Motor RPM losses.

[Iceni]

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

 

 

[Prisce]

I have 13:1 @ 25RPS on an 11.1V , ASG 40K, 348 M100.

 

[Iceni]

There are bigger losses than I would have expected for that motor.

13x25 = 325
325x60 = 19500
=0.48 48% --- 52% speed loss and it's higher than this value because you are running 11.1v.


 

 

[ImTriggerHappy]

There are bigger losses than I would have expected for that motor.

13x25 = 325
325x60 = 19500
=0.48 48% --- 52% speed loss and it's higher than this value because you are running 11.1v.


 

That is because more than just the motor and gearing effects the actual RPM achieved. 

I get what you are trying to do but unless you do tests on the same gearbox with different motors then your results will never be true and even when you have your results they will not be true to the next gearbox.

 

[Iceni]

I'm not after accurate data that can be popped into a spreadsheet and used.

I'm after a basic outline. If the thread gets enough responses, it should prove to do just that. Offer a basic outline of what gearing does, and how to pick a motor to go with that gearing.

 

 

[Sitting Duck]

From memory of std (almost) builds but alas SHORT STROKED 3 teeth

Did a titchy M4 build a while back that I was ultra pleased about

(was it Dan - jeez was along time ago)

13:1, SHS HT probably m115/m120 SS 3 teeth I think

produced about 330fps (Mall safe) at 24 rps 7.4v 25c battery

very thick wire - prob 15awg (needed work to fit in)

pulled about 16 amps I think, I had a Rocket Green to use but somehow the orig SHS had a smidge more zest

(heard some say SHS/Rocket had dropped the tpa/rpm a bit recently from 30k to about 28k

but then this could be just variation from cheapo china lottery slapped together in typical sweat shops)

The SHS HT was a new but say 18 months old unused motor I had to hand - tiny bit better than Green RA

but yeah if done really well (bushings) can just hit 24rps on 7.4v 25c - though was SS 3 teeth mind

Also took 2 x Cyma 517's apart for a giggle & redid them to similar spec

m120 = 396fps so SS 3 teeth, removed piston spacer, AoE guide blah blah blah to get 335fps on 300mm barrel

used cheapo 13:1 set, but a different bevel coz them cheapo BD 13:1's bevels are shit

Used 2 x G&G Blue Powerful Motor's aprox 25k - slightly stronger than stock ferrite - better than std 18k

not as good as orange ifrit but not a bad stock(ish) motor to reuse in budget builds imho

Anyway - rebuilt these exactly the same - one was 330fps & one was a bit lower so flipped irregular spring to get 338 I think

(think I didn't fit v3 bearing spring guides - trust cyma to use v3 in a V2 box as it would push it over 340fps)

just seeing if I could tweak and downgrade cheaply for poops & giggles & test my SS theories n shit

One gun hit 19rps & the other just about touched 20rps now & then - ultra low amps of 12amps when tested

(was very pleased with this low amp draw to rps ratio plus cheapo parts used)

so for a budget build the G&G (quite new & other lightly used) motor did OK in my book for a budget tweak

Now all of these examples were SS 3 teeth so take off a round or two perhaps ???

I really don't know WTF this effects the rps over full stroke blah blah blah

Now these are SS builds, but the final draw/amps/shimming and all the shit that goes with it

makes a HELL OF A DIFFERENCE - if shimmed like shit, loads of stress then you will get heat & poor performance

Those builds are about some of my better ones - can list lots of terrible ones when shit didn't go to plan

but that was things went well for a change & tbh I doubt if I could have got it much better

(without ceramics, faster motor & lots & lots & lots more attention to detail - I did spend a while checking shit at the time)

soz they are SS examples but they are some of my best examples that stick in my mind

 

[Iceni]

Short stroking as far as I can understand just changes the load dynamic of the motor. 

Under regular conditions, the Sector is under load for longer, but it starts out with less load. The total compression energy = 350fps.

Short stroke the cycle gets lumpy. More spring downtime, but the load curve is faster and harder, Same compression energy = 350fps.

With that in mind, I can't see why you would penalise short stroked gearboxes. They do the same work, just in slightly different conditions. And the added spring downtime might make a significant change to the RPS losses.

