Stuart Triple Expansion Engine

[aarggh]

You only paid 8 pounds 3/ for the engine which in 1960s dollars is only $13!!

How did you get $13 Harry? That would have been a great sum then, I know my father-in-law bought his house around then and it was under 3000 pounds. If you extrapolate it based on that and todays value, the engine would have been around 1000-1400 pounds roughly in today's rates I figure.

About a weeks pay, would that be right Alec?

cheers, Ian

 

[Alec Ryals]

At that price I should of bought one of each but it wasn't me The receipt came with the package on eBay I wonder what the increase % is. and the #1 engine with reverse kit was ~ 4-6 pounds.

Alec

 

[Alec Ryals]

Hello Ian.
I not very savoy on exchange rates I have been to England back in 69 threw 87 but I live in Calif. U.S. but sounds even more costly.
Cheers
Alec

 

[rhankey]

I'm still confused about timing on a compound engine, My twin compound launch will run on air or steam, To time it I got each cylinder to run the fastest, then hooked them up and it runs on booth, This can't be right I would think I need to time the second cylinder (LP) using steam coming from the High pressure side and go for the fastest speed this way,as from what it shouldn't run on air but it screams to more air the harder and faster it turns -within reason.
Does anyone know about this I would be Great full.
Alec

Timing for compound and expansion engines gets quite involved. I have a really good book from 1907 named “Model Steam Engine Design” by R.M. de Vignier that covers timing really well among many other topics. Google seems to have an online scanned copy of this book for free online viewing. I’m sure there are numerous other books on the subject.

Without having all the dimensions for your valve ports, valve, eccentric throw and angle, I’m guessing it isn’t going to be easy for someone to determine why your twin compound works equally well on steam and air. In theory, a compound really needs steam to run properly. Without modifications from Stuart’s plans, a compound should only run on the HP cylinder when powered by air.

Without modifications from the plans, the Stuart triple isn’t going to run very well on air if at all, as the friction of two non-contributing cylinders is likely to be a significant drag for the one cylinder to deal with. Since the triple can run in forward and reverse and the forward & reverse eccentrics are machined from a single piece, there isn’t much timing adjustment to do. Each pair of eccentrics have to be centred to the crank throw, as rotating the eccentric one way to benefit one direction will throw off the timing of the other direction. In fact, I used keyways to fix the eccentrics to the crankshaft on my in progress triple rather than using the specified grub screws. All that leaves is adjusting the valve up/down so it is perfectly centred to the valve ports. If you wanted greater timing adjustment, I think you would need to start by making the forward and reverse eccentrics as separate pieces so they can be adjusted independently of one another.

Robin

 

[Alec Ryals]

Robin,
Thank you for the information I will look up that book.
Alec Ryals

 

[Alec Ryals]

I was reading a sentence in a right up were this little fellow visited him, well he visited me.
After being so ever careful to offset the HP cylinder -016 to compensate I went the wrong way hence I only caught it way to late and now have to settle with a .781 bore "I always thought the HP was a bit small .
Now I'm making rings hence the kit came with none, I'm using the Tremble method and my only problem is cracking the ring to get a nice even crack but the first one was clean enough so that filing a .0015/.002 gap made it clean up nicely. On my drawing Stuart shows 3 rings on the HP & IP pressure cylinders and one wide one on the LP cylinder V's my Twin compound Witch call for two and Twin launch calls for one 1/8" wide rings on the 1." bore seems bit much I wounder how many times the triple has had this changed.
Alec

 

[Alec Ryals]

Here are some more photos of machining the steam chests

 

[Alec Ryals]

Well I started on the cylinder bottoms finishing the gland side all in the same set up (In the 4 jaw chuck) The drill wandered so I had to single point to bore to true up, then transfer the 4 jaw to the mill to finish up the detail.
Alec

 

[Alec Ryals]

Well all my drills wondered when drilling the bottom cylinder covers hence I had to single point bore them to get a true straight hole them reamed them to 7/32 there must be little hard spots that make the drill wonder, here are some more photos of the other cylinder bottom covers.
Alec

 

[rhankey]

Well all my drills wondered when drilling the bottom cylinder covers hence I had to single point bore them to get a true straight hole them reamed them to 7/32 there must be little hard spots that make the drill wonder, here are some more photos of the other cylinder bottom covers.
Alec

Looking good.

