Mark's Monitor Build

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.
Hi dnalot !

Just a quick post. The base for the steam chest has been glued to the cylinder and all went well. Tested for leaks and all is tight.

Mounted the cylinder to the mill and trued up the valve surfaces and then relieved the flanges to locate the steam chest in place. All the steam chest parts now stack up properly and are located (locked) in position for drilling and tapping the holes for the bolts that will hold everything together. I will wait for a new 2-56 tap and the appropriate drill bits before I move on with this step.

In the meantime I will be modeling the heads and a couple of other parts for casting.

View attachment 135795

Mark T

I have a few questions :
What glue do you use ? Is it durable ? and why don't you solder ?
What glue do you use ? Is it durable ? and why don't you solder ?
Well it is not something I would normally do but I like to experiment sometimes. The epoxy is called JB Weld. In the way I used it I expect good results. Solder would have been better but holding so many pieces in place would have been difficult and I did not want to risk warping the cylinder material.

I am a fan of yours Minh-Thanh. Love your builds.

Mark T
I have been working on the Bed-plate. The original was made of cast iron and was cast one-piece (I think) . Mine is made of aluminum and is assembled from 6 pieces. I cut the main parts with my cnc router table. The parts were then bonded together with JB Weld epoxy. After assembly smaller details were added and fillets were added where appropriate to mimic the look of the original's casting. I have no idea what color the original part was painted so I will go with something I like. For now the bed-plate has been etched with Alodine and painted with zinc chromate primer. I have provided a drawing of what this part should have looked like. Dam Murphy and his Law. I could have not mentioned the error and no one would have noticed except Mr Carlstedt. But I didn't want to put him in the position of having to decide whether to mention such a huge mistake.


Part after being etched with Alodine. A must if you want your paint to stick to aluminum.

Cylinder-test-fit-2 gif.gif

I am now working on the main shaft bearing support and the bearings for the rock shafts.

Mark T
Very nice work. Had to look Mossyrock up. I lived in Castle Rock for many years before coming back to the UK where I grew up. Beautiful area! Looking forward to seeing this engine progress. 👍
Did you get the plans from Rich? His "build book" is impressively large.

Find the excellent drawings by R. W. Carlstedt here

Rich has been very helpful. Giving pointers on how he did some things and providing information about what the Museum that has the original engine has found during the conservancy.

Thanks for the likes and comments guys. Nice to know someone is watching.

Mark T
I'm in the "Study the plans" phase now. R. W. Carlstedt did an excellent job with these plans.
I decided to paint the Bedplate olive-drab

The bracket for the crankshaft and thrust bearing has been added to the Bedplate. And the brackets for the translators have been added to the bedplate.

Bearing blocks have now been installed to the Bedplate assembly for the main crankshaft, rocker shafts, translators and the shaft the eccentrics will ride on.

I don't know what I will do next, now that I have options. With the big stationary parts made its time to start adding the moving parts. I think the logical next step is to make some sort of mount and display stand. Mr Carlstedt mounted his model on a section of the hulls bulkheads. My model is of a larger scale and I don't want the size of the completed model getting out of hand so I will be doing something different.

Mark T

I wasn't planning on returning to my shop till the fall but heavy smoke from nearby forest fires have driven me indoors. Expecting temps in the mid 90s so I can test the shops heat pump I repaired a few days ago while I'm here. I never normally use the AC function of my heat-pump but with the windows closed against the smoke its a must.

I have mounted the engine to a 14 inch diameter disk made or black walnut and mahogany. Wipe on Poly for a finish. The signboard is made of spalded hickory. Later I would like to set this on a motorized turntable.

Power has been out this morning so I had to move outside to take this photo.

Mark T

display mount.jpg
Absolutely beautiful! Icing on the motor, finishing touches all perfect! You did an remarkable job on this extremly difficult project, congradulations are in order!
Say hello to Andy Beaverhausen. He is dressed in a sailor costume of the era. Just to lend some idea of scale. I don't know if I should paint him or just leave him as is.

Mark T


Pages 4 and 5 are just a lot of chatering, skip to near the end of page 6 to resume the build.

Thats what happens when you take to long between posts.

Mark T
Last edited:
The John Ericsson designed Monitor ironclad engine (1862) has fascinated me ever since I saw a video of Rich Carlstedt's build many years ago.
There have been others that built Monitor models, and one is in the Mariner's Museum in Newport News, Virginia, as shown in the video below.

Another build is from a source that unfortunately I did not save or document, and so I can't credit the source, but it was found somewhere online while searching for Monitor engine information.
These photos are not mine.
Perhaps the photo below is the same engine as shown in the video above?
They do look to be identical except in color, which may be just a function of the lighting when the photo was taken.



I think what distinguishes Rich's model from all the rest is the extraordinary attention to detail, not to mention the world-class machining work in a very small scale.

And Rich has worked with the museum that has actually acquired the original Monitor engine from the seabed, and I think Rich's understanding of the workings of this engine is better/deeper than the museum folks.

After documenting his Monitor build so accurately, Rich has become the defacto Monitor engine expert (and expert builder), in my opinion.

