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TOPIC: Teaching model

Teaching model 13 Oct 2019 04:33 #203467

  • grandad
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This is a vintage teaching model showing the operation of a mechanical braking system on a drawbar trailer
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Teaching model 13 Oct 2019 04:38 #203468

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Teaching model 13 Oct 2019 08:14 #203471

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Grandad,
that is a great historical model and definitely worth keeping and displaying at shows.
I have my shoulder to the wheel,
my nose to the grindstone,
I've put my best foot forward,
I've put my back into it,
I'm gritting my teeth,

Now I find I can't do any work in this position!

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Teaching model 13 Oct 2019 11:11 #203482

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Grandad

What a good subject! Big difference between hearing and seeing when you are trying to learn something. Here are a few more.

Lang
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Teaching model 13 Oct 2019 20:27 #203485

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A bit more on the trailer-
If the trailer becomes detached from the towing truck the safety chain lifts this catch to allow the spring inside the tube to put the brakes on.
The wheels and brake drums have slots in to be able to see how the brakes work
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Teaching model 13 Oct 2019 20:45 #203487

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Morris, I get a lot of interest at shows with these models and it's surprising how many youngsters like to know about them too.
I can put up some more pics of them if you like
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Teaching model 14 Oct 2019 05:27 #203498

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Very well built models
To see and feel and push and pull etc is a great way to learn things

A lot different than watching a iPhone app

Grear stuff grandad and please keep on sharing, I find this stuff very interesting

Paul
Your better to die trying than live on your knees begging

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Teaching model 15 Oct 2019 09:01 #203534

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Ya,

Even for those among us that already know everything there is to know, can have a bit of a play, a push and a prod and (quietly, silently) finally, after all these years actually Understand how it all works (true knowledge).

Thank you to all those model makers tinkering away in their mini toolmakers man cave workshops.

-b
Mucking about on the edge
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Teaching model 16 Oct 2019 07:44 #203571

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Another model, this one shows the workings of a four stroke engine

Ignition too!

Interesting throttle
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Teaching model 16 Oct 2019 08:15 #203572

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Here is something a bit more modern Pratt and Whitney PT6 Turboprop.

It needs the explanatory drawing for those not in the game. The air comes in the back of the engine (blue) and and is seriously compressed by the axial and radial compressor blades. It runs forward and fuel is ignited in the combustion chamber just before the compressor turbine. This creates huge pressure which A. keeps the cold air section turning via the shaft from the compressor turbine This makes the action totally self sustaining until the fuel is cut off. B. Expands forward through the power turbine blades which drive the geabox and prop.

Turbine engines are controlled solely by a fuel "tap". The more fuel you put in, the bigger the fire behind the compressor turbine, the bigger the expansion and the greater the power. The pilot is restricted either by temperature (too much fuel and blades start to melt) or torque which if too great will start to break things in the gearbox. The two gauges are watched closely on take-off or climb and according to whether it is a hot or cold day when one reaches the red line you can not push the throttle any further.


Interesting thing about these free turbines is there is no mechanical connection between the jet engine power section and the drive to the gearbox. It is just two turbines facing each other. Just like putting two house fans together, switch only one on and the airflow will soon have the other turning at the same rate as the powered one. It is easiest to see when a turbine helicopter starts up. You can hear the engine whining at full speed while the blades slowly catch up until they are "locked" to the engine speed by the compressor and power turbines coming in to synchronization. Many automatic transmissions operate on the same system but with fluid instead of gas.

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