Arnold's take on Elmer's #5 Geared Engine

[Roger B]

Nice start to an interesting looking engine    As Jo said any chance of a GA or picture of the engine for those of us who don't know it?

[arnoldb]

Thanks all who looked in and commented

Roger, I added the GA and a link to a finished one to my first post in the thread.

Dave, yes; the cost of the gear appears to put off many.  Hopefully the method I'm going to use will be easy enough for people to home-make - the only cost will be material, some drill rod/silver steel to make the cutters from, and quite a bit of time and effort.

Stan, there's more warts & all in today's post .  Detailed posts are not everyone's cup of tea; it takes quite a bit of effort, but it does pay dividends - sometimes there's details that one overlooks in the photos and others pick up on.  I've learned a lot from others' detailed posts - from those of beginners to experienced model engineers, I still do, and always will.  Each and every model engineer's shop is different; I'm willing to bet there are no two alike shops in the world.  So no matter what is shared in posts, there's always something that needs adapting to one's own shop and tools.  IMO, sharing posts serves to provide inspiration to carry into one's own shop and build upon.

Shop time's been a bit scarce; I had to work quite a bit of overtime (the bane of a career in IT), and catch a bit of rest as well.

Last weekend, some parts were made - not much though. 
I dug around my off-cut bin and found some left-over phosphor bronze bits to make the cylinder covers from.  I started off with a bit that was just about long enough - with minimal chucking - to make the inboard cylinder cover from:


That was turned down to the cover dimensions


Some more drilling - 2.5mm through, followed by a 4.2mm drill about 6mm deep and an M5 tap formed the packing nut part of the cylinder head.

Off to the RT (Rotary Table) chuck and all, and the mounting holes drilled after first spotting them:


Back to the lathe and parting off.  Something was not right, and the parting off went horribly wrong.  My parting tool wasn't as sharp as it should be, and silly me forced it into the cut.  Phosphor bronze can be a bit of a bummer to machine - it work-hardens, and by forcing the cut, that's exactly what happened, with a resultant build-up of heat.  Before I realized what exactly was happening, all the friction had caused the workpiece to flare out at the outside edges - and the face was dished quite badly.  Not a good photo; the camera wanted to focus on the swarf  :


That just plain wouldn't do.  My rear parting tool is a bit of HSS made from one of a rotary wood planer's blades, and a couple of years ago I just ground the blade up roughly and started to use it.  Needless to say, parting's always been slightly problematic, so I decided to spend some quality time to re-grind it.  I could have used the tool & cutter grinder, but it's currently nicely set up to sharpen end mills, so I spent some quality time with the toolbit on the bench grinder - re-grinding all clearance angles and adding quite a bit more back and side clearance to the tool.  After about 45 minutes I was happy.  I re-made the cylinder cover as shown earlier, and at part-of with the newly ground parting tool things went wonderfully, with a good finish to boot  :


To finish the other side of the cylinder head, I mounted it in an 8mm collet and turned the back.  On the inboard cylinder head, it's quite important to have the locating ring concentric to the piston rod bore, as well as a good fit to the cylinder bore.  If it's slightly off-center, it will cause the piston to bind in the cylinder bore at full stroke:


Inboard cylinder head finished - dud one on the left and good one on the right:


While I was about it, I also finished the outboard cylinder cover - I dind't take photos of the machining process.  It was just turned to size, the face skimmed down to make the thin sticky-outy bit that fits in the cylinder bore, drilled on the RT, and parted off.  The small parting pip was removed with a file, and the outside face rubbed on some 600 emery to smooth it out:


Monday after work I had some time, so I started on the valve chest.  Some 6mm aluminium plate was milled to 15.9mm width.  I don't have a parallel set - just some bits and bobs I made, and at times I have to bodge things together to mount work.  The workpiece is sitting on a copy of the home-brew "V" block shown between the movable vise jaw and the workpiece - that gave a good height for machining.  As the "V" blocks are 10mm thick, I had to add the one at the top to be able to clamp the 6mm thick workpiece:


