Vintage motor questions/discussion

[Swath]

I made a video about my vintage koyosho motors, but vintage motors in general.

It's a rather long video (46 minutes), I accidentally refer to capacitors as condensers.

Just some motor tech I am curious about.

https://youtu.be/2M9jfI6NthM?si=3GniWIQv6m43BwDn



I'm not a you tuber and my video might be a little unrefined, I didn't know a better way to get my questions out there.

Jeff

[juicedcoupe]

I'm sorry, that video was a little too long winded for me.

What was the question?

[Swath]

I understand, it was a lot longer than I intended. I could have narrowed it down better. I guess I was trying to create more of a discussion and learning environment.

I'm building my Ultima Pro which I built and raced back in 88-89. I have 4 motors I used back then. I'm on hold waiting on parts to show up and I was looking over my old motors and that brought up a lot of questions.

Specific questions:

What's the theory behind cut brushes?

I found some vintage cut brushes for sale on the evil bay site that were very interesting. There was quite a variety of cut designs I never saw before. I showed them in the video.

I had only used a plain ol step cut brush. I used one that was cut to possibly change the timing? And another that didn't change timing. I also have set the did both if that makes sense.

I wonder if the cut brushes were primarily intended for "can" motors?

Why don't we do some of the things with the motors we did back in the day, such as:

Vary spring rate?

Use a brush to clean the commutator?

Use "com drops"?

What was the function of com drops?

What exactly were those electrical bits we soldered on to the motors? They don't seem to be used at all anymore.

I assume if I can get my vintage electronics to work I need to keep those electrical bits on the motors since I will attempt to use the old AM transmitter. I believe capacitors can dry out over time so I should replace those?

That's probably most of it.

Jeff

[juicedcoupe]

Here is a brush guide from the mid 90s.

Anymore, I put serrated brushes on nearly everything, with a medium spring. I want my motors to run pretty good, for a long time. I'd rather preserve my vintage motors instead of trying to get every drop off power out.

Comm drops are nearly extinct. Team Brood was making some but I haven't seen it in stock for a while.

A fiberglass pen can be used to clean the comm. Thats all the Trinity cleaner was.

New comm sticks still show up on Ebay fairly often. They do a little more than the pen.

[juicedcoupe]

You are likely referring to capacitors on the motor. They were used to reduce electrical noise.

Newer 2.4ghz radios aren't affected.

Some new motors still have them, they are just tiny (surface mounted) components.



Diodes were also used back in the day. They were originally used on foreword/brake setups. Do NOT use then with a reversing esc.

[Dangeruss]

I guess I was trying to create more of a discussion and learning environment.

Asking your questions on YouTube is like asking for auto repair advice from people standing around in the DMV.

In addition to juicedcoupe's reply, I always found Trinity's brush ad quite informative...




Also, the electrical bits we soldered onto motors back in the day were Capacitors on motors with reversable speed controllers to reduce radio system noise (interference) and Schottky Diodes to prevent reverse voltage spikes on motors without reversable speed controllers. Capacitors aren't needed with 2.4GHz radios but if your AM gear doesn't glitch when you get to the point of running it then the existing Capacitors are fine.

Comm Drops increased electrical conductivity between the brushes and the commutator for more power/rpm. RCCA did an excellent article on Comm Drops back in the day... I'll post a link when I find the article unless someone else beats me to it as it was a neat read.

With the decline of Brushed Motors the speed parts associated with them like harder and softer springs, cut brushes, etc. have declined in use as well. Buggy whips in the petrol age, and all that.

[tgfarrell]

I like this thread.

I have a question. When I power up my tx and then the rx, things twitch to neutral as expected. If i let it sit for a bit I can here the a servo doing a small twitch occasionally. Not sure if its the steering or throttle servo. Will need to pull the body so see for sure. Ideas on what this could be? Its a 35 year old RC10, stock MSC, AM Futaba electronics, stock Associated motor.

[juicedcoupe]

Here is another Trinity guide. It took me a little bit to find.

[juicedcoupe]

I like this thread.

I have a question. When I power up my tx and then the rx, things twitch to neutral as expected. If i let it sit for a bit I can here the a servo doing a small twitch occasionally. Not sure if its the steering or throttle servo. Will need to pull the body so see for sure. Ideas on what this could be? Its a 35 year old RC10, stock MSC, AM Futaba electronics, stock Associated motor.

It's not uncommon for servos to twitch a little, particularly older analog models.

If the servo isn't centered properly (requiring more than minimal trim), the twitch can be more pronounced.

External interference (electrical noise) can also cause the signal to get twitchy.

[Frankentruck]

I like this thread.

I have a question. When I power up my tx and then the rx, things twitch to neutral as expected. If i let it sit for a bit I can here the a servo doing a small twitch occasionally. Not sure if its the steering or throttle servo. Will need to pull the body so see for sure. Ideas on what this could be? Its a 35 year old RC10, stock MSC, AM Futaba electronics, stock Associated motor.

With a 2.4ghz radio I still have steering servos that make a little noise after sitting powered and centered for a little bit. A quick flip of the steering wheel quiets the servo for a little while. I think it's just how servos are, but I don't buy many brand new servos (I'm a cheapskate).

[TRX-1-3]

Not to hijack, but it seems possible to double the comm life of a stock motor by running those Trinity "offroad" brushes by 180'ing them (replacing with a new pair) after roaching either the upper or lower half of the comm. (before it's completely blown out). Did anybody do this bitd?

[juicedcoupe]

Not to hijack, but it seems possible to double the comm life of a stock motor by running those Trinity "offroad" brushes by 180'ing them (replacing with a new pair) after roaching either the upper or lower half of the comm. (before it's completely blown out). Did anybody do this bitd?
Screenshot_20250604_080408_Samsung Internet.jpg

They look like they were primarily used on 4 cell and mild/stock oval cars.

With the decreased surface area, they couldn't carry near as much current as a full brush.

[RogueIV]

Not to hijack, but it seems possible to double the comm life of a stock motor by running those Trinity "offroad" brushes by 180'ing them (replacing with a new pair) after roaching either the upper or lower half of the comm. (before it's completely blown out). Did anybody do this bitd?
Screenshot_20250604_080408_Samsung Internet.jpg

Some did. Those were mostly used to reduce friction.

Personally I always just used full faced brushes except with some stock motors that benefited from narrower brushes to decrease overlap.

If you want to really geek out, find a copy of Big Jim Greenmeyer's RC Motor Black Book. He was one of the greats at tuning and building brushed motors.

[TRX-1-3]

Not to hijack, but it seems possible to double the comm life of a stock motor by running those Trinity "offroad" brushes by 180'ing them (replacing with a new pair) after roaching either the upper or lower half of the comm. (before it's completely blown out). Did anybody do this bitd?
Screenshot_20250604_080408_Samsung Internet.jpg

Some did. Those were mostly used to reduce friction.

Personally I always just used full faced brushes except with some stock motors that benefited from narrower brushes to decrease overlap.

If you want to really geek out, find a copy of Big Jim Greenmeyer's RC Motor Black Book. He was one of the greats at tuning and building brushed motors.

Yeah I just used the standup full face's that came with the motors bitd. Always stock, always around that 20-$30 price point. But that thought just occurred to me.

[1911Colt]

Useless fact- Schottky diodes work exactly like regular diodes, except super fast.

Basically, current can only flow in one direction with any diode. Reverse the voltage and the diode's internal resistance goes sky high and no current flows. The Schottky switches on/off faster than regular diodes. Fast switching allows the Schottky to do a better job shunting electrical spikes.