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Grasshopper engine build thread

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tomw

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#1
Dear All,

I have decided to put together a build thread for my next engine, Elmer Verburg's Grasshopper (grasshopper beam )engine. Plans are here. I decided on this engine because the mechanism of operation is interesting. This article at Wikipedia discusses how it operates.

The design is really going to push the envelope of my Sherline equipment. So, I also am using this build as an excuse to upgrade my mill to a PM 25V:cheerful:. Unfortunately, the mill is not here yet, so we will see how things proceed.

I posted a little bit ago the making of the flywheel. That post is here.

The next bit I made, because I had the metal on hand, was the crankshaft.

First I turned a 1"-ish long bit of 1" round 12L14 to clean up it up and bring it to nominal size and drilled and reamed the 3/16" center hole for the shaft (operation not shown). I then transferred the chuck to my Sherline mill and centered the piece under the spindle with my CoAx. I then drilled and tapped the offset for the connecting rod (5-40). Then the counter-weight profile was cut.

Crankshaft journal profile.jpg
Cutting the counter-weight profile using a 3/8" 2 flute endmill.

Crankshaft journal profile finished.jpg
Finished counter-weight profile. I followed up with some light chamfering.

I then returned the chuck to the mill and carefully parted off the piece, leaving the width 10 thou oversized. I always seem to get a bit of scalloping when parting. The extra material was removed by draw filing to the final width, with some light hand chamfering of the edges.

The shaft portion of the crank is 1/4" drill rod (W2) cut to proper length. I turned the mounting shoulder to a shrink fit. Then I chilled the shaft in my freezer, and gently heated the journal with a propane torch. I then put the journal and the shaft together with just a touch of green loctite. After returning to room temperature, the pieces are quite solidly joined.

Crankshaft shaft.jpg
Turning the shoulder on the shaft, or a nice picture of my power strip.

Finished crankshaft.jpg
The finished crankshaft. I may try to smooth it a bit more.

Next up is the beam. This is a bit tricky, since the pivot point is off-center. Also, the location various attachment points is critical, so careful measurements must be done.

Until then, thanks for watching!

Tom
 

solo

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#2
I looked thru the plans, boy there's some small tap sizes in there. Always scared me, when I went under a #4.
Neat project. I'll be watching to see how it comes out!
 

tomw

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#3
Dear All,

The next bit to make was the beam.

Beam plan.jpg
The plan​

I wanted to do this entirely on my rotary table (RT). The general shape trapezoidal shape could have been done in a multitude of other ways.

I also decided that I wanted my beam to be more beam-like than the plans. Thus, I relieved the web such that it was 3/32" thick and the flanges were 1/16". Here is a layout version.

Beam Layout.jpg
The layout​

This took a fair amount of math tracking, but with my DRO and RT proved not a problem. Or not a problem after a screwed up the first two tries. It turns out that even small screw ups (.02 or so) on any axis (X, Y, Z, R) can ruin the part!

My first step was to square and dimension my stock. I started extruded 6061 Al, .25 thick. x 1", cut to close to length. I machined the cross section to nominal size and the length to about .5 over.

I then made a jig that would allow me to slide the part in the X plane in a fairly precise manner. I started with 2" x 3/8" 6061, and machined to square and flat. I then milled a slot to fit the width of the my stock. I then made the length pretty close to the length of the beam stock. I then found the center of the jig, and drilled and tapped holes .75" from center to a distance of 2-1/4". The holes were tapped for 2-56. This will allow me to bring each feature I need to machine under the spindle center.

Beam Jig.jpg
The jig​

Once the jig was made, I mounted it to my RT (already centered below the spindle), being careful to keep everything square (indicators and all that) The location of the main pivot point (a tapped hole) was then centered under the spindle (and at the RT center). NOTE: the main pivot point is 3/4" from the center of the beam, thus the jig is 3/4" displaced off the RT center. This took a bit of fiddling. I then glued my stock in place with cyanoacrylate glue.

