Building Don Young's Doncaster

[ettingtonliam]

Dec 21, 2020 10:01:01 GMT @greenglade said:

A little more info re-weighing

Even though the figures given in the measuring of the axles in my latest blog entry made sense, that is the total figure and differences between the axles looked correct and I got the same readings from 3 measuring sessions my head was still having trouble accepting the figures. My reasoning for questioning the process was that even when measuring each axle independently I was having trouble accepting that this would give the actual loading weight on each axle as surely some of the weight was still being supported by the rest of the chassis and all I was achieving measuring each axle was the weight of that mass plus any parts attached, not the actual axle loading? I, therefore, asked the guys who really know the subject, that is those who work on the full size for how they weigh the old lady.
It is basically the same, they fit the scales in the pit and measure each axle, actually, they measure each wheel, I can do that too but didn't see the need at this stage of the build. Once all wheels have been weighed, they run the engine for a hundred yards or so and remeasure, just as I did when rolling the chassis along the track. The difference here though is that I got the same figures each time, I'm told that with the full size the readings change and then have to be redone, again and again, the word tedious was used...
Adjustment, of course, is done by adjusting the springs until they measure the correct tonnage. As stated in my blog, I know what the percentages were in full size and will use these on the final setting up of the model when complete. IIRC the percentages were changed after first built to even out the main drivers at 20 tons each rather than having more weight on the leading driver. I'll see what works best when I get there.

Pete

According to the late Eric Langridge, there were difficlties in accuratly weighing the BR 4 6 2s, and he gives a table of weights, for 72001, empety, full boiler, 1/2 glass water, then drove it a litte way, over some nuts on the rails to shake the springs up a little, and finally after the springs had been given a good hammering! Noticeable differences could be seen.

[Deleted]

[quote author="ettingtonliam" source="/post/197718/thread" According to the late Eric Langridge, there were difficlties in accuratly weighing the BR 4 6 2s, and he gives a table of weights, for 72001, empety, full boiler, 1/2 glass water, then drove it a litte way, over some nuts on the rails to shake the springs up a little, and finally after the springs had been given a good hammering! Noticeable differences could be seen.
[/quote]

Yes, it seems that striving and then maintaining complete accuracy in weight is fruitless....I can understand why things change once running...trying to get sprung weights on so many axles allowing for settling each time would be as I've been told a tedious task. Cars are the same, first pothole or kerb and that expensive 4 wheel alignment you just spent a fortune on is out the window.. I'll get it as close as I can, I think the model will be much easier than full size...

Pete

[Deleted]

[terrier060]

That is looking really like a loco now. Will be great to see it running!
Ed

[61962]

Dec 22, 2020 18:15:20 GMT @greenglade said:

Hi Guys

I have noted on here lately how my son and my son-in-law have been supplying me with some metal stock and cutters etc as their work closes down, I've had an awful lot of gear to date. My son-in-law dropped off some more pieces on two separate occasions over the last couple of weeks. Last week was some steel, alloy and some nylon 66 bar along with some clear acrylic, I'm sure that I'll find a job for them, if anyone needs anything like these and is close by, let me know and I'll see what I have, after covid lockdown, of course. Today there was some more steel including two large sections of flat bar. On checking the label and the BS code it seems that I have some good quality tool steel/gauge plate, I suppose they are the same thing? The lumps are wrapped in greaseproof paper which is normal for this type of steel. The problem is, how the hell am I going to cut this into manageable sizes? one is metric at 500x250x20mm and the other is imperial at 18x10x3/4 ". I could only just lift these pieces of steel individually.

Any ideas guys/ my chop saw blade is kaput, along with my small bandsaw blade, even with fresh blades neither would be up to this task.

Pete,

Gauge plate is also known as "precision ground stock" or 01 which is silver steel. It's a nickle chrome alloy. In it's annealed condition it isn't much more difficult to cut or machine than mild steel, just needs sharp tooling and lighter cuts. I've just about finished the coupling rods for my H4 in thi alloy steel (the K3 is done in mild steel EN3) and I did all the cutting to length and width reduction with a hand hacksaw. I use Starrett Red Stripe blades (my preference for many years)( there are I believe other makes). Bar the size you have takes me about ten minutes to cut through. Use cutting oil to ease the way as resistance comes from the sides of the blade. My workshop is too small to accommodate power saws of any type, but I like to think that cutting material by hand provides excellent excersize, rather than going jogging. 