The cylinder covers on mine were terrible for hard spots around the outer diameter, and far worse on the guide mounting flanges. I had to hand file through the hard spots so I didn't destroy a bunch of cutters.

Robin

 

[Alec Ryals]

Some were I saw machining the center eccentric for the Stuart triple or maybe it was just photos as I can't remember, does any one have any photos of this or a procedure for machining this.
Thank You
Alec Ryals

 

[Alec Ryals]

Well I'm onto the base, I can't de-side if I should leave the casting bases for holding down the engine and make shims for the back or machine the whole bottom, any thoughts would be greatly appreciated. I lapped the top side till flat hence it was very flat anyway (Good Casting) then super glue to the table and take light cuts till the bottom cleans up that way there is no pressure warping the casting and a sharp blow with a mallet will break the bond and acatone will and a sharp razor will remove the super glue.
Thank You
Alec Ryals

 

[rhankey]

My sole plate did not include the front pair of "feet" that yours has. As such it was an easy decision for me to machine the pump bases flat with that of the rest of the front and back edges of the sole plate. I know it is a little early to be thinking of a base to sit the engine on at this stage, but perhaps that may also influence your decision. I am quite happy with how mine looks sitting on the wooden base I made for mine a few weeks ago. I'm in the midst of final assembly, and have yet to make the pumps.

 

[Alec Ryals]

I just measured the cylinder mounting hole locations and they are all less than they are supposed to be ? So I set my planer gage to 3.0" and sure enough its minus ~.015 in three inches and about .004/005" per inch my mill lead screw is off, Now its time for D.R.O. my lead screw only has ~.010: backlash -(Go Figure) all I need to do is machine the sole to fit, Oh-Well.
ALEC

 

[steamedlou]

Help, help, help. this may be the perfect thread to ask about the triple timing. I have an ebay engine and I'm not sure its ever been run on steam even though its 10 years old. Things don't look right. I see the comment above about the eccentrics being symmetrical and that makes sensel. Should make for very minimal adjustment. Stuart's timing instructions say to start with cover off LP valve chest and with crank at TDC, high points of IP eccentric should be 90+15 degrees and HP should be 90+30. Now i'm assuming we are talking about the LP crank at TDC. Is this right? So if I understand the meaning of this, the high points of the IP and HP eccentrics should both be "hanging" below a horizontal centerline 15 and 30 degrees and symmetrical about a vertical center line. If this is so then mine are not adjusted correctly. Now fine for IP and HP. So when LP is at TDC, where should the LP concentric be? I'm kinda assuming above horizontal centerline about to open the valve. So please, someone tell me if I'm thinking right. I really don't want to undo every thing if I'm not understanding the instructions. This should not be rocket science but nowhere can I find instructions on where the eccentrics are to be placed. I have the Stuart drawings but they don't go into it at all.
Some one save me from my ignorance!

 

[kilocharlie]

Alec - If heat transfer is critical, you would be wise to machine the entire base for maximum contact with mated parts instead of shimming. Just a suggestion, good luck!

BTW, for everyone's benefit, what is the purpose, type, and cycle of these engines? I'm guessing steam power? Are they unique to Australia?

 

[Charles Lamont]

Help, help, help. this may be the perfect thread to ask about the triple timing. Things don't look right.

