36x60x54 Twin Tandem Mill Engine

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
So why don't artillery pieces look like waffles on the outside of the barrel? It's because a plain cylindrical shell is the most efficient design for resisting internal pressure. (Actually for very thick cylinders like gun barrels, some gain can be had from shrinking one sleeve inside another.) Yes you could make the wall thickness thinner by introducing webs, but you would need more material over all.
 
I would still say that the person designing this relatively sophisticated and advanced steam engine was not a beginner at designing engines, and they did not just randomly add some webs for no particular reason.

I suspect this engine was an evolution of many earlier more simple designs, and reflected state-of-the-art steam engine efficiency at the time.

Doesn't seem logical that so many webs would have been used if previous experience did not dictate that they were needed.
I would guess the person who designed this engine was in the business of designing advanced steam engines.
.
 
Last edited:
All,
I started on the LP cylinder and attached the drawing below. This gets pretty interesting. The valve body is on top with two separate spool valves.

Please help me out on this one, are there two spool valves to keep a smaller valve design and still maintain the high flow rate of steam?

I doubt these valves will be driven on the crank directly due to the location, so there must be a intermediate shaft somewhere behind the LP piston.

There are large exhaust ports on the side. The circular flange on the side is incoming steam from the HP cylinder.

The circular flange on the top is for the starting valve. From what I gather this far, the engine was started off the LP cylinder only with direct steam. I think there was a starting valve on both sides. I have the drawings of this valve and it seems like a generic cartridge valve. I cannot figure out how it was actuated yet.

Mike

IMG_2371.jpeg
IMG_2371.jpeg
 
All,
I started on the LP cylinder and attached the drawing below. This gets pretty interesting. The valve body is on top with two separate spool valves.

Please help me out on this one, are there two spool valves to keep a smaller valve design and still maintain the high flow rate of steam?

I think you must be right. I've never seen double piston valves before.

There might perhaps be a separate shaft to drive the valves or they might be driven by rocking levers.
 
This engine is the only horizontal twin tandem compound I have found online.

Looks like Corliss valves on the high pressure cylinders, and piston valves on the low pressure cylinders (am I seeing that correctly ?).

Normally a piston valve was used as steam pressures increased from 100 psi (+ -), to 250 psi and above.
Piston valves will withstand superheated steam, whereas D-valves don't do well with superheat.

Corliss was king until Charles Porter came along with the modern high speed steam engine.
Porter was heavily influenced by steam locomotives with high piston speeds, and so it was not a totally unique concept, but was unique to the stationary engine world.

The engine at this link has unsupported outboard crank pins, and so that puts the eccentrics inboard next to the flywheel.

The piston valves appear to be driven via rods directly from the eccentrics.
I can't follow the valvegear drive for the Corliss valves; photo not clear enough.


https://www.nmes.org/dee.html


Edit:
I have never seen twin piston valves either, but as I mentioned, I see a new type of steam engine about every day, and the variety seems to be endless.

.
 
I don't see any Corliss valves for this engine Pat all the same spool valves

Quite possible they used two on the LP due to the larger volume of partially expanded steam.

As Charles says a rocking lever would soon get the line of eccentric movement up from engine ctr line to the height of the top pair of valves than a cross shaft with two arms to drive the two vale rods.

This engine has a rocking valve to get movement upto the valve


DSC03971.JPG


This is the sort of cross bar that may have been used to split the single eccentric rod movement to two valve rods but would not go back to the yoke and single rod like this engine

DSC04643.JPG
 
Last edited:
As I recall (check me on this), the lower valve controls admission, and the upper valve controls cutoff.
Valve on top of a valve.

I think the ironclad Monitor engine had that feature; Rich Carlstedt could fill us in on that.

The problem with a single D-valve is that there are limits to where you can establish admission, cutoff, release, and compression; since all the edges are attached to the same valve and the same eccentric.
Double valves corrects this problem, as do the Corliss style valves, or any independently operated intake and exhaust valves.
.
 
You have got it. The main valve controls admission, release and compression, and the expansion valve controls the cut-off for expansive working. I am aware of four types.

In the simplest type the cut-off is controlled by the relative phasing of the main and expansion valve eccentrics. The phasing is fixed but the engine may have a provision for the expansion eccentric to be adjusted as a maintenance job.

In the second arrangement, a governor controls the engine speed by altering the cut-off. The expansion valve eccentric is connected to a swinging slotted link. The valve rod is linked to a die block in the slotted link. The governor is arranged to raise or lower the die block in the slotted link, thereby altering the stroke of the expansion valve, and so adjusting the timing of the cut-off.

Thirdly, there is the Meyer (not Myers) expansion valve. In this type, the expansion valve is in two separate piece. The two valve heads are driven from the valve rod by means of a sleeve that has right and left hand external threads. Rotating the sleeve causes the two valve heads to move together or apart, allowing the cut-off to be adjusted by altering the effective length of the expansion valve. Usually the threaded sleeve has a splined extension through the rear cover of the valve chest so that a handwheel can be used to manually adjust the cut-off while the engine is running. An engine with this arrangement that I have seen running is at: https://en.wikipedia.org/wiki/Coleham_Pumping_Station

The Rider expansion valve is more complicated, involving an expansion valve that has a curved seating on the main valve so that it can be rotated sideways. The ports between the two valves are angled across the valve, so that moving the Rider valve covers more or less of the ports in a sort of wedge action.
 
Last edited:
Thirdly, there is the Meyer (not Myers) expansion valve. In this type, the expansion valve is in two separate piece. The two valve heads are driven from the valve rod by means of a sleeve that has right and left hand external threads. Rotating the sleeve causes the two valve heads to move together or apart, allowing the cut-off to be adjusted by altering the effective length of the expansion valve. Usually the threaded sleeve has a splined extension through the rear cover of the valve chest so that a handwheel can be used to manually adjust the cut-off while the engine is running.

How would this work in a twin? so both engines would be "balanced" for want of words. would the hand wheel be connected to both engines?
 
Hi All,
Interesting videos. I recently watched a documentary on the Monitor Engine by Drachinifel, very interesting on that style of engine and how it came about after the oscillating engine.

I roughed out the valve body on the LP cylinder and will spend the next few days on getting it drawn. I did some looking ahead, the spool valves and eccentrics are the same for the LP and HP cylinders and the plans call out qty:6 of each, which makes sense. I am fairly confident the HP cylinder valve is driven off the crank directly, but i can not find any reference of the LP cylinder valve connecting rods.

Does the term " lay shaft" mean anything to you guys? It is a shaft with levers on it.

I will work on getting some of these drawings digitized so I can "dump" drawings of mechanisms out here.

From this assembly, the rear base is connected to the LP cylinder. The rear base has the cross slide and main crank bearings. The opposite side of the engine is a completely separate entity, only being connected with a set of machine surfaces on the two crank bases.

Mike

1720748961559.png
 
I was kind of expecting there to be some form of bracket on top of the casting between the two cylinders that would carry a shaft, which would be a bit like the pivot of the rocking lever on that blue engine I showed.

Lay shaft is more usually one that rotates with pulleys or gears but I suppose it could be used for levers too.
 

Attachments

  • links.JPG
    links.JPG
    54.8 KB · Views: 0
Answers to Richards Question moved to new thread.
 
Last edited:

Latest posts

Back
Top