On weighing full size locos  I agree with your contacts that weighing with the Kelbus gear is no walk in the park. First you need to find a length of level track. This is an impossibility in the average loco shed. We did 4498/60007 at least twice at Carnforth. The first time with one set of gear. Talking to the people who were in the know, weighing axles individually will give a total weight of the order of 10% over the true weight. This is not a major issue, but makes the adjustment difficult. Later we had three sets so we could weight the driving and coupled axles all at the same time with 10thou clearance of the tyre from the railhead which is difficult to achieve, as when you adjuse one it affects all the others. Friction in the springs and axlebox slides is the enemy so the need to roll the loco up and down for a couple of engine lengths after weighing is a necessity, and inevitable gives a different answer. The loco was eventually weighed at Doncaster works where all the axles are weighed at the same time. With the experience of the weigh house staff the adjusment was done very quickly since they obviously knew what effect making the adjustments had on the other axles which shortens the reiterative process.

As for model locos, IMLEC entries used to be weighed before competing. I don't know what the reason was for this as the result was not a part of the competition, but for those interested in performance analysis, it showed how loco performance could be improved by increasing the adhesive weight, and I was hopeful that some sort of handicapping system could be introduced to counter the advantage that heavily ballasted locos gained. That never happened and weighing was dropped a few years ago. So much for scientific testing. The weighing mechanism comprised an isolated section of track on which the axle being weighed was placed. This section was connected to a weighing device (usually a bathroom scale) by an adjustable length column, and the height of the loaded column was adjusted until it was returned level with the fixed track using a sensitive indicator. The load at this point was the axle weight. With modern digital scales it may not be necessary to have this feature, but I do have in mind that there is no strain without stress and I suspect the height adjustment will still be needed for true accuracy. I also have in mind that household scales are not very accurate. I have three identical scales from the same manufacturer each giving it's own interpretation of the weight of the same object. Mathematically the positiom of the centre of gravity is fixed and can only be changed by adding ballast so the axle weights correctly relate to the CoG. You could locate the CoG by lifting the loco from a single point  and ajusting the lifting point until the loco hangs level. From that you can calculate what relationship between the axle loads gives the best result for maximasing the adhesion without having too little weight on the carrying wheels. That would at least give you a starting point.

All the best for the coming season. Keep up the good work

Eddie

[Deleted]

Hi Eddie

Many thanks for your informative reply, most interesting...

Regarding cutting the steel by hand, not possible for me I'm afraid, I can do light hacksaw cutting but anything more and my body won't do it, too many health issues. I may have found a way of getting the blanks plasma cut, my son informs me that a friend has a CNC plasma cutter which evidently he bought years ago and only used it once...crazy.. and I'm told it cost something like £20k??? We shall see what happens, evidently, he's not very reliable.
Yes, I've had a few responses to my request for info on a FB group, there are a number of ex 4472 crew in this particular group which i was aware off and why I asked the question there. One chap said he has a photo somewhere that he took of 4472 on a weighbridge which shows all of the axle weights. He has shared one picture of 4472 on the weighbridge taken from the control room, but in that pictures the axle readouts are blank, not taking a reading. I can't recall where the picture was taken?
Interesting what you say about IMLEC and weighing the models, I think that this was a good idea and should be used again, some of the entries these days have 1/2" thick running boards which to me is not in the spirit of the competition, just my personal opinion.

Merry Xmas to you and family too..

Pete

[Deleted]

Evening all

I'm currently machining the blanks for the crossheads, a tedious job to say the least. Looking ahead I need to make a decision on the method of fixing the crosshead to its piston rod. Don gives a choice of 2x1/8th taper pins or doing it properly with a 1/8th cotter pin.
Can such pins be bought, what are they called? or do they have to be made and if so are there drawings. I believe that the cotter pin is also tapered?
How have others machined the slot in the crosshead?

Regards

Pete

[don9f]

Hi Pete, on my 9F the crossheads screw onto the piston rods and are secured with a 1/8th taper pin that has a rectangular head silver soldered on....to look like the head of the large flat tapered cotter that should be fitted!
You can just see one in this photo:-



I remember some info on a drawing of the real thing stating that the tapered slot for the cotter was to be broached through the assembled rod/crosshead once a force of 50 tons had been applied to drive them solidly together!

Cheers Don

[Deleted]

Thanks Don, that's a neat idea, I'll give that some thought. My piston rods are 5/16 which would lend themselves to an ME thread. Crossheads are still in an early stage and I could drill them to accept a 5/16 ME thread. It would also make life much easier to set up, something for me to ponder on while I slowly continue with reducing lumps of black steel to size.

Many thanks for sharing...

