Cold start rattle

[oliver90owner]

Kennatt,

They must have fitted a different pressure switch to prevent start up. I would be surprised if the normal oil pressure switch would support ignition loads for long (usually a 2W lamp?) and the oil warning switch allows current with low pressure which is interrupted as the pressure rises above the switch threshold.

At work (a long time ago) the 3000HP installations utilised high pressure oil pumps for initial lubrication before start up. The total weight of the driven rotating (~12-15rpm) mass was likely over 300 tonnes. The HP pumps lubricated the motor and driven load items only before and during start up before lube was taken care of by low power/pressure oil pumps.

Earlier (1960s) 1500HP installations did not have that refinement but I cannot recall any trunnion bearing failures on anything except the very much older 500HP installations (from the mid 1920s to the 50s). All of these older machines were gravity oiled by oiling rings and were not lubricated (I think) before ‘normal’ starting although the rings should have been checked for operation after starting. Well, they were sometimes

[niftyrodman]

Thanks Kennatt and Oliver. First, Oliver I read you,and do understand your point and of course, nothing is off the table. Impossible to measure mains, without the crank out so that would be a last resort. And Kennatt, I understand your confusion. The man in the shop that did the work assures me that if for example the big end bearings are now ,020 under that he can get a set of bearings .020 under +.002 so if the clearance is say .004 that will bring the clearance back to .002, which i think is all there is in this problem. I find it as interesting as it is nuisance. However my electronic vernier will tell me the truth. I also liked the innovative oil pressure ignition switch, and when you think about it, if the bearings aren't noisy, they cant be doing damage.

[philthehill]

Your electronic vernier will only tell the truth if has been calibrated or used to measure a test piece and the electronic vernier shows the same measurement as the test piece is in length/dia.

When checking the accuracy of my electronic vernier I use the test pieces from Moore and Wright micrometers with all items at room temperature (around 20/22 degrees centigrade)

[kennatt]

Probably fitted a relay,fed from oil switch.Its actually not a bad idea when you think about it, certainly guarantees oil pressure to bearings before it fires up, only issue could be flooding with choke out .

[oliver90owner]

Well, I have both digital electronic calipers and analogue vernier ones, but not seen any electronic vernier calipers!

Even so, I would not rely on calipers of either type for really precise absolute measurement - I would be using a micrometer, checked against standard gauge blocks to determine any error. The only time I rely on unchecked/uncalibrated measuring kit would be for checking crankpins for ovality, which is a simple comparative check.

[philthehill]

I am sure that the term electronic vernier is being used as a generic term and cover those measuring gauges that are not mechanical.

In my post above I consider the term electronic vernier to be a generic term.

It has to be remembered that not everyone uses the correct technical terms for such items or even knows what the various terms mean.

Below is a vernier gauge being used by me to measure the lift on a camshaft. It is battery powered and has electronics inside the body of the gauge so can be considered an electronic vernier.

100_2648.JPG (1.19 MiB) Viewed 2123 times

I have a full set of micrometers ranging from 0" - 1" to 5" - 6". They get little use because the electronic vernier is calibrated and so easy to use.
Phil

[kevin s]

I seem to remember some triumphs for the US market came from the factory with some sort of oil pressre switch in the ignition to reduce warranty costs.

[niftyrodman]

Thanks Dr Phil. Of course the vernier is electronic, as it has a battery, why do people split hairs? If I know the diameter of the crank when it was new, and I measure it according to that and deduct whatever has come off it from being ground I will be somewhere pretty close. The vernier I have, is not the most expensive model out there but will measure down to 0005. Anyway if I bolt the rod up aside, and can measure that, the temperature doesn't matter, as it is that relativity Im after. Am I right in saying these motors are oversquare,? and if so, does that make clearances at the big end bearings more critical.?

[oliver90owner]

It has to be remembered that not everyone uses the correct technical terms for such items or even knows what the various terms mean.

