# An experimental engine



## arnoldb (Jan 2, 2011)

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


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## tel (Jan 2, 2011)

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


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## shred (Jan 2, 2011)

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.


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## arnoldb (Jan 3, 2011)

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


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## bearcar1 (Jan 3, 2011)

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


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## njl (Jan 4, 2011)

Hi Arnold, 

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

Nick


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## b.lindsey (Jan 4, 2011)

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


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## arnoldb (Jan 5, 2011)

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


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## arnoldb (Jan 8, 2011)

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


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## ozzie46 (Jan 8, 2011)

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


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## zeeprogrammer (Jan 8, 2011)

arnoldb  said:
			
		

> So nothing much for today, and much less pretty,



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


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## arnoldb (Jan 9, 2011)

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


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## swilliams (Jan 10, 2011)

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


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## bearcar1 (Jan 10, 2011)

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


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## tel (Jan 10, 2011)

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


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## arnoldb (Jan 10, 2011)

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


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## arnoldb (Jan 15, 2011)

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


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## bearcar1 (Jan 15, 2011)

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


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## zeeprogrammer (Jan 15, 2011)

Looking good Arnold.



			
				arnoldb  said:
			
		

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



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


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## arnoldb (Jan 16, 2011)

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


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## Ken I (Jan 16, 2011)

Arnold,
     Re earlier superglue failure. Here's a tip.

All metals oxidise virtually instantaneously - so you are bonded to the "rust" not the bare metal.

Try sanding the surface using the glue as lubricant (fine with epoxies - a bit more problematic with superglue - but doable) this causes the glue to bond directly to the metal surface.

Wipe clean to get rid of debris - do not wipe off glue film.

Do this to both surfaces and proceed as per normal.

To be sure etching primers do the same thing - but if you don't have any to hand .........

Strength is 2 to 5 times better.

Ken


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## arnoldb (Jan 26, 2011)

Thanks for that tip Ken Thm:

This project has been waylaid a bit; I wanted to be much further along but the redesign and personal life interfered.
Re-designing the valve gear layout took quite a bit of time, but I think I'm close enough to continue now.

Today's bit - a start on the frames...

As the loco will be a bit on the narrow side, I want the frames to be fairly heavy to keep the center of gravity as low as possible. I decided on using 3mm thick steel plate for the sides, and will use mild steel for the cross beams as well. The only 3mm plate I have is locked up in a fairly big sheet, and cutting a strip off it was a bit of a challenge. I could have tried man-handling it on the band saw, but that was just asking for a broken blade. Another option was using one of my angle grinders, but I don't like cutting thinnish plate with either of them; it takes a lot of concentration and makes a hell of a noise. Gas is a bit expensive, so I tend not to use my oxy-butane kit for that. So, I settled on the venerable jig saw with a suitable fine HSS blade for cutting thin steel:






Next I sawed of two suitable lengths from the strip and off to the drill press with a rubber-backed sanding pad mounted in it. After a bit of work, most of the rust and crud was gone from the plates:





A bit of clean-up followed on the mill; very carefully over the extended bits with a fine feed:





Once I had both long sides parallel and to width, I squared up one reference edge as well:





Then I drilled holes for the cylinder mountings, axle bushes and valve gear mountings/bushes:





Some holes followed for mounting the cross beams, and I finally split the two sides apart, de-burred and left off for the day:




There's still some more work to do on the frames, but at a later point.

Regards, Arnold


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## arnoldb (Jan 30, 2011)

Some more progress... eventually :big:

Started off with the axle bushes. I'm out of my preferred phosphor bronze in the smaller size, so I used 7mm brass rod to make them. The first one took a bit of time to get the final sizes I needed, but then I just jotted down the cross slide readings and used that for the next 5 - which went quickly. Here I'm on the first one, with the final parting done to just below the 4.9mm diameter that it will be drilled out to:




Then a quick spot with the center drill, and drill out to 4.9mm, and the bush ends up on the drill bit. I find this more convenient to do than to first drill and then part off.

