[AsianGuy]

So I have a fundamental understanding of mechanical ratios and motors, but I don’t understand why certain combination are said to be preferred - such as the preference of high torque motors paired with high speed gears over high speed motors paired with high torque gears. I also don’t understand how one max/min the system to achieve the highest rps (a proxy for trigger response) and fps.

On both my AEG I am using an ASG U-18000 motor, said to be around 26ish TPA, and SHS 12:1 gears (which I realize when you count the teeth, it’s more like 12.6:1). Currently I am using M110 spring and can shoot .28 bbs at 1.74 joules with 22 rps as measured via chrono and reconfirmed via audio using audacity.

When you work the math out (I’m going to round the numbers to make the math easier):
18000 motor is 300 revolutions per second. This means the pinion spins 300 times a second
Based on the gears ratio of 12:1, The sector gear should yield 25 cycles (shots) per second

Since I get 22 rps via chrono — I’m going to attribute the real life ‘yield’ being lower in part to the motor ramp up speed, me only having bushings, rounding errors, and etc. Regardless of all this…the math seems right.

Now having said all this, why do people not use High speed motors and High torque gears?
Let’s us examine an ASG -45000 motor and SHS 32:1 gears with all other things being equal

45000 motor would be 750 revolution per second. This means the pinion would spin 750 times a second
Based on a gears ration of 32:1, The sector gear should yield 23.5 cycles (shots) per second

And before someone saids a 45000, 13TPA, motor can't pull a M110 spring...why not if you're using 32:1 ratio gears?

This isn’t too far from 25… and one could easily use a different gear set, say 18:1 gears? And that should yield 41.5 cycles per second.

So what am I missing here exactly? Is high torque motor and speed gears just a convention everyone assumes is correct, or is there something else I’m not understanding? Ultimately we are just converting the electrical energy from the LIPO to mechanical energy in the piston, I don’t see how one combination of motor/gear is superior to another combination.

Input appreciated!

 

[BlackDogAirsoft]

You could do that. People just don't. For one, 32:1 gears are often finicky and troublesome. Secondly it would generate a lot more heat because there are more teeth and therefore more points of contact.
People do run high speed motors with 18:1s though. Good for when you don't want to change your stock gearset.

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[redmoon3580]

When you get past the surface level tech hive-mind, there are a fair amount of people who use mid/high torque gears with lower TPA motors. I do, granted I've never gone as extreme as you're suggesting.


There's electrical efficiency to be considered too. Lower TPA motors can use thicker wire, and a lot less of it. The difference isn't negligible. That said, most people can get a full day of play out of a buffertube lipo on even grossly inefficient builds, so it might not matter that much.


It also, in theory, generates a lot less motor heat. Running tons of current though the long thin wires that are in high TPA wires can generate tons of heat! In practice that also depends a lot on your shimming, motor height, pinion angle, etc.

 

[1tonne]

Higher Torque motors have less heat. High Torque motors have more wire wrapped around the armature (this is called TPA). The more Turns Per Armature the more it will create a magnetic field and this creates more spinning with less electricity. So free power in essence. The more electricity needed, the more heat will be made. While motors with less wires wrapped around the armature, need more electricity to create the power needed to pull the spring.
Also, High Torque motors tend to use Neo Magnets (Most have a strength that is about N35 like SHS but they can go up to N52), while a lot of High Speed Motors tend to use weaker Ferrite magnets. Neo Magnets are stronger and so they create more free power.

High torque motors matched with high speed gears do give really high rps but there is a point to where if your motor is too high torque, you will loose rps. For instance if you match a 13:1 gear ratio with a 32TPA motor you will most likely loose RPS compared to a 22TPA motor. So really what people are doing is matching the motor to the gearset to get the more RPS with the least heat possible.

Another thing is that High Torque Gears, since they have stronger magnets that grab the armature and stop it spinning around, tend to have less over spin. While high speed motors with weaker magnets tend to have more over spin.

Yesterday, I was experimenting and because I decided to use a 14.8v lipo on my DSG and left it cycling for about 30 seconds, the heat fried my mosfet (I was also fiddling with settings that may have helped fry it). LOL. (Lucky I have spare ones). Sounded great and fed OK but heated up very fast.
Maybe I should have used a higher TPA motor with the 14.8v to make less heat. But that would have given less RPS.

