/eng/ - Engineering

Drum is a miniature keg with a diameter of approx 150mm.

Posts are locked in place with little pins and the top rollers can be adjusted with the bolt. I wanted to use 2 bolts but didn't have enough nuts.

I tried driving it using a power drill and a rough polishing mop, with about 1kg of lead balls inside. Appeared to work best when the drum was being driven UP.

A video was recorded to attempt measuring the RPM by counting frames. Video information states a framerate 30.012822.

4 rotations were measured at an average of 23 frames per rotation.

92 (frames) / 30.012822 (frames/sec) = 3.07 seconds

4 (rotations) / 3.07 (seconds) = 1.3 rotations per second

= 78 RPM

Having seen the "machine" rotate at that speed, it looks very manageable and not extreme.

>>7

What are some good programs to let an idiot edit some video?

>>9

""Where

CS = Critical Speed
D = Internal drum diameter
phi = Diameter of tumbling media""

http://atomurl.net/math/

http://www.codecogs.com/latex/eqneditor.php

>notes

Some of the things I write down could be complete nonsense.

What's next on my list of things to do is to figure out how to calculate the forces involved in driving the drum. Need to find my notes on vectors and matrices and see if I can remember what the fuck I'm looking at.

The motor will be underneath the drum with an upwards force. This force must be sufficient to have enough grip to start turning the drum without slipping.

This upwards force will push the drum into the top 4 rollers, effectively leaving the bottom two rollers doing "nothing" during operation.

>>15

I had the bright idea of modelling it as a pair of stacked boxes and solving it as a friction/toppling problem.

I need to brush up on my basic mechanics because even this is too much for me right now.

>>16
>>15
>>14

More notes. Wondering about how roller orientation encourages or discourages stability.

With a straight sided drum there will be no taper to keep it in place.

Will tilting or angling the rollers force the drum to stay centred or is it an absolute requirement that the drum be tapered?

>>18

I'm going somewhere with this. Drive wheel needs to be damped because of the vibrations from the tumbling material inside.

How? My brain function is impaired with alcohol and retardedness.

>>6

Made a little more disorganised progress.

I've shopped around and think I've found some suitable parts:

~ 300rpm 12V DC Motor - 6mm shaft
~ Pulleys - 25mm & 16mm - for 6mm shaft
~ Bearings for 6mm shaft
~ Drivewheels - 65mm

>>13

These parts should run the 150mm drum at a speed of 83 RPM.

Somewhere between Optimal and Critical speeds.

>CS = 115 RPM
>Optimal Speed = 74.75 RPM

>>14
>The motor will be underneath the drum with an upwards force. This force must be sufficient to have enough grip to start turning the drum without slipping

My intuition says I need some sort of shock absorbing mechanism to reduce vibration from the shock loads of the media tumbling inside.

I've pieced together this spring loaded rocking arm but I still haven't actually analysed it to see if it's actually useful.

>>26

Making rough measurements I think the shaft hole in this wheel is ~4mm. Can probably drill it without problems.

Simple 12V DC motor. Will need a power source and a switch that I don't really know how to do. I think a car battery charger will work but that's not really useful.

The pulley and bearings seem fairly straight forward. The o-rings look a little small (70mm x 5mm diameter) and I've no idea how well the bearings will handle the load, I don't yet have enough numbers to try any estimated lifetime calculations.

>>27
>>26

It's hard to understate how awful I am at all of this. I've forgotten so much in only a year.

>>28
>>27

Obvious Incoming Problems

Getting an o-ring or pulley belt, the correct size, will probably be annoying.

Being able to transmit enough torque without slipping.

Having a motor that isn't powerful enough.

Making small and durable enough tensioners for the belt.

For scale

>>29
>>27

I've taken the motor specs: 12V, 300rpm, ~5W and tried calculating the rough torque I can expect from it.

At the 65mm drivewheel I think it will produce up to 0.2487 Nm at its surface, at 192rpm.

The drum will contain something in the, very guessed, range of 0.2kg to 1.5kg. Spherical/Cylindrical lead media. I'm not sure how to model this so I'm just doing some really basic stuff to have some numbers.

Lifting a point mass of 0.5kg to a height of 75mm will require 0.368 Nm

I'm fairly certain I'm making massive assumptions about basic fundamental things e.g. just because the units are interchangeable doesn't mean something automatically makes sense. The numbers are staying close together and realistic looking so far.

0.368 Nm > 0.2487 Nm

My next assumption is that the media will be rolling inside the drum rather than being lifted straight up, at the rate of the angular surface velocity of the drivewheel (and equally the drum surface).

The media will have an equivalent, lower, rpm that describes the actual torque required to run the machine at full speed (83 rpm)

>>6

I found something cool

Reading this http://www.space.com/25575-space-crystals-huntingtons-disease.html

Wanted to know more about this http://en.wikipedia.org/wiki/X-ray_crystallography

Lol "Goniometer"? ttp://en.wikipedia.org/wiki/Goniometer

What's a linear stage? http://en.wikipedia.org/wiki/Linear_stage



Maybe there's a rotary stage and we're back to goniometer BUT I did find this

tl;dr

http://www.rotation-stage.com/

It uses piezoelectric motors to oscillate a friction tip, LOTS of times, to drive a linear or rotary stage. Neato.

https://www.youtube.com/watch?v=loAhRLFFPNk

>>30
>>29

I've added the pivot the motor will rock on. There's a hole in the plate on the opposite side of the drivewheels for the bolt that will be used for setting the meshing force.

