Ball Hopper Monitor - Casting Project

[GreenTwin]

Nobody has ever been able to explain the short neck/long neck styles on the Ball Hopper Monitor, but looking at the photos, it is clear that some of the water jackets stop above the top of the flywheel, and some stop below the top of the flywheel.

According to company literature, some BHM models could be purchased with an option between two sizes of flywheels, which could make the cylinder look taller or shorter.

The company literature seems to consistently list one bore and one stroke for each type and horsepower of engine.
You would think that if two different strokes were offered for the same engine, the catalog would list that.

The longneck engine (that is the slang term for it) seems a bit overly tall.
The shortneck looks about right to me, so I will design around a shortneck design.

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[GreenTwin]

Since the Ball Hopper Monitor has points, it looks like it has a separate cam to actuate the points.

The points could be actuated by a screw in the side of the main cam, but having a separate cam for the points would allow the vavle timing and the points timing to be easily and independently adjusted.

The 4 hp BHM appears to have a rocker arm, that has a roller that rides on the main cam.

The weight in the flywheel actuates the catch that holds the rocker arm up (holding the exhaust valve open) when the engine exceeds a certain rpm.

The spark plug would continue to spark regardless of whether the exhaust valve is being held open or not.

The larger gear on the 4hp is directly centered above the crankshaft, and the larger gear on the 2hp is not centered over the crankshaft, but rather offset a bit to one side.

I guess the BHM design evolved over time, but if I were designing BHM's I think I would use the same design and just scale it up, unless there was some sort of compelling reason to do otherwise.

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[GreenTwin]

Sort of a wishbone weight in the flywheel, with a spring towards the flywheel center radially at the end of the wishbone weight.

The cam is built integral to the large gear, and is on the inside of the gear.

Since we are actuating points with a separate cam, the exhaust cam should be able to be a simple symmetrical design with a constand radius plateau.

One factory sheet says the exhaust valve opens 36 degrees before bottom dead center, and closes 3 degrees after top dead center.
The plateau on top of the exhaust cam needs to be wide enough to produce these timing events on the exhaust valve, ie: the plateau width determines the duration that the valve remains open.

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Edit:
If the exhaust valve opens at 36 degrees BTDC, and closes at 3 degrees ATDC, I think that is giving degrees of crankshaft rotation, not degrees of camshaft roation. Total rotation would be 129 degrees of the crankshaft.

If the camshaft is rotating a 1/2 the speed of the crankshaft, then would you double the crankshaft degrees to get camshaft degrees, and thus give the camshaft degrees required to cut the cam plateau width ?

Edit2:
Perhaps the angle on the camshaft travel would be 1/2 the crankshaft travel ?
So the cam plateau would be across 64.5 degrees ?

Edit3:

A reasonable amount of lift would seem to be about 0.3".

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[GreenTwin]

I forgot I purchased this little Baker pumpjack engine a few years ago.

The guy said "How you going to get it into your van?".

I said "Stap it to a 2-wheel dolly and winch it in".

I will go look at this cam.

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[Jasonb]

Cam duration is not just the length the valve is fully open subject to any lash and the shape of teh follower duration will be where the flank of teh cam starts to where the opposite flank ends, if you take a radial line out to the tangent of where the flank meets the base radius on each side and measure the angle between the two that will give you a good idea of cam duration.

"Contacts "is a better name than points a sthat is usually associated with the type of points found on a car. Points fire as the two parts separate, a buzz coil or modern CDI will fire when th econtacts come together which will make a lot of difference..

 

[GreenTwin]

This is the cam from the Alan Shelley-drawn 1/3 scale Galloway drawings.

In the first photo, the cam is symmetrical at the top, ie: 1/8" either side, 1 13/16 either side, 2" radius either side.
Only one side of the top of the cam will actuate the ignition contacts, and so once that is fixed, then the other two contact points for the roller/cam contact have to be adjusted accordingly to allow the valve open at 36 degrees BTDC, and close at 3 degrees ATDC.

The bottom of the cam is almost symmetrical, but not quite.

