4472 Flying Scotsman 5"

[greenglade]

evening chaps/chapesses

I've just had these excellent photo's sent to me by Owen Chapman of Saturday's meet, thought I'd share them here as they are much better than mine...the colour is much more vivid and of course the resolution is far higher , looks great...

 

 

 

 

 

 

Pete

[greenglade]

Back to reality and on with the build, I haven't got much to show for tonight but since this next job is fairly involved I'll cover what I've done so far giving a little more detail of what's to be made during the next week or so.
I'll start with Don's drawing, I am of course talking about the valve crosshead guides that are part of the steam chest covers, or will be once I have machined them and silver soldered them to the covers already done. The drawing shows what's what. I suppose the best way to describe them is to say they are a little like 'arrowheads' with inner grooves for the valve crossheads to slide along, hopefully, things will become clearer as we progress.

 

To add some 3D here's a picture that I took at York in 2016, this is the rear cover which is a little longer than the front.

 

Ok, so onto a little machining, well a lot actually but little to show for it, first up the bronze blanks that my son kindly supplied me and cut into small rectangles for me to make a start. my chop saw blade is too blunt and as for using a hacksaw?.. no chance, this is 1/2" thick bronze (I had thought it was 10mm?) and my days of cutting this stuff by hand are long gone. So, thanks to my son I have 10 pieces of 50 x 32 x 12.7 mm bronze plate. I have a lot of machining ahead of me as these blanks need to be reduced to 1 19/32 x 1 1/16 x 21/64 (4 off) and 1 25/32 x 1 1/16 x 21/64 (6 off). Note the drawing shows 2 off and 3 off but these are assembled parts, each slide requires two sides. here we have the blanks as they arrived.

 

Here they are machined to size but not thickness, this took most of a day to machine. I first had to square everything up as being cut by saw left them out of square and then reduced to their correct dimensions. 6 of one and 4 of the other.

 

Lastly, I have made a start on reducing the thickness to their required 0.328, only managed 2 of the larger blanks so far.

 

If all goes well I should manage the rest tomorrow but it will take most of the day, I have no surface grinder and can't currently use the 4 jaw, so it's small 25 thou cuts with the mill, don't you just love model engineering. Once the blanks are finished I can then get stuck into the little properly...

Cheers

Pete




 

Edited August 13, 2019 by greenglade

[greenglade]

evening all

Continuing with the machining of the valve guides, after I is had finished getting all of the blanks to size I cut the first slot which is the inner slot for the crosshead to slide in. This slot as drawn is 5/16 wide by 1/8 deep, I have made the slot 8mm as it was the sharpest slot drill that I had to hand, my 5/16 drills have seen better days. 8 mm is probably a better size anyway as the 5/16 crossheads will need clearance to slide, since I haven't made the crossheads yet it's of no consequence to the final item. 
The first picture for tonight shows that all 10 blanks have now had said slot machined, btw, when machining the blanks to the thickness required I only machined one face, I'll explain why in a minute.

 

before I could machine the top slot I first needed to sort out a piece of metal to bridge the first slot so that it could be held securely in the machine vice without deforming. I used a length of 8 mm square gauge plate (it was the only thing that I had), grinding it down so that it would fit into the slot without protruding from the bottom as seen in the next picture.

 

I could then machine the top slot which again is straight down the middle although this one is very slightly less in depth, this is why I left one face unmachined so that I wouldn't get things mixed up during further setups, the unmachined face is completed removed in later machining operations anyway. The thickness between the slots is drawn as 1/16 although Don states this isn't critical, I have chosen to leave it slightly larger for a stronger part, as Don noted, this part could get a little flimsy if not careful, I'm playing safe. The picture shows the top slot machined and the brace in place for said machining operation.

 

With the top slots finished, it was then time to remove the metal from either side of it, this is where extra care is required. I first bridged the top slot as with the bottom but for this, I didn't need to worry about the height of the piece involved. I used some brass square which was filed down a little to make it a snug but not distorting fit as there is no force from the jaws this time. For all operations, I have set the part as close to the jaws as possible, that is, the cutter just clears the top of the jaws. The sizes are 3/32 for the bottom plate and 1/16 for the two uprights, again I have made these very slightly larger. Note that the top of the bottom slot is higher than the bottom plate top edge, hence why Don mentioned it getting a little flimsy, it's not, it's rock solid but could easily be destroyed by a wrong cut, considering how many hours has gone into each one of these little that would be a very bad thing..

 

All ten at the same stage...

 

Next up was the 3/8 slots which are to allow access to the 'C' nut glands for tightening, Don has drawn simple rectangular slots, this is not correct, they have a curved corner, not sharp. I, therefore, used a 6mm cutter, used it to step drill along the centre line and then open up to the sides of the slot, I have made the slots slighter longer to be closer to the prototype in appearance. The picture shows how I held each part. As with all operations, once set I could do each part on the same setup.

 

And here we have all ten parts to the same stage, note that the smaller guides which go on the front of outside cylinders also have small slots on their front face. Don doesn't show this but it is on full size, I'm guessing that it may be to give more clearance for when fitting the 2:1 arm pins, anyway, it's on full-size and thus now on the model..

 

I have to say that this has been a marathon machining exercise ( lots of swarf to clear up) and it's not over yet. Next job will be to angle the sides and top face, hopefully, I'll get this done tomorrow.

Cheers

Pete


 

[greenglade]

well, that took less time than I thought and I have to say that I'm sure glad these guides are nearly finished, it's been a long week of many hours machining.. I need a break...

