It must be point­ed out that although the focus of this arti­cle is about Dinky Toy devel­op­ment, the order of the steps out­lined below would be applied to all in house man­u­fac­tured prod­ucts, though not all steps would be rel­e­vant (e.g. new parts for Mec­ca­no out­fits). The use of the word “pro­to­type” denotes the actu­al real life vehi­cle, not the mod­el. The accom­pa­ny­ing illus­tra­tions fol­low the devel­op­ment of DT 199, the Austin Sev­en Coun­try­man intro­duced in May 1961.

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A well proven route

Prod­uct devel­op­ment fol­lowed a well proven route:

1) The New Prod­uct Com­mit­tee would iden­ti­fy a pro­posed mod­el to man­u­fac­ture.

2) The committee’s choice would be passed to the New Prod­uct Devel­op­ment Man­ag­er who would liaise with the man­u­fac­tur­er (e.g. Ford Motor UK) and obtain pho­tographs and draw­ings. In the absence of good pho­tographs of all sides of the pro­to­type, a trip would be tak­en to pho­to­graph the pro­to­type fur­ther using a wood­en mea­sur­ing bar grad­u­at­ed in inch­es and placed against the pro­to­type as required. By sign­ing con­fi­den­tial­i­ty agree­ments with man­u­fac­tur­ers, details could be obtained of vehi­cles that were yet to reach the pub­lic domain. This way a Dinky would be released to coin­cide with the mak­er’s launch.

3) Using the above data, a draughts­man assigned to the New Prod­ucts Man­ag­er would pre­pare an assem­bly draw­ing of the Dinky show­ing the pro­posed num­ber of parts, mate­ri­als and col­or scheme. The scale of the assem­bly draw­ing would be 1:1 so as to give the cor­rect impres­sion of size.

4) Next to the Draw­ing Office, a small Mod­el Shop would man­u­fac­ture a work­ing mod­el at the pro­posed scale, espe­cial­ly if a mech­a­nism need­ed to be proven. Not all pro­posed prod­ucts would need a mod­el if they were part of an estab­lished and proven Dinky group (e.g. saloon cars). Mod­els would be made from a vari­ety of mate­ri­als such as wood, brass, plas­tic, sheet steel, or a com­bi­na­tion as required.

5) Using the assem­bly draw­ing and his­tor­i­cal data from pre­vi­ous sim­i­lar prod­ucts, the Cost­ing Depart­ment would pre­pare a rough esti­mate of man­u­fac­tur­ing and pack­ag­ing costs. With this infor­ma­tion and the mod­el shop mock-up, the New Prod­ucts Com­mit­tee would make a final deci­sion on whether or not to pro­ceed with devel­op­ment.

6) The Draw­ing Office would now pro­ceed with a detail design of all the new parts required.

7) As soon as detailed parts became avail­able for check­ing, a Tool Design­er would study each part and deter­mine where the tool­ing split lines (part­ing lines) would be. This was a skilled job with the aim to make the split lines as unob­tru­sive as pos­si­ble con­sis­tent with ease of man­u­fac­ture. Tool design and pat­tern man­u­fac­ture could now com­mence.

Pat­terns would be carved in wood at 3 or 4 times the intend­ed size of the fin­ished mod­el. The pat­tern is “male”. “Female” casts are now tak­en from the pat­tern in wear resis­tant resin whose bound­aries fol­low the split lines already deter­mined. These casts are used by the tool­mak­er on die sink­ing machines (pan­to­graph copiers) to cre­ate the mov­ing parts of the tool in steel.

Some fur­ther com­ments about pat­terns:

Mec­ca­no did have an in house pat­tern shop, but capac­i­ty prob­lems lead to the use of exter­nal pat­tern mak­ers in late 1960’s. The qual­i­ty and accu­ra­cy of these pat­tern mak­ers pro­vid­ed an oppor­tu­ni­ty to reduce the num­ber of dimen­sions on detail draw­ings. Pro­vid­ed the draw­ing was drawn accu­rate­ly at 3 or 4 times fin­ished scale, the pat­tern mak­er would take their mea­sure­ments direct­ly from the draw­ing and with the aid of a good set of pho­tographs cre­ate the pat­tern. Obvi­ous­ly, areas of designs that relat­ed to cor­rect fit and func­tion of work­ing parts (e.g. doors, etc.) would still be dimen­sioned, but not the 3D shape and pro­files of the exter­nal body­work.

