Gear Ratios????

If it has a battery and a gearbox, this is where it belongs

Gear Ratios????

Postby koolaidz83095 on Mon Aug 03, 2009 11:12 pm

Yeah i've never known what they are. I would appreciate it if someone could just tell me the answer to these questions:
1) what they determine about ROF (if they do)
2.)how they affect the gun
3.) if they affect the motor, how so?
4.)and if there is one, which is the best ratio?
Thanks
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Re: Gear Ratios????

Postby GettoPhilosopher on Tue Aug 04, 2009 8:57 am

koolaidz83095 wrote:Yeah i've never known what they are. I would appreciate it if someone could just tell me the answer to these questions:
1) what they determine about ROF (if they do)
2.)how they affect the gun
3.) if they affect the motor, how so?
4.)and if there is one, which is the best ratio?
Thanks


The gear ratio is how many turns of the bevel gear it takes to turn the sector gear. Lower turns = higher ROF. Higher turns = more torque. Think of riding a mountain bike; when going straight up the side of a mountain, you go to a very easy gear; you might have to pedal 20 times just to move a foot, but that's possible. If you're going fast, you go to a harder gear. Now each pedal is moving you 2 feet. It's more strain on your legs, but you go much faster. So there is no "best" ratio; it depends on what you're doing. For a high speed setup, assuming your motor can keep high RPMs with that much load (depending on the ratio and the spring), you want a lower ratio gear. That means that your theoretical 40K high speed motor (these are all made up numbers) that gets a conservative 30K RPMs (due to wiring, battery amperage, and load) on a SP100 spring, for a 16:1 ratio gearset (Guarder and Systema), you've got 30,000 RPMs/16=1875 rounds per minute/60=31.25 RPS. Now that's not exact; most motors don't have good data on their RPMs, nor do most people have the gear to calculate their actual RPMs under load. But you can see that if we had used a Systema Torque set (22.58) instead, we would have been in the ballpark of 22 RPS.

This post has a great chart comparing gear ratios of a ton of different gearsets. http://forums.airsoftmechanics.com/inde ... pic=1208.0

This post is a great in-depth discussion of gear ratios and ROF.
http://www.airsoftmechanics.com/home/co ... iew/17/26/
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Re: Gear Ratios????

Postby koolaidz83095 on Tue Aug 04, 2009 1:29 pm

http://www.airsoftgi.com/product_info.p ... ts_id=5335
so like how the ratio for the gears listed above is 16:32:1 that means the bevel gear spins 16 times and the spur gear spins 32 times to make one revolution of the sector gear? if that's correct i think i got it. but if not, please correct me
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Re: Gear Ratios????

Postby GettoPhilosopher on Tue Aug 04, 2009 2:03 pm

Look closer. It says 16 [POINT] 32, not 16 [COLON] 32.

So 16.32 motor revolutions per sector revolution. The per gear ratio would be different.

From the AirsoftMechanics article I linked:

"Bevel to Motor Pinion Ratio: 30:10 = 3:1
Spur to Bevel Ratio: 39:10 = 3.9:1
Sector to Spur Ratio: = 32:20 = 1.6:1
Final Ratio = 3 x 3.9 x 1.6 = 18.72"

All that to say, 16.32 motor revolutions per completed firing cycle. Now this seems very predictable and straightforward, but in real life it gets messy. See, most motors don't have good information out there as to their unladen RPMs, let alone graphing of their RPMs at different loads. So even were I to know for a fact that my G&P M160 is rated at--I'm using made up numbers, I can't actually find RPM data on the M160s--25,000 RPMs and my gearset is a 18:1 ratio, that doesn't mean I'm going to get 23 RPS. See, the production motor I'm holding in my hands probably isn't spinning at exactly the rated 25,000 RPMs, and I can't know how big the discrepancy is. My wiring/trigger/battery combo may have too little amperage and voltage and too much resistance to give full power to the motor. And even were those not true, the more load the system has--both from the spring, the weight of the piston assembly, and even the friction in the gearbox including the rails and the bushings/bearings--the slower it goes. So I can't know exactly what my ROF will be.

However, I can do something useful. Assuming my gun isn't overstressed (for instance, with a G&P M160 or a Systema Magnum or another high torque/high speed motor I don't have to worry about a M110 or M120 spring being too stiff for a HS gearset), I can use the ratios to compare how much of a gain or loss I'll get by changing gearsets. If I'm getting 21 RPS in an 18.72:1 ratio Systema genuine gearset....
(21*60) = RPMs/18.72, RPMs = (1260)18.72 = approx 23,587.2 effective RPMs. So if I go to a Systema high speed gearset at 16.46, I can expect RPS in the ballpark range of 23587.2/16.46 = 1433 RPM = 23.8/24 RPS range. A Systema Super High Speed at 15.5 would net me around 25.36 RPS...and so on.

That help, or did I just ramble on for no reason? ;-)

Kids, do your Algebra! :-D
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Re: Gear Ratios????

Postby koolaidz83095 on Tue Aug 04, 2009 8:32 pm

it helped thanks. my eyes hurt, but that's okay. thanks
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