So where am I?...I have finished all of the machinings except for one extra on top of the drawing which will be to fit the oil pot and drill down into the slideway on each slide, I'll do this once I have made the pots following the full-size design. My plan is to make 4 brass reservoirs which will sit above the lower running board and under the top running board where the access hatches are, more on this later, a fair later in fact.

Ok so the final main machine work, first up was the angles along the top and bottom of the slides, I have deviated from Don's drawing and followed much closer to the photo's that I have, it's just a case of having steeper angles which go more to a point. the angles worked out at approx 9 and 8 degrees depending on long or short slide. Luckily my machine vice swivels so this was a fairly easy task once the angles were decided on, here's one of the rear (long) slides having it's first angle machined. After noting the X,Y final positions I did all 6 long slides with this setup. Reason for noting the 'X' reading is because I have left a slight kick on the trailing end where it meets the cover to give it that one piece cast look one silver soldered together.

 

With the first side done I then clocked the vice around by 18 degrees and did the other side, I repeated the process for the smaller (front) slides.

 

This just left the angle down the top (side as fitted) of the part, for this I reset the angle, for this is much shallower at approx 3 degrees, as can be seen I used some steel to give support behind, the clamp was used for added security although not always fully tightened, just as a fine adjuster to keep the cut along the two ridges equal, hope that makes sense?

 

here we have all ten slides at the same stage, I have put them on some W&D so you can make out the shape easier. Next week I'll spend a few hours removing all machine marks and filing (rounding) off the sharp edges. Once that's done they will be ready to silver solder to their respective covers before I can do this I'll need to make up a jig to hold them in place to the covers, that will be my next machining job.

 

One more picture to show one of the rear slides held roughly where it sits on it's cover. The nuts are temporary standard sized head items and will be replaced with the smaller head 8BA's once I refit the cover with the slides silver soldered to them. This picture also gives a clue to where the rear reservoir will sit as you can see the access cover above, in fact, it's centre is right above where the oil pots will sit on the slides. FYI there will be 4 (probably brass) reservoirs under the raised running boards, two each side, the one that sits under the cover in the picture will supply both the rear valve slides and slide bars below. The forward reservoirs will supply the front slides, all gravity fed.

 

That's it for today, I'm looking forward to getting these things completed, they certainly look much different to the rectangular block they started as and hope there aren't many more parts this labour intensive in future..haha.. yeh right...

Regards

Pete

 

[greenglade]

continuing on with the valve guides, I have now silver soldered the 3 long guides together, leaving just the 2 short guides which I'll tackle tomorrow, I would have got them done this evening but had forgotten that they have a slightly smaller bore than the longer guides and thus will need to modify the jig first.

I'll describe the jig next but first to say that the guide ends were rounded off first and the machine marks removed with a little filing
Don in his words made the crossheads first and used those as a jig, doing a little filing after to achieve a sliding fit of said crossheads. I have gone a different direction, making the guides first and then make a jig to hold the parts together for silver soldering. Two reasons for this, first I wanted a larger surface between the guides to ensure they remained parallel and second, I didn't want to risk any damage to the crossheads if used during the heating up stages.

Here is a picture of the jig, note that the gland nut is the wrong way around in this picture, the picture that follows this one will hopefully show how it works better than I can describe.

 

Here we have the jig assembled ready for the silver soldering of the parts, The steel block (long crosshead) suspended between the guide halves is 5/16 thick and 11/16 wide. A tool clamp is used along with some packing to hold the guides tightly against the guides. The cap screw which is attached to the steel block and goes through the gland nut (just as the valve spindle would) is tightened to pull the two sides up close against the cover. Before this is fully tightened I brush on some flux around the mating surfaces to help with penetration and then tighten fully, being sure that the cover is aligned correctly to the guides. Once all is ready I go over the mating areas again and cut/place some silver solver bent to right angles along each join on both sides, this takes a little time but IMHO worth the effort. It's then just a case of placing some heat board close to contain the heat and brazed everything together.

 

here's the first one placed for the middle cylinder, note that the middle cylinder only has one set of valve guides and the front is a long guide, whereas the outside cylinders with two sets apiece have the short valve guides at the front and long at the rear.

 

Lastly, all 3 long guides assembled and seen here after a quick clean in some citric acid.

 

Tomorrow I should be able to get the fronts to the same stage, I'll let you guys know how I get on in the next update...

More soon

Pete



 

[greenglade]

Good afternoon chaps/chapesses

Just a couple of pictures for today to finish off the main assembly of the guides, I still have some work to do on these, I need to make up 10 rectangular oil pots drilled to fit a small pipe for the oilway, I'll leave these overlength and without unions until I know exactly how long the pipes need to be. I'll need to drill a small angled oilway in each guide to feed the crossheads and then I'll need to polish the crosshead slideways for a smooth action of said crossheads. so some work left to do but not much more than a few hours.

The first photo is one that I should have posted yesterday, it's just a view of the final setup before heating, you should be able to see the small lengths of right-angled brass pushed up into each corner. One last job before heating was to brush some more flux over the pieces of silver solder.

 

And here we have all 5 covers with their respective guide halves silver soldered in place. I have only pushed on the covers for this photo, they aren't bolted up yet as they need to come off before I can get back onto the cylinders and finish them completely.

