Motor RPM losses.

[IntelligentCelestialBeing]

On 20/04/2019 at 23:21, Iceni said:

I was thinking about motor rpm losses for various configurations and there is a lack of any information on the net.

It's a pretty basic concept that the no-load speed V/s the load speed is going to differ. Motor speeds, however, are not a unified value. 

At the most basic level, motor speeds never tell you the rated voltage for that speed. We all know that putting more voltage into a motor increases the speed, What we don't know is what the voltage was set at when the motor was tested.

A simple example would be a 20K motor, but the test voltage was 20v. Because the voltage was set so high getting an AEG to use that 20K speed is never going to happen.

What I'm hoping is people can chime in with real-world values for motors,  mainspring or FPS, gears and batteries and the resultant RPM.

All variables are important.

Motor brand and model gives us a reference to the sales RPM.

Gears, mainspring/fps and battery let us see the system.

RPM tells us the total losses to the system.


For example one of my own guns:


18:1 gears @24rpm.
It shoots at 345fps on a cut M110.
The motor is an ASG ultimate 35K.
7.4v lipo.

From that you can work out:

18x24 = 432 revolutions per second on the gearbox.
432 x 60 = 25,920 rpm motors actual running speed.

25,920/35000 = 0.74, Or 74% meaning a 26% drop in speed at 345fps.



---------------

18:1 @ 20rps
325fps M100
SHS high speed 30K ish
7.4v lipo

18x20 =  360
360x60 = 21,600

21,600/30,000 = 0.72, 72%, 28% speed loss at 325fps.



What I really want to see is how the losses are affected by gearing, So people running 12, 13, 16, 32 :1 gearsets if you can provide those details I'd be very happy if you could post your numbers. Without complete details I can't work the losses out. Many thanks.

@Sitting Duck

 

 

 

Please do correct me if im wrong. But from what I understand is that you want to see if your mathematics for calculating losses to RPMs after a load is put onto the motor is correct ? 

 

Cant you test your results with a spectre fet? Im sure you can purchase a Bluetooth spectre fet which gives you infotmation about the RPMs of your weapon system. Surely then can see how accurate your results are and surely you can get more accurate results but putting the information you get from the spectre fet upagainst rpms of a motor without the load.

 

i could have misunderstood you and i could also be wrong. But from my knowledge a spectre fet tells you details of your rifles performance on your smartphone and if this is the case it would tell you your rifles performance when the load is put onto the motor. So using that info and putting it up against the info of the rpms on the motor when no load is on it you can come up with a more accurate percentage of losses and you can also see if your mathematics make a good basic outline for losses to a system 

 

just thinking out load 😊

[Iceni]

3 hours ago, IntelligentCelestialBeing said:

Please do correct me if im wrong. But from what I understand is that you want to see if your mathematics for calculating losses to RPMs after a load is put onto the motor is correct ?

The math is only a part of it.

What I actually wanted to know was the correct way to select a motor for a particular gearing. How brands or motor differ in efficiency, and what the total losses would look like in a real world gearbox.

The math is actually just a method of comparison, so I can see the differences in the builds. It is in no way a method to estimate losses as a gearbox build can significantly alter how well a motor performs. The % mark is just a reference, It can't be used to make an estimate of an unknown motor.

The results are only really applicable to someone that can build a gearbox to the standards of the people that posted. I'm pretty confident my gearbox rebuilding is close to Prisce and SittingDuck standards. Your mileage may vary as there are a lot of variables in gearbox rebuilding, and friction can have a significant effect on speeds. As too can a poor airseal, As some guns run @350fps with poor seals, but the gearbox does a lot more work, with greater losses and lower consistency to get there.



 

 

3 hours ago, IntelligentCelestialBeing said:

Cant you test your results with a spectre fet? Im sure you can purchase a Bluetooth spectre fet which gives you infotmation about the RPMs of your weapon system. Surely then can see how accurate your results are and surely you can get more accurate results but putting the information you get from the spectre fet upagainst rpms of a motor without the load.

