The Knex More-for-less efficency series

Ok, i just posted my pistol, which wraps up my first knex gun series.It is featuring my guns which have decent range and features using less parts.........THEY ARE (in order that i like them):-The AR-4 Commando-Longbow SR-L-The SPEC-9 sniperand..................The Jackal.357enjoy building these very part-efficient guns!

Topic by DJ Radio 10 years ago  |  last reply 10 years ago


Maximum cooling efficency

I am looking to build a compact cooling unit, sized under 12"x12"x12".  I have seen and built 2 of the most common types of home made air conditioning units.... 1) Run air across a block of ice or other frozen object. 2) Blow a fan through a whirl (or other pattern) of copper tubing and pump very cold water through. So my question is which would offer more cooling capacity? The first option is cooling with Ice which is below freezing, with minimal surface area.  The second option is cooling with cold water but still above 32 degrees, could potentially have more surface area.

Topic by scubaru 8 years ago  |  last reply 8 years ago


What are the most energy efficent light bulbs? how to be more eco-friendly around the house?

I picked up my first ever issue of Mother Earth News and I absolutely loved it. What are some small things I could do to help save the planet?

Question by CrawdadMan 9 years ago  |  last reply 9 years ago


Is charcoal powder better than bricks?

What would happen, if you put charcoal powder instead of bricks in your bbq, Would it push up the heat, or is it just unefficient? Cuz it's really messy, I thought it would be easier to ask someone with experience. I have put it under camping channel, and if it is more efficant than bricks, I guess It could go under the survival channel.

Question by Pollu112 8 years ago  |  last reply 8 years ago


How can I generate a power source via EMF waves around us without using any other power source?

Tell simply and more efficent way while dealing with it. Also it must work and practically available as well as possible.

Question by asim164 9 years ago  |  last reply 9 years ago


Where can SCR's be found in Australia?

I'm looking for some scr's (silicon controlled rectifiers) in australia but have so far been unable to locate any local suppliers. I'm using them *naturally* to switch the power for a multistage coilgun. So far i have been using high rated microswitches, but they are constantly failing and i've heard scr's provide the power quicker and more efficently.Thanks :)

Question by pyroten 9 years ago  |  last reply 9 years ago


I need some solar help. Answered

Ok so i dont know a whole lot about solar but i love the stuff. I also dont have alot of money (byproduct of not having a job) and wanted to make my own solar stuff for cheep. I posed another question about this but it was poorly writen so im putting more time into this one. I bought 9 solar powerd garden lights from dollar tree and one car phone charger. Now ive been led to belive that if i take a 9V battery and hook it up to that car phone charger it can deliver a safe and efficent charge to charge my phone. However since i dont want to spend a ton of money on batteries i deside to turn the consept solar. Ive found a few bumps along the way so if you have any advise please share it.  1. First ive been told that you need to connect a solar pannal to a load (for example a motor) to get an acccurate reading on your multimeter about the panals output voltage. Is this true? 2. I measured one of the solar pannals with a load in the sun and was told the cell emitted 1.5 volts. I then put five of them in serize and only got of reading of 2 volts not the 7.5 i was expecting. 3. I dont understand the imprtance of diodes when it comes to solar projects but as far as i know their just a safety procaution to help protect your cells against damage. Is this true and if so can i make my project work without them. 4. I dont know how to messure the amprage on my multimeter. Do i need a knew device or am i just missing something.  Thank you so much for takeing the time to help me out with this.

Question by inconceivable1 1 year ago  |  last reply 1 year ago


advice on making a rail/coil gun also known as a electromagnetic accelerator for someone who understands basic electrics

Im looking for advice on how to make a "rail/coil gun", i understand the principals behind it and the componets needed but id like to know what is the most efficent and powerfull componets. have in mind im looking at making the gun completly portable but a stationary charging for the battery would be prefered id like to keep the device 12v dc if possible using a battery to charge up capacitors, a switching device which allows the capacitors to charge and switch of the battery input automatically to prevent the electricity draining back into the battery. also another switch which discharges the capacitors into the coils but is switched manually(trigger), multistaged coils hopefully around 16 if possible( the way i see it lots of power running into lots of coils means the projectile traveling faster and further) ive also been told that once the coils have been charged they'll need to be discharged within micro seconds and theres a certain componet which allows that im not sure exactly what that is?. Having many coils means ill need a timing mechanism to activate the coil when the projectile is within the magnetic field, ive done a bit of research on that and come up with a microswitch between every coil or infared diode and a photosensitive diode(not sure exactly the name of the second one). 1. how many rows of coils would i need for each coil, what gauge wire would best suit my needs, what grade of wire, a way to prevent the magnetic field affecting the coils next to it, to optimize the energy in the capacitors should i start with a larger gauge wire at the first coil and slowly decrease it per coil, 2. what size capacitors would best suit my needs also bieng small in size, also would it be better have 1 or 2 capacitors per coil 3. what sort of switching device would be best for charging the capacitors and isolating the battery when there charged 4. is there another switching device for turning on each coil seperatly when the projectile is in range of the coils magnetic field to optimize the use of the magnetic field 5. more info on when the coil needs to discharge would also be great any ideas or inputs would be greatly appreciated no matter how big or small or if only concerns a certain aspect, cheers, chris cross australia

Question by crossy 9 years ago  |  last reply 8 years ago