High Revolution Jet Turbine
by TriDev, published
here is my Jet Turbine Project.
This is a hand operated high revolution compressor turbine blowing through a chopper ring thus generating pressure waves..
The design consists of a Modular High Ratio Step Up Transmission and a Fan/Chopper Stage.
My own challenge for this project is to get the biggest Step Up Transmission Ratio as possible!
The key to success is all about friction, strength and balance:
- lower friction -> higher possible StepUpRatio -> higher rpm
- get the tolerances right (gear play)
- strength to withstand high input torque to overcome all the friction.
- strong muscles, good grip
- well balanced turbine and drive shaft to avoid extreme wobble (more friction), wear, damage or even total failure from high rpm
Update 20151206 V05:
Uploaded AddStageV05 with Ratio i=4.71 and i=5.57 and corresponding Carriers
You can stack..
MainStage4.71 + MainStageCarrier4.71
AddStage5.57 + AddStageCarrier5.57
AddStage4.71 + Handle4.71
MainStage4.71 + MainStageCarrier4.71
AddStage4.71 + AddStageCarrier4.71
AddStage4.71 + Handle4.71
4.71x5.57x4.71 works but is much harder to turn. I think I reach higher rpm with 4.71x4.71x4.71 or maybe I'm just not strong enough. I will test more and measure over the holidays. V05 Stages are compatible with previous V04 prints as long as you use the corresponding V04 carrier/handle.
Update 20151103 V04:
uploaded new V04 Files:
- Adjusted tolerance of gearing
- Ratio of Main and Additional Stages still is i=4.71:
(zR = -52; zS = 14; zP = 19; mn=1.1mm; Gear Play = 0.40mm)
- Connector size increased from Hex 12mm to Hex 18mm for higher strength (mainly for the first stage)
- Floating rotary joint for turbine tip to reduce wobble
- counter Thumb-lever on handle for better grip/higher torque input on startup
I haven’t fully printed this release yet so it’s not verified. Tolerance of the gearing works for me but my printer isn't as accurate as I'd like it to be. Gear play is 0.40mm. Fit is on the tight side for me.. Any reference values/guidelines from experts that works for most of you all are greatly appreciated. I can export and upload files with these values if needed.
Print and verify this Release V04.
I am also planning on doing Stages with other Ratios:
Some math to do first..
Further I want to export only the bayonet lock sections for you to design other attachments for the Main Stage/StepUp Transmission. Fast rotating stuff is always fun. Wondering what you all will come up with. Or in high StepDown configuartion for high torque output applications..
I also need to create a setup to measure the frequency to be able to calculate the max rpm of the turbine..
..so stay tuned
Notes:I printed PLA with 0.4mm nozzle. Still have warping issues with ABS. I cannot print Nylon, POM, or other fancy low friction stuff (..yet) I am sure this would also improve the overall performance. maybe someone can verify/confirm this..? Repetier/Slic3r with 3 Perimeters, 3 top and 4 bottom. Turn down the speed for the Perimeters. Infill: I put small holes to force the slicing software to make shells (reinforcement tubes) where I needed extra strength. I used solid infill all 4mm for radial strength. 40% rectilinear for all the parts. 40% honeycombs for the turbine. It looked more evenly distributed and more uniform for radial strength.. not sure if it really matters but it didn't hurt... Don't use supports! I designed all parts to be printable with bridging and max 45° overhang only. Rafts and brims settings: If you get a good clean flat first layer without it, don't use it. It will save you the cleanup work afterwards. A note to all the dear Lefties in the Thingiverse ..mirror all the parts in your slicer. you will have more ease operating this THING and reach higher performance!!!
Breaking in of the planetary stages:
As friction is the main enemy cleanup and break-in is crucial for this to work.
Break the gearing free with an 10mm Allen Key. Clean the tooths of any excess material. Then use a M6 Hex Screw and a drill to break-in the individual stages. 5-10min should do. I started to use bearing grease as well (Molykote). I know the Challenge rules have a “100% printed” policy. It works without lubrication but my own personal challenge for this project is to get that THING as fast as possible and reach the limits of this design. Temperature of the Main Stage and the floating joint of the turbine tip is also an issue if you drive it for a while. especially with PLA. Grease reduces the friction therefore heat emission and it also helps to reduce wear and extend the lifetime of your Stages.
