Seized JP2

[steamraiser2]

From the dimensions you quote a new "off the shelf" big end shell will not fix it. It falls between the stock shell sizes. Re-metalling and boring to size will do it provided that any ovality of the journal is within tolerance. Be careful as we have had a crop of JPs through in recent months where the journal ended up beat to pieces because the replacement bearing did not meet the tolerances.

 

Don't risk breaking the crank, which JP's are prone to do when running with worn or damaged bearings,for a quick fix. Check the crank for end float. If there is a significant amount of end float (anything above a few thou) it is a pretty good indicator that the bottom end is generally clapped out and in need of refurbishment.

 

Your decision making now is pretty important. Things could get a lot worse.

[Tunneltug]

I am astonished how intolerant JP engines are turning out to be and how fragile, I don't really know how they got the reputation of being a work horse. I worked in the pump industry for years, from designing new pumps to on site servicing up to my knees in sewage. We sold a few hundred pumps a year from 2 to 10inch most of these used lister engines but we did fit Cummings, hatz and even some big german petrol engines whatever the customer asked for (in one case we made 6 pumps with 50hp DC electric motors). These pumps had to work hard for a living and occasionally came in for an expensive factory rebuild. These things were doing 15 thousand hours between rebuilds and were still recoverable. We obviously never used JPs and I think that was a good thing as we would have gone bankrupt with the short service period they offer between major rebuilds, they wouldn't have been able to do the job.

 

I think I should recommend that Alan dumps the jp and installs something more robust.

 

Ha Ho, it's Alan's decision.

[RLWP]

And what does it say on the back of the shells?

 

Richard

[Tunneltug]

Hi Richard, I havent got them with me they're still on the boat, I'll get them soon and get back to you but it's probably not going to be before Wednesday now as I've got to do some stuff before joining Hasty at Braunston for the rally.

 

Speak soon,

 

Keith

[starman]

I am astonished how intolerant JP engines are turning out to be and how fragile, I don't really know how they got the reputation of being a work horse. I worked in the pump industry for years, from designing new pumps to on site servicing up to my knees in sewage. We sold a few hundred pumps a year from 2 to 10inch most of these used lister engines but we did fit Cummings, hatz and even some big german petrol engines whatever the customer asked for (in one case we made 6 pumps with 50hp DC electric motors). These pumps had to work hard for a living and occasionally came in for an expensive factory rebuild. These things were doing 15 thousand hours between rebuilds and were still recoverable. We obviously never used JPs and I think that was a good thing as we would have gone bankrupt with the short service period they offer between major rebuilds, they wouldn't have been able to do the job.

 

I think I should recommend that Alan dumps the jp and installs something more robust.

 

Ha Ho, it's Alan's decision.

Don't say this sort of thing - it makes us JP owners anxious!

[Giant]

I am astonished how intolerant JP engines are turning out to be and how fragile, I don't really know how they got the reputation of being a work horse. I worked in the pump industry for years, from designing new pumps to on site servicing up to my knees in sewage. We sold a few hundred pumps a year from 2 to 10inch most of these used lister engines but we did fit Cummings, hatz and even some big german petrol engines whatever the customer asked for (in one case we made 6 pumps with 50hp DC electric motors). These pumps had to work hard for a living and occasionally came in for an expensive factory rebuild. These things were doing 15 thousand hours between rebuilds and were still recoverable. We obviously never used JPs and I think that was a good thing as we would have gone bankrupt with the short service period they offer between major rebuilds, they wouldn't have been able to do the job.

 

I think I should recommend that Alan dumps the jp and installs something more robust.

 

Ha Ho, it's Alan's decision.

 

I reckon that the JPs are just as bombproof as the smaller stationary Listers. The fact so many are still going after decades of use, often with only pretty basic maintenance, proves that. The thing is that many have now been going so long they are showing up longer term issues deeper in the engine that need a rebuild to tackle.

