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Harvard model by B P machine ohio

wbunett2922

Registered
Any one have any information about harvard model built by B P machine in ohio. trying to understand how valve system works also seems to be timed a bit to far advanced how is this adjusted?
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
I have one of these that was machined by another person. It is mostly complete, but needs some work before it will run. I've just started working on it and have it mostly disassembled now. I've identified several issues (well, about 20) that need to be corrected before I can try to run it.

I'm familiar with the full size Harvard/Stickney Jr. engines. The valve system is interesting and unique. There is but a single valve going into the cylinder. This valve is driven off an eccentric on the secondary shaft, and is open through both the exhaust and intake cycles. It should be timed so that it starts to open just before BDC at the start of the exhaust cycle, and starts to close right around BDC at the end of the intake cycle. The timing is affected/controlled by 3 things:
1. The way the gears mesh (this is a fairly coarse adjustment)
2. The position of the eccentric on the secondary shaft (I think the eccentric has a set screw)
3. The length of the pushrod

I haven't looked at the timing on my engine yet. I have a whole bunch of other issues to deal with before I get to that. :)

John
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
A little more information about the valve system.

The single main valve opens into a sort of secondary chamber that has two more valves: the exhaust valve and the intake valve.

The exhaust valve is more or less a disk/ring, with a valve seat machined on one side. It is concentric with and slides on the main valve stem. It doesn't have a spring. If the main valve is open (via the eccentric) and there is pressure in the cylinder, the exhaust valve is forced open and the exhaust gas is pushed out by the piston rising in the cylinder. N.B., the exhaust valve is not visible when the engine is fully assembled.

The intake valve is a more or less typical automatic/atmospheric valve. At the end of the exhaust cycle, the piston is at TDC and the exhaust gases have been pushed out. As the crankshaft continues to rotate, the piston begins to move downward. The main valve is still open by virtue of the eccentric. As the piston moves downward, pressure in the cylinder decreases. The exhaust valve disk closes due to its weight. As the piston continues downward, cylinder pressure continues to decrease. At some point, atmospheric pressure acting on the intake valve causes it to overcome its spring pressure, and open. Just like atmospheric intake valves on other hit & miss engines. The air/fuel mixture is drawn in. At the end of the intake cycle, the main valve closes and the compression cycle begins.

There is a third valve, which I call the governor valve. It acts as a sort of on/off throttle. When the engine RPM is below the governor set point, the valve is open and allows the air/fuel mixture to flow through a passage to the intake valve. When the engine RPM reaches the governor set point, an arm holds the valve closed so air/fuel cannot flow on the intake cycle. The main valve continues to operate normally and the engine coasts against compression, unlike a typically hit & miss where the exhaust valve is held open when the set speed is reached.

The governor valve is a little strange, in that the seat is on the face of the valve, rather than on the stem side. So when the valve is up, it's actually open and when the governor arm pushes it down, it's closed.

I guess that's enough for now. I hope some of it makes sense. :)
John
 

wburnett2922

Registered
A little more information about the valve system.

The single main valve opens into a sort of secondary chamber that has two more valves: the exhaust valve and the intake valve.

The exhaust valve is more or less a disk/ring, with a valve seat machined on one side. It is concentric with and slides on the main valve stem. It doesn't have a spring. If the main valve is open (via the eccentric) and there is pressure in the cylinder, the exhaust valve is forced open and the exhaust gas is pushed out by the piston rising in the cylinder. N.B., the exhaust valve is not visible when the engine is fully assembled.

The intake valve is a more or less typical automatic/atmospheric valve. At the end of the exhaust cycle, the piston is at TDC and the exhaust gases have been pushed out. As the crankshaft continues to rotate, the piston begins to move downward. The main valve is still open by virtue of the eccentric. As the piston moves downward, pressure in the cylinder decreases. The exhaust valve disk closes due to its weight. As the piston continues downward, cylinder pressure continues to decrease. At some point, atmospheric pressure acting on the intake valve causes it to overcome its spring pressure, and open. Just like atmospheric intake valves on other hit & miss engines. The air/fuel mixture is drawn in. At the end of the intake cycle, the main valve closes and the compression cycle begins.

There is a third valve, which I call the governor valve. It acts as a sort of on/off throttle. When the engine RPM is below the governor set point, the valve is open and allows the air/fuel mixture to flow through a passage to the intake valve. When the engine RPM reaches the governor set point, an arm holds the valve closed so air/fuel cannot flow on the intake cycle. The main valve continues to operate normally and the engine coasts against compression, unlike a typically hit & miss where the exhaust valve is held open when the set speed is reached.

The governor valve is a little strange, in that the seat is on the face of the valve, rather than on the stem side. So when the valve is up, it's actually open and when the governor arm pushes it down, it's closed.