1/4" offset to either side, but the centerpoint distance from the shaft centerline varies from 9/16" on the right to 19/32" on the left.

So it appears the are shaping the cam to give the 36/3 degree valve points.

This could be mocked up in a 3D modeling motion study, to verify if these cam dimensions actually give the valve open/close positions stated on the Galloway drawings.


Edit:
Putting the drawing below into CAD, it appears it is not as symmetrical as it would seem.
Rather tricky little drawing.

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[GreenTwin]

Cam duration is not just the length the valve is fully open subject to any lash and the shape of teh follower duration will be where the flank of teh cam starts to where the opposite flank ends, if you take a radial line out to the tangent of where the flank meets the base radius on each side and measure the angle between the two that will give you a good idea of cam duration.

"Contacts "is a better name than points a sthat is usually associated with the type of points found on a car. Points fire as the two parts separate, a buzz coil or modern CDI will fire when th econtacts come together which will make a lot of difference..

I would set it up with points, a condenser, and a coil, just like on the old automobiles.

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[GreenTwin]

I don't have good photos of a full sized 4hp BHM valve gear/cam arrangement.

Makes it a bit challenging.

I need to figure out the dimensions of the roller that rides on the cam, and then work backwards from there to figure out the exact profile of the cam that produces the exhaust valve events we want.

I nice 3D model of the BHM would be nice, but I have not seen one of those.

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[GreenTwin]

JasonB's video gives a birdseye view of the 4hp scale model valve gear in action.
See 0:14.

Very helpful; thanks JasonB !

Edit:
Not sure if I am using the correct terms, but it looks like the follower gets pushed up and latched in the up position.
The follower stays latched up until tripped into the down position by the flyball in the flywheel.

The flyball is moving fast, so it is difficult to see what is happening with it.

Looks like the rocker arm hinge point is on the left (facing the flywheel), and it pivots parallel to the flywheel.
The trip latch is hinged on the right side, and it pivots perpendicular to the flywheel.

The pushrod going up to the bottom of the valve almost seems to be floating in free air.
I would have thought the guide for that pushrod would be much longer.

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[GreenTwin]

The weight in the flywheel seems to be a very simple arrangement.
Weight is hinged on the right, with a spring to hold in in towards the hub.

As the engine speeds up, the weight overrides the force of the spring, which moves the weight outward, and releases the trip mechanism.

See 0:34
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[GreenTwin]

Here is a Lister with what looks like a slightly heavier flywheel than the BHM.

 

[GreenTwin]

Here is Barney's attempt to cast one half of a muffler for a BHM.

His gate is way too small for such a large thin part.

He needs a ring runner, with multiple knife gates.

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[Jasonb]

When the engine is running and missing the weight will make the latch hold the valve open each time it comes round. The latch is released every time not just when the engine is slowing but will hold the valve open again if the speed and weigh are going fast enough. Basically the load is taken off the arm every time as the valve rod moves to the release point on each cycle. It's a very small amount and hard to see on the video, Weight engages the latch, cam lifts the rocker arm and disengages the latch.

Watch the Gade running you can see that the latch gets released as the rod moves more than teh latch distance but engages again on the miss strokes and every few will allow the rod right back so the valve is closed on the inlet stroke thus making the inlet mave open due to vacuum in the cylinder, slightly different on tha gade as the latch arm is held all the time not just when the weight comes round



May be easier to see on the R&V which uses a similar weight to the monitor, the latch lever moves every time but only on the hit does it move further out to allow the rod to move enough to close teh valve

 

[GreenTwin]

I made more progress on the ball hopper monitor project.

I found some pretty good photos of a 4hp BHM, and a few old factory catalogs, and so that is helping quite a bit.

I also found a few photos of a partially disassembled BHM.
Those photos are exceptionally rare.

I have been drawing a 4hp BHM in 2D CAD, trying to capture some accurate full-sized dimensions.

The 2D drawing then has to be scaled down, in this case by about 0.42, to get a 12" diameter flywheel.

I found someone who owns a 4hp BHM, and he sent photos with a measuring tape held in strategic places, so that is helping a lot.

