Building a Hunslet 'Jack' in 7/8ths Scale

[Steve Cook]

Thursday evening saw a piece of steel drilled and shaped to fit the chimney base and cap, I then took it round to my friend to show progress - I think I got top-trumped



As he said though, he has bought all of his stuff in though just to speed things up - it was interesting to see that his smokebox is wider and taller than mine whilst in theory both are built to the same drawings. He's done a nice job on the fake springs with them relieved on the underside to fit the Slomo unit I sold him - I'm putting in the correct 3' wheelbase on my model which means the Slomo won't fit.

I did get presented with my Christmas present though, a 60mm length of 55mm diameter steel for making my smokebox door.



Horrible stuff to machine though with hardened bits appearing at various diameters, it gave the tools a real work out. I struggled to get a good surface finish on it unless I went to a really rounded cutting tip, completely opposite to the steel used for the chimney which almost behaved like brass - I have a lot to learn about materials!

The chunk had both ends faced off, then it was mounted in the chuck and the outside diameters turned down as per the drawings.



What will be the rear of the door was then bored out to size



I had a go at parting it off, but with the tool squealing and chattering what ever I did, I gave in and used a hacksaw instead. About 20 minutes later it was mounted back in the chuck, facing the other way round and marked out for shaping, the centre boss is shown here.



The shape was generated using a rounded tool and winding the handles all at the same time to create a rough profile, this was then smoothed with a file and various grades of sand paper.



This morning saw another go at the sanding to get rid of the tool marks and the clearance hole drilled for the door handles



The excess material on the rear flange was hacksawed off and filed to give a 2mm ledge all the way round to locate inside the smokebox door opening.



The finished component placed on whats left of the steel bar.



The rest of the day has been spent making the parts for the door handles.



A little bit of silver soldering (my first) followed by a fair bit of filing got the door handles finished which meant I could put it all together for the first time



Tomorrows job is to fabricate and hopefully mount all the brass parts to represent the door strapping and hinges.
Steve

 

[JohnFla]

Cracking stuff as always Steve, Your friend is only in front because he only put one line of rivets on his wrapper

 

[Neil]

Though I doubt that I'll ever build something this big or do live steam it's fascinating to watch progress being made. It's also made me realise how much of a slapdash bodger I am/have become. Not sure what I'll do with this insight yet, probably for another thread sometime somewhere. Apologies for the drift Steve, please keep up the good work, I'm hooked on this project.

 

[ceejaydee]

Lovely craftsmanship Steve - thanks for sharing

 

[Dikitriki]

Cracking stuff as always Steve, Your friend is only in front because he only put one line of rivets on his wrapper

Actually, I think Steve's smokebox has a finesse that his friend's lacks - the rivets are better defined, the filing is is just a bit squarer, and the chimney cap and flare are finer.

I too am enjoying the (to me) heavy engineering aspect of the construction, and the explanations.

Richard

 

[Steve Cook]

Thanks for the comments and the likes chaps
I ought to say that the brass smokebox my friend has is actually a one piece casting he bought from Australia, I think it is the casting process which explains the lack of sharpness in some of the detail.

Today started out OK with the production of all the brass bits to make up the door hinges.



Alas, it all went downhill from there on in! The suggested way forward is to put all the components in place on a firebrick and silver solder together. The notes say that all the parts must be placed securely in position so there is no chance of movement, but there are no hints or tips given on how to achieve this. Despite weighting parts down with various chunks of metal, I have not yet come up with a way that works. Most bits have been remade twice now - there is only so much clean up you can do before it becomes quicker to make a new part.
I think its time to pause for a thought and try and come up with a better way of doing things. The first task is to reduce the number the components as that makes holding significantly easier. Some way of fixing the unit down would also be very helpful. I'll let you know what I come up with
Steve

 

[mickoo]

Not sure which bits need holding where, but try something like fire brick cement or some sort of fire proof putty, you might find something like tiling grout or putty might hold it long enough to solder and cool.

 

[unklian]

You are doing grand Steve. I would say that soldering all those loose bits is a tad optimistic any way. If I might make a couple of suggestions, I would make the strap hinges in one piece. with the eyes rolled around a spare bit of hinge pin. I think that is how the real thing would have been done anyway. I would locate them on the door by drilling and pinning them in place with a couple of your little brass rivets. If you don't want the heads showing file them off after soldering. The hinge posts that attach to the smokebox likewise need a pin or even a small bolt from inside to hold them in place, the solder then becomes the 'glue' that holds it all together properly. Time for a brew and a bit of a think

 

[JimG]

Steve,

I haven't done silver soldering for a few years, but I do remember using soft iron wire to hold things in place. The wire bends and stays bent with little or no spring back. You can weight one end of a wire down off the piece and bend/twist the other end to bear down on whatever part you want. I used to get the wire from florists - flower arrangers use it. I've just done a search and I'm not definitely sure if I've found any. I used to get it in small bundles of straight wire about 12" long and about 1mm thick with no covering. I'll keep looking and see if I can locate anything on the Internet.

