Tender (June 2020 - Current)
The tender is the last 'major' element of the Allchin Build and when fitted will give scale and proportion to the model, however in all fairness this element is a complete project in its own right! It contains a water tank, coal bunker, draw bar, steam powered water lifter, injector, attaches the braking system, the majority of the plumbing and foot steps and footplate for the driver and engineer to stand! There are a various ways of tackling this project, I chose to start with the strengthening plates that sit over the brass tender and connect the tender to the hornplates. I made this decision as I didn't make the hornplates I have no idea how accurate the hole spacing or alignment is so the strengthening plates can act as a drilling guide and reference plain upon which the rest of the tender can be built.
Strengthening Plates
The plates were initially cut to size and clamped to the hornplates to position and mark for the bearing blocks and fixing holes. I ground up two short transfer punches to transfer the location of the various fixing holes to the plate, then once content the plates were removed, cut, filed and drilled. I modified the design slightly here to allow for a extra 2mm in length as if made 'correctly' the fixing holes at the bottom of the bearing block would be impractically close to the edge of the material (just another problem with original the design!)
The tender is the last 'major' element of the Allchin Build and when fitted will give scale and proportion to the model, however in all fairness this element is a complete project in its own right! It contains a water tank, coal bunker, draw bar, steam powered water lifter, injector, attaches the braking system, the majority of the plumbing and foot steps and footplate for the driver and engineer to stand! There are a various ways of tackling this project, I chose to start with the strengthening plates that sit over the brass tender and connect the tender to the hornplates. I made this decision as I didn't make the hornplates I have no idea how accurate the hole spacing or alignment is so the strengthening plates can act as a drilling guide and reference plain upon which the rest of the tender can be built.
Strengthening Plates
The plates were initially cut to size and clamped to the hornplates to position and mark for the bearing blocks and fixing holes. I ground up two short transfer punches to transfer the location of the various fixing holes to the plate, then once content the plates were removed, cut, filed and drilled. I modified the design slightly here to allow for a extra 2mm in length as if made 'correctly' the fixing holes at the bottom of the bearing block would be impractically close to the edge of the material (just another problem with original the design!)
Draw Bar
The draw bar was a casting originally purchased by my Grandad before I was born, so great care was required not to bozo [get the job wrong!] up the job! The casting needed to be machined all round including an internal 'draft angle' to match the original prototype that required a fairly complex milling set up. Again, I found that the casting was only just large enough to machine to dimension and internally was marginally under size, however the defect could be lived with as when fitted would not be obvious. [Instgram Vid]
The draw bar was a casting originally purchased by my Grandad before I was born, so great care was required not to bozo [get the job wrong!] up the job! The casting needed to be machined all round including an internal 'draft angle' to match the original prototype that required a fairly complex milling set up. Again, I found that the casting was only just large enough to machine to dimension and internally was marginally under size, however the defect could be lived with as when fitted would not be obvious. [Instgram Vid]
Fair Lead and Angle Irons
The fair lead rollers guide the winch cable past the tender and are suspended off the back of the tender upon two angle irons. The rollers were a simple turning job and were made from stainless steel as they will not be painted. The angles are milled from a small piece of commercially available mild steel angle. The bolts securing the rollers were formed from a mild steel rod and a square head section soldered on the top.
The fair lead rollers guide the winch cable past the tender and are suspended off the back of the tender upon two angle irons. The rollers were a simple turning job and were made from stainless steel as they will not be painted. The angles are milled from a small piece of commercially available mild steel angle. The bolts securing the rollers were formed from a mild steel rod and a square head section soldered on the top.
Tender Sides
Material: The sides of the tender are to be made from 16G brass sheet, which during the COVID19 lockdown posed quite hard to obtain. Luckily my dad stepped in having raided his stock pile and let me have two solid brass kick boards originally fitted to the bottom of office doors in a factory (many years ago!) Amazingly they were in good enough condition and the correct gauge! So they were recused from being scrap to being immortalised as the rear end of this Allchin!
Formers: My Grandad had originally purchased a cast iron former from Reeves which could be used to hammer the brass round. However, on closer inspection it was pitted, and would have taken quite some time to bring it to a condition suitable that accurate side plates could be made from it. Then as luck would have it the phone rang!...
I'm a member of the Bristol Society of Model and Experimental Engineers and had recently given a technical presentation on the construction of the Allchin Hind Wheels. As luck would have it the slides were passed onto one of the members friends who was in the final stages of his Allchin Build - Roger James. I was provided the contact details for Rog with the message that he might be able to help with my build. So, I got in contact with him and after a great conversation around the various build elements of the Allchin, Rog offered me the use of his tender formers and to my delight volunteered to post them to me.
Rog had commissioned the CNC cutting of the formers from a tough engineering plastic and the set included the inner and outer formers for both sides of the tender. The formers were complete with drillings required to position the key features and were accurate with respect to the drawings. This was a huge help and something I'm very grateful for, I can't thank Rog enough and should I get the chase to meet him in person Beer will be provided!
