# A Stuart Turner Triple Expansion Engine



## Hilmar

A Stuart Turner Triple Expansion Engine is borne.

   I did buy the castings in the 1970s. We moved once in between and I lost all the Bronze castings.
Still have most, not all of the cast iron castings. I think it is time to start after 37 Years.
And this is the Start.
   If some one tells you it: Is easy to work from castings dont believe it. Only if you have good ones and they are a bit oversize, other wise you have a heck of a time to get there. These are not the best one. There is a problem with the cylinder ports.
  I will take pictures on a continues bases but it is slow going.
   The decision has to be made if I should continuous with this post or just drop it.
Also the moderator may put the post in a different spot. I dont know if this is the right one.
Is there a spell checker some where?
Hilmar


----------



## gbritnell

Hi Hilmar,
I have done quite a few Stuart kits over the years and have found them to be quite well done. You're correct on the amount of stock for finishing but with judicious layout it gives you less to cut. The iron has always been a very close grain and machines great leaving very sharp edges. I have done other peoples castings and was much less impressed with the quality. I have seen very few Stuart triples over the years but they are something to see when completed.
gbritnell


----------



## Tin Falcon

I have only heard good things about stuart kits. . And have admired the triple expansion engines they a classic marine design. But they must run on steam compressed air does not cut it without a modification. 
Tin


----------



## Hilmar

Hi Tin

What is with the modification?
Hilmar


----------



## Tin Falcon

Hilmar: 
IIRC there is a couple of things you can do. It has to do with feeding the cylinders pressure  1 you can feed air to the largest cylinder and let the others run free or you can feed air direct to all cylinders . The double or triple expansion does not work with air.
Tin


----------



## gbritnell

Without getting too wordy, steam is a working gas, meaning it has life. When the slide valve shuts off the supply of steam it keeps working, therefore even though it has a reduced pressure coming out of the exhaust it still has life (or work) left in it and can be used to power one, two or even three more cylinders. On the other hand compressed air only works when the valve is open. Once the supply is shut off there is no more work. The problem with admitting air to every cylinder in a compound or triple expansion is that there is uneven pressure applied to the crankshaft becuause of the surface area of the pistons. Just for round numbers lets say that you have 30 lbs. of air applied to a 1 inch piston. The pressure on the piston would be 23.56 lbs. Now you take an 1.50 piston and the pressure would be 53 lbs. Although the engine would run it would be very erratic in perfomance. You could feed the largest cylinder only but it here again it wouldn't run very smoothly because it would be fighting the friction of all the other cylinders and their mechanisms and linkages.
gbritnell


----------



## loggerhogger

I too have the Stuart triple kit. I haven't started on it yet, but one thing that I found has helped me when machining the cylenders from castings. I found that if I machine the valve face first, then I can drive a wooden plug into the cylender hole, (it's not a "bore" yet) :lol:  and then us that to find the center of the bore from the valve face. mark it on the wooden plug, use that to center it on your lathe, drive the plug out and go to work.


----------



## Hilmar

Tin .
I  understand what you where saying .
I was thinking there  was a mechanical modification in print or so.

I have two print sets, one from 5/2/55 which came with the casting in the 
late 60s.
  The second set is dated 19 April 1977 by Willis. I don't know where it cam from. Could be from Coles in CA.
So fare I came up on two different Dimensions. A P.I.T.A. when you partly 
in to machining it.

Gbritnell. 
    A good explanation.  Also in real life a Triple Expansion is basically
like a single cylinder  _*Not self starting*._ If the HP Cylinder is TDC it just sits there. Then the machinist had by change of valves get the steam in one of the other cylinders to get is off TDC.

I did some more work on the Triple.Pictures will be fort coming.
Also I have some more gadgets may be I should post them under Tools
Hilmar


----------



## compound driver

HI
The valve is caled a "simpeling valve" as you say it feeds steam into the high pressure and nudges the thing off TDC. Most compound traction engines use the same idea. Or if your my mate paul and too tight to rebuild the valve on his Fowler you pull the flywheel round whilst standing on the motion! 

Never had a problem with any stewart castings and im on my fourth engine. 

make yourself a boiler and run it on steam nothing better and as stated before compunding wont work on air.

