An experimental engine

I've hinted in a couple of posts that I'm busy on some design work of my own.

My long-term goal is an O gauge 060 locomotive with functional tender that's fairly easy and cheap to build and a good no-nonsense runner. I've learned many valuable lessons from building and running little Fred, and while I love the little loco, it has quite a couple of flaws - which I'm not going to attempt to correct, as I like the loco as it is - it carries many fond memories!

While working on my design, I've gained a VERY healthy respect for designers who draw up a model and then proceed to build it - it is a huge challenge!
So far I have spent a lot of time on research - from pointed questions asked in the Boilers section on HMEM to reading and fully trying to understand each bit of information I could lay my hands on relating to boiler design, how steam works in small models, and studying different valve gears to figure out how they work.
I'm slow with CAD - which makes matters worse, so I've resorted to just hand-drawing parts when I've had a bit of inspiration. And material selection is a bit of a problem; I have to work with what I have available. O gauge is fairly small, bringing some additional challenges...

I've reached a point where it would be easier to actually make some bits than try and run them through my mind. Thus, this thread will not be along the lines of a quick and deliberate build to established plans, but a changing work most likely with a LOT of failed bits and re-designs to reach an end goal. I'll share all the trials and tribulations along the way; maybe there would be some useful information for someone in there. And if anything's good for a chuckle, that's also fine by me - building boo-boos is more fun than no machining at all

Experimentation first - I need to see if the idea I have for valve gear will work. First prize would be full Walschaerts gear - but I have a simplified valve gear in reserve... For a start I need the basics of an engine - a working cylinder, a way to mount it, simulate a loco drive train and then "play" with the valve gear.
First up, a cylinder along the lines I have in mind - outside admission D-Valve, 10mm bore, 14mm stroke, 5mm thick piston - a rough C-o-C of the plan, and a block of aluminium to make it from:


The block's a bit big; it's 1" square stock about 43mm long. My design calls for a cylinder block 20mm long, 16mm high and 18mm wide. So I milled it down to 20mm in thickness first:

Really hogged it to 20.5 mm hence the big chips, then took the last 0.5mm off slowly to get a better surface finish.

As the block had more than enough material left on it to also make the steam chest from, I slit off the top to make the steam chest from and leave the block 16mm high, rather than waste all that aluminium by turning it into chips:


At this point one of the realities of my endeavour kicked in; this cylinder would be quite small... Not nearly as small as Elmer's Tiny, but still, it would present some workholding issues. In fact, there was enough material on that aluminium block to make two cylinders from - while making machining easier..., So I started making two cylinders from it. I marked it out for two, then drilled the first cylinder; a 6mm through hole (just convenient to fit the mill's collet chuck), then 9.8mm, and finally reamed it to 10mm. The reamer is actually a hand reamer that I chucked in the mill - slowest speed and lots of methylated spirits which I use for cutting fluid on aluminium, and it makes for quite a presentable bore:

The cylinder bore on the right-hand side received the same treatment

With two cylinders-in-making needing port holes drilled, it just seemed logical to have a think around what's needed in terms of valve chests, valve plates and covers. Cue some small bits of 1mm thick brass:


I couldn't be bothered to set up to mill the plates to size, so a quick bit of filing was in order. Good for some exercise to work off the effects of Christmas and New Year :


I thought I'd be clever and stick the bits together with some cheap CA glue (Superglue/Crazy Glue):


I did say CHEAP CA glue; it didn't work, and while drilling the first 1.6mm bolt hole, it started coming apart, so I fell back to some of my "friends" for keeping things together; the much underestimated toolmaker's clamp:

The bolt hole is 1.6mm for threading M2 - most of the holes will need drilling out to 2mm clearance later on.

While the going was good, I kept the valve plate fixed to the cylinder block, and laid out one side of the valve holes:

The other side was done simply; clamp up on the side that was done, and remove the clamp on the side to do. Have I mentioned how convenient the height gauge is for jobs like this ? - I can't believe I took so long to make one!

