Author Topic: Corliss Valve Duplex Triple Expansion Mill Engine  (Read 2077 times)

Offline propforward

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #30 on: July 23, 2018, 04:41:29 PM »
Superb shop - and that Burrell is absolutely beautiful. Thanks for sharing!
Stuart

Offline Jakdaw43

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #31 on: July 23, 2018, 06:35:20 PM »
Hi All,
The pic of the boring/chambering tool didn't materialise...so I'll try again.... :atcomputer:
Sorry, not a very good pic...but you can see the idea................
Cheers,
Stuart
Stuart alias 'Jackdaw'

Offline Jakdaw43

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #32 on: July 30, 2018, 10:43:55 AM »
Hi All,
Next I decided to make the low pressure cylinder...not having a gunmetal casting for this, I fabricated it up silver soldering the parts together.
The main cylinder body was machined up from a chunk of cored gunmetal (LG2) that I had to hand....never look a gift-horse in the mouth !!  The finished diameter is 2.218; the length 3.875".
Set up in the lathe I turned the outside diameter(s) holding the chunk  with inside jaws on the cored bore....I held the outer end on its cored bore using a 3-jaw chuck on a ball-bearing spindle in the tailstock.
I roughbored it 0.040 undersize on the bore including the  counterbores each end where the covers sit.
To make up the blocks  that form the port-face and underside support I milled gunmetal blocks then mounted them on the vertical slide and using a between-centres boring bar cut the scallops to fit the cylinder mid-diameters..
The remaining parts, bottom bolting plate, support webs and bosses for the draincocks were made up from brass plate (BS249) machining brass.
The parts were held together by bronze screws down the exhaust port and up through the centre of the bottom plate.  The webs and bosses held by jamming or soft iron wire.  The assembly was fluxed up all-round and silver soldered with Silverflow 55.
After pickling clean the cylinder was set up in the lathe once more....the bore and counterbores were  finished and the ends faced.
The covers were machined up from continuous-cast grey iron bar drilled for cover studs using the toolpost drilling spindle (with chuck backplate detent), as were the tapping size holes (6BA) in the cylinders.   The holes  were tapped quickly using one of my Geo. Thomas tapping/staking machines.
I hope the pics are self-explanatory...
Cheers,
Stuart


« Last Edit: July 30, 2018, 10:47:29 AM by Jakdaw43 »
Stuart alias 'Jackdaw'

Offline Jakdaw43

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #33 on: July 30, 2018, 10:46:37 AM »
Low pressure cylinder Pics continued...
Cheers,
Stuart
Stuart alias 'Jackdaw'

Offline scc

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #34 on: July 30, 2018, 01:08:41 PM »
Excellent work!  I'm watching and learning :popcorn:   Thank you for posting in detail.              Terry