 

For the rest of this week, I'll be stripping down both the lathe and mill to dial out some of the play which has crept in since their last service, already made a start on the lathe.
After that and a short interlude as my son has asked me to do some machine work on his Cossie cylinder head, I'll get the outside cylinders to the same stage as the middle which is to make/fit the piston glands and their retaining covers and to machine the slide bar fixing platform above the gland. Lot's to do after that on all 3 cylinders, finish pistons and make their rods, machine the valve liners and fit them into the steam chest, make the valve bobbins and their spindles, so yes I'll be busy for a while, the first job for this weekend is to order the material required, minus the bobbin material (fluorosint) which is a little too dear for me just now.

Thanks for looking in guys...

Pete

 

[greenglade]

Evening all

I have now made and fitted the valve guide oil pots scaling off a photo that was side-on, so hopefully, they will look something like the prototype, if anyone actually notices them under the running board that is.. 

First was to cut up some 1/4" BMS into 10 x 8.5mm lengths, I then machined one side down to match the width of the web on the guides and then drilled a 1.6 mm hole through the 1/4" section. This hole is offset a little to bring it close to the crease of the web that it sits on. The picture shows this first stage completed.

 

I then worked out the position of the oil pot and used a small section of steel to place the pot against for drilling. I only did this for the first one, realising that I could do it much quicker in the machine vice as I would have a datum to work from. So the remaining guides were all held in the vice, once the distance up the web had been ascertained all I needed to then do was use a block to position the hole distance next to the web wall, hope that makes sense? With the 'X' locked I could do first the long guides and then adjust for the smaller guides, two holes in each. The two lengths of guides have their oil pots in slightly different positions which I matched from the front face.

 

Having spot drilled each of the oil ways I then cranked each guide over to drill an angled hole through the guide into the crosshead sliding channel. i used a centre drill to begin with and then a 1.6mm drill bit.

 

I then finished the oil pots, making them an oval shape with rounded edges, filed and then polished.

 

Next, I held the oil pots in situ ready for heating, it was an error to do this in copper, just me not thinking clearly....it meant I had to clean up a little after but no big deal, next time I'll remember to use a fuse wire and coat it in bar soap first....

 

This picture to show how I held them for heating, the pots were soft soldered to the guides, no need for silver solder here.

 

Lastly, a picture of the finished middle cylinder guide in place and here we have a small issue to solve. As can be seen, this guide is very close to the exhaust opening for the outside cylinders. Ok, the added oil pots don't help but even without these, things are a tad tight. I think what I'll do is machine a little of the guide edge to give more room for the saddle flange that sits between it and the frames and also take some metal off the saddle flange if required, I'll have a close look at this when fitting the middle cylinder for the last time. I have fitted a couple of temporary pipe sections to give me some idea of how to route them, clearly not as I have here as I wouldn't be able to do the cover nuts up.

 

I may use a larger tube from the lubricator and then branch off these two small tubes ensuring they are of equal length. I will take a look at how the prototype is, adapt and and go from there.

More soon chaps

Pete



 

[greenglade]

Hi all

To finish for this week I have the guides now finished (bar lapping the guide channels) for the outside cylinders and contrary to what I said a few days ago, I took a look at the issue with the middle cylinder guide obstructing the saddle exhaust flange to the outside cylinders now, it's certainly very tight in there, more so when some fool adds oil pots...

Ok, so first the outside cylinders, I just have the one photo as they are the same process as for the middle cylinder, just that they have two guides compared to the one for the middle cylinder. I have placed them together and laid the copper tube which will be used on top, the copper tube is small-bore Refridgerator cooling tube, IIRC I bought two sizes, 1.6 and 1.8 mm OD, the larger size is ideal for the Bowden cable that I need to make for the drain-cocks. At least I think this is what I have, I've forgotten, at some point in the near future I'll need to fit the Bowden cable so guess I'll be able to give firm details then.

 

So, on taking another look at the middle issue I set the guide assembly in the machine vice as best I could and machined approx 60 thou off the inside guide down to where the lower web is, the photo will show this. I also machined off some of the top of the oil pot this side as it's going to be very close in this area as the outside exhaust passageway which is integral of the saddle goes over the guide and there won't be much room for clearance. I'll take a look over the next few weeks to see just how close the saddle is above this middle guide and make any changes that are required, the oil pots don't help. If anyone out there knows the layout of the pipes from the middle guides I'd be very interested to hear from you.

 

 



This last picture shows the state of play today, I can work with this, the gap is just over 1/8th, the saddle flange which needs to fit between is close to 1/4", in fact, it's just a little smaller than the machined edge along the top of the saddle clearly in sight. So at some point, I'll need to reduce the thickness of the saddle flange on this side only. I am happy with this, that gives me approx 1/8th thickness which is more than enough for the CSK screws which go through the frames into the flange and thus will seal the exhaust passageway when assembled. I tell you, there's nothing simple when building a Gresley Pacific, more so when you add detail, the workload ahead of me is, well it's frightenging, but hey it will be fun...I hope...

 

Yesterday I received the gauge plate for doing the slide bars for all 3 cylinders, along with two sizes of hex for the bolts and some brass for the packing. I also received the cast iron that I'm going to make the cross-slides from but alas it's not thick enough, I ordered 5/16 and received 7.5mm, so 0.4mm too thin, I'll need to find another source for this. I also have the bronze required for the liners and the bobbins, oh and stainless for the spindles, plus you may recall that I've already made a start on the bronze pistons, so these can be finished once mated to their rods too. Lot's to do over the next month or so and of course I shall show you guys my progress as and when it happens...

