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10E problem

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10E problem

Post  Malfisher on Sun Mar 06, 2011 12:24 pm

OK, what have I done wrong!

Ive been rebuilding the 10E in m Falcon 81 I bought recently, the main bearings were in an atrocious condition, and the best thing to do was replace. Also the crank seals were poor. One was hard as bakelite! All in all Im amazed it ran as well as it did.

Got the bearings seals ect Saturday morning so we put it all back together and realised that on spinning the crank the crancases are "walking"! The cases seem to want to move apart, raise and pitch forward, and lower and go backwards accordint to crank position.

Bad news, anyway thinking the crank must be more then a little out, we took it all up to Eckas and put it in the lathe to check for runout. At worst there is a runout of 10 100ths of a mm, which I believe is just under 4 thou. I have not buttoned it all up yet, just used the dowell stud and one opposing it, but the movement in the cases to my mind is too great to risk chancing it anyway. Theyre only very thin studs in the crankcase.

But, the cases are moving visible to what I'd estimate about 1/16th or 32nd in or so. The gap between the flywheels is the same as it was before splitting, and the scribe line is lined up bang on, so what else have I missed here?

Of course, the obvious is very possible, and that being it was like that before, but Im not in the habit of checking for stuff like that on strip-down, just re-assembly so have no way of knowing. Also, a Villiers expert may say, they do that dont worry, again, I dont know Ive not done a Villiers before. All I know is when I do an engine, it dont happen, so why it should with this one needs to be established.

The fact is, this engine has been apart before, the butchery of the fixings and poorly applied red hermetite tell that story, and theres got to be a reason why the cases were split. The mains looked to me like were origionals, so the only other reason I can think that they split the cases is to work on the crank, so maybe it has been split before, put together out, and so all we did was repeat the origional mistake?

The technique we use is this, before we split the crank, an engineers set sqaure is clamped firmly to a flywheel, we then scribe a line, and center-popped each end of the scribed line which is opposite the crank pin. We also took 2 outside measurements of the flywheels, top and bottom, and and 2 measurements of the gap between the flywheels. Heat and a 12 ton press is then used to press the pin out. The bearings were OK so it was then pressed back together, the pin never took fully out of both wheels, just the one.

When reassembling we put it back to these measurements, and lined the scribed lines and centre pops exactly. This being so, what has gone wrong? I need to find out whats gone wrong to put it right, be it my mistake or someone elses, but given the way we do cranks, with the measuring and scribed line, what is it that could have gone wrong?

Unless it was out before, and Ive simply replicated that, possible, but theres no way of knowing.


Heres some before and after photos.

Before









And after:






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Malfisher

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Flywheel

Post  kerabo on Sun Mar 06, 2011 3:48 pm

I would say .0004" is not much at all. I dont know the villiers figures but thats not a lot in any engine. I dont quiet understand if that was your oly problem. My AMC 20T crankpin had moved and was about 1/8" out of the crank web. I made some V blocks and got a magnetic dial gauge. Had a word with nametab and they said it shoud take 2 tonne to push back It was just over this so pressed it in and then put it on the V blocks and trued up using a mallet to about .0006" and no problems.

Ken
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Re: 10E problem

Post  Malfisher on Sun Mar 06, 2011 9:32 pm

Im of the opinion I might well have additional problems here Ken, you could be right.

But, at the moment Ive gone to the limit of my current knowledge and the tried and trusted method has failed for us this time. It could well be that theres something else out, and I will have to learn how to measure everything very accurately to see what may be out, maybe even the cases are slightly out?.

All I know is in all the engines we have previously rebuilt, this has not been a problem before. So Im a bit flummoxed?

Just a question Ken, is yours 0.0006, or 0.006? Im not a trained engineer, but believe one refers to one sixth of a thou, the other to 6 thou, am I right in this thought?

Malc
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alignment

Post  piston 197 on Mon Mar 07, 2011 7:21 am

Malc,the cases would have originally have been machined as a pair and should have matching numbers stamped on the bottom surface where the gearbox mounts,if these numbers (and letter) match they are an original matched pair and will have been line-bored so that they are correctly aligned,if they are numbered differently ,they are not a pair and may be your problem.If they are a pair and with the dowelled bolts in place they crank does not spin freely either your crank halves are mis-aligned or you have a bent shaft,JH
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Re: 10E problem

Post  Malfisher on Mon Mar 07, 2011 10:49 am

Ta for that John, I'll check them numbers in a bit, it never occured to me to do that.

