Subject:
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Re: Chain Precession Drive - Courtesy of TechnicBRICKs
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 23 Mar 2009 21:14:47 GMT
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Viewed:
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25438 times
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In lugnet.technic, William Leue wrote:
> In lugnet.technic, Mike Hatton wrote:
> > In lugnet.technic, William Leue wrote:
> > > Owen and Mike,
> > > The 2825 part connects the input shift with the orbiter. The part that was shown
> > > in the original LDRAW model clearly does not work because all its holes are
> > > round and so there is no way of transferring torque to the orbiter body. The
> > > 2825 part has a cross hole at one end, which takes the drive axle, and one at
> > > the opposite end, which takes the axle 2 slotted, which in turn is mated to the
> > > Technic bushing and forms the orbiter itself.
> > >
> > > I discovered this when I tried to build an actual physical model from the LDRAW
> > > model and discovered the problem, so I am quite confident that the LDRAW model
> > > is incorrect as shown.
> > >
> > > -Bill
> > >
> > > > > Bill.
> > > > >
> > > > > Perhaps you could elaborate on that a little? I can't see that part working
> > > > > there at all - the 2825 part has crosses at both ends, and you need the axle
> > > > > attached to the gear to be able to rotate freely.
> > > > >
> > > > > Owen.
> > > >
> > > > Apologies for not having part numbers to hand..
> > > >
> > > > You did mean the 1x5 not the 1x4 liftarm? if so Owen is right the cog must turn
> > > > freely hence the excessive 1x5 liftarm. I would be interested to see if you have
> > > > a working redesign...
> > > >
> > > > If you meant to replace the '1x4 liftarm' and a 'bush' with the '1x4 liftarm
> > > > with boss' and a 'half bush' then you will have a clearance issue with the cog
> > > > teeth. The bush is the only part that will clear the teeth and keep the correct
> > > > tension for clearing 4 teeth per turn, if you use just an axle the tension is
> > > > inadequate and you may clear either 3 or 4 teeth per turn making it a bit
> > > > random..
> > > >
> > > > I have built a 6:1 ratio drive around a 24 tooth gear this uses a 1x3 liftarm
> > > > and a 1x4 liftarm (again offset for the smooth hole) this uses just an axle (no
> > > > bush) for the correct tension.
> > > >
> > > > Regards
> > > >
> > > > Mike
> >
> >
> > Only the input side of the orbiter is connected to a shaft (via 1x4 liftarm) the
> > output shaft turns freely (via 1x5 liftarm) inside the orbiter and connects to
> > the Cog Only.
> > It should be as shown here:
> > http://www.brickshelf.com/cgi-bin/gallery.cgi?f=297233
> >
> > I dont have Ldraw installed on this pc at the moment I could you confirm if it
> > is different to these picture instructions.
> >
> > Regards,
> > Mike
>
> I agree: the input side is connected to the orbiter; the output shaft connects
> only to the cog. That is exactly the way mine is built. Where I disagree with
> the LDRAW file is the nature of the liftarm: what is shown is a 1x5 liftarm with
> only round holes. This can't work. If you try to build a model directly from the
> LDRAW file, you will see the problem immediately. My model, using the 2825 1x4
> liftarm, works perfectly.
>
> -Bill
Bill
Are you missing a part from the ldraw library?
32449.dat is a 1x4 liftarm (without boss) and is in the model
as pictured here:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=297233
(Yellow Part)
Regards
Mike
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Message is in Reply To:
 | | Re: Chain Precession Drive - Courtesy of TechnicBRICKs
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| (...) I agree: the input side is connected to the orbiter; the output shaft connects only to the cog. That is exactly the way mine is built. Where I disagree with the LDRAW file is the nature of the liftarm: what is shown is a 1x5 liftarm with only (...) (16 years ago, 23-Mar-09, to lugnet.technic)
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