We shouldn't forget the original genius behind the design though, which is Swedish John Ericsson, not to diminish the work of subsequent model builders in any way.
What a fantastic set of patterns and molds that must have been, and no doubt it took a clever foundry person to cast that original engine.

I had the honor of seeing Rich's engine in person, and I can attest that it is as impressive in person as it is in the video, if not more so.
And I have heard a number of Rich's stories of his trials and tribulations of building such a complex and rare engine (a book in and of itself).
Rich has documented the Monitor engine in 2D and 3D, and this represents many many years of work, that he has shared for free.
Rich's work and his "gold standard" model have really peaked the interest in this fabulous and incredibly historic old marine engine.

And while reasearching the Monitor engine, I ran across a print of another John Ericsson engine that was built for the Monadnoch, which at the time was one of the few online sources for the working geometry for this engine.

Here is the Monadnock engraving.


This was a simulation I made using the geometry from the Monadnock print.
I drew a 2D CAD drawing, and rotated the parts a few degrees at a time, taking a GIF each time, and then combined all the GIF's to make an animation.
This was the first time I really started to undertand the geometry of Monitor-style engines.

Some (not sure how many) of the existing original Monitor drawings have been published, and I have seen a few of these.
I am not sure if John Ericsson himself created these drawings, or someone else, but they are certainly worth a look.
The quality of the original drawings is not very good, but luckily these drawings exist at all, since many/most drawings for old steam engines do not survive.

I have seen the original drawings for the Mississippi gunboat, and those drawings were created by Charles Copeland, who also designed the side lever engines for the same boat.
And Charles Copeland designed the side lever engines for the Pacific too, which is a most impressive steam ship.

Finding original drawings for these early 1800's ships is facinating, even if the drawing quality leaves a bit to be desired, since it gives us the original souce material for the design, and thus ensures that a very accurate model can be constructed (if you have that sort of talent).

Last edited:
Well done Green Twin on the research.
Bell cranks are simple devices to translate angular motion in one form to angular motion in another. e.g. where one lever in the middle of a hatch is used to drive a number of latches around the hatch.
The sleeve to wrist-pin is a common design in many double acting Naval marine engines of the period, used for compactness. I think Brunel even used it on some of his engines?
The use of cranks to translate motion from one axis to another is very common in many industries where linear motion (e.g. from a piston) needs to be translated to some remote actuator.... e.g. vacuum or air pistons driving levers to operate brakes on railway wagons.
So the "simple" idea of combining all these attributes into a single engine is the clever bit.
Walschearts valve gear is perhaps a super clever bit of crank motion design, as he uses various angles of crank to take the prime mover motion to create non-linear valve motion best suited to engine needs.
When I joined an electrical switchgear manufacturer in the 1980s, they had used bell cranks extensively to convert horizontal linear motion to vertical motion and back to the horizontal, always with 90degree cranks, but usually with different lengths of crank to gain velocity ratio or mechanical advantage.
I had a problem of extending the contact breaker stroke, from the same actuator stroke by increasing crank lengths. But the electrical designer had set certain distances of travel of the contacts to occur at certain times (for the circuit breaker to extinguish the electric arc). To achieve certain speeds of contact at these points in the motion curve I used non-linear curves of velocity ratio and mechanical advantage - by simply rotating the cranks away from the "90degree" angle of 1:1 ratio of motion. This enabled the driving piston to do more work initially through a larger velocity ratio: more piston stoke than a 1:1 ratio would deliver (work = pressure x area x STROKE), thus accelerating the actuator to higher speed before "position 1" design parameter. As most of the "power" was lost during the mid-part of the motion, the remaining 20% of kinetic energy at the end of stroke could be transferred back from the actuator to power piston end of stroke so the whole system could be "stopped" by the high mechanical advantage of the end of stroke, without exceeding maximum stresses and strains of the components. - Not clever, just borrowing ideas from the centuries of "crank work" that had gone before. But it has left me fascinated by "crank-work" since then. - Maybe it has made me the "crank" that I am? Perhaps the cleverest original cranky idea was taking the simple beam of "linear to linear" motion (Early use of beams in atmospheric pumping engines, or village water pumps!) and making it into James Watt's "linear to rotational" motion of his patented crank beam engine design?
Then another curious "cranky" idea is the use of 2 valve gear motions from eccentrics being conjugated to a third motion for the 3rd cylinder of some Gresley steam locos...?

Enjoy these cranky designs!

Last edited:
The original Monitor drawings apparently show more than one engine configuration?, with one configuration having vertical cylinders (if I am looking at that drawing correctly).
I guess it is understandable that steam engine design of the era was in a state of flux, and there was no concensus about exactly what the best engine design/layout was.
Some of the Monitor's dimensions were driven by the very low profile of the Monitor hull, and the need to keep the engine below the deck of the boat.
The quality of the original Monitor drawings is much better than the quality of the original Mississippi gunboat drawings by Charles Copeland.

I would guess that Rich Carlsedt has compared the original Monitor engine drawings to the actual recovered Monitor engine, and he would have a better idea on the actual "as-built" design of the Monitor engine, as far as how closely the drawings were adhered to.


Latest posts