---------------------
13:1, SHS HT probably m115/m120 SS 3

330fps 24 rps 7.4v

13x24   = 312
312x60 = 18,720/30,000
= 0.62 ,62%, 38% rpm loss.
---------------------
 13:1, 335fps, G&G Blue Powerful Motor's aprox 25k
19rps SS 3 (I assume 7.4v as well)

13x19 = 247
247x60 = 14,820/25,000
= 0.59, 59%, 41% rpm loss.
--------------------

Really interesting results there. That SHS motor with the 38% losses looks to be the best performing so far.

Thank you for the input so far. I still need a lot more information so anyone that knows the RPS of there gun and the motor battery feel free to add your information.
 

 

[Sitting Duck]

Yeah - all on 7.4v 25c inc Cyma's

Dan's M4.....

https://www.facebook.com/video.php?v=1721515051448878

probably fucked now but at time of building - it went well & if he asks about warranty

well it was running alright when I left it

in vid might be at 22rps if using say a 15 or 20c, but I use the 25c 7.4v Zippy Compact and swear it was 24 rps

It was an Asia Gun M4 M7 full metal cheapo GF offer at £85 or something daft

full metal - think it had 8mm bearings but swapped to bushings

used good G&G bronzey bushing for sector coz COL was just catching so easier to file down a smidge

rest was proper steel bushings

https://www.airsoftworld.net/aeg-m7-special-forces-xmas-offer-deal.html

Worth it at silly price and Dan was after a M4 PDW with medium motor or change grip - yeah fuck that

how about this M7 cheapo mofo - he bought the bits, inc green motor I think

which wasn't quite as low amp/sweet as an old orig SHS HT

heard on Airsoft Society they "might" have altered their tpa from say 16 tpa to 18 tpa

which might explain why green RA wasn't quite as good as the older unused SHS - fuck knows

All I know it well (for once) but the cheapy Cyma's with G&G blue ferrite's wasn't far behind in the end too

 

[Iceni]

The ASG U30K is a 16TPA. So it might make the perfect replacement is SHS/RA have adjusted the HT.

It's making some sense to me about what I need if I run off a different gearing.


10:1 15K after losses. -18K franken torque 28tpa
12:1 18K after losses. -22-25K high torque 22-18
13:1 19.5K after losses. -25-30K high torque 18-16
16:1 24K after losses. -30-35K balanced 16-14
18:1 27K after losses. -35K high speed 14
32:1 48K after losses. -40k+ and still wanting more power. 12


It's the losses that have been throwing me for a while, and working out how I can factor them for better motor selection in the future.

I am planning on using this information on a gearbox I'm going to rebuild for the M4. And it's all good asking for an answer. To understand why that answer is given is what I'm trying to factor. I know a lot of trial has gone into this for most people, I'm not the sort of person to trial anything. I want it to drop in, but I also want to be able to tell people in the future why parts were selected, what the method of selection was, and how well it all went together and runs.

 

 

[Sitting Duck]

The ASG U30K is a 16TPA. So it might make the perfect replacement is SHS/RA have adjusted the HT.
 

The only two minor niggles is that ASG is I think " O " pinion

so if pinion wears or needs changing to one that meshes better with bevel

then pinion puller required - or find a better meshing bevel

Slightly more expensive than some places offer SHS from time to time

but ASG/Infinity are respected with alloy end bell etc.....

Watch out if you see SHS HT's on AliExpress for $20 - they are ferrite STD Motors

a few people have been caught out, not moi I've stopped buying peew peew

But a few grabbed these and found out they are just a weak/std motor unlike the pic

Buy from reputable places or triple check out stuff - you won't get a neo motor under $30 really

(OK maybe a neo BD 140/160 @ $29:50 but naaahhhh & avoid & BD M120 = ferrite so double avoid those ones)

But yeah - a 30k motor give or take 5k eg: 25,000 to 35,000 is a decent motor

anything faster is gonna run warm with extra amps

& much slower is unlikely to be needed torque wise for a reg UK 350 gun

(DMR maybe a slower torquey motor on 11.1v)

But yeah around 30k rpm +/- 5k is a good basis to build on, but whatever you can get hold of & works

 

[Iceni]

The only two minor niggles is that ASG is I think " O " pinion

so if pinion wears or needs changing to one that meshes better with bevel

then pinion puller required - or find a better meshing bevel

I've got access to a pinion puller/setter so O-type isn't an issue.

I'm looking at it now in one of 2 ways.

