Ball Hopper Monitor - Casting Project

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And at the scale you are building at a 3/8 - 24 plug will be closer to 1/2NPT than a 10mm CM-6

Buzz coils are not hard to make and you will be able to fit one of them into a scale battery box on the sled, just like I did on the 1/2 scale domestic along with a 6V dry cell rechargable battery.
The Monitor used a buzz coil and a 1/2npt spark plug. Some of the later pump jack engines and the HJ horizontals could be ordered with a magneto.
As far as compression ratio goes 3.5 or 4 to 1 is good, anything higher and they hit too hard. You don’t want the engine to jump every time it fires, do you?
What made you settle on the 4 horse engine? I always thought that 1/2 scale of the 2 hp would be nice or 1/3 scale of the 6/7 horsepower would be interesting, the 6 (later treated to 7) has a mechanically operated intake valve, which is unique.

That is good advice on the compression ratio.
I have never run a model IC engine, and so this is all plowing new ground for me, and I have no idea what is good or bad in a model IC engine.

I don't see the need in a buzz coil.
Seems like just a simple auto coil with points and condenser is all that would be needed.
I have never seen an engine that needed multiple sparks, but then I have no knowledge of spark ignition, or why the buzz coil became so prevalent (Henry Ford is my guess).
One spark is all you need if the engine is set up right.

Why did I choose a 4hp to model ?
It was a random choice, but turned out to be a good choice because I ran across Barney Kedrowski, and he apparently has three 4hp Monitors, and so has provided quite a bit of information.
Barney is an avid Monitor guy, and a super nice old engine guy.
Barney also cast a water hopper for his engine, and is into backyard casting, so that is right up my alley for sure.

Thanks very much to you (Joe Prindle) for the database on fb.
That has also be extremely valuable in getting this build accurate.

I saw that actuated intake on the 7 hp.
That is getting pretty modern.

The longer period of sparking that a buzz coil can give is a lot more forgiving of setup. It also comes into its own on a hit and miss that may want to fire at a slightly different position when it is just running with no load and firing every few cycles to when it is running under load and firing every cycle. Its a bit like having advance and retard that may want adjusting for optimum when an engine is either running fast or slow.
Yes I remember there was quite a taper on all the bits that stick out on the ignition side and obviously the feet and access panel surrounds
I am going to cast the bottom of the feet perfectly flat, and also cast the top of the cylinder flat.

I want the frame/cylinder casting to be very close to net, and require a minimum of machining, especially on things like the bottom of the feet.

It will take a bit more pattern work, but I can cast those surfaces accurately flat.

It would be nice to be able to just run a file over the bottom of the feet, and use it as-is without machining.

There is really no sense in doing castings the way they have always been done.

The near-net castings I made for the green twin have really spoiled me.

There is a guy in Europe named Muller Nick (screen name), and he has cast some fantastic engines.
Green, I was able to find "muellernick" youtube channel, but nothing on the model of the full size twin diesel photographed, is there somewhere else I should be searching ?
If you ever decide to do a half-scale of the long neck 2 horsepower, you'd have a 2 x 3 bore and stroke and 12" flywheels. That would make a very nice running engine. I thought that I mentioned earlier that I have some blueprints. About 20 years ago I had the opportunity to photograph many of the original prints used to make the Monitors. There are original patterns, too but they are too fragile to use.
Baker and the Monitor brand of water well components is still very much alive and well. They have an excellent foundry. They actually cast some engine parts, off of new patterns, for a friend a few years ago.
The Baker built Monitor engines are really very simple and almost crude. They come from a time when things had to be simple in order to be considered reliable. Because Baker had a very well established foundry, there are many things on their engines that were cored and cast instead of drilled. For example the main bearing caps on the horizontal engine are held on with carriage bolts in cored holes instead of studs.
Whatever happened to the patterns that Bob Bromps had for his Monitor model? It was a nice looking engine and then he just sort of disappeared. It's a shame that they are out of circulation. I'd love to buy a set of his castings.
The 2hp Ball Hopper Monitor is very close to the 4hp in design, so it would probably not take too much effort to make both sets of patterns.

The larger gear is offset to one side on the 2hp, but otherwise the engines seem very close in design.

The 2hp is a smaller engine, and would be a smaller model I guess, depending on how you scaled it.

With 3D printing, you can print a pattern at any size, however, you have to revise shaft and gear sizes, and fastener sizes, to get back to something standard, when you change scales.

Whatever happened to the patterns that Bob Bromps had for his Monitor model? It was a nice looking engine and then he just sort of disappeared. It's a shame that they are out of circulation. I'd love to buy a set of his castings.

Maury, who ran Lone Star Castings company, and made castings for a 2hp Ball Hopper Monitor, knew some of the story behind the Pacific Monitor casting kit company, but I forget all the in's and out's.

Apparently Bob was not able to fulfill all of his orders; at least that is the story I have heard, and I have no verification of that; we will leave it at that.

I really liked the Pacific Monitor kit, and I especially liked how the flywheel spokes looked.
The Pacific kit seemed to hold very close to the original 4hp engine too, best I can tell.

Maury based his design on a 2hp Monitor, and his flywheel spokes are not quite like the original engine.
Maury's ball hopper monitor kit was otherwise stellar, and the set of gray iron castings I purchased from him were extremely high quality (some of the best castings I have ever seen).
Maury's drawings were also excellent.
I sold my Lone Star Ball Hopper gray iron casting kit to someone up north, since I really wanted a larger scale ball hopper monitor; ie: a monitor with flywheels between 10" and 12".

I think Maury sold his patterns and such to another company, which apparently has since ceased production ?

I think the Pacific ball hopper patterns may have also changed hands, but have apparently gone the way of the dodo.

I am going to make a set of patterns for the Ball Hopper Monitor, with 12" flywheels, and make sure these patterns don't vanish from the face of the earth. I will have the engine in a 3D model, and I will probably send this to several folks, just to make sure it does not disappear.

I may also end up making a set of patterns with 10" flywheels, but I would not go smaller than that.

I don't want to go into the casting kit business, but I do want to save some of these old iconic hit and miss engine designs for modelers of the future, and so that is my goal.

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Joe, if you are wanting the Bob Bromps engine just to run rather than build I know of a completed one for sale, it is in the UK. Built to a high standard on sled with S/S ignition.
Joe Prindle said "The Ball Hopper engine is a pretty simple engine design".

That may be true in theory, but the pattern work for this engine has a LOT of subtle things going on that can be seen if the photos are studied carefully. There are very few flat surfaces anywhere on this engine.

The valve chamber is a work of art in and of itself, and it will take a while just to get that modeled correctly.

There are a lot of curved surfaces, convex surfaces, bosses everywhere, etc., and when the draft angles get added on the the appropriate places, then the 3D modeling work definitely will give you a mental workout.

I am feeling good about the 3D model so far, and I don't see any "show stoppers" yet.

Here is today's assembly.
Making progress.

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