Meriam Abbott Build

[Sprocket]

Plans for the 1902 Meriam Abbot engine by Doug Kelley were published in the Nov/Dec 2022 and Jan/Feb 2023 issues of "Home Shop Machinist"
I had built the Two Cylinder Nash, also by Doug Kelley and had liked his designs.
This engine uses very similar construction methods, although there are things I would have done differently, so I did.
The original was made mostly of brass, which I would have had to acquire, but I had steel in the right sizes for most parts, so it is mainly made of steel. My crankcase is silver brazed, but first bolted together with 2-56 socket head cap screws. The crankcase sides and bottom are 3/16" plate, the sides are spec'd as .030", but I made them .060" for a little more stiffness. I tried the silver solder recommended in the article (Harris 4% silver) and found I'd rather use the high temperature braze (Harris 56% silver). I did use the silver solder for some small parts, or where different temperatures were needed for a second part to be added.

I used the rotary table to cut out the crankcase sides. Two roughly sized blanks were riveted together, and the crankshaft center marked. The rotary table was set up so one slot was parallel to the x axis with rotation at 0 degrees.

I had made a plate and smaller finger clamps along the way which have helped a lot in small work holding. The plate was added to the rotary table with the table centered under the quill, then the two blanks added with the crankshaft center at the table's center. This way, I could cut the sides parallel, top and bottom parallel, cut the curves where the sides angle toward the top in one set up. The crankshaft center was the 0,0 point, and all the other dimensions came from there.

I also made the larger bearing flange from steel, and in one piece instead of gluing the webs to the flange. A blank was turned with the cone to make the ribs from. This was screwed to a plate using the mounting holes, then the center of the flange was centered on the rotary table.

Cuts for this part were relative to the center also, and two of the mount holes were parallel to the x axis. Start points were: y axis away half the rib thickness plus half the cutter diameter, x axis left half the center hub diameter plus half the cutter diameter, then make the cut moving further left and down to the height of the edge. Rotate 60 degrees and repeat x6. I actually started bigger, and finished at these dimensions, but that is how I planned the cuts.

Next, Y axis toward me one half the rib thickness plus one half the cutter diameter and repeat all the above steps. I used a ball end mill for the cuts close to the ribs and hub, so it looked like a fillet, and flattened the areas between with a regular end mill. It looks rougher in the pictures than it actually was, because bead blasting made it quite smooth.

I need to fix some more pictures.

Thanks for looking

Doug

 

[Sprocket]

The engine's base was also .190 steel. it has a recess bored in the bottom for the assembly hatch.

The crankcase ends are spec'd to be .030", but I felt that .060" would be a little firmer. It worked well, although I did have to heat it to form it to the curve of the crankcase sides.

The ends were left a little long, and after bending and screwing them to the sides, I trimmed off the tops so the crankcase top would fit on,

The bottom of the crankcase end was made with a large (1/2") ball end mill. Because the rest of the end is .060", I left the top of the fillet piece .060" also. I have to go find some better pictures.

Thanks for looking,

Doug

 

[Sprocket]

This is the picture I was looking for

I cut the curve on both sides of a piece of steel with one edge to the needed thickness, cut it in two and finished the other edge to dimension. It fit under the crankcase end.

There are added rounds on both sides to make mounts for the bearing flanges. These were soldered to the crankcase sides. The plans show them as rings instead of solid circles, but this made sense for me

There is a doubler and crankcase access door on the end of the crankcase.

There is a 5/16 SHCS holding the bearing flange mounts on. I soldered these on rather than epoxy them and made a curve on the edge instead of an epoxy fillet. After it was all brazed or soldered, I bored the holes for the bearing flanges.

Having all the pieces screwed together makes a very solid assembly to braze. when you grind off the screw heads the holes barely show.

Thanks for looking,

Doug

 

[raveney]

Hi Doug,
That looks terrific. Thank you for sharing how you held the cove pieces. I was wondering how you were able to thin the other sides. The bearing mounts appear to be worth the effort in the last after brazed photo.