Cheers

Pete

 

[greenglade]

Evening all

I've spent the last few days tidying up various bits and pieces and finishing off the outside cylinder slidebar brackets which are part of the casting. I'll show the right-hand cylinder first as this is the one that I noted before which was a little off in as far as the pattern. Things like this don't help when making final cutting decisions but I learnt early one to trust the measurements from whichever datum I had chosen and to ignore if the castings didn't fully tally. This particular cylinder is a good example, the issue is the piston gland cast is off-centre to the slidebar bracket above and thus the drilled hole looks off-centre. It is as far as the casting is concerned but is not as far as the dimensions are concerned and those are what I follow.
So here's the first picture to try and show what I mean, it's difficult to see when using a phone camera with it's wide lens which distorts everything but as we look at the picture, the gland housing is a little too far to the left and sticks out that side in relation to the bracket above and yet is inboard of the bracket on the opposite side, also the bracket itself is a little curved and angled slightly up on the left-hand side. As can be seen, it is not parallel with the top of the casting.

 

Here we have the other side for comparison, this side is much better with the gland housing where it belongs although the bracket is in worse condition (thinner) although not as angled as with the other side. It's also interesting to note the total difference in the finish of the two castings, clearly done at different times and perhaps temperature.

 

Ok, so onto the jobs needed to do, here we are back to the right-hand cylinder, I have machined both faces of the bracket, it's base needed to be 3/4" from the centre of the piston rod. Once centred on said rod hole and using a 5mm cutter I advanced along the 'Y' axis to (IIRC) 0.8486 and machined the inner face, width needed for the slidebar to fit was 5/8 and using the same cutter I advanced either side of '0' on 'X' by 0.214. The underside was machined to give the important securing bolts a firm surface to grip, I'll blend in the rad to match the casting later. The sharp corners required on the slidebar base were filed by hand (not shown here). Next, I needed to address the height of the bracket and here I discovered a rare error on Don's drawing. Don shows this as 3/4 but it's clear on all the drawings that the bracket depth is less than the 3/4 distance shown from rod centre to bracket base. Confirmation of the error is confirmed by the fact that the casting itself is too shallow for 3/4". On scaling from the cylinder drawing and the GA drawing I came to the conclusion that the depth should be 5/8" and this worked out well removing little from the casting edge to meet this dimension. The last job was to machine the gland housing to it's final height of 3/8, I had left it slightly oversize and this was achieved using the boring head which can be seen in this next picture. I hope that lot makes sense...

 

I then repeated the process on the other cylinder and shown here...



Next was to machine the gland bushes from Bronze, this was basically the same process as described for the middle cylinder, I have made a new bit for boring the 'O' ring recess, the size of the ring which I have ordered in Nitrile is 5/16 ID and 1/16 section. the picture shows me checking the rad for size which was done by hand. I then removed most of the material down to the halfway mark ready for machining. I have not gone the normal 'D' bit route this time as I found it hard when cutting into bronze, this time I have removed nearly all of the metal and put a rake on the back of the tip to help with cutting, this worked much better. Oh, and yes I hardened the tip first.

 

Lastly, a picture to show the rear of both cylinders and the bushes ready to fit, I'm not saying that my methods are the best or even correct but they work for me and the tools/machinery that I have to hand, oh and I'm happy to report that life is much better/easier now that I have stripped down both lathe and mill and removed all slack.

 

Tomorrow I'll machine up the two gland cover plates and drill/tap the 8BA holes around the gland housings to hold them. that I believe will be all the machining involved on the cylinders bar the final pass with a reamer through the liners when fitted, there's a lot of work involved with those so it may take me a while, more so if I get sidetracked.... again...

thanks for looking in chaps/chapesses

Pete

 

[greenglade]

Continuing with the cylinders I have finished off the gland cover plate fitting and tidied up the gland housing themselves. First, an extra that I also did on the middle cylinder was to drill/tap 6BA into the housing as extra security in holding the gland bush in place. The bush is a drift fit so shouldn't move anyway but with no shoulder and involving two different metals and when heat is involved I thought it prudent to do so, especially for the middle cylinder as once the model is completed, getting to it would involve a major overhaul.
The first picture shows the tapped hole's location and also that I have now drill/tapped the 8BA holes to mount the gland cover plate. The good thing is that even though the gland housing is offset, the cover still sits within it, I'll show this better in the next couple of pictures.

 

View from rear 3/4...

 

and square on, I could remove a little more from the housings but since I'm doing this by hand I think this will do, more so as most is hidden from view and when looking at full size, well that varies too...

 

Now I'm back with the pistons and their rods, these are relatively simple turning but I'll show what I'm doing as after being given some advice on joining piston to rod I'll share what I've done here.

To begin with, a picture that shows the piston blanks (machined some months ago) along with the 3 rods cut oversize. Don states on his drawing that the rods are in total 4 7/16 long including a 1/2" long 1/4" spigot half of which is threaded 1/4 x 40 TPI. A side note states (check to place) and so I have cut these rods overlength at 5" Note that the piston bores have been chamfered, this is due to the advice given for which I'm much obliged, more on this soon.

 

The piston rod after having the spigot/thread machined, in this instance I am not going to polish the stub, leaving it rough to give a better surface for the retaining compound to grip. Note that the thread is more than the 1/4" shown on the drawing and that I have machined the stub a little longer than the required 1/2"

 

The first piston now on it's rod, when cutting the thread, I did it in stages advancing while checking the fit of the piston so that the plain spigot was fully home and up against both the piston and the end of the 1/4" bore before the thread itself, ie there is no thread within the plain 1/4" bore, hope that makes sense.