Offline Jakdaw43

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #35 on: August 04, 2018, 04:23:44 PM »
Hi All,
Thanks Terry for your comment; if it helps someone, maybe even provoking a thought, then it makes it worthwhile.... I must have learned something worthwhile in over 60 years in the workshop !!
As a little aside I thought I'd show a couple of workshop 'machines' that help with accuracy as well as in production rates..
When it comes to items such as cylinder covers, glands and flanges etc., that have an array of bolts/studs one of the  basic methods to gain accurate pitch circles/divisions is to have some form of indexing system.  Rotary tables/ dividing heads/ and using digital read-out are amongst other methods.
 A far simpler, easily accessible  means is using an indexer attached directly to the main machine in the workshop, your lathe.
Some years ago I 'standardised' my chuck threads used on the lathe, dividing head, rotary table chuck, and indexer to that of the lathe... 1.5" dia x 8tpi w/f....thought that a logical step.  :old:
I took a little  time one afternoon to drill the periphery of all my chuck backplates with 48 holes with a BS4 centre drill using the dividing head.  This will allow common useful factors such as 2, 3, 4,6,8,12 .
A swing clear arm attached to the headstock of the lathe can position the spring-loaded detent over the chuck.  Thought...when the detent is in place DON'T SWITCH ON THE SPINDLE MOTOR !!    :'(
I've done it several times !!!!   It also pays to mark the  indexing steps on the hole circle using a felt-tip pen to aid repetition mistakes.   6 hole steps gives 8 holes positions on pcd. etc..
Using the toolpost drilling spindle, the spindle bore of which was drilled/reamed/ bored in situthus ensuring accuracy.  The centre/start-point is easily attained by placing a centre in the t/stock and parallel centre in the chuck to line up .  The pitch circle radius can then be set by using the cross-slide feedscrew, a rule, or digital read out whathaveyou.
The spindle is driven by a 80watt sewing machine motor and I put a domestic dimmer switch on the supply to give speed control.....I only hope I can get the motor back on domestic managements sewing machine before she decides to use it next!!
I usually put a BS1 centre drill in the small Jacobs chuck and 'spot' the locations....drilling for tapping size/clearance as appropriate on the drilling machine.  All the cover, flanges and glands were done like this.
Although I have an Archer No2MT tapper , it is often easier to tap the holes using part of my George Thomas (of hallowed memory) tapping attachment...it gives vertical guidance and very good 'feel' for small taps such as 8BA.  I've attached a pic of the 'tapping' machine and next to it one of the developments George made for closing small rivets.
I hope the attachments help explain my ramblings  :atcomputer:
Cheers for now, Stuart
« Last Edit: August 06, 2018, 07:28:18 AM by Jakdaw43 »
Stuart alias 'Jackdaw'

Offline Jakdaw43

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Re: Corliss Valve Duplex Triple Expansion Mill Engine
« Reply #36 on: August 23, 2018, 03:45:11 PM »
Hi All,
Just returned from 10 days in South & Mid Wales, which ended with a trip up the Vale of Rheidol railway, by accident  of course !!
Back to the Duplex Corliss....
The castings I had to hand included the high and intermediate pressure cylinders, both in LG2 gunmetal.
These will eventually be chemically blackened and grey iron end covers fitted.
The blocks were milled all over with a face mill; then the cored holes thin plugged with aluminium and the centres of the bores set out using the surface plate/height gauge.
The castings were then set up in the 4-jaw independent chuck and the centre dot set to run true.( Use a tailstock centre and a second full centre supported between bore centre dot and tailstock centre; use a dti on the large diameter of the follower centre, adjusting the chuck jaws to suit)
The bores were roughed out and then finish bored  to size ( 1.125dia. HP;  1.625dia. IP)
The live steam and exhaust chambers were slot drilled into the top and bottoms of the castings and the Corliss rotary valve bores marked out and drilled and reamed  to size. (5/16" dia. HP inlet; 3/8" exhaust.  IP cylinder 3/8" inlet 7/16" exhaust)
The ports are cut from the bottom/top of the chambers to meet the Corliss rotary valve bore on centre line.  It required a !" dia x 0.090" wide saw type cutter (like a Woodruf)....a size I did't have....so I made one up from silver steel (drill rod to those across the pond).    I turned up the blank to tooth dia. spec., turned a shank on it to fit the ER25 collet chuck then using the indexer head on the miller formed eight teeth with primary and secondary clearances.
The chest cover plates were made up of gunmetal off-cuts...stud holes drilled/threaded  with provision for steam studded flanges and exhaust below with nut/olive....out of sight in the baseboard.
The Corliss valve spindle bonnets were turned up from phos. bronze; stud holes indexed and drilled using the toolpost drilling spindle/chuck indexing system in each bonnet and covers and the stud threads drilled and tapped into the blocks.   In this case, as there were 192 8BA holes to tap I used the Archer machine tapper in the drilling machine, much easier !!
Pics. attached.
Cheers Stuart
Stuart alias 'Jackdaw'