"The GER crank axle workshop".

[iploffy]

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

Nice one Mick, Just tell em' what Stanier said when they put the upturned coffee pot on top of one of his LMS designed loco's

 

[mickoo]

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

Well you learn something new everyday round here! Makes sense as right angle joins are sources for cracks so a fillet will relieve stresses in these areas, had a scour through my photos and noted fillets on all bearing surfaces, be it axle box or coupling rods, internal and external, the only join machined to a right angle I could find was on a Britannia intermediate crank pin where it joins the wheel all other crank pins were filleted.

 

[Locomodels]

Makes sense as right angle joins are sources for cracks so a fillet will relieve stresses in these areas,

Absolutely right, and the radius takes side loads and stops the con rod moving sideways to rub on the crank web.
Some years ago a couple of Spitfires had crankshaft problems, they broke! One was, I believe, in the aircraft owned by Charles Church. The AAIB of the CAA investigated and attributed it to one particular engine rebuilder having ground the crankshaft with too small a radius in the corners. And, as you say, the crack propogated from there. All these engines were grounded until the crankshafts were checked and sorted. At that time I was involved with Spitfire PV202, a two seater, and we had to obtain another Merlin, unfortunately the only one available was a Type 266, and the aircraft had originally been fitted with a Type 66. You would not believe the amount of work required to make the changes needed. However I digress, apologies.

 

[Dog Star]

Spitfires... aaahh.

Sigh for a Merlin.

Do not apologise, digress - the biggest difficulty will be choosing a name for the new thread.

 

[mickoo]

Absolutely right, and the radius takes side loads and stops the con rod moving sideways to rub on the crank web.
Some years ago a couple of Spitfires had crankshaft problems, they broke! One was, I believe, in the aircraft owned by Charles Church. The AAIB of the CAA investigated and attributed it to one particular engine rebuilder having ground the crankshaft with too small a radius in the corners. And, as you say, the crack propogated from there. All these engines were grounded until the crankshafts were checked and sorted. At that time I was involved with Spitfire PV202, a two seater, and we had to obtain another Merlin, unfortunately the only one available was a Type 266, and the aircraft had originally been fitted with a Type 66. You would not believe the amount of work required to make the changes needed. However I digress, apologies.

Not at all, a 2 seater, ML407 is based near me now (RAF Bentwaters) and I regularly see her flying around, you can't beat the sound of a Merlin in the air! Just bloody gorgeous.

Regarding replacement parts, can't be as bad as Siemens and their PLC components, an updated part with just one letter difference often requires a complete program change, identical part except some internal thingy and your days gone to pot, plug and pray we call it!

Back to con rod pin, why then is the Britannia not radius it quite clearly looks like a non radius machining so I presume a big washer is inserted in there?

Copyright, Nigel Frazer Kerr http://fraserker.com/britannia/

 

[Dog Star]

Back to con rod pin, why then is the Britannia not radius it quite clearly looks like a non radius machining so I presume a big washer is inserted in there?

A photo of the rear of the coupling rod might reveal all. I suspect that there is a bronze lip to the bearing carrier and the whitemetal of the bearing is carried "round the corner" of the carrier and over the lip. Hence there is a whitemetal thrust face on the rear of the coupling rod boss.

Having said that, the actual pin does look to have a run-out radius which is inside of the wheel boss, almost as if the crank pin has been pushed too far into the wheel.

regards, Graham

 

[mickoo]

Graham, there is clearly a bevelled edge to the coupling rod intermediate bearing and it does look like it extends and forms a thrust bearing surface.

 

[Dog Star]

Well, there you go, you knew the answer before asking the question.

Always appreciate a good photo of the brutish side of British engineering, especially when the subject is something from the railways.

 

[mickoo]

Well yes and no, still does not explain why the crank pin has no fillet, there is space for it on the rod bush but no corresponding fillet on the pin, even if the pin is partially pushed in as you suggest, there still is not enough fillet to fill that bevel on the rod bush and this pin of all pins you would expect to have the largest fillet as it transmits the largest forces furthest from its fulcrum point.

 

[Locomodels]

Well yes and no, still does not explain why the crank pin has no fillet, there is space for it on the rod bush but no corresponding fillet on the pin, even if the pin is partially pushed in as you suggest, there still is not enough fillet to fill that bevel on the rod bush and this pin of all pins you would expect to have the largest fillet as it transmits the largest forces furthest from its fulcrum point.