Steam is king! LOL


----------



## Hilmar

Some more photos from the Triple.
 I am cutting the Piston Rods and Cross heads. Notice the Slitting Saw I am using. 
It is for a portable Trim Saw. The Carbide blade I bought from Home Depot for about nine $$ and change. Cuts true metal like butter. The slot is 0.050 and clean.
Hilmar


----------



## Mcgyver

Hi Hilmar, the engine is looking great - i like the slitting saw idea too  


I'm also working on one.  several years ago I came to the point of working on the steam pipes, got sidetracked and have been building tooling every since.  

time to get back to working on the triple   here's a pic of mine

http://i20.photobucket.com/albums/b201/michael0100/Stuart Triple Expansion/st2.jpg

what sort of port trouble are you having?


----------



## Mcgyver

dup, sorry


----------



## Hilmar

Mcgyver,  
    the castings had pits and holes in them. The valve ports had pits and where not parallel and also oversize. I will have to see how it works out. How did You finished the Crankshaft. One piece or put together. Also how do You make out with the two start thread for the reverse change?
Hilmar


----------



## Mcgyver

that's too bad about the ports.  i made the crank shaft from the solid, only way to go imo.  The silver soldered fabrication that comes with the kit makes a better pretzel blank than crankshaft blank, its just too flimsy to work with.  The crankshaft came out beautifully from the solid.  I used free cutting steel to give myself a fighting chance.  No, free cutting is not the best material for a crankshaft, but its a model not a lawn mower engine   Also, I made the counterweights from steel.  I had made them from the cast iron provided and first one i try to peen on split.  dang.  maybe that tip will save you some time

two start thread is still to be done, and it looks challenging.  Current thinking is to make a progressive tap or several taps each taking out a percentage of thread depth.  I want to get the torque on each down to a minimum.  the taps won't have to be very long which helps.  that said, i still expect it to be tricky, I've made taps but not that small.


----------



## Bogstandard

Hilmar,
The way to go is to cut the multistart on the lathe, is is really easy to do if you just do it logically. It is just getting into a routine of dropping in on one threading dial number then repeating for the second start on another number before putting any more cut on. It is just done in equal stages, a bit off one start then a bit off the next. Don't try to cut one full start then attempt to cut the second, it just won't work properly.
I am sure that a man who has got as far as this on this build could easily tackle multi start threads. Practice on a bit of scrap first.
If you can make a multi start tap you can make the cut direct and cut out the middle bit. 
I find it easier to make the cuts by not feeding onto the forward cutting face, but onto the reverse face, this takes all the pressure off the cutter and I end up with a much better multistart thread. That goes for both internal and external cutting.
But you do need your lathe running as slow as possible.

Mcgyver,
Still being sidetracked by your massive learning curve in electronics. Have you finished those damned flanges yet.

John


----------



## compound driver

Hi
The better way o cut multi start is to set up your change wheels for twice the pitch required so lets say 10 TPI for a 5 TPI double start.

Cut the first start of the thread to depth and finish as a normal thread. Next advance the compound slide by half the 10TPI pitch and cut the next start.
Using the same number on the threading dial.

If your cutting a blind internal multi start it helps to have a stop on the bed or a bit of room at the bottom of teh bore for jiggle room. Best machine to use is a Hardinge but we are not all lucky enough to have one sadly.

Using different numbers on the thread dial can cause big errors in the thread and leave you lapping the nut to the bolt.

I still do a lot of these this way after my father laughed at my attempts 30 years ago. 

Cheers Kevin


----------



## Mcgyver

> Mcgyver,
> Still being sidetracked by your massive learning curve in electronics. Have you finished those damned flanges yet.



and the ball drops... hehe ... nope, not yet.  almost got the spot welder done so i can make the enclosure for the bench top power supply so i can test the cnc so i can make the flanges .  the process of learning electronics has been particularly effective at making me feel stupid.  

on the multistart thread, imo the challenge isn't just that its multistart , it's that its 3/16".  The tap idea occurred because trying to single point cut a 3/16 internal thread seemed masochistic.  maybe I'm wrong though, knowing its 3/16 does that change your opinion or would you still single point it?

I do appreciate the good info on multistart threads.


