Garden Railway Forum

Great stuff!

The technical stuff's beyond me, but it looks fantastic, loving how the sun catches the steam and reflects on the brasswork...

Cheers,

Andrew.

The sun glare was purely accidental, however, when I went back to watch the videos I thought they were quite atmospheric.

I think I will produce a narrated video of how the locomotive works as it would take me hours to annotate various pictures of all the working parts.

Is that cheating, what do you think?

Voice is best Tom. I'd love to hear your voice

I'd certainly find it instructive - for someone who's spent his entire life fascinated by steam locomotives, I really know very little about how they work!

If you can find the time to do it then I'll definitely be watching...

Thanks,

Andrew

I have not forgotten about the narrated video idea, however, I am still having to work during lockdown so I need to find time to script and produce it.

I while back I fitted stainless steel mesh inside the smokebox to stop any hot ashes blowing out the chimney which could set fire to dry grass or hit members of the public while running on the club track.

It was only until I did my last steam test with the newly fitted injector that I realised I could no longer access the exhaust nozzle to squirt oil down into the cylinders and push the engine backwards after a run (cylinders are made of cast iron, if left with condensate inside them the pistons are likely to rust solid - very bad).

If you look at photos of Kerr Stuart Wren class locos some of them have a single bolt located in centre of the steam chest covers. Not sure what function these perform on the Wrens but if I could fit bolts to the steam chest covers on my loco it would give me a way of getting oil into the cylinders directly.

I decided on 4BA brass hex bolts as the steel steam chest cover nuts are 4BA so size wise the hex bolts look alright to me (the brass 4BA nut in the picture shows the rough position of where I wanted the hex bolt to be located on each cylinder):


I have never tapped a hole before and given the importance of not making a hash of this I thought I should practice on some scrap steel. I had a raid through my drill bits box and found a 4BA tap and 3mm drill bit (you can Google what size drill bits you need to use for BA thread tapping):


I use to live next door to a retired engineer (sadly he passed away) and he would often give me bits and pieces that at the time I had no idea what to do with but I am grateful now that he did as the brass hex bolts were also from a collection of nuts and bolts he passed on.

I bought this pillar drill years ago and it has not had much use railway wise although it has come in handy for DIY projects:

https://gardenrails.org/viewtopic.php?f ... 1&start=15

However, it would be ideal to drill and tap the holes I needed!

Here is my practice piece:


The pillar drill was second hand and I would not use it for anything that required bang on accuracy, however, it has not done a bad job. When I tapped the hole I did this by fitting the tap in the pillar drill and then rotating the chuck by hand slowly using some oil.

Filled with confidence now that I had popped my tapping cherry it was on to the steam chest covers!

tom_tom_go wrote: ↑Thu Apr 16, 2020 9:19 pm

I use to live next door to a retired engineer (sadly he passed away) and he would often give me bits and pieces that at the time I had no idea what to do with but I am grateful now that he did as the brass hex bolts were also from a collection of nuts and bolts he passed on.

My late friend Colin was just the same, except that he wasn't a retired engineer, he was an ex-salesman, and he could get anyone to take anything off his hands! Over the course of thirty years he handed me boxes of this and jam jars of that, often with a glint in his eye and the words "this stuff's like gold dust" on his lips. It often took me years, if not decades, to work out quite why the bits and bobs in question were so valuable, and I've got quite a lot of stuff that's still waiting to come into its own, but he was almost invariably right, eventually. And, every time I find a use for some of it, Colin's phrase about gold dust comes to mind all over again...

Looking forward to the video in due course Tom. I'm working from home too, but my employer very generously gave us the rest of this week off in addition to the Monday and |Tuesday that we normally get. I've done lots of DIY for two days, hoping to get down to some train fun tomorrow.

Cheers,

Andrew.

Tom, taps come as a set of three (or did when I was an apprentice) taper, second and plug, the taper for starting the thread, for through holes next use the second, and if a blind hole follow up with the plug. Threading steel need lubrication, any is better than nothing, and a final hint is one - one and half turns, then turn in reverse for half a turn (this breaks the cut swarf from the thread). This should give you a smooth finish to your thread, good luck.

Good on you Tom, I haven't tapped cast iron

I’m intrigued by this thread, started building a sweet pea years ago when I was a member of a model engineering club, only got as far as the frames but this is giving me ideas...

Garethh wrote: ↑Thu Apr 30, 2020 8:49 am I’m intrigued by this thread, started building a sweet pea years ago when I was a member of a model engineering club, only got as far as the frames but this is giving me ideas...

Check out this guy on YouTube, he is building one at the moment using bits he has in his workshop:

https://www.youtube.com/channel/UCe6dCz ... nzH-LpRMZA

That’s an interesting watch, need to figure out if I can make enough space in my shed before I get any more ideas unfortunately!

Here are the valve chest covers tapped with 4BA holes and fitted with brass washers and hex bolts (tapping a hole in cast iron is much easier, no swarf is produced just a powder like iron filings):


I liked the look of the brass washers to mimic the look of flanged bolts, however, they leaked slightly when I tested the loco on air with oil poured around the bolts to spot bubbles. I also tried annealed copper washers but I still had leaks.

