On 02/05/2021 17:17, Rick C wrote:> On Sunday, May 2, 2021 at 11:38:25 AM UTC-4, Clive Arthur wrote: >> On 02/05/2021 16:22, whit3rd wrote: >> >> <snip> >>> >>> Classically, for a burst one uses a regular-old-motor and a flywheel. >>> An electric clutch doesn't need PWM, and doesn't dim the lights when >>> engaged. >> High torque short bursts? You need a Marinov motor... >> >> http://www.electricstuff.co.uk/bbmotor.html#article > > Interesting. I'll take the guy's word for it that it works. He says some things that don't make sense. > > "One can see immediately that the baI1- bearing motor has no back tension because there are no magnets, and the magnetic field of the current in the "stator" cannot induce electric tension in the metal of the "rotor". > > Thus the firm conclusion is to be drawn that the mechanical energy delivered by the ball-bearing motor is produced from nothing, in a drastic contradiction to the energy conservation law. " > > There is "back tension" because of the resistance that creates the heating. I assume he means no inductive counter EMF, but that's not what makes a motor work so who cares? The statement that the motion is produced from "nothing" is absurd and violates no energy laws. Maybe he is speaking creatively, intending to mock what others might say? > > This is a very low impedance device. I suppose the impedance can be increased by making the bearing balls smaller while keeping the radius of the race large. At some point this becomes counter productive to the lifespan of a high torque motor. The author also posts some errors. He claims the two motors have equal ohmic resistance, but says the larger motor draws a correspondingly higher current commensurate to the torque. If the current is higher, would not the resistance need to be lower? If he didn't use the same voltage in each case there is no comparison. > > Two other statements offered apparently without evidence. --- > The driving force is higher for bigger bores, as the curvature of the races is less. > The driving force is greater for bigger balls, as their curvature is less. > > I don't see this. A lesser curvature essentially lowers the leverage at a given distance from the point of contact. A greater rotation is required to accommodate the expansion. This would perhaps allow a larger speed of rotation, but either with no more force or with less force, but maybe I'm not grasping the full effect. I suppose since the expansion interaction area is greater this could result in a higher force. As the result is not so obvious at first glance, perhaps some measurement is in order. A lot would depend on the rate of cooling of the working area. I wonder if a thermal insulating layer might be of use? I'm also curious as to why box bearing don't exhibit this effect. Maybe there is too much area of contact lowering the electrical resistance and raising the thermal conductivity to a point the effect is nearly absent. > > I wonder if there is any practical use for such a motor? I'm guessing it is not very efficient. It might however, be useful at the very low end of motor size where torque is very important to overcome stiction. >Marinov was a bit of a nutter with all sorts of free energy type claims, but his ball-bearing motor does work in that it rotates, albeit with very poor efficiency. It would take an imagination far greater than mine to envisage a sensible use for it. I remember this being discussed in 'Wireless World' decades ago with various theories to do with magnetics etc, when it was obvious that it was really just a load of expanding balls. -- Cheers Clive
PWM for High-Torque Motors
Started by ●May 1, 2021
Reply by ●May 2, 20212021-05-02
Reply by ●May 2, 20212021-05-02
Clive Arthur wrote:> Marinov was a bit of a nutter with all sorts of free energy type claims, > but his ball-bearing motor does work in that it rotates, albeit with > very poor efficiency. It would take an imagination far greater than > mine to envisage a sensible use for it.Reminded me of Mazda's rotary engine (I know nothing about). There appears to be a "return of the rotary engine" maybe 2019. So, apparently it was not very successful.
Reply by ●May 2, 20212021-05-02
søndag den 2. maj 2021 kl. 18.41.30 UTC+2 skrev Cursitor Doom:> On Sun, 2 May 2021 16:38:18 +0100, Clive Arthur > <cl...@nowaytoday.co.uk> wrote: > > >On 02/05/2021 16:22, whit3rd wrote: > > > ><snip> > >> > >> Classically, for a burst one uses a regular-old-motor and a flywheel. > >> An electric clutch doesn't need PWM, and doesn't dim the lights when > >> engaged. > > > >High torque short bursts? You need a Marinov motor... > > > >http://www.electricstuff.co.uk/bbmotor.html#article > April the 1st was a month ago. I can't see any basis for this thing > working as described.it'll turn, but it won't be self starting and will ruin the bearings https://www.plantservices.com/articles/2007/022/
Reply by ●May 2, 20212021-05-02
Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:> søndag den 2. maj 2021 kl. 18.41.30 UTC+2 skrev Cursitor Doom: >> On Sun, 2 May 2021 16:38:18 +0100, Clive Arthur >> <cl...@nowaytoday.co.uk> wrote: >> >> >On 02/05/2021 16:22, whit3rd wrote: >> > >> ><snip> >> >> >> >> Classically, for a burst one uses a regular-old-motor and a flywheel. > >> >> An electric clutch doesn't need PWM, and doesn't dim the lights when > >> >> engaged. >> > >> >High torque short bursts? You need a Marinov motor... >> > >> >http://www.electricstuff.co.uk/bbmotor.html#article >> April the 1st was a month ago. I can't see any basis for this thing >> working as described. > > it'll turn, but it won't be self starting and will ruin the bearings > > https://www.plantservices.com/articles/2007/022/Ceramic bearings can solve the problem. Scott Manley describes the solution: "Scientists May Have Figured Out Why So Many Spacecraft Were Failing" https://www.youtube.com/watch?v=KibT-PEMHUU -- The best designs occur in the theta state. - sw
Reply by ●May 2, 20212021-05-02
On Sun, 2 May 2021 22:40:22 -0000 (UTC), Steve Wilson <spamme@not.com> wrote:>Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > >> søndag den 2. maj 2021 kl. 18.41.30 UTC+2 skrev Cursitor Doom: >>> On Sun, 2 May 2021 16:38:18 +0100, Clive Arthur >>> <cl...@nowaytoday.co.uk> wrote: >>> >>> >On 02/05/2021 16:22, whit3rd wrote: >>> > >>> ><snip> >>> >> >>> >> Classically, for a burst one uses a regular-old-motor and a flywheel. >> >>> >> An electric clutch doesn't need PWM, and doesn't dim the lights when >> >>> >> engaged. >>> > >>> >High torque short bursts? You need a Marinov motor... >>> > >>> >http://www.electricstuff.co.uk/bbmotor.html#article >>> April the 1st was a month ago. I can't see any basis for this thing >>> working as described. >> >> it'll turn, but it won't be self starting and will ruin the bearings >> >> https://www.plantservices.com/articles/2007/022/ > >Ceramic bearings can solve the problem.Trouble with ceramics is they're not very good conductors, though. ;-)
