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Author Topic: New pistons Petter PJ2, block after short time engine running. Clearance?  (Read 10495 times)

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #45 on: October 24, 2018, 03:41:15 PM »

Hi guys!
This video shows a honing tool. I knew it was something like that, but would this size be OK for my bigger cylinders?
https://youtu.be/-NRUZNX0IAg?t=642
Indeed, I'm not going to buy new pistons. They were expensive: 245 euro each. But I could do some light honing, to just get that one hardly noticeable scratch away, right?

I took both cylinders off, with the finger nail I can detect just one light scratch. Other lines are visible but I can't feel them, and I'm quite a sensitive guy, really ;-)! Most of my working hours so far were spent on illustration and design.

I let the pistons sitting on their rods and the crankshaft. There's really no vertical 'play' of the pistons. All the pistons can do is move sideways, over the pins they're attached to the rods with. The rods can not tilt one bit. I see no reason to dig into the block and take it all apart.

I got all other rings off the pistons without breaking any. Did that with sliding them up over three thin metal strips, one of them being a valve clearance feeler gauge.

I'll wait for the manual to arrive in the mail (and stuff) before adjusting the gap of the piston rings. The manual I was using so far, of a one cylinder air cooled Lister LD, actually had measures of the gaps equal to the ones of the new piston rings.

I'll ad the flyer for this engine (earlier I wrote it weighed 300 lb, but that's in kilos. It weighs 611 lb).
I also ad a photo of the boat it sits in, parked in an Amsterdam canal. It was an open life boat coming from a cruise ship. I build the cabin over it. Last summer I painted the black figures at the white hull. The wooden roof part and windows can be taken all off in 2 minutes. There it also has a fire place in it, for wood fire, oh yes! So, that's why I need this engine to work again. I missed 3 months of boating fun already!

ajaffa1

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #46 on: October 24, 2018, 10:41:33 PM »
Hey Rob, honing tools come in different sizes for different size bores. Look on fleabay for one that will adjust to at least four inch. They also generally come with different abrasive heads, coarse, medium and fine.

Bob

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #47 on: October 25, 2018, 09:07:31 PM »
Hey Rob, honing tools come in different sizes for different size bores. Look on fleabay for one that will adjust to at least four inch. They also generally come with different abrasive heads, coarse, medium and fine.

Bob


Hi Bob, today I mail-ordered the proper honing tool with the proper 'sanding stones', honing oil, a piston ring opener, a 'tension wrench' that can handle the in the manual described force for the cylinder head bolts, and some more delicacies from the tool candy shop.
Before all that arrives, there's plenty to do: draining the oil from the block and cleaning it, cutting new gaskets, checking the shims or making a new one with the desired thickness.
And when Jim Perkin's package arrives with the manual, operation handbook, oil banjo bolts (one put in my engine wasn't properly fitting!) and two piston + .020 oil rings, I bet I'm going to have an interesting week after this weekend!

Here's the monster in the state I got it in, in 2011 (here without air cooling cover). It took me three years before I dared touch it. But all it needed for its first start was cleaning the fuel pipes (and a scooter engine to get the flywheel turning with enough speed).
« Last Edit: October 25, 2018, 09:23:40 PM by Rob PetterPJ2 »

Matt12

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #48 on: October 26, 2018, 01:41:24 AM »
Hi Rob,
            I'm a newby to this forum but am an ex motor mechanic, (retired).
Did you notice any scars on the piston skirts, assuming they are alloy pistons, if so, the pistons are 'grabbing' the bores, due to insufficient clearance, if not, then it's likely the top rings are too tight, ( too little end gap), this gap should in your case be around 4 thou per inch of bore, 4x4 = 16 thou.
Hope you have a successful outcome.

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #49 on: October 26, 2018, 12:01:39 PM »
Hi Rob,
            I'm a newby to this forum but am an ex motor mechanic, (retired).
Did you notice any scars on the piston skirts, assuming they are alloy pistons, if so, the pistons are 'grabbing' the bores, due to insufficient clearance, if not, then it's likely the top rings are too tight, ( too little end gap), this gap should in your case be around 4 thou per inch of bore, 4x4 = 16 thou.
Hope you have a successful outcome.

Hi Matt,
thanks for the extra info. I'll check for scars at the pistons, today. But the 16 thou may not be correct, at least not for this particular engine, as earlier written by dieselgman. According to his data is has to be like double that distance. The Petter engine collector Jim Perkins says the same. He'll snail-mail me the manual today.
When pushed the rings into the cylinder for about 2 inches, the gap is only 0.3 mm, which is 0.118 inch. According to the proper manual for this engine (PetterPJ2) it should be 3 times that.
« Last Edit: October 26, 2018, 12:12:28 PM by Rob PetterPJ2 »

glort

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #50 on: October 26, 2018, 02:24:12 PM »

Have you got both cylinders off and checked the gaps of both lots of rings yet?

