Grasshopper engine build thread

Last weekend I made the piston, piston rod, steam cylinder, valve plate and steam cylinder top. My wife was busy with gigs...

First up is the piston. Because I oversized the bore, the piston was oversized. And because the cylinder part is tiny, I could use that as my gauge. So a bit of aluminum rod was turned to a "piston" fit. Then I put in some oil grooves, using a very cute little HSS groover. Not shown is parting off the piston with a bit of extra material and then swapping end to end and turning to the correct length. I did this all in a 3-jaw chuck, as the parallelism of the the top and bottom surfaces is not super critical.

Groovy piston.jpg
The piston turned to final diameter and grooved. You can just see
my grooving tool in the bottom of the photo.​

I then made the piston rod by thread some 3/32" brass rod of appropriate length.

Piston rod.jpg
A piston rod, with a short and longer bit of thread.​

Piston, rod,  and top cylinder head.jpg
A nice, if I might say so, photo showing the piston, rod and upper cylinder head.​

Next up was the steam chest. This began life as a 3/8" x 1" x 1-1/2" bit of aluminum (it's what I had). I machined it close to 1/4" x 5/8" x 1-1/4" per the plans. I left some extra on the sides for later. I then layed out the main features.

Laying out the steam chest. Outer dimensions are oversize.jpg
Lay out for the steam chest.​

The stock was then centered in my Sherline 4-jaw chuck and valve rod end was drilled and then turned. The first operation was carefully drilling through the stock with a 1/16" drill to where the end of the blind "alignment" hole will be. I then drilled for the valve rod clearance and the stuffing box threads. This operation is not shown. I keep forgetting to pick up the camera.

I then reversed the piece in the chuck and turned the blind end. I then used a file to shape the blind end end. Or I ended the end with a file to make it end.

Steam chest closed end.jpg
The steam chest 'closed' end, nicely shaped with a file and a prayer.​

The part was then transferred to the mill. I found the center, and then milled out the opening. I Initially used plunge milling along the edges, leaving 30 thou for final milling. The end mill was a 1/8" double flute.

Chest pocket machined.jpg
The steam chest center being roughed out.​

I then drilled the clearance holes for the mounting screws.

Clearance drilling mounting holes.jpg
Steam chest with mounting clearance holes.​

I then made the steam chest top and valve plate. Again, I did not take any photos in progress. For the parts I started with two bits of 1/16" brass sheet stock cut close to the right size. I then glued them together and machined the sides square to slightly over the final X/Y dimension. Then I drilled the clearance holes for mounting. The plates were then separated. I then surface plate sanded the valve plate (the one with all the steam holes) as flat-ish as I could. Then the steam holes were drilled and the valve plate sanded flat-ish again.

Steam chest parts done.jpg
All the bits for a steam chest.​

I then assembled the cylinder, valve plate, steam chest and steam chest cover.

Time for a little cosmetic work.jpg\
One of my oops is highlighted. But you can see how
everything is just a bit too wide.​

Once all was put together, I put the assembly back in the mill to shave the sides so all was was square and my oops :oops: were removed (hence my oversizing before). I also took a file to the ends of the steam chest assembly to make them square with the cylinder.

Cylinder and steam chest.jpg
Now it all fits nicely.​

That pretty much catches things up to where I am now. The next bit, I think, will be a major change from the plans. And some pillow blocks. At least, I think that is what they are called.

Thanks for checking in.

T
 
Before the pillow blocks, I made the valve rod. This was pretty simple. I started with some 3/16" brass round stock. I turned 1-1/8" to .086. I did this with the stock held only by my 4 jaw chuck. The trick is to turn to the final diameter in one operation, so the remaining 3/16" stock ends up preventing the piece from deflecting.

