8" motor Helwig Brush Upgrade Bulk Buy... - Page 2 - DIY Electric Car Forums

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#11
05-27-2012, 09:56 AM
 ruckus Senior Member Join Date: Apr 2009 Posts: 654

Well, there's only one way to find out isn't there?

I have carefully measured the temperature of the motor after driving continuous at 60 mph. The temp is consistently between 250F and 260F measured with an infrared thermometer. I will install the new brushes and do the exact same drive and remeasure the temp. If the temp is less than the energy went into go-power instead of heat. I can easily get the brushes at \$225 and do the experiment, I just wanted to save everyone some cash. Kind of that whole "work together community thing".

What confuses me is that we have 2 sets of empirical data which had the exact same outcome within 1%. There is NO data showing a brush change had no effect. Yet folks refuse to believe the data that has been collected. Instead you make several undocumented assumptions:

1. That your motor is already 85% efficient. Try more like 75%. Add 18% and you get up to 88%. Not bad. My motor is putting out WAY too much heat to be anywhere close to 85% efficient. Personally I am not very impressed. at all. In fact it is lame.

2. That 13% of 20hp could not POSSIBLY be released as heat. That is only 2.6 hp. I am not going to bother putting all the math on here, but that is entirely possible. Remember that heat moves FASTER the bigger the heat differential. So if I am getting 250f on a 60f day that is a 190F heat differential which is A LOT. Now we are probably only using about 16hp which would be about 2hp in heat. Again, completely possible if you bother to do the math. (please remember the comm is copper which moves heat very fast).

3. That Jenifer Aniston wouldn't marry a fine fellow like yourself. Step 1, you have to BELIEVE. Step 2, well, good luck anyway...

Cheers
__________________
www.northvalleyev.com

#12
05-27-2012, 01:48 PM
 onegreenev Senior Member Join Date: May 2012 Location: Marysville, CA Posts: 3,496

Quote:

Well said.
__________________
Change comes, one conversion at a time.
http://onegreenev.blogspot.com/

#13
05-27-2012, 02:04 PM
 jeremyjs Senior Member Join Date: Sep 2010 Posts: 370

The brushes definitely seem to raise efficiency. What would be really interesting is if someone with a dyno could do it at several different voltages and power levels between the standard forklift brush and the helwig's. Is the gain linear or non-linear (and in which direction) with higher power/load levels. From what I've seen and read the brush compound is a more efficient conductor and the split/dampened design provides more consistent contact with the commutator.
#14
05-27-2012, 08:35 PM
 aeroscott Senior Member Join Date: Jan 2008 Location: West Sacramento Posts: 1,316

It would be interesting to test the resistance of the different brushes . I wounder what the resistance of aircraft brushes is .
#15
06-27-2012, 10:05 AM
 ndplume Senior Member Join Date: May 2010 Location: Dallas, Tx Posts: 100

Rucus,
I'd be up for a set. What is the status. My 8" ADC is running.
NDP
#16
06-27-2012, 10:29 AM
 DIYguy Senior Member Join Date: Sep 2008 Location: Kitchener, Ontario, Canada Posts: 2,494

Quote:
 Originally Posted by aeroscott It would be interesting to test the resistance of the different brushes . I wounder what the resistance of aircraft brushes is .
What would you look for? IIRC, higher resistance brushes are used for higher current applications. The carbon composite has a resistance inversely proportional to temperature. As the temp increases... the resistance drops. Pretty kewl huh?
#17
06-27-2012, 10:48 AM
 ruckus Senior Member Join Date: Apr 2009 Posts: 654

Quote:
 Originally Posted by ndplume Rucus, I'd be up for a set. What is the status. My 8" ADC is running. NDP
Great! I was going to place the order next week. The more the better (cheaper). I will contact you with details soon.

Thanks
__________________
www.northvalleyev.com
#18
06-27-2012, 11:08 AM
 ndplume Senior Member Join Date: May 2010 Location: Dallas, Tx Posts: 100

I wonder how many of the folks here have power meters on their EVs? Putting one on mine really helped me see how much power I was using for various activities. It also showed how much power I was losing in my LA batteries. I'll expect that if these brushes help out, I'll see it on my power readings.
Do you know if Helwig will pre-radius the brushes for the 8" motors? I saw that on Jack's EVTV store.
#19
06-27-2012, 12:38 PM
 ruckus Senior Member Join Date: Apr 2009 Posts: 654

Yes, the brushes come pre-cut to the proper radius. Even so, it is best to use a break-in period of running the vehicle in neutral for several hours.
__________________
www.northvalleyev.com
#20
06-29-2012, 05:37 AM
 Dennis Senior Member Join Date: Feb 2008 Posts: 293

It should be obvious as to why the use of Helwig brushes have a gain in efficiency for DC motors. It is because of less brush bounce or none at all. Brush bounce is when the brush contact to the commutator is not complete because of the brush moving in which some of the brush surface area or none of it (very bad!!!) is not touching the commutator surface. This results in an increase in electrical resistance, more voltage drop which reduces motor speed, and more heat.

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