25 HP Nash

[Weldsol]

Superb work you have done, keep it up

Paul

 

[Sprocket]

Chuck and Paul, thanks for your comments,
I have been using oxy-acetylene for brazing. In the past, I have tried propane and have had little success except for very small parts. It may be that
propane will work, but I'm not sure I have the patience to wait that long. I also like being able to tune the flame which you can't do with propane.
When I first started brazing, I read that the flame should be a "long, soft carburizing flame" and that is what I've been using. That was a while ago, and I don't remember where it came from, but it works. I use the largest tip I have (#5) . I've been using Safety-Silv 56 and it works nicely. I have some 45, and the melting temp is just enough higher to make it difficult. some of these parts have a fair amount of mass, and take a while to heat up. I haven't done the valve body to the water jacket yet, but the valve body is 3/4"thick and 1 1/2" wide or so and will require some heat. Instructions say to use ribbon braze .005" x 1/2". haven't got that, so I guess I'll use the 1/16" wire.
Later.
Doug

 

[burn0170]

Doug - When I brazed the water jackets for the Snow, I had issues with small pin holes, I found that Green (wicking) Loctite worked well. I just smothered that on after it cooled and cleaned up. Filled the pin holes and sealed up well. Hopefully you're a better brazer than I am, but if you have any small holes, this trick helps.
Jim

 

[Sprocket]

Jim,
Thanks for the heads up. I hope it won't be necessary as these cylinders are pressed, (he says shrunk) into the water jackets. I may see if I can wick some Loctite in from the ends as a backup. Haven't ever used the green, but this seems like a good place to try it.
Thanks,
Doug

 

[Sprocket]

Another little detour.
I decided that rather than make the coolant manifolds from soldered brass pieces, I'd make them from miniature plumbing parts.
I got "T's" 90's and 45's from PM Research in 1/4", and tubing to match. the castings come either un-machined on trees, or for a lot more money, machined. I bought the casting trees.
They are pretty small to hold and machine, so I made a little vise to hold them.


you have to do the first side while the part is still on the tree so it can screw on to the rod to
slide into the vise. It works for 90's and "T"s, haven't tried 45's yet, but I think it will just clamp at 45 degrees in the mill vise.



Inlet on the water jackets, outlet on the heads. The attachment plates get soft soldered to the manifolds, then bolted to the mount plates,
with a thin gasket. There will be more piping to do, but it will be connections, not pieces like this.
The parts are tapped and threaded 1/4-40 Model taper pipe thread, taps and dies also from PMR.
More a little later,
Thanks for looking,
Doug

 

[Sprocket]

Back again.
Before I could bore the crank shaft bearing holes, I had to join top and bottom pieces and even off the surfaces.


just a bunch of drilling and tapping to get to this.


There is a symbol for surface finishing on the ends that looks like a square root symbol with a second line next to the left side.
So I surfaced the ends. (Couldn't find a reference for the exact meaning of that symbol if anyone knows?).

Which should have made me ready to bore the ends. So now comes the "Oh, crap" moment.
Somehow in setting up to braze, I flipped the top piece, so the holes were exactly 1.00" from the wrong edge. Maybe a good reason not to have bored them earlier, but it seemed like a good idea at the time.
Moving holes is not an easy thing to do, but it seemed easier than trying to un-braze the top.
So I made half circles, and hole plugs, brazed them in place, and re-bored the holes in the top



And now I'm back where I was a couple of days ago, but at least the holes are in the right spot.
Out of room for now,
Thanks for looking,
Doug

 

[kuhncw]

Doug,

That was a nice bit of salvage machine work.

Chuck

 

[Sprocket]

So, I got back to the point of boring the crankshaft bearing holes. I'd been thinking about it way too much, got to go ahead and start.
The holes are about 1- 3/16" in diameter and go through the ends and the middle plate. I suppose if I had a very long boring bar, I could do it all from one end, but I don't. It also seems you would magnify any error by going all the way through. So my plan was to bore one end, and through the center plate, then flip it over and do the same from the other end. You also have to place the cam arms on the top of the crankcase and drill for the cam shaft. It's marked as a critical distance for gear mesh from the crankshaft center, so it seemed a good time to do add those also.
I got the crankcase mounted on the not quite big enough angle plate, vertical in two planes, and square to the table travel.


It took a shim between the angle plate and the top of the base to get it vertical.
Then I found the center of the crankshaft, and measured to where the camshaft should be, and soft soldered the first arm in place.

Added the brass plug for the camshaft bearing and drilled the cam shaft hole, then went back to the crankshaft center, drilled the mount holes for the bearing retainer, then drilled and bored the crankshaft center hole.


So the bearing retainer fit in.


Repeat for the opposite end, and it looks like a crank case. The tips on the arms are soft soldered, they are the pivot for the rocker arms.


