I’ve blogged about this project already, and I’ve finally gotten around to making a proper webpage for it on my site. Although at this point, the webpage isn’t finished yet 
At any rate, I just wanted to announce it and get it out there:
http://www.texbrick.com/model_craneproj
TexLUG’s display at the Healthy Baby and Child Expo in Houston was a good success (see more info and pics here). Our modular tables (based on the MichLUG design) made their debut and worked quite well.
It was very nice to have a flat, level surface (roughly matching LEGO dimensions) to set our stuff on.
Finally… I have taken photos of my train work I’ve been messing around with two things. The first is an 8-wide bogie for freight cars.
I did a lot of test runs at the HBCE show, and the fatal flaw in the design is that the outsides of the bogie fall off. Their attachment to the inner frame is a little weak, and that’s something I’ll revise.
My other train work has been on a compact, powered bogie. This design will be useful to make a powered (using LEGO’s Power Functions parts) boxcar or perhaps a tender for a steam engine.
It’s problem is that the whole assembly torques to one side when running. This presents a problem when running through switches. I’ll work on debugging this design.
I’m making the switch to using PF trains and getting away from the old 9V system. One of my old 9V motors died recently, and it’s just the push I needed to move to PF. Aside from that, I’m really attracted to making PF trains because I get to design and build the drive systems. That’s Technic-related stuff and that’s what I enjoy.
And finally we have Project X.
More about that later
Ugh… sorry that it’s been over a month since my last post here. I have not touched my bricks lately because of a hectic, super-busy schedule (work, life, etc.). That’s just how it goes…
Plus I’ve got a load of stuff to break down and sort. I’m not looking forward to that so much
But hey, I built some trees for the train show last month. That’s something new here on the blog.
The big tree makes use of a bunch of different brown Technic connectors. These brown parts came mostly from all the old Starwars Technic sets I got years ago, and until now, I haven’t found a good use for them.
I also have a small back-log of ideas that I need to photograph and post here. Yep, I have plenty of house-keeping work to do!
On the side of serious building… I’m stuck in a rut. I cannot decide what to do. I’ve been wanting to build a new, very large crawler crane. I’ve built crawler cranes in the past, but I want to build the ultimate crawler crane MOC now that I have a lot of lessons learned and experience. The trouble is that everyone and their dog has built crawler cranes.
Sometimes I can’t get motiviated to build a MOC if there are too many similar ones out there by other builders!
The bridge made it through our train show (see photo gallery)! It held up great. I was quite surprised to find that no member or cross bracking loosened noticeably. Usually, on trusses like this, a piece of cross bracing will come loose at some point due to vibrations from the trains.
I packed up the model by breaking it into four sections, and then piggybacked two section pairs together.
TexLUG’s layout consisted of three 8-foot long tables on either end of the bridge. One of our members (Matt S.) brought two 2.5-foot small truss bridges, and we used those on one side of the layout.
Super Chief crossing (click for larger)
The bridge did endure some heavy loads. At one point, we had two very long trains on the main loop, and they managed to end up on the bridge at the same time. Both trains were longer than the bridge
Their were a few accidental human contacts, but it survived. The worse was when my 4-year old son was underneath and suddenly popped up. He buckled a section of deck with his head. I managed to press it all back together quickly before the train came back around
Over the past two weeks, I’ve been working on a new bridge. This will be for TexLUG’s display in an upcoming model train show.
The design length of the bridge, measured from center-to-center of the end supports, is 10.46 ft (3.19 m). The actual clear span will be just 1/2 inch, or so, less than this distance. The actual length, in reality, will be just slightly less or more, depending on how the structure settles.
click larger view
I designed the bridge by determining the sizes of all the main members and also the deck and hanger pieces. I modifed my old truss spreadsheet for this design: www.texbrick.com/model_10ftbridge/bridge_10ft.xls
deck members (click for larger)
I changed a few things about the construction of this bridge as compared to how I normally build trusses. I’ll describe all the fine details later on when I make a formal webpage for this bridge.