Finding center.jpg
Using my pointer to point out the beam pivot center.​


I then drilled the main pivot 5/64". This would become my longitudinal center. I then drilled the other pivot points per the drawing. I was very careful to not go very far into the jig. I followed this up with a 3/32 reamer. I then removed the stock with some gentle heating to release the CyA glue. I de-burred all drilled holes, and removed the glue from the stock and fixture. I could now use 2-56 screws to hold my piece in the x plane where I wanted.

I used clamps and adjustable parallels to move things in the Y, as you will see.

Set up for moving in the Y.jpg
A bit fuzzy, but making things square for the move.​

Wow, that is a lot of words to describe only a few hours work. Crap.

So now I had my set up, all I had to do was some simple math to figure out angles and distances. I decided that I wanted the flanges of the beam to 1/16" thick and the web to be 3/32" thick. The bosses for the pivot points would be the full 1/4" thick, per the plans, and 5/32" in diameter. I machined the outer trapezoidal shape first.

Making the main beam angles.jpg
Outer edges​

To do this, I had to displace the jig (and stock) 1/2" plus half the cutter diameter (.125, in this case) along the Y dimension. I then rotated my RT 6.6 degrees for the long leg and 12.9 degrees for the short leg and machined the slopes. The whole setup was then moved the to the other side of the part and the process repeated. Given my Sherline mill, these were initially plunge cuts about 20 thou oversize, followed by successive finish cuts to final size.

Once the general shape was done, I started the internal relief. So I moved my Y to the correct spot, and then milled a groove along the flange using my 1/8" end 2-flute end mill. I had also calculated my depth a cut, and set my depth stop.

Cutting the internal relief.jpg
Inner flange edges​

I then decided it was a good idea to do the ends of the beam. I don't remember why. But it would have involved moving my stock such that the ends were under the spindle and centered on the RT, then offsetting in the X to make the radius. So I did the ends, and then reset my depth stop and finished the flange (which meant moving the jig in the Y to match my flange and cutter dimensions).

Finish the internal edge.jpg
Inner flange edges and ends finished​

I then undercut the pivot bosses, moving the stock such that each boss would be centered under the spindle (thus the multiple tapped holes in the jig).

Machine the bosses.jpg
Pivot bosses​

Then I finished off machining the web. The piece was then flipped and most of the process repeated. The first end boss was cut by eye, and then the RT setting was using for all other cuts.

All done but some filing.jpg
A bit of clean up​

The now milled piece was obviously in need of help. So the web was filed and sanded, and a small flange mistake was filled with PC-7. Since the part will be painted, this seemed OK. Particularly since this was my 3rd try. My 1st try was actually pretty good, but this was better. Don't ask about my second try.

Post filing.jpg
Done-ish​

In primer.jpg
Here it is in primer​


Next up is the cylinder.

Cheers,

Tom
 

tomw

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#5
Thank you to all who are following along!

Last weekend I made the cylinder and the heads. The cylinder is Elmer's type F. The plan is in this document.

The cylinder was made from aluminum bronze because I had some and I thought it would nice. I started with a hunk of 1"-ish square stock that was then milled to 1" x 1" x 1-3/8.

Squared Al bronze stock.jpg
Cylinder stock is a milled Al bronze piece 1" x 1" x 1-3/8"​

I then layed out the steam ports, steam inlet, and centers for the cylinders. After mounting the stock in the vise and centering under the spindle, I drilled the 1/16" steam 'inlet' ports. This was followed by chain milling the 'cylinder' ports using a 1/16" end mill to a depth of 1/8".

Spot drilling intake ports.jpg
Afer a bit of layout work, the stock was centered under the spindle. Here I am center drilling the steam inlet ports.​

Milling steam ports.jpg
I used a 1/16" end mill to cut the ports for steam going to the cylinders​

I don't have a picture, but the next thing I did was drill the hole for the intake on the side of the cylinder. I have circled that hole in the plan below.