A little while later, I had all 6:




On one, I took the parting too deep... So it left quite a burr, but the 5mm reamer will easily take care of that later.
These were then pressed into the frames together with bearing retainer to make doubly sure they'd stay put, and set aside to cure a bit.

A block of hot-rolled flat bar was cleaned up, and accurately machined to make the frame spacer pieces from:





Some more machining and a little tapping later, I had the two spacers:




I actually made holes in the frames for a third spacer toward the middle, but things seem entirely rigid enough with just the two.

The first real "feel" of the frames coming together:





I then reamed the axle bushes out to 5mm with a hand reamer, running it through both bushes completely to ensure alignment:





Further work on the cylinders will be easier if they are split apart at this point, and I wanted to see how they fit on the outsides of the frames, so I slit them apart:




The bottom cylinder is not getting clamped on the studs; I shoved a T-piece between the studs so the vise could clamp down through it on the valve cover plate.

With the cylinders fit to the frames, I did a quick mock-up to see if things will look OK. The frame is resting on some blocks on the track at about the height it will be once the wheels are fit to the chassis, and the aluminium stock lying on top is approximately the same size and in the same position the boiler will go after getting some cladding added to it:





Some more size comparison with Fred:





Things look about right to me ;D

This boiler would definitely be too big:





Not as much progress as I'd hoped for up to this point, but some is better than none!

Regards, Arnold


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## arnoldb (Feb 1, 2011)

;D Managed to squeeze an hour in the shop after work today.

Skimmed off a bit of hot-rolled bar to 30mm diameter:





I then drilled a 4.5mm hole deep enough into it to allow for 6 wheels and parting space.
Then, with the QC toolbit swung over to the correct angle for the flange, the first wheel rim was turned down to 28mm, and a note taken of the cross slide reading to get the others to exactly the same size. Then I started parting off the first wheel:





The others soon followed - two of them "blind" - i.e. without wheel flanges; these will become the center wheels; I found that it is relatively common in this size of locomotive to do this, as it allows locos to negotiate tighter curves. The six wheel blanks awaiting further machining:





Regards, Arnold


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## arnoldb (Feb 5, 2011)

Today was a bit slow in the shop, and in retrospect things could have gone a lot better had I thought things through a bit more.

Finding a suitable method for mounting the wheels to the shafts proved to be a bit daunting. There's not much space anywhere to fit grub screws, and I couldn't have bits sticking out. As I want to be able to easily disassemble and reassemble things, retaining compounds is not an option either at this point... I settled on using round "keys" to locate the wheels on the axles and countersink screws to retain them; a lot of work initially, but would hopefully pay off in the short to medium term. There's an additional advantage; some machining operations on the wheels will be easier if they are keyed.

The 5mm shafts would have 4.5mm steps turned on them to locate the wheels, and then a 3mm countersink screw used to retain the wheel on the shaft. A bit of 1.5mm wire would serve as the key. Fiddly work :

So first order of the day, start cutting key ways. I centered the rotary table on the mill, mounted the 3 jaw chuck with a wheel blank, dialled in a 2.25mm offset on X and chucked a 1.5mm 2 flute center cutting endmill:





Then just gently milled straight down to take out a half-moon. For the blind wheels, I just spaced them off the face of the chuck with a square toolbit, taking care that I would not run into it with the milling cutter. Here's the result:





In retrospect, I was silly with the following proceedings and should have used a different method that I used later after completing the wheel facings, but for the record...
I chucked a bit of 5mm silver steel in the lathe's collet chuck, and turned it down to 4.5mm diameter for a length of 3.5mm; 0.5mm less than the final wheel thickness. Then moved the collet chuck to the rotary table on the mill. As I'd not changed any settings on the mill, and my chucks screw down pretty accurately on the chuck adapter on the R/T, I could just straight away mill a half moon in the arbour as well:




(had to keep my hand behind to take the photo; the camera wanted to focus everywhere except on the work :

A quick test with a wheel and a 1.5mm drill shank - and a very satisfactory fit:





