I'm proposing is the material thickness immediately surrounding the taper the crankpin seats into.
The problem is just how to actually do it. I tried a 0-1 mike and while I could get it in through the tapered bore, it was too wide to measure close in.
Hmmmmm.......Frustrating......

Maybe someone has a better idea?

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Originally Posted by Stuart Kirk
Originally Posted by Shane in Oz
........I marked the flywheels at positions I to VIII as per the attached.........They measured.......
I must not be explaining very well. The measuring I'm proposing is the material thickness immediately surrounding the taper the crankpin seats into.
The problem is just how to actually do it. I tried a 0-1 mike and while I could get it in through the tapered bore, it was too wide to measure close in.
Hmmmmm.......Frustrating......

Maybe someone has a better idea?
You explained it fine, but I can't figure out how to measure it. either. A 0-1" micrometer won't fit over the flywheel rim or through the crankpin hole, and I don't have the gage blocks required to be a player in The Tooling Wars[TM].

The best I can figure at this stage is to
  • skim the inner face of the flywheel rim,
  • clamp the flywheel to the milling table on 1-2-3 blocks
  • indicate the mainshaft dead vertical
  • indicate the clamping face for the crankpin nut.

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Originally Posted by Shane in Oz
A 0-1" micrometer won't fit over the flywheel rim or through the crankpin hole,
But, a hub micrometer will fit into the hole. As the photograph shows, the measuring faces are just 5/8" from the back so it can easily fit through the hole to make the measurements.

[Linked Image]

The 1/4" gap between the anvils and body means it can not only make measurements near the inside edge of the area just outside the hole, it can measure that far further into the area.

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Originally Posted by Magnetoman
But, a hub micrometer will fit into the hole. As the photograph shows, the measuring faces are just 5/8" from the back so it can easily fit through the hole to make the measurements.

[Linked Image]
That looks more like 3/4" than 5/8". and the non-Goldie crankpin threads are only 3/4".

Anyway, I am obviously way behind in The Tooling Wars[TM] frown

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Originally Posted by Shane in Oz
That looks more like 3/4" than 5/8". and the non-Goldie crankpin threads are only 3/4".
Sorry, I thought from superficially glancing at something earlier in this thread that they were 7/8". The 5/8" in my post is the distance from the frame to the center of the anvil. Unfortunately, if you look really, really close at the photograph you'll see that the width of the frame at the business end of this micrometer is 0.785" so it wouldn't fit through a 3/4" hole. Unless the depth of the hole was thin enough that the micrometer could be "hooked" through it, in which case it would (barely) fit.

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Hi All,
Working the other way around I have a micrometer set as in the pic that has interchangeable anvils
I think one of these could reach in from the rim of the flywheel to measure the points around the crankpin hole,
A long time ago I had a similar issue in that when bolted tight the flywheels would "take a set" and close in opposite the pin
I eventually found a low area on one flywheel where the shoulder of the pin sits against
Way back then I did not have much in the line of machine tools so I found a piece of round bar to fit the flywheel (parallel pin on Ariel 500)
and a cast iron gear with 1" bore that sat in the flywheel recess, Then it was a case of adding some grinding paste and lapping the flywheel face until I had an even contact face
It probably took a week of lunch hours to do the lapping !!! anyway it worked and the Ariel has been running great since 1986!!

Earlier in this thread I read that there was a burr on the flywheel taper where the edge of the crankpin taper had dug into the flywheel
I would carefully scrape away the burr and grind a very small radius on the thread end of the crankpin taper so as it will not "dig in" as the pin is tightened

John

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Originally Posted by chaterlea25
I have a micrometer set as in the pic that has interchangeable anvils
I think one of these could reach in from the rim of the flywheel to measure the points around the crankpin hole,
I hadn't thought about that approach - but there are lots of nifty things available that I didn't know about.

There's even a 0 - 4" Browne and Sharpe on the local eBay at a very reasonable price.


p.s. I just measured the crankpin holes. They're 1" diameter, so Magnetoman's hub micrometer approach would also work.

Last edited by Shane in Oz; 11/15/22 10:32 pm. Reason: Added p.s.
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Originally Posted by Magnetoman
Originally Posted by Shane in Oz
That looks more like 3/4" than 5/8". and the non-Goldie crankpin threads are only 3/4".
......the width of the frame at the business end of this micrometer is 0.785" so it wouldn't fit through a 3/4" hole. ......
Actually, the small end of that taper is bigger than either thread so that cool hub mike should easily fit through.
Originally Posted by chaterlea25
....... I have a micrometer set as in the pic that has interchangeable anvils
I think one of these could reach in from the rim of the flywheel to measure the points around the crankpin hole,
..........
Another good possibility and a wonderful opportunity to do some tooling up.