After sawing a bit of the workpiece off to just over length and cleaning up the sawed ends, I layed it out using permanent marker and digivern.  The center point on the end was given a good poke with the scriber:

(Apologies for the fuzzy photo)

That was mounted in the 4-jaw on the lathe and clocked up:


And turned to the scribed line and _just_ till the extended end was round:


That was then center drilled.  For the most part, I only have access to metric material and tools.  From previous Elmer's builds, I've learned that the best sizes to use for one of his standardised valve chests like this one when working in metric is to use a 2mm rod instead of the .086" (2.18mm) specified and thread it M2 instead of #2-56.  The core diameter of M2 threads is slightly less than the 1/16" (1.6mm) specified for the end of the valve rod - it ends up with some thread scoring.  1.5mm for that bit seems to work OK, so that's what I use.  So I drilled the end of the workpiece with a 2mm drill to just about the depth of where the 1.5mm section should start:


Then finished off into the other end of the workpiece with the 1.5mm drill - just short of breaking through the end in the headstock side of the chuck:

This is quite a deep hole compared to my 1.5mm drill's length - there was only about 5mm of the drill shank chucked up in the drill chuck...

For the packing nut, I drilled 6mm deep with a 3.3mm drill, and tapped it M4.  This is smaller than the 3/16-40 thread specified, but well within usable limits, and may help make a nice (in my opinion) aesthetic change later:


Now for a naughty bit...  The other end of the workpiece must be turned down to form the nice domed spigot that acts as a valve rod guide.  I didn't bother to lay out the center on that side of the workpiece.  I just loosened two adjacent jaws (#1 and #2) of the 4-jaw chuck, and reversed the workpiece end-over-end. Then I tightened up the same jaws just about as hard as they were previously, and started turning down the end of the workpiece.  Not very accurate, but plenty good enough for this cosmetic bit, and most likely no-one will ever know...  Well, no-one that read this anyway  :


Final profiling of the end was done with a small, fine file:


After a quick rub on emery to tidy it up a bit, I left it at this on Monday evening:


A quick family photo thus far:


I'll stop posting here for now; today was a good day in the shop, and there's a bit more to report, but it's time to make some grub first...

Kind regards, Arnold

[Johnmcc69]

Very nice work Arnold! A neat little engine to watch run.

 John

[Don1966]

You certainly make it look easy Arnold and she sure is looking the part. Nice work as usual bud........

 
Don

[b.lindsey]

Another great update Arnold. Nice looking parts too. This one has always been on my build list but like many the gear put me off so I am looking forward to seeing how you make it.

Bill

[Kim]

Great progress and an informative update.  I'm watching and learning!

Thanks for taking the time to post your informative updates. I know they do take time.  But I want you to know that I for one, enjoy them.
Kim

[arnoldb]

Thanks for checking in Gents 

I was supposed to add more yesterday evening, but after dinner was knackered, so went to bed instead...

Some more - from yesterday's shop session.  This one might be a bit long...

The first job was to finish the valve chest.  I clamped it in the milling vise, and used an edge finder and the DRO to locate it's center position:


Then I spot-drilled the mounting holes locations and the center position:


And drilled the mounting holes and a center hole:


The width of the cut-out in the steam chest comes to 8.7mm Rather than going round and round with a small mill, I decided to remove the bulk of the material in the hole first.  I used an 8mm drill to drill out the center - that left about 0.35mm for clean-up on the "narrow" sides:


That was followed with an 8mm mill to clean out the long sides, leaving about 0.3mm on them as well:


A quick calculation gave me the readings to mill to using a 4mm mill to finish the cut-out:


I made a pass with the 4mm mill still leaving 0.2mm "meat" on all edges - this was more to remove the bulk of the material left in the corners from the previous milling step.
Then a final pass followed, taking the last 0.2mm off on all sides:


The last machining operation on the valve chest was to spot the location for the steam connector:


I drilled and tapped it a bit larger than the #5-40 specified; I went for M4.  This makes turning up the steam connector easier later on:


