7 replies to this topic

[Boeing747]

So, I'm fairly new to k'nex and I'm trying to make a launched coaster. I looked at the other post/threads and the tutorials were either unavailable or to advanced for a newbie such as me. Can anyone help?

Edited by Boeing747, 09 December 2017 - 12:40 AM.

[Rollerfreak987]

What type of launch are you looking to make? People have done drill launches, where a drill just spins a chain fast, like a horizontal lift hill, rubber bands, etc. 

 

It depends what you're trying to do, Also, feel free to post some pics of what you've got because that can help sometimes with advice too. 

[Boeing747]

I'm trying to make a launch like jesper's launch. I've seent the video but the tutorial was unavailable.

[X7123M3-256]

IIRC, Jesper's launch consists of a loop of chain pulled by a rubber band which is tied to one of the links. The rubber band is affixed at the far end of the launch, then looped round a pulley at the start of the launch, and then tied to the chain. If the chain is wound back, the rubber band is tensioned, and when it's released, the chain is will run rapidly forwards and launch a train. A gear with a ratchet can be attached to one of the chain links as a release mechanism - I've seen versions of this design that trigger automatically when a train arrives.

[Boeing747]

Ok thanks!

[Chaos]

I too, would like some launch-related guidance, but this time from st33lspectrum. Specifically how I might make an automated launch with surgical tubing, a lego nxt or eve, and possibly a drill. And where/ what brands should I purchase the materials from? Any suggestions help!

[~stεεlspectrum~]

I'll offer some launch help if you can give me some tips on making a mountain out of brown paper

Drill launches are by far the easiest. You're just building a horizontal chain lift and hooking it up to a drill instead of a K'Nex motor. They're nowhere near as powerful as cable launches, but they also don't take a week to build and adjust.


So for those venturing into cable launches... For surgical tubing, I don't think the brand matters too much. You just want latex tubing that's 1/4 inch outer diameter so it will fit in the KNex wheels. I recently bought 10ft of this one:
https://www.amazon.com/dp/B074NCLZSW/

I like to attach it by slipping the end over a green micro-to-regular rod. If you use a decent amount of super glue, it should never come apart.

 20180222_202531-01.jpeg   90.13KB   0 downloads

That should be the only extra material other than KNex you'll need. One suggestion I'll make is to use a wheel at the end of the launch and route the surgical tubing back underneath toward the beginning. This increases the length of surgical tubing that's stretched, giving the launch smoother acceleration. I've seen improvements by running out back and forth 3 times too. I can take a picture if that sounds confusing.

Now if you're making a chain launch, it's pretty self-explanatory how to arrange the gears, because it's the same as a lift hill. Now if you're making a cable launch, there's a couple of different ways to build the rail guides for the catch car. The ones on Tron, my current Volcano coaster, and Helmut, Jumpge, and Maarten's coasters are all slightly different, so I'd advise taking a look at those. The main thing here is to minimize friction between the rails and the moving parts of the launch.

When it comes to the reset mechanism, that's where you get into the mechanically complex parts. Not that it needs to be mechanically complex, but it's always a custom solution since everyone uses custom motors or drills. I wish KNex made a more powerful motor, because then we could design a reset mechanism that anyone could build and make a tutorial for it.

[Chaos]

Thanks! That's really helpful. Now I gotta start preparing for my next coaster . . .