Brass castings for brake lever guard of JLTRT TTA - now available

Discussion in 'Workbenches, including workshop techniques.' started by Dog Star, 21 January 2019.

  1. Dog Star

    Dog Star Western Thunderer

    I have written elsewhere ( see here) about our difficulties in keeping the brake lever guards of our TTA 7mm models in an intact condition - made of whitemetal the guards are broken easily, the first three kits that I have assembled have required roughly four castings per model. To me the part ought to have been a brass casting or a nickel silver etching... faced with another few kits to make I decided to do something about the status quo and engaged Chris Brown (@ChrisBr) to help. This topic is about what was done to produce brass castings and to show the result.

    I provided Chris with a whitemetal casting from an unstarted kit and Chris produced a 3D drawing of the part as was supplied in the kit. My experience with the initial builds was that the "foot" of the casting did not have a secure attachment to the axleguard being just a butt joint. Chris added a "stay" to the lever guard which was a closer approximation to what we could see in photographs - thanks to Brian Daniels (@Brian Daniels) for pointing us towards his on-line gallery of TTA photos where there is a suitable image of a prototype wagon. As well as increasing the contact area of the stay to axleguard Chris included a spigot on the rear face and thereby provided a positive location for the bottom end of the lever guard. A first trial 3D print showed that the drawing was a good representation of the original casting... except that we found that the JLTRT casting was too long and placed further left than on the prototype (see here for details).

    Chris changed the drawing to reflect our better understanding of the prototype and another trial 3D print was obtained... and fitted to the wagon as seen here. Now that we had a 3D drawing which could produce a print to fit the model I asked David White (Slater's Plastikard) for help in converting the drawing to brass castings. I sent the 3D drawing to David as a .STL file from which David obtained a wax master. The wax master was used to produce a brass master... the brass master was used to produce lost-wax brass castings and those items were posted to me.

    Here is a TTA underframe using the JLTRT casting:-
    TTA2.jpg

    Here is tha underframe after removal of the JLTRT casting - the large, lower, hole is where I had put an epoxy resin plug to secure the foot of the JLTRT casting... the upper, small, hole is for the spigot of our brass casting:- TTA3.jpg

    This is a cast brass brake lever guard from Chris's 3D drawimg, I have cleaned and polished the "as-received" casting:- TTA4.jpg

    A finer appearance than previously, compare with the prototype photo in my original post, here.

    This is a sample of the castings from Slaters, two brake lever guards so one sprue per wagon:-
    TTA sprue.jpg

    Other WTers got to hear of what we were doing with the result that more sprues are required than were provided by the first batch from Slaters. I shall be ordering some more castings in February so please let me know if you want some - price is £3.50 per sprue plus postage.

    regards, Graham
     
    Dan Randall, Overseer, simond and 4 others like this.
  2. Pencarrow

    Pencarrow Western Thunderer

    No use to a Southern modeller like me but an excellent demonstration of folk working together and using the available technology to produce items that were not commercially available or to the right standard. Great stuff - particularly making it available to others. :thumbs:
     
    Dan Randall, markjj and simond like this.
  3. AJC

    AJC Western Thunderer

    I'm not sure why they'd be of no use? Lever guides are - relatively - generic (though just how generic would be clearer with some dimensions; is that possible please @Dog Star?) and these could be adaptable for other uses with a new stay bracket for example. At that price even this 4mm modeller might have a use for a couple of pairs for some incomplete 7mm vehicles I have lurking in a drawer, if the size is right...

    Adam
     
    Lyndhurstman likes this.
  4. Pencarrow

    Pencarrow Western Thunderer

    I assumed they would be specific to the wagon and stand ready to be corrected - would be useful if they are relatively generic though.
     
    AJC likes this.