I think I must have worried about this just enough, because it came out ok.
Thanks for looking,

Doug

 

[Sprocket]

Crankshaft.
This part was difficult. It would seem that the way it's made would keep it straight because everything is symmetrical. It didn't work out that way.
The first one was just as the plans. It was hard to keep parts positioned for brazing, and ended up with too much bend when it was finished. I tried to straighten it, but couldn't make it better.
So i did things differently the second time.

Made the crank throws in pairs, as I did the first time, then split them. Turned the shoulders on the outside throws, then rounded the outer ends. I centered the rotary table, clamped a piece of aluminum to it, drilled a hole at the center, and another one crank throw (.656") away on the X axis, then tapped the two holes. Made bushings to fit the two holes, and clamped the parts down. I Moved X axis to clear, and then rounded down to the end of the part for a radius of 9/16".


The other end, or center is 5/8" so I blended the sides

I also made the crankshaft 1/2" instead of 7/16", so I could turn it down to take out any bend. To keep things spaced, I made little half
circle spacers for the throws and center section. After cleaning and assembling all the pieces with flux, I wired all the parts together.


Brazed the center section, then cut the wires, knocked the spacers off and brazed the ends, let it cool down mostly, then scrubbed it.
Out of room for now, more in a little while.
Thanks for looking,
Doug

 

[gbritnell]

It's sure coming along great! Even though silver solder is pricey I think I would have gone that way just for ease of construction.

 

[Sprocket]

To continue,
The crankshaft cleaned up nicely with soapy water and a wire brush.

Had to make sure I cut out the right parts, then rounded the inner ends of the throws, and milled out the center of the throw.

To maintain the distance in the throws, I'd made some little "T" nut pairs to clamp in the spaces.
then turned the ends to 7/16"



I'll need to make the center bearing 1/2" instead of 7/16", but I'd planned a little change in that anyway. I think this one is going to work.
That's all for now. I'm caught up with what's done.
Thanks for looking!

Doug

 

[Sprocket]

George,
I really like silver brazing. My first real silver brazing project was a mountain bike frame that I rode for several years, Fillet brazed, no lugs.
It has gotten more expensive since then, but I still like working with it.
Doug

 

[Vietti]

Looks good! I've made a few built up cranks, so far pretty straight. I find by cutting a deep chamfer aka counter sink, in the webs prior to soldering I get a stronger joint, I think, looks good any way. Don't put them on the insides of the rod journals cause you cannot cut out the excess solder. The ends of the rod throws are easily rounded in the lathe when the job is done before the crank sections are cut out. Also had pretty good luck straightening the crank in the lathe with a soft hammer. Never thought of making the crank oversize and turning straight, good one!

John

 

[Sprocket]

John,
On the first version I made of this crankshaft, I did round the ends on the lathe. I thought it might look better more rounded, and as long as I was doing it again...
first time second time
It just seemed it needed to be a smaller radius than I got turning it on the lathe. Purely visual.
Thanks for looking

Doug

 

[Sprocket]

There is a center bearing that goes in the hole bored in the center plate of the engine. The plans show a split bearing 3/16" thick
and 1.188 in diameter, screwed together with 2-56 SHCS. I decided that as long as I have the space to do it, I'd make the bearing surface longer.
My plan was to make the bearing about 1/2" long and make a saddle to sit over the center plate. Eventually, there will be a set screw from the
bottom (through the bottom center plate) to lock the bearing in place. Being wider, I could use 3-48 x 3/8" SHCS to join the two parts.

Counterbored, drilled and tapped, cut the center, and cut the top loose, then milled both halves to the same thickness and bolted them together.
Centered the part in the 4-jaw chuck, and cut the profile and drilled/reamed the center hole.
The other end was done partly on a mandrel, partly holding that 1/16" x 3/4" boss in a collet.

The side ridges locate the bearing on the center plate.

and the crankshaft in the bearing.

Still needs some cleaning up and polishing, but so does the crankshaft.
Thanks for looking.
Doug

 

[Sprocket]

Connecting rods.
These are a little different from what I've made in the past, mostly because they are built up and brazed, but also because the ends are cast iron.
As messy as it is, I like the way cast iron cuts. The big ends are pretty standard. I cut a piece off of a scrap of cast iron and milled it to thickness, and width with a little extra length, drilled and tapped the bolt holes to attach the caps, then cut off the cap ends and milled them to length.
Same with the other piece. I had marked the pairs for orientation, but by the time they were correct length, some of the marks were gone.
Bit of a puzzle, but I got them sorted out. The top ends have a 45 degree cut off on the corners, so after drilling and reaming the crank pin holes,
I cut the corners off.

