limit rotational speed with a mechanism?
limit rotational speed with a mechanism?
(OP)
Hello everyone, first post.
I'm working on a project where we need to incorporate a mechanism into a gear train which will limit the gears from spinning too fast. We will use a torsion spring to accelerate quickly to, say, 2000 rpm, but once we hit this ceiling we want to keep the rpms around 2000, while still using the energy in the spring.
We cannot use any kind of electrical speed controllers, only mechanical components.
I could really use some inspiration, does anyone have any ideas or leads?
Thanks
I'm working on a project where we need to incorporate a mechanism into a gear train which will limit the gears from spinning too fast. We will use a torsion spring to accelerate quickly to, say, 2000 rpm, but once we hit this ceiling we want to keep the rpms around 2000, while still using the energy in the spring.
We cannot use any kind of electrical speed controllers, only mechanical components.
I could really use some inspiration, does anyone have any ideas or leads?
Thanks





RE: limit rotational speed with a mechanism?
RE: limit rotational speed with a mechanism?
Ted
RE: limit rotational speed with a mechanism?
RE: limit rotational speed with a mechanism?
But ... they were regulating a constant-force flow of steam (that is, they were changing a control valve position based on turbine or engine speed), not a releasing a wound-up spring slowly expanding and letting its energy come from the relaxation position of the end of the spring actuator.
RE: limit rotational speed with a mechanism?
Seems to me there isn't a lot of hunting or overshoot with this type of control but I guess that comes from also having a damn great flywheel?
Incidentally, Citroen's 2CV was available with a centrifugal clutch. Now that was neat - on a 500cc 2 cylinder engine.
JMW
www.ViscoAnalyser.com
RE: limit rotational speed with a mechanism?
http://www.mcmaster.com/#rotary-dampers/=ex7piy
RE: limit rotational speed with a mechanism?
http://www.winder.co.za/Lilly%20Controllers.htm
Regards,
Lyle
RE: limit rotational speed with a mechanism?
Dashpots tend to have resistance proportional to velocity as well, since the flow is limited by a restriction orifice.
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RE: limit rotational speed with a mechanism?
The flyball governor as used on steam engines is a bit different than what you are looking for in that it operates a valve which then controls the engine speed.
But taking that idea and adding it together with the eddy current brake suggestion, how about this - are you familiar with the centrifugal advance mechanism used on pre-1980 automotive distributors, with the weights and springs? A spring(s) would retain a weight(s) in toward the center of the rotating shaft until the shaft speed was high enough that the weight(s) overcame the spring force. Similarly, you could build a magnet / spring arrangement on your shaft in which the magnet(s) were stowed at a small radius until the critical speed was reached, at which time they would move radially outboard to cause eddy current braking in a conductive annular disk. Hmmm, gotta go find my blank patent application forms...
Mark
RE: limit rotational speed with a mechanism?
No.
A flyball governor produces a linear motion output proportional to speed.
When used on a steam engine that linear motion output is used to open or close a valve.
But there is no reason why it couldn't be used to apply a friction brake, change the gap of a magnetic brake, open and close a damper on a fan, etc.
RE: limit rotational speed with a mechanism?
You are describing a similar (friction instead of eddy current) speed control system used on my 1920s Victrola. It has a governor that actuates a brake on the inside rim of the platter. Think fly-ball that actuates a friction brake instead of a steam valve.
RE: limit rotational speed with a mechanism?
IMO. To properly do what you describe you need a mechanical control mechanism. A centrifugal clutch or similar won't really limit the speed of the shaft in the same way. It may be possible but I doubt the accuracy of a simple clutch system used for this purpose. Basically you want some sort of mechanism to limit the torque the spring transmits to the shaft in such a way that the set point is calculated to be the point where inertialy the shaft is spinning at 2000rpm. There are many ways to do this. But most of them are more complicated than you may think. Not easy to construct, but really cool and work well. An example I got from a well known text on control engineering by Ogata. See attached.
Fe
RE: limit rotational speed with a mechanism?
Fe
RE: limit rotational speed with a mechanism?
RE: limit rotational speed with a mechanism?
It shouldn't have a lot of drag to retard your acceleration, unless this application is something like a pocketwatch, in which case, you've got some serious miniaturization and probably bigger challenges than the governor.
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