Some drilling in the mill followed. I didn't bother to center punch any of the holes (In fact, I've stopped center punching any hole spots for the last couple of my builds!) I just located the first (top left hand) drilling position as accurately as I could, zeroed, the dials on the mill, and co-ordinate drilled the rest off readings of the handwheels - keeping backlash in mind:

The center drill I used (actually a spotting drill followed by a normal drill would be better - but I don't have spotting drills) has a convenient 1mm tip - but it does make a larger hole - it ends up at about 1.1mm - but OK for the valve plate and spotting through to the engine block.

Some milling followed. Seeing as I'd done things by setting the mill dials, this was quite easy. My smallest milling slot cutter is 1.5mm - this is bigger than the 1mm holes I need. By using the valve plate with pretty near correct sized holes, I could slightly offset the bigger cutter to mill the steam and exhaust ports in the block. The steam ports are offset 0.25mm to the outsides, and the exhaust port smack bang in the middle. This leaves a 0.75mm wall between steam ports and exhaust on the block; a bit tight, but it should do:


The ports look a bit crappy in the photo, as there's a lot of burrs. Some flat-lapping removed those, and things are looking up

That was it for today's work; not a lot to show, but some chips to start off the new year ;D:


Regards, Arnold

I'm on board Arnold - just as long as no hippos are harmed the the process!

Looks like a lot of fun. From reading LBSC's Shop Shed and Road, I think he recommends Baker valve gear for that size, but I might have to go re-read that.

Thanks Tel - No hippos, honestly! - they're NBG for using as gang-planks as they scare two kinds of running out of me - one with legs & shoes...

Shred, Thanks I wish I had that book... - one more for the list. A quick look at the Baker gear, and it seems just as involved to make as the rest :big:

Project will be a bit slow for a while... I have some tooling to make first and my day job will compete with shop time

Regards, Arnold

Arnold, a joyous new year to you! It is always delightful to witness your WsIP, this example is yet another to sit back and enjoy as it unfolds. Thanks once again for sharing with us.

BC1
Jim

Hi Arnold,

happy new year from me as well, I'll second BC1's comments, got my comfy chair all ready.

Nick

Wow Arnold...lots of progress already. An O gauge loco with reversing gear...I can only imagine all the little parts that will be needed. I will be anxiously following along.

Bill

Jim, Nick, Bill, thank you; and may you all have a good New Year as well!

Don't get too comfy; you'll fall asleep, as things will be slow on this one

Bill, the little parts don't bother me too much, but fastening things together will be a challenge... I might end up using small rivets...

Kind regards, Arnold

Well, no tooling was made, but a little progress on the project was

First things first though... My 40 year old Myford was still running with its original motor V-belt - it needed replacing badly:

: I forgot to convert its size to "Metric" before I went shopping; just jotted down the imperial size and didn't think to take along the original. First thing the salesman told me is "We don't sell Imperial v-belts" : So I borrowed his calculator, and got him the "metric" size - well, closest over and under sizes from his stock list & bought both as I couldn't remember if the Myford was closer to its short or long adjustment for the belt. The longer one works perfectly (even though a certain salesman is convinced a metric V-belt cant work on imperial machinery). The old girl is running as smooth as I ever heard her - it was time for this belt change and I think I can expect better surface finishes and easier parting off now ;D

On to the project, and first off, I milled 1.5mm wide by 1.5mm deep port holes at the top of the cylinder bores to start the steam passages from:


...tool gloat... - As the port passages needed to be drilled at an angle to meet up with the slots on top of the cylinder, I calculated the angles - 10.8degrees, and brought out my "Christmas Present" - a precision protractor I found in a 2'nd hand shop just before Christmas:

Mitutoyo 187-901 protractor set in mint condition for US$60 - sometimes I get lucky!

I used the protractor to set the valve block at the calculated 10.8 degrees off vertical:


Then used a 1mm center drill to spot a starting hole to drill the steam passage in the milled out bit on the cylinder:


And drilled the steam passage with a 1.3mm drill - checking from the side for break-through into the steam port on the top of the block:

: These macro photos can really light up the minutest imperfections and scratches on a surface!

