Gear ratios

[Airsoft-Ed]

I feel like I've not started a new topic for ages, you've no doubt all forgotten how long they tended to be...

But anyway, since I was just doing some techie shiz, I thought I'd voice my thoughts about what I encountered.

 

I bought an Madbull M150 spring the other day with the intention of fitting it in my LSW to make a DMR.

 

As you probably all know I have an L85 already, which is still running with the stock gears and a Systema high torque motor.

 

The LSW was also fitted with stock gears, and ICS' Turbo 3000 motor, which are supposedly exceptionally good, and also intended to provide high torque.

 

As a general observation, the Systema motor is massively more powerful and with the stock gears and a 9.9v LiFe battery I can easily break 20rps. With the Turbo 3000 linked to the same gearbox it's somewhere between 15 and 20rps, though I suspect the higher the tension spring you use, the larger this gap would become apparent.

 

Now, a few months back, I bought some high torque gears for this very occasion, high torque gears, high torque motor, high tension spring, it sounds like a match made in heaven. So I matched them up all in the same gearbox.

 

This is where it gets physics breaky.

One would assume that with high torque gears and a high torque motor the gearbox ought to easily be able to pull back this spring, I'm fairly sure the Systema motor I have is one of, if not the most powerful motor on the market, and the gears I have are rated to M180 springs, which are massively higher tension than the M150 I have.

So I fitted the M150 to my L85's gearbox as I've been using it, Systema motor, stock gears - Result? Yeah. It worked pretty well, pretty decent trigger response and speed on single shot, though it's very prone to jamming if you go mad with it. The ROF on full auto was actually staggering considering the amount of force all the parts were being held under, it sounded around the 10-15 mark and very ridiculously loud.

 

So at this point I was sat thinking, "When I fit these high torque gears, this thing is going to be a beast" so I fitted them aaannnnndddd... Meh! The gun sucks. ROF dropped to about 5rps, single shot doesn't work, it's horrendous.

So it got me thinking; the high torque gears I have are a 1:26 ratio, which I assume means that for every 26 turns of the motor, the gearbox will turn over once, right? Correct me if I'm wrong.

 

Kinda like with a bike's gears. The lower the gear you're in, the higher the gear ratio, meaning you have to pedal more to go less distance, but for less effort.

 

The less effort thing, being the part I bought the gears for. I thought if the gearbox could turn the spring over with less effort, I could afford to take the drop in ROF.

But having fitted everything, the gun acts and sounds as though it's taking a lot more effort...

 

The stock gears are a 1:18 ratio, so that means the gearbox as it comes, can turn everything over at almost double the speed.

 

So to sum this all up, why would anyone ever use high torque gears? Less stress on the gearbox? Yeah, I get that. But if you're playing the DMR role and you're locked on semi, you can't afford to have bad trigger response, because if you jam up, you're screwed. High torque gears by their very nature, via their ratios, increase the chance of locking up occurring... So they just seem like a bad choice, for everything.

 

High speed gears I assume bring the ratio down below 18, I've not looked but maybe they go down to something like 1:10?

 

What sort of set up would ever benefit from having 1:26, if it could have 1:18 or less?

 

All I can say is that I'm glad the mad expensive Systema high torque gears were out of stock when I was looking for some, otherwise I'd have bought them instead and been even more out of pocket.

[sp00n]

thinking about it, i would say to get some where similar rof wise you would have to use a high speed motor with the high torque gears, let the gears deal with the torque to lower the load on the motor.

[Ian_Gere]

Yeah Sp00n, I think that's the right idea.

 

I think the high speed gear ratio is 1:13.

 

I've a feeling that what's happened here, Ed, is that you've fallen foul of having excellent parts. Your motors can pull a 150 spring without any help from high torque gears. If you had a crap motor, perhaps it wouldn't work at all with 1:18 gears.

 

Dunno why it doesn't work on semi at all though. I'd expect it to just be slow. This makes me wonder if there's something going drastically wrong. I'm not convinced that all airsoft gears and/or gearbox shells are manufactured within sufficiently tight tolerances to be truly interchangeable. I don't think it matters so much at lower spring tensions, but I think that the angles between them may cause the teeth to jam into each other at higher tension. Like maybe the angle between the surface of a tooth and a radius of the gear it meshes with is too shallow...

 

I'm running out of understanding of mechanical engineering here, but I think it has something to do with the efficiency of energy transfer from one gear to the next and how that relates to how much pressure is on the teeth at any given moment; Tariq mate...?

