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SimonBrown

8 Cylinder Torpedo Engine - Restoration

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I'm really puzzled by the internal thread in the gudgeon pins. Don't recall seeing anything like that before, and can't see any purpose to having it there, especially if they are pressed in.
The brass ends of the pins look to be very big in relation to the pistons and con rods, so I'm wondering if they are just end caps or bushes? Something like this: https://blog.wiseco.com/what-are-wrist-pin-buttons

Could the brass ends be externally threaded too, and held in place with the split pins?

The internal thread could be there to facilitate installing them. Not sure how they could be got out if they are threaded though?!?

Worth investigating before you try pressing them out.

 

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1 hour ago, MatchFuzee said:

If you put it to a readers' vote, mine would be "leave the patina". 

Duly noted!

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56 minutes ago, Johnny said:

I'm really puzzled by the internal thread in the gudgeon pins. Don't recall seeing anything like that before, and can't see any purpose to having it there, especially if they are pressed in.
The brass ends of the pins look to be very big in relation to the pistons and con rods, so I'm wondering if they are just end caps or bushes? Something like this: https://blog.wiseco.com/what-are-wrist-pin-buttons

Could the brass ends be externally threaded too, and held in place with the split pins?

The internal thread could be there to facilitate installing them. Not sure how they could be got out if they are threaded though?!?

Worth investigating before you try pressing them out.

 

I did promise a while back some photos of the gudgeon pin-less design. Its not easy to get your camera in - even a slim one like an iPhone - but here goes...

Two bronze or brass caps are pressed into the piston and retained via a split pin. The brass caps extend deeper than the piston skirt and into the area under the piston crown. The caps are fixed and do not rotate, but are machined with a large flat on the side facing into the crankcase:

SBrown-20190404-0003-2.jpg.035452aa568b96bf5076a6c8b05cb4fc.jpg

Under the crown of the piston and fixed to the top of the con rod sits a solid bronze semicircular shaft that extends beyond the con rod and over the brass caps. The semicircular shaft is machined so that the piston can rotate about this shaft on the brass caps.

The internal Admiralty threads may be there for no purpose other than to help in a manufacturing process?

The load from the piston appears to be transferred to the con rod directly to the semicircular shaft and the brass caps are then to keep the con rod in place, but transfer no load whatsoever on either the induction, compression or power stroke.

Is like nothing I have ever seen before and the conclusion is space was at such a premium they dreamed this up to reduce the overall diameter of the engine. I would imagine it might clatter a bit when running...which seems odd as sound travels well underwater and it might alert a hydrophone operator something was starting up...thats guesswork at the moment though.

How it comes apart - if it ever can - is today's conundrum. Right now I'm fairly relaxed as underneath the crowns looks clean and lubed, and no corrosion. 

 

SBrown-20190404-0005-2.jpg

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How strange!!

Could you make up a puller to remove the bushes using the internal thread?

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Looking at the underside, the 2 brass pins cannot have external thread on them as that is a bearing surface, so it looks like they are pressed in from either side, with the internal thread for extraction. the oil jets in the crankcase are obviously aimed at that oversized  bearing surface! 

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Posted (edited)
1 hour ago, Longen said:

Beautifully designed and engined.

Isn't it just? A real joy to work on, if a little fiddly at times.

13 minutes ago, terryb said:

Looking at the underside, the 2 brass pins cannot have external thread on them as that is a bearing surface, so it looks like they are pressed in from either side, with the internal thread for extraction. the oil jets in the crankcase are obviously aimed at that oversized  bearing surface! 

 

1 hour ago, Johnny said:

How strange!!

Could you make up a puller to remove the bushes using the internal thread?

A puller has occurred to me. There might be risk of the caps being pressed in so tight the threads strip, but a puller could work. For now, and unless I can find a good reason, the pistons will stay on their con rods. 

The true purpose of oil feed into the cylinder is not something I had considered, but the idea its spraying over the little end bearing sounds perfectly logical and given the power output absolutely necessary. I will have a look at it again when next in the garage.

Edited by SimonBrown

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5 hours ago, MatchFuzee said:

If you put it to a readers' vote, mine would be "leave the patina". 

For me it would depend on what you want to do with it.  An exhibition piece might look better replated.

Andy

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Not much progress of late, but things are cleaning up nicely and the gummy preserving oil is coming off a treat.

SBrown-20190414-0007.jpg.368b7c36cb1f363630a5872a529d3f96.jpg

On the right, pot No 3 cleaned and lightly lubed and on the left pot No 4 waiting its turn. Most of the pistons have some light scoring on the skirt but nothing to worry about. A scrub with degreaser is shifting the muck and the rings are now free to move in the groove.