The big ends are 3/4" square. The small ends are .44" diameter on the ends, and taper to .31" at their bottom end, and are .595" overall.
So this is what I did. Started with another cast iron rectangle of correct thickness and excess width, drilled and reamed the two wrist pin holes, 1.375 " apart for plenty of extra, then rounded the ends on the rotary table.

I used the part like a tiny sine bar to mill the taper on the part, then cut it in half, drilled the holes in the end.

It took a little fixture to hold the parts vertically so I could drill the end holes


"Oops, we ran into some problems" no more room.
Continued below

Thanks for looking
Doug

 

[Sprocket]

To continue,
I used a piece of brass rod to align the two parts, and the wrist pin holes to suspend them in the vise,

Milled half way through and to length, then flipped it over to finish


Next time I'm brazing, I'll make a little holder for length and alignment and braze these together. There was probably an easier way, but this is what I came up with. Probably could have done it all on the rotary table (little ends) but the angle was 9.7 degrees for .375 inches, and I wasn't seeing a way to make all four of them the same that way.

Thanks for looking,

Doug

 

[Sprocket]

Well, I spent a lot of time in the last two weeks working on the shop, not in the shop. but I have a lot more room now and made room for
a bead blast cabinet that had been in an un useable position, and a big air compressor to run it. Still need to find homes for a few things, but it's much better.
So, this weekend I worked in the shop. I had made the cam mounts and started trying to set up to cut the cams


The rotary table was centered, the blank clamped in the V block and that was centered then the V block was clamped to the rotary table
so I could release the blank to remove it to cut off the first cams, then raise it for the second set. That part worked fine. The problem is getting the cam lobe the width specified in the plans. I thought I had worked out how many degrees I had to rotate it before moving the X axis to make a flat, but that made a point, not the lobe I expected. I ended up just sneaking up on the dimension by rotating a few degrees at a time.




The cams were parted off a little long, drilled and tapped 2 places each, 2-56, then clamped on a mandrel to face to thickness.



In the picture above, the intake cams are on the left with a narrower lobe, one mounted on a cam mount, and as they will be on the camshaft.

Thanks for looking,

Doug

 

[Sprocket]

I took another bit of a detour from the larger parts I'd been working on. I was working on the valve blocks, thinking how to pipe the carburetor, but didn't have a carburetor. The S/S carburetors are no longer available, I understand. I had gotten a Traxxas carb, but it really doesn't look like it fits with this model. So I made one. There was a discussion on carburetors a while back, and out of it I got a couple of different plans. The one I used was George Britnell's from a 4 cyl OHV engine.
https://www.homemodelenginemachinist.com/attachments/4-cyl-ohv-sht-j-pdf.38086/
It seemed like the right kind of carb for this engine. I thought I would use MIL-TFP-41 (M) * and really tried to make it like it was drawn, but there were a couple of things I had to change.


The body is turned in the 4-jaw, on three of its four sides, the third picture is a gauge plug I made to see when the bottom of the cone reached .260". Couldn't think of a good way to measure that, my snap gauges don't go that small. I just snuck up on it until to gauge would just go through.



This is one place I deviated from the plans. The intake cone is tapered on the outside, also and .150" longer than original.



Throttle barrel, the fuel jet, and because I expect to power this with propane, a compression fitting for fuel.

The bug catcher screen wasn't on the original, but I thought it needed one. I had expected the 2-56 idle stop screw and 3-48 air bleed screw to be difficult to make, but they really weren't. And no, I didn't single point them. I did mostly on the 10-40 threads for the fuel jet, then finished them with a die.
I'm out of room. More in a little bit.
Thanks for looking,

Doug

*MIL-TFP-41 (M) = make it like the freaking plans for once (mostly)

 

[Sprocket]

There is a groove in the throttle barrel for the idle stop screw to ride in. It locates the barrel in the body, and should provide a stop for idle position. Eventually I figured out how to do this.


The through hole was set vertical, an .085 end mill lowered to about center, moved in in small increments to .088" deep then .003 wider to finish, and rotated to 16 degrees short of horizontal.

This ends up with a slot that ends in a flat bottom.

Because this is an engine that will run at a constant speed, with no need to VROOM,, VROOM, I thought it needed a throttle quadrant for
speed control. And a few more deviations from the plans.






I drilled and tapped the mounting holes in the sacrificial plate clamped to the rotary table, cut the arcs, the first to clear the throttle barrel, next to thin the piece and make room for bolt heads, then scored the detents with a spotting drill, and cut it loose with the third arc, and the mounting bolts held it in place.
It seemed too thick at the edge, so I flipped it over, angled the mill head, an thinned the back side. It was time to tram it again anyway. The last picture has all the parts but the needle valve. I think the handle that is on it now is a prototype, but it works for now.
Out of room again.

Thanks for looking!

Doug