12:1 with the 22K motor for pure trigger response. (I've not built for trigger response at all yet).
Or 13:1 with the 30K to get a better trigger response than anything I currently have and somewhere in the region of 20-25 rps.

I'm actually very tempted by the 12 22 option. It's not going to be out there crazy, but it's going to take some work on the gears and a fair bit of project time to get running nice.

https://www.ak2m4.co.uk/sld-12-1-gears

https://www.fire-support.co.uk/product/ultimate-motor-infinity-cnc-u-22000-long-shafthigh-torque

 

Not the cheapest of setups, but with the required rewire as well it should prove to be an interesting build for me.

 

[Sitting Duck]

I've got access to a pinion puller/setter so O-type isn't an issue.

I'm looking at it now in one of 2 ways.

12:1 with the 22K motor for pure trigger response. (I've not built for trigger response at all yet).
Or 13:1 with the 30K to get a better trigger response than anything I currently have and somewhere in the region of 20-25 rps.

I'm actually very tempted by the 12 22 option. It's not going to be out there crazy, but it's going to take some work on the gears and a fair bit of project time to get running nice.

https://www.ak2m4.co.uk/sld-12-1-gears

https://www.fire-support.co.uk/product/ultimate-motor-infinity-cnc-u-22000-long-shafthigh-torque

 

Not the cheapest of setups, but with the required rewire as well it should prove to be an interesting build for me.

TBH - I don't think it will matter that much if 12:1 or 13:1

I have chucked in both SHS & cheapo BD 13:1 gears - though BD bevel is crap so used std bevel

(whatever meshes nicely and press bevel/pinion up tight to check for 90 degree meshing

so as close as 100% teeth mesh to transfer power nicely - some mesh at 85 or 95 degrees)

30k motor on 13:1 to get into twenties on rps on 7.4v

22tpa or about 22k motor - use for maybe DMR on 11.1v as it is a bit slower or not much quicker than 18k motor

Think most motor spec crap is taken at 8.4v or a fully ultra charged 7.4v LiPo fresh off charge (.5v extra/4.2v per cell)

22tpa will be fine, but might not be as fast, even with 12:1

as said I would be inclined to use a much torquey motor where needed in a DMR or DSG

End of the day it won't matter that much a few rps either way, as long as it runs smooth & cool/low draw etc....

and you ask 10 people what they like/recommend - you'll get half a dozen variations

plus about a dozen or so different parts list of some description & what motor/gears/bushing/ceramics mixture etc....

other crap like piston lightening - not worth it unless you are really sad

Short Stroking - only for shorter guns say 300mm or less as you lose volume & crap

(again only if you are really fucking sad like moi & very bored for poops n giggles)

nah - decent motor, snappy gears and a bit of attention to detail = snappy gun - job done

 

[Iceni]

The orders are in.

Went for the ZCI reinforced 13:1 set and the ASG u30K.

Also got some Stainless bushings, Wire, Mosfet, and a couple of springs to test.

It's a short M4 variant so I think it'll suit the SS3 method, I'll try SS2 first tho and chrono. I think the barrel is about 280mm.

 

[Sitting Duck]

The orders are in.

Went for the ZCI reinforced 13:1 set and the ASG u30K.

Also got some Stainless bushings, Wire, Mosfet, and a couple of springs to test.

It's a short M4 variant so I think it'll suit the SS3 method, I'll try SS2 first tho and chrono. I think the barrel is about 280mm.

Nice

just check the bevel gear's 10 teeth as they are on SOME bevel's a bit thin looking imho

the 16:1 sets I had from China/TinyWind & others like TWG were OK with 6 latches

but 13:1's had 8 latches and rather thinner looking 10 teeth meshing to spur, that I chose to use other bevels instead

The BD/ZCI gear sets are not as chunky as SHS sets if shim space in some boxes is tight

and they run/spin very smoothly, I'd say a whisker smoother than SHS in many boxes

(plus a bit cheaper), so they have some plus points over SHS

The SHS sets are more chunky and plenty of teeth width on the gears - but as been said by many some batches/gen 3 or 4

were better/worse than others with even SHS sets failing the Chinese lottery

a pic says 1,000 words about bevels.......

see how thick/thin the 10 teeth are, obviously treated/tempered manufacturing also matters too blah x 3

check the bevel gear, see what meshes well with ASG pinion.....

hold motor in right hand, place bevel in left hand and press up against pinion with left thumb

(left thumb at bottom/pinion not at top like pic shows - but check in ya hand bare motor/bevel)

check by eye how well the gears mesh at 90 degrees to each other - max teeth meshing together.....

hard to put into words and no real pic to hand but something like this arrangement but in your hands checking....

