Ball Hopper Monitor - Casting Project

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.
I probably need to pick a gear set from McMaster Carr, and design outwards from that.

McMaster Carr has a 72 tooth at 3.08 inch diameter, and a 36 tooth at 1.58 inch diameter, both 24 gear pitch.
Problem is they are only .25" thick, which is a bit on the thin side.

I do have a set of gear cutters.

The problem with McMaster-Carr gears, specifically the small one, is that the hub is not sized very generously, and really needs to be larger in diameter.

I am thinking a custom-cut gear will be required to get the desired gear thickness and hub diameter.

You don't need any hub on the gears, an unbossed one will do for both. Crankshaft gear is just keyed to the shaft, cam gear bolts to the cam/shaft assembly

If you are going with a 12" flywheel then you will have to play with th etooth count, 34/68 at 24DP will be the right PCD

Try som other suppliers you should be able to get thicker, one I tried here ha sthem 0.312" thick which will be about right.

EDIT cheap set of imported 1MOD gears will be spot on and keep the 36/72 tooth count as per original
Found some gear pitch 20, 60/30 tooth, 0.5" wide face width, 3.1"OD/1.6"OD.

I think those would work.

The cool thing about McMaster-Carr stuff is you can download 2D drawings and 3D models, in a variety of file formats.
That makes importing the design really easy, into either a 2D program, or a 3D program.


Last edited:
Ideally you should try and keep the same tooth numbers as the original if you want to do a proper job.

Does your Solidworks not have a gear generator like Alibre and Fusion?
I think it would be better to buy gears, and not get bogged down with making them at this point.
I could design it where I could change out to 72/36 gear later, maybe?

I looked at the photos of the various Ball Hopper Monitors I have, and it seems like the horsepower mimics the number of bolts holding on the valve chamber; ie: 2-bolts is 2hp, 4-bolts is 4hp, 6-bolts is 6hp or more.

And the spark plug varies depending on the horsepower.
The larger engines seem to have both valves down, and spark plug on the side or top of the valve chamber.

One engine has one valve down, one valve up, spark plug on the side.

The 2hp and 4 hp engines all seem to have one valve up, one valve down, spark plug straight out the front.

The 2hp has the spark plug centered between the two bolts.

One of the 4-bolt ones has a priming petcock between the two upper bolts facing out, and the sparkplug on the left side.

It seems like the 2hp is the only design with the spark plug on the front, if my assumption about the bolts is correct.

The larger engines have the spark plug either on the left side, or top.

Makes me wonder why the Pacific castings had the spark plug on the front.
Is that a mistake, or just one more variation in a log list of variations.

I am guessing the Ball Hopper Monitor design evolved over time? much as can be seen with the Dake engine.

A little more research on the Baker company and their gasoline engines reveals more information, although much of it seems conflicting.

They manufactured horizontal engines at 3 hp (4" bore), 5 hp (5" bore), 8 hp (6" bore), 11 hp (7" bore), and 15 hp (8" bore), all horizontals.
I think the designation for horizontal engines began with "H", and the Type was "HJ" on the nameplate.

The designation "J" appears to refer to "Jump-Spark" ignition.

The designation "V" is vertical engine, and these included the ball hopper type, and the vase-shaped engines.
Baker does not seem to make it very clear why they made two varieties of vertical engines, at least it is not clear to me.

The typical vertical vase-shaped hopper small pump jack engine you see so many of were 1 1/4 horsepower, and were referred to as the "Little Monitor Pumping Engine".
This engine had a single flywheel, with a headless design, and valve cage cast into the cylinder.

The vase-shaped hopper engines I think had a model number such as "VJ", and apparently came in 1 1/4 hp (3.5" bore), 2 hp (4" bore), 4 hp (5" bore), and 7 hp (6" bore).

The Baker company seemed to be very consistent with their piston sizes, and it appears the piston size and maybe to some extent the stroke, drove the horsepower rating.

The ball hopper engines apparently also came in 2, 4, and 7 horsepower, and I am not sure if they used the same piston and piston size as the vase-shaped vertical engines.
I have seen references to a 1 hp and 6 hp ball hopper monitor, so I don't know if that was just a variance in stamping the nameplate rating for a particular application, or what.

Comparing the bore sizes between the horizontal and vertical engines, the horizontal engines produced more horsepower for the same piston diameter, for some reason.

One photo of a Monitor nameplate shows an "RV" designation, but I am not sure which engine that nameplate goes with; listed as 1 5/8 horsepower.

The nameplates on the vase-shaped vertical Monitor clearly says "Type VJ".

I can't find a photo of a ball hopper monitor nameplate, but it would appear that they were elipsoidal in shape, located on the side of the cylinder opposite the valve cage.
One nameplate photo shows a rectangular nameplate, but I am not sure which engine this goes with.

I am assuming that the ball hopper monitor nameplate did not have a "Type", but just a horsepower, rpm, and maybe a serial number (not positive about this).

