Author Topic: 12/2 rebuild questions  (Read 15540 times)

captfred

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12/2 rebuild questions
« on: August 23, 2008, 04:45:01 AM »
Helping to rebuilding a friends 12/2  (new crank, bearings, pistons/rings/liners, camshaft etc), But have run into a binding problem - crank is difficult to turn with one con rod torqued down (haven't got to the second one.)

Followed the book and torqued down the rod nuts to 55 ft/pounds then backed off one and checked with a feeler gauge - only .004" - recommend .004" - .006" - so does this one require a shim or is it good and just torque down"

I'm also in a quandary about how to properly set the end play in the crank so the roller bearings are adjusted properly (we adjusted the number of gaskets at each end and then tightened down the set screw for the center roller bearing).

Got something mucked up - any assistance would be greatly appreciated



On a side note, there were no timing marks on any of the new parts (cam, idler or crank), ended up drilling our own timing marks.



Cheers, Fred

M61hops

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Re: 12/2 rebuild questions
« Reply #1 on: August 23, 2008, 06:40:57 AM »
Hi Fred!  Just because I don't know what I'm talking about doesn't mean I won't try and give advice  :P !!  If the cylinders are on could the binding be caused by deck alignment?  That is you might need to shim one side of the cylinder so the piston travel is parallel to the cylinder wall?  My first thought when I read your post is that the piston is binding on the cylinder wall because the deck is not square to the crank.  It sounds like the bearing nip would be proper if you just torque the nuts without a shim; if I'm understanding your situation.  The crush or nip as the Limeys like to call it keeps the bearing from spinning in the rod and is different from the actual running or oil clearence.  If the rod binds on the journel after you torque the nuts you probably don't have enough oil clearence.  This should be checked with plasti-gauge or micrometer measurements.  Does this engine have a roller bearing for the center main bearing?  I thought all Listeroids had a plain bush type center main bearing.  Goes to show I can't offer a suggestion there  :-X !                      Leland
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Geno

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Re: 12/2 rebuild questions
« Reply #2 on: August 23, 2008, 11:38:43 AM »
I think crank end play is .005" or barely perceptible movement and no binding.
If you can get any plastigauge you can use it on several places on the big end bearing, one at a time and adjust to .002"

Thanks, Geno

captfred

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Re: 12/2 rebuild questions
« Reply #3 on: August 23, 2008, 01:52:30 PM »
Thanks for the responses Leland and Geno, will look into them tomorrow.  I asked about plastigauge at several parts stores and they were clueless - should have known better - will order some, but with the power situation, my friend (it's not my engine. really  :D), would really like to get the beast running - would take a week to get plastigauge mailed out and no sunnen equipment on island to properly hone bearings if required

BruceM

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Re: 12/2 rebuild questions
« Reply #4 on: August 24, 2008, 12:02:36 AM »
I've had problems with Rajkot quality on conrods.  Assuming that your big end machining was done properly is a fairly wildly optimistic position based on my limited (2 conrods, both defective) experience.

Mieasure the fitted bearing for trueness with a telescoping gauge, also make sure that the cap and rod fit properly such that the bearing has no mismatch.  I have one conrod with an out of true bore, binds on one side and excess clearance on the other.  The other was apparently bored with bent cap bolts and when the cap is tightened with my straight bolts, it is shifted slightly, which caused binding on the crank.  Reworking that was very time and patience consuming. Check the crank for roundness too.

The Rajkot solution is to add shims until it turns easily.  Not the best solution for longevity.

Best Wishes,
Bruce
« Last Edit: August 24, 2008, 12:04:48 AM by BruceM »

captfred

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Re: 12/2 rebuild questions
« Reply #5 on: August 24, 2008, 01:31:25 AM »
Thanks Bruce

We changed the liners and pistons cuz of odd wear at the top of the liners - slight ridge on one side but not the other (bent rod is my guess)  will have to do some research to find some proper micrometers - no easy task here - and a friend in guam is looking for some plastigauge to send up.

We did chuck up the crank in a lathe and check with a dial indicator - appears to be true - the center bearing fit seems good - end roller bearings too - so it's time to double check the rod bearings and journals again

Fred

captfred

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Re: 12/2 rebuild questions
« Reply #6 on: August 26, 2008, 04:42:58 AM »
Pulled the crank out and set it up in a jig to fit the rod bearings - here's what I got ...



