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  • Mechanism Design - An ongoing experiment

    I though i would start a discussion and draw on the experience of the machinists of the group and the tinkerers.

    I have recently been working on my local prototype in Tasmania. Tasmanian railways used 3'6" gauge. There is a small group of modelers who build in Sn3 to get the correct gauge while others build in OO 4mm and HO scale with 16.5mm gauge track.

    A very small few build in what could be called OOn14. Some may have seen the works of Simon Handby in narrow Gauge Down Under.

    Simon recently offered me some a 4 wheel wagon kit to try out that has led to what can only be described as jumping into a rabbit hole of new modelling.

    Now for the focus of the thread. There were only a few Diesel locomotives used in the era I like to model. Mainly the TGR X and Y Class. More info on these can be found here https://www.railtasmania.com/loco/

    Simon has made castings of these and adapted chassis over the years to suit but im now on the task of making my own chassis for these models with 14mm gauge.

    I hope that in the following posts the machinist of the group will be able to jump in and comment on thoughts and musings of possible problems i may encounter.
    Owen Pass Lumber Company

    HO Logging Layout in a Shed.

    https://owenpass.blogspot.com/

  • #2
    With the demise of Hollywood Foundry the availability of quality mechanisms for custom gauges is some what limited.

    I would hope that i am able to produce something that can be adapted to my fleet of up to 10 locos and possibly consider both bobo and coco wheel arrangements.

    My first thought was to start looking at old KTM mechs and there issue. I have an old S1 that i swapped the mech out for an Atlas one.

    From my limited experience these were poor runners due to cracking in the truck frame and poorly cut gears on the gear tower. Anyone care to comment further do jump in?

    I am contemplating a folded etch to mimic the truck frame that commonly cracked and use a worm and wheel gear drive. Sounds simple enough to develop an etch that allows top hat gear bearings on all surfaces ect.

    Now the sticking point is the transfer gearbox up to the motor. Hollywood used a belt drive system of various types. Centre mounted under deck for trolley motors and also truck mounted.

    Im curious on experience of those who have uses the belt drive system vs a gear tower and also thoughts on a centre transfer i guess similar to the old MDC shay vs the more tradition above the chassis board.

    As for some parts, im looking at ultrascle in the UK for worm and gear sets. https://www.ultrascale.uk/eshop/products/CAT015

    PPD in the UK for photo etching - They also offer laser cutting of nickle silver

    I am also considering small batch machine shops in china for the brass pulleys for belt drives or a minilathe for my home shop with the steep learning curve associated.
    Owen Pass Lumber Company

    HO Logging Layout in a Shed.

    https://owenpass.blogspot.com/

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    • #3
      Interesting project.

      Comment


      • #4
        ..........
        New York, Vermont & Northern Rwy. - Route of the Black Diamonds

        Main thread to all that's happening on the NY,V & N Rwy. The New York, Vermont -and- Northern Rwy. - Railroad Line Forums (railroad-line.com)

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        • #5
          I'm not sure if this is useful information but while dabbling in O14 (7mm scale, 14mm gauge), I figured out it's pretty easy to narrow a power truck from the old Bachmann GE 44 ton diesels to 14mm gauge. I don't exactly remember how I did it but do remember it not being terribly difficult.

          I'll see if I can find it and let you know any clues I can discern.

          Good luck with the project, I'll be following along!

          -Cody

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          • #6
            The 1970s Hobbytown drives used quality parts, but the 5-pole open frame motors of the day were prone to 'cogging' as the iron armature rotated slowly. Their nylon universals were durable but were molded with some clearance so had a little slop. This amplified the cogging. It's been on my list for a while to remotor one with a coreless motor to see how it performs. Hobbytown bearings were bronze initially, but later were changed to nylon. Because the parts are all assembled by pressing, they're fairly easy to take apart and reconfigure. One nice feature is the helical gears on the longitudinal shafts in the trucks driving helical gears on the axles: because power can be transferred both ways, they don't buck on grades like a worm can. One tiresome feature is the long universal shaft between the trucks; getting the trucks pointing in different directions could pull one end out of the socket. They could be reinserted without disassembly but it took some fiddling.

            Boston Gear Works was Hobbytown's supplier in the old days. They still offer a broad range of parts, but I didn't find gears quite as small as Hobbytown used the last time I examined their catalog. And being a US company, you might find shipping more of an issue than from China.
            James

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            • #7
              Bernd, I may have intentionally posted here to get a response from you.