Back on the lathe with the collet chuck, center drilled the arbour, then drilled 2.5mm and threaded 3mm. Then I cracked the collet closer loose and pushed the arbour back into it so that a wheel mounted on it would be clamped against the chuck face by tightening the screw. I mounted the first wheel, with a short bit of 1.5mm wire shoved into the "key" bits, and a bit of offcut with a 3mm hole hole was used with a 3mm screw to clamp the first wheel down. I locked the carriage, and then faced the wheel to size using the topslide for infeed - taking note of the topslide and crosslide readings at final size:





For the following wheels, I just machined to the dial readings and things went well, except that it was difficult to get the wheels off the arbour after machining. I used my pocket knife to wedge them away from the face of the collet chuck :. On the fourth wheel disaster struck; I overshot the cross feed grossly, the tool dug in and sheared the holding screw away; I heard it landing somewhere behind me in the shop.... Fortunately the wheel stay put and I managed to stop things before it went flying. Some choice, highly reserved and rarely used words in an astounding variety of international and native languages followed...

Recovery was a bit painstaking; there was just enough of a stub left of the screw to use a needle file to file a groove in it without disturbing the entire setup. I managed to get a screwdriver into the groove, and a bit of a turn; then more groove filing, and another bit of a turn. This went on for a bit, then I got the junior hacksaw to the groove with enough of a slot to unscrew the stub. Sorry; no photos; I was a bit peeved at that point :big:

With the stub out, I took a break and had a bit to eat and a good strong cup of coffee. Always make life seem better 
Then I finished the rest of the wheels in the same way, though a bit less energetically. I must still have been a bit peeved off though; I didn't take any photos of using my tooling plate for the first time. To get rid of the bosses left on the wheels, and to get the correct countersinks in the hubs, I used the tooling plate with bits 'n bobs and disassembled toolmaker's clamps to clamp down the wheels to countersink the hubs. I'll do a mock-up of the setup tomorrow if I remember.

I ended up with this motley crew for all that effort; hardly what I have come to expect from myself, but will do for the experimental engine for now:




The wheel at the top left has a gouge around the hub; that's the one I had the "fun" with.

Now came part of the "in retrospect" moment :doh: - to drill for the crank pins on the wheels, I would need a new arbour. The one I made earlier would not work, as I could not drill the holes for the crank pins using it as-is, as I'd drill into my collet chuck or collet. Definite No-No. The scars you see on the lathe's 3-jaw was done in years-past, not by me, nor by its previous owner (as far as I'm aware). There are no machine marks on any of my chucks or vises that I put there - I take great care not to make any. The existing arbour would flex too much under off-center drilling pressure, so I made a new one from some aluminium that would offset the wheel; used the 3-jaw for that so that I could transfer between lathe and mill without re-chucking. I milled the key half-moon in it on the mill like before, but then drilled it out deeper, so I could shove a bit of wire in there and leave it in place. Much easier than having to fit individually for each wheel. A later photo will show more detail of the new arbour (there's a linky clicky thingy on the photo to load a bigger one)

With the R/T on the mill still set up, I just added the additional offset to get the 7mm from center I need (for a 14mm stroke). The wheels were divided into a left and right hand set; 2 flanged and one blind in each. For the first set I turned the RT so that the "key" would be at 0 degrees, and drilled the crank holes (2.5mm to thread M3) - taking care to tighten down the wheels against the round key in the same (in this case clockwise) direction to eliminate any radial play:




For the other set of wheels, I cranked the R/T around to 90 degrees, and followed the same procedure as for the first set of wheels. This will hopefully make life easier; the wheels will already be properly "quartered" if I cut the key ways in the axle shafts in line; which should be easy to do.

