Author Topic: Repairing a high quality model marine engine  (Read 54945 times)

bogstandard

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Repairing a high quality model marine engine
« on: April 18, 2009, 07:23:08 PM »
A few of you might remember a project that I had mentioned that had come into my workshop.

A very high quality marine steam engine.





Well I contacted the owner to see if it was OK to show my refurbish on the site, as I thought it would be a nice change to see what happens to these old but well made engines, and he very kindly agreed.

I will just explain how things work.

Unlike when you do work for yourself, where you can just do things as you want to get the job done.
When you do something for someone else, they are relying on your expertise to do a good job, and give them value for money without ripping them off.
After being a marine modeller for well over 40 years, I understand exactly what it is like, entrusting your pride and joy into the hands of a total stranger. Hand it over to a cowboy and you will be in trouble from the start and most probably pay thru the nose for the privilege. What I do is come to an agreement on rough costs at the very beginning (I give a substantial discount to fellow modellers), and keep the customer updated if it is to be a long job.

So basically the engine came to me with a list of faults, and with instructions to get it working to the best it can be.

What I do initially is totally ignore where the problem is liable to be, and give the engine a good going over.
The engine came with a requested set of plans, so if any faults on the mechanical side shows up, I should, without too much trouble, be able to remake any parts that are required.

So I went all over the bottom end of the engine, and soon came to the conclusion that this engine had been made by a very experienced craftsman. No corners had been cut, and it was made to a great standard, and no wear or faults could be found anywhere. It goes to show, if an engine is made well and looked after, they are bombproof and will last forever.

So once I am satified that no other work is required, I then concentrate on the problems that the customer has listed.

In this case, a gasket had 'blown' and steam was leaking everywhere, plus he would like the timing 'put' right.

Blown gaskets are a common fault and normally people just replace them, and carry on until it blows again.
I don't like that idea, if a gasket has blown, there is usually a reason for it, and I soon start to find the problem.

These next few photos show what I found.

The first thing that I noticed was that the top end on the valve area was held together by slotted screws. Normally studs with nuts and washers should be used, and with checking on the plans, I was shown to be correct on my assumption. I suspect that sometime during it's long life, one of the gaskets had blown, and someone had replaced the originals with brass screws. Or the original builder didn't get to finish the engine off, and someone with lesser knowledge had taken over the finishing off. But unbeknown to them, screws cannot be tightened down enough to make the gasket stable, and so it will just keep blowing. I will be putting it back to original, how it should be.

So now to disassembly.
This is the main steam face, and was sealed with some sort of compound instead of a gasket, and later pictures will show what it had caused.




This is the steam chest and slide valve off this end of the cylinder block. Also shown are some very hard remnants of the gasket goo




This is off the opposite end, which hadn't blown, but it also showed another problem.




You can see on this shot how hot this end must have been running, it has actually 'blued' the surface of the brass, and by the looks of it, the gasket was very close to blowing.
Only assumptions can be made of the cause of this problem, ranging from loss of lubrication and very high temp steam or air entering the valve chest, or what I suspect, this end of the engine is very close to the boiler. I will advise the owner to make up a small shield to go between the engine and boiler to try to keep the heat down.




Both faces were gently cleaned off, and it shows the damage on the face, both ends were scored by the same amount. I suspect this has been caused by fragments of gasket goo being trapped between the sliding faces. The deep score is about 0.002" deep. That is a massive groove when put into the context of a finely lapped sliding steam face. It will also account for the lack of power and the assumption that the engine timing is out, this scoring will allow exhaust and pressurised steam to go anywhere it wanted to.




After a lot of tedious hand flatting and lapping, both faces were brought back to a perfectly flat faces. Before final assembly the slide valves and the faces will be lapped together to get gas tight seals.




One slide valve has been cleaned off, the other is about to get the same treatment.




While I am at the top end poking about, I decided to take the cylinder caps off. These again were sealed up with liquid gasket. As luck would have it, the internal spigot had stopped any going down into the cylinders and causing any damage. Just general gunge in there which was cleaned out.




Without a full bottom end strip down, I can't check the whole of the bores, but I will check what I can.
No sign of any ovality, and both bores measure exactly the same.