Jim.

 

[ceejaydee]

I've used soft iron wire to hold parts together whilst hard soldering in the past but usually that has been fairly simple shapes; your assembly is far more complex maybe for this simple approach.

I say the past and sometimes it does feel like a lifetime ago.

Edit - Jim G has posted whilst I was typing so I wasn't imagining it despite a frantic look through various LBSC, Evans, Jones, Cooke et al writings for evidence

Further Edit - I used to get the wire from work as the packing dept used it to tie the synthetic 'hessian' sacks some of the product was sent out in... blimey I left there 20 years ago this year!

 

[adrian]

Not to sure what bits need to be held together but a couple of suggestions for alternative methods.

First suggestion - use different grades of silver solder, they all have different melting points. Do the first joint with a hard solder, next joint with a medium solder and the hard soldered joint should be ok. Then you have easy and extra easy to go at as well.

Other option - solder up the joints before cutting and final finish of the component. For example the straps across the door and the brass hinge tube, obviously we want them all aligned so the straps are parallel. So cut out the strap the correct width but just over twice the height required, solder on the single piece of brass tube. So only one soldered joint, then cut it in half to get the two straps, alignment guaranteed.

Best of luck.

 

[jamiepage]

Steve,
Another idea for what it's worth would be to mill two slots in the door blank, cut and drill two over- deep door straps, slot together and solder, after which the straps can be dressed back to better follow the door dishing.
Photos show the straps over deep so not yet dressed to shape.

 

[jamiepage]

 

[jamiepage]

 

[JohnFla]

Steve, I've used Blue tac with some success but only in 4 and 7mm.

 

[Steve Cook]

Another week, another smokebox door

Thank you for all of the comments and suggestions above concerning the hinges. I took onboard your views and came up with what I think was a workable solution. Unfortunately my equipment isn't rigid enough to try the approach Jamie demonstrated above, however its very impressive and not one I would have thought off!

My proposed solution was to roll the eyes of the straps as per Ians suggestion, but leave them over length so the 'door' ends could be tied together by soldering on an extra strip of brass. With the hinge pin in place, that would give me a rigid / square unit which I could hold against the smokebox door and drill through for the rivet fixing holes. I could then cut the straps down to size and profile, riveting then soldering in place. Small pins in the base of the hinge posts would locate in an aluminium jig, holding them firm and at the correct spacing.

With all that sorted, I spent some time trying and failing to get the straps rolled around a dummy hinge pin, I can anneal the brass OK but getting a neat roll round currently escapes me - more practise required I think. Of course, having spent more time looking at the hinges on photographs, I became dissatisfied with my smokebox door. I suppose the problem comes from the fact I followed the drawings and didn't look at any photos to check whether the drawing replicated what I see. The door proportions were all flawed so I made another one (new one on the right).



The new door is both thinner and flatter, the flange is much better proportioned and the centre boss is both prouder of the front face and smaller in diameter. Comparing it against a photo shows its a lot closer in my opinion.



It looks good when located in position, so its time to get going again on the hinges



Steve

 

[unklian]

Smokebox door MkII is a definite improvement, a bit more finesse for sure. On the hinges did you notice that they are not spaced equally from the centre of the door ? The front of that loco is very interesting it's all over the place , and I guess that is its charm .

 

[Steve Cook]

Cheers Ian. The hinges are in a position where people are going to ask if my modelling is bad aren't they
I thinks its a great loco, I'm having naughty thoughts about doing a bigger one!
Steve

 

[JimG]

On the hinges did you notice that they are not spaced equally from the centre of the door ?

They don't look too square either. That'll give Steve a bit of leaway.

Jim.

 

[Hobbyhorse]

Very impressive workmanship.
Garden rail is my distraction from the modelling business, and I'm currently designing the garden to fit a line into it.
Most of my stock is 16mm but I would like to including some mixed gauge track work for 7/8th's in 45mm, as I would like to build one of the small Barclay gas works loco in 7/8th's.

Simon