You are clearly right on that point! A Hoover is a vacuum cleaner but not all vacuum cleaners are Hoovers. Cells and batteries, even glue and heat sink compound (on another current thread!).

I never rely on my Mitutoyo digital calipers when turning - OK to close to size but then I use either my digital micrometer or, more likely one of my vernier micrometers (these will indicate to one tenth of a thou). You may well have a caliper capable of measuring 150mm, but it won’t measure a 150mm crank, for sure. Do remember the anvils on calipers are ~30mm long whereas a micrometer are likely about 6mm diameter (and better ones are ground carbide).

This has now got me wondering whether con rod caps have been swapped around at some point in time....

I would not be arguing the toss over a measurement, with a proper engineer, unless I was using the appropriate measuring gear.

I’ll leave you to reply to the ‘over square’ comment.

[niftyrodman]

I have thought the same thing about the rod, Oliver, and that it may be the problem. Fortunately I have another engine which is not bottom end dismantled, so if the problem I have persists, there is a crank and rods to work with. Inspiration killer for sure, sweet little engine.

[niftyrodman]

Thanks Kennet. Ive just ordered a 25-50mill inside and outside Micrometers Ive got a good vernier but I want to be exactly sure. I know the journal that is in question, its too light(the rattle) to be the centre main, so I will take off the sump and pull all the rods off and measure the lot.Incidentally how long from fire up in seconds as a general rule with 21/50 oil before the gauge moves up? Anyone please. The oil pump is not new, and if there is any doubt I will get a new pump. (When the engine is running its about 40- 50 psi) Taa.

[oliver90owner]

The centre main bearing was found to be the problem area in one of my engines which only ‘rattled’ at cold start - reason was simply because I thrashed it at high revs back then. That was a five bearing crank which presumably flexed - numbers two and four mains showed shell wear only on one side, while the centre bearing was dead.

I’ve not trashed the bottom end of an engine since about 1987 (actually bought a new diesel, that year ) although a few engines have required top-end fixes. Simply inspecting the bearing shells can be enlightening. Nothing lost while you are in there.

One fellow I knew trashed his crank because it came back (after re-grinding, hardening and balancing) with not so much a blockage in a crank drilling, but a ‘restriction’ sufficient to shorten that crankpin’s life - to a few minutes of competition work.

There is always a reason why bearings fail. Mine was over exuberance with the right foot. Find yours - or it will re-occur.

[alawrence10360]

I’ve come to this vernier/micrometer discussion late
During my apprenticeship at GEC Diesels I spent a great deal of time in both the toolroom and inspection departments
If high accuracy was required micrometers in various forms (and there are many) were used or often slip gauges and DTIs, never Verniers
We would often used verniers for use with the measurement of forgings and and castings when in the “black” because of convenience as they have a greater range but at that stage of production the level of accuracy required was lower
Also they would be used by machinists to mark out castings in conjunction with blue to identity positions of holes etc using a surface table
All the above were very expensive and looked after very carefully and regularly calibrated
The beauty of these electronic verniers widely available today are that they can be zeroed before use but I can’t help thinking this lulls you into a false sense of security, also just because the have a read out to 3 decimal places doesn’t mean they are accurate to that.Internally there is a electronic mechanism counting 1s and 0s based on a small probably plastic cog which is mass produced and I cant believe it’s manufactured to the tolerance that the completed device purports to give
The cost of these devices is so low that I am very sceptical on their accuracy.
I may be old fashioned, reluctant to change, and not upto speed with the latest technology but my gut feeling is that these are good in instances where in the past I would have used a caliper and a rule to measure the OD or ID of a work piece but anything else I think I would use a mic

[philthehill]

The problem I see is that how many people know how to use a micrometer correctly.
Does the micrometer you (the general you) have purchased come with a test piece. The Moore and Wright micrometers I possess all have the factory test pieces and adjustment spanners to enable correct calibration.
If you want absolute accuracy yes a micrometer is the way to go but a good quality electronic vernier checked against a test piece(s) will tell you whether you have a faulty journal or not.
Whether you buy a micrometer or electronic vernier always buy a good quality branded item. Cheap is not the way to go.

