[GBC] Kicker Module

[Captainowie]

Hi guys.

I have begun construction of my newest GBC module, and I've decided to try sharing my journey with you.

I am aiming to make a projectile launcher, that will get the balls across the gap between two tables, a distance of about one meter. I have considered two approaches: contra-rotating wheels as in a bowling machine; or impact from a moving lever, like someone taking a golf shot. After an afternoon playing around with contra-rotating wheels, I decided that the moving lever had more chance of success.

As most of my structural elements are currently tied up in display models and other GBC modules, I decided to use the one set I have that isn't either built or assimilated into my collection - a 8110 Unimog (no longer MISB because I had already raided it for the pneumatic pump). As a result, I would like to see if I can make this from only the parts in this set - because this wasn't going to be hard enough already!

Here's a very quick rendition of what I've got so far:

The part on the end of the arm is the rubber 2-length liftarm, because I thought it would make for a gentler impact on the balls. I plan to raise the balls vertically into the path of the arm just like they do at some driving ranges.

In order to get a rate of ~one ball/sec I'm probably going to have to build two or maybe even four of these things side by side.

I do have a couple of questions I'd like to ask the forum:

• When using shocks like this, should I stop the movement of the arm before the shock expands fully? Or will the shock handle the sudden stop by itself?
  
• Has anyone built a reliable projectile module that shoots over such a large distance? I don't remember seeing one online anywhere, though I've seen plenty that cover smaller distances. I fear that at this range precision is going to become an issue.
  
• How should I prime the arm? I need to allow for quick release, and automatic re-arming.
  
• Is there any other mechanism I should consider? Like perhaps a centrifugal gun?
  

I'll keep you all updated on how I progress.

Owen.

[DrJB]

Check out Akiyuki's basket ball shooter. He's got a video on the internals and how the shock mechanism is actuated. He does use 'thin' 3x3 lift arms as cams.

[Captainowie]

I've seen that one, but the distance involved is much smaller - I'm not sure the same technique can scale to propel a ball a meter.

[torso]

When using shocks like this, should I stop the movement of the arm before the shock expands fully? Or will the shock handle the sudden stop by itself?

Lego probably designed the element to withstand such usage. It's still good to stop it as early as possible, as you'll need less energy to rearm it.

Has anyone built a reliable projectile module that shoots over such a large distance? I don't remember seeing one online anywhere, though I've seen plenty that cover smaller distances. I fear that at this range precision is going to become an issue.

You just need a bigger target.

How should I prime the arm? I need to allow for quick release, and automatic re-arming.

The balls are light, so give the solution mentioned above a try. If you have a strong spring, one meter doesn't sound very far. If you do end up a little short, you can place the target lower than the launcher. Don't complicate things until you really need to.

I'd recommend paying more attention to the hammer design and how it's connected. The less elastic it is, the more energy it will consume. The more energy you lose, the more energy you need to put in and that will just increase your troubles. Also try without the rubber.

[Eigenbroetler]

i have made one with counter rotating wheels, it shoots about 3 feet and it needs a 5 inch wide target to be sure no balls get lost, my wheels are in a vertical position and spins with about 700rpm.

[Nalyd997]

You should make a cam out of bricks that resembles pacman and position it under the firing arm with something fixed to the arm that goes around the cam. Anyway should this be a topic for the gbc at the brickvention where we can get help and maybe set up a floor plan before we even get there? Hope that helps

[LegoGBC]

Altough I would use wheel based launcher at this case (the large distance), here's some

Wheel launchers are all about finding the right gap between the wheel and the ball, so having multiple types of wheels to test with should help in case you decide to go that way

[Captainowie]

Well, I decided to take a closer look at Akiyuki's mechanism, and decided to have a go at scaling it up.

I've hacked together a temporary power source, and this fella can launch the balls approximately a meter and a half, with quite good precision. I think I'll put two of them side-by-side, running 180 degrees out of phase with each other.

Biggest problem is that now I can't really use the name "kicker"!

Now I need to work on how I'm going to feed the balls to the launcher cup (best use for portal axle frame that's not in a portal axle?) one at a time at the right point in the cycle. I have some ideas for this, it remains to be seen whether those ideas will actually work!

Owen.

[Captainowie]

Turns out they do work! Well, kind of. I would have preferred to keep the ball in the trap and let it go on the trigger, rather than keep the ball out of the trap and let it in on the trigger. But I couldn't get that to work.

Sorry about the ugly colour scheme.

Things still to do:

• Rebuild it from Unimog-only parts (if possible)
  
• Build a second copy of the mechanism
  
• Work out a drivetrain that rotates the power axle at 30 rpm (or as close to it as I can)
  
• Build something to split a stream of balls between each launcher mechanism
  
• Build something to get the balls high enough from the input bin (might have to look outside the Unimog for this
  
• Build the catcher module
  

Fun times!

[Nalyd997]

Turns out they do work! Well, kind of. I would have preferred to keep the ball in the trap and let it go on the trigger, rather than keep the ball out of the trap and let it in on the trigger. But I couldn't get that to work.

Sorry about the ugly colour scheme.