----------



## Bogstandard

Mcgyver,
Size doesn't really matter, both Kevin and myself have suggested different methods of doing it, it makes really no difference whether it is inside or outside threading, it's got to be done. Screwcutting it on the lathe is the way to go, either under power or if it is a bit too fast then a handle up the spindle or on the end of the leadscrew (preferable) will allow you to do it by manual power.
But I will tell you one thing, once you have done it you will wonder what all the fuss and worry was about. It is really no different than cutting normal threads, you just have to be aware of what you are doing all the time.
There are other ways to do it but the cost is very prohibitive. Like getting taps and dies made by a third party, having a dividing head on your miller connected to the lead screw of the table. If you had your cnc running maybe you could have done it with a 4th axis running on a rotary table. But I don't know how you would do the internal threading. Maybe that will delay it a bit longer while you sort that out.  :lol: 

John


----------



## Hilmar

Mcgyver,
I must have a different kit. There is no silver soldered crank shaft in my kid; it is a one piece blank cut partly out.  Some times I think that I do not have a Stuart kid but a fake. On the ports I am thinking about to mill the whole thing out and insert one plate with the ports cut correctly. Not sure what material to use. On my print, the multi start thread calls for a
   " 3/16 x 20 T.P.I.  2 start thread "
   That should be  2x 10 TPI  out 180°  I hope this is correct? 

Bogstandart



> I find it easier to make the cuts by not feeding onto the forward cutting face, but onto the reverse face,


 I don't get it. Do you talking about a rear tool post? Could you please explain that for me?

Hilmar


----------



## Bogstandard

Hi Hilmar,
What I am on about when cutting on the back face.
When you cut a normal 60deg thread you set the compound slide to 29.5deg and when the cut is put on the compound is wound forwards. On a multistart thread, because of the fast forward motion a high force is exerted onto the front face of the cutting tool, to such an extent the gears or holding bolts or the cutter can break. That is why it is recommended to move the lathe with a handwheel on the leadscrew, this reduces most of the heavy forces on the gear train. In your case this doesn't really come into it because of the small sizes involved, but because of the small size of the cutter this can easily break or dig in badly. So you put the cut using the compound onto the rear cutting face by screwing backwards, by doing this it relieves a lot of the force on the cutter.
Once you have the machine set up and the technique perfected it will most probably take less than 30 mins to cut your threads, both inside and out.

John


----------



## Mcgyver

Hillmar, chunks are cut out of the crank blank?  doesn't sound good - I think you need the rigidity of the solid bar to start with, turn the pins, put accurately made spacers between each, then turn the journals.  more than one way to skin the cat, but that worked for me and I'd not want to try turning the pins with the journal already turned down - too much spring

John, its not the 2 start that concerns me, its the 3/16 size.  I haven't cut a single point internal thread that small, seems like the tool would be prohibitively spindly, hence the tap idea....we'll see.  I've boring bars that small, but the nature of the width of cut with threading would significant increase the force on the cutting tool.  ways around that I know, but they might be more of a pita than making a tap.  might have to experiment on small dia single point internal threading

I wouldn't need a fourth axis though to thread on the the cnc, three is all you need.    I'd still have the same challenge of some very tiny tooling for the internal thread.


----------



## compound driver

Hi Mcgyver
Look sorry i just clicked on the sie your dealing with. Dont even bother trying to cut the internal on the lathe the chances of any success are slim to none at 3/16th.
I would go on as follows. Find a bit of 3/16 silver steel twice the length you need and cut your reverser screw screw cut full length so you can make a tap from the same screw cut rod.
Making taps from silver steel is reasonably easy and if done the same time as cutting the reverser screw you should only need to relieve the threads slightly to get a useable threaded assembly.
On silver steel id be inclined to grind a Stelite tool and remove a large amount of the front face to account for the fast helix your cutting. grinding just one flute should be enough but two would be nice for swarf clearing.
go no more than 1 thou cuts to depth.


