[NSRCA-discussion] Himax 6330 rebuild

[Bob Kane]

This knowledge is in the dusty mental archives from my university days, but basic motor theory will show a motor develops a voltage when it spins. We will call this the "back EMF" voltage.  It is easy to measure with a brushed DC motor, hook it up to a voltmeter and spin it. You will see the voltage rise as the RPM increases (and drop as it decreases). This voltage is a function of many things, but we will focus on RPM and the strength of the magnetic field. The current drawn by a motor is the difference between the supplied voltage and the "back EMF" voltage developed by the motor.  Since the back EMF voltage is a function of how fast it spins, it will draw little current when unloaded, and the as we load the motor with a prop the current will go up.

Weak magnets will cause the motor's back EMF voltage to go down and result in an increase of the current drawn by the motor.

Bob Kane

getterflash at yahoo.com


________________________________
 From: Patrick Harris <harris7148 at gmail.com>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org> 
Sent: Thursday, May 2, 2013 3:31 PM
Subject: Re: [NSRCA-discussion] Himax 6330 rebuild
 


Verne,

I was thinking that may be the issue. I pulled it already so no way to do an amp draw. 



On Thu, May 2, 2013 at 11:29 AM, Verne Koester <verne at twmi.rr.com> wrote:

If the motor is demagnetized (usually caused by overload and/or overheating) the amp draw will increase dramatically. Of course to know that, you have to have a baseline amp draw from when the motor was new to compare it to. What you’re describing sounds like your old motor was demagnetized. You could try comparing the amp draw on your old motor with the amp draw on your new one.
> 
>Hope this helps.
> 
>Verne Koester
> 
>From:nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Patrick Harris
>Sent: Thursday, May 02, 2013 1:57 PM
>To: jpavlick at idseng.com; General pattern discussion
>Subject: Re: [NSRCA-discussion] Himax 6330 rebuild
> 
>Just last week I had to replace a 210. It was getting so hot you couldn't touch it. It was putting such a load on the Jeti that it shut down in the air. The bearings feel fine, so it may be the magnets. Can magnets cause this to happen?. Oh and a year or so ago I did replace the shaft in mine and it had just a hair of end play.
> 
> 
> 
>On Thu, May 2, 2013 at 10:13 AM, John Pavlick <jpavlick26 at att.net> wrote:
>You had to rebuild an electric motor? I thought they never wore out (which is why they’re better than glow engines)… LOL
> 
>Seriously, how long do magnets last in these big motors (if you’re careful about heat + current draw)? Does anyone offer a “magnet-zapping” service?
> 
>John Pavlick
>Cell: 203-417-4971
> 
>Integrated Development Services
> 
>From:nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Kirk Sutherland
>Sent: Saturday, April 27, 2013 11:14 AM
>To: NSRCA
>Subject: [NSRCA-discussion] Himax 6330 rebuild
> 
>I have rebuilt a Himax 210 . When I  replace the retaining bolt in the back how much end play should the can have in it when moved front to back ?
> 
>Thanks Kirk
> 
> 
>
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