Barrels have been given a dunk too:

SBrown-20190414-0008.jpg.47fbfe2f72171a3427c9fbc87ca86f58.jpg

And the bores are pristine:

SBrown-20190414-0010.jpg.b13a73ffc8aa28fb46ce060d027a1f66.jpg

Note the two oil grooves halfway up the bore. Only one is pressure fed via the external pipes, with the other not aligning to any oil way I can see.

Thinking about the big end...if it ain't broke don't fix it springs to mind. Its clean, rust free and rotates smoothly. Plus another special spanner is needed to get to the large nyloc holding the big end together.

So I'm inclined to leave it and clean/reassemble from this point.

Its still a work of art though. Heres a side view:

SBrown-20190414-0003.jpg.9ed2ca32a600165191b7f7b86e6a3976.jpg

I think the 'F' stamp stands for 'Front' but I will know when I turn it over and see if the rear set of con rods are stamped.

Here's a view looking down:

SBrown-20190414-0006.jpg.a59483edb93b6ba425a634148fd53aa8.jpg

You can just see the big end nut above the main bearing. Here's a closer view:

SBrown-20190414-0005.jpg.d6de7efd0272657dd16ea636d51f2b95.jpg

Access is tight and I think a standard socket and extension is going to clash with the square section next to the main bearing.

Its such a compact unit. Quite remarkable the power output crammed into a 21" diameter tube. The pan head screws are treated to a dunk in the ultrasonic degreaser before having a die nut run down to clean the threads and the inlet valves are coming up brand new. Takes about an hour per pot to fully degrease, with 3 down and 5 to go.

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Simon,

 

I am very happy to make another special tool.  Perhaps a cranked 12 " extension?

John

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Hi

Torpedo engines are 2 stroke diesel, When running "Hot" the fuel air mixer has ignited, (using an ignitor) Suppiled in individual pressure tanks (so no injector pump, just a distributor,) oil is also in a pressure tank.

when running "cold"the fuel has failed to burn, and so is running off the compressed air supply, and unburnt fuel.the range is about halved,

oxygen torpedoes were used but did explode.

electric torpedos we are used to day.

regs

Rupert

 

 

 

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Posted (edited)

Progress has stalled a bit as I have been busy on other things Scapa Flow related. A week of frustrating-at-times diving proved useful with a few new finds, plus documenting stuff like the Anti Torpedo Close Protection Pontoons at Flotta:

3D model of a pontoon.

But I shall be back on the torpedo engine tomorrow - fingers crossed.

I have also taken a close look at an 18" example recovered from the sea. Its in a bit of a state but could be worth preserving. The steel has gone but lots of bronze parts remain. On the 18" engine the cylinder heads were steel and have rotted but it did mean I got one of the set-circular gudgeon pins out of the bore without so much as touching a spanner...

SBrown-20190503-0001.jpg.968f9a853ea3dfa2f21c603bdf5a6bad.jpg

SBrown-20190503-0004.jpg.6a1fdaec318b2d55f8e6ec2dcb105973.jpg

The rust is all that remains of the con rod. It crumbled like dust so not sure this one will be a runner again soon...of note was the piston ring. They are made of bronze and have survived well, if a little caked in rust. 

 

Edited by SimonBrown

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Interesting project! 

This engine is not a Diesel engine, it works like a steam engine: gas is supplied under pressure and expands in the cylinder. The compressed air from the reservoir is heated and greatly increased in volume by burning some fuel in it (at an intermediate pressure) in a combustor. This hot gas is what this motor is running on.

The inlet valve has the very thick stem because the inlet gas is at quite some pressure. This pressure produces a force acting to push the valve open that is proportional to the area of the back of the valve minus the cross sectional area of the valve stem so a fat stem much reduces the required valve spring strength.

Have a google of air motor and hydraulic motor images for some vaguely similar mechanics.

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Automotive 2 stroke engine rely on a blower to supply air and scavenge the spent charge from the cylinder . The torpedo carried air at up to 3000psi which was supplied to the engine at approximately 800 psi as I understand it . Hence no need for a blower.

I am currently playing with a 4 cylinder unit and trying to make out what it is . It is stamped " P Brotherhood's Patent 1" and then what could be a date stamp in very small print 17.8.18 .Could it be a hot air engine ?

