graeham

31 ms·

271.
Like it's your last chance to do it(graehamdouglas.com)
1 points by graeham 14y ago|0 comments
272.
by graeham 14y ago
I think what Chuck meant was that the speed of sound increases with pressure, so the pressure wave in front of the capsule would cause the transition speed to supersonic to be higher. I'm not sure this is a good thing though from a drag pe
273.
by graeham 14y ago
My "apples to apples" point is that density is not the only parameter to change when comparing ships to trains. 1. Assuming the same speeds. Ships go slower than trains (say 40kmph compared to 80kmph). 2. The frontal area is not the same
274.
by graeham 14y ago
Comparing hydrodynamics and aerodynamics here is not quite comparing apples to apples: I expect much less surface area is exposed to water on a ship than exposed to air on a train, and speed are lower. Drag scales with velocity squared.
275.
by graeham 14y ago
Old report, but seems to me that barge shipping is more energy efficient than truck or rail (see page x): http://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/53xx... More recent report from Europe comparing different transport modes f
276.
by graeham 14y ago
Great points! The lateral g load could be reduced by banking the capsule - but you still raise an important limit that even with banking would still cause an unreasonable curve radius. Launch loops are interesting. They seem to be even mor
277.
by graeham 14y ago
Both liquids and gasses are fluids and drag is worse in water than air, so the energy required would only be higher. Consider: is it harder to push your hand through the air or a tub of water?
278.
by graeham 14y ago
When fluids flow, there is a `no slip` condition at surfaces - that is the velocity of fluid at a surface is the same as the surface`s velocity. So in a stationary tunnel, the fluid may be moving at an average of 300 meters per second, but
279.
by graeham 14y ago
I was trying to compare the energy required to overcome friction of the air against the tunnel to driving the route conventionally. 80 million is an excessive number to expect want to travel at one time, which implies that driving is much
280.
by graeham 14y ago
“Cheaper than high speed rail” - why is high speed rail expensive? I believe because precision contact between rail and wheel is required. How would this be done cheaper in a tunnel? One issue with a tunnel is that even if the air and car
281.
Why I got a Blackberry(graehamdouglas.com)
1 points by graeham 14y ago|0 comments
282.
by graeham 14y ago
Well put. Toyota's lean manufacturing was in fact what I had in mind when referring to the origins of the term. I wasn't familiar with that particular example, but was referring in general to Toyota's reputation for trying to reduce vario
283.
by graeham 14y ago
I mostly agree with you, including the pains of moving my hoards of parts (or junk, as my friends call it). Ideas need time to ferment, but they spoil if they are left in the mind for too long without manifestation. This is exactly why I a
284.
Lean Prototyping Techniques for Hardware(graehamdouglas.com)
26 points by graeham 14y ago|7 comments
285.
by graeham 14y ago
Worth mentioning the patent was set to expire in Canada in ~18 months anyways. The US patent was set to expire in early 2012 but coverage appears to have been extended to 2019. The bigger resulting effect here might be from the establishme
286.
by graeham 14y ago
Second the "build your own" CNC. A good friend recently made a 2x2 CNC that does a great job on wood and Halloween pumpkins for about $600. He did most of the structural pieces out of carbon fiber so it looks awesome but took some time.
287.
by graeham 14y ago
Thanks for your thoughts, you brought up a few points I hadn't thought of. I haven't worked in a international corporate environment but the collaboration ability is an interesting advantage. Printed injection molds are also interesting.
288.
Perspective on 3D printers from a mechanical designer(graehamdouglas.com)
50 points by graeham 14y ago|46 comments
289.
by graeham 14y ago
The threads themselves don't expand, its that they re-arrange themselves so the material is larger in total volume, but the voids within the material are also larger. The solid material itself, of course, must be conserved. Think of a spo