4472 Flying Scotsman 5"

[greenglade]

Thanks for the suggestion David, I have used that very same stuff on the car, it's good. I have a number of types that I can choose from when the time comes, that may be a while yet though...:)

 

Pete

[greenglade]

I think that the sun must be shining on me of late as for a second weekend I've had free time in the workshop, I fear this may end soon but hey, ho, while the sun shines and all that...

as anyone who builds steam models will know, you have stressful days and you have more relaxing enjoyable days depending on the job in hand. I for one find boring the cylinders pretty stressful, I think that's mainly down to the cost of these things as there's nothing complicated about the job itself although the 'unknown' is always a factor to bear in mind. Anyway, the other type of day are those where you are sitting down with your feet up type of days, were you are actually having fun...it does happen, honest...
Today has been one of those days, not a care in the world and just having fun, so what did I actually do? Well, first I took a close look at how the running board sits over the cylinder as it's actually bolted to the cylinder by, in model terms, 2 8BA bolts which match the size of all the other bolts down the side valance. The casting does have a small step for the running board to sit in which is great but of course, it doesn't have square corners since it's still as it was when taken from the mould. Taking a quick look at the fit and looking at photo's I took 3 years ago at York I could work out how it should fit/look. the first picture shows that I have taken a small amount from the area to give me a square vertical surface to bolt too. This is a lot easier to set up now that the cylinders are bolted to their flanges.

 

I then refitted the cylinder and placed the running board back in place, not bolted down though, just loosely held there to show how one mates to the other. I haven't drilled the mounting holes yet as I need to be sure of their position. From pictures it seems that the bolt positions varied, in some cases there are 4 instead of 2, some in line with the cladding, others not. I will look for better images for my era of 4472 before committing to hole drilling. Right now I'm thinking that the cylinder cladding bolts are smaller, if so I'll use 10BA, not that I'm looking forward to drilling/tapping those in bronze on a curved surface...lol... anyway, here's how it looks...

 

This is one of the many pictures that I took of 4472 while at York, April 2016. It's a good picture to use for comparison purposes, tit shows how the cladding meets with the running board valance and the two different sized bolts used. Before looking more closely at this I had assumed that the cladding sat under the running board valance but having now seen that it butts up to it it becomes obvious that having it under the valance would be a real handicap for maintenance. This picture also shows that the cladding covers approx half of the cylinder lip and even cuts into it, I'll probably draw a line of doing that one though, we shall see.

 

So, what else did I do while relaxing with my feet up, slippers on, etc, thank god I don't smoke or there may have been a 'pipe' in that mix too...

I went back some years to a job I didn't do when doing the main horns, you may recall this is the second time that I've returned to the main horns in recent months, this time it is for the lubricator pipe connections that are screwed into the top of the horns. I won't bore you with manufacturing pictures as they are basic turning but in essence, they are made from 5mm hex brass stock, threaded both ends with a small hole through the middle. The end that screws into the horn is 5/32 x 40tpi, the other end is 3/16 x 40tpi and is centre drilled for a cone to fit. I will say here, right now, that I am not going to waste time making all of the cones and nuts for this loco (of which there are many), I have enough to do as it is. The connectors like these though are custom jobs so need to be made to spec, well loosely as they are not critical. a picture to show the 6 that I made, there will be others but as you know, I hate repetitive work..

 

Lastly, a picture showing 4 of the connectors that I have temporarily fitted 3/32 nipples and 3/16 nuts, I may go smaller on the nipples if I can find them commercially, I have an old one here which is smaller that fits the copper pipe that I ordered from China for the draincock cables, it looks a possible candidate for the oil pipe too, if I can find the nipples.

 

Well, that was my weekend play time, tomorrow I will get on with something more serious, or will I?

Cheers

Pete 


 

[tigerburnie]

I can't remember if we discussed heli-coils before or not, but would they be an option when considering tapping the bronze? 

[greenglade]

Well hopefully the tapping will go to plan, there are ways to remove broken taps from bronze which I hope aren't needed. My approach will be to drill larger tapping holes than normally required as there's nothing structual here, just cylinder cover fixings...