Things still to do:

• Rebuild it from Unimog-only parts (if possible)
  
• Build a second copy of the mechanism
  
• Work out a drivetrain that rotates the power axle at 30 rpm (or as close to it as I can)
  
• Build something to split a stream of balls between each launcher mechanism
  
• Build something to get the balls high enough from the input bin (might have to look outside the Unimog for this
  
• Build the catcher module
  

Fun times!

Looks good! Will this be at the Brickvention? And why only unimog parts?

Edited October 19, 2014 by Nalyd997

[Captainowie]

Looks good! Will this be at the Brickvention?

I certainly hope so! I've still got a couple of months to get it right!

And why only unimog parts?

That's in the opening post.

[Captainowie]

Sorry everyone for the lack of updates - I've been distracted by other (both LEGO and non-LEGO) things.

I now have a pair of nice ball launchers in a red, grey and black (with a hint of yellow and blue) colour scheme, and I've got a drivetrain that delivers 30 rpm to the flicker arm cams (giving the requisite 1 ball per second between the two launchers). What I'm trying to do now is design the middle bits of the module (the drivetrain, and a couple of visual-effects mechanisms) so that I can join the two halves together in such a way that:

1. It's actually possible to assemble it in a nice order
   
2. It's sturdy in all three dimensions
   
3. It can be broken down into relatively dense chunks for transport
   
4. It can actually be disassembled at all
   

Photos and hopefully video to come when these simple requirements are met.

Owen.

[Captainowie]

So I've made some progress lately. I've got a rough video up here.

Let me know what you think!

Owen.

Edited December 20, 2014 by Captainowie

[Captainowie]

This afternoon I ran a test with this module fed by its feeder module rather than my fingers. The spill rate was about 1 ball in 4 :-(

But after some minor adjustments I got that down to about 1 ball in 10. The vast majority of this spill is due to misfire (rather than a ball popping out of its track), which happens when the ball doesn't sit in the holder properly before being launched - it stays in the lip around the edge. I will try to jam some putty or something in the gap to prevent this.

Owen.

[Myxo]

Have you thought to try the 92911 Power Joint for the cup

[Captainowie]

Have you thought to try the 92911 Power Joint for the cup

Hi Myxo.

Yes I have given it some thought. But the outer part is a bit big - the ball rattles around for a second before settling down - so that is likely to impact accuracy. The inner part has a nice cup, but will require a complete redesign of the top part to fit it on the throwing arm. If I can't get something working with the portal axle then I'll look into it further.

Thanks for the suggestion.

Owen.

[technicaddict430]

This module looks fascinating so far! Any chance of getting some building instructions when it is finished?

Edited December 22, 2014 by technicaddict430

[Captainowie]

I've been able to improve the misfire rate down to a couple of percent, by strategically placing a piece of wire (actually, a twist-tie) such that the balls aren't able to rest in the lip around the edge of the portal hub. I'm now happy enough to say that this module is essentially finished. There are a couple of minor aesthetic changes to make, and I'll do those when I break it down into pieces for transport.

One question I was kind of expecting to be asked was "this is built from Unimog parts - where's the orange?"

Well, I thought it would be a little bit cool if as well as being a GBC module, it still looked like a Unimog. So I kept all the bits for the cabin separate when building the catapaults, and made a frame to support it and the engine. I also added space for the wheels, so this is what the completed module looks like.

It's a bit hollow in the middle, and the wheelbase is just a bit too long for my liking, but I'm really happy with how it's turned out.

Of course, the wheels and engine are powered!

I realise that the input chute is way too high for a standard GBC module. I have designed a feeder module that delivers the balls to the right place.

Now I just need to make the catcher module - using the parts from the tray.

(yes, I'm posting to a web forum on Christmas day. No, I'm not spending time with my family - they're four thousand km away)

[technicaddict430]

Looks great so far, but will you make building instructions when you finish? I would really like to build this.

[Captainowie]

Sure - here are the instructions:

Step 1) Study all published photos and videos

Step 2) Figure out how the mechanisms must work

Step 3) Recreate the mechanisms

Step 4) Recreate the aesthetics

As an added bonus, these instructions work for pretty much any of the wonderful creations you see on this forum (or any other, for that matter)!

If there's anything specific that you need help with in that, I can probably help, but I'm not going to make put-this-pin-into-that-slot instructions.

Owen.

[Technic Jim]

Sure - here are the instructions:

Step 1) Study all published photos and videos

Step 2) Figure out how the mechanisms must work

Step 3) Recreate the mechanisms

Step 4) Recreate the aesthetics

As an added bonus, these instructions work for pretty much any of the wonderful creations you see on this forum (or any other, for that matter)!

Very good universal instructions! Jokes aside though this model is lovely and a very good idea/design. Thank you for sharing this.

[Captainowie]

So I finally got a chance to use this in an actual GBC circuit (the event I had designed it for forbade it on safety grounds). It worked pretty well with an accuracy of approximately 98%, and was a bit hit with the crowd. However, I'm going to disassemble it for a few reasons: I need the parts for other modules; it's just a fraction slow and would occasionally back up with balls; and it puts too much stress on the shocks!