I guess that's enough for now. I hope. some of it makes sense. :)
John
Thank you for info I adjusted push rod and seems to run better. The timing of spark is a problem the only way I can see is to change gap in order to retard there doesn't seem to be any way to move cam.good luck on your build my engine seems to have been run a lot perhaps new points would help but I don't have a clue as what where they are. Bill Burnett
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
Thank you for info I adjusted push rod and seems to run better. The timing of spark is a problem the only way I can see is to change gap in order to retard there doesn't seem to be any way to move cam.good luck on your build my engine seems to have been run a lot perhaps new points would help but I don't have a clue as what where they are. Bill Burnett
Bill,
1. Are using ignitor or spark plug for ignition?
2. Do you have the drawings that came with the original kit?

John
 

wbunett2922

Registered
Bill,
1. Are using ignitor or spark plug for ignition?
2. Do you have the drawings that came with the original kit?

John
spark plug altho there is what looks like ignitor on side of engine no drawings I am sure this engine was made by BP machine in ohio there is a tag on base They seem to be gone
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
If you have spark plug ignition, the ignitor is just for show. Mine doesn't have a spark plug fitted. If a spark plug is used, the plans call for "older Chevrolet adjustable ignition points" mounted on a bracket under the center of the engine base. It says the points have an Allen screw for adjustment, so apparently that's how you adjust the timing. The plans also call for use of a "Chrysler resistor" to keep the points from burning. If your engine was built by BP Machine or sold as a mechanic's kit, that's probably how it is set up. If it was built by a hobby machinist from a casting kit, it might have something different. I'm planning to fit mine with a Hall sensor for electronic ignition.
For timing, it says to set ignition approximately 3 degrees BTDC if using Coleman fuel, or 5-7 degrees if using gasoline.
 

wburnett2922

Registered
If you have spark plug ignition, the ignitor is just for show. Mine doesn't have a spark plug fitted. If a spark plug is used, the plans call for "older Chevrolet adjustable ignition points" mounted on a bracket under the center of the engine base. It says the points have an Allen screw for adjustment, so apparently that's how you adjust the timing. The plans also call for use of a "Chrysler resistor" to keep the points from burning. If your engine was built by BP Machine or sold as a mechanic's kit, that's probably how it is set up. If it was built by a hobby machinist from a casting kit, it might have something different. I'm planning to fit mine with a Hall sensor for electronic ignition.
For timing, it says to set ignition approximately 3 degrees BTDC if using Coleman fuel, or 5-7 degrees if using gasoline.
Thank you for info points on mine are adjusted with a screw don't know why there would be resistor there is buzz coil mounted under base will look for new set of points now that I know what thanks to you .condenser is what keeps points from arcing and buzz coil don't work with out them hall effect sounds good thanks again. Bill
 

wburnett2922

Registered
Thank you for info points on mine are adjusted with a screw don't know why there would be resistor there is buzz coil mounted under base will look for new set of points now that I know what thanks to you .condenser is what keeps points from arcing and buzz coil don't work with out them hall effect sounds good thanks again. Bill
Points under water tank and rest of engine are very unhandy to get to if possible I would hide hall effect somewhere else
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
Bill, can you please look at your engine and tell me if the connecting rod is straight? Mine was made with an offset. The centerline or axis of the cylinder/piston does not coincide with the center of the crankpin. It's as if the cylinder is about 0.180 too close to the flywheel end of the engine. So the builder put an offset in the connecting rod to compensate. So far I've been unable to find anything that could explain it. I've checked the relevant dimensions, and everything seems OK. There's nothing that could explain it being that far off.
John
 

wburnett2922

Registered
Bill, can you please look at your engine and tell me if the connecting rod is straight? Mine was made with an offset. The centerline or axis of the cylinder/piston does not coincide with the center of the crankpin. It's as if the cylinder is about 0.180 too close to the flywheel end of the engine. So the builder put an offset in the connecting rod to compensate. So far I've been unable to find anything that could explain it. I've checked the relevant dimensions, and everything seems OK. There's nothing that could explain it being that far off.
John
Sorry didn't get back sooner but picked up new project last night 11pm my Harvard connecting rod appears to be straight from what I can see .set it up temporarily and that might give you a reason why .models are not always perfect and sometimes you have to make up for a o shit moment Bill
 

JohnMN

Subscriber
Last Subscription Date
07/12/2019
Here's a picture of the top of my engine. I think it's missing some parts or something that would hold the main valve guide down. Otherwise, I think the valve guide would have a tendency to "pop up" on the exhaust stroke. Bill, can you please look at your engine and see if I'm missing something? Would it be possible to post a picture or two?
Thanks, John
IMG_20200314_125848140.jpg
 

wbunett2922

Registered
Here's a picture of the top of my engine. I think it's missing some parts or something that would hold the main valve guide down. Otherwise, I think the valve guide would have a tendency to "pop up" on the exhaust stroke. Bill, can you please look at your engine and see if I'm missing something? Would it be possible to post a picture or two?
Thanks, John
View attachment 386728
will try to send picture this eve not at home now also will try to send picture
 
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