 

And a view from the other side, note that the thread is poking through the bore...

 

And so we have all three pistons attached to their rods but not fully just yet. The parts have been bonded on the plain 1/4" shaft by Loctite 640 retaining compound which is very strong and gives a couple of hours curing time.

 

And now for the final joining of the parts from advice given and gratefully received and that's to peam (spelling) over the end of the rod into the chamfer that was machined into the piston.
I have taken this picture to show how I held the rod/piston and the lightweight hammer/metal chisel used. You should be able to see that the end of the piston has been chiselled into the chamfer, I just worked my way around the outside first and then moved further into the middle of the rod. the piston is flat on the two parallels and also held in the vice, there is no support under the rod which might have risked a bend. The worked rod end will be machined flat to the piston when the piston blank is machined to size.

 

The last picture for tonight, all three piston/rod combinations put aside to fully cure, these were checked to see they were running true before doing so not that it would be a problem as the blanks are oversize and will now be finished on their respective rods.

 

While these are curing I'll remove the middle cylinder from the frames and remove all 3 main bore end covers ready for me to check each and machine down the piston's to be a good fit in the bores, the last job is to add the piston ring grooves and fit said rings.

This will be next weeks job...

Cheers

Pete

 

[greenglade]

Good evening all

I'm still progressing a little with the cylinders, I've been a little busy with some DIY of late which will keep me occupied for a while longer yet but did find a little time for 4472.

Just 4 pictures for tonight, among other things, I've been doing the final touches to the cylinder bores, they were pretty good and even better now after a little lapping with some 'Timesaver' fine grit lapping compound.
I am using an auto honing tool which is usually used for brake cylinders etc, it's an ideal size for boring the 1 3/4" bores on 4472 too. I did use this tool a little before, this time, however, I have covered the cutting stones which some felt pads which are wired to the stones and soaked them with the 'Timesaver' compound. First picture to show what I have...

 

here's the end result on the middle cylinder...

 

next was to machine the front of the piston blanks to remove the excess material from the rod and also to bring all 3 pistons to size...

 

The fourth and last picture for tonight shows that all 3 pistons are now at the same stage.

 

The last job to do to the pistons is the groove for the ring, one of the drawbacks of the Warco machine that I have is it's slowest speed is too fast to machine this size PB102 easily and I don't want to risk causing damage this far down the line. I could cut it by hand and may well end up doing so but I'll have another go under power with some new inserts which are due to arrive next week first. I'll let you know how I get on then...

all for now...cheers

Pete



 

[greenglade]

Good day chaps/chapesses

Well, I have to say that machining the grooves has been fun, not, in fact, I have only completed one so far although most of my time has been on some DIY so not as bad as it may seem. Today I decided to get at least one piston properly fitted into it's cylinder. it's been a bit of a sager, none of my tools would cut the groove, not even the new inserts which when facing or reducing diameter cut like butter? I can only put this down to the speed being too fast, with or without cutting fluid it made no difference and so by hand it had to be. The groove ID calculates to 1.525 and thus that's a lot of turning of the chuck by hand. BTW, I used the App, 'O-Ring master' by GMORS to work out the depth/width of the groove which it does very easily, I highly recommend it to anyone doing the same as it was recommended to me by a fellow MECH forum member. All I needed to do was set it for 'Dynamic', enter bore size and ring cord section, it does the rest.

So, only one piston to show for today but that was a lot of work and my arm needs a rest hense the update.. Taking on board Julian's advice I held the rod by it's end that presently is overlength which I mentioned earlier. The other end was supported by a live centre, something I omitted to share previously is that I had centre drilled this end to allow for holding the job this way. For the distance from the front face to the groove I have followed Don's drawing, IIRC it's 7/64, the groove width I have followed the App at 0.185 which is close to Don's suggestion of 3/16 or 0.187. By hand the new insert cut this very easily, in fact all of the tools used did do, just not under power...lol I'm beginning to think this bronze may be something a little tougher than PB102/104 which I thought it was, as stated before it was a gift from my son, anyway, now that I have finished one I'm happy, just have a tired arm... The tool seen in the picture was used just to trim off any burr.

 

Here's the first cylinder with it's piston finished. I have also fitted a new nitrile 5/16 x 1/16 seal to the gland, the piston ring is silicon. I can't show the action but the stroke feels good, there is a good seal as felt by the force of air being pushed out of the rear relief valve opening, so in all, I'm happy with the result so far, just need to get the other two to the same stage.

 

Before I move on I must show this picture to show that before machining the piston groove I first turned up some cast iron, I had thought that I had nothing of suitable size for this but when searching again found a 6" length of 3" dia cast iron that my son had given me some time ago along with some other offcuts from his work. A fair bit of waste but it did the job, BTW the groove and parting off was done by the new inserts with no problem. Since both outside cylinders are of the same size I can fit the test piston into both. You may recall that I left the middle cylinder a little undersize feeling it prudent to do so not being able to tell how much material was left on the cylinder wall during machining. I will do the other outside cylinder first and then reduce the test piston to fit the middle cylinder and check that the ring fits when following the app's dimensions.

 

Moving on to some other business, the postman bought this goodie this morning. No prizes for guessing that it's the backhead cladding halves, these were kindly drawn up for me by Paul (Southern Boiler Works) and sent to Malcolm (Model Engineers Laser) to be cut, the material is 1mm steel.