>>38

Not quite sure how to decide on the best place to drive the drum from.

>>39
>>40

I'm surprised at how bad I've got at simple stuff but I think it's starting to come back.

>Correctly identify all forces & reactions
>Resolve horizontal & vertical components and move on

I need to be less confusing and shitty. Need to run through my sketches and write things out in a sensible and coherent linear fashion with numbered equations etc.

If I behave really well I should be putting it all into a spreadsheet.

>>46

Made a full scale diagram comparing two positions for the drive wheel. The position of the wheel on the left came as a natural extension to the centerline between the drum and top-right roller.

When the drive roller is engaged then, in a static perspective, the drum will ONLY contact the top-right roller. It's in an unstable equilibrium, that is if you don't consider the drum deformations that will eventually lock it into position against the other rollers.

In a dynamic perspective, with the drum rolling Clockwise, the drum will be trying to drive itself towards the top-left roller.

I'm not entirely sure what the bottom rollers are doing right now.

I think I'm almost ready to make diagrams for the Z-Y plane. I could solve this very simply with vectors and matrices but I'm not ready to look at maths again, I took one look in my Further Mechanics textbook and winced at how much I need to refresh on.

>>6

So I made a little bit of charcoal, inside a cake tin over a fire, and made a black powder mix with it. Total 100 grams extra weight.

I tried fixing a power drill to the base to drive it but just couldn't get enough meshing force for the polishing mop to turn it well enough. I think I sat for an almost continuous run of 15-20 minutes.

Observations From Test Run

- One of the upper wheels was clogged with a bit of plastic meaning it was much more difficult to turn. This upper wheel was one of the ones in-line with the drive wheel (polishing mop), as described in >>47 . I believe forcing it to run with this defect made the circumferential damage on the drum center more pronounced, because of the increased meshing force required and possibly because of any additional vibration.

- The mounting board for the upper wheels is currently only attached with one bolt in the center. This means the board has rotational freedom perpendicular to the drums rotation, I think this lets the rollers and drum bind. While too much free rotation will cause the machine to lock, I think some form of damping here may prove useful because of heavy vibration and possibly deflection in the same of the drum.

- The machine does vibrate heavily due to the fact you have lead balls falling and thumping the drum's wall.

- The drum is made from thin steel. There is already evidence of critical damage to the wall, particularly where the drive roller contacts. Sharp creases in the metal have formed, the exact cause of which is unknown. It stands to reason that this material will continue to deform until it cracks and breaks.

- Letting this happen with black powder inside is a real danger. Dangerous in my current setup because I'm using a power drill to run the drive wheel, the power drill motor produces strong sparks.

- The power drill does not feel suitable for long term use. The AC motor spins too fast without much torque. Driving the drum at the correct speed requires the button to be depressed approximately 50%. The drill eventually begins to heat up (after 10 minutes) and I'm pretty sure that a few sessions of 40 minutes will quickly kill it.

>>50

Black powder was a fair enough success. I think I sat for no more than an hour tumbling it by hand (with a power drill). I burned a few samples, open air and lightly pressed into a small PVC tube. It lit up well and I think should be good enough for some small crap rockets.

I needed some charcoal for that so I've distracted myself a little bit by looking into how it's made and what "Bio-Char" is. There are some ideas I have that I want to explore to see how well it works.

There seems to be a lot of talk about how Bio-Char and Bio-Crude are the way forward and are excellent things to improve the environment. Carbon sequestering / carbon negative etc. I'd like to see for myself if it proves to be thermodynamically sensible.

http://www.biochar-international.org/biochar/carbon

My idea involves this can. It has a cone and a pipe.

2 posts with pictures because I'm quite happy how it turned out, considering how it was made with less than ideal tools i.e hands. The old brake drum, wheel bearing and random large piece of threaded bar proved to be quite effective at starting off the cone.

>>69
>>70

I did a test run with this set up that wasn't hugely successful. Wood was a little damp, flame was weak, after about 4 hours the most that was accomplished was some slightly drier wood.

I've fabricated a cyclone filter, have a slightly fresher bottle of propane to work with this time and the wood is drier. I've also had the idea of putting some crushed aluminium beer cans under the internal can to help distribute the heat more evenly. It's maybe not very likely but it would be nice if they melted and eventually formed some sort of cast block for the internal can to sit on.

I'm almost a little worried at the prospect of molten aluminium doing something bad.

# If there's water or moisture it could cause some sort of explosion, throwing metal everywhere - Not too concerned about this because it's somewhat contained inside the yellow bottle.

# There was a lot of red Iron Oxide on the interior of the yellow bottle. I have largely cleaned it with a wire brush on an electric drill, not perfectly because it was very dusty and it was going inside my drill. Iron Oxide + Aluminum = Thermite. I don't want a thermite reaction. I've collected a lot of the dust because I might as well try a controlled thermite experiment.

