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El Gecko

Vintage vs. modern brushed motors

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Did some GPS testing after rebuilding a few old brushed motors, and then I tried a couple modern motors to see how they stack up, and I have to say I came away a little disappointed.

The modern motors I tested are all very smooth on acceleration, and seem to have good punch, but their top RPM on a 7.2V pack seems much lower than I expected.

The GPS confirmed this, with both cheapo 21T (Amazon) motors coming in 1-2mph slower in the same car than my recently rebuilt 27T Point Blank stock motor, which was a big surprise.

I know there's double/triple/quad/whatever winds to get more torque or more top speed, and armatures can have lots of different slot configurations, but has anyone taken one of these generic black cans apart to confirm what's in them and why they might perform differently?

In fact these 21T motors are about the same top speed as an old 27T Yokomo stock motor, so I'm wondering if they're just tuned for torque instead of top speed? Since most brushed motors these days are intended for crawler usage rather than racing. But I'd still be curious how they did that "tuning"--more slots? higher winds? Who knows?

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I have a couple of cheap Chinese 21t and 19t motors. They are sub-standard. I wouldn't trust their turn numbers. 

In fact, if you open it up, you will discover that the wires are never this thick. 

2hwWp4f.jpg

The whole reason why 21t should be faster than 27 is because 21t would use beefier wires.  I wouldn't be surprised if they are using the same wire used on 27t, but just wind it 21 times.  That means 21t could be slower than 27t!  Not all Chinese stuff is bad, but those cheap brushed motors?  I think it's better to spend the whole 17USD and get a Tamiya Sport Tuned.  

 

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9 hours ago, El Gecko said:

Did some GPS testing after rebuilding a few old brushed motors, and then I tried a couple modern motors to see how they stack up, and I have to say I came away a little disappointed.

The modern motors I tested are all very smooth on acceleration, and seem to have good punch, but their top RPM on a 7.2V pack seems much lower than I expected.

The GPS confirmed this, with both cheapo 21T (Amazon) motors coming in 1-2mph slower in the same car than my recently rebuilt 27T Point Blank stock motor, which was a big surprise.

I know there's double/triple/quad/whatever winds to get more torque or more top speed, and armatures can have lots of different slot configurations, but has anyone taken one of these generic black cans apart to confirm what's in them and why they might perform differently?

In fact these 21T motors are about the same top speed as an old 27T Yokomo stock motor, so I'm wondering if they're just tuned for torque instead of top speed? Since most brushed motors these days are intended for crawler usage rather than racing. But I'd still be curious how they did that "tuning"--more slots? higher winds? Who knows?

Is this a sealed can motor you are comparing against?

There are a few differences with a 27T stock motor:

- Better magnets (or at least they would have been when new)
- Timing advance (locked at 24 degrees mostly)
- Armature stack optimised for performance (usually lots of laminations missed out rather than being full length)
- Better brushes

etc etc etc

So not much comparison.

Even if you look at one of the cheap rebuildable motors, they are made to be "just a motor" and don't have the same optimisations.

Better comparison of sealed can to rebuildable stock is a Mabuchi silver can (27 turns) and a racing stock motor (27 turns). The difference is immense. These cheap 21 turn motors are likely faster than a silver can, I've used the Core RC branded one in the past and although it is a pretty soft motor, it's probably faster than a 27 turn.

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It's always been like that though tbh. Back in early 2000's I ran a Reedy Spec 19, 19T motor. It would keep with the cheaper made 12T and even 11T motors with no issues at all. Even my old Green Machine 3 27T rebuildable stock motor was rated at 33000RPM @ 7.2v !! It would take a decent spec 19T motor before it would be faster than a good quality 27T rebuildable stock motor (P2K, GM3 etc etc)

James.

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11 hours ago, BelknapCrater said:

Are these the motors marketed as Hackmoto/Trackstar/whatever else?

Yes, and they are all rebuildable (no sealed cans in this group). The two 21T motors came in combo deals with ESCs (generic Hobbywing clones) so I wasn't expecting blistering performance, but it was just very odd to me that these were no faster than older motors with higher turn counts in worse condition. Especially because I got the 21T hoping it would be a step up from the old 27T stockers I usually run. They do have just slightly more power and are a bit smoother on the low end, so they're not bad for basher motors, and are particularly good for short tracks (like racing by post). They're certainly not speedrun motors, though.

 

11 hours ago, Juggular said:

I have a couple of cheap Chinese 21t and 19t motors. They are sub-standard. I wouldn't trust their turn numbers. 

In fact, if you open it up, you will discover that the wires are never this thick. 

2hwWp4f.jpg

The whole reason why 21t should be faster than 27 is because 21t would use beefier wires.  I wouldn't be surprised if they are using the same wire used on 27t, but just wind it 21 times.  That means 21t could be slower than 27t!  Not all Chinese stuff is bad, but those cheap brushed motors?  I think it's better to spend the whole 17USD and get a Tamiya Sport Tuned.  

