Anyone for a Knob Wheel?
Despite these wheels being in the education kit, the retail kit and the education resource set, I don't see them used in many models. That could be because I don't get out much, or it could be that their slipperiness makes them less suitable than conventional gears. (I used them in pairs while building Alpha Rex, but the knobs kept disengaging from each other).
Knob wheels provide more surface contact than a regular gear, hence more torque (theoretically). But I haven't seen many around.
Can anyone point us to models on the web or in NXTlog that use these wheels? They look too good to just lie in the box.
Comments
I'm looking at the book cover's gripper at 400% magnification, and I don't see the knob wheels. Perhaps they're obscured by other parts?
Rick
You can see one of them on the front cover. Look at the swinging arm. There are actually two there that convert the gear direction by 90 degrees.
I'd be interested in knowing why the designer chose those gears as well.
My guess is that they provide better torque esp. at higher speeds.
I still don't see it, but I'll take your word for it. (I'm looking at the first draft of the cover. Maybe something is cropped or I'm looking in the wrong place).
I do see the one on the Lego Ed base vehicle. I never noticed it before.
Rick
I must admit the current cover picture, does not show them.
But they are used.
so maybe you just will have to wait a little longer until the book is available.
Martyn
http://www.youtube.com/watch?v=K6u7pn62Zz0
Thanks!
Rick
To shift gears, I needed to
shift the angle of rotation by
90 degrees, and bevel and crown
gears just kept slipping. They
were not able to transfer enough
torque. The knob gears do a
great job here without slipping.
In a normal configuration
(no 90 degree turn), I don't
think you need them. The normal
gears don't slip much. But
the bevel and crown gears do,
and that's were you need the
knob gears (that's what they
are called).
Ah, yes....I plainly see the knob wheels in the undercarriage of your roadster. A beautiful model, too, by the way.
Rick
An amazing transmission and a GREAT video.
Where can I get those yellow knob wheels featured in your model? ("Knob wheels" is common parlance in our part of the world, even though the wheels function as gears).
Rick
I read your post more carefully and now see where you got the yellow knob wheels: 8421, the Mobile Crane.
Rick
http://www.bricklink.com/catalogItemIn.asp?P=32072&in=S
I was aware that the knob wheel was included in many manufactured models. I just hadn't seen it in many homemade models.
Obviously, lots of people have found creative uses for this wheel. And I considered it an "orphaned" part. :)
Rick
--
Brian Davis
Sorry I didn't see your question ealier. Yes, they are from the mobile crane.
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=145292
take a look at the in progress folder!
I'm definitely a believer in knob wheels, even with a perfect frame the 12z bevel gears' teeth will bend and click, especially under power from the NXT motors.
Impressive photos!
The two pairs of knob wheels add a large amount of torque, I assume.
Rick
http://www.brickshelf.com/gallery/masterprogram/DifferentialXL/diff_xl_center.bmp