The steam passages came out OK - with no additional break-through into the cylinder bores, and closely bottoming out in the steam ports on the top of the block:

Looks like a dog's breakfast on close-up - I need to improve my skills.

One problem I found with my design so far is for the exhaust ports. I need to be able to pipe the exhaust from the cylinder blocks back to the boiler smoke box later on to help create draft there. On most cylinder designs I've seen so far, the exhaust is in-line with the exhaust port, but I didn't leave enough room, so another angled hole was needed from the port face to where I could fit the exhaust connection pipe. I decided that I'm not going with a threaded exhaust connection; a Loctite fit would be fine, as the exhaust side of the engine won't be under pressure, so I drilled a 3.2mm hole 4mm deep into the block from the side to receive the available copper piping I have:


Then I calculated and set the angle to drill the passage hole through from the port face to the exhaust hole. Made a horrible boo-boo on the first one by drilling the angled passage hole all the way right through to the outside of the cylinder block :wall: :

Well, Warts & All is what you get :big:

The second one went better; I remembered to use a bit of rod shoved into the hole and held there to "feel" for break-through into the exhaust hole:

When the drill breaks through into the hole, the bit of rod wiggles.

Photographing down holes is a problem in macro mode... I was hoping to show how the port passage hole was nicely centered in the exhaust hole - if you squint, have a vivid imagination, and take a couple of grains of salt along with that, you might be able to make it out ::


On to try and recover the bad port hole. I first counter bored across both the holes with a 4mm center cutting end mill. A 5mm would have been ideal, but I don't have one, and a 6mm (which I have) is too big, as it would likely break through into the cylinder bore on the one side. A drill bit would have wandered so I couldn't drill it out:

And a oh: moment while typing this up... I could have just counter bored it like I did and then opened up the hole with a 5mm drill afterwards : - too late now!

I then turned down and parted off some aluminium rod (salvaged from an old TV antenna directors :big for a press fit into the counter bored hole:

I left the parting pip on - it's useful while handling small bits...

Then with a lavish coating of loctite pressed the slug into the hole with the mill vise. The pip squashed a bit flat in the process :big::


After cleaning off the excess loctite and material from the pressed-in bit, things looked like this:

There's a small artifact left on both sides from the old holes - that's why I would have preferred a bigger hole initially to mend my erroneous ways...

I finished today's shop time by re-drilling the exhaust hole at 3.2mm to depth through the repaired section:


So nothing much for today, and much less pretty, but it _IS_ experimental after all

Regards, Arnold

Arnold; I've got my easy chair and popcorn at the ready. This is going to be a very good thread.

Had some warts of my own yesterday. Measured several times and still cut off to short. TWICE!!! :wall: :wall: :wall: :wall: :wall:


Ron

arnoldb said:

So nothing much for today, and much less pretty,

Click to expand...

I hadn't figured you for a liar. ;D
Seems like a lot to me...and it is pretty.

Thanks Ron - those are the kind of days I give up & get a beer - or distilled malt - and watch TV - One booboo is OK but 2 means its not a shop day :big:

Thanks Carl :big: - I can tell you with a very straight poker face that I never lie :big:

Today's bit; I had shortened shop time due to a personal commitment that paid off handsomely in a bottle of good single malt ;D

First job was to drill the mounting holes on the sides of the cylinder block - 2.5mm for tapping M3 later:


I drilled out all the mounting holes in the cover plate, valve plate and valve chest stock to 2.1mm by clamping the lot together:


Then on to milling out the valve chests - I got rid of a lot of the excess material by drilling two 6mm holes in each:


And then started milling to the scribed lines with a 4mm end mill. Apologies for the out of focus photo:

The other chest received the same treatment. I think I'm due for a new 4mm end mill though - the flutes on this one leaves two "lines" on the sides.