If so what were the gaps on each one with each ring?  Did you measure piston Clearance.

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #51 on: October 26, 2018, 02:31:49 PM »

Have you got both cylinders off and checked the gaps of both lots of rings yet?

If so what were the gaps on each one with each ring?  Did you measure piston Clearance.

Hi Glort
yes but I'd already written so. at the top pf the cylinder the ring gaps are 0.4 mm. But 2 inch lower the gaps are just 0.3 mm (0.118 inch). All rings the same.

The piston clearance is around 0.3 mm (piston, when I had it lowered in cylinder, pushed to one side, feeler gauge at other side).
« Last Edit: October 27, 2018, 02:03:12 AM by Rob PetterPJ2 »

glort

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #52 on: October 26, 2018, 03:18:55 PM »

OK, thanks. must have missed that.

About the only thing I can't relate to in metric is clearances.  Thou, not a problem. .4mm?? NFI what that looks like.  :embarassed:

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #53 on: October 26, 2018, 03:46:47 PM »
You can't be that helpless, Glort! I have to do it all the time, go from mm to silly inches...
Here's a tool
https://www.rapidtables.com/convert/length/mm-to-inch.html

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #54 on: October 27, 2018, 05:22:26 PM »
Hi Rob,
            I'm a newby to this forum but am an ex motor mechanic, (retired).
Did you notice any scars on the piston skirts, assuming they are alloy pistons, if so, the pistons are 'grabbing' the bores, due to insufficient clearance, if not, then it's likely the top rings are too tight, ( too little end gap), this gap should in your case be around 4 thou per inch of bore, 4x4 = 16 thou.
Hope you have a successful outcome.

Hi Matt,
i can't believe I hadn't noticed it yet, but indeed, one piston is clearly damaged in four places at its skirt. The other one a tiny little bit, but hardly.

So, then I thought, is it the cylinder, or is it the piston? I measured the clearances, at the top.
Piston 1 had 0.3 mm, piston 2 had 0.4 mm clearance.
Then I had the cylinders change place.
Piston 1 had 0.3 mm (0.0118"), piston 2 had 0.4 mm (.0157") clearance....
Meaning: the pistons aren't exactly of the same size, right? Not at the top, at least.

In inches, the measured difference between the pistons' diameters would be 0.0039".

Your suggestion and Glort's very first response (and my own in my 'opening speech', but that more due to not being hindered by any other knowledge) that the clearance between pistons and cylinder might not be enough, seems to be correct.
That fits to the picture of the damage.

Two inches down from the top, the clearance is about 75% of that at the very top of the cylinder, I noticed when I measured the ring gaps at the top (0.4 mm) of the cylinder, and further down (0,3 mm).

I'm not happy with these traces at the piston skirt, can you imagine...
I have to wait for the manual Jim Perkins sends me to see what the clearance should be.

« Last Edit: October 27, 2018, 06:29:19 PM by Rob PetterPJ2 »

mikenash

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #55 on: October 27, 2018, 08:15:26 PM »
Rob - quite a long way back in this thread you said that you had been supplied with oversized pistons because the cylinders had been honed.  When I read that I assumed you meant the cylinders had been bored to an oversize and you were just speaking casually. 

But, reading your comment re the piston skirts, I wonder if the cylinder has been bored correctly to suit the oversize pistons.  Do you know?

Just checking . . .

Cheers, Mike

glort

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #56 on: October 27, 2018, 10:39:04 PM »

So, then I thought, is it the cylinder, or is it the piston? I measured the clearances, at the top.
Piston 1 had 0.3 mm, piston 2 had 0.4 mm clearance.
Then I had the cylinders change place.
Piston 1 had 0.3 mm (0.0118"), piston 2 had 0.4 mm (.0157") clearance....
Meaning: the pistons aren't exactly of the same size, right? Not at the top, at least.

Be aware that pistons are not round, they are in fact ovalised.  This is to allow  for heat expansion.  You could get very different readings  depending on where you measure the clearance.  If you measure it on the wide side obviously going to be different to if you meausre it on the narrow side that is allowed for expansion.

I also suggested you check the pistons a while back because I did not know what potential effects having the rings bind would be, but I could imagine the possibility of the pistons being rocked sideways as the force of the rods tried to make them go where they didn't want to.

Sorry to say but there seems to be a LOT going wrong here.  Perhaps it is time to call in an experience mechanic and have things looked at and you may be wise and save money in the long run having them re assemble the thing for you.  I think if you are going to have any need for reliability on this thing, It would be a very smart move to at least have an experience eye look it all over for you.  There could very well be other problems in the making that you are not aware of now.

