My understanding is that many wind tunnels combine a fine mesh with the "straitener". What type of netting fineness would be sufficient for a wind tunnel of this scale, and how much would you expect that to decrease the windspeed? Sorry I can't give you more info on the motor until I get to see it a...

Yeah, that was my understanding (on the motors) too. Is there any way to change the frequency of the AC? Run it through a rectifier and than a modified inverter? I'm sure I'll lose some torque - but this is a 1/3rd HP motor blowing air through a 4' duct; I have some to spare. ******** It's an AC mot...

Just build it really small, and with a .5:1 C:B ratio.

For just tossing stuff to a dog, I'd try a 12" chunk of 2.5" with an endcap on one end.

Fuel it with a syringe or something.

Don't even need a chamber fan in a chamber that small.

Alright, I've been conscripted to complete my vocational-technology instructor's wind tunnel. Some questions follow. 1) How should I design the collimator screen? Here's some design data on the tunnel: Tunnel is about 50" long; that's 8" of expander, 33" to the test object, and 9" to the end of the ...

There is a equalization hole; it's the green hole labeled "[diameter] .031" It's hard to see in the frontal view, because the cross hairs obscure it. And yeah, I'm being a very bad drafter and dimensioning a hidden line. I was lazy and didn't want to draw up an entire new view just so I could label ...

http://smg.photobucket.com/albums/v611/car2/SpudIdeas/?action=view¤t=valve.png That's a 3/4" tee, pipes leading into the top and left of the fitting are 3/4" sch 40 PVC, pipe to the right is 1" sch40 PVC - and would be longer than is pictured. Ok, it's a slightly atypical barrel sealing piston...

My understanding is that the amount of energy that is dumped is more important that the voltage or the current. Obviously, a fair amount of voltage is required to make sure you discharge your bank in the time alloted, but otherwise, I don't think it's important. And it'd be a bad idea to discharge y...

I'm not convinced that: a) Coil guns are the way to sidestep construction strength limits on the power of a launcher... with a coil, you still have large forces involved. Not to mention the power switching circuitry. b) Electro-thermal guns are the way to sidestep construction strength limits - you ...

"A-treb demo only allows 40kg counterweights" So? There is no viscous or form drag during the launch phase of a treb, so it scales perfectly. Change the mass of everything else in the design so that you put in the same object_mass:counterweight_mass ratio in ATREB as you are actually planning to use...

Ya know, there's a fairly good chance that the 4.9% test velocities where actually higher than the 4.6% tests... latke's data had a large standard deviation, and his averages in question aren't very different. I think the probability that the 4.9% is better is 26.5% (T-test), but I really don't know...

Sentence 1, 2: you look it up, calculate it, or guess. The GGDT website is an excellent resource. (hint: generally, you should model burst disks/barrel/chamber sealing/hammer valves with the option designed for that valve type.) Sentence 3: friction basically doesn't matter. Ignore it. Sentence 4: P...

You realize that a trebuchet of that size will have peak axle loads of a few tons, correct?

As far as all the rest of your figuring goes, check out <a href="http://www.ripcord.ws/atreb/atreb.html"><b>atreb</b></a>.

Is that a metal piston? A lighter piston would hit the endcap with a good deal less force. Secondly, I think I see a scar on the endcap where the corner of the piston hit it. I am prone to think that the piston hit the endcap directly. Any bumper is better than no bumper; you might try a ring of pol...

The resident physics professor is asleep right now, so I'm going to turn to Dhall... First off, launching a projectile at 409 fps (89* above horizontal) using the GGDT exterior ballistics tool is not equivalent to launching one at 818 fps (30*). Hang time, time to apogee, and the apogee in the latte...

Eh, I'm not so sure that one can model partly-horizontal launches that way. Let's examine a time step in which the projectile is launched at 30* above the horizontal at 100 m/s: We'll define drag to be equal to (velocity in m/s)² Basically, I cut the constants out of the equation. Still f...