 

Of course, I had to do a quick check, I may need to adjust the top water gauge hole a little but not as much as it may look as it's misleading with the cladding being held much more upright than it will be when fully fitted. The other holes all seem to line up nicely with some temporary bolts fitted into the two cladding securing bushes for the nearest side, the other half has been folded up out of the way for this test as the tabs won't allow me to fit it properly. I haven't parted the parts yet as I'm in two minds as to leave them connected for when shaping them to fit over the crown and down the sides, there is an extra 15mm of material to allow for this forming. Once I have decided I'll make up a suitable former and make use of a dolly/hammer. I'm very much looking forward to working on the boiler/backhead, there's a lot of detail to add to these cladding halves, looking forward to it very much indeed...

 

Hopefully, I'll get the other pistons sorted during this week, then on to the big job (well it is for me) of the liners/ bobbins and spindles, I'll have to leave the valves themselves until later once I have some fluorosint.

Thanks to all for the input/advice/suggestions...

Pete


 

[greenglade]

good afternoon all

I've been very busy of late concentrating purely on getting the piston's finished and working smoothly within their respective bores. To arrive at the correct dimensions for the pistons I have used a free online app that I have to say is excellent for this purpose. For those interested the app in question is O-ring Master by GMORS, it makes this job very easy and can cover a host of applications from piston (static or dynamic),rod and surface fittings.
The details for my cylinders are as follows:

R/H cylinder: Bore 1.746
Ring CS 0.138
Groove depth OD 1.506
Groove width 0.186

L/H cylinder Bore 1.746
Ring CS 0.138
Groove depth OD 1.506
Groove width 0.186

Middle cylinder Bore 1.734
Ring CS 0.138
Groove depth OD 1.494
Groove width 0.186

The cross-section is what I chose, it's 3.5mm , you can select from the available CS sizes in the app

As stated in the last update I had to resort to doing the groove by hand, a lot of work but it's done now, just hope that I don't have to repeat this again..lol

As well as machining the groove I also looked again at honing the bores to get them as smooth as possible. I think that I spent approx 20 mins honing each cylinder, using the honing rig as shown before along with Timesaver fine compound mixed with two types of oil. First was lathe machine oil and for the final passes, I used a watchmakers oil which gave a really nice smooth finish. This time though I used the rig's oil stones directly on the bores rather than the pads, I was worried before that they may have been too harsh but with the oil mixes, they worked very well.

I only have the one picture for today, I have placed the pistons in different positions to hopefully share more information. The pistons move in the bores very nicely, 20 PSI will push them the length of the cylinder and 25PSI will fire them out of the end. Note that these tests were with open cylinders, no end covers and various open holes for the drain cocks, relief valves and steam chamber passages. Air was blown in through the rear relief valve hole with the piston pulled back as far as it would go in the cylinder, so further back than when in operation. Thin oil was coated around the bores for the tests.

 

I'll give the lathe a good clean now and take a look at what's next on the list, probably either liners or slides bars depending on what takes my fancy...

More soon guys

Pete


 

[greenglade]

 

 

 

 

On to the liners which are made from bronze, I can't recall if I said it was PB102 or PB104 but it's one of those, think it's listed elsewhere in the build.
Chucking a 12" length of 1" bar I centre drilled one end for a live center and machined approx 10" down to 0.930 as per drawing, the picture shows how I held this, one advantage of the warco over MyFord is it's size.

 

I then parted off the 10" machined portion so that I now had a length running true rather than the cast round bar I had to begin with. Something to note here, I had no issue in machining or parting off this bronze so I have no idea what bronze I used for the pistons but it wasn't either 102 or 4, guess it's some form of hard drawn bronze..perhaps? It's tough is all that I know. Picture to show parting off wasn't an issue.

 

I then set about profiling each liner, drilling 3/8 through each and parting off. Before parting each lip Dia was checked to be as Don calls a 'rattling' fit into each cylinder recess, the lip was left over width for now with the liner spigot being the only part machined to size, checking with each cylinder for it to be a few thou oversize for a tight fit.

 

I then step drilled each bore to approx 11/16 just needing a reamer to finish, for which I have ordered an adjustable 21/32 to 23/32 from RDG tools. I also need to open up the ends a little applying a small taper. The picture shows the state of play, the liners are sitting on the cylinders so that I don't get them mixed up, the steam chamber openings are all very close, within a couple of thou of each other, which is good enough.

 

The next job will be to cut out all of the 3/16 sq ports, 6 per liner, this should keep me busy for a while. Currently, I'm spending a little time cross-referencing all of the dimensions to get the liners and thus the critical port positions in their correct positions, it's proving a bit of a brain twister, think I'm seeing double now but worth the time to get this right. I knew that I would have to visit this more closely having no real means to accurately measure depth cuts on the lathe, having to rely on a vernier tail is not the best way of doing things, no working DRO and inaccurate dials can be a real pain at times...I think they are pretty close if my maths is working that is...

More soon folks

Pete

 

[greenglade]

this will be the last update until next week, I'm doing this now as it sets me up ready to get on with the rather long job of doing the ports, I have now decided how I will do this and shall give details today and then sometime next week (may take longer), I'll show the results.

