Author Topic: newnes - a triple expansion engine  (Read 11116 times)

Offline swilliams

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Re: newnes - a triple expansion engine
« Reply #15 on: May 13, 2013, 12:47:24 PM »
Quote
a big improvement, the first one looks like me coming home from the pub, wereas the second at least resembles me going to it!

 :lolb:

Love the ingenuity you bring to this Peter. Really great!

Steve

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #16 on: May 31, 2013, 10:03:32 PM »
I now need to make the nut. but first , I need to grind an internal threading tool. given the size free hand was out , so I made a holder for the proxxon multi tool. then it was a case of mounting the small grinding wheels and thining down somw 3/16 tool steel. I used a cut-off wheel to get a sharp corner as the pink wheels are quit soft and left a radius

the rest of the tool was finished free hand - not the best preparation for cutting an internal square thread
 I faced of a square blank, drilled a tapping hole, set up the thread follower and began cutting the nut


it did cut , but I could visibly see the tool flexing, and i realised i would need better tool grinding facilities or come up with a different method

so i tried making a tap from silver steel ( drill rod) using the proxxon free hand to cut the flutes.

no way was it going to finish the threads and broke quite easily the first try.

having cut the male thread , I didn't want to give up just yet, so tried to think of another method.
having had some success removing taps I wondered if it would be possible to reverse the process as it were, and form the nut round a sacrifial stud, then disolve it out leaving the nut.
so I drilled out the blank clearance size, set up the thread follower and made a small stud.

I then dropped it into the nut blank and heated it up to a good red heat and then proceeded to knock the hell out of it with a 2lb hammer. As an anvil I just put a block of steel on the garage floor - there's no way my wooden bench would be up to it. sorry no photos - with hammer in one hand, pliers in other and torch in vice not possible.
I soon stopped as A) It wasn't doing the floor much good, and B) It looked like the bronze was splitting by the hole.

I tried drilling out the centre of the stud to give me less steel to disolve, but this was a mistake as it was difficult to hold the now mis-shappen nut square in the vice an the drill looked like it had wandered.

I then started to disolve out the mandrel using alum powder. It took the best part of a day . I ended up using about 2/3rds of a 100g bag, but i have no idea how to make up the solution - I just kept topping up the water and spooning the powder in whenever the stream of bubbles looked like it was tailing off.

I would take it out every now and then to check progress and see if I could loosen the bolt. eventualy I was able to get a punch behind it and twist the las bit out
here you can see the remains of the stud next to the nut.


the nut was a bit dissapointing. the drill hadn't wandered too much , but I hadn't been able to hammer enough bronze into the threads.

The nut tried to go on the threaded bar but was very tight - i had foolishly made the sacrificial mandrel the same size as the original bar, so there was vertualy no clearance on the o.d.
Eventualy, with the help of some timesaver lapping powder, I got it started and then merrily would wind it on a bit , back it off , on a bit etc. etc. and I began to make progress. Unfortunately I got carried away , wound it on too far and it locked up - not to worry - i'll just back it off. and then 40 odd years of using right hand fasteners kicked in , and instead of backing it off ( it's a left hand thread) I turned it the way you would to loosen a right hand thread , screwed it on even more, and sheared the bar. No point in stopping, so clamped the stud in the vice and carried on. I eventualy got the nut to run on what is left of the bar - in fact it runs quite freely .
hopefully I've posted the link to the video O.K.
http://s1184.photobucket.com/user/PEATOLUSER/media/NEWNES/DSCF0464_zps373bdcc7.mp4.html
7/32 O.D.  8TPI Lefthand twin start thread


all is not lost . the stud is repairable and I think there is enough depth in the nut to be usable. But I may remake them anyway.
For the nut, I'm thinking of casting it around another stud, and the maching / dissolving away  the excess as before.
And I would like to remake the stud and get the threads equal length.
I may be back in the middle of the woods, but this time I think I have found a path out!
 any way i have a couple of weeks to think it over as we are of to sunny Spain on sunday for two weeks!

thanks for looking

peter

Offline steamer

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Re: newnes - a triple expansion engine
« Reply #17 on: May 31, 2013, 10:07:49 PM »
Holy crap Pete!.....NICE!

I'd consider casting it too...but

You could make a series of tapered taps...if your a masochist....I figure you would need 3 to get to full depth


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

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #18 on: May 31, 2013, 10:17:13 PM »
Thanks for the comment Dave.
 in fact I did try making the taps undersize with a good taper - they were going into a partly threaded hole- but I think a combination of trying to put the flutes on free hand plus a square thread form and a steep helix angle, well it was always going to be difficult. I might have stood a better chance if I had rigged up some sort of milling fixture to cut the flutes. certainly an idea, even if only to clean up the cast threads.

peter

Offline steamer

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Re: newnes - a triple expansion engine
« Reply #19 on: May 31, 2013, 11:30:42 PM »
Pete
come to my shop snd use the Southbend
Anytime!