Pete

[61962]

Hi Pete,

I've done correct cotters on the K3s. It's not easy but it's given me a lot of satisfaction and I'm sure it will be better than any other method I've used. To date the A4 has screwed piston rods, origininally with taper pins across. They eventually became loose over time and tightening the pins ultimately caused one of the piston rods to fracture through the pin hole. The crossheads were bronze so I replaced the ends with steel inserts silver soldered in place with a similar fastening, but with a cross pin scewed in vertically from underneath and whilst that has lasted a long time I am loathe to recommend it, as it's a bit Heath Robinson. My 3 1/2" atlantic has screwed rods and cross taper pins also and has been running for near 40 years without problems. Other than the lower power, the only difference is the A4 has the single slde bar and the atlantic the double slide bars which do give better restraint to the crosshead as the slidebars become worn. My Adams radial also has the single slide bar arrangement. The crosshead is just a plain parallel fit on the piston rod with a cross taper pin. Over 18 years the crosshead have become slack, but the crosshead slippers now have a lot of wear, but not so bad as to affect the operation. Having now done taper fits and flat taper cotters I think the Adams will eventually get the same arrangement.

These LNER type crossheads are a lot of work to maachine and get to look right. Many locos have been built with crosshead that are simlpified, and that is understandable, but I have gone the extra miles to make mine for the K3s as near correct as possible. I did them from the solid, but if you want to save some time you might look at Steam Workshops Doug Hewson range for the Brittania and 9F cast steel crossheads which are pretty much identical with the LNER type. After all the motion parts for these locos and the class 5s were designed at Doncster.

I'll email spome photos of my efforts later.

All the best to you and everyone on the forum. Hope the coming year will get us off the leash and back to running trains

Eddie

[Deleted]

Dec 31, 2020 17:41:39 GMT 61962 said:

Hi Pete,

I've done correct cotters on the K3s. It's not easy but it's given me a lot of satisfaction and I'm sure it will be better than any other method I've used. To date the A4 has screwed piston rods, origininally with taper pins across. They eventually became loose over time and tightening the pins ultimately caused one of the piston rods to fracture through the pin hole. The crossheads were bronze so I replaced the ends with steel inserts silver soldered in place with a similar fastening, but with a cross pin scewed in vertically from underneath and whilst that has lasted a long time I am loathe to recommend it, as it's a bit Heath Robinson. My 3 1/2" atlantic has screwed rods and cross taper pins also and has been running for near 40 years without problems. Other than the lower power, the only difference is the A4 has the single slde bar and the atlantic the double slide bars which do give better restraint to the crosshead as the slidebars become worn. My Adams radial also has the single slide bar arrangement. The crosshead is just a plain parallel fit on the piston rod with a cross taper pin. Over 18 years the crosshead have become slack, but the crosshead slippers now have a lot of wear, but not so bad as to affect the operation. Having now done taper fits and flat taper cotters I think the Adams will eventually get the same arrangement.

These LNER type crossheads are a lot of work to maachine and get to look right. Many locos have been built with crosshead that are simlpified, and that is understandable, but I have gone the extra miles to make mine for the K3s as near correct as possible. I did them from the solid, but if you want to save some time you might look at Steam Workshops Doug Hewson range for the Brittania and 9F cast steel crossheads which are pretty much identical with the LNER type. After all the motion parts for these locos and the class 5s were designed at Doncster.

I'll email spome photos of my efforts later.

All the best to you and everyone on the forum. Hope the coming year will get us off the leash and back to running trains

Eddie

Thank you, Eddie, now you tell me that there are castings out there?.... I'm doing mine from solid too although the slipper will be a replaceable part that the crosshead body will slide into via a slot for alignment/location and there will be two CSK bolts to hold the parts together. I'll use Loctite for extra strength. I've been giving some thought to going the 'threaded rod' way, I do like this although a little concerned to hear of your experience with this method. I like it for a number of reasons, particularly with the ease of setting up, for example, it will be easy to test if the stroke is correct with a threaded rod, if not it's just a matter of screwing in or out to get it right and the pin it after. The trick though will be getting it close enough so that no thread is seen on the rod, I'm thinking of reaming 5/16 dia for a short depth into the crosshead hole and then getting the thread to be hidden within that short section. I like don's method of making the taper pin look like a cotter pin. Things can still change and probably will, right now I'm spending many hours just trying to machine the lumps of steel to size before even starting on profiling the crosshead shape, might take me another week or two for this stage, then I'll have the drop arms to deal with, lots of detail there to fit in.

I look forward to the photos Eddie, once again, many thanks

Happy New year to you sir

Pete

[mbrown]

My Burma Mines loco has "proper" flat cotters although the piston rods are parallel in the crossheads rather than tapered. Admittedly, she hasn't done a lot of running but they are absolutely fine after a dozen or so "outings" on the rolling road and a lengthy track outing.

