Model of a Bessemer Hot Tube Oil Field Engine

[cfellows]

Chuck why is it necessary to pin the rings ,I remember the 2 stroke detroits had a series of exhaust ports and the rings were never pinned.Excellent build by the way.
Vince

I don't know the exact reason. It's generally suggested that allowing the ring gap to line up with the port(s ) can lead to unfortunate results.

I took the engine apart today and could see that the ring ends were pressing hard against the cylinder and the areas 1/8" or so away from the ends was not contacting the cylinder wall. So I took the piston out and honed the outside edges of the ring adjacent to the ring end. The Model Engine Builder article had suggested this was necessary, but I chose to ignore it at the time. The compression seems to be better now, but I still can't get it to run.

I'm going to hook up an electric motor with a belt drive so I can turn the motor over while I fiddle with the fuel adjustments.

Chuck

 

[cfellows]

I still seem to be getting compression leaks past the ring. I don't think it's the gap, but maybe it's getting past some part of the OD. I also measured the width of the ring groove which turned out to be a little over .006" wider than the ring. Don't really know what the affect of that is, but it should probably less clearance. Dang, I sure wish I could use an o-ring, so much easier and seems to work consistently...

So, today, I cut the top off the piston down to the ring groove. I drilled and tapped a 1/4-20 hole in the center of the piston so I can screw on a new piston top. This will make installing a new ring easier. I'm also rethinking the pinning mechanism. The idea I like best for now is installing a roll pin radially that extends out into the ring groove by about half way or less, then cutting a small radius in the side of the ring to fit over the pin. Logic tells me that if I do this fairly close to the gap, it will have less affect on the overall "springiness" of the ring.

Chuck

 

[Brian Rupnow]

Chuck--Is there any particular reason that you can't use a Viton o-ring?---Brian

 

[cfellows]

Chuck--Is there any particular reason that you can't use a Viton o-ring?---Brian

Yeah... from what I've read, sliding past the exhaust port would chew up the o-ring pretty quickly.

Chuck

 

[bobsymack]

Chuck would it be possible to chamfer the port from the inside and clean the sharp edge.

 

[Brian Rupnow]

Yes, Chuck, you are right. I had forgot it was a two stroke.---Brian

 

[cfellows]

Chuck would it be possible to chamfer the port from the inside and clean the sharp edge.

I know that sounds like a reasonable solution, but I think the problem is that the pressure against the O-ring is still going to press the outer edge up into the opening, and while a smooth edge won't cut it, I think the constant beating wears it out in pretty short order...

 

[Rustkolector]

Chuck,
Put your rings squarely in the cylinder and hold the cylinder up to a bright light. Look for any areas of the ring that are not contacting the cylinders squarely. .006" ring side clearance is too much on a new ring. It has to be tighter. When you redo your ring groove, lap the top and bottom faces with a sacrificial ring. Then lap the top and bottom ring faces to a nice polish to fit the groove. Try for .0005" to .0015" side clearance. making sure the ring groove is clean, and has about .010" radial clearance behind the ring. For reasonable compression in a new engine I think you're handicapping yourself with one ring. Two would be much better. I know that ring staking is a pain. Use a small dia. pin so that some portion of the adjacent ring ends form the ring gap.

Jeff

 

[t.l.a.r. eng]

Just a thought for what it is worth, pinned rings are for two strokes with wide slots for cylinder ports, and still need pinned even with bridges across the port "window".
Perhaps if this engine only uses relatively small round holes for ports, it may not need a pinned ring. It takes a window big enough for the ring tension to expand into the window, your ports may not be large enough for this to happen.

May be worth your while to try a regular split iron ring first. Just thinking aloud.

 

[cfellows]

I took the cylinder over to Maury's shop today and he graciously used his (very nice) Sunnen hone to fix up my cylinder. It had a bit of a tight spot in the middle of the bore, but now it's a very nice fit over the whole length.

So, now I'm wanting to add an oil cup to make sure I get enough lubrication. Thought I'd include a drawing of my plan to see if anyone thinks this is about right or if there's a better arrangement?

Seriously, I'm not at all sure this is the best placement of the oil cup in the cylinder and the oil groove in the piston.

Chuck

 

[aonemarine]

Chuck, to pin that ring, drill down thru the top of the piston and insert the pin so half its diameter creates a hump in the bottom of the rings groove then file the inside of the ring to clear it without disturbing the outer portion of the ring gap.....

 

[cfellows]

Chuck, to pin that ring, drill down thru the top of the piston and insert the pin so half its diameter creates a hump in the bottom of the rings groove then file the inside of the ring to clear it without disturbing the outer portion of the ring gap.....

Good idea! If I wind up having to go back to using a ring, I'll give that try.

Chuck

 

[bobsymack]

Chuck ,with it being 2 stroke would the vacuum below the piston cause it to draw in the oil from the cup
Vince

 

[cfellows]

Chuck ,with it being 2 stroke would the vacuum below the piston cause it to draw in the oil from the cup
Vince

Yeah, Vince, that's been brought to my attention on another forum. I'm going to have to make the hole for the oil enter the cylinder where it won't be exposed to the space below the piston.

Thanks...
Chuck

 

[Brian Rupnow]

Chuck--Any 2 strokes I have ever seen use a bit of oil with the gas to lubricate the crank and rod bearings, and inadvertently the piston. Could you possibly do the same and forget about the oil cup?---Brian

 

[cfellows]

Chuck--Any 2 strokes I have ever seen use a bit of oil with the gas to lubricate the crank and rod bearings, and inadvertently the piston. Could you possibly do the same and forget about the oil cup?---Brian

Yeah, I plan to mix oil with the gas. But I kind of wanted the additional insurance of a cylinder oiler to reduce the possibility of wear on the piston since I'm using a steel cylinder.

Chuck

 

[aonemarine]

maybe put a spring loaded bb in the oiler so when the piston travels across it it lifts the bb to give a bit of oil??

 

[cfellows]

I'm beginning to have thoughts of converting this engine to a 4 stroke. I'm thinking I would make it a sideshaft engine and make my own helical gears. I might be able to salvage the cylinder. Just thinkin...


Chuck

 

[cfellows]

Today I tried starting the engine with a glow plug. Turning the engine over with an electric motor, I can get the engine to fire about every other revolution, but it won't run on it's own. At this point I think the problem is one of two things. Either I'm not getting enough compression (there is still a bit of a leak), or fuel mixture transfer passageways are big enough. I think tomorrow I will remake all the brass piping with 5/16" OD pipe and fittings with an ID of 7/32". I'll also have to remake the two check valve assemblies with larger passageways and larger balls. And, I probably need to find another spark plug and try again with spark ignition...

 

[cfellows]

I'm back on the Bessemer. Since I had such good luck with the Hall Sensor ignition on the Vertical Single, I've decided to go ahead and install a Hall Sensor on this engine. I made small, dovetail milling cutter so I could cut a dovetail in the acrylic plastic. This will hold the sensor down since it has a double bevel on the face that will slide under the edges of the dovetail.

Here's the bare sensor in place.

And here it is with the wiring attached.

I've since epoxied the sensor to the piece of acrylic. I tested it in place with my test circuit and the sensor is still working. Tomorrow I'll make the magnet collar and I think I'll be in position to try starting it again.

Chuck