City of Truro 3440

[flyingfox]

Wonderful work. well done.
regards
Brian B

[Cro]

Thanks Brian,

Your photos were a big help in getting the tool boxes correct!

Adam

[Gary L]

Jan 1, 2021 19:37:36 GMT Cro said:

Hey all,

Mick, I'm glad this is helping someone. Here is a photo of the flared corners which I am yet to solder, I am waiting till I have formed all the beading to help hold it all in place for soldering. It's not a great fit, the kit has turned trumpet shape which doesn't actually match the radius they have bent the sides too so it will take some dressing once fitted to suit.

Untitled by Adam Cro, on Flickr

[Snip]

If it’s not too late Adam, I suggest you dress those trumpet segments before you solder them in place. I remember fettling someone else’s tender a few years back, and it is surprisingly hard to conceal misalignments in plates. Since they are spinnings they will be very malleable, and if they end up as no longer perfect curves it isn’t a problem. I don’t know exactly how the full-size ones would have been formed, but we can be pretty certain it involved some heavy metal bashing and they would not have been spun on a lathe! A few gentle taps with a round mallet might make all the difference.

HTH

Gary

[Cro]

Gary,

I’ve got them the best fit I can without going too far at the moment. The problem is these aren’t spun they are turned so not as malleable as one would like. I could ask the guy who spun my done to try it but I don’t know the dimensions to give him a drawing!

I won’t be fitting these till the beading is done which will be towards the end so there is time. Just finishing the tool tunnel floor right now before fixing the tool boxes in place.

Adam

[Gary L]

Jan 2, 2021 13:50:46 GMT Cro said:

Gary,

I’ve got them the best fit I can without going too far at the moment. The problem is these aren’t spun they are turned so not as malleable as one would like. I could ask the guy who spun my done to try it but I don’t know the dimensions to give him a drawing!

I won’t be fitting these till the beading is done which will be towards the end so there is time. Just finishing the tool tunnel floor right now before fixing the tool boxes in place.

Adam

Ah, that's a different kettle of paint entirely. You could anneal a turning, but it is difficult to catch the right temperature before the item melts! You can bash them to a very limited extent, but cracking is the danger. Being turned they are more likely to be too thick than too thin (and your photo shows this), so fettling the outer face with a file should be easy enough, as long as you can solder the inside face level. Taking material off the inner face will be very difficult, but I assume there will be lap plates there anyway, so maybe not such a problem at all.
Gary

[Cro]

Gary,

You now see my way of thinking! But yes there are lap plates on the inside, I hadn't planned to fit these but they would cover the uneven joint if I am unable to sort it so we will see how that goes.

I have spent today finishing off the tool tunnel, its surprising sometimes how long these little jobs take as its a lot of on off on off to check it all fits right, couple of solders and clean ups and time is gone! I also made the little support for the firing iron tools as I felt it would tie up this 'area' nicely. All that is left to do is fit the stand to the top plate and the tool boxes and then move onto injector valve valves and the boxes that sit in the coal space but I fear tomorrow has been promised as a DIY day so I'll be lucky if I make it out to workshop.

Here you can see I have fitted the base to the tunnel and rivetted this to the front baffle, this required a fill in piece soldered to the end of the channel first. Once this was all assembled I silver soldered it together to help hold its shape and give it some strength for when everything is eventually soft soldered.
Untitled by Adam Cro, on Flickr

Untitled by Adam Cro, on Flickr

Lastly the curly firing iron support, a small bit of taper turning before bending up the support and some careful soldering. I have modelled this up off the drawing I have so I will get one cast as the white bronze we have available is perfect for these sorts of items and I'm sure its something people would love for their tenders.

Untitled by Adam Cro, on Flickr

Right, time to sit in front of the TV with the laptop, wife and dogs and try model up some new parts!

Adam

[dsa]

Not clever enough to do what you do, but clever enough to appreciate outstanding workmanship,

Well done,a most interesting thread.

