Thursday, November 18, 2010

Homemade fan Jet

A few years ago I decided to build a Fan Jet Engine. I started with a stainless steel wine glass, a stainless steel chutney dish, high pressure duel stage computer fan, and a few small pieces of tubing.
S/S wine glass from thrift store.
When I purchased the S/S wine glasses (2) I had no idea what I would build. But soon after I came up with a plan. A jet engine, well a fan jet at least. I began by designing a flame tube. This is the most critical part of the build, it needs to create a cone shaped flame inside of the combustion chamber.
Flame tube mock-up.
After lots of research this is the design I came up with.
36 - 0.09375 holes = 0.24837890625 = 32%
12 - 0.125 holes =0.151875 = 19%
10 - 0.21875 holes = 0.3756347665625 = 48%
The total is 99% of the flame tubes flow.
I then proceeded to make the flame tube out of 0.875 S/S tube and capping the end. Once finished I cut the stem end off the wine glass leaving a 0.875 hole for the flame tube to be installed. And then welded the flame tube into the opening and drilled a 0.25" hole for the fuel tube in the capped end. I then began work on the fan side. Taking a S/S chutney dish from the dollar store I removed the bottom and welded the dish over the open end of the wine glass. To create a thermal break I used High Temp Copper Silicone to attach the fan mount tube inside of the chutney dish.
Finished Fan Jet
As you can see I cut and narrowed the output nozzle slightly. You can also see how the fuel tube entering the engine. What you don't see is how the tube bends 90degrees and enter the flame tube.

I have run the engine on butane and 5-12v dc and it produces enough thrust to move itself . I then made a smaller nozzle out of a vinegar dispenser lid and it increased the thrust a little. I did at that point start to make a thrust augmenter but never finished it. Maybe some day I will build something with the engine.

Monday, November 8, 2010

Pencil Gun Video

Thingiverse user Parkolay has printed two pencil guns and has sent me a video for all to see. It's hard to see the pencil.

These are his prints.

And this one is printed by Thingiverse user Linkreincarnate.

From their experiences it is clear the choice of elastics is very important. The outer two elastics can not be to strong or they will over come the trigger friction and inner elastic. You may be able to use as strong of elastic as you want but the inner elastic will have to be very strong and may make the trigger hard to pull.

Friday, November 5, 2010

Pencil Gun Trigger Detail

Close up view of my pencil guns trigger mechanism. Uses one internal elastic to return the trigger and latch to their rest positions. And two larger elastics to propel the piston forward and launch your projectile.

I designed this with the little pencils you get from Ikea and golfing in mind as the ammo. The barrel has a minimum diameter of 11mm and most pencils are 7mm's giving it lots of clearance.

Tuesday, October 26, 2010

3D view of modular printable airplane

I have spent the best part of the last month learning Blender and 3D modelling. And I feel as if I have reached the point where I can move on to the next aspect of 3D printing.On the software side of it, I still have to learn the slicing software and decide which one of the three (RepSnapper, RepRaps Software, or Skeinforge) I will use. I've installed all three on my laptop and run all of them, Repsnapper seems the cleanest and easiest but does not seem to slice as well as the RepRap software. Skeinforge on the other hand sounds to be what everyone is using but after opening it 10 times I still have no idea how to use it. It almost seems alien in its layout and wording. If anyone can point me in the right direction on which one to use and how to use it (maybe a link to a tutorial) , I would be grateful.

On the hardware side of it I am still waiting for parts.

Monday, October 25, 2010

Micro printable crossbow animation

I decided to enter Thingiverse's rubber band contest today so I designed this crossbow. It has lots of overhangs, nothing under 45 degrees so they should all print.

I have now been learning Blender and 3D modelling for 30 days and have created five projects so far.All are posted on Thingiverse after doing 2 tutorials from and 1 from and a bit of reading. My impressions of Blender are positive but it is not all that intuitive, I do have the advantage of not being trained in any other 3D programs and do not have to relearn what seem like odd short cuts. I have had a lot oh no moments, when I've pressed a key while the mouse was over a different panel making it a different function and not knowing what I had done, but all and all as long as you save after doing anything right you can model anything. The hardest part right now with Blender 2.54 is the face normals being inside out, then the recalculate doesn't correct them properly, so I have to correct them manually.

Friday, October 22, 2010

In the beginning there was nothing and man said let there be stuff.

I've started this blog to cover the progress of my Rep-Strap Huxley/Mendel. I will also be covering my 3D modelling experiences with blender and other inventions and fun stuff. My Huxley is built from wood and polyester resin using the mini Mendel/Huxley design but only 20% smaller then a Mendel. I've utilised three nema 17 1.8 degree stepper motors salvaged from dot matrix printers as well as the chrome plated guides and bushings. At the time of this posting it is in need of a thermistor, end stops, and testing.