Laminar Nozzle Cutter Test 2

11 04 2009

The cutter is working much better since I added the baffle.  The baffle is working almost perfectly except for that pesky leak.  I’m pretty sure that leak is comming from the brass nozzle/plexiglass interface. I suppose that I will just add some more expoxy and hope that it works this time.

Here are a couple of my thoughts regarding the cutter.

1. Fix the electronic switching so that it flips the electricity from one solenoid to the other immediately.

2. Fix the drip.

3. Fix the drain for the water.  I think it is probably the biggest of the three right now in order to make the cutter work properly.


Laminar Nozzle Speed Cutting Test

11 04 2009

A friend of mine posted a video of his cutter just cutting so that we could gauge the speed of his cutting.  I’ve decided to do the same.  If you have done this let me know how your’s compares.  If you have any concerns or possible design improvements let me know.  I’ve been told that this is the trickest part of the whole laminar fountain, and it is pretty tricky to get it to work the way I dream it.

Laminar Nozzle Cutter Mechanism Test 1

8 04 2009

I got a prototype working last night for the cutter mechanism!  It works….mostly.  There are some bugs in that I have to work out, but all in all a strong showing.

It may be difficult to see, but when it is un-cut there are more blurbs (I don’t know what to call it!  If you have a good name submit it please!) than there should be.  I’m thinking it is probably from the water splashing on the upper plate and then dripping down onto the nozzle and then getting sucked up by the stream casuing the annomally (there’s a good word for it).  That’s my guess.  Any suggestions as to what it is would be greatly appreciated.

Laminar Nozzle 8″ Prototype Test 1

3 04 2009

Let me know what you think!!!!  Have any suggestions?  Have you built one of these before?  Are you going to build one?  Please leave a comment.

Trebuchet – The First Fling

19 11 2008

We had our first test of the trebuchet with the full 600+ lbs of concrete, and well it a huge… Well just see for yourself!  This was the very first toss!


Photo sequence provided by Irotras! Thanks for the awesome shots!

I don’t know how far it went exactly because we were so busy tossing the next pumpkin, but by my estimates the really heavy pumpkins (about 15+ lbs) were going about 100 ft. and the small pumpkins (about 6-8 lbs) were going about 200 ft.  That’s good, but it can be better!  One thing that was clearly evident in watching the trebuchet is that there is too much friction in the throwing arm and main axle joint.

I have some video that was taken with a real video camera, and once clean it up I will post that.

I would like to thank every one that helped me out on this project, specially my wife for being understanding and listening to the days and day of technobabel.

Trebuchet – Firing Pin Mechanism

12 11 2008

img_0080I finished building the firing Pin Mechanism for the trebuchet.  It’s pretty simple.  There are three eyelet hooks; one on the throwing arm, and two attached to the frame.  I had to cut a slot into the trough so that the eyelets could be very close together. The photo below shows what it will look like underneath the trough.

I purchased a large 8″ nail that will act as the firing pin.  I’ll get a photo of that up here soon.


Trebuchet – Throwing Arm

11 11 2008

So in explaining on how to size the primary axle, I realized something.  The same force that the primary axle experiences will also be experienced by the secondary axle!  This is bad, considering that I was planning on using something a lot smaller on the secondary axle.

However, this is not a complete disaster!  We had a couple of different options.

  • Resize the axle
  • make the axle strong (I don’t know how exactly)
  • or distribute the forces closer to the edges

So that’s what we did!  Instead of having the two 2×8’s right next to each other we decided that we would put a 2×4 in between the board in order to space out the forces that the 2×8’s are putting on the secondary axle.



The forces are acting on the basket, throught the axle to the throwing arm.  The closer we bring the 2×8’s to the basket arms the less of a moment arm there is, which means less bending.  Just think for a minute.  We’ve all seen those large cat machines and all of those joints are made in a similar fashion to how we are making the basket joint.  If we look at the figure below the pin there is a tremenous amount of forces on that pin, but it completely in shear forces, and not bending.  It’s a lot easier to deal with shear forces, than it is to deal with bending forces.

So that what we did by separtating the beam and distributing the forces.

Other Resources

Trebuchet Design

Cement Blocks


Sizing the Axle (Part 1)

Sizing the Axle (Part 2)


Car Throwing Trebuchet

Cool Trebuchet Pictures

The bucket