[Airsoft-Ed]

I might buy some high speed gears and a high speed motor and try various different combinations, see which works best.

 

When I can be arsed and have money to burn, anyway.

 

I was kinda hoping there'd be more people on the forums that were a bit more mechanically minded, someone else must've encountered this issue before.

 

I'm immensely impressed that a gearbox filled entirely with stock parts and using a stock motor can even pull an M150, ICS are gods.

[Ian_Gere]

Yeah, I just wish I could get mine to break down, but it's either seized or perhaps some cock who had it before me used glue on it or something! I've got a Systema bucking and Guarder 6.02mm barrel sat waiting to go in it and I reckon it'll be about as good as a 74U can be...

 

IF I CAN GET THE POXY THING APART GRRRRRRRRRRRRRRRR!

[sp00n]

so what you are after is a setup that will pull a m150 spring at a similar ROF as your L85

 

some basics :-

high torque motor will not spin as fast as a high speed motor

high torque gears will not output as fast as high speed gears

OEM gears and motors are a balance between power consumption, speed, torque, and cost

 

well you have a few options as i see it.

 

1) standard gearing (not necessarily the OEM gears) and a high torque motor

-will work but your rof might be slower then standard due to the possibility that the high torque motor may be slower than standard

-will consume less power than a standard motor in the same setup (as the high torque motor is designed for this)

 

2)high torque gears with standard motor

-will work but your rof will be slower due to the slower cycle time of the gearing

-standard motor power consumption

 

3)high torque gears high torque motor

-will work but will be the slowest rof as the motor spins slower and the gearing output will be slower too

-lower than a high torque on its own, as the motor is not having to do alot of work

 

4)high torque gears high speed motor

- "should" work rof should be similar to standard

-medium power consumption

 

personally i would be tempted to go with number 1 as you know it works (maybe get some gears that are a little tougher though to cope with the increased stress), you could try high speed gears with a high torque motor, but it would be the same as 4.

[Ian_Gere]

I don't think high torque motors do use less power, Sp00n. I think they work by drawing more current through shorter coils so that the spindle spins slower but with more turning force, or torque.

[sp00n]

I don't think high torque motors do use less power, Sp00n. I think they work by drawing more current through shorter coils so that the spindle spins slower but with more turning force, or torque.

while this is 100% true, if the motor dosnt need to produce soo much torque to do the same amount of work, it will use up less power

 

Edit :- i have edited my last post to reflect this as it wasn't obvious

[Airsoft-Ed]

The OEM gears are probably better than most other standard gear sets available, the motor has already shredded itself against them and there's not a mark on them lol. Suggests ICS are better than Systema, and about half the price.

I think option 4 sounds the best, I feel that's the most likely to work.

 

Of all the combinations I've been able to try, if the set up isn't rigged for ROF, then the gearbox locks up just before the piston is released on semi auto. I can only use the gun if it's on auto.

 

Due to the trigger and fire selector design, I'll also have to figure out a way to semi lock the gun before it'll be skirmish legal anyway, and I could do with a chrono.

 

For some reason the LSW performs generally worse than the L85, even with my gearbox in it. It's like there's an air leak somewhere, or a build up of friction. The BBs seen to come out of it significantly, visibly slower than with my L85 and the range isn't up to much either, even with the M150 fitted, which by eye I would say isn't even giving me 400fps. I can't quite figure it out.

 

But I'm going to try my best to, and once I do I ought to be able to make a pretty epic DMR out of it. My L85 was spitting .43s at least 60m, only issue was that I couldn't see them because they're black...

[JRTIGHE]

Ed, why would you want to make a DMR out of a support gun? Seems a bit heavy to carry around just for single shot? Just interested.

[TPI]

Because it was designed as a Light Support Weapon not a Light Automatic Weapon (we unlike the Septic's don't need Volume of fire to hit the Broad side of a Barn)

[JRTIGHE]

It may have been designed that way for real world military use, but I'm just wondering if in airsoft terms it's worth the firepower to weight/maneuverability ratio?

[sp00n]

i have heard a whisper that current LSW's are being retro fitted for 7.62 and could be used as a stop gap DMR role ......... i could be wrong though

[jcheeseright]

You are wrong, the L129A1 has been brought in to cover the 7.62mm gap and the LSW is still being used by many units with a standard SA80 mag as it's increased barrel length provides better range and accuracy than a standard SA80.

