Metal Spur Gear?

[Powerman6766]

I finally took my Savage 25 apart to fix the spur gear because it was slipping.I found out that the center of the spur gear melted, and the slipper clutch pad was stuck to it.We went and purchase a new spur gear and it brought up the question of a metal spur gear, because it wouldn't melt like the plastic one.Anyways back to the question, what are the advantages and disadvantages of getting a metal spur gear.I want to know like does it get hot, does it melt, will the teeth ever be stripped of of it, and things like that.

Thanks,
Powerman6766

 

[olds97_lss]

It doesn't give you much of a weak point in the drivetrain. It's always easier to fix a spur than it is to fix a gear in the trans, a blown diff or a broken cvd. It also adds rotational mass which means the truck will be a little sluggish on take off. This is more noticeable on smaller trucks with smaller engines, but I'm sure it's still noticable.

So, IMO
Cons:
rotational mass - slower spool up
no weak point
gear mesh must be set more accurately
new CB will be needed as stock are soft and will wear out quickly
costs a lot

Pro:
Lasts longer
rotational mass adds inertia to the drivetrain (more torque once in motion)

That's about all I can think of, but that's just IME with a maxx. I left the savage with plastic and haven't chewed one up yet in a gallon.

 

[SkyMaxx]

Pros:
- Strength
- Rotational mass increase means that you do not need to lean on the throttle as much once it is up to speed in order to maintain that top speed.

Cons:
- If gear mesh goes, the damage to the drive train in the vicinity of the engine is much more costly.
- Rotational mass increase means it takes a little bit more time to spin up...but once its going...good things.

Other:
- Gear mesh becomes super critical. Your set-up needs to be just right otherwise you could have some serious issues.
- Hardened steel clutch bell is a must.
- Did I mention the mesh?

I ran steel spur gears on my T-Maxx to great effect. Once in place, I never had to replace it. I did, however, make a ritual of pre-run checking my engine and gear mesh to make certain everything was tightened down the way it should be.

If you have no problem with that, then you should be able to switch from plastic without too much cause for concern. As Olds mentioned, you do have the cost consideration. Replacing a plastic spur every now and again might be more cost effective in the event that you screw up.

 

[Kodama]

Does anyone have any tips for getting the gear mesh down right with the metal spur gear? I use the sliver of paper thing and I've had minimal trouble with that but I stripped my clutch recently and had to replace it, and now it's starting to eat it again. I pushed the engine over as far and as hard as I could to get the gear mesh tighter but it just didn't work...

 

[SkyMaxx]

Here is how I do my mesh...

Originally posted by SkyMaxx
Setting gear mesh is very important to the longevity of both gears and the components driving and being driven by the gears.

Here's how to do the mesh check.
1. Loosen the screws that hold the motor mounts to the chassis plate (don't take them all the way out).

2. Make sure you have both spur gear and clutch gear on properly (since you've mounted the spur and the clutch is attached to the motor, you probably have little to worry about here).

3. Take the plastic bag that the spur gear came in (a ziploc bag will work just as well) and place one thickness of the plastic between the two gears.

4. Push the motor back into place so that the two gear compress on the plastic.

5. Tighten the motor mount screws (making sure that the motor mounts are as square to the chassis as possible...you want the gears to have as even a surface to surface contact as possible).

6. Pull the bag out. The gears should rotate freely and mesh together just right.

Hope this helps...

Beyond that liberal use of loctite on engine mount screws and making certain things are nice and squared up when you are complete should help keep the mesh snug.

After that, the only thing that can defeat your set up is chassis flex.

 

[Powerman6766]

Ok thanks for the help guys...think I am going to stick with the plastic one.Seems like it is less expensive and less work in the long run.

 

[olds97_lss]

I adjust mine by feel. I've been around gears and machines where gear mesh was crucial for quite some time. Having gear mesh to tight is worse than having it too loose. To loose, you strip teeth, big whoop. To tight, you melt gears, eat up bearings and put unneeded stress on the engine as well.

Basically, I do what Sky mentioned, but without the bag. I get the gears meshed together and squared up with the engine plate screws relatively tight by gently tapping on the engine mount with a blunt punch and light hammer. Then I gently tap it back until the gears spin smoothly and I have about 1mm of play when rocking the spur back and forth with the clutchbell being held stationary.

Doing it this way has made my gears last a good long time. The only times I've stripped a spur is when an engine mount bolt rattles out or a hard landing brakes the engine mount all together. Like I said, the one in my savage has been in it for about a gallon and it shows minimal wear. The one in my maxx has been in it for about a gallon as well.