"The GER crank axle workshop".

[Locomodels]

This is probably going to be a long, tedious and boreing description of how I build crank axles. This is just my method, there are, no doubt, several better ways to go about it. So, as I know many of you build your own axles, if and when my method differs from yours, please let us know. It might help me to build better axles. Even if you have never built one, but think that there are better techniques, let us know your thoughts. One never stops learning.

The very first thing to do, of course, is your research and few things are better than having a works GA drawing available. Which I am fortunate enough to have for this loco. Anyhow GA’s are always wonderful to look at and just enjoy, so definitely worth any costs involved.

OK we have the details, have decided on any compromises necessary and are ready to go.

So to start at the beginning, we cut out the webs. Mine were done on my pantograph mill. Now I know several of you have these beasts so you can skip this bit. For those of you who may not recognise one if you walked into it, here are some pictures. There are several different makes and each make comes in several different sizes. For the record mine is a Taylor-Hobson JH, this is the largest that they made and as you can see it is some 4’6” high, 2’0” wide and about 4’0” deep, so you need quite a lot of space for one and, preferably a reinforced floor, as it is bl**dy heavy. Probably four or five hundredweight. She is getting on a bit now as she is 56 years old, now I know that it is un-gentlemanly to mention a lady’s age, but she is a tough old bird and will certainly see me out.

 

[Locomodels]

Now before we can begin the milling we have to have a pattern for the machine to follow. The pantograph is capable of being set to almost any ratio from 1:1 to 50:1
However for this type of work I find that 3:1 and 5:1 are generally of most use. For small components 5:1 works very well and this was used for the webs.

Here is a shot of the plastikard pattern mounted on the copy table. The roller on the stylus touching the pattern is the follower and also has to be made to the same ratio for the cutter diameter, this one is 10mm dia. for a 2mm cutter. This pattern is made from 50 thou Plastikard and cut out with a piercing saw, cleaned up with a file before sticking it to another piece of plastikard with double sided tape. The edge of the pattern has to be really smooth so that the follower can glide round it.



Now here are some webs that I made earlier, didn’t you know that I used to work for ‘Blue Peter’? They are cut from 12swg Chrome Molybedenum steel. Mild steel would have been fine but I didn’t have any, it would have been much easier to cut too and kinder on the cutters. This machine has eight speeds going from fast, at 3.000rpm to extremely fast at 18,000rpm, I settled for 11,000 for this job.
So why didn’t I go and buy some mild steel sheet ? Have you ever tried getting Imperial size SWG material in France. No I thought not, so there you have your answer. All self inflicted I admit, but I am stuck with it. The up side is wandering round to the village store and getting a nice bottle of Claret or Burgundy for a few Euros. So it isn’t all bad.



View attachment 16330

Due to the small size of the cutters and as I was cutting steel, the depth of cut was only 10 thou. This meant that I had to go round the pattern eleven times, 12 swg is 0”.104, lowering the cutter ( actually I raised the table) each time I passed GO.
After they have been cut I draw file them to remove any machining marks.



Stage two is to drill and ream the axle and crank pin holes. This was done on my Austrian ‘Emco’ Mentor mill, which has a drilling quill making life much easier. However a jig is also needed for this, I use the one that I made for drilling the crank pin holes in cast iron wheels. It is extremely simple as you can see, simple is always best. I drilled them in pairs, and kept them as pairs, just in case there were any errors that might have crept in.





The next stage is a quite delicate one, drilling for the pins. For this I would normally have used nickel silver wire, but as I did not have any of a suitable size, used 18 swg brass in stead. It doesn’t make any difference anyway as you can’t see the brass under the paint!

(‘Dog Star’, my researcher, has told me that the LNWR left machined components bright, so no camouflaging the brass pins this time.)

The webs were centre punched, held in a machine vice, clamped to the mill table, and drilled 1.2mm into the crank pin and axle holes. I had a dummy crank pin in place, to stop the risk of the drill breaking as it broke through into the hole. This was done for both the crank pin and the axle and only into the hole, not all the way through. This will be done later.



Next I turned the crank pins, these were made from 5/32” dia. PGMS (precision ground mild steel) which is very free cutting. These are reduced in diameter, to 1/8”, for the pin on which the connecting rods run. This is under scale, the originals were 8” diameter (4.66mm) but as you have to fit the conrods with caps, you need to have room for the 14BA bolts, so that is where I cheated a little.

As I had not taken any pictures whilst making this axle, it was going to be a little difficult to show you what I did, So this morning I started another one at about 11 o’clock so, with lunch and dinner breaks plus other interruptions, that is as far as I managed to get today. Only the final assembly, milling out the axle between the webs and cleaning up to go. That should be do able in one evening session so maybe I will continue the saga tomorrow.

 

[Dog Star]

Possibly the most exciting thread on WT for yonks... thank you Paul. So are you building two Claughtons? Or was the first axle a dry run? Or do you have a cunning plan to convert Richard to the true gauge?

 

[adrian]

Is there a specific reason why you made the crankpins from 5/32" bar and turned down the centre section to 1/8"? I would have thought that it would have been easier to drill and ream the web 1/8" and have a plain crankpin. The reason I ask is that I'm curious how you managed to get a good finish on the centre section on the crankpin.