 

[AsianGuy]

What it sounds like the consensus is that we are trying to convert the electrical energy as efficient as possible (since heat was mentioned a few times) into mechanical rotational motion in the pinion.

This then brings up an alternative question, why have speed motors? If torque motor / speed gears beat speed motors / torque gears as far as energy conversion efficieny… and speed motor / speed gear won’t likely be able to pull a reasonable hard springs, why does speed motors exist? What situation would they be applicable (superior to their torque motor counter parts)?

 

[BlackDogAirsoft]

If you don't want to change your stock gears then high speed motors are a good way of getting high rate of fire and snappy trigger response.

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[FMP Airsoft]

I believe from what I've seen, the higher speed motors will gain a higher maximum speed, but will take a short amount of time to speed up to that maximum (as opposed to a torque motor, which will be slower at its maximum, but give snappier response due to an instantaneous speed up time). Does that make sense?

 

[Skara]

High speed motors are for those who can't tech and want to boost their RPS.
"EeTs gOt A HaIgH SpId MoTuRrR"

Meanwhile the gun eats more batteries than a high tier whore gobbles cocks and heats up so much you can cook an egg on the pistol grip.

A former teammate installed one crazy high RPM high speed motor which managed to kill 2 fully charged batteries in less than two hours.

 

[BlackDogAirsoft]

You can install a high speed motor in both v3 and v2 guns without opening the gear box and get a high fire rate. If you install a high torque, you need to change the gears to get a high fire rate. Needless to say, boosting rps without changing gearbox parts is a bad idea but there you go.
I use a high speed motor in my cyma platinum because it came with one and I can't be asked to change it.

 

[1tonne]

Normally, High Torque Motors will also make the gun snappier than high speed motors. High speed motors have higher speed but it takes a little time to get that speed (You may notice it). High Torque Motors get up to their max speed nearly instantly.

 

[redmoon3580]

Higher Torque motors have less heat. High Torque motors have more wire wrapped around the armature (this is called TPA). The more Turns Per Armature the more it will create a magnetic field and this creates more spinning with less electricity. So free power in essence. The more electricity needed, the more heat will be made. While motors with less wires wrapped around the armature, need more electricity to create the power needed to pull the spring.
Also, High Torque motors tend to use Neo Magnets (Most have a strength that is about N35 like SHS but they can go up to N52), while a lot of High Speed Motors tend to use weaker Ferrite magnets. Neo Magnets are stronger and so they create more free power.

I have a degree that's more or less in electrical engineering, and I have a not-insignificant amount of robotics experience that involves tracking the performance electric motors (both brushed and brush less) paired with mechanical transmissions, including gearboxes (albeit planetary). I can say with authority that your understanding of this stuff is fundamentally wrong.

Less related to the science and more to product availability: high speed motors don't have weaker magnets than high torque motor. If you buy the same brand and model of motor in a different "speed" they will come with the same magnets. I've got plenty of first hand experience with this, from upper end brands like Tienly or Action Army all the way to the cheapos like ZCI, and this has remained true.

Secondly, there is no free power. A higher torque motor will have more torque, but lower RPMs. Power is directly proportional to Torque AND RPM. High TPA motors are actually less efficient (power in vs power out). This is because they have significantly higher impedance. This impedance is directly caused by the TPA - not only are the wires in the motor much longer, because they need to fit more wire in the same space, the wire is much thinner.

What a motor can or can't pull also depends entirely on the transmission. Your transmission transforms some of your RPMs into torque. In our case it's the gears in the gearbox that determine this, since the "pinion" gear is fixed.

Most high speed gears are 13:1. Most high torque gears are around 26:1. This means that with high torque gears (compared to the high speed gears) you're trading twice the speed for twice the torque.

The efficiency (power in compared to power out) of "high torque" gears is very similar to "high speed" gears. Generally adding/removing a gear or changing the shape of the gears has a much larger bearing on efficiency than the ratio of the gears.

So, since "high speed" motors are more efficient than "high torque" motors, and "high torque" gears are equally efficient "high speed" gears, a combination "high speed" motor and "high torque" will be more efficient than the more traditional "high torque" motor and "high speed" gearset, even when geared in such a way that they have the same power output. This results in less heat and less battery usage for the same amount of rounds fired, for the same RPS and spring.