              Your comments on the belt drive are valued and will certainly take them on board. I think the lather will be worth it just with a few tools i wish to make. A fellow modeller has made a press to allow wheel sets with 25.7mm axle length to be re gauged to 14mm. That in in itself is worth some money. as well as track laying tools it could produce.

              I have been reading and looking into the cheap mini lathe as an option. I know not the best but from the reports I have read that being realistic in its ability and you get what your after. Certainly more research to be had in this space. Its not a lot more then one of my brass shays or some rolling stock sold off and at 33 yrs old it would be a long term investment for me and lets face it a skill i have always waned to learn.

              The options for used here are limited. Market is pretty small due to the big ditch between us and the mainland. Ones that do come up get snapped up through word of mouth pretty quick.

              Bernd are you cutting your own wheels from brass?

              Back to the mechanism thoughts. I did re gauge 2 GE 70 ton bachman mechs to hon3 years ago with the NWSL wheel conversion. Some of the Alco RS locos have similar wheel dia and spacing as the Tasmanian X and Y. I would need to look at the 1.25mm i need to trim off either side of the frame to get the gauge down to 14mm. Im sure there are other possible candidates.

              As to the hobby town mechs. if everyone sent me all there parts from the junk yard i would be set :-) IN all honesty though the gears from one of them will likely be my starting point for some trials.

              Not a lot of bench time right now as i have a 13wk old and a 2.5 yr old. will be some imagineering going on. More discussion later on when i have a spare minute.

              Owen Pass Lumber Company

              HO Logging Layout in a Shed.

              https://owenpass.blogspot.com/

              Comment


              • #8
                Back from the summer home for the week. Had some time going over some thoughts on the drive for engines. Will post some more thoughts on the subject tomorrow (8-31). Glad you're looking into getting a lathe.

                Bernd
                New York, Vermont & Northern Rwy. - Route of the Black Diamonds

                Main thread to all that's happening on the NY,V & N Rwy. The New York, Vermont -and- Northern Rwy. - Railroad Line Forums (railroad-line.com)

                Comment


                • #9
                  The Hollywood Connection.

                  quote:


                  With the demise of Hollywood Foundry the availability of quality mechanisms for custom gauges is some what limited. Now the sticking point is the transfer gearbox up to the motor. Hollywood used a belt drive system of various types. Centre mounted under deck for trolley motors and also truck mounted


                  It was sad news when he decided to shut down the business. I surfed his site many a times with great interest in the design and building of his drives. One thing I'm always interested in is the sourcing of parts. I don't think he produced many of his own parts. I did like several of his, I'll call them tank drives since that's where the gearing and motor are located, and saved the pictures. I was looking at building something similar but using miniature ball bearing for less friction. Here are two pictures of those drives.

                  Here he uses gearing.



                  This one is belt a belt drive.



                  This last drive is a familiar design. I first saw this sold by Walthers for their Doodlebug kit way back. I have one of those kits. Here are two pics of those drives.





                  This last one is from LaBella Woodworking Company. It's the drive used in their D&RGW Gasoline Rail Motor Car.





                  I collected lots of pictures of different ways to power models because I had a high interest in creating my own for some ideas I've had for critter designs.

                  quote:


                  Bernd are you cutting your own wheels from brass?


                  I'm assuming you mean the pulleys. I haven't tried to do wheels yet. If I did I would be using 303 stainless steel. And "yes" I use brass pretty much for all builds for drives.

                  I've run out of time. I have much more on ideas for drive designs. You have asked some good questions, some of which I still need to answer. I'll do that when I get a bit more time.

                  Bernd
                  New York, Vermont & Northern Rwy. - Route of the Black Diamonds

                  Main thread to all that's happening on the NY,V & N Rwy. The New York, Vermont -and- Northern Rwy. - Railroad Line Forums (railroad-line.com)

                  Comment


                  • #10
                    Not to distract too far from the topic of the thread, but what's the rationale for using a novel gauge? I get that there's a challenge in modelling colonial gauge regardless of the scale, but I would think that from a functional point of view, it seems Sisyphean to pick a gauge for which you have to fabricobble almost everything (track, running gear, drivelines) which are arguably make up the majority of the modeled pieces.