 

I'd bet that you could take one that's been fully rebuilt to a high standard today, and use it with only quite rough maintenance for another 50 years. It might be knackered by the end of it, but it'd probably still be going.

[frangar]

 

I reckon that the JPs are just as bombproof as the smaller stationary Listers. The fact so many are still going after decades of use, often with only pretty basic maintenance, proves that. The thing is that many have now been going so long they are showing up longer term issues deeper in the engine that need a rebuild to tackle.

 

I'd bet that you could take one that's been fully rebuilt to a high standard today, and use it with only quite rough maintenance for another 50 years. It might be knackered by the end of it, but it'd probably still be going.

I agree. When I got my boat the timing was well out due to wrong timing marks being used but it ran with some smoke. I think they are good engines but like all machinery especially older stuff they need some love and care from time to time.

 

Cheers

 

Gareth

[steamraiser2]

We recently rebuilt a JP3M for a client who bought back into the family a narrowboat built by his grandfather forty years ago. The JP3M was second hand when first installed. It was a bit wheezy with typically low oil pressure and had the wrong big end shells fitted by "a bloke on the canal". Following a total rebuild it now runs like a watch. As the grandson said "his grandchildren will need to refurbish it again in fifty years" Not a wild claim for a JP.

 

JPs are great engines if given the TLC they deserve. Bodge it at your peril. The same holds true for most of the classic engine types found on the canals these days.

Edited June 25, 2015 by steamraiser2

[martyn 1]

I agree. When I got my boat the timing was well out due to wrong timing marks being used but it ran with some smoke. I think they are good engines but like all machinery especially older stuff they need some love and care from time to time.

 

Cheers

 

Gareth

Very true.

 

The general gist of what I and my father (Steamraiser2) have been trying to make is that in regards to JP2's in particular don't follow the quick fix, "well it's sort of in tolerance so we will temporary fix it... AKA bodge" as the JP2's don't have a center main and this coupled with a crank design from before it was common knowledge that sharp edges/angles cause stress raiser. This means they do have more of a tendancy to break cranks if ran on worn out bearings, but in many cases there is not much to show there is an issue until that happens. Unfortunately we have had too many come through our workshop in this state and in 99% of the cases all because it didn't get the required TLC when it actually needed it. To put it into context the JP3's are less of an issue in this area as there is a main bearing between each cylinder.

 

By no means is a JP a weak engine, there wouldn't be so many still in existence if that was the case, but as with any engine they have their strong and weak points. For example JP's have on their plus side that they are extremely simple in design on there negatives the crank design in the 2's and 4's with two cylinders between each main bearing and a crank with stress raisers makes them weaker in this area than some other engines. Onto Gardner's the L2 cylinder blocks are very susceptible to frost damage and crack easily along the manifold side of the engine and the LW's have a tendency to crack heads between the valves and injector(sprayer) hole if mistreated.

[Tunneltug]

"Bodge at your peril" an interesting term from somebody who knows nothing about me or my 30 years as a chartered engineer, and not one of the people who call themselves engineers because they strip and reassemble engines but the sort of engineer that understands engines and mechanics from the Otto Cycle to the eutectic characteristics of white metal, the sort of engineer that has designed single crystal components to as I said before having been dragged out of my cushy engineers office to stand knee deep in sewage to get a pump running when the mechanics had given up and hand scraped pre-war Daimler white metal bearings.

 

I'm sorry to be so pompous but the the assumption that I cannot make the judgement regarding a reasonable and appropriate repair of a basic engine without "bodging" is both condescending and outrageous. I originally asked the forum for tips on a seized engine that I haven't worked on before and I received that info from a contributor who told me that it will be the big end farthest from the flywheel. Good info thanks it took me Ten minutes to free the seize with this info.

 

I can say however that boat owners are more precious about their engines than aircraft owners and this seems to have been elevated to an art form to the point where an engine with the slightest signs of wear has to be ripped out and completely rebuilt and of course polished something I admit you will never catch me doing.