Then I started fiddling with more 5mm silver steel for the axles - roughly cut to length:





My 5mm ER collet for the lathe is out by about 0.02mm, and would make for wobbly wheels if I turned the shafts directly in it. Seeing as I already had a bit of aluminium (the last arbour) chucked in the 3-jaw with a near-accurate centered hole (except for the threads) - and as I would need a way to fairly accurately get the axles to the same size, I decided to just use it to make a once-off jig to hold the shafts for machining and to set their length. So I ended up pre-drilling holes to thread for grub screws to hold the axle. I don't know if what I did next is a good idea - seemed so at the time, and I can't think of any reason not to... I lightly clamped the lathe chuck in the mill vise and drilled the holes:



The above photo has the linky clicky thingy I mentioned earlier.

Back on the lathe with the chuck, I used somewhat unconventional means to tap the M3 holes in the ex-arbour and now jig; none of my tapping handles could reach, so I used and oldish and seldom-used lathe chuck to do it - being careful not to put any lateral loads on the taps:




Only the front two holes were tapped; the third is for inserting a bit of rod to set the depth of the shafts later on.

Then I drilled the jig 4.9mm , and reamed it out to 5mm to take the shafts. Then I inserted the shafts, each in turn, and turned a 4.5mm step on it 3mm long, center drilled, drilled 2.5mm, tapped M3 and countersunk the end - this is the first one done:





I only did one side of each shaft today; time caught up and I had to call it a day. I ended up with this lot:





And a single-side assembly on the frames:





Still quite a bit of work left on the axles; they need to be machined to length, and the key ways cut in them.

After typing up this lot, I can think of alternates to the way I have done things here which would be much easier... I think I took the "long way 'round"  :big: - but all good fun, even with the frustrating bits in between  ;D

Regards, Arnold


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## zeeprogrammer (Feb 6, 2011)

Very interesting post Arnold.
The round keyway was a learning for me.
I'm sorry you got peeved...sorrier still there was no audio recording. :big:


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## arnoldb (Feb 6, 2011)

Thanks Carl.  :big: - I'm glad there was no audio recording; would have been boring... The "peep" sound in recordings seems to sound the same in all languages and just hurt one's ears  - and it does not help to have a parrot that can imitate it VERY well - I dare not leave the TV on on a channel that might contain peeps :-X
The round keyways are not necessarily a good option; rectangular ones work better and are more accurate; I just did it for the sake of convenience. Once I get the engine built and all issues sorted out, and if it would be a good runner, then I'll rebuild it completely from the ground up, and then tiny details like this will be properly addressed. What I'm flogging together now, and the picture of the real one in my head are two totally different-looking things; this one must just be mechanically sound sound to see if it will run.

Today's bit...

I used the stop hole in the arbour with a pin shoved in to set the depth for each axle, and then locked and fed the carriage from the feed screw hand wheel. When the first axle was to length, I took a note of the reading on the feed screw hand wheel. The other axles was then finished to this same reading to get the lengths correct:




Obviously, the pin was removed from the hole after the axle was tightened down with the set screws, and before switching on the lathe.

More drilling and tapping and countersinking followed on the end of each axle as well. Then it was off to the mill to mill the key slots; 1.5mm wide and 0.75mm deep. Both sides of each axle was done in one setting to keep the slots in line:





Then cleaned off the burrs from milling the slots (that old 1.5mm cutter seems to have had it now; I should have used a new one!) and cut 6 countersink M3 screws to length to use on the axles & wheels:





Well, what do you know; they actually fit the track with just the right amount of side-play ;D:





Assembled on the frames, and a shot from above on a 27" curve (the sharpest for O gauge - and meaning a curve taken from a circle which would have a diameter of 27") - and the reason for the blind drivers in the middle; as you can see, they are way off the track, yet the other wheels still follows the curve quite easily if pushed along:





Now comes the fun bits; the drive train and valve gear. I'm really looking forward to that!

Regards, Arnold


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## arnoldb (Feb 12, 2011)

Earlier this week, I finished tapping the crank holes in the wheels. Just clamped all the wheels on the tooling plate with the holes to be tapped located over tooling holes and manually tapped all the 3mm holes:





This afternoon I started off with two strips sawn from 2mm thick brass plate:





These were then cleaned fairly well on one side each, and a thin strip of soft solder placed on one:




The other was placed on top, and I just used a plumber's torch to heat them up and solder them together.