As per the book torqued down the nuts to 55# and backed off - got 5 thou as in the picture (between the recommended .004 and .006)



installed the conrod on the crank with .004-.009 plastigage and torqued to specs - rod wouldn't move - ended up installing three shims  with another plastigage check and it came out .004 clearance.  Now I'm a little lost.

Don't believe there's anyone on island  with a sunnen hone to fit the rod bearings to the crank - and I agree with Bruce that a bunch of shims isn't the best solution for longevity (that's the idea behind this rebuild - longer reliable operation)

Any ideas would be most appreciated.

Cheers, Fred

mobile_bob

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Re: 12/2 rebuild questions
« Reply #7 on: August 26, 2008, 06:15:22 AM »
fwiw :)

first things first

pull the crank out of the case so you can work with it easily

1. check the journal with a mic, for out of round, taper and finish,, make sure it is within spec's

2. check both rods ID and make sure they are to spec's, round of course (don't forget to torque them first)

if the rod end is eggshaped (narrow 90degrees from the parting line), add shims to get the bore to round

3. clean the brg shells inside and out, clean the rod bores again, check for lint, grit etc

4. install the upper shell, and push one side down flush, and check the other end at the parting line, it should have a couple thousands of nip.
this provides the needed crush when assembled with the cap and torqued. check the bottom shell as well.

if you have had to add shims to the rod to get it round measure them, and subtract this measurement from the nip of the shells
for instance if you have added .002 shims (two of them, one on each side, 2 x .002=.004)and you have determined that the nip is .006
then you will have the needed .002 nip with the shims installed.

if you have more than the needed .006 then you will need to file down carefully the parting line to reduce to .006

note, the "crush" is needed to lock the brg into the rod when it is torqued and to provide positive heat transfer from the brg to the rod.

5. then assemble the rod w/shells and shims onto the crank journal, with a piece of plastigage across the brg shell on the bottom (weight of the
assembly will open the clearance on the bottom) and  torque to spec (do not rotate the assembly),

6. disassemble and check the plastigage to see what you clearance is. if everything was to spec, you should have the .002-.003 clearance.

7. final check is the side clearance just for kicks, use a feeler gage to check between the flange of the shell and the cheek of the journal.

as with anything, careful attention to detail at each step will provide the needed info on where the problem is if there is one, and also assure that
everything fits as it should.

in a perfect world if i found the rod end to be eggshaped and needed shims i would have the rod end honed to spec and perfectly round
and "not" use shim's. shims in my opinion add a level of complexity that need not be there with modern brgs which don't have a thick babbit layer
like the early brg shells had.

if you have a round rod bore end forget the shims and fit the shells to provide the .002 nip and you will be set

as for the main brgs,
this is from many years of setting up tapered roller brgs :)

i like to set them up with the shims where there is "no" end clearance, none!
set them up so that there is a slight drag when rotating the shaft by hand, if you try to spin it by hand it might make a half revolution.
but feel equal around the full rotation.
the reason is tapered brgs will wear in a bit, the angles of the three elements (inner race, outer race, and rollers) are not perfect
and over a bit of time will wear in a bit and clearance will come about.

a final check is to seat the brg assembly with a block of hardwood and a 4lb hammer, a couple smacks on the end of the crank
with the wood as a protector to provide a bit of shock which will aid in settling the assembly. then recheck the preload of the brgs
spin by hand again to see if things got a bunch more loose,,, if so tear down and reshim accordingly, (wash rinse and repeat) :)

another check if you are so inclined

use a precision level, and level the crankcase across the deck, shim to get it dead on with whatever you need
then use the level to check the crank to see if it is level in the block as referenced to the deck.
check several times to make sure nothing has moved in your shims under the crankcase
if the deck is level and the crank is level as referenced to the deck you are golden to this point

if however the crank appears to be not level with the deck, then rotate the crank 180 degrees and see if the bubble moves in the opposite direction
if it does move you may have a bent crankshaft, so check on the other end of the crank and see how it works out.
the goal of course is to have the crank dead level with the deck.

if the bubble does not move but the crank is not level with the deck then you will need to determine how best to get it level.

basically follow a logical progression and write down the numbers one step at a time.

bob g

ps, it is late and i need to recheck my "nip" numbers, but the proceedure is correct even if i am off a thou or two :)


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GuyFawkes

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Re: 12/2 rebuild questions
« Reply #8 on: August 26, 2008, 02:01:45 PM »
With patience, or lack of machine shop alternatives, in an 8 hour day with nothing more than emery tape, kerosene and some prussian blue you can hand grind a crankpin to better tolerances and accuracy that you will get on a workaday crank grinding machine.