 

[Sprocket]

Raveney,
It's always nice when an easy solution works. As you've probably figured, the round was sitting on a parallel.
Doug

 

[Sprocket]

The crankshaft is another fabricated part. Somewhere I read that people had had trouble fitting the crankshaft through the bored hole in the crankcase. My solution was to make the crank pin smaller, and the overall diameter .060" smaller. that still left the same thickness over the end of the crank pin. A .3125" crank pin also left room to add a split bronze bushing in the big end of the connecting rod.

I made the two crank webs from one piece of steel and split it when all the holes are drilled, and shaping done. I am fairly certain they match that way.


The little spacer kept everything in the correct position. I made a little rotisserie that my wife turned slowly while I brazed. Heating was even and the crank came out pretty straight. I put the factory surface of the steel toward the inside, because it's hard to do any finishing in there later. the outsides are easier.



Thanks for looking!

Doug

 

[Sprocket]

The flywheel hubs look like a fairly straightforward part, but they seem to take a lot of steps.
While you could start rectangular and turn the round part down, I started with a round.
It was convenient to hold the smaller end in a square collet block for the rest of the steps:
Mill the flats, drill the holes, slit the clamp.
Preferably you slit the clamp in the correct direction.



This called for #4-40 Hex head bolts. I didn't have any with scale heads of the right length
so, I made the four. I've also found that when I get the scale heads, #4 heads are 11/64" a size I don't have a wrench for. So these are 3/16" heads with a short thread. (I did get an 11/64" socket from Godshall's, but you really need two)

They needed a bit of cleaning up.


Screw holder and nut holder.


And finished parts. Next, flywheels.
Thanks for looking,

Doug

 

[Sprocket]

The flywheels came from Martin Model and Pattern. 5-1/2" 6 spoke "Macbeth". Everything I have gotten from Martin has been really nice, and these were no exception.
I held them in the four-jaw chuck and centered the hub, then rough machined the outer surface as far as possible and the edge of the rim.

reversed it in the chuck, and did the same to the other side. I also cleaned up the area
between the spokes and the rim and the fillet that connects them.
The hubs were pressed in with red Loctite for a lubricant, then they were mounted on a mandrel for final machining and grinding

The edges of the rims were also done with the tool post grinder.
I usually take way too many pictures, but there weren't many of this part.
Thanks for looking

Doug

 

[Sprocket]

The cam followers are brass levers with a roller at one end and the pivot at the other.
The pushrod connector is steel, soldered or brazed to the cam follower. I wasn't sure I could hold the .063"x .19"x .22" piece accurately while I attached it, so I went a different way.

I shaped the steel domes and left them .063" long, made a recess for the piece to sit in, also .063" deep, then silver brazed the pieces together. milling off the excess left a tab that looks like the drawing.
There are a couple of holes, one drilled and tapped for a spring mount, the other for the roller axle.

The pivot is soft soldered to the follower. I made a simple fixture to hold the parts correctly for soldering

There is a right and left shape for the followers.

The cam followers mount on the valve gear base




Cams mount on the back side of this gear hub and the large gear on the front.


This all bolts to the side of the crankcase

Thanks for looking,

Doug

 

[Sprocket]

The gears are specified as modified Boston Gear parts, but I thought I would make them.
The larger gear mounts on the gear hub, and I held the whole thing on a mandrel to cut the teeth.

The smaller gear was also mounted on a mandrel. I was figuring out how to hold it in this picture before mounting it on the mill.

Both gears were of cast iron. I had made a cutting tool for 32 DP 20 PA which I used to cut these

(This video was a practice piece.)
They might not work with a commercial gear, but they work well together.
Thanks for looking,

Doug

 

[Sprocket]

The connecting rod is a pretty usual connecting rod. I had made the con rod journal on the crank 5/16" instead of 3/8", so the big end of the con rod needed to be different. Probably using 7075 aluminum for the bearing surface is fine, but I had made room, so I used a
split bronze bushing.