----------



## Mcgyver

hey it's all good, good info on cutting 2 starts from you and John.  I'm not sure cutting the tap and screw at at the same setting will work, screw needs to be slightly smaller than the tap so there's some clearance.  I think I'll have go at a tap at major dia., tap, then thread the screw until it fits.  The other thing I've found with getting a home made tap to work is to mill away most of the threads leaving a smallish land, otherwise it takes too much torque to turn them

here's a tap that didn't work
http://i20.photobucket.com/albums/b201/michael0100/didntwork.jpg
here's two that did
http://i20.photobucket.com/albums/b201/michael0100/afterheattreating.jpg

main difference is amount of threaded area left.  after the first didn't work  (couldn't turn it) it was suggest i make the thread area smaller.  with 3/16 it'll be a balancing act between minimizing threaded area so it'll turn and not making the core so small its weak.  might be braces and a belt, but doing a couple of taps in different %'s of thread depth appeals, ie minimize amount each tap has to take out.....but in making taps this small I'm in uncharted territory, the pics above are 1/2 20 L, at lot easier than 3/16


----------



## Bogstandard

Hi Mcgyver,
I will admit defeat on this one, Kevin seems to have done it a lot more times than me in this small size, and seems a lot more logical to make the male thread at the same time as the tap.
But depending on the material, you just might have to revert to taking a bit of 'meat' out of the female thread to relieve pressure on the tap to prevent breakage, or have a long lead in taper and take it very steady.
It is little problem jobs like this that usually hold up a build for ages, but once done you wonder what all the fuss was about.

John


----------



## compound driver

Hi
It does work fine if you think about the thread after finishing you have polished the crests on your screw to remove any burs so its lower than the crests on the tap and vece versa. 
If the thread is a little snug work it with BlueBell for a few dozen turns. 

cheers kevin


----------



## Hilmar

Hi, Mcgyver 
since you have the planes for the Stuart Triple, I have a question .

    The 3/16 x20 T.P.I. as printed on the Plane is

    a , 20 T.P.I. cut twice to have 40 threads or

      10 T.P.I. cut twice to have 20 threads
 I know we talked about the subject but that question was not discussed.

  I got different answers from people on that question.
Hilmar

P. S. This new site is real nice here.


----------



## Mcgyver

Hi Hilmar,

i had to look this up, but here's the rule: the lead of a double thread is twice that of a single thread having the same pitch....

from machinery's handbook,

_Pitch: The pitch of a thread having uniform spacing is the distance measured parallel
with its axis between corresponding points on adjacent thread forms in the same axial
plane and on the same side of the axis. Pitch is equal to the lead divided by the number of
thread starts.

Lead is the axial distance between two consecutive points of intersection of a helix
by a line parallel to the axis of the cylinder on which it lies, i.e., the axial movement of a
threaded part rotated one turn in its mating thread._

so if tpi= 20, pitch = 1/20 and then again divide by the 2 starts, the Pitch = 1/10

I believe that's saying to cut a 2 start 20tpi thread, its two helix's 180 degrees apart, each at 10 tpi - the gear box is set at 10 tpi but you're only advancing the tool in as per a 20tpi thread. 

seems rather daunting cutting a 20 tpi in 3/16 stock doesn't it? and we have to make a tap to boot! you are of course doing this as an acme thread to remain true to full size practice right? (j/j )

Hilmar, if you're about to tackle this part, I'll watch with great interest how it works out. these is nothing to stop us from saying, lets have a go at some other number than 20. I'd probably start at 20 and if i couldn't get a decent job of it scale back a bit


----------



## Hilmar

Hello Mcgyver
 ??? I am sorry but I forgot to do that thread in ACME, ;D ha ha .
But in any case you do not need a Die or Tap to make the 
3/16 X20 TPI.
Have a look at the pix. You will se the finished thread plus two goofs , the one on the bottom.
The internal bit could be a bit heavier . But it worked as is
 all thought a bit slow. 
You have to take it easy. 
the spindel with centre Tail Stock and the nut normal from right to left one 1000s at the time

The lathe I have is a Grizzly 9x20 about five years old.
To cut the second thread I marked the 40 tooth gear on the spindle and moved it buy 20 teeth ( 180° ).I did three spindles and two nuts.
Some one explains to me how to centre the cylindrical nut in the chuck. I used a four jaw chuck but dont know how close I came wit the centricity.. 

Hey , Mcgyver if I make an other one I will try the ACME, Ha,Ha,Ha Maybe 20/40
Hilmar






















In the last picture on the bottom you see the two goofs.

How do you resize thos darn Pictures??


----------



## Mcgyver

Hilmar, I am suitably impressed! very nice work, 

I will definitely go the single point tool route, I'd convinced myself it was not doable but you've proved otherwise. That has got to be the trickiest looking bit of the project and you did it perfectly to the print, to the front of the class I say.