You also need to break-in the assembly without load..
Don't go to hard on it and let it ramp up to speed (especially with the drill) or you WILL shear of the Hex on the first Stage or the bayonet lock. Glue it back on with superglue in case it happens.
And be careful were you put your fingers. the energy stored in the inertia at the high rpm end will crush them if they get in the first stage due to the high reversed (StepDown) ratio. This really hurts, I can tell from experience!!
..and protect your eyes in case something breaks loose/gets sucked in and is ejected at high speeds!
You are responsible for your own safety and the safety of those around you. I cannot be held liable for injuries, accidental or sequential damage in connection with the use of this THING!
Balancing the turbine:
I recommend you to balance the turbine. Put a 12mm rod through the Axis and use a Prop-balancing device or something similar. Drill out / enlarge the little holes to remove some material on the heavy side of the turbine until it is as well balanced as possible. Don't pierce through to the fan blades!
Alternatively you can do it the cheap way:
Clean any excess material on the upper Intake-Ring until it is as round as possible and put the turbine on a level flat surface laying on the side. Give it a push and let it turn around and settle. (Note that the outlet is polygonal and not round for better bridging results) Mark the contact point to the surface. Repeat couple of times. Use different starting points and angles to minimize error due to geometrical deviation of the turbine and the effective flatness/levelness of your surface. Drill the holes on the side with the most marks. clear the marks and repeat until satisfied, respectively until the marks are "evenly" distributed around the turbine and you just can't tell which is the heavy side anymore...
How I Designed This
The principle of mechanical sirens is nothing new as such and has been used for many years. It generates a loud tone by compressing air and releasing it in pulsed portions. The tone pitch is the consequence of the release frequency, the loudness is the consequence of the pressure difference created by the sirens rotor.
Some interesting air raid sirens designs can already be found on thingiverse but they all more or less stick to the original design and some are powered by a motor.
For this challenge I wanted to keep the principle of operation and redesign it from the ground up. To make it new, unique and easily printable.
With this concept in mind I started thinking about it.
As the design has to be hand operated, a high ratio step up transmission was inevitably needed to reach the required speed where a compressor turbine would actually generate enough overpressure to be hearable and loud. The design would ultimately be influenced by how I accomplish this high step up transmission. And a lot of questions arose:
- max possible total ratio?
- reasonable ratio per step?
- layout of the transmission?
- assembly design?
- reliability and robustness?
- friction and efficiency?
- which design has best exploitation of the predetermined build volume and is easy printable?
..a lot of questions with no clear answers..
So the idea was to create a step up transmission design with interlockable transmission module blocks that can be combined, exchanged, tuned and redesigned... printed.. tested.. redesigned.. individually
I knew it would need some iterations to get it right and find the best ratio chain, max possible ratio, tolerances and printing settings. So I needed the design to be flexible, versatile and easily interchangeable..
My personal minimum goals for this project were:
- more than 100 db
- more than 6000 rpm
- having fun all the way..
- learn a lot
The StepUp Transmission
A planetary gear bearing offers a fun to print, highly tunable, integral, compact and robust bearing/transmission solution..
The perfect platform for such a module!
The Planetary Gear Stage is a transmission module with common interface that can easily be daisy chained, and optimized individually...
Main parameters to play with are:
- Gear module (size and strength)
The Fan Stage
A Compressor Turbine @ high rpm
The Chopper Ring
..chopping the airflow from the turbine and generating pressure waves. With the frequency of the generated tone we will accurately be able to measure/calculate the actual rotation speed of the turbine... in theory..
The Main Stage
coupling between the StepUpTransmission, the Fan Stage and the Chopper Ring
..or other attachments..
I am currently testing my V03 design.
One Main Stage at i=4.71 ratio plus two additional Stages also at i=4.71 ratio
4.71^3=> iTot = 104.5
Input revolution at ~1Hz -> turbine at approx 6000rpm!!!
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High Revolution Jet Turbine by TriDev is licensed under the Creative Commons - Attribution - Non-Commercial - Share Alike license.
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