Possibly because the pin is not reduced in diameter, it just looks very tired and worn. The thrust face of the bearing is as Graham said, actually bearing on the wheel boss face, so the chamfer is probably to stop a sharp edge getting damaged and stop it picking up. It is fairly common to chamfer holes on plain for that reason. Probably helps any lubricant get to the thrust face as well, even though there would be no great side thrust force anyway.

 

[Locomodels]

As you will have noticed I did not get to finish this off during the week. As my workshop is getting on for a quarter of a mile away from the house, damp cold evenings are not conducive to going for a walk and driving is just too lazy for words.

So as it is Sunday I made for the workshop to continue the job in hand.

The webs are assembled in pairs, using the Slater’s axle to align them, and a spacer of the correct width, which was machined to suit. Then clamped together and soldered, using soft solder and a small flame. The flux is the non toxic one from Christian Cresswell at ‘Building O Gauge On Line’. This is now the only flux that I use as it seems suited to everything and works every time.

To help the solder to flow into the joint I very slightly countersink the webs on each side, just by a couple of thou or so. At this stage I also drilled for the cross pins and tapped the pins home.

Here are some shots of the process.

Firstly my soldering set-up using toolmakers clamps, with one pair of webs soldered and the small gas torch that I use. It only takes seconds for the solder to flow with this needle point flame. It is using Butane.





Next drilling the cross holes in the mill. Firstly it is important to start with a nice sharp drill and then keep relieving the drill by withdrawing it from the hole. Also cooling and lubrication are important, so the drill is sprayed each time it is clear of the hole. This is a somewhat delicate process and requires a sensitive feel on the drill quill. In this instance it was possible for me to feel the change from PGMS to the 4130 metal of the web. Here you can see the swarf that has clung round the top of the hole.



OK off home now for lunch and to clean up the web pairs before assembling the whole axle. Back soon.

 

[mickoo]

Is that a Soba vice you have there, looks like the 1½" version? They do look very good quality, ARC Eurotrade do a nice 25mm one with a rebate in the top of the jaws for holding very small stuff.

Regarding your workshop and distance, perhaps the perfect excuse for a 2½" or 5" gauge railway?

 

[Locomodels]

Is that a Soba vice you have there, looks like the 1½" version? They do look very good quality, ARC Eurotrade do a nice 25mm one with a rebate in the top of the jaws for holding very small stuff.

Regarding your workshop and distance, perhaps the perfect excuse for a 2½" or 5" gauge railway?

Hi Mikoo,

Sorry I cannot remember if it is a Soba vice, but it certainly came from ArcEuroTrade. It is a super vice but sometimes it is difficult to hold things in place and tighten the vice with an Allen key.

As to a larger railway, I would love one, having built a 71/4" 1400 loco some years ago. Sold it when we changed countries. But I do have plans for one when we move into the watermill. However it would be difficult here as the house and workshop are on opposite sides of the village. The track would have to cross one road and negotiate a roundabout. Interesting but the Mairie might have something to say about it.

Just home for dinner, back to the bench now to finish the axle off.

 

[mickoo]

Hi Mikoo,

Sorry I cannot remember if it is a Soba vice, but it certainly came from ArcEuroTrade. It is a super vice but sometimes it is difficult to hold things in place and tighten the vice with an Allen key.

As to a larger railway, I would love one, having built a 71/4" 1400 loco some years ago. Sold it when we changed countries. But I do have plans for one when we move into the watermill. However it would be difficult here as the house and workshop are on opposite sides of the village. The track would have to cross one road and negotiate a roundabout. Interesting but the Mairie might have something to say about it.

Just home for dinner, back to the bench now to finish the axle off.

Paul, ohh that sort of ¼ mile LOL, not bottom of the garden sort!

Regarding the vice, have you considered a cut off Allen key, the long end retained and jam that in a small file handle, just for the initial nipping up? One/two is/are certainly on my purchase list shortly.

 

[Locomodels]

Well here we are again, next and final installment.

Now here is the axle being set up in Vee blocks. These are lined up by eye, with the help of a square. Slaters wheels are set diagonally to the crank-pin centre line.





Next I cross drilled them and pushed the pins in before soldering the whole thing up.

After some cleaning up, of the excess solder, we come to the last operation, milling away the axle between the webs. This is a 2mm dia cutter so easy does it. At just 10thou a time, that is 19 cuts, then step it over 10 thou and repeat. Then again for the other side.




And here is the finished item.