If in doubt buy something cheap like a lawnmower engine to practice on.

It really isn't difficult or technically challenging, all it takes is patience and working where the blue tells you to.

You don't even need a micrometer, when you have it right the oiled and assembled con rod will fall / rotate smoothly under its own weight.
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oliver90owner

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Re: 12/2 rebuild questions
« Reply #9 on: August 27, 2008, 12:04:52 AM »
This whole engine rebuild sounds a bit of a problem.

I am wondering how many hours has it done before needing such a major overhaul?

OK. so there appears, from reading the thread, that something is seriously mis-aligned.

Could be the crank/deck or rod(s) or other possibitities.

The replacement bearings sound like rubbish or perhaps the crank pins are slightly over-sized.

The damage/wear to the bearings should have been observed, checked and noted at the dismantling stage.  It was obviosly loose before rebuild so it should not be too difficult to compare previous with replacement parts.

As Guy indicates, Prussian blue is great for showing where the lack of clearance is.  They didn't have, and didn't need, plastiguage when these things were first made originally.  Clearance is enough on these bearings.  Plastiguage is only accurate if everything is round. Journal roundness can even  be checked with a large appropriately sized spanner and a few shims (feeler guages) if a suitable micrometer is not available.

My thoughts are that the crank is mis-aligned with the crankcase deck and the new bearings need shimming/ scraping.  I would not grind the crank pins, if they are round and true, as bearings are the cheaper item to modify or replace.

The one thing that is certain is that if all the replacement and original parts (replaced) were good, the problem will re-occur.

If the original parts are still available these need to be inspected to find the cause of failure, or you will need to check everything as you rebuild.  Finding one faulty alignment will not necssarily mean it is the only one!

Remember the originals were not high tech, by modern standards, but with simple and sound basic engineering they lasted for years and years and years....

If the modern version is so much poorer, so be it.  Just rebuild it to the 1929 specs and it should be fine.

Regards, RAB

captfred

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Re: 12/2 rebuild questions
« Reply #10 on: August 27, 2008, 03:54:56 AM »
Thank You Gentlemen for the excellent observations and advice!

Since we really don't have the requisite micrometers, and no hone to fit the bearings, have taken the crank and rods etc down to an older machinist from the PI (he's worked on similar engines back there). Anyway, He's carefully scraped the bearings (I know they say not to do that) with tool stock blank and fitted them to the crank and checked for clearance.

Will begin fitting the crank this afternoon (after leveling the deck for good measure)

As to the reason for the rebuild - the engine was run out of the crate from india - changeover valves were never screwed out and the engine was run at, or near full load 8 - 10 hours per day for 9 months  on straight unheated wvo - nuf said.

Upon tear down the # 2 rod bearing and crank pin were severely scored (can post if you want) the cylinder liner showed asymetrical wear (slight ridge at the top on one side of the barrel, none on the other)

One injector pump lobe on the cam was worn pretty badly due to that injector pump roller's failure.

One rocker assembly bushing was severely worn.

Can't think of another way to "torture test" one of these engines than the way this one was.

Again, Many thanks for the assistance, will try to follow as much of your advice as is possible, and post the results of this project as it progresses.

Cheers, Fred


SHIPCHIEF

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Re: 12/2 rebuild questions
« Reply #11 on: August 27, 2008, 04:13:30 AM »
Fred;
You mention uneven cylinder wear, near the top. If the piston is cocked in the liner, you will get the wear you mention. that could be a crooked wrist pin bore in the piston, or small end bore, or if the cylinder is not perpendicular to crankshaft, which will also bind the con rod big end bearing, causing it to wear prematurely.
Take a second set of plastigage (or prussian blue) readings after the assembled crank, rod & piston are in the block and liner. If these problems exist, the plastigage will be squished unevenly, like the crankpin was tapered. The rod is cocked because of the side force applied to the top of the rod. The Rod could have been machined crooked or bent. Crooked rods and cranks can be bent back within limits.
You can machine, hand work,  shim out, or even pound out problems that you find based on available machine tools, ability, and desire for a 'perfect job'. Like Guy said, you don't need a micrometer. you can hand fit everything.
I'll bet the injector pump roller and cam that were worn came from the injector pump farthest from the governor. That cavity runs dry, and needs to have oil added. I bored 1/8" NPT (in the injector pump support housing) toward the point where the cam lobe meets the roller, and put in a hose to pipe fitting with a small piece of tube soldered in. once the fitting was threaded in, I bent the tube to dribble onto the cam. I ran the  hose to the oil pump top fitting, using a needle valve to control flow. I also put an oil filter in this line, but that's another story.
On the other hand, 9 months of abuse on such an engine, straight out of India was probably pretty good service...
Scott E
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captfred

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Re: 12/2 rebuild questions
« Reply #12 on: August 27, 2008, 05:21:58 AM »
Hey Scott, thanks for the information - I'll check it again with plastigage after assembly - we've another set of rods if one's bad, maybe I can get one of the engineers on the prepo ships to check it for true - isn't anything on island.

