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Project - 7.5 Gage Ride-on Train

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  • Project - 7.5 Gage Ride-on Train

    As I've been accepted in the Vancouver Island Model Engineers society, I've the intention of making my own train. Nothing fancy, just electric, simple as I can get it. The end goal of this is to get my now 6yr old kid to say "Daddy, let's go to the shop to work on the train." I figure, if I get there before he's 12, I'm doing good.

    I've got all the guts from an electric wheelchair and a stack of batteries from a UPS, so I'm most of the way there. I just need to replace the wheel that are attached to the geartrain at the end of the motors to the wheels that hit the track. I figure I'll use both motors, one for each truck, and then add a bit of mechanical linkage to the joystick control so it can only go forward and backwards. The frame is no big deal... just welding up angle iron, done that lots. It will only be the loco and one car, probably batteries in both. Both will be small, just enough to hold an adult and a kid. It's roughly laid out in my head with only a few details to work out before I start.

    Anyway, problem number one is the drivetrain. The received wisdom from the club is to use chain drive, not belts. Now, I don't get this considering we're talking about little steel wheels running on steel track, and the drive will only be a little bit smaller than the wheel. How could a rubber belt on an aluminium pulley slip before a steel wheel running on steel rail, even if you consider it will be 2 wheels per pully?

    Me... I'm leaning towards using a ribbed alternator belt... about the right size, cheap to buy, and making pulleys for it would be the easiest. What say you?

    Yeah, yeah, I know... take the advice of a bunch of guys that have already built trains over asking all the crazy people on this board... but I guess I'm one of the crazy ones now. Why chain over belt?

    David...
    http://fixerdave.blogspot.com/

  • #2
    Just remember......

    A chain you use a chain breaker with, and can put on the sprockets anywhere.

    A belt (unless you use a link type) needs access over the shaft, and so would be hard to put on the wheel set without dropping an axle to get it over.
    CNC machines only go through the motions

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    • #3
      Are these the size your thinking about .. ? Here
      John Titor, when are you.

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      • #4
        Originally posted by Mike Amick View Post
        Are these the size your thinking about .. ? Here
        Yup, that gage, those tracks, that engineering society, and some of those guys... but a smaller engine. Those are the bigger ones that come out for the public run day. I won't be pulling the carnival cars, max 2 adults and 2 kids. Also, I'm a long way from running a steam engine.

        It won't be the smallest train on those tracks, my kid absolutely loves a 2-car (and only 2 small person) skytrain a guy made, but there are some pretty big beasts too. My kid and I did a loop on the club "Loco 6000" today, in the pouring rain. That thing litterally weighs a ton. He loved it.

        My wheels will be 3" diameter... small even by club standards, so the pulley/sprocket will need to be smaller than that. But, an altenator pulley is pretty small too.

        David...
        Last edited by fixerdave; 11-14-2016, 03:22 AM.
        http://fixerdave.blogspot.com/

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        • #5
          If you're making the engine look like a more or less modern diesel/electric perhaps leave room for a possible engine that runs an automotive alternator that then charges a smaller size battery bank to run the motors. Maybe stick with all battery power for now but with the room needed to adapt it later on?

          I recall a plantation tour I had in Hawaii a few years ago where they used a small electric engine to pull the produce around to the processing plant. Out of interest I googled for "electric shunting train" and in the "images" option got quite a few interesting looking smaller engines that might tickle your fancy. If you're going to make a smaller engine this might be a way to let you do so while still making something that is able to be closer to the same scale as the other engines. And shunting engines didn't normally move a lot of cars so that fits in too. A few of them are even made with wooden upper structures.

          The descriptions on a few pictures also led me to do an image search on "battery locomotive". That turned up another bunch of interesting smaller designs that might let you build "big" without actually being big.

          I'm guessing that the others just found that with belts that they ran into too many slipping issues. With a proper design it could likely be made to work. But perhaps there's some issue with slipping unless extra belt tension is used and then there's too much friction or something. Or perhaps it's as simple as chains can use a master link so they are simply far easier to work with.
          Chilliwack BC, Canada

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          • #6
            Friend of mine did this: http://sparetimelabs.com/animato/ani...03/3003bg.html

            I'm in the process of doing a model of the first Galloping Goose, but I keep re-engineering stuff. Just need to nail it down so I have a switcher for the track I'm planning on building.