The advantage that "high torque" motors with "high speed" gears have is that they get to their peak speed faster. This doesn't net you an RPS advantage, but it does increase trigger response.

For most airsofters the extra power efficiency doesn't net them much since lipo batteries are so power dense. Similarly most airsofters aren't shooting so much and in such quick succession that motor heat becomes an issue. But the trigger response advantage offered by the latter set-up is fairly negligible too - either set up can easily get you past human reaction time.

I prefer efficiency. The 'tech hivemind' barely acknowledges it's existence. At the end of the day neither offers a big enough advantage on the field to matter much.

 

[1tonne]

I have a degree that's more or less in electrical engineering, and I have a not-insignificant amount of robotics experience that involves tracking the performance electric motors (both brushed and brush less) paired with mechanical transmissions, including gearboxes (albeit planetary). I can say with authority that your understanding of this stuff is fundamentally wrong.

I am always willing to learn.

Less related to the science and more to product availability: high speed motors don't have weaker magnets than high torque motor. If you buy the same brand and model of motor in a different "speed" they will come with the same magnets. I've got plenty of first hand experience with this, from upper end brands like Tienly or Action Army all the way to the cheapos like ZCI, and this has remained true.

Tienly motors range from N52 neo magnet (This is me surmising. See link below) right down to ferrite magnets in their 50000rpm motor. I see it advertised as neo on Evike but it is actually ferrite according to a reliable tech who sells them.
https://www.airsoftsociety.com/threads/tienly-magnet-strength.161923/#post-1826681

 

[1tonne]

The higher torque requires less amp draw from the battery, which creates less heat.
https://www.airsoftsociety.com/threads/motor-heat.122773/#post-1553807

 

[AsianGuy]

@redmoon
Thank you for the thoughtful reply – it was very helpful and helped confirm some of my suspicions that both systems were equality viable.
In your experience, have you encountered at what delay threshold is considered “instantaneous” trigger response for an individual?
Additionally, how much time difference is there to achieve maximal rotational speed of a high torque motor (say a 26TPA) vs high speed motor (say a 13TPA) with all things being equal? Are we talking a factor in the order of 2 or 3? Or are we talking about 10 in an application setting?

Lastly, outside of exhaustively checking each gear ratio and motor torque/speed ratio, is there a method to figure out the bare minimum for ‘instantaneous’ trigger response while increasing RPS? I realize the combination I’m using it’s nearly as extreme as it gets – 26 TPA motor with 12:1 gears – and while I do feel ‘instantaneous’ trigger response it would be great if I didn’t have to buy 200 dollars’ worth of motors to where I begin to feel the lag.

@1tonne
Does amps always equal heat? On the surface it makes sense, but what if a system is more efficient in its conversion of amps to mechanical energy, whereby it’s not actually generating as much heat as we’d expect – I believe that’s what the applied studies of thermodynamics attempts to do.
I recall being told by an environmental engineer that one of the reason you want big power plants over small ones spread all over is because big power plants are more efficient in reducing its carbon footprint, where by the carbon per energy output is much lower. This is of course offset by the ability to transmit power across long distances, so it becomes an optimization problem.

 

[1tonne]

@1tonne
Does amps always equal heat? On the surface it makes sense, but what if a system is more efficient in its conversion of amps to mechanical energy, whereby it's not actually generating as much heat as we'd expect

Not sure to be honest. I am really good with bolties (and AEGs') but when it comes to electrical systems and motors, I tend to rely on the knowledge of other techs. A lot of the techs from Airsoft Society seem to know what they are talking about when it comes to AEG's.

 

[redmoon3580]

[
Tienly motors range from N52 neo magnet (This is me surmising. See link below) right down to ferrite magnets in their 50000rpm motor. I see it advertised as neo on Evike but it is actually ferrite according to a reliable tech who sells them.
https://www.airsoftsociety.com/threads/tienly-magnet-strength.161923/#post-1826681

Guges is a distributor, not an engineer. He has a lot of insight into the industry, but doesn't always really have a strong understanding of the science.

Still, when it comes to magnets on Tienly motors, I stand corrected. I haven't gone as fast as 50k, which is VERY fast (especially since most manufacturers label their motor speeds based on no-load rpm @ 8.4v).