There will be 6 ports in each liner, the drawing shows them to be 3/16 sq although Don does state that they can be wider (or is that long?) as long as there is at least 50% of material left around the circumference. There is a trade-off though as wider can mean the valve wears quicker, I'll decide on this when I start machining after the weekend. I will, of course, use the rotary table to accurately plot the six ports around the liner and will use a hardened thimble (cup) to accurately plot the position and size of each port, however, I will do this differently to how Don has described, BTW Don has given the wrong dimension for one of his thimbles, so for anyone else building Doncaster and following his words, check the drawing and you'll see the error. My method is basically the same but done in a way where I can accurately repeat the position of each liner in the rotary chuck. Don describes using two thimbles which when slid onto a liner and positioned either end of it the gap in the middle is the width of the ports.
I will be using a single thimble as describe below...

The first job was to turn up some steel bar and after facing, turn down to approx 1". Next, it was centre drilled, step drilled and finally bored out to just over 7/8" making it a sliding fit over the liners which can be seen in the first picture. Note this thimble is over length for now.

 

I then machined a 3/16 slot approx in the middle across the thimble using the machine vice and them going back to the lathe to turn down one end to give a section 17/64 (0.266) wide from the slot thus in effect making the first of Don's thimbles. I then reversed the thimble in the chuck and turned down the other end too as close as I dare to the slot, thus creating both of Don's thimbles in one piece and I'll show why in the picture after this.

 

Hopefully, this picture shows what I'm up too, Here we have the finished thimble, (it has now been hardened) over the test liner and held in the rotary table chuck. My reasoning is that in this way, once clocked, I can place each liner in turn into the chuck in the same position ensuring that all liners have their ports 17/64 from the front lip. All I need to do is drill each hole and rotate the chuck 60 degrees for the next and rotate the thimble independently around the liner to allow this. When all 6 holes have been done on the first liner, I'll change the cutter to a smaller size (perhaps 2mm) and using the DRO can plot the size of each port from the centre of it's relating hole, opening to 3/16 wide and to whichever length I decide on, probably 3/16 but we shall see, I think that makes sense? This should ensure that all liners are identical. The reason why I turned down the second end was to give me enough liner to hold securely in the chuck, it's a bit of a balancing act as I also need it wide enough to give the collet chuck enough room for machining, we shall see how this works out next week.

 

It will probably take me some time to do all 6 liners, I hope to get them done during next week, wish me luck.....

Pete




 

[greenglade]

evening chaps/chapesses

No, I haven't done all six liners already, but I have done one which I'm pleased with and needed a break from milling so will show what I've done for today....

I laid out before how I was going to set up each liner, making it a simple process to do all six liners without needing to reset more than just the mill head position for each. I first needed to be able to find the centre for the port on the 'X' axis ('Y' already set via the rotary table centre.) As the port is very small and not so easy to clock I decided to turn up a 3/16 dia peg that fits into the port. The picture shows what I did, it's stepped to allow clearance from the chuck, I only needed to do this once, with the rotary table dial set at 0 and locked on the mill table and the DRO also set at 0 for both X and Y I don't need to use the peg again as the thimble seen in the picture sets each liner in its correct position for this operation, I hope that I said that right...

 

I few simple pictures to show my approach, first I centre drilled the liner for the first port hole, here I used a long centre drill and of course, the rotary table as mentioned is at 0/360.

 

Next job was to open this up with a drill, Don states to use a number 14, I've gone for a number 16 as I prefer to give a little more meat to the final machined edge. Plus I'm not going to be finishing off the square to shape by hand filing.

 

I then needed to machine the square, for this, I chose a 1mm cutter and after calculating the DRO setting allowing for said cutter dia I machined each port to size. this took some time, the cutter isn't able to do this in one cut, I worked around the hole at 4 settings, 0.060 (ie: 'X' 0.060 and -0.060 and likewise with 'Y'), 0.065, 0.070 and 0.074, this gave me the hole size but I also needed to do this in 'step down's to eliminate anyway lean of the cutter. I didn't measure this, just did it in 4 similar depths, starting each plunge in the centre so as not to deflect while plunging. The picture shows the first port nearly fully machined, just leaving one more pass. The process was repeated every 60 degrees to give the required 6 ports.

 

Last picture to show the first liner with it's ports completed bar a final polish and ream. I am not going to square off the corners, preferring to leave the 0.5 mm rad as it is guaranteeing that all 6 ports and liners will be identical.

 

Although the first liner took a fair amount of time, now that everything is set the others should be much quicker although the machining itself is fairly labour intensive and nothing can be done about that.
thanks for looking in guys, more in a few days time.

Cheers

Pete

 

[greenglade]

The liners are all but finished, or should I say, I can't think of anything else that needs doing, so what have I been up too? First, on rereading what I wrote last time I thought it best to show an extra picture of where I increased the depth of the cut for the square port as I wasn't convinced that my words described it properly. I took this picture at the point of increasing the depth, the first cut is approx 20 thou deep and after it crosses the halfway point of the side furthest from me (easiest side to see) I plunge a little deeper where it has the least resistance as it's in the centre of the radius on that side. Since the first port, I have changed the cuts a little, now reduced to 3 cuts and 3 depths, made things a little quicker.

 

now we have all 6 liners completed, I'm a little amazed that my one poor little 1mm cutter lasted the course, very impressed with that. Not easily seen in this picture but the ends of each liner have been tapered out a little for ease of fitting the bobbin and I have angled the lip on each to help with the flow for the exhaust. I also checked and rechecked the overall cylinder dimensions for where these liners sit, any discrepancies I have tackled with a little modifying of the effected liner lip width. Things look good but once fitted I'll devise/make a tool to accurately measure the distance between each set of ports and adjust the bobbin size to suit if so required. The liners have also been reamed to a couple of thou below 11/16 (0.687), once they are fitted in the steam chests I'll run the reamer through again at the required size. This will be by hand as suggested by Don.

