Author Topic: newnes - a triple expansion engine  (Read 11138 times)

Offline peatoluser

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newnes - a triple expansion engine
« on: August 28, 2012, 07:30:31 PM »
this engine is based on the triple originally designed by O. B. Bolton, although Ive modified it so i can build it without using castings as well as altering things to suit my own tastes. Some of you may recognize it from the HMEM site, although it's been a while since I did anything to it. some DIY, holidays, changes at work etc. the usual stuff.  here it is at the present state of play.

I had run into a couple of head scratchers that I needed to resolve.
the first was how to build the  L.P. cylinder. It was difficult enough turning down the O.D. to 2 1/2" , that's the most I can swing over the saddle - i should point out  that I only have a peatol lathe, a small bench drill and a dremel.
the real problem was how to cut a 2 1/2" radius on the block that will have the steam passages in.
I tried making a boring head to give a big enough swing, but the lathe isn't rigid enough to allow the use of a  dovetail cutter and I couldn't find a commercial one that would fit the spindle.
So I think I did what a lot of people do, and started planning my next engine, and making a few parts to see if it is feasible.
then I realised that the solution was staring me in the face! - well it would have been if I had looked at the back of the lathe were all my home made fixtures are!
I had made a faceplate fixture to allow me to bore out eccentric sheaves. all I needed to do was to weld up another slide to accept some boring bars I had already bought.
here it is - I really need to get me some 6mm grub screws.
 
the set up really stretches the peatol - the boring bar clears the saddle by 0.002".

and a couple of hours later of careful feeding in the block

rough as hell finish

but what the hell - i need a capillary gap for the solder!


thanks for looking

peter
« Last Edit: September 30, 2012, 04:14:02 PM by peatoluser »

Offline Dean W

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Re: newnes - a triple expansion engine
« Reply #1 on: August 28, 2012, 07:34:39 PM »
Nice to see you here, Peter.  I've seen some things you've done with your Taig.  You're really good at working solutions!
Dean
In beautiful N. Idaho, U.S.A.

Shop Projects:
http://www.deansphotographica.com/machining/projects/projects.html

Online Dan Rowe

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Re: newnes - a triple expansion engine
« Reply #2 on: August 28, 2012, 08:17:50 PM »
Peter,
Yes nice to see you back at this engine. It is always amazing to see how you tackle problems and solve them with micro equipment only.

Dan
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Offline steamer

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Re: newnes - a triple expansion engine
« Reply #3 on: August 29, 2012, 01:45:56 AM »
That's really coming along Pete! :ThumbsUp:

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline FLG

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Re: newnes - a triple expansion engine
« Reply #4 on: September 06, 2012, 05:19:28 AM »
whoaa!! your work is really amazing!, as I started this hobby my goal was to build a triple expansion engine just like the one you are building, full of detail and realistic proportions/style!  :NotWorthy:

great work!

Saludos

Online Jo

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Re: newnes - a triple expansion engine
« Reply #5 on: September 06, 2012, 07:19:07 AM »
Hi Peter,

Wow I am amazed that you are building such a large engine on what is a relatively small lathe.

I like your faceplate fixture :LickLips:, I will adding one to my list of things I need to make for my Cowells Lathe ;D.

Jo
Usus est optimum magister

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #6 on: September 07, 2012, 05:44:26 PM »
Thank you all for your kind comments.
Jo , concerning the fixture, I tried to get the vee centrally  located as possible , and with a 1" bar clamped in it , I turned the outside of the slide to match the O.D. of the faceplate. That way , it's quite easy to set up, turn an eccentric, then use a vernier to dial in the offset.

back to the engine. I bought some sheet solder to braze the block to the cylinder, so as to save feeding a rod in. I was unsure about heating the job up to temp. but needn't have worried. everything flowed fine.
 
I scratched my head for a while as to making an expanding sleeve to hold the cylinder, but in the end I drilled and threaded an offcut of plastic (nylon, I think) 3/4 unf purely because it was  easy to use hand taps on it. I turned it down to be a wring fit on the bore.

I could then face the end of the block flush with the cylinder.


the next step was to make the cylinder covers (I still had the I.P. cover to do)
unfortunately , I managed to break a 7 B.A. tap when tapping the holes, so it's off to hunt down some alum (that is the right product isn't it?)  and hopefully I can dissolve it out.

thank you for looking

peter
« Last Edit: September 30, 2012, 04:16:15 PM by peatoluser »

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #7 on: February 24, 2013, 08:36:37 PM »
Hadn't realized how long it had been since I posted on this engine, DIY and an unheated shed being the main reasons.

with dissolving the tap, the alum powder worked spot on.

so lesson 1 :- when a tap starts feeling blunt  ,don't push it buy a new one. far less hassle than removing a broken one.
next up was the steam ports. just a case of the right size packing on the cross slide.


it was then I ran into another problem. I've based this on a published design that uses castings. as they are too big for me to machine ( and I'm too tight to part with 900 quid) so I'm quite freely making changes to it. one of them was to turn the LP cylinder round (valve linkage is then on the inside) and extend the gap between the LP & IP cylinders. unfortunately I make these changes on the hoof as it were, and didn't leave a big enough gap.
you can see the distance between the cylinders is not that great.


so lesson 2 :- when making modifications don't sketch them out on the back of a fag packet, at least use the back of a decent sized envelope.

it was a bit of a head-scratcher as to what to do. remaking bases and crank was not something I really wanted to do, but then machining the port face was going to be difficult on a peatol. I eventually came up with the idea of bolting the cylinder between two plates bolted to a shop made faceplate. if one plate is tightend to the face plate first. then the cylinder and second plate are snugly fitted to the first. then bolt second plate to face plate, clock in port face and tighten all bolts, I may stand a chance of reducing the depth of the port face. perhaps the photo explains it better.
 