Clearly your skill set is in other places which is fine, we all are experts in some things and not so much in others.  Not gapping the rings was a huge oversight and potentially very expensive. I know you like anyone else does not want to part with any more money than you have to, but I think the investment in an experience person may save a lot of money  at best and give you good peace of mind at a Minimum. As you have seen, as straight forward as an engine is, there is a bit more to it than just meccano where you put the bits back in place in order.

I hope your pistons are OK but if they are not, the cost of replacing them will probably make the cost of a mechanic the cheaper option straight up. In my experience as limited as it is around marina's, there is always a knowledgeable mechanic  hanging round some where so start having a look at places close by and see whom you can turn up.  At very least they can tell you if the machine work has been done correctly or not so you know which way to go.
Also having an experienced and knowledgeable person argue any warranty work will give you infinately better chance of getting somewhere and eliminate the chances of you getting baffeled with bullshit and fobbed off.

I really think the problem is going to be your own than theirs but in any case, you are in a very bad position now having put the engine back together your self incorrectly.  Have it at least checked out by someone in the know and find out about them putting it back together for you so you have some peace of mind there won't be any more problems down the river as it were.

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #57 on: October 27, 2018, 11:42:06 PM »
Rob - quite a long way back in this thread you said that you had been supplied with oversized pistons because the cylinders had been honed.  When I read that I assumed you meant the cylinders had been bored to an oversize and you were just speaking casually. 
But, reading your comment re the piston skirts, I wonder if the cylinder has been bored correctly to suit the oversize pistons.  Do you know?
Just checking . . .
Cheers, Mike

Hi Mike,
I had brought the engine revision shop the old piston that had little pieces broken off, and the two, scratched cylinders, and had them do what they had suggested: find a supplier of new, slightly wider pistons for this particular engine (given the type, model and engine number) and hone the cylinders accordingly.

When I later picked up the new pistons and honed cylinders, how could I expect the clearance then to be not OK? It was their suggestion to do it like that, and their job to do that right, wasn't?

I don't think I did anything wrong, with the reassembly, or it was that it didn't come up in my mind, that I should find a way to check if they'd done the job right.
I think... but correct me when I'm wrong.

« Last Edit: October 27, 2018, 11:54:10 PM by Rob PetterPJ2 »

glort

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #58 on: October 28, 2018, 01:43:52 AM »

To me, checking clearances and Gapping rings would be as fundamental and basic as putting gaskets in. Mechanic that workd for my father is always saying and PROVING, " Just because it's new, Don't mean it's good". Yes, the engine re conditioners should have made sure the clearances were right and this is why YOU need to check them.  In the end, the responsibility ALWAYS lies with the guy assembling  the engine not the guy that supplied the parts. Anything wrong should be picked up during the build. I'm not trying to give you some highbrow industry rules or culture here, it's really just the way it is and logic.


The fact you weren't aware of checking clearances is why I think it would be a real good investment  to have someone look things over for you to make sure there are not any other problems you might be missing that will save you much more money to take care of now rather than later.

Sometimes the ultimate shortcut is not to take any at all and go the long and through way round.  :)

Rob PetterPJ2

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Re: New pistons Petter PJ2, block after short time engine running. Clearance?
« Reply #59 on: October 28, 2018, 12:30:55 PM »
Yes, the engine re conditioners should have made sure the clearances were right and this is why YOU need to check them.  In the end, the responsibility ALWAYS lies with the guy assembling  the engine not the guy that supplied the parts. Anything wrong should be picked up during the build.

ASSEMBLY GUY's FAULT...
Dang, that's what I once told a publisher who had the emailed LOW RESolution example of my illustration printed on a book cover, instead of the high res, sent on a CD together with the typography and the design. 2000 books were printed with low res cover, not showing the fine details I'd put in. I said the production leader screwed up, for not noticing the mistake, that those who assembled it, had made. So, I get the point you make.

But still, what were the honing guys thinking?
When the engine seized after the first two tests, I wrote them an email about it, asking them what could have made the engine seize. All they replied with was: "A pity it didn't work out as we'd planned".

OVAL shaped PISTONS, or not?
I've also been measuring and measuring, over and over again, both the old pistons and if there's a difference between the longer and the shorter diameter of the oval, it's not more than 0.05 mm, which is 0.00197 inch, roughly 0.002".
The Lister LD manual I have doesn't say anything about the oval shape, when measuring the piston clearance doing maintenance. It just says: "measure it, it should be not less than this".
Could it be, that with these old engines, the oval shape wasn't yet invented, or that it isn't applied for every engine? Or is the 0.00197 inch difference in length and width of the oval shape about the expected margin?

DAMAGE TO PISTON
Here's a picture of the damage to Piston 1. It has similar damage at the opposite side. The grooves rubbed off, here.
Piston 2 has tiny traces of damage. The grooves still there, and all around.
« Last Edit: October 28, 2018, 03:09:15 PM by Rob PetterPJ2 »