Some may have by this point wondered what I'm going to do about the valve guides and packing glands... I had decided on doing things a little differently - that's what experimentation is all about - and make up longish press-fit guide & gland combinations, that can be pressed into holes in the valve chest. As these would be subject to steam pressure and heat eventually, I opted to go for a design where they would be pressed in from the inside of the valve chest with thin flanges to prevent them going out should heat and pressure loosen things. Seeing the things might be better...

So on to the lathe for a change. Material for the valve guide combinations is 6mm stainless steel rod, which I turned down to 4.01mm for a length of 8mm, threaded the end M4 for a length of 3mm using the tailstock die holder and then drilled and reamed out to 2mm in the center. Then I started parting it off leaving a 6mm diameter and 0.2mm thick "flange" on the end:


Then I drilled and reamed 4mm holes in the side of the valve chest:


Pressing the guides in from the inside was a bit daunting. The bits were coated with some loctite, and then I resorted to using a spanner and hammer to bash them home using the big vise as a guide. Brute force, and I paid the price by missing a hammer blow - no guesses where that one landed :-[ :

I should have made a proper pressing jig; would have made for a much better outcome :wall:

Surprise, surprise... Things are offset : - the valve ports are offset by 1mm towards the inside, which will become the outside of the cylinders :-\ :

I'll see how things pan out from here; I'm thinking it will be usable as-is, otherwise I'll have to make a new valve plate. Now I'm glad I made the valve plate separate from the cylinder blocks.

Time to sample that malt ;D

Regards, Arnold

Nice work Arnold. I'm glad you decided to slow down from your usual pace, I'm still struggling to keep abreast at this speed

Cheers
Steve

I agree Steve, so very much accomplished in such a short period of time makes my head spin :toilet: ;D

Arnold, it really is a pleasure watching your progress. The 'mistakes' along the way and how they are overcome makes the journey that much more interesting for me. On your valve plate, were the inboard row of holes supposed to have been towards the outer edge instead? Is that where the error was? Could you not attempt to plug that row and re-drill a new row. A LOT of extra fuss and ado but at least the brass bit will have been salvaged. Tally HO!!!

BC1
Jim

That single malt could be deleterious to your health - better send it to me for safe-keeping!

Steve, Jim - thanks for checking in

:big: Maybe I must spread my progress posts through the week - I'm only getting in the shop on weekends right now, so I try to make it count when I do get in there This coming weekend might be a bummer, as work life will interfere - in a good way - as it's the go-live of an IT project that's been 5 years in development next Monday.

Jim, the middle row of holes should have lined up axially with the valve stem; instead the "no mans land" is lined up. I'll have a go at making the valves offset toward the error; not ideal, but should work. If the bottom of the valve surface partly covers the row of holes toward the middle of the "cylinder block" as it is now, it shouldn't be a biggy either. Like I said, experimentation is the aim of the game here. Maybe I don't even need 3 rows of valve holes. Its just what's always shown and used so maybe a bit of a diversion from the "commonly accepted and used method" is in order...

:big: Tel, sorry mate I can't afford the shipping; besides Aussie customs would nick it as the seal's been broken. Cheaper to pay the local quack to look after my health... Poor bugger; he annually complains that I'm too healthy and he's not making money from me; could be due to the fact that single malts keeps one healthy

Kind regards, Arnold

My IT project's going well at work, so I'll have a bit of time for the shop this weekend ;D

Stole a couple of hours in the shop today, and got down to some bits.
First off, grabbed the M2 taps, and sat down and tapped all the holes on the top of the cylinder using my crude tapping guide and handle. It looks like one piece in the photo, but actually I set the tap depth in the top "handle" so that it will bottom out the handle on the guide at the correct depth:

: I really need to get around to making a tapping stand...

The mounting holes needed to be tapped M3 - but as they are pretty shallow and I want to get maximum depth of thread, I had a bit of a problem; one that seems quite common. My M3 "final" tap; the last one of the set of 3; has a sharp point:


A quick step to the bench grinder,and with the excess ground off to leave just three threads with taper for engagement in the hole:

Most bolts I've seen will get well down to final depth of thread in a hole tapped with a tap like this; and one could always file that slight taper at the very end of the bolt to go down into a hole completely.