Inlet plan.jpg
Where the steam inlet is drilled​

The piece was then moved to the Craftsman lathe for cylinder boring and machining the cylinder head flanges. The center of the bore is 17/32" from face with the steam ports, so the stock was shifted 1/32" from center in that direction in the square jaw chuck. If you know what I mean.

Squaring up for lathe operations.jpg
Setting up for drilling and boring the cylinder bore. Note the 0.031 offset on the dial gauge.​

Once I was set up, the bore was center drilled, then drilled 3/8" and then bored to .508. It should have been .5, but I had brain fart. This happens enough in my shop that I need air freshener.

Boring cylinder.jpg
Boring the cylinder on my 1953 Craftsman 12"​

At this time I made a tight fitting aluminum plug gauge for the cylinder. I did this on my Sherline. This will be required later.

The next step was turning the cylinder head mounting flanges. Per the plan, these are 1/4" thick and 15/16" in diameter.

Rounding cylinder flange.jpg
Turning the first cylinder flange.​

I then reversed the stock in my 4-jaw and, using my previously made plug gauge checked that the cylinder bore was still centered in the chuck. Probably not necessary, but I did it anyway. Also, I could have used a DTI to do the same thing without making the gauge. But I used the gauge later, so all is good.

Centering bore.jpg
Checking that the bore is still centered after reversing the part.​

I then turned the flange.

Turning other cylinder flange.jpg
Some flange turning.​

Cyl. progress.jpg
Finished with lathe work.​


Back to the mill for the drilling the steam passages and recessing the sides. To set up drilling the steam passage I used some angle gauge blocks to position the cylinder in my vise at a 17 degree angle. The plan calls for 16.5 degrees, but over that short of a distance .5 degrees off will not matter (I checked. It won't). Once at the correct angle I centered the bore under the spindle (using my bore gauge block to indicate from), then found the cylinder edge using my wiggler (not shown). I then used my dti to offset 1/32" in the x, centering the spindle over the steam passage. You will note in the photo that the stock is not being held in by much meat. I noticed this as well, and changed the set up. I don't show this, but the steps were the same except for where I put my angle gauges.

Setting up to drill steam passages.jpg
Offsetting from the cylinder edge 1/32" to the center of the steam passage. Note, the set up was
changed to grab the part more firmly.​

The steam passage end was then milled flat using a 3/32" end mill. Then the passage was center drilled and then drilled 1/16" through to the steam ports. I used a small drill in the steam ports to determine when I had gone through (I could feel the 1/16" drill hit my 'indicator' drill). The part was then flipped in the vise, centered and such, and the other passage completed.

Machining flat for cyl. steam passage.jpg
Milling the passage flat​

Drilling steam passage.jpg
After center drilling, the passage was drilled though to the steam chest port. Note the small drill
in the port to feel for the passage drill breaking through.​

Finished passage.jpg
Steam passage finished. This is actually the second passage.​

The next step was to mill down the recessed sides of the part. This is just basic end milling. However, bronze is a very grabby metal, so at least on Sherline you need to take light cuts. Also, once you are near the flanges, you need to take even lighter cuts. At least if you start from the center and go nearly full depth like I did.


Recessing cylinder sides.jpg
Milling the side recesses. I started by milling a slot to almost full depth and then working my way towards the flanges.​

Milling to the flange.jpg
As you get near the flanges, you need to go slow.​

Oops.jpg
Grabby brass + bozo = Oops​

smaller oops.jpg
Another oops. Luckily I did not mill the recesses to full depth, so I will be able to clean up the oopsies.
I will do that after I attach the steam chest and valve plate.​


This post has gotten long enough. I will discuss the cylinder heads next time. Until then...

Thanks for following along!
 

solo

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#6
Wow. Great work even with the brain farts. I've been watching, and thinking I'd like to build one too. But... maybe double the size, so I don't have to deal with such small bits. I fix enough stuff at work that people break, I don't want to break my own tools.
 

tomw

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#7
Solo,

The design should certainly scale. Because the tapping is all shallow or through-holes, tapping is really not a problem. However, it does take time, with lots of cycling in and out with the tap with tap cleaning in-between.