 

[Dikitriki]

Great thread, thank you.

I have a Taylor Hobson pantograph miller that I'm looking forward to using, so this is a very timely thread.

It appears that you haven't drilled the cranks right the way through for the pins. Can you explain why please?

Richard

 

[Locomodels]

Is there a specific reason why you made the crankpins from 5/32" bar and turned down the centre section to 1/8"? I would have thought that it would have been easier to drill and ream the web 1/8" and have a plain crankpin. The reason I ask is that I'm curious how you managed to get a good finish on the centre section on the crankpin.

It was just that there is more metal for the cross pin to go into. I felt that 1/8" was rather small.
The finish was not a problem, I used a specially ground round nose tool and polished it with wet-or-dry on a stick.

 

[Locomodels]

Great thread, thank you.

I have a Taylor Hobson pantograph miller that I'm looking forward to using, so this is a very timely thread.

It appears that you haven't drilled the cranks right the way through for the pins. Can you explain why please?

Richard

They get drilled through when it is soldered together, then the pins are driven home and soldered.

 

[Locomodels]

Possibly the most exciting thread on WT for yonks... thank you Paul. So are you building two Claughtons? Or was the first axle a dry run? Or do you have a cunning plan to convert Richard to the true gauge?

No the Claughton one is finished as you know, this is for a Stanier Pacific. It won't be built for some time yet though.
But, as I said, I had not taken any pictures, so it was killing two birds with one stone.

Oh and I wouldn't exactly call it exciting, you must just lead a dull life !

 

[Dog Star]

... this is for a Stanier Pacific. It won't be built for some time yet though.

You do seem to be moving away from the true path, what has happened to Adams?

...you must just lead a dull life !

Pardon?

 

[adrian]

It was just that there is more metal for the cross pin to go into. I felt that 1/8" was rather small.
The finish was not a problem, I used a specially ground round nose tool and polished it with wet-or-dry on a stick.

Cheers - though a photo of the round nose tool would be of interest to me! I was thinking you'd be using something like a parting off tool hence the query about getting a good finish.

 

[Locomodels]

Cheers - though a photo of the round nose tool would be of interest to me! I was thinking you'd be using something like a parting off tool hence the query about getting a good finish.

The cutter is exactly that, a parting tool that I ground round corners on, in fact it is now semicircular.

 

[Locomodels]

You do seem to be moving away from the true path, what has happened to Adams?

It is a very winding path but Adams does feature prominently along it.

Pardon?

I just can't believe that this could be called exciting, boring more like.

 

[Locomodels]

Cheers - though a photo of the round nose tool would be of interest to me! I was thinking you'd be using something like a parting off tool hence the query about getting a good finish.

Adrian,
Here are a couple of photos of the tool that I used.

 

[Eastsidepilot]

Nice work Paul, I have a Taylor Hobson model 'K' which I now find invaluable.
Your method of producing crank axles especially for Slater's type axles is ideal, I have been turning some LNWR 'A' class cranks, for telescopic axles, from 1" round bar which is probably not as economical I must admit.
ATB, Col.

 

[mickoo]

You do seem to be moving away from the true path, what has happened to Adams?

Splutter, there is only one path, that trod by Stanier himself, one which all disciples must follow, they may tread other paths before hand, but must accept that they will end at this path in due course.

 

[mickoo]

Adrian,
Here are a couple of photos of the tool that I used.

View attachment 16394View attachment 16395

Paul, I accept that the round tip gives the best finish (not that I can technically explain or understand) but how does it finish off in the recesses, surely that will have a curved fillet that must be accounted for on any fittings applied to the shaft?

 

[Dog Star]

Splutter, there is only one path, that trod by Stanier himself, one which all disciples must follow, they may tread other paths before hand, but must accept that they will end at this path in due course.

Fine, just as long as you and Dikitriki remember where Stanier did his training.

 

[mickoo]

Fine, just as long as you and Dikitriki remember where Stanier did his training.

Ohh I have no illusions as to Churchwards contibutions to modern British steam engine and the Castles are very fine locos indeed, but Stainer took it one step further IMHO. Note also to balance the score sheet, Gresleys work on the A1 only leapt ahead after many discussions, probably over dinner, with Andre Chapelon who is rightly accredited with some of the finest steam passages and steam managment the world has ever seen.

Swindon had the chance after seeing Gresleys and Staniers work to evolve as well, they chose not to and perhaps robbed the UK of some outstanding machines

 

[Locomodels]

Paul, I accept that the round tip gives the best finish (not that I can technically explain or understand) but how does it finish off in the recesses, surely that will have a curved fillet that must be accounted for on any fittings applied to the shaft?

Exactly, just like the real crank pin. The con rod bore matches this.

 

[Locomodels]

Nice work Paul, I have a Taylor Hobson model 'K' which I now find invaluable.
Your method of producing crank axles especially for Slater's type axles is ideal, I have been turning some LNWR 'A' class cranks, for telescopic axles, from 1" round bar which is probably not as economical I must admit.View attachment 16398View attachment 16399
ATB, Col.

Thank you .

Nice work, that is the proper way to do it, no need for soldering and cross pins. But quite a lot of work, milling as well, did you make a fixture to turn the crank pin?