David

[92220]

Jan 2, 2021 13:50:46 GMT Cro said:

Gary,

I’ve got them the best fit I can without going too far at the moment. The problem is these aren’t spun they are turned so not as malleable as one would like. I could ask the guy who spun my done to try it but I don’t know the dimensions to give him a drawing!

I won’t be fitting these till the beading is done which will be towards the end so there is time. Just finishing the tool tunnel floor right now before fixing the tool boxes in place.

Adam

Hi Adam.

Another way of making the flares is to use a piece of brass tube of the right thickness and press a shaped plunger into it. It would be relatively easy to make up a press tool. You could turn up a punch the correct shape for the INSIDE, then find a piece of hardish thick walled rubber tube that tightly fits around the smaller diameter. That should then be fitted inside another piece of steel tube to support it. The brass tube is then placed inside the rubber tube and the shaped plunger pressed in to depth. You should end up with an exact shaped flared brass tube that can then be cut in quarters. I forgot to say that the outer steel support tube needs to have an integral bottom, to stop the brass tube being pushed on through by the form tool. You may need to try a couple of different rubber tubes to find the best rigidity, but harder rubber is better than softer, to make sure the brass tube forms properly. The rubber will want to expand sideways when the form tool is pressed into the brass tube, but the outer steel case stops it expanding sideways. The integral bottom stops the rubber moving downwards and so the only direction it can move is upwards, around the outside of the form tool. It won't move much but this is a method of forming, quite regularly used for 'one offs'.

Another way of easily making press tools is the use a special casting plaster for making experimental press tools, and mold around the male press tool. I found a company that can supply such plaster, and a wax that can be melted over a roasting dish of water that is just below boiling. The molten wax can then be allowed to cool and harden and becomes a thin sheet which can be formed over the outside of the male press tool, to represent the thickness of the metal being formed. A box is used to hold pour the casting plaster into, and the male press tool, lined with the thin wax coating, is then pushed into the plaster, and then allowed to harden. The wax sheet also acts as a release agent so it can all be separated and you have a perfect shaped female mold. The company says the plaster casting should be good for 10 or even 20 pressings before it starts to degenerate. It is important to have a couple of 1/2" or 12mm silver steel rods to act as guide bars, to suspend in the casting plaster, to ensure they are in perfect alignment. They can be grooved near the bottom to trap them dead vertical, in the hardening plaster.

Bob.

EDIT:   I forgot to say, working out the shape of the internal forming tool is easy. It is the same as the flare on the sides and end of the tender sides. 

[Cro]

Bob,

I quite like that first method, I may play around with that before I have to do the final fit. Thanks for that! I know how much you love your press forming of complicated parts so should have known you’d have a trick up your sleeve.

Adam

[Gary L]

Jan 3, 2021 10:48:12 GMT 92220 said:

Jan 2, 2021 13:50:46 GMT Cro said:

Gary,

I’ve got them the best fit I can without going too far at the moment. The problem is these aren’t spun they are turned so not as malleable as one would like. I could ask the guy who spun my done to try it but I don’t know the dimensions to give him a drawing!

I won’t be fitting these till the beading is done which will be towards the end so there is time. Just finishing the tool tunnel floor right now before fixing the tool boxes in place.

Adam

Hi Adam.

Another way of making the flares is to use a piece of brass tube of the right thickness and press a shaped plunger into it. It would be relatively easy to make up a press tool. You could turn up a punch the correct shape for the INSIDE, then find a piece of hardish thick walled rubber tube that tightly fits around the smaller diameter. That should then be fitted inside another piece of steel tube to support it. The brass tube is then placed inside the rubber tube and the shaped plunger pressed in to depth. You should end up with an exact shaped flared brass tube that can then be cut in quarters. I forgot to say that the outer steel support tube needs to have an integral bottom, to stop the brass tube being pushed on through by the form tool. You may need to try a couple of different rubber tubes to find the best rigidity, but harder rubber is better than softer, to make sure the brass tube forms properly. The rubber will want to expand sideways when the form tool is pressed into the brass tube, but the outer steel case stops it expanding sideways. The integral bottom stops the rubber moving downwards and so the only direction it can move is upwards, around the outside of the form tool. It won't move much but this is a method of forming, quite regularly used for 'one offs'.