 

Aha I think you're onto something here. This seems to be the most likely culprit for manufacturing/cost cutting to me: the correct number of turns but using the same wire gauge as a 27T motor.

It would explain the performance, too. The armature on a 21T would be lighter than a 27T so it spins up slightly faster, but the RPM would hit the wall sooner due to the thinner wire (and less wire overall).

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On 12/6/2021 at 4:05 AM, Juggular said:

I think it's better to spend the whole 17USD and get a Tamiya Sport Tuned.  

I have an Absima 19T Thrust Spec Motor that is nowhere near the Performence of a Tamiya 23T super Stock BZ Motor.

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32 minutes ago, whahooo said:

I have an Absima 19T Thrust Spec Motor that is nowhere near the Performence of a Tamiya 23T super Stock BZ Motor.

Yep, if wires are thicker in the 19t, then Tamiya's magnets must be stronger.  That Absima 19t is a double wound motor, which would be less punchy too.  I liked tinkering with brushed motors, it's a shame that it's a rather obsolete tech now. 

 

Edited by Juggular
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Conrad has some rebuildable Motors, but they have even worser (more worse?) specs than the Absima Motors, the 15 or 17T Motors have lesser RPM and Tourque than a Sport Tuned.

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14 hours ago, Juggular said:

Yep, if wires are thicker in the 19t, then Tamiya's magnets must be stronger.  That Absima 19t is a double wound motor, which would be less punchy too.  I liked tinkering with brushed motors, it's a shame that it's a rather obsolete tech now. 

 

Did you`ever handwinde a rotor?

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On 12/7/2021 at 6:00 AM, Juggular said:

Yep, if wires are thicker in the 19t, then Tamiya's magnets must be stronger.  That Absima 19t is a double wound motor, which would be less punchy too.  I liked tinkering with brushed motors, it's a shame that it's a rather obsolete tech now. 

 

Yep remember the days of different brush springs on the + and - side. Different cut brushes, serrated, holed etc. Brushless has taken all that away, but on the plus side you do get peak performance every run every time with almost zero maintenance 👍

James.

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On 12/7/2021 at 3:24 PM, Collin said:

Did you`ever handwinde a rotor?

No, I only played with motor lathe at most.  

The only thing I learned was that just sandpapering was almost as good.  If I raced, I might be able to tell the difference, but no fancy equipment required for bashers.  

HpjVKhs.jpg

The one on the left is a commutator lathe, the one on the right is a brush lathe. 

 

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6 hours ago, Juggular said:

No, I only played with motor lathe at most.  

The only thing I learned was that just sandpapering was almost as good.  If I raced, I might be able to tell the difference, but no fancy equipment required for bashers.  

HpjVKhs.jpg

The one on the left is a commutator lathe, the one on the right is a brush lathe. 

 

I used to use 1000 wet and dry for my Comms. Was every bit as good as a lathe for a few attempts until the comm started to go concave. But wasn't a big deal after the brushes bed themselves in. 👍. These cheapo brushed motors these days are a joke tbh, the 12T cheapos on sale these days wouldn't even keep with a 19T spec back in the day .

James.

James.

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9 hours ago, InsaneJim69 said:

These cheapo brushed motors these days are a joke tbh,

Yes, it's like there is a 30 year setback.  What used to be done by top of the industry has gone to mom-and-pop shops. 

 

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On 12/7/2021 at 3:24 PM, Collin said:

Did you`ever handwinde a rotor?

I've always wanted to, maybe I should try and rewind these Chinese motors with the correct spec wire...

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16 hours ago, El Gecko said:

I've always wanted to, maybe I should try and rewind these Chinese motors with the correct spec wire...

Me too. I have a LRP motor with death comm and windings but sadly th shaft is bent : (

I think it would be very interesting to handwinde a motor. Wires cost nothing. The only thing is how to ballance the rotor at the end. Static or rotating ballancing, as you do it with crankshafts or flywheels on motobikes for exsample.

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I own only brushed motors avoiding as the plague cheap chinese stuff, the motors I'm using are Tamiya's, LRP, Atlas and some refurbished Corally bought years ago.
Now I'm collecting some vintage, used and somethimes abused motors with the idea to refurb and use them.
I also bought for a bargain prince a comm lathe but in the good old days I were used take care of comm with a stripe of sandpaper.

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On 12/6/2021 at 8:35 AM, sosidge said:

Is this a sealed can motor you are comparing against?

There are a few differences with a 27T stock motor:

- Better magnets (or at least they would have been when new)
- Timing advance (locked at 24 degrees mostly)
- Armature stack optimised for performance (usually lots of laminations missed out rather than being full length)
- Better brushes

etc etc etc

So not much comparison.

Even if you look at one of the cheap rebuildable motors, they are made to be "just a motor" and don't have the same optimisations.

