Subject:
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Re: APT tilts thru curves in Real-Build ABS form
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 25 Jun 2001 23:27:44 GMT
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Viewed:
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1515 times
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In lugnet.trains, Iain Hendry writes:
> "James Mathis" <thakius@nmt.edu> wrote in message
> news:GFI7GG.36J@lugnet.com...
>
> > 1) The train cars do indeed tilt through curves. The pendular axis of
> > rotation is just below the roof-line; thus, the car bodies swing "out"
> > rather than tip "in". I'm not sure that is the best way to describe this
> > motion???
>
> That seems to make sense. CN's original "Turbo" exhibited this
> characteristic; today, the TALGO tilting trainsets also tilt this way. I
> don't know of a lot of passive systems able to tilt inward; but I think that
> ABB's trapezoidal linkage leans more toward the centre, while remaining
> inherently passive...
>
> (does that make sense? From a physics standpoint, maybe it doesnt...! I'm
> not sure.)
I'm actually very ignorant as to how the real APT tilts. What little I do
know makes me think that the pendular axis is very low; maybe just above the
bogie near the floor? I think the APT used a very active forced-tilt with
some kind of feed-back sensors and computer system to actively tilt the
wagon body's. I think I read somewhere that the original mechanism was TOO
instantaneously corrective, and it tilted back and forth in response to
small irregularities in the track that it made people ill! They relaxed
the feedback response interval(?) to slow the tilt down I think.
> > 3) The height of the train is equivalent to a standard official LEGO
> > passenger train.
>
> That's really amazing! That's fantastic you're able to fit the hardware into
> such a compact space.
The mechanism is really quite simple. Just a force lever arm on a camshaft
so the body can "lift" away from the surface of the bogie plate.
Getting the pendular axis and the bogie/wheel axis in just the right places
so the wheels wouldn't pop out of the track under load through a curve was
the real "trick".
> > I found it a little difficult to photograph the tilt. I hope some of the
> > pictures convey that it really is tilting!
>
> I supose this picture exhibits it the best:
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?i=51171
>
> Is that the appr. maximum tilt angle achieveable? I'm very intrigued by your
> pendular mechanism. :)
Yes, that photo of the driving unit is with it in a full curve; both front
and rear bogies at full curve-track rotation.
The tilt mechanism handles curvey-curves. There is enough "lift" in the
camshaft so that opposite curve forces kind of push the whole body (front
and rear) up. Which ever side imparts the greatest force (torque) tilts the
wagon in that preferred direction.
Each tilt mechanism is about 5 bricks tall by 4 studs square. Fits behind
the blue train doors. If you don't want it to tilt, you just pop off one
piece at each end of the shared bogies. In this way you can make individual
wagons fail to tilt; just like individual wagons in the real APT test runs
failed to tilt! ;-)
> Again, James, you amaze me! Thanks for sharing your brilliant work.
>
> Iain
What's a hobby for? Glad you enjoy it! :-)
later,
James Mathis
PS: I wish I had a mini-movie digital camera. It is quite fun to watch
this APT run through a circuit. Top speed is one "notch" below maximum on
the 9v train speed regulator. However, this is without a huge straight-away
leading into a full curve; so curve entrance speeds may be lower. I run the
set with two 9v train motors in the single non-driving power car.
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Message has 1 Reply:
 | | Re: APT tilts thru curves in Real-Build ABS form
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| (...) Like many things - it's simple once you know how. It's the figuring it out the first time and/or having the original idea that is the difficult/challengin...nteresting part. (...) <snip> (...) I must echo this sentiment - this is amazing work. (...) (23 years ago, 21-Jul-01, to lugnet.trains)
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Message is in Reply To:
| | Re: APT tilts thru curves in Real-Build ABS form
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| "James Mathis" <thakius@nmt.edu> wrote in message news:GFI7GG.36J@lugnet.com... (...) That seems to make sense. CN's original "Turbo" exhibited this characteristic; today, the TALGO tilting trainsets also tilt this way. I don't know of a lot of (...) (23 years ago, 25-Jun-01, to lugnet.trains)
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