Another way of easily making press tools is the use a special casting plaster for making experimental press tools, and mold around the male press tool. I found a company that can supply such plaster, and a wax that can be melted over a roasting dish of water that is just below boiling. The molten wax can then be allowed to cool and harden and becomes a thin sheet which can be formed over the outside of the male press tool, to represent the thickness of the metal being formed. A box is used to hold pour the casting plaster into, and the male press tool, lined with the thin wax coating, is then pushed into the plaster, and then allowed to harden. The wax sheet also acts as a release agent so it can all be separated and you have a perfect shaped female mold. The company says the plaster casting should be good for 10 or even 20 pressings before it starts to degenerate. It is important to have a couple of 1/2" or 12mm silver steel rods to act as guide bars, to suspend in the casting plaster, to ensure they are in perfect alignment. They can be grooved near the bottom to trap them dead vertical, in the hardening plaster.

Bob.

EDIT:   I forgot to say, working out the shape of the internal forming tool is easy. It is the same as the flare on the sides and end of the tender sides. 

That's very ingenious Bob, and worth a detailed explanation. I've never come across that method before, but for irregular shaped parts it sounds perfect. For round parts though, as here, it depends on the availablity of suitable tube, as well as obtaining the plaster and wax, so my personal inclination would be to stick with spinning, but it would be interesting to see some examples of this pressing technique.

Gary

[delaplume]

hello Adam,

quote}------ "Lastly the curly firing iron support, a small bit of taper turning before bending up the support and some careful soldering. I have modelled this up off the drawing I have so I will get one cast as the white bronze we have available is perfect for these sorts of items and I'm sure its something people would love for their tenders".

Yes, absolutely....They are a very iconic part of a GWR tender and easily spotted missing by the "Rivet counters"........ 3 for me please when you are ready...If they can do them in 4mm then we have no excuse...

Alan...

[92220]

Jan 3, 2021 12:40:38 GMT Gary L said:

Jan 3, 2021 10:48:12 GMT 92220 said:

EDIT:   I forgot to say, working out the shape of the internal forming tool is easy. It is the same as the flare on the sides and end of the tender sides. 

That's very ingenious Bob, and worth a detailed explanation. I've never come across that method before, but for irregular shaped parts it sounds perfect. For round parts though, as here, it depends on the availablity of suitable tube, as well as obtaining the plaster and wax, so my personal inclination would be to stick with spinning, but it would be interesting to see some examples of this pressing technique.

Gary

Hi Gary.

I've done a pressing of the clothing under the front of the firebox, where it meets the boiler barrel, but made the press tool out of large lumps of aluminium. It worked well, though I have a lot of scrap due to experimenting. I now have some casting plaster and wax, from the company I mentioned. I am going to experiment with using them to make the female part of a couple of press tools to form the front top, and rear firebox clothing mouldings. I've got photos of the pressing with the aluminium tool. I've just got to download them from the camera and then do a write-up for my thread.

Bob.

[Gary L]

Jan 4, 2021 9:19:39 GMT 92220 said:

Jan 3, 2021 12:40:38 GMT Gary L said:

That's very ingenious Bob, and worth a detailed explanation. I've never come across that method before, but for irregular shaped parts it sounds perfect. For round parts though, as here, it depends on the availablity of suitable tube, as well as obtaining the plaster and wax, so my personal inclination would be to stick with spinning, but it would be interesting to see some examples of this pressing technique.

Gary

Hi Gary.

I've done a pressing of the clothing under the front of the firebox, where it meets the boiler barrel, but made the press tool out of large lumps of aluminium. It worked well, though I have a lot of scrap due to experimenting. I now have some casting plaster and wax, from the company I mentioned. I am going to experiment with using them to make the female part of a couple of press tools to form the front top, and rear firebox clothing mouldings. I've got photos of the pressing with the aluminium tool. I've just got to download them from the camera and then do a write-up for my thread.