----------



## Hilmar

Thanks Mcgyver.

     But now I think I need Bogstandard, or Cedge) to Re size the pics. And my question is
 what size should they have bin ???? I am using Photo bucket and on there 
what should I use for size??
Hilmar


----------



## Bogstandard

Lovely bit of work there Hilmar.
Now you've done it the once, you should have no trouble making all the ones required when everyone rushes out and buys a triple expansion. ;D ;D
Please don't look to me about resizing pictures, I have trouble with my own. There is a post about picture posting.


John


----------



## tattoomike68

I resize pics with paint shop pro myself and set the JPG compression to make them around 70k.

A common web friendly size is 640 wide by 480 tall.

I think I have the software here set so any picture *over* 800 x 800 is resized to 800 x 800 max automaticaly.

once you upload it to photobucket click the picture, hit the resize button and there will be a 640x480 message board size option.


----------



## rake60

Now that *IS* some impressive work, both in the finished parts
and the tooling!!

Great job!!!

Rick


----------



## Hilmar

Now am I the only one who ever bent a triple crankshaft while turning it on the lathe?
   Was trying to turn the last Crank. Got too eager, feed the tool to fast, Tool caught on the crank, stalled the lathe and shaft went bang. Shaft bent. In the excitement I forgot to take a pix of the whole process. Worked almost a week on the darn piece. So I put the thing between two V Blocks and straighten it out again. How good we will see later. If it is a no go I have to do it over  Of course this never happened to You guys !!!
 Hilmar


----------



## Mcgyver

Hi Hilmar, did you get my PM re your question...wasn't sure if it went through and i hadn't heard....if not speak up.

I'll try to snap a pic of the pretzel i made. i wouldn't bother with the silver soldered blank that comes with the kit, its a lot easier to make it from solid imo. let me know if how its going, i think i remember how i did it. 

finally got back at mine, minor stuff, drilling out for studs on the valve chest, feels good as i haven't touched it in years (took a multi year hiatus and built tooling)


----------



## Hilmar

Mcgyver, 
Yes,I did send you an E-Mail back .
 Then I toughed I could put an attachment to it but that did not work. Have a look in Frequent question I put one there of the item in question.
  As for the Crank shaft. It was not silver soldered it was one piece but partially turned and milled. This was my first shaft and then a triple on top of that. It went mostly under size. I could not get the follover in the right place. So I will see how it turned out.
Hilmar

Some more pixs on , machining the crank shaft


----------



## Powder keg

That is a neat way to turn the crank between centers! I might have to try that. 

Thanks for the pictures, Wes


----------



## Hilmar

This is what I have so fare.





In the winter the shop was kind of cold, so not much got done in there.
Some of you did followed the tread in >Cast Iron< know that things went wrong some where. I think it is the Edge Finder off Set. Murphy must have bin hanging around my shop.
The LP + IP casting is off by around 0.100 ". That means the Crankshaft is not lining up with the center of the cylinders.
  I have to look now for alternatives. Scrap the Cylinder and make a new one, make a new Base, buy a new Cylinder and Base ( since I don' know if I buy only one part that it will fit on the old part, there are 40+ Years different. So I got to think (I should have that done before) to what to do.
  In the mean time I may make some more parts .For fit I will put the head on the columns and see what will happen.

Here is the Lap I used for lapping the LP Cylinder








Copper clad Cherry Wood


----------



## Mcgyver

looking good Hilmar, a couple of eccentrics and you're done!

so as you're getting close to the final straightaway, have your thoughts turned to what kind of great boiler you're going to make.........expansion engines really don't won't to work on air...


----------



## Alphawolf45

Cant bore it oversize and sleeve it then rebore in correct position?..Shame to have to start all over...Looks too good to quit on..
.
.


