Category: Knex

One of the things I remember from being a kid was that having large assemblies rotate was a big pain. Either making a “circle” of weirdly spaced rails for using wheels as bearings, or having a sloppy/ugly/fragile rod connection. So, now that I have a credit card, I made sure to get a bunch of gears, including a large crown gear.

For the turret itself, I was more worried about getting it to look like a turret than making it look exactly like the real one. The angles and sizes are too precise for accurate replication with K’nex, so I am worrying less about the shape than functionality.

I decided that I’d build the mounts and basket at 45° from the hull. This allowed me to use a blue rods on the hull and use yellow rods in a 2-blue-wide hull opening for it to rotate within. On the base of the hull, the turret support ring is a set of 4 gears at 45° to the hull. They are fixed on white axles with opposite rod-clips, and the rotated square is built up with the halfway points of each side green-rod clipped to the hull.

The entire turret and basket are placed on top of a large crown gear, with a blue rod through both axle slots clipped above. This lets the whole thing drop down with a short amount of the center rod interfacing with the bottom of the hull, giving me two planes with support around the axis of rotation. It also gives me the option to put more wires or force-transmitting rods into the turret to allow manipulation from within the hull and have enough room to not chop them up.

 

 

The tracks are proving to be more of an issue than I’d anticipated. I’ve seen a lot of K’nex crawlers in the past with a variety of tracks, and all seemed to work fine. Now that I’m trying to do the Panther tracks, I’m running into issues. Ideally, I’d like to have the track three wheels wide plus two indexing spacers, so that it looks like the real track as much as possible.

You can see that the basic layout seems simple, but there’s a slight problem. The wheels I am using slide easily between connectors in a 3-connector-wide groove. But a blue rod only supports 6 total connectors edge-on. I made a track with 2 connectors in the center, but this would only support a single wheel on either side of the guide. I don’t think this would be stable, and also isn’t keeping with my desire to keep it close to the real function. It does work though, so if none of the other options are doable I might just keep it as a placeholder.

This means if I want a 3-connector wide center wheel, I have a few choices:

1. Have the wheels hang off the edge of the track. This is not acceptable for a number of reasons.
2. Have the track links staggered along the length of the track. This would probably work, and might make the sprocket connection a little easier (more on that later). It’s also closest to scale.
3. Use yellow rods. This makes everything easier, in that it holds exactly 11 connectors, which means 3×3 wheel slots with 2 guides in between. This makes the track huge, and means I either need to be OK with going off scale, redo the scale of the hull and turret, or switch gears to make this a Tiger.

A few pics of the designs I’m playing with are below.

I also need to sort out the sprocket drive. If I can, I’d really prefer to have the sprocket be an actual gearing system that engages the outer track pins. This is how the real one works, and would be nice if I can do it. Problem is, taking an 8-way connector and putting green rods in all slots won’t fit any of these designs. Same if I use white rods and use wheels to adjust the engagement height. This is going to need a lot more thought and design to get right.

When it comes to features that make a good tank, the tracks and drive system are critical. Everything being equal, a tank is a maneuver weapon for modern cavalry tactics, so I wanted to give the subject its due diligence. When I started this I had no idea how this whole system worked, so I did some reading on basic mechanics and attributes of various tank suspension systems.

I’m using the largest tires for the road wheels, since I have a bunch of those, and it looks good for this size. For the Schachtellaufwerk road wheels, I interweaved single wheels for the test design. I haven’t added the overlapped outer wheels yet , but have the measurements for doing so.

For the idlers, I’m trying out two simple designs, but I think I need to rework this part so that it can actually adjust track tension. A pair of widely spaced motorcycle wheels seem like they’ll be the right size.

For the sprocket, I tried a few designs using gears (as seen on the Tiger) or various sized wheels/tires. I built a 16-tooth helical gear out of a series of interconnected offset 8-way white connector/rod combos on an axle, which works OK. But I’m not doing much else here until I get the tracks sorted out.

For the tracks themselves, I’ve tried doing a K’nex connector/rod track, different wheel/rubber band combos, and a few chain-based designs. I’ve temporarily settled on “borrowing” some Magic Tracks and using the flexible roadway as an ersatz method of traction. The inner surface of the racetrack is smooth, so using a drive wheel or sprocket doesn’t work yet. But as the tank is rolled on the floor, it (sort of) works.

The first sub-assembly to tackle was the suspension. I wanted to build it as a separate chassis to which the hull would be affixed. This might mean a slightly smaller crew compartment, but much easier ability to make changes to the design. I also thought this would be better than a complex and fragile through-hull axle mounting and complex indexing joints.