I checked for taper in the bore, with the same very good results.




While I am working on the engine, I am also on the lookout for areas where problems might occur in the future.
I will be making a full set of top end gaskets from PTFE sheet. This is a great substitute for the old waxed paper product, and shouldn't break down over time like paper does. I was a little worried how thin the steam covers were, even though they were made to drawing. So I knocked up a couple of new ones out of thicker material. It was then that the suspicion that someone else had taken over the finishing of the build on this engine. Everything on the engine had been built to superb standards, except this top end, the bolt holes were at different pitches, and it took me quite a while of measuring and calculation to make a pair that would fit either end.




Also, I will be fitting studs and nuts instead of screws, so I had to check that no overhang would take place when they were fitted, the one on the right is how it will look. I tried the same thing on the cylinder covers, but because of the way they have been made, they will go back on with just hex head screws with no washer.



So now I have the covers made, I can use them for the patterns to make the gaskets up.

To be continued

Bogs
« Last Edit: April 19, 2009, 05:22:55 AM by bogstandard »

Offline Mustang

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Re: Repairing a high quality model marine engine
« Reply #1 on: April 19, 2009, 12:39:57 AM »
Very interesting as usual John. Waiting to see the rest.  :thumbup:
Andy

Offline John Stevenson

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Re: Repairing a high quality model marine engine
« Reply #2 on: April 19, 2009, 08:07:56 AM »
What size is that bore gauge and where did you get it please.

JS.
John Stevenson

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #3 on: April 19, 2009, 08:27:33 AM »
John,

It is out of a cheapo Chinese set, it is spring loaded, push down the bore, tighten up the end which locks the bottom rods, withdraw and measure with a mic. I have found them to be very accurate.

Down a bit on this page

http://www.rdgtools.co.uk/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2frdgtools%2eco%2euk%2f&WD=gauge%20bore&PN=EVERYTHING_ELSE_MEASURING%2ehtml%23a620#a620

If you are after something for measuring very small holes, I have something that will do up to about 7mm, super accurately. Give me a call if interested.

John

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Re: Repairing a high quality model marine engine
« Reply #4 on: April 19, 2009, 09:26:21 AM »
I love to read posts like this. Very interesting and very educational.

Thanks John!

Eric
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Offline Stilldrillin

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Re: Repairing a high quality model marine engine
« Reply #5 on: April 19, 2009, 12:31:59 PM »
This is another crackin` post John!  :headbang:

Thank you......  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Darren

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Re: Repairing a high quality model marine engine
« Reply #6 on: April 19, 2009, 01:52:44 PM »
Thank you for showing this wonderful little engine repair John  :thumbup:

I would never have guessed that these engines run under such arduous conditions  :bugeye:

Just like a real engine, I'd never have thought it  :scratch:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline John Stevenson

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Re: Repairing a high quality model marine engine
« Reply #7 on: April 19, 2009, 02:09:03 PM »
Thanks John,
Now I look closer it's bigger than I thought.
I have the set of telescoping gauges but I thought at first this was smaller than the smallest in the set I have, if you can follow  ::)

JS.
John Stevenson

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #8 on: April 19, 2009, 02:42:28 PM »
John,

PM sent.

Darren,

On these types of engines, everything works and operates the same as the full sized ones, including all the related problems. On say the more complicated ones like a triple expansion, they can even condense the water out of the used steam to be reused, just like the real thing.

John

No post tonight, as I am half way thru cutting all the gaskets.

Offline Divided he ad

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Re: Repairing a high quality model marine engine
« Reply #9 on: April 20, 2009, 02:59:53 AM »
Looking Good John  :thumbup:


You having fun?  :)


I know this is more than likely giving you a hint on how to suck eggs, but.....

If you have to use screws (bolts) on the head? Then a little bit of oil (on the cars also copper grease)under the head of and on the thread of the screws (bolts) greatly improved the tightening of the head, it allowed angular torque to be applied far easier than if the parts were clean and dry.....Allowing a tighter bolt with less stress all round!
A little obvious I know, but it doesn't hurt to say it out loud! ::)



I have missed most of my weekend so will hopefully catch up with all this now as it unfolds?



Ralph.
I know what I know and need to know more!!!