----------



## Hilmar

If it wouldn't be for all the other holes ,yes but as is now, no chance.
Hilmar


----------



## Paolo

Dear Hilmar
..please let me know something more about the Carbide blade who you bought from Home Depot ..like..number of tooth..diameter...Etc. TY
Paolo


----------



## Hilmar

> ..please let me know something more about the Carbide blade who you bought from Home Depot ..like..number of tooth..diameter...Etc. TY
> Paolo



Give me A Day or so, I will check tomorrow at home.
Hilmar


----------



## Hilmar

Paolo,

  This is the blade I use. The best thing I ever bought to cut metal
It is by > LOWE'S < not Home Depot. $7.95. 3 3/8 diameter. The arbor hole is 15 mm
On my blade the kerf is 0.055 -0.060 thin. I run the blade on a Mini Mill.
I find that when I run it slow it will no work so good,it clogs and you can hear it, so I up the rpm to 800 - 1000 on Steel. Cutting fluid from Home Depot in the pluming Dep. On Alu and Brass Kerosene or dry and even more speed. The kerf is as smoth to be used directly
and no wandering.
Hilmar


----------



## Paolo

TY a lots..I'll try to buy it from Internet...I'm living in Italy...Ty again...
Paolo


----------



## loggerhogger

Hil. On the cylinder, can you build it up with some cast iron rod and a OA torch and then re-machine?


----------



## bigmartinmachine

On discussions regarding machining the crankshaft of a Sturt triple. I put mine in a dividing head with the type of spacers other people described and milled it. Much likely to pretzel it


----------



## Maryak

Hilmar,

Just a thought, is it possible to make a new crank offset to the cylinder centres ??? and would there still be room for the eccentrics if you did that ???

Best Regards
Bob


----------



## steamer

Bob has a point, you could off set the block at the lower cyliner cover/standard mount.

Dave


----------



## Kermit

When you mentioned the crank doesn't line up with the center of the cylinders.....

Would it be easier to remake two of your piston rod connections? Leaving the center one alone and adding offset to the outside ones?

Is something like that possible with the room available, above the crank and between the supports?


Kermit


----------



## Milan Machine Worrks

I talked Cole Power Models today an ordered a set of drawing for the triple and at the same time I asked them about the castings being available separately and availability and they have the cylinder in stock.


----------



## GWRdriver

This is an interesting and informative thread. I have a set of Triple cylinder castings (but those are way down the to-do list) and years ago I became an advocate of built-up crankshafts, and not the brazed-up variety. I became this way after my 4th attempt to turn the crankshaft of my first engine build (a Stuart 10V) from the old Stuart drop-forged steel blank and succeeding only in making pretzels. I may have even kept one as a souvenier. Now my first option is always drill rod or SS and Loctite.

On Stuart casting quality, . . .When Hilmar bought his castings they would no doubt have come from the old Henley High Street shop and foundary. So far as I've ever heard or experienced those were invariably superb castings and these days some castings hunters especially value sets of the old castings. In addition, the old Stuarts would replace any casting which was not up to snuff. I never recall having to send for a replacement. But that was then, this is now. The castings from the current owners of Stuart Models are unfortunately earning a reputation for inconsistent quality, typically areas of hardness, which I've personally experienced lately, which is what the original Stuarts strove to eliminate. But it's the natue of the beast, small thin or delicate castings in iron are always more susceptable to spotty hardening.


----------



## Alec Ryals

Nice Work, Im making the ectrincs now and cant tell if the 30* degree one is for the L.P. cylinder or the H.P. ?
Any thought would be of Great help.
Thank You
Alec Ryals


----------



## Mechanicboy

Alec Ryals said:


> Nice Work, Im making the ectrincs now and cant tell if the 30* degree one is for the L.P. cylinder or the H.P. ?
> Any thought would be of Great help.
> Thank You
> Alec Ryals



See post #95, page 10 in this the link http://www.homemodelenginemachinist.com/showthread.php?p=260466#post260466


----------



## Charles Lamont

GWRdriver said:


> On Stuart casting quality, . . .When Hilmar bought his castings they would no doubt have come from the old Henley High Street shop and foundary. So far as I've ever heard or experienced those were invariably superb castings and these days some castings hunters especially value sets of the old castings. In addition, the old Stuarts would replace any casting which was not up to snuff. I never recall having to send for a replacement. But that was then, this is now. The castings from the current owners of Stuart Models are unfortunately earning a reputation for inconsistent quality, typically areas of hardness, which I've personally experienced lately, which is what the original Stuarts strove to eliminate. But it's the natue of the beast, small thin or delicate castings in iron are always more susceptable to spotty hardening.



This may now be out of date since the company was taken over again
oh, something like three years ago. At a show the new owners told me the had to throw out about half the stock of castings they bought.


----------