 

Thank you all for your valuable input which has been useful it is always worth respecting the knowledge and experience of others. Alan's engine has suffered years of neglect, negligence and even bodging however to suggest that anything less than a full engine out strip down and overhaul is a bodge is frankly nonsense.

 

Thank you once again but I think this thread has served its purpose and ran its course.

 

Regards

 

Keith

[martyn 1]

Keith, I have hesitated as to put this here or via PM, but for completeness of the thread here it is...

 

From your last I feel a little wrong end of stick grabbing has taken place but then wording can always be interpreted in multiple ways so I will endeavour to be clearer in the future.

 

The advice/comments made is based on the plus side of 100 JP overhauls along with many other engines of this era right through to modern equipment and from two time served engineers who like yourself do also both happen to be CEng.

 

At no point was the "bodged" comment aimed directly at you but was for the benefit of the greater world wide web who might read this. On far too many occasions we have been ask for advice, given it and then had it ignored, only to have to deal with the tears before bedtime when the inevitable happens that could have been avoided. We work on the theory that advice to allow prevention is being more proactive than just standing back and allowing the worst to happen to someone who may not know the consequences of their actions. For example in post 33 my father mentioned a JP3M that the owner had asked for advice on low oil pressure problems, and then as time would tell had ignored the fact that after we had talked them through checking end float, pressure relief valve, oil level, pipework etc and in general it was shot had “someone on the canal” change the big ends “standards on an at the time 0.020” under crank!!! and then continued to use it even though the oil pressure issues were still apparent. When the engine finally arrived with us I had to grind the crank at maximum undersize to recover it, all because it wasn't dealt with correctly when it was needed first.

 

To put it another way, on a forum like this you may well have people who read the comments as “teaching grandma to suck eggs”, but also many more that would otherwise not understand the content as it is out of their field of expertise. So we always try to remember most people are end users, not time served engineers, so assume a low level of knowledge and the reader can pick out what they need to know from what they already do.

 

As we are well aware that on the basis of my previous comments you had removed the bearing and inspected it and the journal and were/are trying to source a replacement I have no doubt that a proper job is what your intending and that although worn you have made the judgement call that the journal is not oval or tapered outside of the Lister stated tolerances. (I can supply these if you don’t have them, they are not in the workshop manual but are in the manufacturing/refurbishing drawings).

 

What my father was getting at is that the dimension of 2.975” you previously stated based on a bearing to journal clearance max of 0.004” and as new being 0.002” is no good for any of the off the shelf standard undersizes. Therefore the fitting of a .020” undersize would leave an incorrect clearance, therefore doing so would be wrong, incorrect or bodge, whichever term you wish to use.

 

Now the next std undersize would either require boring and hoping there is enough white metal there to allow it or most likely a crank out and regrind, which in most cases the space around the engine requires an engine out. Another option if the crank journal is spot on is the manufacture of a bearing made to suit that journal, which would then satisfy the tolerance requirements and not require the removal of the engine.

 

Martyn

Edited June 25, 2015 by martyn 1

[Tunneltug]

Dear Martin, thanks for this clarification which makes perfect sense now I have got off my high horse. I'm sorry if I was over reactionary and have taken your comments on board. You're right that the written word can sometimes not convey the desired message even though the words are correct and I should have spotted this. I do apologise for my abrasive paragraphs there's no real excuse.

 

Regards

 

Keith

[martyn 1]

No problem, we all get hold of the wrong end of the stick from time to time. Back to the original topic, if you do need the full tolerances that are not in the normal manual, just ask.

 

Martyn

[Tunneltug]

Yes please Martyn that would be very helpful.

 

Regards - Keith

[RLWP]

I'm going to bung something in too

 

I've learned a lot about JP crankshafts from this thread, particularly about the sensitivity to stress due to the design. That stuff about ignorance about fatigue cracking and using sharp corners, plus the two bearing crank makes perfect sense

 

Richard

[bizzard]

I'm a bearingless crank.

[RLWP]

I'm a bearingless crank.