Howard Cogan

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Posted (edited)

Hi Howard,

P. Brotherhood is probably Peter Brotherhood, by 1918 Peter Brotherhood Ltd.

He appears to have been applying for patents from 1874 onwards, was certainly iterested in all aspects of steam engines, governors, compressed air, superchargers, torpedoes,  aero engines and internal combustion engines, to name a few subjects. I could not find a patent with a 17/8/18 date, but hopefullly, here is a list of his patents you can look through.

https://worldwide.espacenet.com/searchResults?submitted=true&locale=en_EP&DB=EPODOC&ST=advanced&TI=&AB=&PN=&AP=&PR=&PD=&PA=peter+Brotherhood&IN=&CPC=&IC=

The company apparently still exists, working in the same fields.

https://www.peterbrotherhood.com/

Best Regards,

Adrian

 

Edited by Le Prof

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I have been doing a bit of research on another Brotherhood item, being a Brotherhood-Crocker car c.1904.  It is a 4 cylinder T-head engine, but interesting to note that the Brotherhood logo was based on their 3 cylinder radial design that could be adapted to either being a pump / compressor or a motor.  The early 3 cylinder torpedo motors are straight Brotherhood designs.

A photo of the car engine is included for interest sake.  However, no evidence that it was used in a military application...yet.  Brotherhood did design some very innovative features for the car engine.  Most of the car and engineering journals at the beginning of 1905 have large articles on the engineering side that can be seen using Graces Guide if you are curious.  A lead on any parts for a Brotherhood car engine and gearbox would be much appreciated.

But back to the main subject, - out of the blue, I have also been offered a Japanese torpedo engine for the museum.  It happens to be an 8 cylinder radial unit with an 18 inch diameter.  This was a bit of a surprise, as I have not seen any references to it.  The Japanese definitely produced the Whitehead long stroke 2 cylinder designs for their 18, 21 and 24 inch torpedoes, so where an 8 cylinder radial for an 18inch fits in, I do not know (other than very tightly).The present owner was a salvage diver after WW2 and recovered the torpedo.  He has had the motor running on compressed air, so he says.  I will be following it up.

ATB,

DNA

brotherhood engine1.jpg

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On 22 December 2018 at 4:46 PM, SimonBrown said:

I did have an electric Mk44 air dropped torpedo for a while and connected the motor up to a car battery to see if it was still viable. The contra rotating props worked a treat. But the missus drew the line at an intact, complete and functioning (less the warhead and original battery) torpedo in the garage,

What a Strange Woman......., but something in Common with mine, as mine doesn't like a Bren Gun in the living room but is happy with Grenades on the bookshelves.........

Certainly a talking point if you got it going,  I'd build a torpedo around it. 

Got me thinking back to when I was an Apprentice Fitter in a certain Shipyard, I did a lot in the Torpedo rooms of HMS Trenchant and HMS Talent, setting up the torpedo load lines etc, worked in the tubes too (I was a bit thinner back then).

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On 5/24/2019 at 8:44 AM, rory57 said:

Interesting project! 

The inlet valve has the very thick stem because the inlet gas is at quite some pressure. This pressure produces a force acting to push the valve open that is proportional to the area of the back of the valve minus the cross sectional area of the valve stem so a fat stem much reduces the required valve spring strength.

Excellent thinking on why the valve stem is so fat...and whilst I think the reasoning is spot on, its worth bearing in mind the design of the engine.

The inlet valves work the other way around to any normal internal combustion engine; The flat face of the valve would typically face the combustion gases. Not so in this engine...here the inlet gases are pressing against the flat face of the valve...so the large diameter spring is actually holding the valve closed during combustion/power stroke and the expanding gases inside the combustion chamber. Inlet pressure alone  is exerting a force that would hold the valve shut in this case.

Did that description make sense? Have a look at the photos in the 1st March post here:  Inlet valves etc

I hadn't realised just how unusual this is, until your really thought-provoking post rory57 - so many thanks for that. The more this engine is understood, the more whacky it gets.

Quote

The torpedo carried air at up to 3000psi which was supplied to the engine at approximately 800 psi as I understand it . Hence no need for a blower.

So far, everything I read hints at an inlet pressure of 160psi as supplied by the air tanks, regulated down from the 3000psi or so they were charged to. Interesting, as it appears there was a shift in design thanks to improvements in the strength and quality of steel to hold progressively higher pressures. More reading needed.

Quote

But back to the main subject, - out of the blue, I have also been offered a Japanese torpedo engine for the museum.  It happens to be an 8 cylinder radial unit with an 18 inch diameter.  This was a bit of a surprise, as I have not seen any references to it. 

Now that does sound interesting - got any pictures yet? That would make the number of 8-cylinder torpedo engines I know of go from 2 to 3 and it would be great to see what it looks like. My engine measures 20" over the cylinder heads, leaving just 1/2" as a sliding fit into the torpedo body. Be interesting to know what the 18" actually measures?

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On 7/10/2019 at 10:31 AM, David Herbert said:

Odd chaps, women !

David

Still looking for the operation manual 

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