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Discussion Starter · #1 ·
Hello Everyone,

I'm slightly ashamed that I havn't even picked up a model train since I was about 14. However I have a big plan for a setup at the top of the garage when my son gets older (he's 12 weeks so it's going to be a while).

I got a call yesterday from a client who wants to do some filming in a model railway .. he saw the "TV licencing" job I did and wanted to do something similar (I'm sure you have seen the commercial it's a city made out of circuit boards with "We know where you are and we're coming to get you").

It's kinda easy to do that sort of thing with a crane and a periscope and a prism. But it has drawbacks .. You can't go through a tunnel for instance.

As the production only want Standard Definition video I think it might be possible to mount the camera on a train and shoot the train journey "for real".

So I have 100 questions and about 50 problems to overcome ..

My big problems come from the fact that I have never seen the trainset and I can't get out of the client what the guage will be. Apparently the setup is 90cm by 90cm and it is a "proper" model railway (By which I'm guessing they mean not a battery operated toy).

However !

I have an idea that I would like to run past anyone here who would like to comment ..

The shot the production want is travelling along the track from the front of the train .. For various reasons powering the train via a motor with the current coming up from the track is a non starter. I need to be able to repeat the move perfectly ....

SO ..

If I make a bogie with the camera built onto it and then modify the model so that instead of being a siding the track extends out 2 metres to the side of the setup. The idea would be to make a 2 meter long train and then push this along the track with a motion controlled dolly.

Question ..

How long can I make a train without being concerned that it will derail? Is 2m possible ?

Justin Pentecost

www.portablemotioncontrol.com

South Oxon
 

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QUOTE (Justin Pentecost @ 26 Jun 2008, 03:34) <{POST_SNAPBACK}>Question ..

How long can I make a train without being concerned that it will derail? Is 2m possible ?

Justin Pentecost

www.portablemotioncontrol.com

South Oxon
Yes it is possible but factors to consider are the type of track used, how well it has been laid, the flanges on the wheels, does it go over any points and how flat is the surface it has been laid on.

These variables will all affect the reliability in one way or another.
 

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***Hi

Length is not a problem - 2m is a relatively short train if the track is appropriate - BUT - 90cm x 90cm is quite small - that makes the gauge 16.5mm max, 9mm possible. It also only gives you a maximum appx 3 metres to the full circle so the end of the train will be pretty close to the front!

Hope for the larger gauge, as if its in 16.5/OO scale or similar then reliable tracking and smoothness of movement will potentially be of a much higher quality that 9mm/N scale.

I suspect that pushing the train with a motion controlled dolly will be exceptionally difficult to get smooth - Pushing is a worst case for smooth motion as the mass of the train will be extremely small and there's likely to be a lot of forward/rearward jerkyness compared to using a high quality locomotive digitally (DCC) controlled, which would allow it to move along under its own steam in a smooth and very controllable fashion to synchronise with the movement speed of the camera.

(DCC control allows adjustment of overall loco speed range limits which allied to 128 possible speed steps would therefore allow matching to dolly speed very easily - anything from about 100mm / minute upward can be done no problem)

This will also remove a major variable in that if pushed, as Neil said, variances in tracklaying quality may compromise quality and it sound like thats a variable U have little control over.

Doing it that way will also remove (a) the need for absolute precision in the arc of motion of the camera vs train and (
it will lessen the direct interdependency of camera and train, which must be a bugger to get right with a tight shot and close to macro type settings - it will also end up leaving U much more flexibility in focal length & general filming.

Regards

Richard
DCCconcepts
 

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QUOTE (Justin Pentecost @ 25 Jun 2008, 17:34) <{POST_SNAPBACK}>I got a call yesterday from a client who wants to do some filming in a model railway .. he saw the "TV licencing" job I did and wanted to do something similar (I'm sure you have seen the commercial it's a city made out of circuit boards with "We know where you are and we're coming to get you").
Justin Pentecost

Hello justin. richard will be better with the questions but i just want to welcome you to the forum!

I got that COI filler but i dont think we played it out on our channel more than a couple of times. (its still on the server though!) the recent fire safty ones seem to be in fasion with the schedulers!

Regards

Peter
 

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Discussion Starter · #5 ·
That's superb !

Thanks very very much, I've told the client that it should be possible. They are going to get back to me with the guage.

The massive advantage of this job is that as I can varispeed the whole thing I can shoot it at 1fps (1/25 of screen speed) which should give me the smoothest move. (there is no speed reference within the set).

I also had a great idea .. if I combine my motioncontrol drive with a DCC controlled loco I can in theory do a tracking shot with the loco following the camera. (The motion control dolly drive is a 55V 1050W motor and drive with a 5000 PPR encoder giving via a gearbox hundreths of a MM precision Max speed is 3 m/s and minimum speed is pretty much as low as you want to go .. 1mm/hour easily).

I'll get back when I know more ..
 
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