Offline sbwhart

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Re: Repairing a high quality model marine engine
« Reply #10 on: April 20, 2009, 03:30:02 AM »
Nice one John  :thumbup:

Stew
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Location:- Crewe Cheshire

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #11 on: April 20, 2009, 08:50:45 AM »
Following on from the last time, where I was making gaskets.

They do take a fair amount of time to hand cut well fitting gaskets, so I have managed all that need to be done at this time. I do have some more to do on the steam valve, but they can be done when needed.

So here is the kit, a scalpel, a couple of hole punches and a hole jig for each type. The jig for the square one was made from the now redundant steam chest covers, and the circular one was made from a piece of 10mm PVC. I always cut extras, just in case I tear one on assembly, plus any that are left over are sent to the customer in a little spares pack when the engine is returned.
Two thicknesses of PTFE are used, one at 0.005" and the thicker at 0.010". Where the gasket cement was used will get the thinner material, while the main gasket on the steam chest will get the thick ones.
I have used PTFE for a few years now, and found it much superior to the old paper gasket. I have even made head gaskets for IC engines with no problems at all. All the little offcuts are saved, to be used for smaller gaskets, as it is rather expensive to just be thrown away.




This is where the cylinder cap ones will go.
They look awful in this shot, but in fact they are quite round, on here they are all wavy and makes them look all out of shape.




The steam chest gaskets will fit like this.




If I feel up to it later, I will get all the studs made, and get the top end reassembled. Then it is just the steam connection pipe and control valve to do.


Bogs

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Re: Repairing a high quality model marine engine
« Reply #12 on: April 20, 2009, 08:55:23 AM »
Hi John

Where do you get that PTFE sheet from ?.

Stew
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #13 on: April 20, 2009, 09:38:58 AM »
Stew, I couldn't find a supplier in the UK when I wanted some. I don't know if anyone is doing it now.

I bought mine from the greatest shop in the world for bits 'n bobs

http://www.smallparts.com/

The only problem was the delivery charge, I ordered about $45 worth of bits but the small package they sent me came to over $60 in carriage charges. So I have never used them since.

Just search for PTFE sheet.

John

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Re: Repairing a high quality model marine engine
« Reply #14 on: April 20, 2009, 10:35:25 AM »
Stew, I couldn't find a supplier in the UK when I wanted some. I don't know if anyone is doing it now.

I bought mine from the greatest shop in the world for bits 'n bobs

http://www.smallparts.com/

The only problem was the delivery charge, I ordered about $45 worth of bits but the small package they sent me came to over $60 in carriage charges. So I have never used them since.

Just search for PTFE sheet.

John

There are some of us here in the states that could help 'assist' getting things shipped to the UK (or else where) for much cheaper. I have done that for a few people... CrewCab most recently. He ordered a bunch of stuff from Mcmaster and LMS , had it shipped to me and I sent it to him. Saving the huge shipping fee from LMS and he was able to get stuff from Mcmaster (who no longer ships out of the US for 'small' guys)

Eric
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bogstandard

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Re: Repairing a high quality model marine engine
« Reply #15 on: April 20, 2009, 12:22:57 PM »
Many thanks for the offer Eric, that is most kind of you.

If ever I need anything, I will let you know.

I have had massive shipments sent from the US for the bike, and they came to less than what Smallparts charged me for a little bag, and faster delivery as well.

But I have to admit, I could spend a fortune in Smallparts pages, they have almost everything I have difficulty finding anywhere else, all in one place.


John

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #16 on: April 20, 2009, 05:24:19 PM »
Just a tiny post this time, as I have reached a stage where the job has to stop for a few hours.

I am now doing the rebuild on the top end.
Part of this requires putting the engine back to how it should have been made, that is with studs, washers and nuts instead of screws on the steam chest covers. So that is what this post is about.

Not having any correct diameter material to cut the studding myself (which I would normally do), I actually bought some steel 8BA studding ready made. I cut 8 lengths at about 25mm (1") long. The length at this time isn't critical as it will be cut to exact length after the parts are all bolted together. After chopping up, both ends of each stud was ground up so that a nut screwed nicely onto it. This studding is about 2mm (1/16"+) diameter.