[tigerburnie]

Fair point, another thing would be studs and nuts, but then it wouldn't be right cosmetically or accurately either I guess.

[greenglade]

Well, you'd still need to tap the holes...:)...but yes it wouldn't be prototypical which I try very hard to follow..

[njee20]

I understand about 10% of what I’ve read,  but my god that’s impressive engineering, well done!

[tigerburnie]

6 hours ago, greenglade said:

Well, you'd still need to tap the holes...:)...but yes it wouldn't be prototypical which I try very hard to follow..

I was thinking that you wouldn't have to disturb the studs again thus reducing the likelihood of any thread damage at a later strip down, would a self tapping bolt get away from the thread cutting, you can get them with hex heads, just not sure if they are as small as you would be using though. I am impressed with you work, your workshop must be very comprehensive.

[greenglade]

The threads will be ok , reason for using bronze is it's so tough, the threads won't wear, it's the reason why all boilers these days have PB102 bronze bushes.  To remove the risk of a fitting being blown out of damaged threads when at full pressure. It will also withstand many cycles of undoing and doing back up of the fittings, or in this case the small 10BA bolts that I plan to use. I can drill the holes oversize and still have enough thread for the job in hand. Admittedly the cylinders aren't made from PB102 but they are strong enough.

As for my workshop, I wouldn't say that it's anything special, my lathe and mill are both of Chinese origin, not great if relying on the dials but can do accurate work with a DRO or constant mic checks, the biggest issue there is how much longer everything takes but you get to live with it in the end. One day I'd love to get myself a decent lathe and mill, life would be bliss in comparison. I can't moan, I have a well equipped workshop if not state of the art equipment...:)

 

Pete

Edited March 18, 2019 by greenglade

[greenglade]

evening chaps

I have spent today setting up the first of the outside cylinders, well I did finish the last update saying 'next would be something more serious'... No machining yet but I will take time to show you how I approach setting up the cylinders, I'm not saying this is the best way but it works well with the equipment that I have to hand...

It didn't actually take me all day to set up as I had to adapt the alloy block that the middle cylinder sat on when it was machined first. This was why I did the more complex cylinder first as it's centreline is higher than the outer cylinders. After taking a few measurements, it worked out that I needed to remove 6mm from the bottom of the block to get the correct height, I did this with a 3" fly cutter which took some time, I can't do deep cuts with this cutter as it's too large for the machine, but works well if not rushed.

My setting up approach was more or less the same as with the middle cylinder. Once happy with the height I double checked it was correct by sitting a cylinder on the block but not bolted down. I held the 1/2" boring bar in the 3 jaw chuck with it's bung slid along it but again, not fixed, the picture should help show this. I then advanced the cross slide towards the chuck adjusting the 'Y' axis until the bung would slide into the bore without binding or moving the cylinder, once happy with that I could tighten everything down.

 

Now that everything is ready for machining here's a couple of photo's to show the final setup. first is from the front showing the bung in the bore, of course, the 1/2" bar is only just in there too as these are blind bores.

 

And here's the view from the rear, we have the strong back across the top, I prefer one that gives a little so it wraps around the curve of the cylinder. There's a tool clamp at the front that holds the flange down, oh and this reminds me when taking the 6mm off the block, I also machined two 12mm wide groves for the clamps to grip. there's a G clamp at the rear and the two stops, one on the side and one at the rear. This gives me a 90-degree jig which locates the cylinder where I want it to stay. As with the middle cylinder I also double checked all was in line by placing the tailstock centre up to the piston gland boss, all looking good if I say so myself. As per usual, I hope my rambling makes sense. 

 

So, no guesses for what I'm going to be doing for the next week or two. I will do all of the machining operations (main bore, piston gland etc) for this setup on the first cylinder and then repeat on the other. It will then be a reset with more material needing to be removed from the alloy mounting block to bore the steam chests...that lot should keep me out of trouble for a while...

