Ball Hopper Monitor Patterns/Castings Attempt

[Casting Iron]

I have photos of a red and gray 4hp BHM.
One shows a stop that is radial, on the top of the governor weight (the red engine), and the gray engine does not have this stop, but instead has a C-shaped boss on the inside of one flywheel spoke.

I am going with the gray engine design; ie: the C-shaped stop that limits the travel of the unhinged end of the governor weight.

The governor weight needs some fillets added, as you mention.

I am working on an assembly of the crankcase, crankshaft, crankshaft bearings, gears, flywheels, and valve chamber, so I can coordinate vertical alignment of the centerline of the exhaust valve stem down to the associated boss on the top of the rocker arm.

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[Casting Iron]

I noticed that I scaled this engine by 14/12, to get to 1/2 scale.

This threw off the exact shaft size of the crankshaft, so I make a new 3D model for it.
I noticed from photos that the crank webs are tapered, apparently with a curved surface taper, which would mean the original crankshaft was cast.

I add the curved taper to my crankshaft webs, since I intend to cast it in ductile iron.

I worked round-robin, starting at the crank pin, crank pin bearing, then the main crank bearings.

That is as far as I got.

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[Casting Iron]

I tried to get to the point where I can create the 3D model for the rocker arm last night, but there are many things that touch/interact with that arm, and the exact location of those items needs to be determined, before the work on the arm can start.

To that end, I continued with the frame/crankshaft/bearings/flywheels/gears/valve chamber/frame/valve pushrod assembly.

Things seem to be lining up pretty well, especially the position of the exhaust valve pushrod over the area where the cam will go.

The proceedure is to add one component at a time to the assembly, and check the movement/rotation of the moving parts after each part is added.

I have not built a hit-and-miss engine before, so this is new ground for me.
Even though I can watch the video of a 4hp engine operating, it is still taking me a while to get a good understading of the exact relationship and timing between all the moving parts.
Lots of new synapse connections have to be made in this old brain.

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[Casting Iron]

Governor weight added.
The end of this weight needs to be tweeked to match the stop that is on the inside of the spoke, and the ball at one end needs to be shaped to match the spoke.

I was confused about the exact center-to-center distance on the gears, and so I pulled in drawings for the exact gears that I will be using from McMaster Carr, and inserted those into the model.
I am assuming that the pitch circles touch, and that determines the center-to-center distance ?

I roughed in the cantilevered gear support shaft shaft, and need to adjust its position, and add the boss for it onto the side of the crankcase.

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[Jasonb]

Pat, I've not seen those two "stops" on an engine can you post a bit of the photo you saw them on, either here or on yours. I could not see it on barney's photos if that is the grey one you mention.

Looks like you need to cut the slot for the pivot end of the governor deeper as it looks to be hitting the edge of the spoke.

For drawing purposes add the PCD of the two gears together and divide by 2 to get the gear ctrs. When it comes to actually making the engine you want to set it up with a little backlash, I use a depthing method with teh small gear on a dummy crank and the big gear mounted in the mill bring the two gears together with a strip of copy paper between then and zero the DRO when they turn freely by hand.

[Jasonb]

Also reduce the diameter of the flange on the crankshaft bearing so it sits lower than the valleys of the small gear and also turn a similar dia shallow spigot onto the inside edge of the flywheel. This saves the larger gear from running against the bearing or flywheel if there is a bit of play. You can see those gaps on Barney's.

[Casting Iron]

Also reduce the diameter of the flange on the crankshaft bearing so it sits lower than the valleys of the small gear and also turn a similar dia shallow spigot onto the inside edge of the flywheel. This saves the larger gear from running against the bearing or flywheel if there is a bit of play. You can see those gaps on Barney's.

I see that; will do.
Keen eye.

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[Casting Iron]

Looks like you need to cut the slot for the pivot end of the governor deeper as it looks to be hitting the edge of the spoke.

The governor weight needs to be tweeked in several places.
I had not noticed the conflict with the spoke and the slot.
This is where it would be nice to have a 3D printed piece in hand, for comparision.
I will physically mate the patern halves for the governor weight with the pattern halves of the flywheel, and grind/shape accordingly.

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[Casting Iron]

Pat, I've not seen those two "stops" on an engine can you post a bit of the photo you saw them on, either here or on yours. I could not see it on barney's photos if that is the grey one you mention.

It is a trick to see the C-shaped boss, but it is indeed there, and provides positive stop in two directions, which I like.
I may cast the boss solid, and then hand-grind the slot in it, so it fits exactly with things "as-cast".

There is no stop on the top of this goververnor weight, but there is a stop on the top of the red governor weight.
Slight variations between the same model and manufactuer of a 4hp BHM.

Also I can see a ridge on the top inside of the gray governor weight.
I don't have that in my model yet, but I can see it.

The knot you can see on top of this weight is actually the bolt that secures the spring.
One the red engine, you can see the bolt, and a stop boss on top the weight.

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[Casting Iron]

For drawing purposes add the PCD of the two gears together and divide by 2 to get the gear ctrs.

Got it, thanks.
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[Jasonb]

I can see it now, did not have that photo.

I'm not sure if it is a step on the outer surface or just the part line?

Does Solidworks not show any clashed on an assembly?

[Casting Iron]

Does Solidworks not show any clashed on an assembly?

The motion study only seems to lock up if there is not a clear rotating fit.
You can have parts that don't fit exactly, as long as they don't rotate.

There are more extensive motion studies, but I only have the stock one that came with SW.
It is very useful though, since if you have rotating parts that are off, the assembly locks up in motion study.

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[Casting Iron]

I'm not sure if it is a step on the outer surface or just the part line?

It looks like the ramp is thicker on the hinge side, and then thins out towards the non-hinged side.
I am thinking that they added a ridge so that they could machine it off true and round.

Edit:

The outside surface of the governor weight would have to be machined concentric, and if the ridge where not there, then there would be a visible groove/flat across part of the top, but that line is not visible.

What is visible is a flat-topped ridge.
During the machining process, I think they bolted the governor weight into a jig, and machined the top of the ridge concentric.

This is from the video, slowed down as much as possible, and on the highest resolution.

[Casting Iron]

Here is a photo that shows the ridge one the top inside of the governor weight.

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[Casting Iron]

There is more to this rocker arm than meets the eye.
I have a parting line down the center, so everything has either curvature or draft angle in the direction of the parting line.
Making patterns takes a lot longer than making a part with no draft angles.

And the "coordination factor" is high on this part (I am making these terms up as I go); ie: this part has to align precisely with a number of other parts, bosses, etc.

Next step is to plug it into the 3D model, and see what needs to be adjusted.

I don't really have any clear photos or video views of this part, so this is the best I can do as far as having an accurate look.

For small intricate parts, I am starting to think about centrifugal casting, or perhaps just vacuum assist.

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