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Dean, it's probably dumb luck that the two drives on the piece I'm working
on have little slack. Yet, with LEGO beams and blocks you can't use every
gear combination; there are published beam/block/plate combinations that let
this or that pair of gears mesh. Someone will do that for chain, someday.
There's another thing you should have mentioned: The less chain slack the
greater the force between shafts and associated friction.
Regards, Jerry
>
> You're kidding, right? It's almost impossible to build a geartrain using
> the chain that doesn't have tons of reversal delay. The links seem to be
> designed in such a way that they don't work well with technic beams and
> gears. I always have quite a bit of chain slack.
>
> > Also, the chain is beautifully made. When I show it to people, they don't
> > want to give it back. They want to play with it...!
>
> With this I fully agree.
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In lugnet.robotics, Jerry Kalpin writes:
> Dean, it's probably dumb luck that the two drives on the piece I'm working
> on have little slack. Yet, with LEGO beams and blocks you can't use every
> gear combination; there are published beam/block/plate combinations that let
> this or that pair of gears mesh. Someone will do that for chain, someday.
Believe me that I have tried a lot of combinations. Also your and my idea
of "little slack" may be quite different. But it is true that I have never
done an exhaustive study on the subject. I usually just give up on getting
it perfect and rig up some sort of chain tensioner.
> There's another thing you should have mentioned: The less chain slack the
> greater the force between shafts and associated friction.
As far as I know, all the available techniques for taking the play out of a
drive train sacrifice efficiency when doing so. The more sophisticated just
do so to a lesser degree. I agree with you that this is really noticable
with a chain. Especially when the load is great enough that shafts start to
bend and the sprockes no longer reside in the same plane.
It's really hard for me to fault Lego for the sloppy mesh of their gears.
Not when you consider their per unit price. I imagine that some of the slop
is intentional for purposes of reducing friction. We are working with puny
little motors after all. If you wan't to limit backlash, just use the big
gears and remember it is a building "toy".
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> It's really hard for me to fault Lego for the sloppy mesh of their gears.
> Not when you consider their per unit price. I imagine that some
> of the slop
> is intentional for purposes of reducing friction. We are working
> with puny
> little motors after all. If you wan't to limit backlash, just use the big
> gears and remember it is a building "toy".
It's not the unit price, but the primary motivation for Lego products: It's
a toy for kids. Yes, it has found some applications in education and amateur
robotics, but it's still a toy. To build exact mechanisms, you not only have
to deal with gear backlash, but also with joiners that have play (or
wiggle), and axles that can be twisted and bend easily. Take the Silver
Champion Technic set for example. Hold one front wheel tight, and see how
far you can turn the other one. Without using too much force, you can turn
it 45 degrees! You can also tilt it at least 20 degrees! It doesn't really
need a suspension!
There are construction systems out there that are much better suited for
mechanical constructions. Fishertechnik is an example. The Mondo-tronics's
Robot Store (http://www.robotstore.com) carries some sets in the U.S.
Fischertechnik uses solid metal axles, and in general is much stronger, with
no flexing and bending. But Fischertechnik doesn't have the large market
share that Lego enjoys, and therefore, it's much more expensive. And there
are no mini-figs, Silver Champions, cool trains, etc. Go to
http://www.fischertechnik.de for full details. The site has a checkbox to
switch to English.
Tilman
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In lugnet.robotics, Eric Sophie writes:
> Listen guys, I'm not playing around with a "Building toy" here,
>
> look,
> When working - creating on this scale, you begin to demand the highest
> preformance from all aspects of Lego.
Looks like toys to me. Really incredibly cool toys!
Tilman's post supporting my "Toy" claim mentioned how torsionally flimsy the
technic axles are. This could be used to take the backlash out of a gear train.