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Originally Posted by Shane in Oz
There's even a 0 - 4" Browne and Sharpe on the local eBay at a very reasonable price.
I have a micrometer set like that, except mine covers the range 6"–12". The frames of these interchangeable anvil micrometers are sized for the radius of the largest diameter they're intended to measure, so mine can reach a maximum depth of 6". A BSA flywheel is 8", so a micrometer only has to reach 4" (less the radius of the spindle). However, I didn't propose it because the minimum thickness the interchangeable anvils in mine allow for is 6". A 0–4" micrometer set works down to 0", which is good, but the frame only reaches to a depth of 2", which isn't. What would be needed is a 0–8" set, but an entire 30 sec. spent with google failed to turn up such a beast.

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Originally Posted by Magnetoman
I have a micrometer set like that....covers the range 6"–12". ......I didn't propose it because the minimum thickness the interchangeable anvils in mine allow for is 6".......
It would be fiddly but measurements could be made by using the standards that come with those type of mikes to extend the anvil to reach down to the size needed. It would be less fiddly if a collar or sleeve was made to hold the standard in position.

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Originally Posted by Magnetoman
Originally Posted by Shane in Oz
There's even a 0 - 4" Browne and Sharpe on the local eBay at a very reasonable price.
I have a micrometer set like that, except m A 0–4" micrometer set works down to 0", which is good, but the frame only reaches to a depth of 2", which isn't.
Another beautiful hypothesis slain by an ugly fact frown


Originally Posted by Stuart Kirk
It would be fiddly but measurements could be made by using the standards that come with those type of mikes to extend the anvil to reach down to the size needed. It would be less fiddly if a collar or sleeve was made to hold the standard in position.
That's a possibility. Another might be to use a 1-2-3 block. I'll have a look at that.
Actually, are we all overthinking things? The actual thickness doesn't really matter, just whether the surfaces are parallel.

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Originally Posted by Stuart Kirk
It would be fiddly but ...
There are other approaches, some more fiddly than others, but the problem is when you need to measure to no worse than ~0.0002".

I could ring 6" worth of gauge blocks to use with the 6" anvil in my 6"–12" micrometer set but, in addition to the fiddly business of keeping it all from crashing down like a house of cards, the spatial resolution of the measurement would be limited by the size of the blocks. A 6" micrometer standard would increase the resolution, but it still would be fiddly.

The flywheel could be balanced on gauge blocks that are precise to micro-inches, the distance from the upper surface to the surface plate measured with a depth micrometer, and the two subtracted to find the thickness. My depth micrometer has a resolution of 50 micro-inches. So far, so good, except the base of the depth micrometer would span a significant area of both sides of the hole, severely limiting its usefulness.

Or, a hub micrometer...

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Originally Posted by Shane in Oz
The actual thickness doesn't really matter, just whether the surfaces are parallel.
That's true, but it just exchanges one problem for another. It doesn't matter too much if the surfaces are precisely parallel with the outer flange, it matters if they are parallel with each other. One way to determine that is to use a micrometer around the circumference. If the readings are identical, they're parallel. The other way would be to directly measure if they are parallel. But, um, how do you plan to do that? I should ask, how do you plan to do that with less effort and expense than measuring with a micrometer?

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Originally Posted by Magnetoman
it just exchanges one problem for another. It doesn't matter too much if the surfaces are precisely parallel with the outer flange, it matters if they are parallel with each other.
Come to think of it, I think this started off as checking that the crankpin nut seating surface is perpendicular to the crankpin (and hopefully that is parallel to the mainshaft)
That can probably be done by ensuring that the mainshaft is parallel to the mill spindle in X and Y and sweeping the seating surface with a dial indicator on an arm mounted in a collet in the spindle.

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This is the plan, or at least one iteration of it.

The flywheel is clamped to the milling table on 1-2-3 blocks, and the mainshaft indicated dead vertical with the centring indicator.

In theory, the crankpin is supposed to be parallel to the mainshaft, so if I skim the clamping surface with a fly cutter, that surface should be perpendicular to the crankpin and its tapered hole. That should avoid the nut trying to tilt the crankpin a la Magnetoman's diagram.


As they say, measure twice and cut once, so I'll give it another day or so before actually removing any metal to allow time for somebody to point out any flaws.