A quick treatment with a small file and a final rub-down on emery later, the steam chest was finished:


I dug around my bits and found a small bit of brass plate to make the steam chest cover and valve plate from.  It's only 1.2mm instead of the 1.6mm (1/16") plate specified, but that's OK - it will work here:


After a rough mark-out, I sawed the bit of plate up, and, feeling in the mood for some hands-on work, filed two joining edges on each bit of plate straight and square:


Then it was off to the bench vise, and I started filing the rest of the sides square and to size - I just clamped the plates together with the previously squared corners and sides aligned:

That could have been done on the mill, but like I mentioned, I felt in the mood for a bit of filing.  Go ahead and call me weird 

I kept the plates together as a pair using a toolmaker's clamp (this one's really starting to look sorry for itself!), mounted that on the mill, located the edges and then center, and set up the vise backstop.  One plate will be returned later to finish the valve passages - so it was easier to do the setup once:


The mounting hole locations was spotted and drilled.  On the last hole (top left), the 2mm drill jumped out of the spot mark and wandered about 0.5mm  - you may just be able to make out that the hole's out of location:


I could just have drilled the holes over-size to make up for the above error - remaking the plates wasn't an option as I'm out of plate stock.  Rather than drill the holes over-size, I used a 2mm mill to open the hole to it's correct location.  The slight slot this made won't be visible once assembled:


A rub over emery followed:


I chose the plate with the best surface finish on both sides to make the valve plate from.  That one was re-mounted on the mill, and the valve hole locations lightly spotted  As the holes will be small, I took care not to spot them too deeply, otherwise there might be small countersinks left around the holes after drilling them, and that is unwanted on the valve plate as it will affect operation:


The holes were drilled with a 1.1mm drill that I bought during the week.  Original size is for a #57 drill which is 1.09mm - so close enough:


The valve plate got another flat-lapping to remove the burrs around the valve holes, and the plate was done.  The shop lighting fools around with photos - the fine grains left by the 600 emery is in different directions on the plates, and makes the one appear dark and the other light...:


A bit more digging around in the off-cuts bin produced a scrap of brass suitable to make the piston rod crank bearing from.  I squared up one end:


Then located, drilled and reamed the crank pin hole - 5mm instead of the 3/16" (4.7mm) specified:


The piston rod is specified at 3/32" - 2.38mm from brass.  I could have turned down a bit of 3mm brass I have in stock for that, but the rod is quite long and should be smooth and even, so that's quite a chore.  I do have 2mm brass rod, but that gets a bit thin for the piston rod.  So I decided to use 2.5mm stainless rod for it.  Only problem is, the bearing is specified to be soldered to the rod.  Rather than do that, I opted to thread it, so I drilled and tapped an M2 hole in the workpiece for that:

At final assembly, I'll just add a drop of thread-locker on the joint to prevent it from unscrewing.

To finish off the bearing, I clamped the workpiece upright - that allowed me to finish of three machining steps without having to move it again.  First I milled it to length (sounds and looks awkward, but the final part is actually lying horizontally on top:


One face of the bearing must also be milled away - the piston rod ends up being off-set in the bearing:


And finally, I slit the bearing from the rest of the stock - stopping just before the slitting saw would toss it to the back of the shop:

It was just broken of by hand then.

A bit more filing followed:


And finished - it doesn't quite look like the drawings, but it'll do  :


On to the piston - I parted it off about 1/4 at the correct length before turning it to about 0.2mm over-size and adding generous chamfers either side, as well as some fairly deep "oil grooves":


Then the last bit was turned down; I've found a good piston fit for Elmer's engines is about 0.015 to 0.02mm smaller than the cylinder bore.  A last check:


Rats - the last cut was too tight - 11.97mm, so 0.03mm under size.  I'll see how it works; if need be, it's quick to re-make:


To finish the piston, I drilled the end 2.5mm to a depth of 3mm, and then 1.6mm to about 7.5mm deep.  The last hole was tapped M2 for the piston rod:


The piston was parted off, and done (unless I have to re-make it later):