As the pair of eccentrics for each cylinder are machined in one piece, you cannot alter the advance (the angle in excess of 90deg each side) . If the angles between the throws are (far) wrong they would need to be replaced. The only thing you can do to set them is to ensure that they are positioned symmetrically either side of (away from) the relevant crank. I am not sure why the instructions seem to refer to setting the eccentrics for one cylinder in relation to the dead centre of another, though if the eccentrics have 30 degrees of advance the throws will line up with the other two crank pins. It may be easier simply to consider each cylinder independently.

You say the the advance is different for different cylinders. You may need to check that the eccentrics have been installed in the right place.

Note that the eccentric rods are most likely to be arranged 'open'. This means that at bottom dead centre the eccentric rods are apart, while at top dead they will be 'crossed'.

Having done that, you need to set the valves. Not having seen the instructions, I suggest you could either set them for equal opening or for equal lead (that is to say equalising the amount of opening at top and bottom dead centres).

 

[rhankey]

Steamedlou, As Charles indicates, assuming the engine has been made and assembled precisely to plans, there is very little to do for timing the Stuart triples since each pair of eccentrics is machined as a single piece. All you can do is rotate the eccentric pair so it is centred to that of crank throw it belongs with. Then set the engine in forward or reverse and adjust the valve rod so that the slide valve has equal travel over the inlet ports.

Given there really isn't any opportunity to adjust the eccentrics, I deviated from the plans and keyed my eccentrics to the crank shaft, rather than used set screws.


Having recently setup the timing on a Stuart triple I'm very close to completing and having seen what a number of builders have done, here are some other things to watch out for when timing or setting up a Stuart triple:

• The LP and IP require *each* eccentric to be machined with a 5/32" throw and 15deg from a horizontal plane. the HP is the same, but is 30deg rather than 15deg. So, make sure the eccentrics are in the correct locations and machined correctly.
• Alignment of the reversing linkages. I have seen way too many of these engines where the reversing linkages aren't exactly aligned with one another such that one cylinder is in full forward, while another might be at 3/4 forward, and even worse another might be in reverse! This is tricky to set up, as you more or less have to do so after full assembly while dealing with real estate challenges. I've seen way too many using set screws to attempt to lock the reverse shaft levers to the reversing shaft, which can't possibly give a sturdy enough attachment.
• You want to be sure there is no slop in any of the reverse gear linkages, as with such a small engine, any slop will result in a fairly big problem.
• The valve rod adjustment is somewhat crude, as you are dealing with increments of +/- half a turn of a 4BA thread.
• Setting the IP valve rod is tricky, as you can't actually see what's going on. I set my IP valve rod by taking measurements from that of the HP & LP valve rods.
• Given you aren't sure on the timing or history of this engine, I would also check the inlet and exhaust ports have been machined to the correct sizes and spacings, and likewise the slide valves are also correctly machined.

Robin

 

[steamedlou]

damn it i just wrote a length reply and is didnt go through. said i wasnt registered and i would store it until i am. lol i am registered and have no idea where is would be stored. test test

 

[steamedlou]

I'll try it again. Thanks Charles and Rhankey for your help. i have some adjusting to do. the "crossed and uncrossed" eccentric rods seem OK but in no way are the eccentrics symmetrical about the crank. I did get it to run on steam in one direction and with the LP drain valves open. We will see if some adjusting does better. I see comments above about the use of gaskets. Use them!! mine was assembled with some gasket compound only which didn't hold steam. I have been using cotton writing parchment coated with a copper bearing anti seize compound on other Stuart engines. That didn't work either. I will use gaskets and compound. I think you are in error on the 30/15 eccentric advancement. The HP is 90+30 while the LP and IP are both 90+15. Wish my reverse operating rod was not pinned. It is and all i can do to make some adjustments is to shim the operating screw out at the hand wheel. to center the operation. I also found the tip of the LP valve rod broken so it does not make it all the way up into the steam chest guide. I'll leave that because i don't have a way to make a new one. Thanks again ill be following the build and give you updates on my "adjustments"