Electromagent¤
(Control the Magnetic Field Directly)
Actually also a variant of: Actively setting the gear.
Reminder: F=v B*B b*b / R
Make the magnet
- stationary, so that area b is constant, i.e. F linearly proportional to (controlled) B^2, nothing else.
- control B, Field Strength
We can achieve this via an electro magnet - which creates a magnetic field through the electrical current flowing through the coil.
No moving part - that is interesting.
Clear downside is the constant electrical current we have to have flowing through the coil.
Looking at this it's plausible that the total amount we need to spend to keep it up may be low though:
That's a 9v battery - not sure how long it lastet though - also not sure if the spinning wheel feedbacks into the performance of the magnet.
Plausibility - Strength¤
In the supermarket they sold these permanent magnets today:
Neodym, i.e. brutally strong, that's 2.5Kg, i.e. 25Newton:
But holding it close to the wheel: Nearly no effect... a bit harder - but not much.
=> We need at least 10 times that strength for an e-magnet.
Looking at a 80kg magnet: 40Euro, 24V, 0.4A but:
Checking back at the store:
Unsere Elektromagnete sind der verlässliche Partner wenn es darum geht präzise Haftkräfte auf den Punkt zu bringen. Unsere elektronischen Magnete sind nur nach dem Anlegen von elektrischer Spannung magnetisch, danach wirkt ein sicherer Restmagnetismus von ca. 5%. Nimmt man dem Magnet also die Spannung, verliert dieser umgehend wieder seinen Magnetismus. Diese schaltbaren Magnete eignen sich daher speziell für den Maschinenund Vorrichtungsbau, sowie für Transport- und Handlingssysteme. Features: Hohe Lebensdauer durch vergossene Spule max. 120 Sekunden Einschaltdauer Geringe Leistungsaufnahme Anschlussspannung 24V Gleichspannung Unbeachtlicher Restmagnetismus (<5%) Kabellänge beträgt standarmäßig 18cm, kann aber auch individuell für Sie produziert werden!
"Max 120 sec. power on period" -> No Go. :-(
What's this:
https://www.maqna.de/elektromagnete/bei-strom-abschaltbar
Same: Max. 120 Sec Turn On Time
I guess to get to that high field strengths, they must have an immense amount of loops in the coils, i.e. very small wire, for the form factor. Which has a lot of resistance, i.e. heats up...
I think electromagnet is dead for now.
More realistic is another mechanical, distance controlled (this time by the computer) permanent magnet on the other side of the wheel.
Or a generator...