When I looked at the threads on the hex bolts I saw that they were not fully threaded up to base of the hex. Fortunately, thanks to my late neighbour I found a 4BA die he had given me and was able to thread the bolts fully so I could tighten them down against the surface of the cylinder cover (I couldn't do this before which is why I had to use washers). Another air test was performed, however, one of the bolts still leaked slightly and I had to over tighten the hex bolts which concerned me as I did not want to snap a bolt inside either cover!

My engineering friend suggested that to achieve a good seal between the bolt and the surface of the cover I would need to 'spot face' them as the cast iron finish of the covers is pitted.

As I don't have a milling machine where you could use a mill cutter bit to face the holes I needed a bit that I could fit to the my pillar drill that would not wander all over the place (this is what I have learned is called 'chatter') when I applied pressure. I found a second hand 4BA counterbore bit with a stub online so that it would could fit inside the threaded hole and centralise the bit:


Unfortunately, when it arrived it was not 4BA sized at all so it did not fit the threaded hole. The seller measured the others he had in stock and agreed they were incorrectly sized so I got a refund but I was back to square one with what to do.

Despite not having a milling machine I decided that I had no choice now but to order a set of HSS end mill cutters and give them a go.

Before trying any of the mill bits on my covers I had a go on some scrap steel, however, the chatter was really bad and the bit regularly wandered off target as can be seen in the below picture (last attempt was not too bad though):


Now steel is harder than cast iron so it was a big ask of my little pillar drill to be able to do this accurately so I moved on to the covers. However, this time I lined up the tapped hole in the cover using a 3mm drill bit and then removed this and fitted the mill bit so it was lined up centrally. I also turned the chuck by hand so I could control the mill bit when it wandered off target.

Eventually, I ended up with a spotted hole!


Not as neat as I would of liked, however, you cannot see the surface finish once the hex bolts are fitted:


I have tested on air with the bolts nipped up and no leaks so far although a steam test will need to be performed to confirm all is well.

Finally, here is the reason why I am going to all this effort (so I can oil the cylinders after a run):

Good job Tom! Endmills in a bench drill tend to be a disaster

Fascinating set of events nicely documented. Thanks Tom, well done.

Neat. You are getting the hang of model engineering.

The valve chest covers on your loco must be high quality castings. Some grey iron castings I've encountered have have a hard skin that can take the edge off a HSS cutter very quickly when taking a light cut.

A couple of things to think about though for the future.......

That probably was a 4BA counterbore. The pilot of a counterbore is designed to fit the clearance hole for a given fastener, not a threaded one. That's why it seemed to be oversize. That's how it works with metric ones, so I assume BA ones were the same.

Dave is right about not using a milling cutter in a bench drill. It usually leads to disaster, as drill chucks can be loosened by the cutter vibration.

How do I know this? There is a chunk out of my milling vice that constantly reminds me that it wasn't a good idea to use the drill chuck to do a quick milling job, instead of taking the time to replace it with the collet chuck.

Also the quill of a bench drill isn't designed for the side loads generated by a milling cutter. That's the reason the cutter wandered around when you practiced on a piece of steel. I think you dodged a bullet by deciding to turn the cutter by hand.

Regards,
Graeme

Thank you guys, it is a slow process but I somehow get there in the end.

GTB wrote: ↑Tue May 12, 2020 1:24 pm Neat. You are getting the hang of model engineering.

I am trying, I hope to one day be able to get into it properly using a lathe and mill.

GTB wrote: ↑Tue May 12, 2020 1:24 pm The valve chest covers on your loco must be high quality castings. Some grey iron castings I've encountered have have a hard skin that can take the edge off a HSS cutter very quickly when taking a light cut.

I agree. The covers are interchangeable with both cylinders (I know this because each cover + cylinder is stamped with the numbers one and two for identification and when I received the loco the covers were on opposite cylinders and bolted upside down). Either that or the original builder was very diligent (the chassis has been made with care as the loco can run just under 10 PSI on my rolling road).

GTB wrote: ↑Tue May 12, 2020 1:24 pm That probably was a 4BA counterbore. The pilot of a counterbore is designed to fit the clearance hole for a given fastener, not a threaded one. That's why it seemed to be oversize. That's how it works with metric ones, so I assume BA ones were the same.

My engineering friend did mention this, however, I assumed as the seller had confirmed the part was sized incorrectly that it was wrong as I did message them explaining what I was trying to achieve.

GTB wrote: ↑Tue May 12, 2020 1:24 pm I think you dodged a bullet by deciding to turn the cutter by hand.

I was very concerned about damaging the covers so this is why I turned it by hand. I only thought to do this as previously I had tapped the holes turning the chuck by hand, experience paid off here!

What a lovely documentation of the whole process, once u started i had to read the while thing. i could very much relate to the challenges and appreciate your ingenuity and resolution to solve them.

As regards your injector, onle one out of 2 on mine work, i have cleaned , adjusted and everyother thing in between, i will likely order the same one as you have , it looks much like the same size in mine. Can I burden you with to measure the approximate dimensions please?

Your solution to oiling the steam chests is great, however not easily possible on my own model as the steam chest is completely under metal shroud . Maybe u can work something out.

Coincidentally , 3 days ago i also ordered the same rolling Roads as you have, I will be making a running setup with maybe with the possibility of adding resistance to some of the rolling bearing to simulate load, I noticed my loco loves working against an opposing force.

Thank you for the kind comments.

I will contact you via PM as this thread is about my loco.

Air test of the modified steam chest covers, no leaks on air!