View attachment 44942

View attachment 44943

not like this.....

View attachment 44944

Though Cyma bevels mesh at like 80 degrees with most pinions (even sluggish 28tpa cyma stock motors/pinions)

but they mesh at 90 with Big Dragon pinions on BD motors I found - weirdness

Just coz a pinion/bevel mesh at 90 exactly still don't mean they roll smoothly, but worth checking angle

then see how they roll together in your hand etc......

This stuff is worth a quick check coz a lot of shrill will come from a poorly matched pinion/bevel, no matter how perfect the rest of box is shimmed & assembled. I mean there are loads of other factors like pistol grip/motor angle blah blah blah

but always worth checking them mofo little gears first beforehand

sounds a nice build going on there sir

 

[Iceni]

Spot on.

I have a few spare 18:1 sets mostly JG and Cyma so If I don't think the ZCI one is up to much I'll swap it out. 

As for the meshing, I have a good few pinion gears as well. SHS, ICS, Star wei, JG, Cyma and APS. So I have a lot to pick from. All are type 0.

It's only a few turns of the screw to get them swapped over.  The last ASG I had meshed very well to a JG set.

It's been a long time coming getting this gun right, I've had it for years and never really used it. I got it in a sorry state and it's never got any better!

It's the GR300 Shorty.

So far it's had the following dropped onto it.

ZCI inner barrel lapped to 0.25 micron.
ZCI plastic rotary hop
New sights, (A&K clones of the originals)
New pistol grip (correct shape for the GR300)
Solid stock (I'm not a fan of the wire stock or crane stocks)
New gearbox (E&C)

And now that gearbox is going to get some treatment to be right.

Should look good when it's all done. It'll be one of those guns that looks completely weird. As I've kept the forend and upper heatshields.

It's also been sprayed nato olive, and given a satin coat on the body and stock.

It's a really well balanced, Lightweight but all metal M4. The G&G magnesium casts are stunning.

 

[ImTriggerHappy]

A really well built box will  get you 22 to 24rps with 18.1 and an ASG 30K firing at 320ish fps.

 

[ak2m4]

Ahhh still love my G&G GR300S, my first rifle.  Back in the day (2003) the stock gearbox didn't make it past the first day lol

Early May I'm getting in a supply of CNC machined bevel's / complete gearsets together with CNC machined pinions from SLD, they really are the nicest set of gears I've seen for the price.  Basically SLD (or whoever is operating the factory) took the SHS design and improved upon the quality massively, from what I've seen they are appearing in new CYMA gearboxes.  

 

[Iceni]

I looked at your SLD set @ak2m4 but you had no stock for the 13:1, or I would have picked that one!

I'll keep an eye on your stock tho and if this works out for me and I like the way the build runs chances are I'll be tweaking my other guns to match in the future.

 

[Iceni]

Update on this build.

The parts I ordered arrived yesterday afternoon from AK2M4.

Stripped the gearbox removed everything.

Degreased the shells.


Enlarged the wire hole on the back side of the box, Cut off the pins that push the wires down on the upper shell.
Removed the bearings - dropped in the bushings.
Deburred and polished the new gears.
SS2 Cut the teeth off nice and polished the scars.
Added a very tight delayer.
Shimmed them to the shells.
Full cylinder and oversized o-ring installed (2.5x20)
Made a new loom, Installed the FET, Sorted the trigger, and dropped the wires into the box. (all that's left is the female crimp connections).
Rebuilt the gearbox and dropped it back in the lower, Lower+stock to check fit.

Literally just waiting for the motor now. Once I get that it's a shim adjustment, Full grease and I should be good to go.

 

[Iceni]

Just had chance to chrono this gun... LMAO.

370fps on 0.25's on 7.4v lipo's at 21rps....

1.6 Joules!!!! With a 2 tooth SS.

Might be a touch hot!

@ak2m4 Do you know what the stock spring is in the E&C gearbox. Because that is what it's pulling.

I'm going to drop in something a little cooler and do the chrono and cut.

Those ASG motors are insane. 1.6J @ 21rps is nuts.