Funny you mentioned your oiler mods for the injector pump - I was just reading that other post cuz I'm thinking of adding oil filtration to my engine - oddly enough it was the one on the governor side - we ordered 4 new spares and only one rotates, need to take em apart and adjust the clearance between the plunger slot and the end roller.

Guess part of the problem is mine - grew up working in an automotive machine shop where we had virtually everything - fitting bearings was easy with that old sunnen rod hone etc.

A lot to be said for working with a guy who's done this kind of work all his life by hand.

Hoping to get a bit more service this go around.

Thanks again, Fred

Hey Jens, you just posted as I was about to post this -

I thought the same thing about the changeover valves and increased compression for the wvo - til I read another post about possible bearing damage by running with em screwed in, so I screw mine out during running.  I mentioned the unheated wvo just because - wanted to provide some background to the running of the engine prior to the rebuild - I only heat mine from the coolant and the engine heat - temperature at the injector runs around 180 F - just posting these particulars for information.

Cheers, Fred





Thanks again, Fred

mobile_bob

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Re: 12/2 rebuild questions
« Reply #13 on: August 27, 2008, 06:26:49 AM »
Capt:

as you probably are aware :)

the shims worked in the old engines because the babbit was quite thick, it wears down and you can remove a shim.

however

the newer brg designs do not have as thick of a babbit layer, therefore scraping can get you down into the harder base metal
which ends up defeating what the primary purpose for the babbit layer is, that being a place to embed tiny particles so they do not lap your crank
journal all to hell.

you might check with your old machinist friend and take him the old set of brgs so that he can determine just how thick the babbit on these brgs actually
is.  would be a loss to determine he needs to scrape out 2 thousands when there might only be 3 thousands of babbit there to start with.

if he scraped out the 2 thousands leaving only 1 thousands any particle that is over 1 thousands would then be really good at grinding your crank journal.

until it is determined just how thick the babbit is, and unless i could determine that i would have at least 2-3 thousands babbit left after scraping them, i would
be very hesitant to scrape them at all, unless i was in a desperate situation and didn't expect long life as a result.

the design of the engine has changed very little over the last (forever), but the brg manufacture process has definitely changed to much thinner babbit layer.

fwiw

bob g
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oliver90owner

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Re: 12/2 rebuild questions
« Reply #14 on: August 27, 2008, 08:28:02 AM »
SHIPCHIEF ,

I based my guess as misalignment of deck/crank because of this:

              odd wear at the top of the liners - slight ridge on one side but not the other

I took this as both liners and wear on the same side of both.


Unless a whole load of bent rods were made, and used, I would be surprised if it is both rods - well, OK, perhaps I wouldn't be so surprised!!

From previous reports on the forum of mis-aligned cranks, I would be looking there first.



bob g,

They have  grooved the bearings for lube so i doubt that the babbit is that thin and I doubt the Indians have bi-metal layers in the babbit.  I would use a combination of shims and scrape if necessary - that always leaves space for adjustment later as necessary

captfred,

You said:   grew up working in an automotive machine shop where we had virtually everything

Surely then, checking out and measuring up should be second nature to you.........and you have the parts that were removed.  You could have checked the new bearings on the on good crankpin to compare and easily determine the differences.  You now have fitted bearings which may still be fitted to bent rods.  You could still have a nightmare situation as you progress and find other dimensions which need correcting and may alter what was needed at the crank end.  Rather you than me....

Again spanners and shims for ovality, straight edge and spacers + shims to check crank pin heights, machined bar through the small end to check for alignment.  They may not be the accepted modern-day means of checking but who cares as long as it suffices, so there is nothing that can't be got round, without a micrometer, to check/get these engines inside their original tolerance specs, excepting the absolute measuring values, of course.

3000 hours and scrap is not a good situation.  Not much better than some of the B&S (well the ones I have come across).

Regards, RAB