25 HP Nash

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Sprocket

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Well, since I wasn't using the carburetor that was used originally, I couldn't really use the manifold either, so I made one from miniature pipe fittings and brass.
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Next was valves and valve cages which are pretty straightforward, but took a lot of time and fussing. The valves are two pieces, threaded 5-40
on one end and a stainless head silver brazed to the other end. I made a little fixture to hold the head about the right distance from the end for brazing
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I made the valve cages outsides, then set up to do the insides, valve seats and valve tapers in the same setup. (I had made a couple of extra valves to practice on).
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The last picture is the whole valve train, the lifter that attaches to the rocker arm, the valve adjuster, spring keeper, cage and valve.
The valve blocks need to be silver brazed to the water jackets before the cages are pressed in. I was going to try to use 1/16" silver braze wire on that joint, but the plans suggest .005" ribbon braze, which I found at Brownell's. It's an area 3/4" wide and more than 2" long, so I'm sure the ribbon braze will make it easier. I think that will be the next step, and also the last large braze.
Thanks for looking
Doug
 

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Sprocket

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Back to brazing. I had some parts ready, and decided it was time. Brazing the valve blocks to the water jackets had concerned me some.
Its a big area to heat under a fairly large chunk of steel. Took a lot of heat, but wasn't as bad as I thought it would be. The .005"x.5" ribbon braze worked great. If you have need of a large area braze, I'd definitely recommend it.
I had made a fixture to hold theses parts together, and another to locate the connecting rod parts.
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The water jacket/valve block fixture holds the square base plate, and a clamp on top of the valve block. I squared the valve block to the base with flux and ribbon braze in between and heated .
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The joint filled just about right. The next step was to finish the top surface on an expanding mandrel in the lathe.


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Now they are ready to drill head mounting holes and valve cage holes.
Time for lunch!
Thanks for looking
Doug
 

Sprocket

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The cylinder with the valve block attached is an awkward piece to hold. There are 14 head mount holes, one coolant passage and two valve cage holes to drill in each, and I didn't want it moving. The base piece was clamped in the mill vise, then the valve block placed against an angle plate and clamped that way. May have been overkill, but nothing moved.
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I drilled and reamed the heads for the spark plug bushings, then pressed the bushings in. You can see the coolant space in the head if you look in the bushing hole.
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I found that a piece of solder draped around the bosses was just about the right amount to fill the space. I had used less on the first head I did, then had to add, and that was hard to control.

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A little more sanding, and the heads will be done. When I blow air into the water jacket it comes out the head, which is as it's supposed to be. I need to press the valve cages into the valve blocks and the cylinder parts will be done. I lapped and honed the cylinder liners, so I think the next step will be pistons and rings.
Thanks for looking!
Doug
 

Sprocket

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Pistons and rings.
Pistons seem fairly straightforward, .002 smaller than the bore, ring grooves, and a pocket for the wrist pin. But that pocket wasn't so easy.
It's drawn as a rectangle, about .440" deep at the bottom of a .5" deep bore. The corners of the rectangle are rounded looks to be .063 radius.
But an 1/8" end mill doesn't really have the reach to do that, and you can't see down in the bore while you are milling. I figured how far I could move from center, X and Y, for the outside of the 1/8" end mill to cut the correct dimension. It felt awkward, and not being able to see what was going on was hard, but it worked out. I had to extend the end mill in the end mill holder to reach bottom. I don't have anything longer.
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I'm pretty sure it was Rustkollector who said he put an oil ring on these pistons, and that seemed like a good idea, so I re-spaced the grooves,
to accommodate a third, wider ring. The compression rings are nominally .045" so I ground the back end of a parting tool to .045" and made
compression ring grooves. The oil rings are .063 wide with a tapered groove .010" deep and .035" wide at the bottom. A 1/16" parting tool worked for those grooves.
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The needle in the second picture is about .035". Form tool for oil ring grooves.

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I had a mandrel from a previous build that was bigger than this one, so I could modify it to work here. The rings were brought to just over
width on the mandrel, and holes drilled in the oil rings. I used a #70 drill (.028"), and made 6 equally spaced holes. (Trimble says he broke off a #75 drill so only 1/8" stuck out of the chuck and made 8 holes) I didn't have to break off the drill, it went far enough in to the chuck. I used a sensitive feed drill chuck so I could feed it with finger pressure. Got through 30 holes without breaking the drill.
IMG_2134.JPG (I only need two oil rings and 4 compression rings, but I made some spares)
Out of space for now.
Thanks for looking.