Better comparison of sealed can to rebuildable stock is a Mabuchi silver can (27 turns) and a racing stock motor (27 turns). The difference is immense. These cheap 21 turn motors are likely faster than a silver can, I've used the Core RC branded one in the past and although it is a pretty soft motor, it's probably faster than a 27 turn.

There is another possibility, namely the nature of the winding and quality of ancillaries like bearings, magnets and such.

BITD, your top-spec brushed motors would be hand-wound, balanced and would feature top-spec bearings and the like. There were also motors with machine-wound armatures that theoretically had similar performance, but in reality were nowhere near.

My first ever modified was a machine-wound Schumacher 17x2 "Red Heat", which I used for Saturday racing in my Mid. It was considerably quicker than the 27 stocker I had been using up until that point, but it wasn't until I got hold of some decent hand-wound modifieds later that I realised how gutless it actually was.

There is also the question of timing, which can be adjusted to suit different performance profiles. A motor suited to crawling will have a different spec to one used for racing or general bashing use, for example.

Given that they are being turned out by the thousands for general use in hobby cars rather than for high-level racing, I would imagine most of the brushed motors on the market now have machine-wound armatures, questionable tolerances, low-quality bearings and generally little to recommend them apart from their low price. It would not surprise me at all to find they can be out-revved by an ancient stocker, since they were a class of racing motor and probably had far better production standards, even if they have a higher winding.

That's not to say they are useless – I have bought several of different winds myself for bashing – but you get what you pay for. If you want top-level performance from brushed motors, you might have to go back to refurbishing old modifieds from the era when they were still top-of-the-line items.

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On 12/5/2021 at 10:05 PM, Juggular said:

I have a couple of cheap Chinese 21t and 19t motors. They are sub-standard. I wouldn't trust their turn numbers. 

In fact, if you open it up, you will discover that the wires are never this thick. 

2hwWp4f.jpg

The whole reason why 21t should be faster than 27 is because 21t would use beefier wires.  I wouldn't be surprised if they are using the same wire used on 27t, but just wind it 21 times.  That means 21t could be slower than 27t!  Not all Chinese stuff is bad, but those cheap brushed motors?  I think it's better to spend the whole 17USD and get a Tamiya Sport Tuned.  

 

 

This is an issue that has gone back a long ways.

I've also seen "double" wound motors just literally doubling the number of winds. 5 turn triple had 16 winds. Many laughs were had. Many pockets were sad.

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I have some 'vintage' modified brushed motors. 2 are brand new in packets and never used. Anyone UK and interested, PM me.

 

Mostly fairly low turn, 11x3 for the new ones. Others are 10, 11 or 12 turn.

IMG_6479.jpeg

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In case there was any doubt, this is why the new cheapo motors don't have as much torque as more expensive or older ones.

Exhibit A:
Snow Panther Hobby 17T TUNED MACHINE

I finally got some time to pull one of these apart, and as you would expect, the cheapo 17T on the right has many fewer windings than the 27T '91 ROAR stocker in the middle, but you all were totally correct: the wires are either the same, or possibly even a smaller gauge!

This means much less rotating mass and higher RPM, but also much less torque, which explains why they drive the way they do. I'm not sure of the turn count on the ancient modified arm on the left, but you can clearly see the thicker wires there.

I'm curious to do some swapping around, to see how the old armatures respond to the new can. Assuming they work on similar principles as my HO slot car motors, they should perk right up since magnets are quite a bit stronger these days.

armature_comparo.jpg

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Oh dear. Typical Chinese junk factory ignorance. If they had only bothered to find the right wire gauge to fill the arm, the motor would have been so much better.

You see this a lot with the dirt cheap products. 90% of what they have done in the factory is really good, but then the 10% of not giving a cr*p about quality ruins the whole thing.

In fact there's a lot of "premium" priced products out there that are coming off the same production lines with a fancy label. You've got to be careful.

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I think the issue is that back 20+ years ago we were racing with brushed motors exclusively and we all cared and were extremely picky about how the motors performed.   I tuned motors all the time to the point my 27 turns were usually faster than most folks racing and the announcer even stopped me after the race to check the arm to make sure I was not cheating by using a different armature.  

I've not raced in a long time, but unless it is like a controlled race with hand out motors, I don't think most people bashing with brushed motors really care or know how a brushed motor in a certain turn is suppose to run..(?). opening up opportunities for these cheap manufactures to inject junk motors into the market place and try to get away with it.. well until the @El Gecko Police chimes in.  :lol:

 

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I agree with all the above, I own a comm lathe and rebuild my own brushed motors, the Chinese new ones are junk, you get what you pay for.....

The only new brushed motors that perform like they should are Tamiyas range of Superstock motors, I 

Even the modern Reedy Radeon 30,000 rpm motors don’t do 30,000 rpm .........

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