The real Panther and Tiger tanks use a torsion bar suspension, where a long rod is twisted by a wheel on a lever instead of using coil/leaf/volute springs. I figured I’d try to mimic that, using regular rods to start and test the design. I could later use the flexible ones to fine-tune the tortional resistance.

I laid out a simple pair of center beam supports to attach the torsion bars. They are a series of 9 yellow connectors with white rods, connected via several blue rod cross braces. I used gray rods for each torsion bar, with road wheels on yellow rods connected by doubled orange connectors. This will give me reasonable torsional stability, and I can adjust the stiffness in several places.

Since this has gone from daddy-and-son to full blown adult playing with toys, I wanted to build this as well as I could. This means that I’m going to try to get it to look and act as much like the real thing as possible, and only diverge when limited by materials or simply not being fun.

The Tiger Cal and I had built together was closer to 1/20 scale and only superficially looked like the real tank. It was also wobbly and fragile, which I wanted to address with the new build. I also wanted to make it somewhat modular, so I could easily adjust the design and have Cal playing with smaller subassemblies.

I also have the dual-motor with wired controller, so while I am doing the initial build unpowered I am making sure to leave room and design elements to make adding power easier. I’m putting in all the gearing for eventual power, with simple clips or friction providing resistance in things like the gun laying.

This brings us to the point where I, a 35 year old father of 2, am building a ~1/12 scale Panther tank out of K’nex.

Last week, Cal asked to build “A TANK”. I asked if he wanted to make a Tiger or Sherman M4E8, but he didn’t really have the background in WWII armored vehicles to make the call.

I called in my friend, a WWII reenactor and fellow jaded imperial stormtrooper veteran. He gave us the waffenamt of the Wehrmacht.

We spent about a day making it, and it’s a regognizable piece of Krupp polyoxymethylene. I posted a photo, and figured we’d scrap it and make something else soon after.

I’ve been having rough sleep for the past week, less than an hour a night no matter what I try. While I’ve been up, I started a new project. A few print-outs of tanks, and I’m putting together a rough hull design for a bigger vehicle. I’ll post up more about the design and building later, it’s still very much a work in progress.

I am trying to be faithful to the real tank when it’s fun or interesting. It has a torsion bar suspension, overlapped road wheels, a turret basket with stabilized gearing, an elevation-limited adjustable main gun, and a lot of dark-colored pieces to intimidate the Reds. But it also has fabulous rainbow tracks, courtesy of Magic Tracks.

For the past few weeks I’ve been nerding out with K’nex. My 3 year old son is an engineer, he doesn’t quite have the dexterity for Legos. I bought a set of K’Nex, remembering how much I liked them as a kid and how relatively simple and durable they were.

At first, it was mostly me putting it together and having him pick the pieces. Soon, he started clipping the rods side-on, then started connecting more pieces, and made a two-wheeled “remote control robot” that was pretty cool.

We “do projects” together all the time, from tow trucks to motorcycles to race cars to trains to a bug robot. Naturally, I take point in most of the work, but we make a good team when we’re in the zone.

I’ve got PTSD, and while I feel good most days, I’ve been having a lot of anxiety lately. We have zero room for me to do any of my normal mindfulness activities (range time and hand-loading ammo). I’ve been having fun playing with my kid, and that has helped with mindfulness and staying connected.

He asked for some gears and wheels, and I figured I’d buy some used stuff to save money and get cool parts. We moved recently, and live in tight quarters with inlaws. But we really don’t have any room for more toys, even with most of our stuff in storage.

I checked Craigslist and bought a box from a local person, and a box of bulk K’nex on eBay. I spent about $55 between the two, and figured we could get the parts we need and give away what we didn’t want. I cleared out a small toolbox to hold the expanded collection. The local box was a few hundred pieces, and we kept everything from it.

When I received the bulk package, I was surprised to find a monster box literally filled with K’nex. Like 30 pounds of them. We dumped them out after dinner to pick what we wanted, and the pile filled the area under his queen loft bed an inch thick. He started tearing through the pile, and picked up a brick axle and says “holy crap dad, this is nice”.

Quickly it was resolved that (a) we were absolutely keeping this whole pile and (b) we had to sort it out if we ever wanted to use it. We packed them into tupperware and started making stuff. We’ve spent a bunch of time playing, and I started making some stuff on my own to show him new things or just to relax and have a bit of fun.