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            • #7
              Originally posted by BCRider View Post
              If you're making the engine look like a more or less modern diesel/electric...

              I'm guessing that the others just found that with belts that they ran into too many slipping issues. With a proper design it could likely be made to work. But perhaps there's some issue with slipping unless extra belt tension is used and then there's too much friction or something. Or perhaps it's as simple as chains can use a master link so they are simply far easier to work with.
              Nope, it will be roughly modelled after a Japanese electric train.



              Hopefully, I'll be clever enough to make it somewhat skin-able, changing the look fairly easily. My first go will be the NEX Train, that runs from the airport into Tokyo... my kid likes that one. His mother in Japanese so he's already been to Japan a few times, and been on that train.

              Oh, and being a biker type, I'll likely put a pantograph on the front that sort of looks like MC handlebars and the riders will basically sit on top, the red being a bench seat just aft of the flared nose. Oh, and running boards for feet behind said nose.

              As for the pulley verses sprocket thing... yeah, I've got a lot of guesses too. I'm just thinking that chain is needed for the big ones and modellers are more into scaling than reinventing Me, I'm pathologically predisposed to going my own way... it's actually a problem at times, not being willing to follow directions. But, I've made it this far, and I'm leaning hard towards pulleys and belts.

              Oh, the motor mount will be the belt tensioner and, besides that, there will only be one bolt (probably a nylock nut on a stud as it has to allow for flex) and both axles of the truck will come free, thus allowing a belt change. Them train engineers have been at it a long time and I'm starting to why they do things... just can't shake the belt idea though.

              David...
              Last edited by fixerdave; 11-14-2016, 01:34 PM. Reason: added picture
              http://fixerdave.blogspot.com/

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              • #8
                Well, it's supposed to be a hobby. So you'll learn something and then adapt if you run into trouble.

                If you're running fairly small size pulleys it may be worth looking at the polyV belts. For no other reason perhaps than you can get a slightly bigger effective diameter within the same outer dimensions thanks to the flatter makeup of the belt. And that larger effective diameter means a little more contact area to offer up more engagement drive friction And there's lots of options for poly V pulleys to be found at an auto wrecker that could be used to adapt to your train. You'd need to source the belt of the proper length though.

                Good luck with it. I'm already looking forward to the pictures of the build.
                Chilliwack BC, Canada

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                • #9
                  Originally posted by BCRider View Post
                  Well, it's supposed to be a hobby. So you'll learn something and then adapt if you run into trouble.

                  If you're running fairly small size pulleys it may be worth looking at the polyV belts. For no other reason perhaps than you can get a slightly bigger effective diameter within the same outer dimensions thanks to the flatter makeup of the belt....
                  Yup, what I meant by ribbed belts. I figure I can easily make a pulley for a ribbed... polyV... belt on a lathe. Way easier than even a standard V-belt. Toothed would be a lot harder though, requiring indexing and (shudder) math, so I'd like to avoid that. I've just ordered a polyV alternator belt for the wife's car... all of $4 (plus some combined shipping) and I can make the design fit (probably) that particular belt. Then, if all goes well, I'll just order a few more. Way easier and cheaper than chain. Probably quieter too; no oiling either.

                  David...
                  http://fixerdave.blogspot.com/

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                  • #10
                    V belts work in cars because they run at high speed low torque. You will want low speed high torque. The reason the steel wheels grip the track is because there is a heavy lead battery weighing it down. You will need a lot of belt tension. Chain is easy and if you look around there are now very cheap sprockets thanks probably to waterjet cutting. UK example provided by His Lordship in another thread elsewhere.

                    For the wheels don't forget to get the club's requirements for flange profile and back to back dimension or you might have problems going over the points (hopefully you don't call them switches in Canada).
                    Last edited by Baz; 11-14-2016, 02:24 PM.

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                    • #11
                      not so fast--

                      Originally posted by Baz View Post
                      V belts work in cars because they run at high speed low torque. You will want low speed high torque. The reason the steel wheels grip the track is because there is a heavy lead battery weighing it down. You will need a lot of belt tension. Chain is easy and if you look around there are now very cheap sprockets thanks probably to waterjet cutting. UK example provided by His Lordship in another thread elsewhere.