There is a lot of information available for the Little Monitor vase-shaped hopper, and many photos.
Apparently everyone and their brother and cousin had a Little Monitor pump jack engine.

Ball Hopper Monitor information seems to be rare, sort of like finding snow in hell, and very few ball hopper engine photos or videos.
Finding photos of a disassembled ball hopper monitor are exceedingly rare.

The spark plug appears to be on the front of the valve cage on the 2hp, and on the left side of the valve cage on the 4hp (check me on that).
For the larger vertical engines, where both valves are on the bottom, the spark plug appears to be on the top of the valve cage.

The larger engines have both valves actuated to give 10% better fuel economy.
Last edited:
I read a description in their company bio about the windmill display that set up at the Chicago Exposition I think in 1896, and they won some sort of award for engineering excellence.
Their windmill sales I think took off after that.

I would like to make a windmill, but that would be another hobby which I don't have time for.

I did try to cast a gear for a guy who was restoring a windmill.
I was not successful, but I think I know how to do it now.

To make matters more confusing, I found a clear photo of a 4 hp ball hopper Monitor, and it also says "Type VJ", just like the vase-hopper engine.
I always thought VJ was for the vase-top only engine, but that is not true.
"V" appears to be the designation for all of Baker's vertical engines, regardless of the hopper style.
Last edited:
There is a guy in Europe named Muller Nick (screen name), and he has cast some fantastic engines.

The last build he was working on before he crashed his bicycle and broke his wrists (I think this is the right timeline) was this engine.

He would put the tape on it as datum points, take pictures from all around, and then use software to generate a 3D model of the engine.
He went to this museum and asked them if he could tape and photograph this engine.
The museum folks of course said "Absolutely not", and so he showed them one of the engines that he had cast, and said "I am going to tape and photograph this engine. I need you to be out to lunch for an hour and not be aware of anything I do".

So he scanned this engine.
I will look up his ytube channel.
These are his photos.
I learned a lot from Nick.

When it comes to home casting engines, Nick sets the bar pretty high.

He shows a lot of examples of intricate core work, which almost always get left out of model engine castings.

I received the 0.5" gears I ordered today.
These are 20 degree pitch pressure angle, 20 pitch, 30 and 60 teeth respectively.

They look pretty good in my opinion, and at a glance seem to fit the scale well, not that I am that familiar with what gas engine gears look like.

I can cut the hub off of them, and maybe drill some holes in the larger one to match what was used on the Ball Hopper Monitor.

This will be my first attempt at a gas engine.
I will design outwards from these gears.

Looks like these gears will give me 2.25" between centers.

I guess I need to draw up a 4hp engine full size, and then scale it down, in case I want to cast a full sized engine.


Last edited:
2.25cts will give you a flywheel of 12.65" on a 4HP if based on the 9" dia of the 1/3rd scale model or just over 13 if taking the flywheel as 28" measurement.

The majority of the casting sets that are/were about had the patterns made by people who either owned or had access to the actual engine which makes life a lot easier than trying to do it by internet images. Nick's engines being a good example of how access allows the builder to take the sizes they want and photos square on. did some patterns for a Robinson paraffin engine earlier in the year and were lucky to have the guy at the museum take load sof images with a tape measure in them and he also took some of the engine apart to show details we would never have got just from the outside let alone the couple of images that were on the net. Yes a lot rarer than even a ball hopper monitor, probably the only one existing.
Ater some digging, I found the following about the full sized 4hp:

1. Bore 5"
2. Stroke 7"
3. Flywheel 28" x 2.5"
4. Overall engine height 54"

And it appears that the original gears for the 2hp and I think the 4hp were 60/30.

Spark plug on the 4hp is out the left side.
Priming cock in the top front center of the valve chamber.

Large gear directly vertically inline with the crankshast.

So to get from 28" to 12" on the flywheel, multiply by 0.4285714.
Not exactly a round number, but that is the scale factor.

I considered rounding the flywheel up to 14", and going with a clean 1/2 scale, but that is a really bulky flywheel, and I would have to have someone machine that for me, since I have a 12x36.

Scaled dimensions:

1. Bore 2.14" (round to 2.1") (Edit: bore 2.125")
2. Stroke 3"
3. Flywheel 12" x 1" (I will probably increase the width slightly to maybe 1.25" or 1.5")
4. Overall engine height 23.1"

Last edited:
Ater some digging, I found the following about the full sized 4hp:


I considered rounding the flywheel up to 14", and going with a clean 1/2 scale, but that is a really bulky flywheel, and I would have to have someone machine that for me, since I have a 12x36.


You could always 'machine' the OD of the flywheel on your mill - - -
I would have thought rounding the bore from 2.140" to 2.125" would make it simpler if you wanted to buy imperial rings or use an 0 ring. Or make it 54mm and you can get 125cc motorbike rings easily.