Doug
 

Sprocket

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Just a little follow up.
The head bolt bosses needed to have their solder fillets blended into the head better. A little abrasive cord worked really well for that.
Somehow I had never had need of abrasive cord, but I really liked the way it worked for this, and was impressed how well the abrasive stayed
on the cord . This was .080" 150 grit .Made by Mitchell abrasives, got it on Amazon.

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The head bolts are 4-40 x 1". The one on the top came from American Model Engineering/Godschall's Custom Machining.
The one on the bottom came from Mcmaster-Carr. The taller, and 1/64" smaller hex heads seem to fit the bosses better.
At least, I like the look better.
Next, I plan to finish the ring spreading fixture , split the rings and get them heat treated.
Thanks for looking.
Doug
 

Sprocket

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Rings were finished by splitting with the tool Trimble described. It worked much better on the compression rings than it did on oil rings.
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The fixture is also as per the article. I wrapped a piece of brown paper around the whole fixture, then seeing as how I was only planning to heat them to 975 degrees, I sealed it all in aluminum foil. I don't know if it really helped, but the paper charred enough that I think all the oxygen was used up, and the paper wasn't all ash. I sent them over to Rick's Overnight Heat Treating, and he baked them at 975 for two hours. (Thanks, Mayhugh 1).
When I got them back, the aluminum foil seemed to be intact, and Rick had kept track of the heat and times. (Thanks, Rick!)

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The ring gaps stayed as they were when I took the pin out, and the fixture should be good to use again.
I don't know if the aluminum foil really helped, but it seemed like it should limit oxygen while it was heating.
I am unlikely to buy stainless foil, but at this heat, aluminum seems to work.
Any thoughts on the subject are welcome.
I've been working on flywheels and flywheel clamps, but that will be for the next post.
Thanks for looking,

Doug
 

Sprocket

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The flywheel castings are an interesting part to hold. I am using two different sized flywheels to accommodate a generator, some day.
The larger flywheel is 7 3/4" diameter with 6 spokes. I held it in the 4-jaw chuck and centered it then drilled and reamed the center holeIMG_2145.JPG
The flywheel clamps are to be press fit into the center hole, but somehow the .0005 over was not tight in the bore. I would have thought a reamed hole would be accurate enough, but it wasn't. I was actually kind of happy to make the clamps over, as the first pair, made from a rectangle of 1018 had some wicked hard places in it. They showed up as rings in the turned part and tough to slice areas in the saw cut.
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After I broke a slitting saw, I decided to go with an easier material. I have 12L14 rounds big enough to yield that end rectangle, and that's what I used. I found it much easier to make a square from a round than a round from a square. No interrupted cuts.
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I pressed the clamps in with red loc-tite for a lubricant. The new clamps were .6265" instead of .6255" for the oversized hole, they were fairly hard to press in so I think they should stay. I turned the flywheel on a mandrel between centers (or center and a collet) so it runs true to the shaft. The slowest speed on my lathe is 50 RPM which is faster than the chart says this should turn, but it cut reasonably well. I used a boring bar upside down with the spindle running backwards to cut the outside of the wheel. The second wheel is much the same, but easier because it is smaller.(5 1/2")

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It will take about 2 1/2" of lift to clear the larger flywheel, or allow it to overhang an edge. Haven't got that figured out yet.
I've been making parts and mandrels to hold gear blanks, and that will be the next pieces.

Ski season is starting! I get to go work at the mountain a couple of days a week. Might slow my already slow progress here, but it's something I've done since I was in college and i don't know how to stop.
Any way,
Thanks for looking!

Doug
 

minh-thanh

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Sprocket !
You weld and finish the surface is really nice
Soldering is part of a homemade engine, but I'm pretty bad at soldering silver
 

Sprocket

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Minh Than;
Thanks. That's a neat little diesel you made,
Silver brazing is a really useful skill. It does take "Learn, Practice and Patience" as you know, I would add to that "plenty of heat". I don't know what you have used in the past, but I've tried some that was really hard to make work. I also think you have to distinguish between silver solder, and silver braze.
Silver braze is a higher temperature but should be much stronger. There are also different alloys of silver braze. My favorite has been Safety Silv 56. It is the lowest melting temperature of their brazes and flows very nicely. It is 56% silver. (1205 F.) Even the 45% silver is a noticeably higher melting point. (1370 F.) I know some people will silver braze with propane, but I don't have the patience for that. Oxy-acetylene, or maybe acetylene -air, but propane has never worked for me except very light or small pieces.
It's definitely worth figuring out how to do as it opens up a lot of fabrication possibilities.
Thanks for looking!
Doug
(I have no idea what is available outside the US, but I'd assume something similar is.)
Safety-Silv® 56 | The Harris Products Group
 

