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06-19-2017, 05:04 PM | #41 |
owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
| Re: Where can I find *hard* brushes?
Cheap cans last longer being over geared than rebuildables. They don't make much power, and power wears brushed motors. Get a 550 sealed can for your slash or go brushless. Otherwise you will burn up motors pretty fast with taller gearing. |
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06-19-2017, 05:18 PM | #42 | |
Quarry Creeper Join Date: Aug 2014 Location: home
Posts: 392
| Re: Where can I find *hard* brushes? Quote:
Sent from my LGAS375 using Tapatalk | |
06-19-2017, 06:06 PM | #43 | ||
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
| Quote:
Quote:
The exact balance of higher-turns vs. lower-gearing depends on the acceleration you want vs. the battery life you want. If you want faster acceleration up to a given top speed, you need a lower-turn/higher-RPM motor with lower gearing; on the other hand, a higher-turn motor with higher gearing will reach the same top speed at a lower overall rate of power consumption, with the tradeoff of slower acceleration when you hit the throttle. If you want to stick with a 550-size motor (which is my preference for something as big and fast as a SCT), on 4S the 21-turn TMP550 should give you more than enough speed. If you want to err on the side of safety, you could get the 30-turn limited edition one and gear it higher. Link? The only brushed RC motors I know of that are larger than 550s are the Traxxas Titan 775 and the Kershaw DeWalt 820. Last edited by THX_138; 06-26-2017 at 08:12 PM. | ||
06-19-2017, 06:11 PM | #44 | ||
Quarry Creeper Join Date: Aug 2014 Location: home
Posts: 392
| Quote:
Sent from my LGAS375 using Tapatalk Quote:
Sent from my LGAS375 using Tapatalk http://kershawdesigns.com/Motors-ESC...isonTable.html Sent from my LGAS375 using Tapatalk Last edited by THX_138; 06-26-2017 at 08:13 PM. | ||
06-19-2017, 07:44 PM | #45 |
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
| Re: Where can I find *hard* brushes?
Interesting. I didn't know Keshaw was selling that motor now. I thought they only had larger ones suitable for Summit-sized trucks.
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06-19-2017, 08:26 PM | #46 | |
Quarry Creeper Join Date: Aug 2014 Location: home
Posts: 392
| Re: Where can I find *hard* brushes? Quote:
Sent from my LGAS375 using Tapatalk Last edited by kongluc; 06-19-2017 at 08:27 PM. Reason: Edit | |
06-20-2017, 05:39 AM | #47 |
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
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That's a long time to have your eye on something. You know what, these Trinity 4403 brushes aren't going to work. My other test motor is already showing significant etching on the commutator, deep enough for me to slightly feel the ridges with my fingernail, especially near the edges of the comm pads. This is a 12-turn 540-size motor in a 1250g touring car with a 9.96:1 final-drive ratio, so the motor's operation consists of high RPMs and very little load, but these brushes are still doing a number on the comm. They're just too abrasive. It's odd, because the Reedy Plutonium brushes are a high-silver-content brush too, but even though they wore the commutators a lot, they never left raw scratches in the comm. They actually seemed to coat the comm with a thin layer of brush material, so the comm took-on a silvery sheen where the brushes touched. These Trinity 4403 brushes are just grinding the comm like sandpaper. I managed to scrounge-up some Reedy 729 brushes. Supposedly these have no silver content, but I don't care as long as they perform well and last a long time. These don't have eyelets on the ends of the shunts, so I don't have to cut the shunts shorter in order to solder them directly to the tabs; that seems to be an uncommon feature for copper brushes. Figures they'd be discontinued, like almost everything else good in this hobby. Last edited by THX_138; 06-26-2017 at 08:14 PM. |
06-21-2017, 06:14 PM | #48 |
I wanna be Dave Join Date: Apr 2007 Location: Arlington, Washington
Posts: 2,303
| Re: Where can I find *hard* brushes?
729 brushes are made by Sagami....both Holmes and I still sell them.....its the standard brush that comes with the teardowns we both buy, same as the Reedy motors did back in the day... When you cut off the eyelet, just leave part of it with the end of the shunt sticking out...don't lose any length that way and they solder up just fine. Later EddieO |
06-21-2017, 11:21 PM | #49 |
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
| Re: Where can I find *hard* brushes?
Really? Reedy 729s are the exact same compound? Interesting. I wish I'd known that sooner...but that's why I post on forums, so I can find out things like this. What are these "teardowns" you speak of? Do you buy pre-assembled motors and take them apart, instead of buying the individual parts? Or does "teardown" mean something else in this context? I haven't had a set of brushes with eyelets attached in my hands in a while, so I'll have to look at the next set I get to see what you're talking about. But if the eyelet can be removed without cutting the shunt shorter, that's a good enough solution for me. |
06-22-2017, 03:29 PM | #50 |
I wanna be Dave Join Date: Apr 2007 Location: Arlington, Washington
Posts: 2,303
| Re: Where can I find *hard* brushes?
Same compound, though there are other compounds available.... Teardowns is a term for motors that come from the factories for motors that are not fully ready to run fully, though it often got used for all motors from japan or china. Sagami sells us their generic teardown, which is a complete endbell, can with magnets (I get mine uninstalled), and a blank armature. For whatever reason, sagami has always put brushes on them, even though the arm was blank. I had them stop putting them on mine....cheaper and I did not always use them. Here is some pics on how to cut it...it leaves a small part of the eyelet crimp, but doesn't effect anything. Later EddieO |
06-22-2017, 06:15 PM | #51 |
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
| Re: Where can I find *hard* brushes?
Okay, I see what you mean. That definitely looks easier than trying to pry-off the crimped part of the eyelet.
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07-04-2017, 01:20 AM | #52 |
RCC Addict Join Date: Aug 2014 Location: Virginia, Near DC, USA
Posts: 1,607
| Re: Where can I find *hard* brushes?
The Reedy 729 brushes seem to be working well in my high-rpm/low-load rally-car motor. The car lost a couple MPH of top speed from switching to zero-silver-content brushes, but I was able to recover the car's original top speed by clocking the endbell to +12° -- which I now understand is where it should've been all along. (I only recently absorbed the necessary knowledge to understand why electric motors *require* a small amount of timing-advance in order to run properly, and I am now going through my entire collection to make the appropriate changes.) At first, I saw something that I had gotten used to with brushed motors, which was accelerated wear at the edges of the comm pads, slowly spreading across the pads, bringing the comm just enough out-of-round to reduce the motor's power. However, I recently had the self-inflicted "opportunity" to tinker with an old 1980's Tamiya Dynatech motor, and I witnessed how increased spring pressure transformed that motor from a spark-thrower into an ass-hauler. Now that my brushed-motor parts box has a variety of different springs in it, I decided to re-lathe the comm in my rally car motor (to get a blank slate for scientific purposes) and try Holmes XXX springs, instead of the XX springs I was using before. With the XXX springs, the accelerated wear near the edges of the comm pads is no longer spreading -- there are little grey dusty strips about 0.5mm thick on the edges of the comm pads, and unlike before, they're not getting any bigger. I've resigned myself to the idea that low-turn brushed motors running on LiPo are going to experience *some* accelerated wear near the edges of the comm pads, so if the stiffer springs are at least keeping it from spreading, then that's a good enough compromise for me. Also, the stiffer springs don't seem to be wearing the brushes faster than before; I suspect this is because any increased wear from the stiffer springs is still less than the increased wear from brush arcing with the softer springs before. Compromises like this are always necessary when combining technologies from different eras, in this case modern high-wattage batteries with old-school brushed motors. |
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