Pete


Read more: http://modeleng.proboards.com/thread/5733/building-don-youngs-doncaster?page=139#ixzz5ifBSlku3

[greenglade]

good day all

I have now made a start on the first outside bore, well actually I've finished the bore itself just needing to face either end before starting on the next cylinder. I will cover what I have done so far now as it's already 9 pictures which equate to an hour or so doing the write-up...I must be mad...
First order of business is a quick thanks to Richard for suggesting a piece of wood under the strongback, duly done sir...

The boring bar is the same as used for the middle cylinder, all I needed to do was make sure that the tooltip was fully retracted before making a start, this just required undoing the grub screw and pushing it in as far as it goes until hitting the 1/2" shaft/bar. At this setting, I made two passes to ensure all was concentric, as before the return cut is done in reverse which buffs the bore giving a lovely finish, I did this throughout even though it's not really required until the final cut. The first picture for today shows the cutter in reverse coming out of the bore bringing with it a mixture of gunmetal and casting sand debris. there was an awful lot of sand in this casting, probably trapped in the steam passage although it seemed like more than possible?
The black mark on the shaft is to show me when to stop the longitudinal feed and finish by hand to the rear face of the bore. You get a warning sound anyway as the cutter hits the steam passage but I like to play safe.

 

a quick check in the bore to see how things looked, the recess on the rear face is there to give a larger passage for the steam as it flows into the bore, you can see the passage itself on the left as the cutter has begun to clear it up.

 

I'm not sure if I covered how I increased the tool when describing the middle cylinder so will give a quick note here. All I do is cut small pieces of paper and measure their thickness, I found that two pieces folded double gave me around 18 thou and so that's what my advance would be giving me, of course, a 36 thou cut. I didn't want to risk deeper cuts as the boring bar is only 1/2" (it has to be to fit through the piston gland) it's fairly long and because of this, I didn't think it wise to drill/tap a hole below the cutter to adjust it with a screw.

 

As things progressed I needed an easy way of checking the bore size, a normal plug gauge couldn't be used as it would require me removing the bar for each check, couldn't use a bore gauge and couldn't accurately measure with a vernier. I began to use an inside divider which wasn't very accurate. I then had a rummage through my tools for a better divider and re-found the pair seen hanging on the bar in the picture. It dawned on me that if I set the outside curve of these to 1.750 and hung it over the boring bar I could use these to easily check the size. Better still, they would spring in as I pushed them into the bore giving me some idea of how close I was, in effect they were doing the job of a tapered plug gauge... brilliant.. not me.. just the new found use...

 

With the bore now only a few thou undersize (I'll leave it like this for now, as I did with the middle), the next job was to machine the 30 degrees chamfer on the rear face into the piston gland, this is for the piston to be able to go flat against the rear face as it has a raised section for extra strength around the piston rod. Here I had a 'duh' moment, I had used the tool made previously for the middle cylinder to bore out it's steam chest and forgot to replace it...lol So it was into 'Heath Robinson' mode to see what I could come up with not being able to use the lathe. The end result is seen in the picture, basically, I borrowed the mill's 'tapping chuck' and held a counter sunk tool in it which I have to say worked perfectly, happy days...

 

And once that was done I ran the reamer through it to remove any burr, BTW, the stain seen in this picture is the oil that dripped out of the piston gland that I used to lubricate the boring bar during operation.

 

This left one operation for the boring bar which was the chamfer on the front face, for this, I reversed the bar so that the tool was now facing the other way. Using the same edge as used to buff the bore and in reverse direction, I cut the chamfer.

 

This picture gives an idea of the bore finish, the chamfer that looks a bit rough isn't really as only the inside part will be there after the bore's front face has been machined. 

 

Last picture looking down the bore itself. looks a bit of a mess in the bottom but the rear face and it's chamfer will be done later on the mill the same as with the middle cylinder.
This picture gives a good idea of how large the steam passage is, the exhaust passages are just as large, those will be for another day though, need to finish the bore faces on this cylinder and then get the other to the same stage first.

 

Thanks for looking in guys...