Tapping down to the hole end; on aluminium I just use the second and last taps, and to the top left, you can see my "tapping fluid" for aluminium; ordinary methylated spirits:

And I'm way too lazy to use a tapping guide for M3 - I just free-hand it...

When I looked in my stock for M2 threaded rod, I was all out : - so I ended up making some from 2mm bronze brazing rod, which is nice and tough to use for studding on lighter-duty applications. I just start it off clamped in the collet chuck and with the tailstock die holder, and a couple of manual turns by hand to make sure the thread is properly engaged. Then I power up the lathe on a low speed (on my Myford, surprisingly, lowest non-back gear speed is fine) and hold on to the die holder and let it run through. It does need quite a lot of tapping fluid to cool things down and lubricate the die, and my left hand is never far away from the lathe clutch in case something goes wrong:


I made up four lengths of rod, and threaded some M2 nuts on - to be used in the next step:

After I took this photo, I ground the excess sharpish points off the rods using the bench grinder; not ideal use of it, but it's very little metal to remove.

Having four separate pieces of threaded rod makes life easier for the next step; a dab of loctite on the tip of each rod, and screw it into the cylinder block until it is finger tight. Then a light additional twist using pliers on the non-threaded bit of each rod, and they tighten up nicely into the block:


A coffee break later - to allow the loctite to cure a bit, and on to the next step. All the nuts are screwed out to a height where their top end allows adequate space for the valve plate, steam chest, steam chest cover, slightly thicker nuts, and a little extra in case some packing is needed and an allowance for clean-up. A whole mouthfull; but rather too long than too short at this point. I also dug up my favourite sharp electronics side cutter:


The side cutter trims off the rod quite well, but still deforms the tops and hence threads at the tops slightly:

That is the main reason why I added the nuts in the first place... Once the nuts are unscrewed, they clean up any thread deformations, allowing nuts to be easily screwed back on again later. : This was REALLY taking the long way around to handing out a handy tip :big:

With the cut ends of the threaded rod cleaned up a bit on the bench grinder again, it was easy to screw on the nuts again; hence ensuring that the rods would screw into the block without problems, and the second set of studs was started, and later finished exactly the same as the first lot:


End of work today; the whole lot assembled and some rods shoved in the valve holes:


I took that lot inside together with the bit of copper pipe that will most likely become the boiler, and compared sizes against Fred the loco:


It's nice to start getting a visual comparison and while the previous two photos don't mean too much, it does start to give me an idea of what's needed from the frames, which will be up next. Some Thinking is required ;D

Regards, Arnold

Ahhh. It is good to see Fred once again there Arnold, as well as some of our other friends from the past and present. I'm enjoying your progress on your locomotive and also can picture you sitting at your assembly station making chug chug sounds, all the while holding your newly made pieces up to that piece of copper tube. :big: :big: Don't worry about it much, your secret is safe with me :

BC1
Jim

Looking good Arnold.

arnoldb said:

I really need to get around to making a tapping stand...

Click to expand...

Thanks for the warning...er...heads up. You'll no doubt have many people looking in on that project.

Thanks Jim ;D - I'm a bit loco, and I won't even hide the fact; so there's no secret to keep :big:

Carl, thanks - I'll be boring everybody with that tapping stand sooner rather than later - just need to find - or even worse, purchase - some bits ;D

Well, there's no update for today... Yesterday evening when I started drawing up the frames I realised that some of the valve-gear components and the front wheel wanted to occupy the same space which is a physical near-impossibility, so today I spent re-designing the entire valve-gear and running simulations to get acceptable and near equal cut-off's for both forward and reverse gear settings, with measurements that actually make sense. I'm getting more and more respect for the engineers at the turn of the last century!
I think I'll spend some time drawing up the frame and gear parts in CAD first - which might take a while...

Regards, Arnold