Chris's Holly Pumping Engine Build

[crueby]

Back on the valves again today, started by turning the valve tubes out of lengths of bearing bronze. To give room to grip them, I turned them in pairs with the flanges towards the center, then cut them apart and faced the flanges to thickness.

Then each valve tube was chucked back up in the lathe, drilled, reamed, then lapped with some very fine grade Timesavers in oil. Messy job, but it gave a good fit on the valve rod material. Here are two of them slipped into place in the lower HP valve block:

Next up will be to drill the screw holes in the end flanges, mill the openings int he sides of the tubes, and then can start in on the valve rods themselves....

[cnr6400]

 

"totally tubular, man" as some folks said in the 1980's 

[crueby]

"totally tubular, man" as some folks said in the 1980's 

Surfs up dude...

[cnr6400]

  get ready to hang ten (thou)

[crueby]

The other day Dan Rowe tipped me to the roll form taps for the smaller sizes in brass and bronze, it sounded interesting so I ordered some, in 0-80 and 1-72. The 1-72 one arrived today, just gave it a try. Looked up the drill size online, nearest I have is a #51, just an elves-whisker larger than the 1.7mm the chart said. Drilled some holes in a bit of 3/8" thick brass, some in the middle, some near the edge, and one just partway through.

My reaction, quite impressed! The full thickness of the tap, with no flutes, makes it a lot stronger, and it goes in with same or less effort than a normal cutting tap. Since it does not clog up with chips, since there are none, it goes in the full depth the same, no backing out to clear chips. Not sure if I should use any oil with it, did not seem to need it on the brass at least. The only difference I can spot in the holes from a cutting tap is that it raises just a little more of a bur at the entry point:



A drill or cutting tap does some of that, this does it taller, but a swipe with a flat file takes it right off again. Given the number of small holes I need to tap in the cylinders, this will be quite handy! The other size is supposed to be here tomorrow. The cutting style taps will still get used on steel, but for the brass and bronze this should be great. I assume it works on aluminum too, probably better to use oil on that with its tendancy to be sticky?

Dan, thanks!!!
 

[Dan Rowe]

Chris, I use a tapping grease for these as it sticks to the tap better than the runny stuff. I use them in mild steel also as I make square nuts from key stock.

#51 gives 64 percent thread and 1.7 is 65 percent thread. I usually try for the closest drill I have to 65 percent thread.

Cheers Dan

[crueby]

Chris, I use a tapping grease for these as it sticks to the tap better than the runny stuff. I use them in mild steel also as I make square nuts from key stock.

#51 gives 64 percent thread and 1.7 is 65 percent thread. I usually try for the closest drill I have to 65 percent thread.

Cheers Dan

Thanks!

[Kim]

Cool! Glad you like the form taps.   I've found them great to use also.  Though right now I'm using mostly spiral point taps (gun taps) since almost everything I'm doing is in steel.  Still, I like the form taps!

Kim

[crueby]

Today the 1-72 form tap got its first real use. Started in on the back covers for the valve tubes, turned a length of round bar to diameter with a step on the end to locate it in the end of the tube. Then over to the rotary table to drill the 1-72 clearance holes around the rim:

Parted off, and repeat three more times....
Then with the same position on the mill, chucked up the first of the valve tubes, back end out, and drilled matching tap-sized holes for the screws:

Quick run in/out of the form tap, and ready for screws:

Three more valve tubes to go, then will start on the front side bonnets for the valve rods...

[mklotz]

There's a program (DRILL) on my webpage to calculate tapdrill sizes for form taps.  Just to ensure that it got the same results as you guys did, I ran this case through it and it came up with 1.7 mm as the closest available drill for 65% depth of thread and #51 as the next smaller dot, 64%.

For the benefit of readers who may want to try form taps and don't have access to a means of computing tapdrill size, the formula is:

dtd = td - 0.0068 * dot / p

where:

dtd = diameter of tap drill
td = nominal diameter of tap (0.073 for #1)
dot = depth of thread expressed as percentage (65 for this case)
p = thread pitch expressed as threads/inch (72 for this case)

Now, if you plug all those numbers into the formula, you get:

dtd = 0.06686 inches

which, when multiplied by 25.4 yields 1.698 mm implying a 1.7 mm drill.

