Scaled down Popcorn

[steamer]

Nice progress there Arnold!   Love seeing the calipers being used "Old School"..

Dave

[EmanMyford]

Also following Arnold. I agree with Dave I love "Old School"   

Kind Regards.
Ewald

[b.lindsey]

Quite a nice start Arnold...will be following along with much interests here. Not an expert on popcorn engines by any means but as to the hardware, I'd go with whatever is historically accurate, even if that is slotted screws.

Bill

[arnoldb]

Many thanks Gents 

No progress tonight - I had a hectic day at work, so the only things I'd be able to make successfully are booboos.

I did a bit more research on the fasteners though.  Nearly without fail, the oscillating Cretors engines used screws from what I could see.  The Dunbar style like this one however, seems to have used hex bolts on the cylinder heads, and studs for the steam chests.  That suits me down to a T - the studs on the steam chest makes setting the valve easier, and I can knock up the eight (well 10 - the shop monster always wants a treat) 2mm hex bolts needed from some stainless rod easily enough.  All other visible mounting fasteners appears to have been screws.

Kind regards, Arnold

[NickG]

Nice 1 Arnold, this will be interesting to watch. 

[steamer]

Oh goodie goodie!
 
Another bolt making lesson!   Can't wait Arnold! Still deciding on the best way to do this.......though I have some unsubstantiated opinions...

Dave
 

[Jo]

Making small bolts/studs are just so much fun to make (if in small volumes).

As Dave has hinted we have recently been having discussions on making these , so I am looking forward to seeing your way of doing them Arnold .

Jo

[arnoldb]

Thanks Nick 

Dave, Jo - I've been following your discussions on making fasteners very closely, and taking in things along the way  .  Don't be surprised if there's some methods blatantly stolen learned from either of you used when I get around to making things.  Some bits might get adapted to the equipment I have available - but I don't think there will be any really new methods. 

Making small bolts/studs are just so much fun to make (if in small volumes).

There was a time when I dreaded this Jo, but you are right - One lesson I learned only lately is to treat the fasteners just like any other small part of an engine build - and that is to make them with care and try and do a good job on each and every one.  Instead of being "just" fasteners, they become a part of the whole experience and satisfaction of building an engine 

  I had a bit of shop time after work today.  Not much, but every bit helps.

I started off by milling a bit of 10mm thick aluminium plate to 16mm wide.  I still don't own a set of parallels, so I make do with the crude bits I've made up along the way:


One end of the block of material was squared up as well, and then a bit of layout followed.  A section of this lot will become the steam chest.  The punched hole on the end is the center point of the valve rod bore, and the marked out section around the edges have to be turned down to form the pack nut spigot:


On to the lathe, and clocked up in the four-jaw chuck.  I must really make some time to make a proper pump-center rather than using one of my dead centers all the time:

The workpiece is standing out from the chuck quite a way - I wasn't in the mood to cut up an old cooldrink can to make protective packing from and I didn't want to mar the surfaces of the bit that will make the steam chest.

Spigot turned down - just by eye to split the mark-out line for the length:


Next it was properly center drilled, then drilled through deep enough with a 2mm drill that the hole would end up in the steam chest, and then drilled 3.3mm for 5mm deep and tapped M4:


As I didn't have too much shop time remaining, I decided against taking the workpiece to the mill to start machining out the inside of the steam chest, so I grabbed a bit of 5mm hex brass and did a bit of work on that to make the valve rod pack nut - here just parted off:


And de-burred a bit - more finishing required:


On to meatballs and baked potato for me now 

Regards, Arnold

[tvoght]

Mmm popcorn...

 I'm here and watching. Saw an old Hitchcock movie the other day "Strangers on a Train". There was a brief shot at a carnival featuring a running popcorn engine.

--Tim

[swilliams]

Looking Good Arnold

Tim - I gotta check that Hitchcock movie out now you mentioned that, I think I have it somewhere

Steve

[arnoldb]

Tim & Steve, thanks for looking in 

  Maybe I must take the time and try and look at that movie...  It's not something I do on a regular basis!

Not much of an update today; there was all sorts of things that happened  Cleaning blocked sewers isn't a good start to the day and a call to a "Work" work site took some more time.

Enough complaining - and on to the bits that did get done.