Pull out four 48 tooth gears, two 8 stud technic beams, and two 8 stud
technic rods. Mesh two of the 48 tooth gears by sliding them onto the rods,
and inserting the rods into the holes of one of the beams. Slide the second
beam over the other end of the rods and attach the remaining gears to the
open end of the rods. If everything is aligned properly, the gears will
rotate freely, and there will be a little bit of play. While the gears on
one side are meshed, disengage one of the gears on the otherside, rotate it
one tooth, and reengage. The gears no longer rotate as freely, but there is
no longer any backlash. Slip 3 or 4 teeth and the gear train begins to get
really stiff.
Nothing too brilliant, but it does the job. Probably not all that original
either, but it just occurred to me.
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Rrrrrrrrr.....
In lugnet.robotics, Dean Hystad writes:
> In lugnet.robotics, Eric Sophie writes:
> > Listen guys, I'm not playing around with a "Building toy" here,
> >
> > look,
>
> > When working - creating on this scale, you begin to demand the highest
> > preformance from all aspects of Lego.
>
> Looks like toys to me. Really incredibly cool toys!
>
> Tilman's post supporting my "Toy" claim mentioned how torsionally flimsy the
> technic axles are. This could be used to take the backlash out of a gear train.
>
> Pull out four 48 tooth gears, two 8 stud technic beams, and two 8 stud
> technic rods. Mesh two of the 48 tooth gears by sliding them onto the rods,
> and inserting the rods into the holes of one of the beams. Slide the second
> beam over the other end of the rods and attach the remaining gears to the
> open end of the rods. If everything is aligned properly, the gears will
> rotate freely, and there will be a little bit of play. While the gears on
> one side are meshed, disengage one of the gears on the otherside, rotate it
> one tooth, and reengage. The gears no longer rotate as freely, but there is
> no longer any backlash. Slip 3 or 4 teeth and the gear train begins to get
> really stiff.
>
> Nothing too brilliant, but it does the job. Probably not all that original
> either, but it just occurred to me.
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Sorry Eric. I certainly didn't mean the word "toy" to be derrogetory in any
way. Must be a cultural thing. My job is to create room sized "toys" which
weigh several tons, contain thousands of kilowatts of potential and/or
kinetic energy, and require special connections to local electrical
substations. When the creation is cool, it is referred to as a "toy". A
"machine" is a boring thing which does not stir the soul.
So once again I say of your inventions. Those are really cool toys! Take
it in the spirit it was given.
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Mmmm, you are indeed respectful. Thanks, wow, So when we have made our
masterpieces we sit back and enjoy our toys, for our mind, body and soul
extensions. I like that! Very good.
Man's gotta have his toys ya know.
or
The more money the bigger the toys. etc....
Recv'd in the manner it was given.
I thank you.
Eric
In lugnet.robotics, Dean Hystad writes:
> Sorry Eric. I certainly didn't mean the word "toy" to be derrogetory in any
> way. Must be a cultural thing. My job is to create room sized "toys" which
> weigh several tons, contain thousands of kilowatts of potential and/or
> kinetic energy, and require special connections to local electrical
> substations. When the creation is cool, it is referred to as a "toy". A
> "machine" is a boring thing which does not stir the soul.
>
> So once again I say of your inventions. Those are really cool toys! Take
> it in the spirit it was given.
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In lugnet.robotics, Eric Sophie writes:
> Rrrrrrrrr.....
>
> >
> > Nothing too brilliant, but it does the job. Probably not all that original
> > either, but it just occurred to me.
Doh!. And I just took this in school (in fact, am going to write an exam which
this will appear on (methinks) thisafternoon. It's called "Locked Train", and
allows for more even power distribution across multiple gears in a gearbox.
Hmm...Now I suppose I am going to have to model a DDG 280's gearbox out of lego
as penance?
James
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Good luck!!!
> Doh!. And I just took this in school (in fact, am going to write an exam which
> this will appear on (methinks) thisafternoon. It's called "Locked Train", and
> allows for more even power distribution across multiple gears in a gearbox.
>
> Hmm...Now I suppose I am going to have to model a DDG 280's gearbox out of lego
> as penance?
>
> James
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