I did them like this - which is probably not the best way but which worked for me.

When I "took the bumps" to get the piston equally disposed within the cylinder, I marked the rod where it entered the crosshead. Then, with the piston and rod removed from the cylinder, I pushed it into the crosshead, up to the mark, with some medium strength Loctite to keep it firm. It was then set up in the vertical slide, at right angles to the lathe bed and with the crosshead angled at 45 degrees so that a drill in the chuck went through at the correct angle for the cotter. I then drilled two holes at No.53 and opened them out into a slot with a 1/16" slot drill.

I then swivelled the vertical slide on the cross slide by a few degrees (can't remember how many) to suit the angle for the taper cotter, and milled one edge of the slot to the new angle. The angle needs to be fairly shallow so that the cotter wedges home tightly.

I then made up an over-long cotter with about 3/8" excess length at either end. This made it easy to hold and adjust as I carefully filed it little by little to be a good firm fit. When I was satisfied with the fit, I trimmed the length, leaving it longer on the top than the bottom, and drove it home, at which point it extended well below the cross head boss with the top of the cotter looking about right. I then drilled the cotter through the bottom, close to the cross head, and fitted a small split pin as a safety cotter (as in full size - at least on the Talyllyn) so that if the main cotter comes loose it won't disappear altogether. Incidentally, the edges of the cotter are rounded so that they fit snugly into the milled slot.

I made the cotter out of 1/16" gauge plate.

Hope that helps.

Malcolm

[Deleted]

Thanks, Malcolm

I do like the idea of making proper cotters as per the prototype, I guess I'll have to give this a little more thought... I think, but not sure that the LNER cotters may also have a pin through the bottom, I'm sure that Eddie will know.. I can dwell on all this while I machine the crossheads, that gives me plenty of time..

Pete

[barlowworks]

Hi Pete, check out no23mk2's YouTube channel and look out part 55 of his build thread for his take on retaining the piston rods, a bit heart in mouth at times but the end result looks quite good.

Mike

[Deleted]

Thanks Mike...will do tomorrow...fight now in the middle of a family zoom pub quiz...not sure if anyone is still sober though..

[Deleted]

I watched the video, Mike, interesting to watch....thanks for pointing me to it. I don't think that I would follow it per se but I'll probably do something similar in setting up. Many moons ago IIRC both Peter Rich and Don Ashton sent me their methods for setting up TDC which I used for Great Northern, I should still have them in my emails somewhere. I'm not sure that I like the idea of securing crosshead to piston rod with an ordinary 8BA bolt? It probably does the job, just I'm a bit wary of that method. I plan to drill my crossheads off the model and then use that as a guide to drill through the rod once set up, or at least that's the current idea...

Cheers

Pete

[Deleted]

Tonight's update (sorry for the delay, I had a break over Xmas) covers part 1 of the crosshead fabrication. In Don's words, he states that the trickiest part on the whole model was probably the steam sander bodies? well tricky maybe but the crossheads are going to take some time to complete and probably as much work as the coupling rods with their fish bellied profile which included the fluting. Anyway, here's part one which covers getting the blanks ready for profiling.



4472flyingscotsman.co.uk/crossheads-part-1/

Pete

[Deleted]

Part 2 of the crossheads, these parts may take a few more entries before completed, I'll probably throw in the drop links too. In this entry, we have the slipper oilways, gudgeon-pin holes and piston rod hole. A few more changes from Don's drawings.



4472flyingscotsman.co.uk/crossheads-part-2/

Pete

[chris vine]

Hi Pete,

I am sure there are lots of ways to put a long flat slot (with one side tapered) through the thick end of a crosshead, but it cannot be an easy thing to do!
I have seen an old film of the North British Loco Works and there was a few seconds showing this operation being done. The milling cutter looked like a long 1" approx diameter reamer which must have been put into a pilot hole. The trick was that the cutter was held at both ends rigidly, IE in a chuck/collet at the powered end and the "tailstock" end also had a proper bearing to guide the long and flexible cutter.

Ah Ha! I have found it. www.huntleyarchives.com/preview.asp?image=1014200 If you look at 12 mins 28 seconds (on the player timeline, not the original film timeline) there is a really good view of the exact machine. I would say that it is a special, just for the job of machining cotter slots in crossheads (and piston rods at the same time.

Chris.

[Deleted]

Hi Chris

Thanks for sharing that, I love watching these old 'works' videos and hadn't seen this one before. Looks a massive plant, no need for personal exercise if you have to walk the length of that a few times a day. Lots of hand fettling shown in the video...great stuff..

Kind regards

Pete