I carried on work on the valve chest.  Clamped it up in the mill, and used the edge finder and DRO to find the center of the valve chest.  Then spot drilled a couple of locations from coordinates:


Then drilled 2mm holes in each location.  The outer holes are the mounting holes, and the inner holes are the inside corners of the valve chest, offset 1mm towards the middle in both X and Y to compensate for the drill's thickness:


The cut-out in the steam chest had to be machined to 8mm wide and 14mm long.  I drilled two 6mm holes in the center portion - just touching one another; that left little material to machine out, so I roughed things out with a 4mm end mill at full depth, leaving the hole 0.2mm under size on each edge.  The left over bit was then given two more passes - taking out 0.15mm on the first and 0.05 mm on the last to leave a nice smooth finish:

There's still some cusps left where the 4mm mill could not get into the corners to join up with the 2mm holes I drilled earlier.  Just a bit of file work needed there.

All the holes and the milled edges were de-burred, and then a hole was drilled 5.5mm and tapped M6x0.5 for the steam connection.  I had to be careful to get the hole on the correct side - on just about all the builds I've done so far requiring steam chests, the chests were symmetrical, but this one is not, so cannot just be turned around to get the steam connection on the correct side:


As a last machining operation, I slit the steam chest off the parent stock using a slitting saw.  It leaves less machining marks to clean up than using a hacksaw and can be done to size.  I stopped the slitting cut just before the part was all the way sawed off - it had just started to "peel up" a bit:

The last sliver holding it on was just broken off.  Saves on from having to go in search of a part flung across the shop, and also saves the part from getting dings from getting flung 

After a couple of strokes with a file to neaten up the cusps left in the valve chest, and a rub across some 320 emery to tidy up the outside and faces a bit, it was done for the moment:


It fits nicely on the cylinder.  The cylinder edge on the front side is still a bit high, but that's because I didn't  finish it down completely to size there yet - I'm pondering something, and that lip might come in handy... :

The bit of bronze rod stuck in the valve pack nut was just a test.  All the rods on this build will be stainless steel.  And I'll have to turn them up as needed; the smallest diameter stainless rod I've been able to find locally is 3mm thick and the valve rod must be 2mm and the piston rod 2.5mm...  I'll have to build a box tool "a la Tel" for that.  At least I got a bit of a bargain with the stainless - I only paid for 3m of 3mm rod (the cutting charge makes 1m more expensive than 3m), and the supplier had a couple of 4mm off-cut sections that they threw in for free - they normally only sell by the meter and the two bits are about 550mm and 680mm long - and thus not in their "selling" range.  I had to promise them that I'd bring along the engine once finished to show it to them though  . 

On to the bearing columns, and a bit of 6mm aluminium plate roughly sawed from stock:


That was sawed through the middle again, the two bits clamped together with a toolmaker's clamp, and I started squaring and straightening edges in the mill:


Shop time on the Popcorn stopped abruptly there.  It was rapidly getting dark outside, and I thought it was just getting late (I don't check the time when I'm in the shop).  Suddenly a gigantic thunder-clap made itself heard...  I have two dogs - the dog is OK with thunder, and is also allowed in the shop while I work as he just picks an out-of-the way spot to lie down and sleep, but the bitch is extremely naughty (she steals tools or supplies and chew on it - to destruction) and is normally barred from the shop.  She is also terrified of thunder and will break the no-shop rules for that.  I suddenly had a terrified bitch under my feet, and the rapid darkness became evident.  It wasn't late, there was just huge clouds in the sky.  The next thing there was the pitter-patter of raindrops on the shop roof and more thunder and lightning - LOTS of it.  Waaay early this year for our first rain of the season - it's only four months since it last rained - and I hadn't noticed the clouds building outside.

During electrical storms, our power is likely to go out at any moment - and nothing is as frustrating as being half-way in a cut when the power goes off - besides, there were more important considerations at that point. 
My day may have started with cleaning crap, but it had to be done.  Some Work - that's how I earn a living, and I really do enjoy my job.  Some Shop time - that's what I do for even more fun. 
The best bit of the day:  Closing up shop, pouring a generous dram of quality Scottish produce on ice, sitting down on the stoep (porch) and enjoying the sound and smell of the first rain of the season coming down.  Ever since I can remember, the first rain of each year is the biggest treat of all - it makes me feel "alive".  A great day all-in all 

Regards, Arnold

[steamer]

Looking great Arnold!   she is a mini isn't she!

