Tuesday, 16 August 2016

Sometimes it doesnt always go to plan...

Hello.

Its about time for another post me thinks.
As the title says, sometimes the best ideas and plans in my head don't always work and below is a classic case of that. This time it was inspired by some recent posts regarding the influx of mini motors from China and in this instance some tiny 3x4x12.8mm which were ordered sharpish from here EBAY LINK

After some initial thoughts I came up with the idea of using these as a miniature axle motor and just fit some wheels onto each end. The idea sounded right in my head and once the motors have been delivered I carried out some simple checks just to make sure the ideas would physically work, so far so good.
Next on from this was to find something to motorise using this new design. I had a choice between a small shunter type or a bus. The bus idea appealed to me but at the time a lack of some suitable donor vehicle lead me to try the shunter option. I had an etch for a Ruston 48DS lying about so the basic structure was put together so I had an idea of the volume I had.
To start with I machined up a set of 4 wheels using the lathe. The rims were made from some Nickel Silver and the middles from Paxolin. These were then pressed onto the motor shafts to see what they looked like.
Next was the chassis design and construction which, to be honest sort of 'evolved' as it took some time trying to figure out things like mounting the motors. I came up with a design that looked like it would work eventually though.
At this point I was getting quite excited until it was wired up and tested. Then it became apparent that this design might not be as good as it was in my head. The problem is the motors just arent powerful enough to deal with something like this. The chassis design had wire pickups to the wheel rims and even with these adjusted so they are hardly touching the rims, the wheels refused to revolve at all. If I am having trouble already then the chances of it pulling itself along is negligible.
Its a shame really but I am now thinking it would be best to put this to one side for now and come back to it sometime in the future once I have figured out a better was to motorise it. Things don't always go the way I hoped they would!

Anyway, on a better note, the 14xx is finished (apart from its decoder) and I am extremely happy with the way its turned out (thanks Steve). Thats another engine ticked off my list!
Julia :o)

EDIT:

OMG! I just noticed I havent really explained the 14xx! So here goes...



So, the original boiler was stuffed full of lead but I found it just wasn't heavy enough to pull anything. The idea came to replace the lead with a big slug of tungsten but as all the lead was stuck fast with super-glue I decided to replace the boiler section. This was scratch built with castings fro N Brass and my rivet tool  was used fr the first time to do the smokebox details. The tungsten (recycled dart) was then machined to be a snug fit inside the Brass boiler.

:o)





12 comments:

  1. Really interesting Julia a good read "I thought the idea was a good one
    John

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  2. interesting as always the 48d is not a failure just a return to project I know I have lots of those

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    1. Thanks Nick.

      Yes, I will return to the project sometime in the future. I have already got ideas on an alternative way of powering it but it will have to wait until I get some more bits and bobs.

      J.

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  3. I wouldn't have thought a motor is going to produce enough torque (or indeed any) at such a low revs to act as an axle motor without any reduction gearing. I've seen this done with a 7mm model, but then there was a tiny pinion gear on the motor and as alrage a pinion as the wheel would allow on the axle.

    Either that, or your tiny shunter is going to set off at light speed!

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    1. Thanks for the comment Chris.

      I had a similar thought right at the beginning of the project but I thought it would be worth trying out. The thought of not having to deal with any type of gearing made trying it worthwhile, indeed the construction was so much easier than a geared engine. The idea was to use two motors connected in series and to add a suitable resistor too to help drop the voltage down. As you say, the size of the motor was just too small to generate enough torque to make it a viable option.

      J.

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  4. What an interesting couple of ideas. I'd never thought of using tungsten instead of lead, and if I had thought about it then I would have wondered where to get it from.

    And those micro motors must have a use...

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    1. Thanks James.

      I originally got the Tungsten idea from Stephen Harris but it was a chat Tim Watson that finally persuaded me to try it out. The dart thing seemed like a cheap solution to buying it, especially if you go to any car boots where they normally cost less than £5!
      I am sure the micro motors do have a use. I am now trying to work out what to do with them... :o)

      J.

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  5. Any special tips need on turning tungsten. I think my M7 could do with something similar.

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    1. I was apprehensive at first about turning it, especially as I couldn't pin down what grade darts are normally made of. To be sure I used a tipped tool similar to one of these ( http://www.ebay.co.uk/itm/Set-of-7-SCT-Indexable-Lathe-Tools-6-mm-Shank-Ref-888202-For-Unimat-etc-/331738895014?hash=item4d3d2dd2a6:g:jmoAAOSwCQNWenql ) and I was pleasantly surprised on how easy it was to machine.

      J.

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  6. I found this a very interesting post. I've worked with tungsten in the past, both as a 'heavy metal' and for making super-fine points from tungsten wire. This last technique is described at
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2555190/pdf/bullwho00274-0151.pdf
    and you might find a use for it sometime. I've used it for making micro-probes to connect to semi-conductor chips. Fishing weights are another potential source of tungsten for model-makers.

    I wasn't too surprised that your tiny motors could not work with direct drive but, like you, I think it's always worth trying things - it's all part of the 'learning curve'. Perhaps you could arrange some sort of rim-drive to the wheels from the small diameter motor shaft? An inner rim could be provided on your paxolin centres, behind the wheel flanges themselves.

    Looking forward to your next post :)
    Mike

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    1. Hi Mike.

      I have just had a read of that article you posted a link to and its interesting stuff. I didn't realise such a low voltage applied to a piece of wire could have such an effect. With regards to a supply tungsten I have found darts to be a useful source, especially if they are found at car boot sales or similar.
      I have a couple of ideas for motoring the 48ds thing using gearing. When it will happen is another thing as my enthusiasm for it has waned a little now.

      J.

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