Phil

[alawrence10360]

I’ve come to this vernier/micrometer discussion late
During my apprenticeship at GEC Diesels I spent a great deal of time in both the toolroom and inspection departments
If high accuracy was required micrometers in various forms (and there are many) were used or often slip gauges and DTIs, never Verniers
We would often used verniers for use with the measurement of forgings and and castings when in the “black” because of convenience as they have a greater range but at that stage of production the level of accuracy required was lower
Also they would be used by machinists to mark out castings in conjunction with blue to identity positions of holes etc using a surface table
All the above were very expensive and looked after very carefully and regularly calibrated
The beauty of these electronic verniers widely available today are that they can be zeroed before use but I can’t help thinking this lulls you into a false sense of security, also just because the have a read out to 3 decimal places doesn’t mean they are accurate to that.Internally there is a electronic mechanism counting 1s and 0s based on a small probably plastic cog which is mass produced and I cant believe it’s manufactured to the tolerance that the completed device purports to give
The cost of these devices is so low that I am very sceptical on their accuracy.
I may be old fashioned, reluctant to change, and not upto speed with the latest technology but my gut feeling is that these are good in instances where in the past I would have used a caliper and a rule to measure the OD or ID of a work piece but anything else I think I would use a mic

Having said all that I’m amazed how cheap a micrometer is these days.
During my first year of training a friend made a cock a doodle diddley up on his test piece and instead of doing it again he used his initiative and ground down the anvil of his mic and presented it to the instructor
Needless to say he was found out and it was a weeks wages to pay for the instrument.
I’ve just had a look at the prices of Moore and Wright mics and the prices don’t seem to have changed in 40 years ...

[pgp001]

I bought three boxed Moore & Wright micrometers in as new condition at our model engineering club auction evening last year.
They were 5-6", 6-7" & 7-8" and cost me a grand total of £1.50. No one else was remotely interested in them.

On the flip side I was extremely lucky to find a rare Grimshaw & Baxter micrometer made in 1900 at an antiques fair a few years ago and paid £20 for it.
I sold it to an American tool collector on ebay for £2975.00 , apparently there were only two of them known to exist in the world.



Phil

[oliver90owner]

I have a set of about 80 gauge blocks ranging from 0.1001” up to 4” (presumably a little more precise than ‘just 4”). Imperial, not metric, but that does not bother me.

They date from November 1960, but good enough for me as nearly all will still ‘wring‘ together.

They could give me both the ‘feel’ for using my mics and do suffice as a good calibration standard/check as needed (‘feel’ and readings go together, really).

Of course, my mitutoyo digital calipers all agree closely with the gauge blocks - but that is over an anvil Length of some 30mm.... I’ve never tried them with just a few mm contact because I simply rely on my micrometers for the final measurements.

[niftyrodman]

With all due respect to all the tech advice I will test my elec vernier with the mic and visa a versa. The reason I bought the mic is because of its design with a finer point of reference, but my theory is that if the cold start rattle disappears when the cylinder No3 is disabled it has to be the bearing of that cylinder, because if by any chance it was a main bearing, disconnecting one cylinder would not stop it rattling. For some reason in these engines clearance at the "big.end" is critical.

[kennatt]

Nothing wrong with your theory and you are probably on the right track,but there is still a possibility, that it is caused by oil draining back into the sump and no oil round the bearings Main and big ends on start up,usualy the result of a problem in the mains. Good luck with it

[oliver90owner]

Your ‘theory’ is only an hypothesis, until proven to hold true under the given constraints. I can’t even begin to count the times my initial thoughts have been wrong , so I don’t try to draw conclusions until all the results are in and collated. An open mind, to all possibilities, is better than tunnel vision, IMO.