Dave

[Bearcar1]

'Scottish produce" LoL!    "That stuff will make you go blind ya' know." "I see." No you don't." "Yes,,, I do." "Than you need another drink!!"


It sounds like you had an enjoyable end to a what started out to be a (wait for it) crappy *oh groan* beginning to your day, Arnold. I too remember as a young lad, sitting on the front stoop wearing only a pair of shorts while the rain and breezes blew in from the West, cooling things down from the days high heat. Ahhh, truly refreshing.    I like the progress you have been making so far, very nice indeed. Hope the dogs both made it through the storm.


BC1
Jim

[arnoldb]

Dave, thanks bud  - Yes, it's a bit small, but it's actually scaling out to be pretty much on equal size with most of Elmer's engines; it should fit right in with the rest of my little collection 

Jim, Jim, Jim.... Groan. At least it's not Prohibition Moonshine  - that stuff apparently really made one blind.  The dogs are fine - in fact they ended up running muddy pawprints into the house  .  Thanks my friend; the progress is a bit slow, but it'll get there 

Today's little bit.  The material for the bearing columns was still clamped together with a toolmaker's clamp like in the last photo.  The clamping position had to be moved for the next operation without disturbing the alignment of the workpieces, so I just added another clamp in a suitable location and removed the original.
Then I set the lot up in the mill vise, and with a bit of business card against the moving vise jaw, clamped the lot up.  The thick cardboard takes up any small play there might be, so both pieces are held securely.  I located the vise fixed jaw to find 0 for Y, and the right-hand edge of the workpieces to find 0 for X.  Then I dialed in the coordinates for the bearing bush hole, and drilled it 6mm for the bushes.  I didn't ream the hole; when I turn up the bushes, I'll turn them to a suitable fit:


Next, a 10mm end mill was used to form the curve on the base:


A 3mm hole followed for the mounting point of the cross-head.  The one bearing block has an "extended" bit for mounting the cross-head, and the other doesn't, so I first made sure that the additional machining operations on the "top" block in the vise wouldn't affect the bottom one:


With a cosmetic 6mm hole following - even if it does not look cosmetic yet - and a bit of milling to form a 2mm deep recess where the cross-head would be mounting, I ended up with this:


I've been taking a lot of liberties with the bearing blocks so far.  The only essential dimension I've kept to is the height of the center line of the bearing hole from the base - that worked out at roughly 20mm, so I set it firmly on 20mm - as this affects both the height of the cylinder mounting and the valve guide.  As I did stuff around so much, I needed to calculate some new dimensions for the cosmetic work on the bearing blocks.  An arm-chair machining session followed in QCad to calculate some dimensions based on the tooling I have available, and I had a couple of dimensions forming the rest of the bearing block.  Not as pretty as Stew's original though - but it'll have to do:


One thing I can't recall having used thus far while machining is a jig - but this job needed one.  I faced off a bit of much-abused aluminium plate, and drilled a 10mm hole in it - setting the DRO to zero on that.  Then I drilled a 6mm hole 20mm away from it - to match the bearing block dimensions:


A slightly rusty slug of 10mm steel bar was knocked into the 10mm hole (the rust helps make it a tight fit  ), and the shank of a broken 6mm milling cutter was pushed into the 6mm hole - with a bit of plate underneath it in the vise to prevent it falling through:


With one of the bearing blocks clamped down on the jig, I used a 10mm drill to remove most of the excess material:


Then, with a 14mm end mill, I milled the rest out to the dimensions from the CAd drawing shown earlier:


The workpiece was flipped, and the operation repeated, and for the second bearing block, only one side received the treatment.  The side of it with the mounting tab on it couldn't be machined like this, as the 14mm end mill was too big and would remove a part of the tab.  Some permanent marker on it, and I used the other bearing block to scribe a line on it to machine to:


Back on the mill, I used a 10m end mill to machine close to the line - some jiggling of the hand-wheels was required:


The machining was followed by - as Jim would say - "character building" in the bench vise to get closer to the line:


There's still quite a bit of work left to do on the columns, but I stopped here for the day:


Regards, Arnold

[sbwhart]

I was reading this through Arnold and thought he's going to forget the extended bit for the cross head guid just as I did:------ but no you got it sorted away nice and safe 

Comming along great 

Stew