Subject:
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Road grader ready for BrickFest
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 21 Aug 2006 16:54:58 GMT
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Highlighted:
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(details)
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12976 times
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After about 3 blade designs and several overhauls, my grader design is complete.
It was the hardest pneumatic design I have ever done because the amound to space
for pneumatic lines and hoses was limited. There was also a few mechanical,
structural, and flexibility issues to be addressed.
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=148840
The blade had to be able to have 3 axes of freedom- which is commonly done with
a ball-and-socket joint. Since Lego does not make any joints like that that can
be pulled on with great force, I decided to make a 3-axes joint in front of the
blade to take this force. It looks like it would pull out at the bottom, but it
doesn't. I recently realized after looking closely at real graders that the
blade assembly needs to be able to swing sideways. Up till that point I had the
blade fixed so it could only move up straight. I also wanted to be able to steer
from the cab with hand-of-god steering on the outside.
The tilt steering was even harder to address because I had to fit pneumatic
hoses inside the front suspension and figure out a way to route the system
around the wheels so that they never brush up against the hoses. In reality, the
steering system has a lot of friction and like any real life steering system- it
works best when the vehicle/machine is already moving.
6 pneumatic switches were used and they seemed to look best in the cabin.
Although they are not in the same places the switches are in real grader cabs, a
5" tall human could still operate everything from the cab if he could get around
them. Anybody know any 5" tall humans?
The rear tilting suspension is not the prettiest to look at but it works
reasonably well. The wheels naturally want to pull outward when it makes turns
but the old studded steering piece is there to hold the verticle suspension arms
together. There was a lot of friction in the drivetrain so a white cluth gear
had to be placed high in the drivetrain which is good if that long 12 stud-long
crankshaft sags in the middle and becomes hard to turn.
I had very few yellow technic parts so the black stripe down the side is to
minimize yellow parts. It is not meant to look like any specific make of grader
but it is about how I would make one look if I worked for Caterpillar.
The blade does not turn 45 degrees, but the side-swing in the assembly allows it
to turn about maybe 35 degrees.
Overall the design is 26" (66cm) long. A few more small adjustments may need to
be made, but it is so done that there is no reason to wait any longer to call it
done.
One might notice the "gap" in the bottom of the blade. I could not find any of
those 1.5-stud wide track pieces that was 2-studs long, so I had to put an old
Lego Town hinge there to fill the gap.
The bent yellow beams on the outside of the chassis behind the blade are there
to keep the chassis from breaking apart in front of the cab.
Last but not least, the ripper does not have very long shanks but works well
enough. It does not plunge all the way down to the shank frame, but I wanted it
to elevate high enough for good grould clearance in the rear (which must not be
too critical for graders since even a raised blade does not give very good
ground clearance in the middle). Real blades might raise 18" (46 cm) off the
ground according to the Caterpillar website.
A thank you goes out to Alvin Brant (an another builder who's name I forgot) who
explained the reason for grader wheels to tilt in detail.
I am glad it is done and since I wanted it done before BrickFest I actually had
to pray to God for help at one point. But He helped me think clearly in the
nick of time!
Enjoy the pics and don't hesitate at all to give comments or criticism as
feedback.
Nathan Bell
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Message has 1 Reply:
 | | Re: Road grader ready for BrickFest
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| (...) absolutly awsume there Nathan! right on.. i've operated a CAT14G motor grader and the detail that you have ,+ mechanics is perfect. you said that the rear wheels are not totally flat?.. send me a photo of what you mean, i would be happy to (...) (18 years ago, 21-Aug-06, to lugnet.technic)
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