 

My plan for fitting these interference fit liners is to use a length of 8mm studding, two stepped spacers that fit into the liner and up against the lip and to tighten them up, not sure yet on whether to do both together or separately, I'll take a look at this tomorrow depending on how tight they are. The picture shows two opposing liners and the rig to tighten them. I'll adjust the studding down a little more to be biased one side so that I can get a long reach 8 mm socket onto the other end.

 

The last picture for tonight shows all 6 liners held together and labelled ready for tomorrow, the reason I'm not doing this tonight is I'm now placing these into the freezer to hopefully help with their insertion tomorrow. I could also put the cylinders in the oven for a short while but think try just freezing the liners to begin with, they will also have a Loctite retainer applied for extra security.

 

I have tried to take a lot of care in making these in an attempt to get a nice sharp even beat, hopefully, a Gresley 6 beat rhythm....

Cheers

Pete

 

[tigerburnie]

641 bearing fit? I have used that a lot, but not with items that have been chilled. What is the fit, are you talking interference fit?

[peach james]

So the afternoon of this adventure- 

 

 

I called it the "New River Coal" loco- because as long as you had a river of water going in, with a coal mine supplying you, it went.  Sort of.

 

I set to, and went and looked at what the bobbins (Valves) looked like, and found that the valves were some .125" short.  Quite how it had steamed at all, I'm not sure...

I am very confident your valves will match the cylinders.  Which is fairly important.

 

So, while you may not end up with really crisp beats, I am sure they will be workable.  Wardale figured that really crisp isn't what you want, that trapezoidal shape is probably better.  (covered in "The Red Dragon").  

 

Lovely work,

[greenglade]

Haha...love the quote James..thanks for sharing...Tiger, yes, interference fit of approx 0.003 thou, I'm freezing the liners just to make life a little easier, I don't have the freezing gear like the full size boys...:)

[greenglade]

Liners now fitted:


I have to say that the effort it took to fit these little gems must be equivalent to a hard session down the gym, not that I would know what that is you understand but I have a good imagination...

As stated yesterday, the liners were left in the freezer overnight, I'm not really sure if this made any difference as the liners are quite thick but it helped in my own mind. Since the liners were still in the freezer and I wanted to keep them as cold as possible I decided to tackle this job in the kitchen, or should I say, that's where I began.

Before doing anything and after taking into account what Don (MECH) said last night I took another look at whether to fit the liners in two's or singularly. One thing that was obvious was that if in two's I had no fixed central point to pull against, what I mean is, one or both liners could be pulled off centre when beginning which may make life more difficult. So, the first thing I did was to turn up another end for the jig that butted up against the outside of the steam chest, just fitting within the studding and having a step to keep it central.
The first picture shows the tools ready for action, a 12mm ratchet spanner, 12 mm long reach socket and the 3/8 rachet. You can see the new turned end which I made thicker than before and out of bronze. Lastly the Loctite retainer, for this job I chose a 'slip fit' retainer with a 2 hour curing time, this is probably overkill and probably not going to do a lot at the 200c mark but I used it anyway just for peace of mind. After the effort it took to fit the liners I think I needn't of worried but it's there now.

 

I began with the middle cylinder front liner and was happy that the liner stopped fully against its lip, I did try to make a mark so that I knew it was fully home as it was so tight and difficult to tell when to stop whilst fitting but it was obvious when the liner was home as I nearly ripped the cylinder out of my hand...lol A picture to show, obviously the liner still needs it's final reaming session. I may grind a little away from where the liner steps down to the exhaust passage for better flow, I'll take a look and decide on this later.

 

Now, I got the middle cylinder done and halfway through the left-hand cylinder and gave up with the idea of doing this in the kitchen as my hands could no longer grip the cylinder, the effort had been that great, plus my poor old hands just can't do it anymore...
I retreated to the workshop and it's trusty vice, I first put the remaining liners into a freezer bag with a few blocks of ice. The picture shows that the rear liner has been pulled fully home while the cylinder is held in the vice, this was a much easier way of doing it although still a lot of effort used on the rachet/spanner.

 

The last picture to try and show a liner fitted, I have tried to keep the opposing ports in line for measuring when it comes to making the bobbins, of course, these have rotated a little during fitting but it looks like I can still take accurate measurements with the tool I plan to use, ie I still have a straight line from which to measure from. As I said, I still need to ream these but think it best to wait until I can get a good long reach 11/16th reamer to do so, I just need to remember to do so...:)

 

So what next? well I still don't have any material for the bobbin valves so that will need to wait a while, I may turn up the spindles and glands just to get them out of the way, or I may go off on a tangent, I'm good at that, we shall see...

thanks for looking in folk...

Pete

 

[tigerburnie]

Well done Pete, we used to use a freezer in my last job, (well that was the royal "we" as I had been promoted to an office job), up 4 or 5 thou no problems, bigger stuff needed liquid nitrogen to be sure.

[greenglade]

Yes, that's what they use full size...I'm just glad that it's done..today I've been making up a card template  ashpan....felt like doing something different...:)  i also ordered an 11/16th reamer, when that arrives next week I can finish the liners...

[dajt]

A lot of great work there Pete! Glad I'm building a 2 cylinder slide valve engine

[didcot]

Great work there. It doesn't take much of an interference fit to make it hard going.