                      For the wheels don't forget to get the club's requirements for flange profile and back to back dimension or you might have problems going over the points (hopefully you don't call them switches in Canada).
                      I am not sure but I believe VIME,s track is 7 1/4" gauge. not 71/2" Regards David Powell.

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                      • #12
                        Chain, easier to get the ratios you need without slipping. Max speed of about 8 mph is good. 8 mph is a pretty good clip on 7.5" rails. This hobby is why I got into machining.

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                        • #13
                          .......(hopefully you don't call them switches in Canada)
                          It'll likely depend on what sort of cap the engineer is wearing at a jaunty angle on his noggin....

                          It's tough to ignore the heavy influence of our neighbor to the south in such things. But then again with Victoria being a great bastion of all that is British here in BC perhaps you'll get your wish.
                          Chilliwack BC, Canada

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                          • #14
                            Originally posted by Baz View Post
                            V belts work in cars because they run at high speed low torque. You will want low speed high torque. The reason the steel wheels grip the track is because there is a heavy lead battery weighing it down. You will need a lot of belt tension
                            ....
                            For the wheels don't forget to get the club's requirements for flange profile and back to back dimension or you might have problems going over the points (hopefully you don't call them switches in Canada).
                            Good point about the weight... I guess I'd need to know how much static/rolling friction I'd get with steel on steel, compare it to what I'd get with rubber on aluminium, and then get my factor to compare weight of the car compared to tension on the belt. Hadn't thought of it that way. Dang... back to math. I guess that's why they go toothed belts on some motorcycles.

                            Yup... now I see it. I'm comparing the wrong things. It's not steel on steel verses rubber on aluminium, it's total weight of the car verses levered belt tension. The total weight of the car is going to win.

                            Thank you... I'm glad I asked.

                            Yes, there are cheap weld-on sprockets and chain available locally at Princess Auto (used to be surplus now bulk China importer). Might even be cheaper mail-order, though there's an odd weight to shipping cost transition that takes over after a bit.

                            And, yes, I have the published standard for the wheels, though I'm still going to try something weird with them. Not the part that hits the track but the hubs. I have some salvaged axle tube out of a truck. Basically pipe, but with an internal taper on the wall thickness. My plan is to run a small diameter steel pipe down the center of the larger pipe then fill the void with aluminium... basically cast in place. Then, I'll buck off slices for wheels. So, steel core, aluminium hub, then steel wheel. Should be fun. Might have to drill and screw in something crosswise to keep the steel on the hub but I'm hoping not. Not sure how well the aluminium will stick to the steel, and how it will shrink when cool. Again, I can always go buy solid steel, or even pre-made wheels, if it doesn't work. But, I'm stubborn... and I seem to waste way too much time trying to use salvage material instead of going out to buy new. That's another one of my self-defeating traits.

                            Funny, I'm old enough to see all the ways I make life difficult for myself... but not old enough to do anything about it... or maybe I'm too old to change my ways Whatever, so long as I'm having fun.

                            David...

                            P.S.

                            As I understand it VIME runs standard wheel (and gage) on non-standard rails for both cost-effectiveness (cheap metal instead of formed rails) and less issues with going around corners. Me... I'm just going to build to VIME standards. Seems to work for them, more than good enough for me.
                            http://fixerdave.blogspot.com/

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                            • #15
                              If you pour the aluminium directly into the tube it WILL shrink and let the tube simply slip off. There would even be quite a gap due to the shrinkage. Your ONLY chance for such a thing to work would be to heat up the tube ahead of time to pretty much cherry red and then pour the aluminium and hope that the expansion of the tube is enough so that it shrinks with the aluminium. But I'm not very hopeful of that.

                              If you want to pursue that method you'll need to cast the alloy around the center shaft then mount and turn the alloy down to a size a few thou over the ID of the cut off "tires" of that tapered tubing. Then heat the tubing up until you can rap it home over the alloy wheel which was shrunken in a bucket of ice and water and then let it shrink tight as the alloy grows up to meet it. Over that size of fit you should be good for a 3 or maybe even 4 thou interference fit yet still be able to put it together relatively easily with the heated tire and chilled wheel.
                              Chilliwack BC, Canada

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