Pete 


Read more: http://modeleng.proboards.com/thread/5733/building-don-youngs-doncaster?page=140#ixzz5ip30pntT

[greenglade]

Ahh.. I seem to have had another 'duh' moment, I forgot to give details machining the piston gland, sorry about that guys, please refer to the middle cylinder as it was the same...cheers

[tigerburnie]

Are the cylinders lined Pete?

[greenglade]

The steam chests are, not the main bores themselves...

[30368]

Really enjoying your account. Admirable work and what a fine prototype. Make sure those conjugated valve gear bushes are spot on! The very best of luck and I look forward to following your progress. 

 

I recall building an LBSCR "Nellie" (3.5 inch gauge) back in 1964-9 when I was an apprentice at Eastleigh Model Engineering Club which was "Underneath the Arches" of Campbell Road road bridge. I left it  there when I moved on and have no idea what happened to it. During 1963/4 many apprentices helped to build the 5 inch gauge C2X 0-6-0. I seem to remember making some of the Stephenson's valve gear - die blocks etc. Ran into that model in 2003/4 when Eastleigh were refurbishing some of our A.C. EMU's. Tried to buy it but no go, wonder what happened to that?

 

Kind regards,

 

Richard B

[tigerburnie]

10 minutes ago, greenglade said:

The steam chests are, not the main bores themselves...

Ah right, nice work so far, interesting use of the lathe.

[greenglade]

17 minutes ago, 30368 said:

Really enjoying your account. Admirable work and what a fine prototype. Make sure those conjugated valve gear bushes are spot on! The very best of luck and I look forward to following your progress. 

 

 

Kind regards,

 

Richard B

 

 

 

Thanks Richard...

 

Yes, I've been very careful/particular with the 2-1 gear pivot pin position, this was all covered a long time ago so not shown on here. I recall setting the 2-1 gear stay in the frames and then clocking the distance from L/H frame inner edge to the pin position with the digital scales and drilled/reamed rather than do it off the chassis. Hopefully, it's correct...:)

 

Pete

[greenglade]

Morning all

I've had a few questions regarding my setup and can clearly see that by me forgetting to post the first sequence of pictures that things are a little confusing, so I'll do it now to make things a little clearer.

the bit I forgot to cover was how I dealt with the blind bore, so here's what I did. the first picture shows the extended centre drill that I made up for doing the middle cylinder some time ago, after checking that it was running true I proceeded to spot the rear of the bore face.

 

Then, using a 12.2mm bullet drill I slowly drilled through the rear face until it began to show outside on the piston gland, as with everything, I check and double check each operation. Here I have the tailstock centre close to the piston gland to check that things haven't moved off centre.

 

And here we have the drill now all the way through and it's spot on centre. Confirmed by being along the casting line flash which indicates the join of the two halves.

 

Lastly, the 1/2" reamer was used to finish. As the taper began to show at the other end I engaged the tailstock live centre with the reamer and completed the pass to achieve a parallel 1/2" bore, ready for the boring bar to slide through.

 

Hope that clears things up and sorry for my mind forgetting that I hadn't posted this sequence previously...

Cheers

Pete

 

[greenglade]

Hi guys

Ok, now for today's planned update, this is just me finishing off the final operations on the first cylinder's bore before de-rigging and moving onto the next. I only had two operations left, the front and rear facing. First picture shows the front face machined although not finished yet, this is as far as I can go with a full swing under power, the rest will have to be by hand.

 

And here's the rear face, the depth of the piston gland as drawn is 3/8, I have stopped just short of this as it's not possible to get a true reading from the cast's rear face, they'll only be a few thou in it though.

 

Lastly, the front face again after hand cranking the cutter to get the required 2 1/4" machined area for the cover. I stopped at this point even though the face isn't fully completed until I'm happy that I have enough depth for the bore which needs to be 2 13/16, I'm only a few thou short of that and haven't machined the rear face yet so things are looking good. The front face is good enough to seal, I'll make a decision after machining the rear inner face and chamfer as to whether I return to it or not, just playing safe for now..

 

 

That's it for this week

Cheers

Pete

 

[greenglade]

evening guys and girls...

