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, 23 Jul 2001 16:15:04 GMT
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Viewed:
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2122 times
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In lugnet.trains, Steve Chapple writes:
> In lugnet.trains, James Mathis writes:
> > In lugnet.trains, Iain Hendry writes:
> > > "James Mathis" <thakius@nmt.edu> wrote
> > > > 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...
> >
> > I'm actually very ignorant as to how the real APT tilts...
>
> > > 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...
>
> 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/challenging/interesting part.
You are so correct. I have thought of how to achieve this pendular effect
ever since Eric Brok showcased a working solution with modified Metroliner.
So, that's been a few years!
Simple: Well, even sometimes the realized solution is not actually "simple"
in terms of parts and construction; sometimes the working solution can be
rather complicated. However, this tilting mechanism is not very complicate,
in my very humble opinion.
> > > Is that the appr. maximum tilt angle achievable? I'm very
> > > intrigued by your pendular mechanism. :)
Hmm, I've not measured it. The side of the car that lifts off of the bogie
plate is raised by about one plate. That would be a rise of one plate over
a run of 6 studs, as the train cars are 6-wide. The angle would be equal to
the arctan[(one plate)/(six studs)]= arctan[(~3.2mm)/(~48mm)]= 3.8 degrees.
Hmm, that seems a bit large. Or, if 3.2mm includes the height of the stud,
then the angle should be a little less: about 3 degrees.
I didn't measure the dimensions myself. I took data from the faq at:
http://www.multicon.de/fun/legofaq.html#a13
under item #13 for dimensions. The the thickness of one plate I took the
specified "height of brick =9.6mm" and divided by 3. But, I'm not sure if
the "height of brick=9.6mm" included the height of the stud. The stud
height is listed as 1.7mm.
Prototype pendular mechanism:
Here is a link to a very early forced-pendular mechanism.
http://www.nmt.edu/~thakius/pendular_v1.html
For the first design study, I was trying to make a CAD version, as well as a
real-build version. I've gotten lazy. I can't remember if the design as
shown in the above pics worked as well as some other slight variations to
the design. :-( Sorry. But, perhaps you can tinker with the design and see
it work for yourself. :-)
The APT's pendular axis stretching camshaft is similar, but the action lever
is not the same. The APT cars have shared 2 axle wheelsets. This
necessitated some design changes to the lever that pushes the cars into a tilt.
> I must echo this sentiment - this is amazing work. While typical LEGO
> creations are of some interest, making something new that's never been
> done before - particularly to solve a "problem" of some kind (like this) -
> is what _really_ interests me! Hence my first and only LEGO arches,
> http://216.18.91.29/SRC/LEGO/Arches and being the first (AFAIK) to
> make monorail spirals. This kind of innovation doesn't seem to have much
> impact on "the masses" though. It's a bit disappointing when others don't
> seem to share ones enthusiasm for something when you think they would.
Oh, yes, I remember these arches. Very cool. You have rediscovered the
Chinese "Rainbow Bridge" from some centuries ago! :-) I don't recall from
what Dynasty this bridge comes. The PBS tele show NOVA showcased a group
from MIT collaborating with a Chinese bridge engineer to build such a bridge
in a village in China. They hoped to answer the question: "Is the bridge
an 'arch' or a 'beam' construction?" The bridge uses interlaced beams to
create an arch, just as you have done (or do I miss a subtlety of your
construction?). Very clever! I think the LEGO medium illustrates
real-world constructions very well!
> I applaud your creativity and am interested in Technic-al engineering
> details. :-) By the way, the alternate mono-rail car attachment
> method - am I remembering that correctly as yours too?
If you have further questions regarding the pendular design, please let me
know. I should tell everyone that the balance of the wheels and car seems
to be important. I don't know how to describe it any better than "balance";
as it is the force of action between the train track rails and the inner
flange of the train wheels that applies the force to both lift and tilt the
car body. Thus, an "out of balance" construction will result in the train
wheels popping off the the rails.
One can alter this construction to raise the car body off the bogie by one
plate thickness. This puts an air gap between the wheelset bogie plate and
the platform of the car body. Now, when the car tilts, the wheels no longer
have to lift the car body up. The force to tilt is much lower than the
force to lift, so the concern of the wheels popping off the rails is much
reduced.
I did make a close-coupled mono-rail car attachment method. Once again,
original inspiration came from Eric Brok who showcased using the Technic
spring brick in his green crocodile locomotive.
later,
James Mathis
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Message is in Reply To:
 | | 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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