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

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #20 on: June 01, 2013, 06:24:44 AM »
The one you've been so diligently restoring!? Now THAT  is an honour!
Looking forward to it's completion. It looks like a true labour of love.

peter

Offline Bearcar1

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Re: newnes - a triple expansion engine
« Reply #21 on: June 01, 2013, 10:35:14 AM »
Very ingenious and way cool. What a thread to attempt replicating, but your perseverance paid off.  :ThumbsUp:


BC1
Jim

Offline steamer

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Re: newnes - a triple expansion engine
« Reply #22 on: June 01, 2013, 10:59:02 AM »
Very ingenious and way cool. What a thread to attempt replicating, but your perseverance paid off.  :ThumbsUp:


BC1
Jim


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

Offline ths

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newnes - a triple expansion engine
« Reply #23 on: June 01, 2013, 11:50:35 AM »
Hi Peter,

I enjoy watching this thread, seeing how you do a such remarkable job on that lathe of yours. It really is in the head.

I'm wondering where you got the name Newnes from, as it is a fascinating old mining ghost town to the north west of Sydney, and I am aware that the plans originate in Australia.

Cheers, Hugh.

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #24 on: June 01, 2013, 12:23:52 PM »
Hugh,
I got the name from a set of books i was given 'Newnes Marine Engineering' . the first volume dealt with steam engines and there was a drawing of a general style of bed plate used for steam engines. As I couldn't afford or indeed machine the castings, I changed the design of the bed plate to resemble the sketch - that way I could fabricate from 1/8 plate -  hence the name.

yours

peter

Offline NickG

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newnes - a triple expansion engine
« Reply #25 on: June 01, 2013, 12:52:00 PM »
Peter, I can't believe I've missed this but will be following from now on. Great advert for the peatol lathe, I recently nearly bought one - wish I had but instead took a punt on something else on eBay and ended up losing 100! Great work, set-ups and write ups.

Offline Don1966

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Re: newnes - a triple expansion engine
« Reply #26 on: June 02, 2013, 01:04:55 AM »
Hi Peter, I to have just finished reading you thread. The wonders you have been doing with a small lathe is fascinating. I will be following along with you.

Don

Offline peatoluser

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Re: newnes - a triple expansion engine
« Reply #27 on: January 25, 2014, 05:38:22 PM »
Well, with procrastinating  about how to cast a nut, and allowing myself to be side tracked by other projects , I thought it was time that I faced this up to this and get it out of the way. (hadn't realised its been over 6 months!)
 I know nothing about casting and was always dithering between building a proper furnace or just try and make something basic and hope it works.
the argument against a something to substantial was the fact that I don't really have the facility to machine castings so might be a bit of a wasted investment (although looking at PatJ's posts it looks like it can be done for not much investment , so may still have ago in the future - it looks like a lot of fun- with the correct safety procedures of course).

I briefly had access to an oxy- acetylene set to do some soldering  when a friend  suggested that why not use the cutting nozzle to melt the bronze. after all it is only a small part. (part of the reason as to why I was reluctant to invest in casting equipment for a one off)

well, I remade the screw and also a small stud to cast the bronze around


I then welded a small open cube with the stud in the middle as well as a small cupola(?) to melt some scrap bronze in.
suitably attired it was a case of heating the cube to cherry red then the cupola with the bronze in until it melted then poured it into the hot mold
well, that was the theory. the problem was as I heated the cube the bronze would begin to solidify and when I heated the bronze the cube would quickly lose heat.
 I was worried that the bronze would solidify as soon as I poured it and would not flow round the thread
it looked like this did happen so I ended up playing the flame over everything untill the tip of the stud melted (I had left a centre in this hoping to drill out most of the stud)

this is the result

I ground off the outside with an angle grinder, then spent about 3 weeks dissolving the stud.
i done it out side on my camping stove when ever the weather let me while I got on with other stuff in the shed.

eventually no more bubbles!
I used the old scew to lap in the nut and it actually went on first time on the new screw!!



the depth of thread is so much deeper than the first try and it also seems to have flowed round the sacrificial thread OK with no cavities, blow holes etc near it!


now to push on with the rest of it (hopefuly!)

thanks for looking

peter

Offline rhankey

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Re: newnes - a triple expansion engine
« Reply #28 on: January 25, 2014, 08:04:24 PM »
I am in awe with your ingenuity to achieve such a small acme thread.  I thought I achieved quite an accomplishment sticking with the 2 start threads as spec'd on the Stuart plans.  I was sweating buckets cutting the threads in the nut, as it required such a small delicate cutting tool - which broke as I was cutting the last spring cut.  Fortunately, it only took a few minutes of turning the thread back and forth on the threaded rod to get it turning freely.

Offline ths

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Re: newnes - a triple expansion engine
« Reply #29 on: January 25, 2014, 09:26:37 PM »
That's fantastic, specially when it worked first time on the acme screw. I know I love it when I surprise myself.

Cheers, Hugh.