I think I need to try and get a measurement on all this, eg individual shafts, even the new bearings, all needs scrutinising I wont accept a bodge where an engines concerned.

The more I think about it, the more I think the crank could have been put back twisted by a previous mechanic, and Ive just replicated it by using the scribed line technique, which of course works brilliantly if youre putting a true and good crank back to its origional state. But of course it would be vice-versa.

Malc.
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Re: 10E problem

Post  Malfisher on Mon Mar 07, 2011 2:45 pm

We have developments. I checked the cases and theyre matching John, so OK there.

I made up a mickey mouse jig this morning to check the runout here at home, as I couldnt get to the lathe again till saturday, anyway, it is fit for only one shaft at a time, but seems to have worked better. I think this is down to the fact I can get the dial gauge more rigid, who knows.

The timing side is actually running out over half a mm in fact around 0.60 at the extreme tip, not, 0.10 so, it is about 0.0238 thou out not 0.004! And it registers only one way. Heres some pics and film clips.

Film of Reading at the extreme edge

https://www.youtube.com/watch?v=BmdS0EwABa4


Film of Reading near the bearing

https://www.youtube.com/watch?v=Cz9XoFdj_K4


And a few photos of the improvised jig.









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run out

Post  piston 197 on Mon Mar 07, 2011 3:25 pm

Malc,the runout at the extremity you have the DTI mounted is irrelevant as regards getting the flywheels true,and can be influenced by bent shaft or angularity between the two flywheels,the important thing is to have no runout at the point at which the bearing is fitted,so your DTI should be positioned where the bearing fits.I used to turn a true centre in the lathe chuck,a revoving centre in the tailstock,two DTI's at the bearing journals,and then administer copper hammer and morse taper wedges as required .JH
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Measurement

Post  kerabo on Mon Mar 07, 2011 4:05 pm

Malfisher wrote:Im of the opinion I might well have additional problems here Ken, you could be right.

But, at the moment Ive gone to the limit of my current knowledge and the tried and trusted method has failed for us this time. It could well be that theres something else out, and I will have to learn how to measure everything very accurately to see what may be out, maybe even the cases are slightly out?.

All I know is in all the engines we have previously rebuilt, this has not been a problem before. So Im a bit flummoxed?

Just a question Ken, is yours 0.0006, or 0.006? Im not a trained engineer, but believe one refers to one sixth of a thou, the other to 6 thou, am I right in this thought?

Malc

Hi Malc

you possible correct i am used to just seeing it on a feeler gauge and its been many years since college.

Ken
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Crankshaft

Post  kerabo on Mon Mar 07, 2011 4:10 pm

Malc

I have only done a couple of this type of big ends but have covered this at college. The idea is to sit the crankshaft main bearings at the outermost parts in V blocks and put you dial gauge near to the crank webs. Then just a gentle tap will move it more then you would think. Yor correct with the scribe lines. Well this works on a full circle crank.

Did you have other problems?

PS I did some checking I was wrong with how i wrote my measurement see below

0.030 inch; or 0.03 inch, three hundredths of an inch, to which it is equivalent.
Think 30 X 1/1000; cancel a zero top and bottom to get 3/100, three hundredths

(The first digit to the right of the decimal point is the tenths place, next right is the hundredths, and third right is the thousandths place. On the right side of the decimal, your number has to end in the named place, so '30' ends with its zero in the thousandths place. Thirty thousandths is 0.030. Three thousandths is 0.003 .)




Read more: http://wiki.answers.com/Q/How_do_you_write_thirty_thousandths_of_an_inch#ixzz1FvmLU2vp

Ken
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Re: 10E problem

Post  Malfisher on Mon Mar 07, 2011 4:39 pm

Cheers Ken, Its good to have a reference. I worked all this stuff out in 2009 and 2010, for jobs I did then, but I cant ever seem to retain it for long!

but im glad to say that by golly I think Ive got it.
We are down to 0.07 mm now, so that'll be around 0.003, the cases are happy now and so am I it'll do!

https://www.youtube.com/watch?v=d6pOCOPZUSs Smile
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crankshaft

Post  kerabo on Mon Mar 07, 2011 6:10 pm

Well done Malc

Not so sure about having the main bearing in to turn it on.That could lead itself to a bit of inauracy. But I am sure you will be fine. I suspect these move in use a little. Think of the strain if you get a wrong gear and it is suddnenly thrust to many revs as the drive in through one side only of the crankshaft.

Good work
Ken
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Re: 10E problem

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