                    Why not save some pain and at least work around readily available track/running gear/mechanisms and use HO (16.5mm) as your gauge? Since you're modelling a very specific and unique prototype, you're going to wind up scratchbuilding almost everything anyway. If I were looking at it strictly from an efficiency point of view, doing that you'd have more time to devote to the other aspects of modelling.

                    On the other hand, I can also appreciate the appeal of doing things "the hard way", just for the challenge.

                    I'm not criticizing, and I think it's a neat project, but I am genuinely curious as to why you'd choose this route to modelling this prototype.

                    Comment


                    • #11
                      Great stuff!

                      If only a short low center gravity unit would be nice for vehicles?

                      Philip
                      Philip

                      Comment


                      • #12
                        quote:


                        Originally posted by MarcusF


                        Not to distract too far from the topic of the thread, but what's the rationale for using a novel gauge? I get that there's a challenge in modelling colonial gauge regardless of the scale, but I would think that from a functional point of view, it seems Sisyphean to pick a gauge for which you have to fabricobble almost everything (track, running gear, drivelines) which are arguably make up the majority of the modeled pieces.

                        Why not save some pain and at least work around readily available track/running gear/mechanisms and use HO (16.5mm) as your gauge? Since you're modelling a very specific and unique prototype, you're going to wind up scratchbuilding almost everything anyway. If I were looking at it strictly from an efficiency point of view, doing that you'd have more time to devote to the other aspects of modelling.

                        On the other hand, I can also appreciate the appeal of doing things "the hard way", just for the challenge.

                        I'm not criticizing, and I think it's a neat project, but I am genuinely curious as to why you'd choose this route to modelling this prototype.


                        Marcus, not to be a naysayer, but take a longer look at some of the threads of builds amongst this forum's folks, that are ready, willing, and very much accepting challenges, even Sisyphean ones.

                        Jim
                        Take the red pill

                        Comment


                        • #13
                          quote:


                          Originally posted by MarcusF


                          Not to distract too far from the topic of the thread, but what's the rationale for using a novel gauge? I get that there's a challenge in modelling colonial gauge regardless of the scale, but I would think that from a functional point of view, it seems Sisyphean to pick a gauge for which you have to fabricobble almost everything (track, running gear, drivelines) which are arguably make up the majority of the modeled pieces.

                          Why not save some pain and at least work around readily available track/running gear/mechanisms and use HO (16.5mm) as your gauge? Since you're modelling a very specific and unique prototype, you're going to wind up scratchbuilding almost everything anyway. If I were looking at it strictly from an efficiency point of view, doing that you'd have more time to devote to the other aspects of modelling.

                          On the other hand, I can also appreciate the appeal of doing things "the hard way", just for the challenge.

                          I'm not criticizing, and I think it's a neat project, but I am genuinely curious as to why you'd choose this route to modelling this prototype.


                          Hi Marcus,

                          I couldn't agree more with your thoughts on hon3.5 or moving to S scale. Fortunately a local modeler has over the years massed masters and castings for most rolling stock in the era i model. This is all in OO scale. there are others modeling in HO and S but majority is scratch built or 3d printed of which im still not all that impressed with.

                          As i hand lay my track already that is not an issue. the kits are available for rolling stock so not an issue to adjust to correct gauge. The mechanisms are the big problem to overcome and with any luck i can come up with something.
                          Owen Pass Lumber Company

                          HO Logging Layout in a Shed.

                          https://owenpass.blogspot.com/

                          Comment


                          • #14
                            Bernd,

                            Thanks for the pics. Offers even more guidance.

                            Some more inspiration for your own projects Bernd,

                            http://www.pojezdypg.cz/ - you can translate to english.

                            https://www.facebook.com/PojezdyPG/

                            Looking through his pictures and blog posts has yielded some inspiring designs to contemplate. Further more are the parts avalible at a reasonable price.

                            http://www.pojezdy.eu/eshop/

                            I did notice a pulley set that is available and might be able to be used in a similar fashion for the old hollywood foundry mechanism. Haven't come across the actual drive belt options though.
                            Owen Pass Lumber Company

                            HO Logging Layout in a Shed.

                            https://owenpass.blogspot.com/

                            Comment


                            • #15
                              ..........
                              New York, Vermont & Northern Rwy. - Route of the Black Diamonds

                              Main thread to all that's happening on the NY,V & N Rwy. The New York, Vermont -and- Northern Rwy. - Railroad Line Forums (railroad-line.com)

                              Comment

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