Main gear

[flyinfool]

Is there a difference between the Bergen and Xcell one piece black main gear other than the mounting bolt pattern?

I recently striped the bevel portion of my Xcell gear and had a Bergen main gear lying around. The pitch and number of teeth appear to be the same for both the main and bevel portions. So I drilled a new mounting hole pattern and installed it.
The mesh was good, I set it with just the slightest possible amount of backlash.
While I was flying in maximum speed forward flight circuits the main gear striped all of the teeth.
I was able to hit hold and auto with no other damage other than to my nerves.
The gov kept the engine rpm down to just scary.
The engine is a Hanson 3D Max with Hatori exhaust that is just starting to break in and still just a touch on the rich side. (I think)
I am running the stock 6.43 ratio with 700mm blades at 1800
The ship is an old Xcell 1005 very modified set up for 3D.

Is this engine just to much power for the gears or is the Xcell gear made of a stronger material than the Bergen gear?
Or did I miss something else?

[Tom Fiddler]

Can't really answer your question, But I think it's kinda cool you made it fit at all.
Did the main gear or the bevel part strip.
What made the stock gear strip?

[Gary Travis]

They seem to be made out of the same material, I would suspect a mesh problem.
Gary

[cbergen]

Curious as well, which part stripped? The gears are very similar in pitch and teeth, although I believe MA also had a 93 toother available at one time.....

Was this a newer, machined gear, or the older molded gear?

[flyinfool]

It was the older doublesided molded gear.
Side by side it looks identical to the MA gear except for the mounting bolt pattern.
It was the main gear portion that stripped not the bevel part.
The mesh was good with no tight or loose spots.
I set my mesh for just the slightest detectable backlash.

I dont know if it matters but the air temp was around 35°F

Is the delrin main gear that is in the split gear setup going to be stronger.

[cbergen]

Yes, the Delrin machined main gear is stronger, but is less tolerant of heat, such as in a hot clutch bell.

You are correct in that the molded main gear was identical to the MA gear, except for hole pattern. They even came from the same place...

The new machined delrin gear, whether solid or split, was initially tested by sending Malorie out with her gasser with EXPLICIT instructions to shear it. It didn't happen, so we knew we had a winner. Now that's not to say it can't be done, loose mesh, slipping clutch due to oil in the liner or low engine RPM,s causing a hot clutch bell, striking the tail on the ground, will all take it out.

If set properly, it should go for a looong time with no problem.

[flyinfool]

I have ordered a new Delrin main gear from Bergen to try out.
After talking to Chris I hope that this will hold up to the engine power.

[fitenfyr]

One thing to consider is how accurate your holes were drilled.
If they were off a bit then you could have had a poor mesh at one point and after a few minutes of flight it finally took out the teeth on that side then the rest can go in short order.

[cbergen]

I touched on that with Jeff. He says he has access to a machine to accurately put the holes in.

[flyinfool]

When I install a main gear in any heli I check the mesh at many points around the gear to check for loose or tight spots. This gear that failed was one of the most uniform that I have ever installed.

The pinion did not move since I have installed another gear and the mesh with no adjustment was at .001 to .004 backlash from tightest to loosest points.

As an interesting side note the tightest and loosest points are not 180° apart, they are near 90° apart, meaning the gear is not round. I have double checked with a dial indicator and the high and low readings coincide with the tight and loose spots.

Being a molded gear there are a lot of variables that can cause uneven shrinkage of the parts.

I will be curious to see how the machined delrin gear comes out for accuracy on my setup.