Well that completes the amusement for the moment, the next job is drilling and tapping the con-rods 14BA. Then cutting the cap off, bolting it back on after truing the joint, and drilling and reaming to fit the crank pins.

This crank axle took me about 8 or 9 hours in total, not bad for something that is hardly visible when fitted. Still it keeps me off the streets.

 

[Locomodels]

Here is the next job, probably for next weekend. Though I will probably have to increase the thickness of the boss first.

 

[Eastsidepilot]

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?

All done in the lathe Paul,
First off is bore and ream the centre of the round bar 3.9mm the length of the whole crank axle for the stub axles that will be fitted to the wheels, then turn the first axle to finish dia. and length, next turn the bar down to the outside dia. of the webs and the width of the two webs plus the crank pin.
The bar is now re-chucked off set on one of the jaws, with some packing, by enough to give the crank throw dimension( in this case 7mm, then with caution take very ,very light cuts as the bar comes round to meet the cutter you have chosen to cut the crank pin, I keep going until I can see and hear that the crank pin is being cut all round, stop the lathe, measure the dia. of the pin and reduce by the required amount ( in this case down to 3/16" dia.)
We now have a round bar with one axle, one circular web and a crank pin turn on the end.
So next job is to turn down the other end of the crank axle, if great care is taken it can be done with the bar re-chucked back centraly in the 3-jaw and then cut off in the vice, over length, and the end cleaned up in the lathe.
The alternative would be to cut the incomplete crank off the bar to rough length, and re -chuck on the turned axle with a 5/32" rod pushed through it ( so the jaws don't distort the hollow axle) and then finish turning the other end of the crank axle.

You now have a solid turned crank axle with circular webs, and a lot of swarf, I cut these to shape by marking round a plastic pattern and cutting and cleaning up by hand, the wheels can be quatered for the taper pins in a jig.

I hope that makes sense, it would probably be easier with pic's perhaps I'll do so on the next one I make and post it on my work bench post.

ATB, Col.

 

[Steph Dale]

I hope that makes sense, it would probably be easier with pic's perhaps I'll do so on the next one I make and post it on my work bench post.

ATB, Col.

Yes please Col!

Steph

 

[Dog Star]

Looks like Col. has been going round in "Ever decreasing circles".

 

[Locomodels]

Here is the next job, probably for next weekend. Though I will probably have to increase the thickness of the boss first.




As I said the next job was to make the connecting rods.

Ever since I first tried laminating motion parts I have absolutely hated it. So my first new year’s resolution is to make patterns and mill the things myself. After all that is why I got the Taylor-Hobson in the first place. Not specifically for motion as there are so many parts one can make on it.

However for this one I persevered and soldered and filed the things up.

But remember these two connecting rods need to be cut in order to fit them to the crank pins.

The method was absolutely straight forward. File up the rod and finish it nicely with the wet-or-dry, spot and drill through the cap and rod before cutting in two. At this point I actually tapped the hole 14BA, it is a stopped hole so care was needed. When this was done I marked the join and cut it with a very fine piercing saw, 6 0’s.

Once cut I flatted the joint faces, very carefully, with files and wet-or-dry of various grades, on plate glass. Next thing was to drill the cap a clearance size for the 14BA screws. I wanted a nice snug fit so I measured the o/d of the screw with a mic and used the nearest size drill that I had to suit. I didn’t do this on the drill but by hand with a pin chuck as there was so little to come out.

I then fitted the cap with two long screws, running the screws until they bottomed out in the holes, having first run a nut up each bolt. These nuts were then tightened down on the cap. Out with the piercing saw again and gut off the bolt heads a couple of threads above the nuts. Remove the nuts and cap and remove the burrs from the cut threads and file up the ends. Refit the cap and tighten down the nuts.

Now having cut right through the bearing hole you of course end up with a sort of elliptical hole. So out with the rat tail file and get it somewhere near circular. Then proceed to open it up with drills of increasing sizes, finally reaming it, 1/8” dia in this case. Lightly chamfer the edges and job done.

Well almost, in full size the nuts are castellated for cotter pins. Now I have no intention of fitting cotters but thought that the nuts should have the slots. So I cut them with, you guessed it, the piercing saw.





The drawings actually show the nuts turned to the a/f diameter where castellated. These nuts are 2mm a/f so I have ordered some hex section brass from Finney and Smith and will make some new nuts. Probably not fitting them to the inside motion, but just to the outside connecting rods.




Hope you like the pictures. I really must get round to turning the wheels to S7 profile sometime.