I had to correct a few things after I had mostly built the whole bridge. I wished I had realized some of these things from the start:
1. It wasn’t wide enough. The original design would have accomodated 8-wide trains just barely. However, I realized later that we’ll have 12-wide trains (i.e. “natural” 10-wides with extras hanging off the sides; e.g. Tony Sava’s monster Allegheny). I spent a lot of extra time making the portal frames wider.
2. Height. The end portals of the bridge were lower in height in the original design. I had to change up the design (by lengthening some members) to create extra height so that trains passing through would have adequte clearance.
3. Strength. After I had the original structure built, I noticed that the main chords deflected a lot when I loaded the bridge. I experienced the same trouble with the 17-foot bridge I built 4 years ago. So, I doubled-up most of the main truss chords on this new bridge. When Tony’s Allegheny rolls accross it, I want the bridge to stay intact!
Anyway, the bridge is nearly complete, and I hope it will hold up this weekend at the show.
Here’s a small turntable design using a thrust roller bearing. It’s still a work in progress, but I think I’ve sorted out the main geometry.
Not shown is the matching ring. When assembled, it kinda creaks a little bit. I’ll have to fine-tune things to make it roll smoother. But I think this one will turn out well. I’d like to make a different design for the rollers - I’d like more of them and with smaller diameter wheels.
This design uses the “solid core” concept that I’ve used on some of my other turntable designs. This concept proved to be too flexible for a large turntable, but I’m hoping that it works for a smaller one like this.
I’ll post a part 2 later on when I finalize this design.
I’ve just finished a new medium-sized turntable design that looks like it will work well. This turntable will be used in my new tower crane (see the triangular cross-section truss entry below - these developments are all for the tower crane). I need to take some photos of this new turntable, but I’ll post it here in the coming weeks.
One of my next projects is to build a simple tower crane. I’ve developed a new turntable (more on that later ), and I’m working on a boom with a triangular cross section.
It’s not too hard to make a triangular cross section, but it’s an added challenge to create a design that will transition between sections of different heights.
This design (below) makes use of a truss chord on the top that is oriented normally. This allows the height of the truss section to change along its length fairly easily (it’s the link between sections that becomes very difficult unless the top chord is oriented normally).
click for larger
My goal is to build the boom of the tower crane as a cantilever type and not use guy wires as typically seen on many tower cranes. The tower base of the crane will make use of the boom sections I built for the crane project.
This post continues the Ideas section here on my blog. I want to point out that one of the main reasons I created this blog is to help me communicate these ideas and works-in-progress.
I’ve decided that I want to present my ideas (even the ones that don’t work out) and the stuff I’m currently developing. It takes a long time for me to finish a MOC and then present it on my website. While I’m building a typical MOC, I’ll go through many design iterations and mess around with many different ideas.
So, I’ll show them here. Maybe they’ll inspire some readers. Maybe some readers will help me out by leaving constructive comments. Anyway, here’s the next installment of my Ideas section:
Small Turntable 1
The classic Technic turntable is a fantastic part. It’s one of my favorite LEGO elements.
However, it has its cons, especially when you attempt to build a large and heavy model with it. Specifically, there is a lot of friction generated within the turntable and it also pops apart when loaded by an overturning moment (think about a crane lifting a heavy load).
A better turntable design will use two things: 1) a thrust roller bearing, and 2) some means of “capturing” the top and bottom components so that they don’t separate under load.
The turntables I’ve built so far have been rather large, just because it takes a lot of space to incorporate the above two ideas into a functional assembly.
I’ve been wanting to build a turntable that is similar in size to the classic Technic turntable. Below is one, quick idea that incorporates rollers to provide a low friction bearing and a method of “capturing” the assembly so that it doesn’t pull apart under a high overturning moment.
The double-stacked 40-toothed gears are captured by 8 rollers. The flat edge of the gears (on their sides) ride against the rollers.