Not all parts required a 3D wood­en pat­tern. In the case of parts with an irreg­u­lar pro­file but a fixed depth, one or more steel tem­plates would be used on the pan­to­graph (die sink­ing machine).

It’s now nec­es­sary to describe the man­u­fac­ture of the clear poly­styrene win­dows fit­ted to many mod­els which fit inside body cast­ings with a min­i­mum gap. To achieve this, a dupli­cate steel core is made, iden­ti­cal to the one in the diecast tool for the body. After hard­en­ing, this core is sent to a spe­cial man­u­fac­tur­er and used as a “hobb”. The hobb is forced under extreme pres­sure into a bil­let of spe­cial steel, thus cre­at­ing the cav­i­ty of the win­dow. Sev­er­al machin­ing oper­a­tions fol­low on the bil­let to make it suit­able for fit­ting into the win­dow injec­tion mold.

The hobb would be used repeat­ed­ly depend­ing upon the num­ber of cav­i­ties (impres­sions) in the win­dow mold. The spe­cial steel is capa­ble of receiv­ing the very high (mir­ror) pol­ish nec­es­sary to mold the win­dows crys­tal clear.

8) When extra tool mak­ing capac­i­ty was required, sub­con­tract­ed tool mak­ers were used. In this case only the com­po­nent designs and draw­ings show­ing the loca­tion of the split lines would be issued. The sub­con­trac­tor is now respon­si­ble for tool design and pat­tern mak­ing. How­ev­er, such tool designs and pat­terns had to be sub­mit­ted back to Mec­ca­no Ltd for approval pri­or to man­u­fac­ture. Mec­ca­no had a strict tool­ing stan­dard for sub­con­trac­tors to adhere to.

9) Fin­ished new tools would be tried and sam­ple parts assem­bled. Any mod­i­fi­ca­tions nec­es­sary to improve fit or func­tion would be car­ried out and the tool tried again.

Diecast parts would be placed in a vibra­to­ry machine with grad­ed hard stone media to remove flash and then “bon­derised”, a liq­uid wash process that cleaned the cast­ings and etched the sur­face so paint would adhere well to the Mazak.

Paint­ing would be car­ried out in auto­mat­ic spray booths that trans­port­ed the cast­ings and spun them under strate­gi­cal­ly placed spray guns to apply an even coat on all sur­faces. The parts would then be trans­port­ed through an oven to hard­en the paint.

If sec­ondary detail was required after hard­en­ing, the cast­ings would be hand sprayed in indi­vid­ual booths. In the booth the part would be placed behind a mask to shield every­thing except the detail to be sprayed. Sev­er­al col­or schemes may be tried to help the New Prod­ucts Com­mit­tee and sales staff arrive at a final deci­sion.

10) With all tools and parts approved, a 500 sam­ple man­u­fac­tur­ing run would be processed from start to fin­ished boxed prod­uct. After fix­ing any remain­ing issues, full pro­duc­tion would com­mence.

Dur­ing steps 5 to 9 oth­er areas would be get­ting their house in order, such as mate­r­i­al pur­chas­ing, detail cost­ing, pack­ag­ing design, sales and mar­ket­ing, paint shop masks, assem­bly jigs and pre­ferred sequence of assem­bly. By the late 1960’s, over­all time to mar­ket from idea to pro­duc­tion was reduced to 12 months by using con­cur­rent engi­neer­ing meth­ods. This enabled the release of two new Dinkys per month.

The tra­di­tion­al method of assem­bly was down a con­vey­or, with female oper­a­tives on each side doing a sin­gle oper­a­tion from the parts pro­vid­ed to their work point. At the end of the con­vey­or, the com­plet­ed mod­el would be inspect­ed and boxed.

Out­put was fast, but the work was very repet­i­tive and bor­ing for the ladies so dur­ing the 1970’s a dif­fer­ent approach was adopt­ed in which a sin­gle lady had her own work­sta­tion sup­plied with all parts where she could build a com­plete prod­uct. For some prod­ucts the con­vey­or sys­tem would still have to be used.