The strips were then cleaned up and milled to 6mm width and a clean reference end. I marked for a center hole next to the reference end, and didn't bother to mark the rest; I'd do them by the dials. The workpiece was clamped to the tooling plate on top of a strip of aluminium plate (got that from an old QUICK-80 tape of which I now have a whole stack) Then I centered the mill on the reference:





And then drilled three 3.2mm holes in it at the same spacing as the axles. I only needed 3mm holes, but made the holes slightly larger to allow for slight variations in wheel positioning, as well as to allow a bit of pivot in the holes once mounted, as the wheels can move from side-to-side by about 0.8mm:





That would have been all that was needed for the experimental engine, but I got a bee in my bonnet and decided to try and be a bit flashy for a change, so I tried out my new 4mm ball nose mill - just 0.6mm deep into the brass:





Just couldn't leave things at that, so I took away a bit on the sides as well:





And ended up with this lot:





Just had to try and keep my filing skills in shape, so filed the pointy bits approximately round, and then re-heated with the blow torch to separate the two pieces. Then spent a couple of minutes to remove the solder from the back sides with some emery paper. Net result:




Can anybody spot the booboo I made ?

At least the booboo is visual and not mechanical; the rods fits nicely on the wheels, and there is no sticky bits when rolling along the rail. I still need to make up some proper mounting screws and spacers though:





Regards, Arnold


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## lazylathe (Feb 12, 2011)

Excellent build thread Arnold!!
Really enjoying reading and following your progress here!

Does your Myford have the taper turning attachment?
I see something attached to the back side that is not on mine.

Andrew


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## bearcar1 (Feb 12, 2011)

Hello Arnold, always a pleasure it is to follow your work, this one is no exception to that rule. Do you have plans for a tender for your loco? One of the reasons I ask is it would seem the moment of the frame rails will be quite acute and wonder how that will effect any coupling issues down the line (oh, no pun intended, sorry :hDe

regards

BC1
Jim


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## Ken I (Feb 13, 2011)

Arnold,
     Liked the soft solder trick - make mental note.

At the begining of this thread you said you are not really working to plans. Seriously - are you doing all this out of your head or sketching as you go along ??

Ken


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## arnoldb (Feb 13, 2011)

Thank you Andrew . Yes, it's a taper turning attachment. It doesn't get used too often though; normally it's just a swarf trap and a handy-dandy place to mount my magnetic base for the dial indicator or DTI when clocking things up in the 4-jaw chuck. On the rare occasion where it's needed though, its a good bit of kit to have, and I'm fortunate my lathe came with it. From what I've seen, they cost silly prices to buy, and if I didn't have it, I'd rather spend the silly price on a quick-change gearbox 

Jim my friend, thank you! Hmm... The loco is supposed to get a tender as I want water and fuel in it, and you raised a very valid point! - On tight turns coupling will be an issue, so I have to think a bit. The frames are overly long toward the back, so I can shorten them, but then I might have balancing issues; not too difficult to sort out though.  Just like real life - I never seem to get a good angle on the coupling thing; prospects for St. Valentine's day tomorrow are a bit slim :big:

Thanks Ken. I have simulations of the valve train, but no real drawings - except for the measurements needed for it. So I'm mostly going by what I have in my head, with some rough sketches where I need them. Once things look good to go, I'll take the final dimensions and draw it up in CAD properly, so that I can build a good one.

Not much done on the loco today...

Some 5mm hex brass, turned down to 3mm and threaded M3 for a bit:





After parting off and repeating, I had the outboard rod bolts - with a dud that I parted off slightly too short (the head is too thin) as I was doing things by eyeball rather than properly measuring:





Having made those, I was hit by "designer's block" - and I wasn't in particular interested in small work today, so I made up some clamps for my tooling plate - I'll post that in my tooling thread.

Regards, Arnold


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## mklotz (Feb 13, 2011)

> Just like real life - I never seem to get a good angle on the coupling thing; prospects for St. Valentine's day tomorrow are a bit slim.



Chuckle, chuckle.


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