Using a stronger magnet does increase back EMF. This does NOT make a motor less efficient, but the same motor with a stronger magnet will be the torquier and decrease speed. Funny enough, using stronger magnets along with a lower "tpa" is often seen as a way to increase the efficiency of a brushed dc motor while keeping its other characteristics similar.

Back EMF is proportional to motor speed, and it's actually the mechanism that creates the behavior that's so easily abstracted as a torque constant. The slower the motor moves, the lower the back EMF. The more load a motor is under the slower the motor is. So, the more load a motor is under the lower the back EMF. As the back EMF shrinks the winding needs more current to maintain its potential (voltage) difference with the battery. With a little bit of abstraction this can be represented pretty basically using just ohms law and KVL.

As a general rule of thumb a motor will run most efficient at half its no-load RPM (though a less efficient motor running at its most efficient load won't necessarily be more efficient than a more efficient motor handling an unideal load). Of course, it's no-load RPM will depend on the motors voltage, and the load on the motor will depend on your transmission. There's a lot of variables at play, and at some point you have to make a few decisions and build the rest around those decisions.

So, going back to the Tienly 50k, it's possible that in order to get their motor to that speed (~60-66k with a fully charged 3cell lipo depending on if they measured it with an 8.4v power supply or a fully charged 8.4v nimh/nicd) they ended up using weaker magnets, but most "high speed" vs "high torque" motors only use their windings to differentiate them.

Using a weaker magnet would make their motor less efficient, and in this case the 50k is all for advertising.

@redmoon
Thank you for the thoughtful reply - it was very helpful and helped confirm some of my suspicions that both systems were equality viable.
In your experience, have you encountered at what delay threshold is considered "instantaneous" trigger response for an individual?
Additionally, how much time difference is there to achieve maximal rotational speed of a high torque motor (say a 26TPA) vs high speed motor (say a 13TPA) with all things being equal? Are we talking a factor in the order of 2 or 3? Or are we talking about 10 in an application setting?

Lastly, outside of exhaustively checking each gear ratio and motor torque/speed ratio, is there a method to figure out the bare minimum for 'instantaneous' trigger response while increasing RPS? I realize the combination I'm using it's nearly as extreme as it gets - 26 TPA motor with 12:1 gears - and while I do feel 'instantaneous' trigger response it would be great if I didn't have to buy 200 dollars' worth of motors to where I begin to feel the lag.

Diminishing returns on trigger response start way lower than most people think. If you look at trigger response like gaming input lag, many TVs have an input lag of over 50ms. If your motor spun up instantly that'd be just 20rps and you're set up would be as responsive as your average console + tv pairing. Of course your motor doesn't spin up instantly, but 50ms is still a very achievable trigger response even in an unoptimized set-up.

I think that most of the perception of trigger response actually comes from the sound profile. It's not that the gun fires faster enough to matter, but the sound makes it feel that much snappier.

If you have a gate titan you can easily measure your trigger responses. But chances are it's good enough that any more optimization would be diminishing returns. But. to answer your question, you can get trigger response around 30ms with either set-up.

Does amps always equal heat?

That's a loaded question. Heat will generally be proportional to impedance (resistance) AND amperage. Of course ohms law relates current and impedance to voltage. That's also why motors are hotter under load - the back EMF lowers their potential difference (voltage) so less current needs to run through the windings in order to keep KVL with the battery's voltage. As the motor goes under load and the back EMF drops and the potential difference increases.

A good way to think of heat is as inefficiency, since most inefficiency (energy in vs energy out) ends up released as heat. This inefficiency can be electrical - or it can be mechanical (i.e. friction in the gearbox). By minimizing inefficiency you're also minimizing the amount of energy that ends up as heat.

 

[crimbcebar]

Learned a lot from these comments whoaaa 🤩

 

[AsianGuy]

@crimbcebar

Yeah, redmoon3580 was extremely detailed, I bookmarked this for myself as a reference

 

[1tonne]

I have learned lots too. Some of what Redmoon has said has gone against what I have read on the net here but he seems to know his stuff.

 

[BlackDogAirsoft]

I have learned lots too. Some of what Redmoon has said has gone against what I have read on the net here but he seems to know his stuff.

It's good to hear from people who know what they are talking about.
Sometimes the internet is full of crap. Some people on there even recommend vfc guns...the hive mind is strong in these people.

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