The bronze is split exactly in half and soft soldered back together


It is strong enough for gentle machining

You can see the soft solder on the edges of the bearing. It sands off.


It needs a little bit more finish work, but that's the connecting rod.

Thanks for looking,

Doug

 

[kuhncw]

Doug,

That is an interesting lathe dog. Is that your larger gear blank that is gripped by the dog?

Nice work on the cam follower levers also.

Nice work. Thanks for posting all this detail.

Regards,
Chuck

 

[Sprocket]

Hi Chuck;
The dividing head came with an "H" shaped piece that fits over the center (it has the hex heads sticking up). It doesn't provide any way to actually turn the mandrel, so I made that lathe dog thing. I don't think I'd like it spinning around on the lathe, but it works for the dividing head. I put different adapters in it to accommodate different mandrel sizes. The adapters have a set screw to hold the mandrel, and the adapter is set screwed in the dog. It lets me work between centers. I tried a chuck on the dividing head, but it wasn't a very accurate way to hold the mandrel. I don't have a 4-jaw chuck that fits, the three-jaw was not good.
And, no, that isn't the large gear blank, just an adapter.

Thanks for asking,

Doug

 

[Sprocket]

I puzzled over these cams. It is not so much a lobe as a part of the diameter that is left bigger.
The plans say to make the blank diameter .730" and use a 3/8" endmill to mill away all but 70 degrees for the intake and 100 degrees for the exhaust. The portion that is milled off ends up .640" or a cut depth of .045. I tried to figure how much width of the cutter is there at. .045 " depth of cut, then how many degrees that equaled.... it was close, but my circle ended up with 372 degrees. (rounding error probably). I'm sure someone knows the real way, but what finally worked was to figure the chord length at the tips of the cut and measure with a caliper.
With the rotary table centered, I used a plug in the quill the same size as the center hole to center the blank on the table.
The blank is held in a collet block so there is something to clamp.


There is enough blank length to do both cams, first the whole length to the exhaust cam size, then the top to the smaller
intake size.

There are two set screws 40 degrees apart. I set the little table at 20 degrees, drilled and tapped, turned it around so it was 20
degrees the other direction and drilled and tapped again. I think if I were to do this again, I would use at least a #3-48 set screw instead of the #2-56. It's hard to get enough torque on those little wrenches, and I have had cams slip.


After parting off and facing to thickness, we have cams. The roller on the cam followers makes the lift a little less abrupt than it looks, I think and there is a return spring to hold contact.


After thinking about this again, I went back to refigure the degrees the cutter took up. This time I got 19 degrees from the center of the cutter to the edge of the cut. If it helps, my cuts were 222 degrees for the exhaust cam (222+19+19+100 =360) and 252 degrees for the intake. Similar addition. The chord lengths measured .419" for the intake and .559" for exhaust.
I hope this is of help to someone. If there was a better way to figure it, I'd like to know.
Thanks for looking.

Doug

 

[Sprocket]

The rocker arms are made from a number of little pieces. I made a lot of them on the rotary table.

The hole at the point of the base is the center of the the rotary table. By figuring the angle and offset for the cutter, I could cut out the whole base. The part is screwed to a sacrificial plate clamped to the rotary table. I also made a groove for the upright to make it easier to position and solder.

To round the ends of the base, I switched the corner to the center hole.



The upright was made in a similar way, the pivot hole is the rotary table center, the upright was made .063" longer to account for the groove in the base.


The rocker arms themselves were also made on the rotary table; the pivot point was the rotary table center. This time, there were two layers.


The rest of the parts are just rounds. I used a brass pin to align the pivot parts while I soldered them together, then redrilled the holes. There is a steel disc that contacts the end of the valve.

I have liked using the rotary table for these little parts. It takes some figuring to get the angles, but it's an easy way to hold the part
and assure accuracy.

Thanks for looking,

Doug