Most Chrono's can do RPS. It's just a case of shooting a burst through one. There's no need to have a special fet to be able to test this. If you ask the marshal when you chrono before game they might let you check the RPS.

It's also only the loaded speed I was interested in. The no-load speed is irrelevant as we always have load on the gearboxes. How much load is also important hence the FPS request as well.


The question you ask is often more important than the results. I could of asked what motor is best for a 13:1 gearset? More people would of had an opinion, but I would still not be in a situation to make an educated choice for myself. Asking a different question stopped the answers been I have X it works well.

 

Imtriggerhappy was spot on with his assessment of the question been pointless. It is. There are no rules that can give a solid formula to work out losses.

 

[ImTriggerHappy]

43 minutes ago, Iceni said:

 

Imtriggerhappy was spot on with his assessment of the question been pointless. It is. There are no rules that can give a solid formula to work out losses.

 

That is because I have many an hour staring at a gun I just built wondering where those numbers came from.

 

I built 12 identical G&P guns a while ago changed everything internally just kept the receivers. They all had identical parts and were built exactly the same but each one threw out different numbers. Only a small difference gun to gun but across all 12 a huge difference.

Only reason that could be is airsoft parts tolerances are sketchy at best so even from the same manufacturer there are differences.

 

@IntelligentCelestialBeing if you interested in high end fet/etu combos forget the Spectre and get a Titan.

[IntelligentCelestialBeing]

7 hours ago, Iceni said:

The math is only a part of it.

What I actually wanted to know was the correct way to select a motor for a particular gearing. How brands or motor differ in efficiency, and what the total losses would look like in a real world gearbox.

The math is actually just a method of comparison, so I can see the differences in the builds. It is in no way a method to estimate losses as a gearbox build can significantly alter how well a motor performs. The % mark is just a reference, It can't be used to make an estimate of an unknown motor.

The results are only really applicable to someone that can build a gearbox to the standards of the people that posted. I'm pretty confident my gearbox rebuilding is close to Prisce and SittingDuck standards. Your mileage may vary as there are a lot of variables in gearbox rebuilding, and friction can have a significant effect on speeds. As too can a poor airseal, As some guns run @350fps with poor seals, but the gearbox does a lot more work, with greater losses and lower consistency to get there.



 

 

Most Chrono's can do RPS. It's just a case of shooting a burst through one. There's no need to have a special fet to be able to test this. If you ask the marshal when you chrono before game they might let you check the RPS.

It's also only the loaded speed I was interested in. The no-load speed is irrelevant as we always have load on the gearboxes. How much load is also important hence the FPS request as well.


The question you ask is often more important than the results. I could of asked what motor is best for a 13:1 gearset? More people would of had an opinion, but I would still not be in a situation to make an educated choice for myself. Asking a different question stopped the answers been I have X it works well.

 

Imtriggerhappy was spot on with his assessment of the question been pointless. It is. There are no rules that can give a solid formula to work out losses.

 

 

 

Thanks for clearing it up 👍🏻

[Sabret00th]

Hi there everyone!

Interesting thread here.

I have a noob question.

I bought a

https://www.airsoftstation.com/g-g-top-tech-raider-xl-ris-electric-blowback-metal-airsoft-rifle/

18:1 V2 gearbox and M100 sprint inside and 11.1V lipo.

I wanted to tune it for more precision and reach. Its upgraded with Dean connectors now.

I bought an ASG u-35000 motor.

What spring do you guys recommend, and do I have to touch the gear ratio?

I'm as said for precision and power, but ofc I want the internals to last and get some nice trigger response. I will do all the things like radiusing, sorbo and so on ofc but this gear ratio and spring thing is giving me headache's. 500 fps limit, so no worries about it being to strong.

Thanks in advance