For the piston rod, I used a junior hacksaw to cut off the correct length of 2.5mm stainless rod:


That had to be threaded M2 on both sides, so I had to turn down the ends of the rod to 2mm for 3mm long either end:


The tailstock die holder made quick work of the threading:


The piston, rod and bearing assembled (not loctided yet; that will come later):


Seeing as I had a bit of shop time left, I decided to make some more quick parts - the packing nuts.  Some 6mm hex brass was turned down to 5mm and threaded with a tailstock die holder to start the cylinder packing nut:


Then it was drilled 2.5mm to match the piston rod.  When I center drilled it, I made a generous cone at the end with the center drill; I've found this helps quite a bit to keep the packing material in place while installing:


Then I turned the thread run-out groove and started to part the nut off:


After the photo above, the parting cut was finished.  I then turned up the valve packing nut in exactly the same way, except I used 5mm hex brass, a 4mm thread and a 2mm hole.
A bit of clean-up later, I had the two nuts:


Before closing up shop, I put things together loosely for a look-see.  A quick test and the under-size piston works just fine with a drop of oil added to it:


Enough posting for now; I have some chores to do, and maybe get a bit more done in the shop as well...

Kind regards, Arnold

[steamer]

Rapid progress Arnold!.....Looks Good!


Dave

[b.lindsey]

Looks great Arnold. I love that last shot of the cylinder assembly all put together....very nice!!

Bill

[arnoldb]

Thanks Dave & Bill 

I didn't get much done on Sunday - just the valve rod.  I wanted it to have the same looks as the piston rod - that meant making it as a composite of stainless steel and brass as well.

It was started off with a bit of 2mm stainless steel rod 0.5mm shorter than the overall length of the valve rod:


It can be daunting to turn down thin rod for any length.  I do have a box tool that I could have used, but decided to give it a go without it.  For thin work, a super sharp tool on center height is essential.  I've done this cut on bronze rod a couple of times without issues, but the stainless added another dimension, as it's tough to machine.  Too slow a feed rate, and it would rub and work-harden...  I tried anyway.  I first set the bit to just rub against the bit of rod, took the cross-slide reading, and calculated the in-feed reading to come out on final size (1.5mm).  I dialled that in, and started the cut feeding manually but very consistently while looking for a good thin chip coming off.  That worked beautifully - There's no chip-breaker on the tool, so the chip came off as a string - I saved a bit of it and draped it over the chuck for the photo:

There was a bit of deflection; the tailstock end is 0.02mm thicker than the bit closer to the chuck, but that's OK for this job.

I then extended the workpiece a bit further from the collet, and threaded it M2 for 7mm:


It was reversed, and the other end threaded M2 for 4mm - and I ended up with this:


Next I turned a bit of 5mm hex brass down to 4.7mm, and drilled it 1.6mm to a depth of 4.2mm, and tapped it M2.  I "touched" the start of the hole with a 2mm drill (0.5mm deep):


Then added a drop of high-strength thread retainer to the valve rod stem turned earlier, chucked that in the tailstock drill chuck to hold it and keep it square, and screwed it tightly into the threaded hole:

(Might have been a bit over-generous with the thread locker  )

That was left to cure ("go off" for those in the areas of the UK so inclined  ) for an hour.  It was a refreshing 30^oC here, and the thread locker is rated at curing in 15 minutes at 26^oC, but a little extra time never hurts.  Ended up with this lot:


Rather than stuff around with parallels and such to mount it on the mill, I used the tooling plate:


The flat was milled in one pass after determining the depth - and the spindle height was locked there:


The hex bar helped to flip the part 180^o and the other side milled flat as well.  Then I marked the longitudinal position of the hole with permanent marker and caliper.  The Y position of the hole was a bit more important, and I used the edge finder to locate the Y center.  I had a reason to take a lot more care for the Y location in the position the workpiece was mounted.  The link hole that was to be drilled needed to pass through the soft brass, then the tough stainless of the screwed-in shaft.  If the drill hit the stainless slightly off-center, it would immediately wander and the brass wouldn't provide much resistance to prevent this.  It's important to make sure that the center finder's tip is fully engaged on the sides of the workpiece; so I left just 0.5mm between it's bottom and the top of the tooling plate:


Next I used a 1mm center drill to carefully drill into the workpiece, just till I saw some stainless chips emerging among the brass ones.  The center drill's tip is quite rigid at this short extension (if a 1mm toolbit can be called "rigid"):


That was followed by a 2mm drill; the pilot hole made by the center drill earlier kept it nice and true:


To part off the workpiece from the parent stock, I used a bit of 2mm ID brass tubing chucked up in the tailstock chuck on the lathe to act as a "steady", as well as a way to catch the workpiece.  If this was not done, the extended end of the workpiece would pretty quickly start to bend and whip around:


Parted off.  Q.E.D. (Quod Erat Demonstrandum)... or (Quite Easily Done)...  The Latin and English translations both apply - I'm just being a bit facetious; it adds a bit of fun to writing up a post  :


Some very light clean-up work later, the valve rod was done:


Hopefully another update coming Saturday - this week's going to be hectic work-wise.

Kind regards, Arnold

[b.lindsey]

Still coming along Arnold and quite well too. For those of us interested, we know you will get around to that gear cutting sooner or later I feel your pain as to the hectic work routine!!

Bill

Excellent write up and pictures too by the way!!

[Nicolas]

Really enjoying this thread. Great explanations and great photos

Like Bill, I'm also really looking forward to seeing how you tackle those two gears, especially the internal

Nicolas

[arnoldb]

Thanks Bill & Nicolas 

The gears are still a bit away; I'm first getting most of the other bits of the engine done - even though I'm bursting to start on them!

Some more small bits for today.  First up, the valve.  The first time or two I made similar valves for Elmer's engines, I found it fiddly and a bit daunting - but actually it's quite simple to make, even though there's some delicate work involved.  The easiest way is to set things up so that as many machining processes as possible can be done without changing the workpiece.  While the valve can be made from a properly sized block of material, it's MUCH easier to make it from a suitable bit of parent stock, and keeping it attached to that for as long as possible. Many, if not most, other fiddly bits works the same.

I decided to make the valve from some 10mm hex brass; 8mm square would have been better, but that wasn't in stock.  Another member commented off-line about my frequent use of stock on the side of my milling vise without any apparent support on the other side...  It's bad practice to clamp up something on one end of any vise without adding some similar sized (or very marginally smaller) material at the other end.  It's one of those important things that people forget to mention.  Some processes become a habit that one does without thinking, and unless it's a very light job, I always drop some suitable small bit of material dug from the scraps bin in at the other end of the vise.  For the next photo , I made a conscious effort to use a bigger bit and show it.  The workpiece is on the right-hand side, and a similar bit of material is visible on the left:


Most of you by now know that I am a lazy rotter, so it should come as no surprise that I simply set the DRO to X and Y zero by eyeball to the small center pip that was left on the workpiece after I last used it to turn something from:

The valve is hidden in that bit of stock, and there's ample material to machine away, so there was no need to be super accurate and bring out the edge finders...

Then I ran around it in a couple of passes on all sides with an 8mm end mill, after calculating the offset dimensions needed to make the valve's sides:

One thing about those long brass chips - they are super sharp, goes all over the place, and will lodge themselves in one's skin.  That's still OK to get rid of, but with uncanny precision a stream of those chips will land between the top of one's safety boots and socks, and work their way down.  Then they pounce when least expected and penetrate the sock - lodging between boot, sock and skin - and strikes painfully when one takes a step, and while taking off the boot...  Occupational hazard I guess 

A slight deviation from the plans due to the fact that I use metric materials and cutters followed.  Elmer specified different sizes for the X and Y slots on the valve top, but as I have some 2mm brass plate for the valve nut, as well as made the valve rod from 2mm stock, I simply used a 2mm 2-flute cutter to cut both the slots specified for the valve top.  These were done with slightly greedy 0.8mm infeed at a time passes to get to depth.  If I had any doubts about this cutter's sharpness, I'd have decreased the passes to 0.5mm at a time:


