# Recent content by bikengr

1. ### Air resistance: cylindrical rotor in stator with air gap

I misspelled, that's Taylor Goertler
2. ### Air resistance: cylindrical rotor in stator with air gap

G.I. Taylor performed wide ranging and fundamental studies of this problem. While a fluid mechanics neophyte might be drawn to the laminar flow solution (which is trivial), the rotation of the inner surface leads to large centripetal accelerations of the inner layers of fluid, which unstably...

4. ### Flywheel Leg Press Design - How is this being calculated?

I can't tell if this forum is posting my input. Anyway, looks like they have typos in their use of R0, RT
5. ### Flywheel Leg Press Design - How is this being calculated?

Hi, I imagine I could help. Feel free to email me at bikengr AT netnet.net
6. ### How would you design this device?

What is the need to keep the salt dry, if it is going to end up wet? save a lotta space by dispensing saline or pushing water through valve-isolated wet salt.
7. ### Low Reynolds Number Flow Visualization Techniques

I seem to recall that a fun competition for a flow tracer was announced by a marine biologist out California way. The winning thing was some kind of neutrally buoyant little spheroids, that might have been sea urchin eggs or something biological like that. I have seen folks check ultra-slow...
8. ### Heating Torch Using a Fuel That Does Not Contain Carbon

that reminds me... I recall learning, years ago, about a welding process called "atomic hydrogen". I think the idea was, send H2 through an arc, which heated it up and in the process dissociated it. Not only was it hot, but also had a large 'latent heat' of recombination, producing very high...
9. ### Feedback control via ODE variable coefficients?

how to Seems straightforward to me. You make the function r depend on y, for example r= -K*(y- y0) where y0 is the desired population. This makes the derivative of y negative if y is above y0, and positive if it is below, so it shoots stably to the value y0. You can embellish this all kinds...
10. ### Aerodynamics: bullets, footballs, arrows?

The real issue is, what happens if not spinning? Long objects like sticks, if slightly angled to the wind, will tend to turn broadside. They are unstable going straight because the center of pressure on a tilted bar is well in front of the centerpoint. If you want a long slender object to go...
11. ### Open Call: propose a CubeSat payload

I think it could be cool to have night-time infrared thermography of building roofs, to see how much heat they leak. But I don't know if a cubesat is able to broadcast high bandwidth information (power and size issue). Also that could turn into a somewhat unwelcome monitoring tool. So how...
12. ### Help with gear ratios please

I'm embarrassed I didn't think of stepper motor. Shows that my mind is still pre-1980, at that time you had to be a real expert to wire up and program a controller. Now it's probably trivial. The term SERVO used to be reserved for a high torque, low inertia DC motor with shaft position or...
13. ### Help with gear ratios please

I'm not facile yet with this interface, so please pardon the lack of quoting. Let me tell exactly how a clock would do the job. Imagine a CUCKOO clock with weights that fall over a couple of days. Let's say a weight is 1 kg (it's probably less). You can replace the clock weight with the cart...
14. ### Help with gear ratios please

In the long ago this task would be solved with 'clockwork', a wind-up spring and a balance wheel oscillating to meter its unwinding. Basically you still want a clock. (The old kind with hands.) (In fact, the old kind that are not run by battery, because the very cheap battery style tend to...
15. ### Simultaneous equations

Just so. I tried to be quite explicit that I probably did not have all solutions. My main aim was to break the logjam, in which proposer was tied in knots about high order polynomials. I think I have done so, however cavalierly, and probably won't be adding more.