I only have one picture to share tonight as there's little point in repeating the process for the second outside cylinder as it's the same but I will give a little background of where I now am.
I machined the second cylinder as the first but this time took it out to 1.744 thou, so only 6 thou short of what the drawing states, I will probably leave it at this in as far as machining goes but will lap the bores to get the best finish that I can, they are pretty good anyway but can always be better and being a little under 1.750 isn't going to upset the applecart.. For the honing, I have ordered some 'Timesaver' lapping compound, the very fine paste suitable for bronze. I'll make up a mop to do this work under power. I have also been looking at 'O' rings and have ordered a couple of sizes to try, I have some PB102 which I'll use for the pistons and 5/16 stainless steel for the rods. I think that I have most of the materials for the cylinders except for the 21/64 Bronze flat bar required for the crosshead guides, this and the gauge plate for the slides will be sorted in due course, I have plenty to do before needing them.
After I had machined the second cylinder to 1.744, I then returned to the first cylinder, reset it on the lathe and machined it's bore to the same size (it was 1.738)using the boring bar with the tip at the same setting as for the second, they are now both identical. hmm, that's a bit of a mouthful, hopefully, it all made sense.

Here's the solitary picture to show both cylinders now bored, things to do other than the steam chest's are to machine the rear inner face and then finish the front face to give me the drawn size of 2 13/16 bore depth. I will also need to drill/machine the front steam passages/ports at some point, may leave that till the end, we shall see...

 

Next job is to remove 1/4" off the bottom of the alloy jig to give me the correct height for boring the steam chests. Not my favourite pastime as it involves using the 3" surface cutter but, hey, ho, it has to be done....

Thanks for looking, folks

Pete


Read more: http://modeleng.proboards.com/thread/5733/building-don-youngs-doncaster?page=141#ixzz5jIxE6kny

Edited March 26, 2019 by greenglade

[greenglade]

Evening all

only 3 pictures for tonight as most of this week's work is just a repeat, in this case, the steam chest bores. Before machining anything I double checked the centre position as it looked a little off if just using a bung to line it up. As it turns out, it was, what I mean is, if I followed the cast bore, the steamchest centre would have been more than the 1 1/2" out from the flange, not by much but best to keep the dimensions as per drawing. Its distance from the middle of the main bore was ok, I first clocked the main bore centre and then moved the cross slide out by IIRC 1.656 and it was within a few thou, so I kept it at that. The important measurements all added up, main bore centre is 1 1/4" out from the flange, steam chest is 1 1/2" out from the flange, it's also 15/16 down from the top edge and the main bore is a further 1 21/32 down from that so I think/hope everything is where it should be.
Ok, so the pictures, first is just to show my set up for reaming as I don't think that I showed it before. I had to start with the reamer tongue held further into the chuck and got close enough to the other side, I could engage the live centre, undo the chuck, move the slide further from the chuck and retighten the chuck and then run the cylinder back and forth over the reamer. A bit Heath Robinson but it worked ok with no mishaps. The picture shows the final stage.

 

I've included this picture taken after the final stages to show the difference between the outside cylinders when compared with the misshapen middle cylinder, there is very little inside the steam chest bore to clean up here.

 

To complete tonight's pictures here's the two cylinders hung on the frames showing both chests now machined...

 

Next week I'll use the mill and a boring head to clean up the rear inner faces of the main bores (as I did with the middle cylinder), check their depth and then finish the front faces, steam chest faces are to size although I may tidy them up a little to make them look more central to the outer casing. It was a tough call to not follow the cast centre's, one always asks questions as to whether they have made a mistake, after making numerous checks I ignored it and carried on, hopefully, I got it right, the figures say so...

Thanks for looking in all..