JasonB has toyed with projecting the "Monitor" logo onto the side of the fuel tank.
See Jason's posts # 17, 22, 31, 38, etc.

I have never had much luck projecting spline-generated text in Solidworks, but last night I decided to give it a try.

First I tried projecting plain text onto a curved surface, and I got that to work.

Then I imported the "Monitor" logo that I traced, and projected that onto a disk.
That worked well enough (not perfect, but ok), and so I decided to mock up a fuel tank to scaled dimensions.

Solidworks does not like to extrude objects that have a lot of splines in them, and this extrusion was no exception.
I finally got a partially correct extrusion, which I inserted on a flat plane, and then extruded into the tank.
Then I used a circle to cut off the logo to within about 0.125" of the tank surface.

Not too bad for a quick attempt.
I still have some work to do on the logo tracing; I am not really pleased with the smoothness of the lines yet, and will try tracing it again.

Looking at photos of the full-sized 4hp fuel tank, the logo is not located on the centerline of the tank, but rather offset up from the centerline.
This makes for an interesting challenge to get the sides of the text to act somewhat normal; ie: not have too much draft one way or the other.

I think the best approach is to extrude the logo directly onto the tank centerline, and then rotate the tank, before adding the fill boss, etc.
Rotating the tank rotates the text, and adds an angle to its sides, but I will be manually filling around the text anyway, so that does not matter.

I think I will be able to get a pretty decent looking logo into the 3D model of the tank, and then I should be able to make a 3D printed pattern of the tank, in pattern halves (left side, right side of tank).

I have a bit more work to do with the center of the "O", which would not extrude hollow, but I think I can get that fixes.
I was a bit worried about how I would make the logo on the tank in 3D, but I believe I have found a method that will be sufficient for what I need (a casting).

 

[GreenTwin]

After the 2D drawing has been scaled down from full size, the various parts have to be normalized in size.

The flywheel is the driving factor, and it scales down to exactly 12" diameter.

The other parts have to be normalized, so they are not some fragmented odd dimension.

I have inserted drawings of the gears I purchased into my 2D CAD drawing, so I can design around those, and make sure the engine will function properly with a commercially available gear set.

The plan is to pour babbitt crankshaft bearings, and I have the babbitt and the high temperature puddy for that.
The original BHM engines were furnished with babbitt bearings.

I am excited about being able to make some significant design progress on this engine.
This has been a very longtime dream of mine, and only recently have I felt like I had the confindence to attempt to cast it.

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[GreenTwin]

I used splines to trace over a "Monitor" logo photo, and unfortunately I used a lot of points in each spline.

This is giving my extruded logo a rather choppy look, so I will try retracing, using as few points as possible, to give smoother flowing splines.

Here is a re-traced logo.
I tried to keep as few points along the splines and other lines as possible, and I think the result looks much smoother.
It behaves much better in Solidworks too, with no problems with the "O's" displaying correctly.

I am happy with this.

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Not my photo, but shown for comparison.

 

[GreenTwin]

Touched up the logo a bit, trying to get it more consistent between letters, and more consistent letter thickness.

Adjusted a few curves and stroke weights.
The pen strokes are non-linear.

There is a lot going on in this sketch.
Every line/spline has to be snapped to the next line.
SW is totally intolerant of any slight imperfection.

I think this is the best I will have time for, but I think it looks ok, and it looks less blocky than the previous revision.
This one captures the "logo look and feel" pretty well I think.

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[GreenTwin]

And extruded onto the tank.
I think this will work, and can be 3D printed.

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[GreenTwin]

I found a cleaner graphic of the logo, and so I decided to try to sketch it yet again.
The one I did above looks ok, but not really close enough to what I seen on the full sized Monitors for my liking.

I think this one is very close to what you would see on a full sized engine, best I can tell from photos.

There are a LOT of very subtle curves and things going on in that logo.
It is very hard to get the swooshes looking visually correct.

I think this will be the final version.

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[GreenTwin]

Here is a full sized 4 hp fuel tank.

Close enough for me.

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