The “core” of the assembly is squeezed together with multiple threaded axles. The Technic threaded axle is a rare part and is no longer produced by LEGO. Note that this concept of a “core” made using threaded axles was used on my 4×4 telescopic crane. You can see that core design in this photo.
This assembly is not finished and is not functional. It’s basically just developed to a point where the major parts and geometry have been worked out.
What’s left to do is make a base that the “core” will attach to. It also needs a stronger centralizing support (the red 2×8 Technic plate) so it will rotate about a fixed center and also handle lateral loads applied to the turntable assembly.
I’m not sure how this assembly will function. My gut feel is that the method of “capturing” the 40-toothed gears with rollers is a little flakey. They might slip off. They might grind too much under load and not rotate smoothly.
I’ve stopped development of this idea in favor of a new one (a different design for a compact turntable). I’ll present that one later.
For the first phase of my recent crane project, I designed a new turntable. The concept of this turntable is based on having a thrust roller bearing and also having the whole assembly centered about a solid core.
I first developed a 12-segment ring for the round bearing.
This ring is based on “perfect” spacing, i.e. every other segment pins into normally-spaced holes. This basically means that the “round” ring is affixed firmly to a square frame and can be easily integrated with the framework of the crane.
The next step was to create a set of rollers. The ring of rollers shown below is actually a new concept, one that I didn’t actually use in Phase 1. This new one is the same roller ring as the original, except that the holders for the rollers are on the outside of the ring instead of the inside.
My new idea for this turntable was to have the whole thing centered about a solid core made of stacked Technic turntables. The core would extend upwards through the superstructure and contain a “cap” with counter-rollers to keep the whole assembly pinned together.
One of the primary loads on the turntable is weight (vertical, downward load), but it also has to resist an overturning moment. For example, when a crane picks up a load, the whole thing wants to tip over. Therefore the turntable has to hold the superstructure down against the base, so to speak.
The photos above were taken after I broke the crane apart into its main components. Here is a photo of the crane when it was assembled:
Here is a diagram showing the cross section of the turntable. Note the different sections and bearings (rollers).
One component I haven’t shown in the photos is the assembly that actually centralizes against the Technic turntables in the core. It is a fairly straightforward design that uses two sets of four 24-toothed pinion gears (spaced at 12, 3, 6, and 9 o’clock). Two of these gears are powered so that the turntable can be rotated by a motor.
Phase 1 of this project proved that this turntable functioned well but couldn’t handle much load. The rest of the crane was robust, much like my marine pedestal crane.
When lifting, the overturning moment on the turntable pried it apart greatly. I pushed it until I felt uncomfortable, but I didn’t break anything. The solid core in the middle is just not strong or stiff enough to keep the superstructure flat against the base. The other downside was that it kept throwing rollers. The 2×2 round bricks would frequently pop off due to the flexing of the whole assembly.
So, in Phase 2 of this crane project, I’m going to try to redesign it.
About a year ago, I got the itch to build another large crane. I started a model and finished it in about two months. The final MOC (my own creation) isn’t really a finalized piece, but rather a project to test various ideas.
What really inspired me to build this were several ideas I had for a large crane, and this project turned out to be more of a testing phase than a real, finished MOC.
Specifically, I had some ideas about a new turntable design and also further development of using large plates to make beams for the framework (including joining them at an angle other than 90 degrees). I also spent the time to develop a compact winch package that could be reused on future projects.
I call this “Phase 1″ because I’m going to contunue to work on it. I created a 4-legged pedestal base for this crane to test out my ideas of joining built-up beams (made from large plates) at different angles. In “Phase 2″, I’m going to explore other ideas I have for a base - a moveable base
In the next phase, I’m also going to redesign the turntable. The original design worked okay, but had its flaws. The most serious flaw is that it lacked the strength I wanted. The crane would just barely support 20 pounds on the main hook, and I I’d like to see 50 pounds supported or more.
I have other projects in the way right now, so it will be a while before I continue on with this crane. But first I need to take close-up photos of the components of “Phase 1″ so that I can present the ideas here.
More to come soon…