Sprocket

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John,
I really don't know much about silver "solder" I only use the braze. I really like the Safety-Silv 56 and the white flux that goes with it. That is their highest silver content, lowest melting point. Their Tech sheet says "solidus 1145 F. liquidus 1205 F." I don't see a tensile strength.
Hope that helps.
Doug
 

Sprocket

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I had made a couple of gears for a Phil Duclos "Whatzit" engine. They were made with a single point fly cutter described in that article and while they worked, they were difficult cutting (thump! thump! thump!) and a little crude.
So, I decided to try to make these better. I had seen hob type cutters and directions for making them. Helicron has a good explanation for making this cutter and that's what I used. (Making a gear cutting hob) I first tried this with mild steel and case hardened it to see if it was a reasonable thing to make. That one worked on brass OK, never tried it on steel. This one I made from O-1 and hardened and tempered it.
You start by making rings, spaced for your DP. mine was 32 DP, rings .098" apart, .106" deep
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I used a hex collet block and made six teeth. I relieved the backs of the teeth with a stone and cleaned up the fronts, then hardened the hob part. I had the piece turning in the drill press as slow as it would go, then lowered it into the oil (ATF) while it was still turning. It seemed to heat evenly and stayed straight in cooling.
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With management approval, I tempered the hob for one hour at 428F. in the kitchen oven. The color doesn't show really well, but it came out a nice dark straw color.
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Now I have to try it!
Thanks for looking,
Doug
 

Sprocket

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I had a couple of gear blanks and mandrels ready. The smaller gear is 40 teeth and has a 7/16" hole with a little woodruff key. (#202 - it's tiny)
The cutter only makes a full depth cut on the center ring, and as you rotate the blank, it cuts facets to shape the teeth. There are sleeves on the mandrel to stiffen and deaden it, so it looks bigger than 7/16"- it's really 3/4"
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The smaller gear came out pretty well, and I probably will use it. Have to see if center distances work.
The larger gear has 80 teeth, and only a 3/16" hole. That mandrel also has the stiffeners, but I'm not sure they are enough. I cut an 80-tooth gear, but I think I can make a better one. I am going to try to anyway.
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I had to touch up the cutter a couple of times, but it was 120 cuts to get around both gears. At least I think I have the process down, now I just have to touch up my execution.
Again, Thanks for looking!
Doug
 

Sprocket

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Sometimes you just have to do it a couple of times to make it work right. My first attempt at cutting these gears was OK, for a first try.
They weren't useable, but I had some idea of what to do differently. The smaller gear just needed to have the teeth cut deeper, but I decided to start over. I made the gear blanks from cast iron this time. Much easier cutting than the mild steel I used the first time. I also made a little hub in the center, so the gear was as wide as the Woodruff key. Cutting was much the same, but slower speed for the cast iron, it seemed to not dull the cutter as fast. I also found there was a little play in the dividing head which could be adjusted out.
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The larger gear was also cast iron, but I silver brazed the hub into the center, and left it long to act as a mandrel as I cut the teeth. I wanted as much stiffness as I could get, and this also made sure the gear and hub were concentric. I couldn't drill the center hole until later.


















This also made it so I couldn't try the gears on the engine until I parted off the hub and drilled it for the cam shaft. After parting off, I tried the two gears together on the cam and crank, and while they went together it was a little tight. I tried running them on a mockup with some Clover compound, and that made it run more smoothly, but still too close. I had already taken the dividing head off the mill table and put the vise back on, but decided I really had to cut the teeth deeper. It was much easier to set the dividing head up the second time, and not nearly as much of a problem to re-align the teeth as I had thought it would be, so I cut the teeth on the smaller gear about .005" deeper. This made the fit quite a lot better, so I did the same with the larger gear. I had a mandrel from my first attempt that fit the 3/16" center hole and the cuts were very light. The fit was much better after trimming both gears.

















Somewhere in there I had drilled the six holes in the larger gear, which makes it look more finished. I'm happy with this pair and I think they will work well. It's becoming less of a mystery, at least for spur gears. The others will have to wait.
Thanks for looking!
Doug
 

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