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I think using either of the shafts would be a mistake. What matters is the crankpin, which is what I would use as the datum.

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Originally Posted by Shane in Oz
........As they say, measure twice and cut once........
Or as I heard someone once say... " I cut it twice and it's still too short."

Originally Posted by Shane in Oz
............. so I'll give it another day or so before actually removing any metal to allow time for somebody to point out any flaws.
I'm afraid I'm going to be guilty of being a total party pooper buzzkill but here goes.

1. Suggest placing the clamping pressure directly over the supporting blocks to avoid distortion of the part to be cut.

2. Don't rely too heavily on that Blake type coaxial indicator.

3. Spin the flywheel between centers and map the flywheel outer rim runout. (Repair centers as needed first.)

4. Then attach a dial indicator to the tool post and use it to sweep and map the face the nut tightens up against both radially and rotationally. Radial variation is more important for the problem you're solving.

5. Compare your results and then decide how you might want to remove metal. Once it's removed, it's difficult to replace.

To a hammer, every problem looks like a nail. To a man with a mill or a lathe? Well, I think we know that answer.

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Originally Posted by Magnetoman
I think using either of the shafts would be a mistake. What matters is the crankpin, which is what I would use as the datum.
Valid point. That's why I suggested making a dummy crankpin to get a read on how parallel the shaft is to the pin when it's seated in the taper.

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Crikey, you blokes are spoil sports.

You're right, but still spoil sports.

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Hi All,
Quote
Don't rely too heavily on that Blake type coaxial indicator.

Totally agree, a flaw in their design is that they rely on the mill collet being 100% accutate
a tenth or less run out at the collet is multiplied by the length of the probe ( I will leave MM to do the math)

I dug myself into a hole relying one mad mad mad
I resisted the temptation to bin it as I found it useful as a static indicator to reach down into cylindrical holes to see if they are vertical / parallel
to the mill spindle. ( I found a pair of AJS twin cylinders that were bored out of square to the cylinder bases using it)

John

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Originally Posted by Shane in Oz
Crikey, you blokes are spoil sports........
I hear you, but it could be worse. I have had that sinking feeling in the pit of my gut when I realize I have removed metal where I shouldn't have.

BTW, all your photos of the crankshaft parts so far have looked pretty decent ie not that terribly beaten up. Why has it been so resistant to truing? I wonder if the crankpin could be the trouble. A relatively simple diagnostic exercise could be to trial assemble and true it with the pin 180 degrees from its normal spot. The key would have to be left out but if the problem reversed, ie the pinch problem became a spread problem, the pin could be the culprit.

Last edited by Stuart Kirk; 11/17/22 4:55 am. Reason: Proof read
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Originally Posted by Stuart Kirk
[all your photos of the crankshaft parts so far have looked pretty decent ie not that terribly beaten up.
It didn't go out of true until the final torque stages on the crankpins, so it may well have been the ridges at the outer end of the tapers. There are slight ridges on the clamping faces where the crankpin nuts have pushed some metal out as well. Goodness only knows how long the spanner was that Bruce Banner used to tighten them.

Originally Posted by Stuart Kirk
Why has it has been so resistant to truing? I wonder if the crankpin could be the trouble. A relatively simple diagnostic exercise could be to trial assemble and true it with the pin 180 degrees from its normal spot. The key would have to be left out but if the problem reversed, ie the pinch problem became a spread problem, the pin could be the culprit.
It may even be worth a trial assembly now that I've deburred the outer ends of the tapers, but I should check the tapers with bearing blue first, and look at cleaning up the clamping faces as well.

We have farm work to do for the next couple of days, so probably no progress reports until next week.

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HI Shane
Above I suggested to grind the sharp edge at the end of the taper into a small radius
Doing this will aid the pin seating properly
You also need to look at how far the shoulder of the pin sits away from the flywheel before the nuts are tightened
The shoulder has to be up against the flywheel once the nuts are fully tight
If the pin shoulder is too near the flywheel before tightening then the assembly will not be secure on the tapers (enlarged taper in flywheel)

John

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Originally Posted by chaterlea25
.......If the pin shoulder is too near the flywheel before tightening then the assembly will not be secure on the tapers (enlarged taper in flywheel).....

Just for sake of discussion, is there a reasonable way to correct such a problem without getting new parts? Two possibilities come to mind, not that I have tried, or have ever seriously considered either of them.

1. Removing metal from the inside face the pin seats against.

2. Remove metal from the ledge on the pin.

This would of course make the assembled crank narrower and would probably need special shimming. The rod might drag on the crank as well.

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