 

Using the LSW as a DMR style weapon entirely fits with it's regular role in theatre these days.

[sp00n]

back to the subject at hand i found this >>> http://www.airsoft-obsessed.com/airsoft-aeg.html

 

might be helpful

[Airsoft-Ed]

Ed, why would you want to make a DMR out of a support gun? Seems a bit heavy to carry around just for single shot? Just interested.

As other's have said, the LSW ended up being used more as a DMR than a machine gun, mainly because you can't put down large volumes of fire with only 30 shot detachable box magazines. The LSW is also accurate out to 600m+ so it made sense to use it more as a precision weapon than a spray and pray style one. That's all in real life, of course. But that's what I'm about. If the real rifle is used as a DMR, that's how I'm going to use it. I don't think it looks like much of a machine gun anyway.

 

As for the weight and mobility issues, have you not seen my kit? Lol.

 

My L85 weighs in the region of 5-6kg, including my rig, helmet, knee pads etc etc. I'm carrying upwards of 20kg about with me. An LSW is going to make me lighter than I am now, if anything. I'll not need as much ammo as my reach will be extended, so that's less weight in mags. Plus the gun is actually lighter than my L85 because it doesn't have RIS fitted to it.

 

Additionally, the sniper rifle I do have, weighs about 7kg, it's stupidly heavy and really is only good for that one shot. An LSW is at least semi automatic at worst, and full auto at best so it's just a big win all around. Or it will be once it starts shooting as it's supposed to.

[Ian_Gere]

I tried out the DMR role first when I had very little experience. I expect that with a lot of practice I could learn to reload a spring sniper rifle and still remain on-target, but my 425FPS semi-auto L1A1 is so easy to use to pick people off at range. When the bitch is working of course... Ares £400... what can you do?

 

I'm owed some money so when I get that I'm gonna send it to the original supplier for a service.

[monkee]

I got a little confused throughout this thread, are you looking for a good ROF or good range and accuracy on semi?

 

If you want range and accuracy, then you want to work on getting your cylinder compression as tight as possible and of course tightbore barrels, etc (you probably know that bit right?).

 

If your looking for a bit of both (ROF and range/accuracy) then its all about high torque motors and high-speed(ish) gear sets. I currently run a 16:1 gear set with a high-torque motor - team this up with active braking mosfet and an 11.1 lipo, I get around 20/25 RPS and a good 50 metre accuracy. I can spam semi all day long with this setup which is why I don't even bother switching to full auto anymore. The mosfet stops gear sets over-running, giving a snappy semi trigger response. On a 1joule spring, I come in around 340fps on 0.25's.

 

Its worth mentioning that to withstand the beating from an 11.1 lipo, everything else will need upgrading as well otherwise you'll be shredding through pistons every couple of weeks.

[Airsoft-Ed]

I'm looking for decent ROF/trigger response with a very high tension spring. I don't really have a goal or an aim, per-se, I'd just like to max out the gun's potential and test its limits to the max.

 

I know more or less everything there is to know, I'm not here looking for advice. I just found it surprising that high torque gears coupled with a high torque motor gave worse performance than a high torque motor with standard gears. I was just putting the info out there and seeing what people had to say about it, I didn't specifically ask anyone to detail a perfect DMR build for me anywhere, or anything.

But yeah, the ICS L85 gearbox really doesn't need upgrading to take an 11.1v LiPo, it's built better than a nuclear bomb shelter. I've heard reports of them breaking 40rps before the piston stripped, I imagine it'd be possible to get them up to around 60 and running quite nicely if you could be arsed to put the effort in.

 

Also, as I've said above, the gearbox can pull an M150 as it comes, how many other gearboxes can manage that?

 

I will have to look into the mosfet idea, obviously I'm aware of them, but I'm not sure how to go about wiring one up, as the ICS L85 has a unique switch assembly and it's largely mechanical. I'm not sure if fitting an active braking mosfet is actually possible.

[sp00n]

diy basic mosfet >>> http://unconventional-airsoft.com/2009/08/26/how-to-make-a-basic-mosfet-switch/

diy basic and active breaking mosfet >>>http://www.airsoftforum.com/board/MOSFETS-t196370.html

 

i am just doing the basic one as i am lead to believe active braking can cause brush wear and excessive heat build up due to the back EMF

i know braking of industrial motors can cause excessive heat buildup, and component wear if not spec'ed correctly.

 

(Edit :- i have all/most of the bits, i am waiting till next pay day so i can spec a battery/wire/connectors etc)