Don't be scared, embrace that small bit adrenaline :fat:.

It is an interesting engine.

Tom
 

tomw

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#8
OK, now on to the cylinder heads. I did not take a lot of photos, or a lot of photos in focus. So this is a bit sparse. First up is the upper cylinder head.

The top cylinder head started as chunk of 1" brass round stock. The plans call for aluminum, but brass will be a better look with the bronze.

The 1" stock was turned to the 15/16" final diameter for about 1/2".

Making the top cyl. head.jpg

I then turned the 5/16" dia x 3/16" depth stuffing box. I then drilled #41 through and #21 to 1/4" depth.

Drilling stuffing box on top cylinder head.jpg

The part was then parted off to leave some material for turning the cylinder register and facing to final thickness.

Parting cyl. head.jpg

The part was mounted in my the 4-jaw and centered. The face was checked to make sure it was perpendicular to the Z axis of the lathe.

Getting set to skim cyl head flat.jpg

I then faced the part to 1/8" thick, followed by making the 1/32 thick (or deep) cylinder register. Unfortunately, I have no photos of this, so a drawing will have to do.

Upper cylinder head.jpg

Right, I have to go make dinner. So cylinder head will be finished later. Really.
 

tomw

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#9
And now we continue with the cylinder heads. Ah, I remember my first head, it was back in '13. It was to be mill engine...but it didn't work out. But I learned, and things are easier now. Just, I, dunno, the experience is not the same as that first time.

The first step was to cyanoacrylate (CyA) the upper head to the cylinder, and then mount the parts in the mill vise. The part was then centered under the spindle, registering off the stuff box. I then calculated the correct bolt pattern (using an app on my iPad). I then center drilled and drilled the head holes, going slightly deeper than the head flange (3/32").

Drilling for head bolts.jpg
Drilling the clearance holes on the upper cylinder head.​

The head was removed with heat. The previous operation had left starter dimples on the surface of the cylinder flange for further drilling. I then drilled into the body the cylinder with a #50 drill 3/16" further. I then used a 2-56 tap to thread the holes into the cylinder flange.

Tapping 2-56.jpg
Tapping the upper cylinder head.​

Almost finished cyl. head.jpg
The upper cylinder head and the cylinder​

The next step was to make the bottom cylinder head, also out of brass. I have almost no photos of how this was done. The head is a square piece with a centered 1/32" cylinder register. The extent of the square is used to mount the cylinder assembly on the base, as the cylinder assembly in this design is positioned vertically. A piece of accurately squared stock was mounted in a 4 jaw chuck and then the register was turned. The piece was flipped and then turned to final width.

Perhaps, again, the plan will help see this.

Lower head plan.jpg
The lower cylinder drawing.​

I then positioned and glued the head to the cylinder such that it was square to the cylinder recesses. This was a pain in donkey. If I was going to do it again, I would make my original stock a bit oversized and then square it to size once I had it attached to the cylinder. I then did basically the same operation as on the top head to drill and tap the cylinder mounting holes. The only difference was I did not remove the head between doing the clearance holes and the tap holes.

I then countersunk the holes, as this head mounts flat on the base, so the machine screws are flat heads. Because counter sinking is sort of a grabby process, particularly with brass, I used some screws to hold the head in place.

Countersinking.jpg
Woo hoo, countersinking the doohickey.​

One thing I forgot was drilling the holes to mount the cylinder assembly to the base. Since the part is really square, this won't be a problem to do later.

Here, as our story continues, is the result of this monkey business:

Finished cylinder with heads.jpg

And this is a good time to ask:

  1. Do you prefer the black and white or color photos?
  2. Are these posts to long?

Next time we will tackle the piston and steam chest! Oh my, the excitement for the next episode might just make the internet explode.

Thanks for reading along.

Cheers,

Tom
 

tomw

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#11
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
 

tomw

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#12
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.​
 
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