Valve rod in progress.jpg
The 3/16" stock turned down to .086 for 1-1/8 inches.​

I then flipped the part in the 4 jaw, re-centered it, and parted to leave 5/16" of 3/16" stock. Then it was reversed again, leaving just a bit more than 5/16" sticking out. The 1/16" 'guide' was then turned. I then extended the piece enough from the 4 jaw to thread rod 2-56. Of course, I don't show any of this! Argh.

One more time the part was reversed in the chuck and then the chuck was mounted to a hex block. I then mounted this entire bit in my mill vise and the linkage end was machined. First the flats were end milled then, then I drilled for the link pin, then I used a slitting saw to make the gap for the link.

Drilling hole for the pin.jpg
Center drilling for the link pin hole.​

Slitting valve rod.jpg
Slitting the link pin slot.​

Completed valve rod.jpg
Valve rod completed.​

Progress so far.jpg
Valve rod in situ.​
 
I am traveling to see family over the next few weeks, so no build updates. However, I can show you my first attempt at pillow blocks. They are pretty terrible, and will be redone upon my return. The dimensions are 3/4” long, 3/16” wide and 5/16” high. The bearing is 1/8” diameter centered 3/16” from bottom. Block material is grey cast iron, the bearing is brass.

P6120092.jpg

Once I figure out how to make them I will post more detail on how I made them. And when the trees are rustling, the wind is blowing. Or your going to be attacked by a squirrel hoard.

Squirrel Hoard would be a good band name.

Until July, thanks for following along!

Tom
 
OK, so where were we... Right, I was going to build some better pillow blocks. Thus, I made the steam chest valve.

Here is the part I am making:

Steam valve plan.jpg

This started out as a bit a of 3/8" square brass that I machined to 1/4" x 9/32" x 1-1/2".

Valve stock.jpg

I then layed out the slots and the total height of the part. This was surprising difficult given my large, but un-dexterous fingers.

Valve stock layed out.jpg

The 1/16" slot was done with a 1/32" end mill. Take very shallow cuts, or you will be replacing your 1/32 end mill. A week later, I finished milling this slot. I then milled the 0.90 slot using a 1/16" end mill, taking very very shallow cuts. Each slot was initially taken to .01 of full depth, then widened to within .005 of full width, then take to full depth, and then to full width. All depths were confirmed with a depth micrometer, and widths were confirmed by using drill shanks. A more anal person would have used gauge pins, thus I am so ashamed. This was as easy as Mr. Brown had it with Paddington. But, I was probably being far more precise than I needed to be.

[Aside] If you have never read the Michael Bond authored Paddington or Monsieur Pamplemousse books you really must. They are examples of simply great writing. The other writer I am in awe of is Bill Bryson. The execution of the simple sentence is brought to new heights by him. I highly recommend "A Short History of Nearly Everything". Each sentence is a lesson in writing well. Which I clearly have yet to absorb. [end aside]

Valve first cut.jpg

Valve second cutg.jpg

Valve cuts done.jpg

I then used a slitting saw to cut the part off the stock. I left a few thou extra in height, which was then taken down to spec by sanding on a surface block.

The part was then placed back in the mill vise, with the slots down, indicated, and the inlet steam pocket was machined using the new 1/32" end mill.

Valve bottom pocket done.jpg
Almost finished valve.jpg

The last step was making the valve nut. Here is the plan:

Valve nut plan.jpg

I used some 1/16" brass stock, which I cut oversized on the bandsaw. I then took the stock to final dimensions on the mill, and drilled and tapped for the 2-56 threaded valve rod. Of course, I did this three times, but not for my health. It turns out a fixture and some cyanoacrylate glue is very helpful with this step.

Valve nut stock.jpg

And this is all the parts assembled:

Valve assembly done..jpg

I am trying to understand the R (radius) function on my new DRO from Precision Matthews (along with my new PM25 mill). I plan to use it to make a better pillow block. Unfortunately there is a bit of separation between my understanding of english and the DRO manual's english.

Thanks, as always, for following along.

Tom
 
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