Bob.

That would be great Bob. I've learned such a lot from this forum, and illustrating new techniques is all grist to the mill

Gary

[mbrown]

I am also interested to know more about pressing techniques. I found spinning the bell for 99 3462 impossible as I couldn't get purchase to drive the blank against the forces involved. And making it by "raising" with hammers thinned the material very badly. So maybe pressing is the way forward for me too...

Malcolm

[Gary L]

Jan 4, 2021 20:14:11 GMT mbrown said:

I am also interested to know more about pressing techniques. I found spinning the bell for 99 3462 impossible as I couldn't get purchase to drive the blank against the forces involved. And making it by "raising" with hammers thinned the material very badly. So maybe pressing is the way forward for me too...

Malcolm

I don’t want to hog Adam’s thread, but don’t give up on spinning. Watch it being done on YouTube. You do need good leverage. On ‘normal’ spinnings in the real world you can see them putting the yard-long tool under their arm and using full body weight. We are unlikely to need to go that far, but you do need an upstand on your toolpost to act as fulcrum, and my spinning tool is about 18” of BMS about 7/16” dia, and the business end shaped, blended and polished. Lubricate it with soap, apparently.

I’m very much a novice, but it no longer holds any terrors, and I don’t scrap too many blanks.

Gary

[mbrown]

Hi Gary,

It's not leverage of the tool that is the problem, it is driving the workpiece against the drag of the tool.

Some books suggest applying pressure from a pad in the tailstock, but I found the workpiece just slipped. I have spun things successfully when there was the possibility of having substantial driving pegs through the workpiece, but if they were too small they simply tore the metal.

Maybe I was doing something wrong....

Malcolm

[Cro]

Malcolm,

I feel one of Garys well explained posts is in order to help us here! If you still get stuck I can pass on the details of the chap who did my tender Dome.

Adam

[Deleted]

Jan 5, 2021 8:20:33 GMT Cro said:

Malcolm,

I feel one of Garys well explained posts is in order to help us here! If you still get stuck I can pass on the details of the chap who did my tender Dome.

Adam

Hi Adam

Did you by chance use 'Spin360'?

Pete

[92220]

I think one of the problems with spinning is that you need a lathe with a geared drive rather than a belt drive that can slip. Spinning also puts massive loads on the front bearing of the head spindle. I worked for a company that have hundreds of parts spun and I was always having to go over to the company that did the spinning, to sort out queries. Their spinning lathes were all quite old (probably war time age) and had massive front bearings. If spinning a shallow dish shape, the Myford may be OK, but anything that needs spinning into a form that is nearer to a tubular shape, like a GWR dome, is likely to put undue stress on the front spindle bearing. I had some small spinning tools given to me years ago, but I have resisted using them. Interestingly they were not long steel bars. They are 1/2" square shafts, 3" long, with small ball bearings mounted on the end so that it is the circumference of the bearing that comes into contact with the spinning.

Bob.

[Deleted]

Jan 5, 2021 9:50:26 GMT 92220 said:

I think one of the problems with spinning is that you need a lathe with a geared drive rather than a belt drive that can slip. Spinning also puts massive loads on the front bearing of the head spindle. I worked for a company that have hundreds of parts spun and I was always having to go over to the company that did the spinning, to sort out queries. Their spinning lathes were all quite old (probably war time age) and had massive front bearings. If spinning a shallow dish shape, the Myford may be OK, but anything that needs spinning into a form that is nearer to a tubular shape, like a GWR dome, is likely to put undue stress on the front spindle bearing. I had some small spinning tools given to me years ago, but I have resisted using them. Interestingly they were not long steel bars. They are 1/2" square shafts, 3" long, with small ball bearings mounted on the end so that it is the circumference of the bearing that comes into contact with the spinning.

Bob.

I did have a go at spinning my cylinder covers on my Warco, but as you have pointed out Bob, being belt drive it couldn't cope with the torque. I am getting them done outside now.

Regards

Pete