Building a Metro train from a tamiya kit?

[Bdongyface 28]

I have been building tamiya cars for a while now as a hobby, but for the first time I have been asked to do something similar for work! I work as a set builder at a theatre and have been asked by the designer to build him a radio controlled Parisian metro train. The train needs to drive forwards and backwards across the front of the stage and into a tunnel at each end. I have only ever built standard tamiya kits, so a custom build is quite a big step up for me. I was hoping to get some advise as to how to start. I had initially thought of using an M-chassis car to contain all the electrics and motor and then find a way to connect a few more pairs of wheels along the length of the metro. It doesn't need to steer, just drive forwards and backwards at the same speed with lights on front and back. I will be building the shell from styrene or a more light weight board.

The dimensions the designer is hoping for 150mm wide / 150mm tall / 1500mm long

I am aware that it may become quite heavy, but it doesn't need to drive that fast. Would a 4wd option such as the mf01x help, or does this make it more complicated? I could make aluminium chassis rails and attach axels to that, but I am not sure what type of axels to be looking for. Any help or advice as to where to focus my search and design would be greatly appreciated. The budget for the train is not huge, but I have a few hundred euros to spend on parts.

I would love a few pointers from anyone out there if you have any initial thoughts or ideas.

 

[Jonathon Gillham 4605]

Sounds like a fun project!

Check out some of the builds by JennyMo she she does scratch builds using various commercially available parts like axles and chassis rails.

Look at aliexpress and banggood for components. I built a tank with my 6yo son using a tracked chassis from banggood with little 190 sized brushed motors, some $7 ESCs and cheap servos and it all came together nicely with 6ch Flysky FS-i6 radio gear. (He made the body using cardboard and paper mache). I've also picked up components for a little powerboat for not muxh $$ like rudders, universal joints, prop shafts etc.

I'm sure you'll be able to find axles which are the right width, driveshafts to connect them, couplings for the carriages etc for not much money. Its amazing what is available - there may even be some kitsets available, or a 1/18 scale car may be a better base. I'm also assuming it only needs to work for a week or 2...

[Tizer 606]

M-chassis would be around 160mm wide, so close to the specs you need. Having a 2WD car will make it a lot easier for you to play around with the wheelbase as you don't need any power going to the other wheels, meaning getting longer/shorter driveshafts or belts and having everything aligned properly.

Something like an M03 would be great, because everything you need is contained in the front part of the chassis. Motor, gearbox, front suspension, steering and even the battery. It also has easy mounting tabs on both the front and back (where the bumper or back half of the chassis normally go) to bolt other stuff to for your custom build. Plus it's cheap!

[Hobgoblin 1059]

I would be tempted to add in like a high voltage (12v ish, relative) 550 motor and perhaps add in an additional stage of reduction 3:1 crawler style planetary thing.  That will give you the torque for sure. 

If that isn't enough and you need to go custom  then I would suggest the motor and gearbox from a cordless drill. Super cheap and high torque! 

[Honza 931]

If you don't need steering, suspension etc, M-chassis is too complicated. I'd use rear pod from F103/104, no differential, simple axle with exact width you'll need. Real trains use very similar layout, so it'll have some scale aspect, too.

[JennyMo 3526]

Hi Bdongyface - I would drop @MadInventor a message - he's your guy when it comes to scratch building huge long vehicles (see his War Rig from Mad Max:Fury Road for example) - and he ought to be able to advise how best to construct the underpinnings for what you propose?

Jenny x

[speedy_w_beans 4272]

10 hours ago, Honza said:

If you don't need steering, suspension etc, M-chassis is too complicated. I'd use rear pod from F103/104, no differential, simple axle with exact width you'll need. Real trains use very similar layout, so it'll have some scale aspect, too.

I like where you're going with this, except maybe RM01 instead of F103/F104 for slightly narrower (M-chassis) 160 mm width?  It would be relatively easy to cut some fresh FRP for a longer chassis plate, use the RM01 rear pod like you say, and then add several rows of RM01 front arms for as many fake axles as needed.  Then you'll need some sort of body mounted on top of it, maybe even screwed to the FRP chassis.

[Honza 931]

I was thinking of F104, because it can fit low RPM 540 motor or 380 with extra gearbox, which should provide enough power at low speed. Width isn't issue, gearbox itself is narrow, custom axle made from 5mm rod can place wheels very close to it (it just needs to drill hexes and wheels to 5mm) Non powered axles can be made similarly, no need to buy whole chassis.

When I look at paris metro boogies, it looks like mini4wd. Is there something slightly bigger?

[Bdongyface 28]

Thank you for your replies and suggestions so far. I like the look of the F104, it does have a very simple layout, that could well be a good starting point. I am currently working on some other elements for the show, so I still have a few more days to figure out what parts I will need. The other thing I need to figure out is some kind of track and guide system. I will visit the local hobby shop soon and see what parts i can get hold of easily, as that may well dictate the direction this build goes in. Will I have problems that forward and reverse are different speeds?

[Busdriver 6209]

Try looking at G (garden) scale railway. Tracks running gear the lot. Expensive new but usually quite a bit second hand on fleabay etc.