[crueby]

There's a program (DRILL) on my webpage to calculate tapdrill sizes for form taps.  Just to ensure that it got the same results as you guys did, I ran this case through it and it came up with 1.7 mm as the closest available drill for 65% depth of thread and #51 as the next smaller dot, 64%.

For the benefit of readers who may want to try form taps and don't have access to a means of computing tapdrill size, the formula is:

dtd = td - 0.0068 * dot / p

where:

dtd = diameter of tap drill
td = nominal diameter of tap (0.073 for #1)
dot = depth of thread expressed as percentage (65 for this case)
p = thread pitch expressed as threads/inch (72 for this case)

Now, if you plug all those numbers into the formula, you get:

dtd = 0.06686 inches

which, when multiplied by 25.4 yields 1.698 mm implying a 1.7 mm drill.

Excellent Marv - thanks!!

Now I need a program to re-educate my brain, its been so many years of knowing which drill size to grab for the common tap sizes that I am likely to just grab the cutting-tap size out of habit!   

[steamboatmodel]

Hi Chris,
I had a case at one time for storeing the taps and drills, It held the drill sized for cutting, the three taps and the clearance drill all in a line. The one I had was made of plastic and eventually fell apart, I keep saying I am going to make another in wood or metal.
Gerald.

[crueby]

Hi Chris,
I had a case at one time for storeing the taps and drills, It held the drill sized for cutting, the three taps and the clearance drill all in a line. The one I had was made of plastic and eventually fell apart, I keep saying I am going to make another in wood or metal.
Gerald.

Hi Gerald,
I have mine in one of those plastic compartment boxes from the fishing tackle aisle of the sporting goods store. Keeps all the taps/dies well sorted, but then I go and buy more sizes, and need a bigger box with more compartments...  That won't fit in the same drawer...   

[crueby]

This morning I got an email from the guy over in Buffalo that I got the Holly plans from - he came across this picture that he took years ago at the Buffalo Color Corp factory - they used to make aniline dyes and such. He was wondering what it was, if it is a steam engine?

Looks to me like it may be a Corliss valve engine out the lower left side, looks like it may be the four back valve covers around the corners of the rectangle cover facing the camera, flywheel on the right, then some sort of pump or compressor or grinder or something up vertically to the top?? Anyone here know what this machine is?

And to continue the side-track-morning, I've been noodling around with ways to make small globe valves for the models. I've searched through this and other forums, found the versions that George and others have done, lots of variation on the theme, all do-able, most with a silver soldered core down the center that has the cross passages cut into before soldering. Then, I came across the drawing in the Holly plans for the full sized one on that engine, which is a little different (same general theme but different construction) :

Having the bottom cover for the valve stem large end to go through means that the opening through the top can be smaller. That got me playing in Fusion again, and I came up with a valve that looks like this on the outside:

with a cutaway view like this:

Rather that a full-depth center core soldered in, all it needs is a short washer shape soldered to the bottom to form the bottom flange, the rest of the valve body can be turned on the lathe. The top valve stem post just screws in. I designed it with a 5/8" diameter body, .300" diameter pipe internal bore, 2-56 valve stem thread, M4 threads on the top post, and 1-72 screws in the pipe flanges and bottom cover. The two side passages in the core could be cut in through the side openings. The threads on the valve stem could be cut, then the bottom tapered valve end screwed/loctited on. To assemble, run the stem up from the bottom, thread the top post down over it, screw on the packing nut with a little packing rope, then screw on the handwheel. It would give the same action as the original throttle valve withe the same outside look, but need no castings or through-soldering.

Looks to me like it should work and be make-able - have I missed anything? I'll give it a try soon and if it works will post the plan sheets for everyone. Will still take some careful boring of passages.

[cnr6400]

Hi Chris, re the prototype 90 degree engine , it looks like some compressor engines I have seen. Frick made some this format for large ammonia refrigeration systems, but I have seen air compressors for mines and large railway shops in the same format.

For your globe valve, the attached sketch markup shows a few ideas - just food for thought. Don't work on these valves too hard - wouldn't want you to get valveosis.