Well, I was able to reduce the face. I now just need to re machine the inlet ports a bit deeper and drill the steam passages.


thanks for looking

peter

Online Jo

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Re: newnes - a triple expansion engine
« Reply #8 on: February 24, 2013, 08:59:44 PM »
Peter,

Nice to see some progress  :ThumbsUp:


so lesson 1 :- when a tap starts feeling blunt  ,don't push it buy a new one. far less hassle than removing a broken one.

....( and I'm too tight to part with 900 quid)  ;D


If you have a tap going blunt if you have a fine rat tail diamond needle file you can sharpen the tap by rubbing it down the slots. A friend does similar with dies using his dremel.

Jo
Usus est optimum magister

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #9 on: February 24, 2013, 09:13:46 PM »
Thanks for the tip Jo. I think my budget should run to a diamond file, especially if it saves me scrapping taps and dies

yours

peter

Offline Johnb

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Re: newnes - a triple expansion engine
« Reply #10 on: February 25, 2013, 10:26:13 PM »
Big job, little lathe. I like it.
John Browning. Member of Ickenham and District SME

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #11 on: March 04, 2013, 04:33:07 PM »
milling the steam ports deeper was straight forward. next problem was drilling at an angle from the end faces to meet the ports.
with the HP & IP cylinders I had milled a flat on the cylinder, and then milled the ports on the valve part before soldering together.
as here

but with the HP this was not an option ( the flat on the cylinder would have cut into the bore)
to help drill at an angle, I cobbled together a crude sine table from 5/16 by 4 flat bar and used  3" flat bar  to set the distance between some turned 1/2" rollers



worked out the angle, cobbled together some packing for the height and gave it a go. that's when the limitations of my cheap bench drill really come to light. there must be at least 2mm play in the spindle. I think mine must have been the first one off monday mornings production line after the mother of all chinese new years eve benders. i hope the sod had a hangover for a week.
I tried to use a slot drill (is that a 2 flute end mill on the other side of the pond?) to gently give me a flat on the edge before drilling the ports, but the machine was having none of it. it tried flipping the sine table , trying to push and pull the job this and that way. I eventually resorted to using my proxxon to grind a flat , then started gently with my largest center drill before drilling. eventually got it done. here's the set up.
   
the table is only locked by that 6mm nut you can see on the front hinge, so i do need to rethink this, but I'm definitely going to look round for a better drill.
the next step was to mill a groove by the holes for the steam. cobbled together a poormans angle plate and hacksawed a bit off the nylon mandrel I'd used to face the ends of the cylinder

then it was a case of bolting on the cylinder , feeding into an end mill, loosen, rotate a bit, feed in again etc. until it was done


did somebody post that all roads lead to Rome? well, I think I've found the one with all the  :censored: potholes!

thanks for looking

peter

Online Dan Rowe

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Re: newnes - a triple expansion engine
« Reply #12 on: March 04, 2013, 05:36:02 PM »
Peter,
Pot holes or not you are finding ways to get the job done.  :ThumbsUp: I always enjoy seeing your methods and set ups.

Dan
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Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #13 on: May 13, 2013, 12:29:08 PM »
Some of you may remember my attempts at making a reversing screw from that other site, but to recap for those who do not, here's the saga so far-
the drawings show a worm and wheel, but I think these are beyond my maching level, so I decided to use a simple scew reversing mechanism. now I could have just cut the thread with a die, but drawings of engines often show a coarse thread for fast movement, so I decided to have a go at screw cutting and make a coarse thread.
with no leadscrew or change gears, the only option was to use a follower system. first hurdle then was getting a follower. coarse threads mean large bolts and unable to get any I decided to make my own.
making my own meant I could decide on the pitch and - probably somewhat foolishly - decided on 8TPI twin start.
my first attempt then
I first marked of a length of bar with horizontal and vertical lines to give me 1/4 pitch

then tried to follow the marks with a triangular file and a crude cross bar was made


these were fitted to the spindle...

...and an attempt was made to cut a thread


note the toolmakers clamp holding the tool in place. i had placed a piece of 1/8 plate behind it. the theory being removing it would give me the correct ofset to cut the second thread.
the results weren't exactly brilliant. everything that could go wrong did. the bar twisted in the chuck, thereby loosing the mesh with the thread, the tool broke, the bar was being deflected, the 1/8 packing ,well, the less said the better. the result was a very drunken thread, but I was reasonably encouraged to rethink it and try and refine it.

 the problem was cutting the master thread. for the mark 2 version, I decided to make a guide and use a hacksaw to cut a spiral in some 5/8 bar.
I cut and rolled a piece of 20g plate that was a tight fit on 5/8 bar and gave me one turn of 4TPI . I case hardend the ends and used this as a guide for the hacksaw, cutting 3/4's of the way round, moving the guide, cutting etc. to produce a helix on 5/8 bar. I hacksawed a corresponding angle on a new connecting block and cut some stainless plate to use as a guide


and here it is all set up

I also made a sliding toolholder to help with the offset, and a quick and dirty travelling steady

here it is set up

and cutting the first thread by turning everything from the headstock hex. i had also decided to reduce the dia. of the screw from 3/8 to 7/32

I used a dti to offset the toolblock

and cut the second thread

a big improvement, the first one looks like me coming home from the pub, wereas the second at least resembles me going to it!

although something seems wrong with the offset - one thread is thicker than the other.
now I just need to grind a tool for cutting the nut and turn a blank and plan how i'm going to attach it to the columns - not out of the woods just jet

thanks for looking

peter

Offline steamer

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Re: newnes - a triple expansion engine
« Reply #14 on: May 13, 2013, 12:37:30 PM »
WOW!

 :praise2: :praise2: :praise2:

Well done!   

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!