Go Back   RCCrawler Forums > RCCrawler General Tech > Electronics
Loading

Notices

Thread: Where can I find *hard* brushes?

Reply
 
LinkBack Thread Tools Display Modes
Old 06-19-2017, 05:04 PM   #41
owner, Holmes Hobbies LLC
 
JohnRobHolmes's Avatar
 
Join Date: Nov 2004
Location: Volt up! Gear down!
Posts: 20,290
Default 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.
JohnRobHolmes is offline   Reply With Quote
Sponsored Links
Old 06-19-2017, 05:18 PM   #42
Quarry Creeper
 
Join Date: Aug 2014
Location: home
Posts: 392
Default Re: Where can I find *hard* brushes?

Quote:
Originally Posted by JohnRobHolmes View Post
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.
It's bigger than a 550...it's a monster truck motor. Longer can same diameter...made to carry it by itself at 35,000rpm at 4s mt's weigh 12-15lbs it can handle it....40-41mm diameter but it doesn't have that shroud like the titan, which makes the I.D. bigger to compensate and fit in the same spot

Sent from my LGAS375 using Tapatalk
kongluc is offline   Reply With Quote
Old 06-19-2017, 06:06 PM   #43
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default

Quote:
Originally Posted by JohnRobHolmes View Post
I'll get a new arm your way for further testing. Just need to get it into the rotation of manufacturing since it was a custom.
Thank you! I've never had to RMA a motor from you before, so I didn't know how involved the process would be. Should I use the address on your website as the return address for the armature I suspect as defective?

Quote:
Originally Posted by kongluc View Post
It's more me understanding what you have that will work not making a completely custom wind or anything

Like being capable of a higher load with out reducing rpm or voltage...58/11 is not my cup of tea...i found a closed endbell can that handles 4s 35,000rpm starting gear ratio is 58/20...see what im sayin?

Sent from my LGAS375 using Tapatalk
Motors aren't really limited to specific voltage ranges, they're just rated that way for warranty reasons. You can run any modern RC motor on 4S, you just have to be careful to use it in a situation where it won't stall and cause the battery to shove tons of amps through it. Part of it is selecting a higher-turn motor than what you'd use in the same vehicle at lower voltage, because a higher-turn motor will have more electrical resistance to limit the amps the battery can shove through it. The other part of it is gearing the motor to ensure it can get the vehicle up to your target speed -- and no higher. Higher-than-necessary gearing keeps the motor in low RPMs longer; motors have lower electrical resistance at low RPMs (lowest at 0 RPM and steadily rising until they hit top speed), so the battery will shove the most amps through the motor at low RPM, increasing the risk of overheating.

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.

Quote:
Originally Posted by kongluc View Post
It's bigger than a 550...it's a monster truck motor. Longer can same diameter.
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.
fyrstormer is offline   Reply With Quote
Old 06-19-2017, 06:11 PM   #44
Quarry Creeper
 
Join Date: Aug 2014
Location: home
Posts: 392
Default

Quote:
Originally Posted by fyrstormer View Post
Thank you! I've never had to RMA a motor from you before, so I didn't know how involved the process would be. Should I use the address on your website as the return address for the armature I suspect as defective?

Motors aren't really limited to specific voltage ranges, they're just rated that way for warranty reasons. You can run any modern RC motor on 4S, you just have to be careful to use it in a situation where it won't stall and cause the battery to shove tons of amps through it. Part of it is selecting a higher-turn motor than what you'd use in the same vehicle at lower voltage, because a higher-turn motor will have more electrical resistance to limit the amps the battery can shove through it. The other part of it is gearing the motor to ensure it can get the vehicle up to your target speed -- and no higher. Higher-than-necessary gearing keeps the motor in low RPMs longer; motors have lower electrical resistance at low RPMs (lowest at 0 RPM and steadily rising until they hit top speed), so the battery will shove the most amps through the motor at low RPM, increasing the risk of overheating.

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.
Thanks for the tips

Sent from my LGAS375 using Tapatalk

Quote:
Originally Posted by fyrstormer View Post
Link? The only brushed RC motors I know of that are larger than 550s are the Traxxas Titan 775 and the Kershaw DeWalt 820.
Kershaw 650s...16.8v 35,000rpm already confirmed the minimum gear ratio

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.
kongluc is offline   Reply With Quote
Old 06-19-2017, 07:44 PM   #45
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default 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.
fyrstormer is offline   Reply With Quote
Old 06-19-2017, 08:26 PM   #46
Quarry Creeper
 
Join Date: Aug 2014
Location: home
Posts: 392
Default Re: Where can I find *hard* brushes?

Quote:
Originally Posted by fyrstormer View Post
Interesting. I didn't know Keshaw was selling that motor now. I thought they only had larger ones suitable for Summit-sized trucks.
No that's for a maxx, I've had my eye on it for about a year now.

Sent from my LGAS375 using Tapatalk

Last edited by kongluc; 06-19-2017 at 08:27 PM. Reason: Edit
kongluc is offline   Reply With Quote
Old 06-20-2017, 05:39 AM   #47
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default

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.
fyrstormer is offline   Reply With Quote
Old 06-21-2017, 06:14 PM   #48
I wanna be Dave
 
Join Date: Apr 2007
Location: Arlington, Washington
Posts: 2,303
Default 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
EddieO is offline   Reply With Quote
Old 06-21-2017, 11:21 PM   #49
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default 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.
fyrstormer is offline   Reply With Quote
Old 06-22-2017, 03:29 PM   #50
I wanna be Dave
 
Join Date: Apr 2007
Location: Arlington, Washington
Posts: 2,303
Default 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
EddieO is offline   Reply With Quote
Old 06-22-2017, 06:15 PM   #51
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default 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.
fyrstormer is offline   Reply With Quote
Old 07-04-2017, 01:20 AM   #52
RCC Addict
 
Join Date: Aug 2014
Location: Virginia, Near DC, USA
Posts: 1,607
Default 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.
fyrstormer is offline   Reply With Quote
Reply



Where can I find *hard* brushes? - Similar Threads
Thread Thread Starter Forum Replies Last Post
Elliptic motor brushes hard to find? MadForce Electronics 10 05-26-2010 10:54 AM
Can't find brushes Jus Electronics 0 02-06-2010 03:42 PM
Hard to find rottenbelly Paint and Body 6 11-30-2008 05:16 PM
why is it hard to find... muddeprived Chit Chat 2 12-23-2007 06:26 PM
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 07:18 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO ©2011, Crawlability, Inc.
Copyright 2004-2014 RCCrawler.com