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Hi all,
I've got an intriguing little MOC coming up that hopefully will interest
both the technicheads and the robogeeks. It is a tracked vehicle with a
twist, but you'll have to wait to learn all the details ;-)
In the meantime, here is something I could use some help on. For precise
operation, I'm using a dual differential drive as described by the Ferrari
brothers in their book. My setup is farily different from theirs, mostly
because I need to save space. I've uploaded to brickshelf 2 dats and 4 POV
jpegs of how it looks right now. You might want to take a look.
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=13856
(For those of you who, like me 4 months ago, don't know what a double
differential drive does, it's a mechanism that mechanically links 2 motors
to an axle so that one motor rotates both wheels on the ends of the axle in
the same direction and the other motor rotates them in opposite directions.
In practice, this means that a vehicle fitted with this drive will go in a
stright line if one of the motors is used or rotate in place if the other is
activated. If both motors are activated, rotation still occurs.)
So, a couple of things about my design. First, it's meant to be as small as
possible. Second, the two input axles (yellow and green in the jpegs) rotate
the output axle (blue) at different speeds - the green one uses a double
bevel 20 tooth gear/24 gear crown combination for reduction, the yellow one
a 8/24 tooth combination. I have not attached motors to this drive, but
nothing seems to break or even creak when I rotate the axles with my fingers
in any direction simultaneaously.
Anybody can come up with a more compact design? Can anybody solve the dual
speed issue? I could add studs in width (distance between wheels) and one
stud in height to what already rises above the wheel axle (and maybe another
stud below). Height is critical, but losing some length is even more so.
OK, I hope you enjoy it and come up with some ideas.
Chao for now!
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In lugnet.technic, Miguel Agullo writes:
>
> Anybody can come up with a more compact design? Can anybody solve the dual
> speed issue? I could add studs in width (distance between wheels) and one
> stud in height to what already rises above the wheel axle (and maybe another
> stud below). Height is critical, but losing some length is even more so.
Well, I think several people have delved into this, but here's my contribution
http://www.lugnet.com/~469/projects/addsub. It doesn't solve the "dual speed"
problem, but it's fairly small, and can be reduced further.
ROSCO
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In lugnet.technic, Ross Crawford writes:
> In lugnet.technic, Miguel Agullo writes:
> >
> > Anybody can come up with a more compact design? Can anybody solve the dual
> > speed issue? I could add studs in width (distance between wheels) and one
> > stud in height to what already rises above the wheel axle (and maybe another
> > stud below). Height is critical, but losing some length is even more so.
>
> Well, I think several people have delved into this, but here's my contribution
> http://www.lugnet.com/~469/projects/addsub. It doesn't solve the "dual speed"
> problem, but it's fairly small, and can be reduced further.
>
> ROSCO
Thanks a lot, Rosco. I think I'm going to go with Stefano Prosseda's
variation, which you also mention on your webpage
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=9341
I clearly didn't quite understand the concept and now see how my design had
way too many gears only to accomplish something totally unnecessary: feeding
input force to both axles of the diffrentials, instead of one axle and the
diff body and using the other axle for the outputs.
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> Thanks a lot, Rosco. I think I'm going to go with Stefano Prosseda's
> variation, which you also mention on your webpage
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?f=9341
>
> I clearly didn't quite understand the concept and now see how my design • had
> way too many gears only to accomplish something totally unnecessary: • feeding
> input force to both axles of the diffrentials, instead of one axle and the
> diff body and using the other axle for the outputs.
I made also a "one-way" version, it's built in the undercarriage of this:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=14512
It's basically the one above, but with two gearboxes at the input ports.
In this way, I think the best design it's undoubtly the Doug Carlson's one
http://www.visi.com/~dc/transmission .
ciao
ste
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In lugnet.technic, Miguel Agullo writes:
> Hi all,
>
> I've got an intriguing little MOC coming up that hopefully will interest
> both the technicheads and the robogeeks. It is a tracked vehicle with a
> twist, but you'll have to wait to learn all the details ;-)
>
> In the meantime, here is something I could use some help on. For precise
> operation, I'm using a dual differential drive as described by the Ferrari
> brothers in their book. My setup is farily different from theirs, mostly
> because I need to save space. I've uploaded to brickshelf 2 dats and 4 POV
> jpegs of how it looks right now. You might want to take a look.
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?f=13856
>
> (For those of you who, like me 4 months ago, don't know what a double
> differential drive does, it's a mechanism that mechanically links 2 motors
> to an axle so that one motor rotates both wheels on the ends of the axle in
> the same direction and the other motor rotates them in opposite directions.
> In practice, this means that a vehicle fitted with this drive will go in a
> stright line if one of the motors is used or rotate in place if the other is
> activated. If both motors are activated, rotation still occurs.)
>
> So, a couple of things about my design. First, it's meant to be as small as
> possible. Second, the two input axles (yellow and green in the jpegs) rotate
> the output axle (blue) at different speeds - the green one uses a double
> bevel 20 tooth gear/24 gear crown combination for reduction, the yellow one
> a 8/24 tooth combination. I have not attached motors to this drive, but
> nothing seems to break or even creak when I rotate the axles with my fingers
> in any direction simultaneaously.
>
> Anybody can come up with a more compact design? Can anybody solve the dual
> speed issue? I could add studs in width (distance between wheels) and one
> stud in height to what already rises above the wheel axle (and maybe another
> stud below). Height is critical, but losing some length is even more so.
>
> OK, I hope you enjoy it and come up with some ideas.
>
> Chao for now!
Excellent color coding in your pics. Regrettably, I have no practical
advice. When I built the differential drive in Dave Baum's book, I was
dumbfounded by the principle. I look forward to to seeing what is clearly a
demanding project.
- Kyle
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In lugnet.technic, Miguel Agullo writes:
> Hi all,
>
> I've got an intriguing little MOC coming up that hopefully will interest
> both the technicheads and the robogeeks. It is a tracked vehicle with a
> twist, but you'll have to wait to learn all the details ;-) • snip
>
> In the meantime, here is something I could use some help on. For precise
> operation, I'm using a dual differential drive as described by the Ferrari
> brothers in their book. My setup is farily different from theirs, mostly
> because I need to save space. I've uploaded to brickshelf 2 dats and 4 POV
> jpegs of how it looks right now. You might want to take a look.
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?f=13856
>
> Anybody can come up with a more compact design?
Here's yet another shrunken dual differential design.
It uses worm gears to drive both differential housings as a space saving
measure. This also the adds the feature (?) of a bit more gear reduction.
There's a few pics of the design here :
http://www.visi.com/~dc/transmission
-- Doug
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Hey! That's a wonderful design! I wish I had done this!
ciao
stefano
> Here's yet another shrunken dual differential design.
> It uses worm gears to drive both differential housings as a space saving
> measure. This also the adds the feature (?) of a bit more gear reduction.
>
> There's a few pics of the design here :
>
> http://www.visi.com/~dc/transmission
>
>
> -- Doug
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"SteP" <stprosse@tin.it> writes:
> Hey! That's a wonderful design! I wish I had done this!
> ciao
> stefano
I had missed that. Luckily Stefano's post highlighted the thread again and I
found this wonderful device. Congratulation, Doug, very compact and nice
design indeed.
Ciao
Mario
>
>
> > Here's yet another shrunken dual differential design.
> > It uses worm gears to drive both differential housings as a space saving
> > measure. This also the adds the feature (?) of a bit more gear • reduction.
> >
> > There's a few pics of the design here :
> >
> > http://www.visi.com/~dc/transmission
> >
> >
> > -- Doug
>
>
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