I then used a slitting saw to saw off the valve-in-making:


The slitting operation left a burr at the end - I broke most of that off with a small pair of electronics pliers, then flat-lapped the surface on some 600 emery to get rid of the rest of the burr.  Next it was mounted in the mill vise again (in the middle of the jaws for those checking  ) There's no parallels or anything; I simply used a finger to feel to get it flush with the vise jaw tops:


The port cut-out is about 3.97 x 4.8 mm - so I used a 3mm center-cutting mill to plunge 0.8mm deep into the workpiece, then milled a pocket 0.1mm under-size on all sides with it.  This simply removed the need to perform multiple cuts with a small mill:


A 1.5mm mill followed - to finish out the corners and take off the 0.1mm left on the sides in the previous operation:


Some tidy-up on emery followed, and this is the result - Top:


Bottom:


In the background of the two previous photos is a strip of 2mm thick brass plate 7mm wide.  A bit of that made up the valve nut - I clamped that up, located the Y center and right-hand edge with the center fined, and then drilled and tapped it M2 for the valve rod:


After scribing the needed width on it, I used a Junior hacksaw to saw it off on the bench vise:


Some filing got it down to size:


After a bit of tidy-up, the nut was done:


On to the eccentric.  I made it from some stainless steel.  I didn't want to saw off a section of the rod to prevent wastage, so it's sticking a bit far out from the chuck.  I just centered it up, turned a short section down to 16mm, drilled 5.9mm and reamed to 6mm:


The lands on my 4 jaw chuck's jaws are about 4mm wide, and the eccentric offset is 1.27mm.  This means I could do the hole without first turning the eccentric bit - if the jaws' landings were narrower, the eccentric's center point would have to be marked out, centered up and turned first, otherwise the hole takes away the eccentric center point.  As it was, I could simply dial in the eccentric offset by using the dial indicator and adjusting two opposing jaws:


After that, turning the eccentric was a no-brainer:


The rod was roughly centered again, and the eccentric parted off.  I was wondering how the resharpened parting tool would handle the stainless - it just went through it like butter:


As a last step, the eccentric was drilled and tapped for an M3 grub screw:


The finished eccentric, and some curls of swarf I picked up off the lathe after parting it off - just for interest:


I started work on the eccentric strap - here a bit of bronze turned down and bored to size for the ring part of the strap:


That was parted off; as you can probably see, I'm deviating a bit from Elmer's construction for the eccentric strap, but all the critical dimensions will be kept as-is:


That was it for my shop session yesterday.  Hopefully a bit more to follow today.

Kind regards, Arnold

[Nicolas]

Another great update

I just noticed that you use your taper turning attachment for your dial indicator. I might add something similar to the back of my lathe to hold the indicator

Nicolas

[arnoldb]

Thanks Nicolas.  Yes - the taper turning attachment comes in very handy - occasionally even for turning a taper  .  All ML7 lathes have a row of mounting holes at the back for mounting the TTA in different locations.  A nice section of angle iron will make a good way to mount magnetic bases from the back.

Not much done today - I just finished the eccentric strap.

First I milled a small groove in the bronze ring I made yesterday - a slightly delicate operation with a 1mm end mill that was then also used to widen the slot to 1.2mm to fit the brass plate I have for the arm:


I then took a strip of the 1.2mm brass plate, filed it to rough dimensions, and silver soldered it to the slot in the ring:


It was given a pickle in some citric acid (I made up a new batch for a change, so it's nice and clean):


After a rough clean-up, I could mark the hole that the valve rod will connect to:


The workpiece was a bit awkward to clamp down for drilling, so I used the tooling plate to clamp it down on with the hole location positioned over one of the holes in the tooling plate:

The hole was drilled and tapped M2.

After sawing off the excess length on the workpiece, I rounded over the end and gave it a final clean-up:


Well, that's as far as I got today; other matters needed attention.  Next up will be the base and bearing blocks...

Kind regards, Arnold