Material: The sides of the tender are to be made from 16G brass sheet, which during the COVID19 lockdown posed quite hard to obtain. Luckily my dad stepped in having raided his stock pile and let me have two solid brass kick boards originally fitted to the bottom of office doors in a factory (many years ago!) Amazingly they were in good enough condition and the correct gauge! So they were recused from being scrap to being immortalised as the rear end of this Allchin!
Formers: My Grandad had originally purchased a cast iron former from Reeves which could be used to hammer the brass round. However, on closer inspection it was pitted, and would have taken quite some time to bring it to a condition suitable that accurate side plates could be made from it. Then as luck would have it the phone rang!...
I'm a member of the Bristol Society of Model and Experimental Engineers and had recently given a technical presentation on the construction of the Allchin Hind Wheels. As luck would have it the slides were passed onto one of the members friends who was in the final stages of his Allchin Build - Roger James. I was provided the contact details for Rog with the message that he might be able to help with my build. So, I got in contact with him and after a great conversation around the various build elements of the Allchin, Rog offered me the use of his tender formers and to my delight volunteered to post them to me.
Rog had commissioned the CNC cutting of the formers from a tough engineering plastic and the set included the inner and outer formers for both sides of the tender. The formers were complete with drillings required to position the key features and were accurate with respect to the drawings. This was a huge help and something I'm very grateful for, I can't thank Rog enough and should I get the chase to meet him in person Beer will be provided!
Flanging: The initial stage of production was to rough out the materials. The Brass plate was mapped out to avoid any damage or deep scratches and the blanks cut out on the bandsaw. The position of the former was finalised and marked on the brass sheet. It was crucial to keep the formers in the same location during the flanging to prevent missing the dimensions! The brass sheet was then clamped between in the inner and outer formers in the vice and supported with an array of G cramps around the perimeter and positioned relative to the hammering taking place.
The flanging itself was a stepped process where wooden and plastic mallets were used to draw the brass round the formers until such point as the work hardening resulted in the material being too tough to bend further. At which point, the brass was removed and placed in the hearth for annealing.
I found that the brass sheet required three rounds of bending/annealing in order to reach final dimension. Rightly or wrongly [answers in a comment please!], once the final form was reached, I didn't anneal the sheet further which has essentially locking in the work hardening stress. My thought was that it will make the overall assembly tougher, although in hindsight, it could lead to stress cracking over time? If anyone has any better judgement on this please let me know!
The flanging itself was a stepped process where wooden and plastic mallets were used to draw the brass round the formers until such point as the work hardening resulted in the material being too tough to bend further. At which point, the brass was removed and placed in the hearth for annealing.
I found that the brass sheet required three rounds of bending/annealing in order to reach final dimension. Rightly or wrongly [answers in a comment please!], once the final form was reached, I didn't anneal the sheet further which has essentially locking in the work hardening stress. My thought was that it will make the overall assembly tougher, although in hindsight, it could lead to stress cracking over time? If anyone has any better judgement on this please let me know!
To annealing the brass I brought the sheet to a cherry red held it there for 10-15 seconds then allowed it to cool naturally to black. This lead to fire scale and carbon deposits on the surface, I initially removed the worst of it with a scrubbing brush and water and then pickled it for 4-5mins in a 10% by volume Sulphuric Acid solution.
Foot Plate Lower and Upper
The tender requires two foot plates to be made which are located on the left hand side of the engine (just below the gap where the driver can climb up into the driving position). Both of the foot plates are brass assemblies which were constructed from essentially scrap brass I had in the workshop!
The initial stage of product was again creating a set of drawings as the original drawings were at best a rough dimensionless general assembly! This lead to scaling from the hand draw drawings (which is never ideal) and some creative licence on what looked best and true to the original prototype.
Manufacture started with milling a brass 'L' angle bar to thickness that would form the top and back side of both steps. This was then cut into two lengths, one for each step. The sides of steps have flanges, which I guessed were originally part of the same casting, however on this model I made the flanges from the same 16G brass as the rest of the tender. Small triangles were cut out and silver soldered to the L brackets and then pickled and brought to size.
The tender requires two foot plates to be made which are located on the left hand side of the engine (just below the gap where the driver can climb up into the driving position). Both of the foot plates are brass assemblies which were constructed from essentially scrap brass I had in the workshop!
The initial stage of product was again creating a set of drawings as the original drawings were at best a rough dimensionless general assembly! This lead to scaling from the hand draw drawings (which is never ideal) and some creative licence on what looked best and true to the original prototype.
Manufacture started with milling a brass 'L' angle bar to thickness that would form the top and back side of both steps. This was then cut into two lengths, one for each step. The sides of steps have flanges, which I guessed were originally part of the same casting, however on this model I made the flanges from the same 16G brass as the rest of the tender. Small triangles were cut out and silver soldered to the L brackets and then pickled and brought to size.
To Date......