Pete

 

[greenglade]

good day all

Continuing on from last week, today I machined the rear inner face of the R/H cylinder, I also cut the internal chamfer and begun to lap the bore. Before showing these I did a few more checks on the measurements mentioned last update  as I hate it when things don't add up. I have checked everything and can't see why the steam chest cast seemed to stick out further than it should do?The only thing that could do this would be if the flange was too thick but it's exactly 4mm as to Don's words. The measurements from said flange are also correct so it's a bit of a mystery, I did consider that perhaps Don had drawn the wrong dimension, many have but it would be very unusual for Don Young. I put some 7/8 bar through each steam chest when fitted to the frames  to see how things line up with the expansion link, it looks as it should do? So, I have moved on, it seems right and if not I can work around it easy enough later, however, I don't think that it will come to that as I'm 99% happy that all is ok.

Ok, so on to today's effort, this has all been covered before in the middle cylinder description but basically, the cylinder is held against the angle, squared up and the boring head fitted. I have used the same tool as before, IE the one that I shaped from 1/2" BMS, which had a approx 3" length reduced so that the angled tip could cut both the inner face and also the chamfer into the bore. The first picture shows the tool in question, BTW after shaping it was hardened/tempered.

 

the end result, this was done in two passes, starting from the middle out, had to be done in two as there was a fair bit of material to remove. The chamfer which can't be seen from this angle is just under 1/8 deep which is the distance that the tip sticks out from the tool shaft. Basically, I keep cutting and checking with some paper placed down the bore between the tool shaft to ensure that I don't touch the bore with the shaft.

 

On to the lapping, for this, I have used 'timesaver', the 'Yellow' tub which is designed for brass, Bronze etc. I have used the very thin paste as the bores aren't too bad, to begin with. This comes in a powder which you mix with oil, type of oil isn't stipulated so I just used mineral oil. The picture shows the tub and a small amount that I mixed ready to apply, I did this with a small brush, both in the bore and onto the honing pads that I had modified for the job.

 

this is what I used to hone the bores, it's a small brake/clutch cylinder honing tool, I have covered up the pads with some tough paper towel and soaked them in the solution, as you can see I have already used the tool in this picture.

 

The tool in action, I varied the speed and kept the action up/down the bore constant and smooth, reapplying more solution as I progressed.

 

Lastly, the finished bore, I have tried to tilt it to get the light to show the result, it's not as polished as the burnished effect but then it wouldn't be, I think it's good enough, once I have made the pistons/rods and the 'O' rings have arrived I'll be able to test it.

 

Tomorrow I'll tackle the other side and then take a look at finishing the front face, I'm in two minds about how best to tackle this as a knife edge face cutter ( as used for the first stage) can't do the full job, I may just use a suitable cutter and machine the whole face on the mill, I'll give this some thought overnight.

thanks for looking..

Pete


 

[greenglade]

It looks like this end of week's update is going to be a little bigger than of late so I'll do it in two parts to safe my sanity at the keyboard.

This picture shows the last stage of lapping the cylinders, luckily last week I had cut down some of my apple tree and have now used a small section for lapping the cylinder. This was turned to a good fit within the cylinder, I then mixed up some more of the cutting compound and slid each cylinder in turn onto the wood and worked them by hand. They were a tight fit to begin but soon loosened up, each now measures 1.7455 so I've gained another thou and a half which is good enough for me. It didn't take long as all I'm doing is removing any high points from machining.

 

I now move on to the cylinder covers, these come as cast discs including a spigot with the cylinders. First job was to true up the spigots, for this, I used the outside jaws and held the cast in the most concentric position. I then refitted the internal jaws and machined the front face, the picture shows one of the covers having had it's face machined and the other with just the spigot done awaiting it's turn. I do each cast in turn for each operation, makes things much quicker.

 

Then on to the rear face, as with the middle cylinder, I have added an internal spigot to fit the bore to help locate the cover for when transferring the mounting holes, this will be removed once the cover has had it's holes drilled and been mounted to the cylinder. the cover hear is still oversize so i wasn't worried about marking it in the jaws.