 

But not necessarily harmless

 

Richard

[bizzard]

 

But not necessarily harmless

 

Richard

Only if I drink Ovaltine.

[RLWP]

Only if I drink Ovaltine.

 

[bizzard]

 

Wonderful, thanks Richard.. I sailed past the Ovaltine factory at Kings Langley on the GU 10 years ago when they were in the process of demolishing it. It was a beautiful building in the Art Deco style. I was very sad, it spoilt my trip.

The canal on one side of it and the west coast main line on the other. Going to Liverpool as a kid on the train, mum would always point it out to us and we'd sing that song. The factory had a big clock and thermometer on its tower which could be seen far and wide. I also like Virol malt.

 

Forgot the T.

Edited June 25, 2015 by bizzard

[steamraiser2]

Oh my! Ovaltinies! They are still out there! Be afraid, be very afraid!

[George94]

The factory building is still there, Bizz, and looking lovely, though it's now posh flats rather than a factory.. Perhaps they just rebuilt the facade, or perhaps it was a refurb rather than a demolition.

[Mrs Tawny Owl]

What my father was getting at is that the dimension of 2.975” you previously stated based on a bearing to journal clearance max of 0.004” and as new being 0.002” is no good for any of the off the shelf standard undersizes. Therefore the fitting of a .020” undersize would leave an incorrect clearance, therefore doing so would be wrong, incorrect or bodge, whichever term you wish to use.

 

 

Martyn

 

 

Can I just clarify something please.

 

If you've seen my thread you'll see I've taken over the Lister parts business of MES, so am in the market to sell such things.

 

My understanding is that with a starting size of 3in (that may be where I am wrong, it's what Keith suggested and I haven't had a chance to check the details) .020 undersize would give a shaft diameter of 2.980. Less the tolerance of .004 gives a shaft diameter of 2.976.

 

If those numbers are correct are you really saying .001 is enough to cause the crank to break in the not too distant future?

 

I know tolerances are very important, and that .001 on a shaft is enough to make it not fit a hole, but I'm surprised it's enough to go from OK to catastrophe on a shaft running with clearance in a bearing.

However I do understand that you have a lot more experience in this field than I do, I just want to understand it properly, and give my customers the correct advice.

 

Thanks

 

Sue

[martyn 1]

My understanding is that with a starting size of 3in (that may be where I am wrong, it's what Keith suggested and I haven't had a chance to check the details) .020 undersize would give a shaft diameter of 2.980. Less the tolerance of .004 gives a shaft diameter of 2.976.

 

If those numbers are correct are you really saying .001 is enough to cause the crank to break in the not too distant future?

 

I know tolerances are very important, and that .001 on a shaft is enough to make it not fit a hole, but I'm surprised it's enough to go from OK to catastrophe on a shaft running with clearance in a bearing.

However I do understand that you have a lot more experience in this field than I do, I just want to understand it properly, and give my customers the correct advice.

 

Hi Sue

 

You are correct for your workings out and yes 3" as std, but to put it as a short answer, manufacturers put tolerances in for a reason. The clearance is meant to be between 0.002" and 0.004" and that 0.001" outside of that means its outside of tolerance, and actually is 0.003" from the as new 0.002". Now by no means will it self destruct within minutes of starting it but as you are already past the maximum clearance the additional movement allowed as the journal loads and unloads when running will ultimately shorten the lift of the bearing in comparison to getting it within the tolerances to start with.

 

Its a bit like measuring your tire depths for an MOT (legal limit of 1.6mm) and measuring 1.5mm and then wondering why its fails its MOT for bald tyres when its only 0.1mm under. The limit is there for a reason

 

In general as a lot of mine and my fathers posts on here have pointed towards (Oils being a good example). If what you find is outside of the parameters stated in the manual for your engine then you need to do something about it so it is.

 

I hope my ramblings whilst typing on my phone make sense.......

 

Martyn

Edited June 29, 2015 by martyn 1