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Modernizing the machinery

An impor­tant fact relates to the qual­i­ty of diecast and plas­tic tool­ing. With the excep­tion of press tool­ing (Dinky tin bases, Mec­ca­no etc.) pri­or to late 1962 all diecast and plas­tic tools weren’t hard­ened (heat treat­ed) and qual­i­ty “Hot Work” steels weren’t used.

Not using “Hot Work” steels reduced die life and in the extreme case where alu­minum (which has near­ly twice the melt tem­per­a­ture than Mazak) was used on the Vul­can Bomber, the die cat­a­stroph­i­cal­ly failed after about 500 shots. So spe­cial new steels were used and tools hard­ened. This gave a tool life of poten­tial­ly 250,000 shots using Mazak, depend­ing on die com­plex­i­ty.

From 1961 and up to 1965, new high pres­sure ful­ly auto­mat­ic diecast­ing machines were grad­u­al­ly intro­duced with many ready for when the Speke cast­ing facil­i­ty was closed and brought into Binns Road. Because the orig­i­nal man­u­al­ly oper­at­ed “Kipp” cast­ers were no longer required they were phased out. This effec­tive­ly grad­u­al­ly killed off dozens of Dinkys because the Kipp tool­ing was­n’t com­pat­i­ble with the new machines.

The new machines offered faster pro­duc­tion and much denser qual­i­ty cast­ings with big sav­ings on Mazak, because the path from injec­tion point to cav­i­ty was much short­er and small­er. The machines were designed by a very clever gen­tle­man Desmond Youde who was Senior Plant Engi­neer for Mec­ca­no, and were con­struct­ed at Binns Road.

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The impact of metrication

Dur­ing the 1970’s sev­er­al changes took place, notably met­ri­ca­tion (which Mec­ca­no took very seri­ous­ly) which revised the gen­er­al wall thick­ness for cast­ings and mold­ings from 0.040″ to 1 mm. In the late 1970’s, wall thick­ness for cast­ings was fur­ther reduced to 0.8 mm to save mate­r­i­al and cost with­out any notice­able reduc­tion in strength. Because the most used mate­ri­als were Mazak and High Impact Poly­styrene (HIP), the use of shrink­age allowance in tool­ing was aban­doned as both these mate­ri­als shrank at iden­ti­cal rates (0.6%).

With the aver­age Dinky saloon being about 105 mm long, this intro­duced an over­all scale length error of about 0.6 mm which wasn’t worth wor­ry­ing about com­pared to the advan­tages of elim­i­nat­ing down­stream errors when apply­ing shrink­age. A fur­ther move was to draw designs on plas­tic film rather than tra­di­tion­al trac­ing paper. This elim­i­nat­ed the need to trace designs onto linen for dura­bil­i­ty as plas­tic film is vir­tu­al­ly inde­struc­tible.

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How it’s done today

Today of course, design and tool­ing are done very dif­fer­ent­ly. Pro­to­types can be 3D laser scanned and the data loaded into a 3D CAD sys­tem for detailed design of the prod­uct. This 3D data can be used in stere­olith­o­g­ra­phy (desk top print­ing) to pro­duce resin mod­els for assess­ment, down­loaded into CNC machines to direct­ly machine detail into hard­ened steel, or to man­u­fac­ture elec­trodes used in EDM (spark ero­sion) machines.

• CAD — Com­put­er aid­ed design
• CNC — Com­put­er numer­i­cal machin­ing
• EDM — Elec­tric dis­charge machin­ing

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About the author

Vic Mum­by joined Mec­ca­no Ltd. in 1961 as an appren­tice tool­mak­er and trans­ferred to the draw­ing office in 1965. After spend­ing sev­er­al years in prod­uct design, he trans­ferred to tool design and final­ly became Chief Draughts­man from 1975 until the clo­sure of the com­pa­ny in 1979.

Vic is active in the Horn­by Rail­way Col­lec­tors Asso­ci­a­tion (HRCA) and Dinky Toy Col­lec­tors Asso­ci­a­tion (DTCA) and was inter­viewed by Jon Angel. You can read the inter­view here:

• An Inter­view With Vic Mum­by by Jon Angel