Using two nuts locked onto a piece of studding, the ends were dipped in some threadlock and then screwed all the way home in the holes in the main block.
After they were all in, the steam covers were pushed most of the way to the end. But not all the way, there will be some threadlock displaced during the cure, and I don't want the plates being bonded to the block. The reason for the plate being there is to keep all the studs in line while the threadlock does it's job.
The first job to do next time will be to clean off the unwanted threadlock that has appeared on the surface.



Tomorrow, if all goes well, should see most jobs done, then I can get onto retiming the engine. Having these studs in will really help, as it is easy to assemble everything accurately without the steam covers on, that, coupled with leaving the cylinder caps off, will make the job a lot easier.

Bogs

Offline HS93

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Re: Repairing a high quality model marine engine
« Reply #17 on: April 20, 2009, 05:56:35 PM »
Have you got the  paint yet ? Brunswick Green ( dark I think) I got some from Phoinix paints supposed to take heat.

Peter
I am usless at metalwork, Oh and cannot spell either . failure

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #18 on: April 20, 2009, 06:11:57 PM »
No paint required Peter, this is just a mechanical refurb and repair.

To have me strip it down and repaint it would cost the customer a lot of readies. It is easier for him to carry out the touch ups required if he wants to.

John

Offline Darren

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Re: Repairing a high quality model marine engine
« Reply #19 on: April 20, 2009, 07:37:01 PM »
Every time you tease us with this engine I can't help but to find it fascinating.

Thank you for all the "how to's". I look forward to every one of them  :thumbup:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #20 on: April 20, 2009, 11:52:02 PM »
Darren,

I really enjoy working on small engines such as this, especially since it was made by what looks like a true artisan (except for the top end, which I am now putting to rights).

After 40 years plus of use, this engine is getting it's first major service, so there is no reason to believe it won't reach it's second major overhaul if it is looked after well.

Some of the bits I am showing you on here will come in handy for when you get to assembling your engine. But yours being a different porting design, you can do away with the gaskets if you want to, and use Hylomar jointing compound.

John

Offline Darren

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Re: Repairing a high quality model marine engine
« Reply #21 on: April 21, 2009, 05:29:32 AM »
Thanks for the info, that will make life a lot easier at this/my early stage  :thumbup:

I've never enjoyed working in the workshop so much since finding this forum, well the machining side that is. The information gleaned has really helped me to get things going much more smoothly.

You were showing some small bore gauges, I have a set, an old M&W set that I've had for many years and it's just occurred to me that I can use them to size boring a hole  :doh:
Should make life easier to prevent going oversize  :ddb:

You see your posts give away so much.... :thumbup:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #22 on: April 21, 2009, 06:04:30 AM »
Darren,

I think I have said this before, a lot of the shots are set up. Most times, I try to include somewhere in the shot the tools that are used to do the job. As in the bore gauge, I put the mic in the background to show that is what I used to take the measurement off the gauge.

So it pays sometimes to look a bit further than the main item in the shot, not always, but most times.

I am just taking a break from the top end studding work, so tonight you will see some more progress.

It is going slowly, as I am still limited to the amount of hours I can do, but it is progressing, and it won't be long before it is ready to go back to the customer, if things carry on as they are doing.
I have noticed a bit of a problem with the internal valve gear, so I will have to knock up a couple of bits before I can do the final assembly and timing. Nothing major, just annoying, and will definitely cause problems if left as it is. All will be revealed.


John


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Re: Repairing a high quality model marine engine
« Reply #23 on: April 21, 2009, 07:10:37 AM »
   


   Hylomar jointing compound


       John is this the same as high temperature RTV silcone  sealant on this side of the pond?

   Ron

bogstandard

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Re: Repairing a high quality model marine engine
« Reply #24 on: April 21, 2009, 10:21:23 AM »
Ron,

Hylomar is a non setting jointing compound. I usually apply it with a fine paintbrush to both surfaces and then push the two parts together.

It is a world renowned jointing compound that was first used on aero engines, but because of its properties was also soon used in all areas of industry especially the automotive.

It must be available in the US, as we can buy it in our car accessory shops.

http://www.hylomar-usa.com/_resources/_html/products.html

A gooooogle search will soon give you everything you ever need to know about it.

John