# Aluminium fires burn hot. Very hot. I don't know how to start one but it's something I don't want. It would be very cool if it happened but I don't have enough time or metal right now to replace whatever it destroys.

https://www.youtube.com/watch?v=Zzv6fIDsNwM
>Appropriate Technology graduate students at Appalachian State University in Boone, NC demonstrate the pyrolysis of biomass in an airless system. Using fractional distillation, three distinct, value-added products are produced: bio-char, bio-crude, and syngas.

This is the video that gave me the idea to do this.

I'll go into more detail about fabricating the cyclone filter in the next update. I hope to run the second test tomorrow.

>>77

Ran the experiment today. No aluminium fires, that's much too optimistic though I did however get some oil and charcoal.

I think I gasified the beer can coatings and made some charcoal with it, it was caught in the orange cylinder and solidified, lots of acrid smoke. Next time I'll fill the internal can with crushed beer cans and see if I can condense anything from the smoke. The only thing in the glass jar this time is from the wood contained in the can.

For the next experiment I need more data collection, the can will be filled with a more uniform media and weighed before and after.

The cyclone filter was fitted with a general rubber airline hose, the gas inside cooled too much before reaching the filter and condensed liquids ran back down into the can. Low vortex effect and low gas velocities maybe because: The nozzles are too large, too much heat loss, not enough mass flow.

Should probably make a dedicated bio-stuff thread.

>>83
>>77

Lots more unnecessarily large photos.

Finally got a version of Solidworks Flow Simulation working and ran a few quick and basic simulations to get rough figures and pretty pictures.

I recorded a video of smoke going into the jar. Rough guess that a puff of smoke moved approx 1cm in a second. The inlet boundary condition was set to 0.01 m/s and increased in increments of 0.01 m/s with the outlets set to a standard environment pressure. Gas was "air".

Hopefully I can start finding some real numbers for the minimum requirements of a vortex.

There's a before and after picture of what was put inside the can. It handled the very small amount of sawdust fine, it probably needs some form of metal screen to handle a full load of very fine material.

And finally you can see the big differences in heat the internal can experienced between experiment 1 and experiment 2. Placing the board covered in tinfoil on top seems to be a must, hotter flame helps but wasn't quite as important. The board was destroyed by the heat it was containing and just crumbled after it cooled.

Experiment 1 resulted in only a very small piece of discoloration across the bottom.
Experiment 2 had enough heat to pretty much entirely clear all of the surface rust.

>>87

Another picture of the simulation but from the side. At 1 m/s inlet velocity.

It shows signs of being a vortex with high density regions in the center but I have no idea how effective it is.

It says we can upload pdf so let's give it a go.

PDFs can be unsafe so if anyone can suggest the most sensible way of staying secure I'm all ears.

It's a partially formatted and complete report.

>>27
>>17

So I got a rubber tread general trolley wheel today and it's infinitely better than trying to drive with a polishing mop. It takes much less meshing force because friction.

It also makes a lot more sense than the cheap fancy model wheels, there's no way those crappy little things would withstand any serious force and I'm sure they would be shattered almost immediately.

Right now I literally have next to no disposable income, that's why I haven't bought anything until today.

I've also had the bright idea of using a cheapass battery drill to harvest a motor from. I can get DC 12V 550rpm motor for next to nothing and since it's a drill it will have a chuck and a gearbox. Plan is to use a PC PSU with a resistor to power it and do something silly with the battery.

>>6
>>119

I bought a cheap 12V battery drill to serve as the motor. I've soldered an IDE connector to it so I can power it with a power supply.

Battery drills aren't really designed to be driven continuously for several hours.

I wonder how long it will actually last, the planet gears are nylon or some other plastic while the drive gear and annular gear are some type of metal.

The type of gear found inside your battery drill is Planetary or Epicyclic
https://en.wikipedia.org/wiki/Epicyclic_gearing

I drew it on Solidworks and rendered it all shiny just because. And of course to get some final dimensions for the mounting parts.

>>38
>>39

>>119
>>120

This wheel took a long time to render for some reason.

Bumpy rubber texture? Bumpy metal?

>>122

Just looking at it from this view, my guess for failure will be a big bending moment in the gearbox and something snaps off unreasonably quickly.

>>6

Some textures with a bit of render time can make any shitty model look good.

>>124

Almost 30 minutes to render. Solidworks sucks dicks.

NVIDIA has all sorts of flashy graphics and videos to boast about how they improve Solidworks performance but they're actually useless outside of the actual modelling environment. There is no support or benefit for Nvidia when it comes to rendering (Photoworks/Photoview) and CUDA doesn't do shit for any of the simulations (FEA in solids or Flow Simulation).

I'm running a GTX 570 right now and it's no better than my GTS 250. Granted, it's far superior to using the "Software OpenGL" setting but Jesus "getting titty fucked on a bike" Christ, it would be nice to get the supposed mind-blowing enhancements advertised.

>muh workstation cards

I don't see the point right now.