 

Now to the front and here I have deviated from how the middle is as I want them to look like the prototype including the cosmetic covers that sit over the studs. I have made 3 changes although one may not be needed now that I've looked closer at the cover in relation to it's fit on the cylinder. Perhaps Don covers this later, but I've not found it. IIRC, Don states that the covers are 5/32 thick to give a scale appearance, on looking at my reference photo's this doesn't really work out, it's too thick for just the cover without it's outer shield and too thin to be both, well that's how it looks to me at least. So I have reduced it's thickness down to nearly half, I have also added a small step around the outer edge, the idea for this was to give a register for the shield but on further investigation, this may not be required. The third difference is I have added a central blind hole tapped 6BA to secure the shield as per prototype. 
Here's a photo of the full size that I took to show what I mean..although today the shields are painted black, for my era they are polished steel, I haven't decided how I'm going to make these yet, they could be spun or machined from solid, the material that I use will have some bearing on which method I choose.

 

here's the front so far, you may just be able to see a scored line half way across it's face, this will be explained in the next picture.

 

And here we have the cover put roughly in place and we can see why I scored a line. The cover will be closer to the steam chest once it's had a small section removed to allow for this. I need to make two mirrored covers as they are handed to fit the cylinders. The scored line is to give me a vertical register for placing the holes, the first to the right will be on a 15-degree arc, the first to the left will be on a 30-degree arc and all other after will also be on 30 degrees. You can see clearly in this picture that the steam chest bore as stated previously isn't central to the cast, why? I have no idea. However, the last picture after this one did put my mind more at ease.

 

As an added check, I do this a lot, I measured across the face of both cylinders to see how the cover would look. The cover dia is 1 1/4" and you can see that when placed centrally to the bored hole this will fit nicely in line with the lower edge so I don't think that the hole can really be out, very strange but I'm not going to let it worry me. I'll make the covers to size, fit them and then look at profiling the casting to match, it's strange as there should be no reason to touch this part of the casting and it should be to size which it clearly isn't? The important thing is that the dimensions are correct so no problem.. yeh right, if only my mind would let me drop it...lol

 

Tomorrow, all being well, I'll set up the rotary table and plot/drill the mounting holes, I'll also drill/tap the relief valve hole and machine the small section off for the cover to clear the steam chest and sit nicely in their respective bores.

Till then

Pete


 

[greenglade]

Evening all, time for this week's final update and I found an error in Don's drawing on the front outside covers, the problem is I didn't spot it until I had machined them. Also, I'm not sure, but Don may have mentioned it later after having it pointed out to him by a builder, at least I have some recollection of this, I think?

So, what have I done now?....here's the drawing, it has my pen notes for the degrees of each hole, I did this as they are handed and I didn't want to get confused during the operation. The few outer numbers are for the other side, this one is for the L/H cylinder or right hand as you look at it from the front. There, that should give some an idea of the error which I didn't spot?

 

maybe this picture may help, here's the same cover after machining, placed over the bore. The error is that the relief valve hole should be outboard, not inboard as seen here, oh and yes, I did both covers before trial fitting them..lol

 

No big deal other than having to reset each cover on the rotary table and drill/tap the two 7/32x40tpi holes again in their correct positions, here we now have both covers with two holes, just not what the doctor ordered. I don't have any bronze hex to hand so will need to get some to plug the holes but I had another idea which some may be able to answer, where would one fit a connection for measuring 'Cylinder pressure'? I had thought about fitting such a gauge before but now I may just do it due to my not paying enough attention, or more to the point, forgetting what I think Don had already warned about.

 

Next week I'll finish off the bore face, I've already made a start on one, the bore is still a little overlength but I may leave it for now as extra clearance. Once i have the pistons and rods made and some of the other motion I can check to see if the stroke as it should be.

Thanks for looking in again chaps/chapesses

Pete

Read more: http://modeleng.proboards.com/thread/5733/building-don-youngs-doncaster?page=143#ixzz5k9Pul0hY

[mswjr]

Dont worry Pete, we all have had similar,Some drgs are real naff. On mine to day i decided to fit the finished eccentric rods to the links, All built to the drawings before hand,The last bit before testing on air,Well the links were 1/4 wide and the eccentric forks were 5/16 wide, not happy, more extra work now, guess i should of cross checked ,but took the drgs to be correct.  Keep the pictures coming , your not hanging about.