Another Motor adjustment technique

[Spa]

I was jsut reading a small sheet by systema on how to adjust a motor. Systema said that their was to fit a motor in properly with a bevel gear is to put nothing in the gearbox except the bevel gear and attach the motor and then adjust it till theres no more noise.

So, I'm used to just putting everything together and shooting the gun off till i think its sounds good, that generally works but I want to know the best way.

So i tried the new systema method; After adjusting the the motor the sound is really smooth. After looking at how the gears interact on to why it sounds so smooth, the bevel gear is not completely all the way in...maybe 3/4 of the pinion gear is actually interacting with the bevel gear. Is this correct or should the whole pinion gear be inserted with the bevel gear?

I am wondering because when the whole pinion gear is touching, but (not all the way in pressed against the bevel) there is alot of sound but when 3/4 of the way touching it makes perfect sound.

Then, I am concerned that the pinion gear is now having to do more power to turn the gears because it is not 100% touching.

So my question is, Does the pinion gear have to be 100% touching the bevel gear to have 100% efficiency?

Thank you for the input,

Spa

[m102404]

LOL...funny, I've been wondering the same thing lately...

I've been troubleshooting a couple of sets of gears that should work/sound fine...but for some reason...just don't. They turn/crank/etc...but they sound horrible.

I ended up leaving the bevel gear shimmed a little loose, and the pinion gear of the motor indexes into place.

I'm using class-a parts (systema/guarder/eg1000 motors, systema/modify gears sets).

There's still 100% tooth contact between the bevel gear and the spur gear, not sure about the pinion/bevel contact.

I have noticed on a lot of worn pinion gears that the wear tends to be on 4/5ths of it (from tip back to motor)...and there's usually a bit of the tooth, at the widest part of the gear, that doesn't seem to have much, if any, wear at all. Sometimes just a little lip...sometimes a bit more.

I figure that it's still going to impart the same force/torque to the rest of the gear train...but the strain will be more focused on a smaller tooth section of contact. So same power, but increase stress and thus increase risk of part failure.

I've always adjusted the motor with the complete gear-set installed. I've shimmed each gear separately at times...but never just adjusted the motor with only the bevel gear. I'll have to try that. I suppose that if your bevel gear is set too low and is rubbing the mechbox or the spur gear...you'd have to readjust the motor anyways....

[Spa]

Try doing that with helical gears, you cant really have a loose bevel with helicals or the teeth might get screwed Im already starting to see some wear on my sector gears helical teeth.

But, let see what others have to say

[Flatlander]

Originally Posted by Spa

So my question is, Does the pinion gear have to be 100% touch the bevel gear to have 100% efficiency?

Spa

First off you can never achieve 100% efficiency

Secondly, yes and no to your question...but more of a no and opposite what you think!

- Less tooth contact means less friction; therefore less energy lost due to friction, therefore higher efficiency.

That amount of energy difference is probably so small it would be difficult to even measure accurately! So don't worry about that. What you need to worry about is:

- Less tooth contact means more force (or torque, however you want to look at it) transmitted through less material. Which means you will have more stress on your pinion gear.

So in closing...I'm not entirely sure! What I do is generally by sound and try to have as much contact between the gears but still maintaining the "clean and crisp" sound. I've yet to strip a pinion on any of my guns or any guns that I've worked on. I've even seen some pretty beat up pinions (from improper intallation/use) keep going strong for thousands of rounds...and are still going actually.

[m102404]

Well...helicals are different, yes. I'm sorry, I thought you were referring to "regular" gears.

[Spa]

Your right, now that i think about it, when i opened up a 249 mechbox, the pinion gear is actually touching perfectly [back of the pinion tooth lines up with the end of the bevel gear].

So like Flatlander said, there should be more tooth contact to cause less material failure.

So in conclusion, I guess the systema method either has a flaw or i just did it wrong And make sure the pinion gear teeth are fully touching the bevel gear

Well...helicals are different, yes. I'm sorry, I thought you were referring to "regular" gears.

If these helicas break im never going back to them, I will just purchase Torque gears, BB's per second means nothing, gearbox stability > anything else.

[Flatlander]

Side note on gears in general:

(So far) I don't trust anything but standard ratio gears. Reason:

- The tooth profile is VERY important in geartrains. They must be properly designed/chosen and consistent on each gear.

- The axle placements do NOT change on the mechbox, but the number of teeth change on torque/high speed gears so they have to change something...the profile of the teeth!

The reason I don't touch them is because I worked on a buddy's gun who put in system high speed gears. The profile of the spur gear teeth were like little sharp triangles. Only after a few thousand rounds I saw significant wear on the spur gear and so I changed those out immediately.

I've had great success so far with standard ratio gears. I've seen an 8.4v mini pull an m120 spring so I see no need for high torque gearsets. If I want more ROF I just up the voltage on the battery.

[Spa]

Good call Flatlander Let that be a lesson to everyone!

I said torque gears b/c I put CA High Torque gears in my 249 and that gun has put in over 80,000 rounds and the gears still look brand new. just my 2 cents and with standard ratio gears ive seen teeth break off, but thats probably b/c they were not shimmed right or were jsut of poor quality

[Kos-Mos]

The way you are shiming your gears can make a difference.

I usually try to have the smallest shim possible behind the "large" section of the bevel, then work from there on.

That allows the motor pinion to go further in contact with the bevel gear, since the gear is pushed to the side a little more.

Acheiving the "Perferct" shimming/motor adjustment could take a while, and it would be different on every gearbox/motor/gear/bushings/motor cage combo.

We don't need perfection to have the mechbox working properly. Just close to perfect is enought.

Look at the surface of gear between the spur gear and sector gear. Don't you think that it is a LOT less than between the bevel/motor pinion? Well, that is the link that takes the most load (except between piston/sector). If that does not break, the chances that a properly adjusted motor breaks a pinion are quite small. It does not really matter if all the pinion is in contact. even 1/2 would probably be enought.

[damage]

There is a way to properly shim bevel gear to minimize gear noise. You have to find which side the right shims go untill you hit the sweet spot. A monkey can install spring, piston etc. upgrades but not shimming. It takes a lot of patience and practice to master the art shimming.

Anyways you get different advices in this forum on "how to's" but everyone have a different ways but not technique.