Axial AR60 Gear mesh

[Erik D_lux]

I have posted this a couple of times but I cant find it so I am posting again...

Wheels told me that he ended up breaking a front housing at the modded bearing. He also told me that he thought he messed up his spare housing instantly when he replaced it. On top of that he also told me that he stripped a brand new R&P at the exact same time all this had happened. This didn’t sound right to me so I had to investigate and see what was really going on. Why had he and Doc now broken housings and stripped many R&P when they are the only two to do it and also figure out why we had no problems during testing. What is different?

Kyle brought me the axle and the first thing that popped out to me was that he somehow broke the ring gear bolts. The ring was deflecting away from the pinion making it act like the gear set was stripped. I also noticed that this was causing the pinion to have a TON of in and out play. After I put new screws in to hold the ring gear to the carrier, it still had way too much in and out play. I figured it was the housing. I put it in a brand new housing, still too much play. Maybe it’s the carrier bearing caps? Replaced those, too much play. I put my standard ratio R&P into his housing he was having problems with NICE AND TIGHT. Hmmm. I checked my sporty that also has this mod but runs front overdrive like Wheels does. Mesh looks perfect, pinion has no in and out play.

I had Kyle then bring me all of his failed R&P over and I had a look at them. Here are some pics, these are 3 totally different ring gears.

 

[Erik D_lux]

If you take a good look at them, you will notice that none of them have failed correctly (debatable that they even failed). They all have the top of the tooth shaved off and none of them have wear marks at the root of the tooth showing proper mesh. If you break a R&P that has proper mesh, you should break the teeth off at the root or at least smear the teeth down to that level. ALL OF THE STRENGTH FOUND IN THE R&P WILL BE FOUND AT THE ROOT (which is not being used). This picture shows exactly what I am talking about.

 

[Erik D_lux]

My theory of what is happening is that the pinion is acting like a slide hammer and hammering on the bigger bearing until it finally breaks the housing. The worse your R&P is, the bigger slide hammer that it acts like. Toss in the idea that the ring gear bolts were broken causing more slop, now its even a bigger slide hammer.

Now why did the pinion have too much play (other than the ring gear bolts)?

When we first made these housings we setup a housing at a time, put the gears in and tested the fit. So, what happened is that we tested the fit on the OD gear and it was perfect. Kyle ran this for a long time without issue. He finally broke the housing in half and he went to an off the shelf housing when we made the Ultra trusses. Now he has a housing that was made for a standard ratio instead of a OD ratio and this gives the “in and out” of the pinion making it act as a slide hammer. They have different mesh but Axial only makes one housing……

Once you start taking a look at the R&P, you will notice some decent differences between the ratios. The first one I wanted to take a look at is why the teeth were so much shallower on the OD.

Standard ratio:

 

[Erik D_lux]

OD gears

 

[Erik D_lux]

Actual measurements of each

Standard Ring .174 thick

 

[Erik D_lux]

OD ring .134

 

[Erik D_lux]

The OD gear set is about 1mm shorter tooth than the standard set. Well that’s because the pinion gear is bigger on the OD set, right? Kinda, not really.

Standard pinion:
I guess you would call this the Toe of the pinion approx .320

 

[Erik D_lux]

Heel of the pinion .568

 

[Erik D_lux]

OD gear set:

Toe of the pinion approx .358

 

[Erik D_lux]

Heel of the pinion .572

 

[Erik D_lux]

If you look at the pinions, you will also notice a big difference in the heads. The standard set has the teeth go all the way back and at a constant angle. If you look at the OD set, they do the same right until the middle and then they go flat.

 

[Erik D_lux]

Where they go flat is right where Kyles rings are failing.

 

[Erik D_lux]

Take a look from the back and you will see that the pinions on each gear set have a different mesh

OD

 

[Erik D_lux]

Standard

From my inaccurate measurements, it seems as though the OD gear set uses 1mm worth of tooth mesh where as the standard gear set uses 2mm worth.

 

[Erik D_lux]

From what I am seeing, I think the design of the OD gear set is the problem. I think the proof is in the fact that I can take a brand new housing, put a standard gear set in and its is solid with great mesh but then take the same housing, put the OD gear set it and its sloppy with horrible mesh.

Kyle is going to test standard gears (front), UD gears (rear) along with some different bearings in the housings. I think this will make that front axle truly bulletproof. Really, from my learnings in the 1:1 world, you should be running the lowest gear set possible to save the drive train from strain. If you need more speed, its simple to kick the pinion on the motor up a tooth.

 

[Joshs4x4toyz]

Great explanation. Friends always made fun of me for being the only guy running 5.29s (old yoter days) but when shit went south, id just pop in another 3rd already setup. Theyd have to drop the duals for input shafts :lmao::lmao:. UD FTW

Good info for sure, makes sense with such a drastic difference in diameters when the ring gear especially only has so much room "thumbsup"

 

[mikemcE]

Great read and tech, as always from you!

Thanks Erik


Hang up and Drive

 

[meatmonkey]

I've setup 1:1 ring and opinions, so I understand the importance of proper gear mesh, and am quite OCD about it.

I've installed lots of Axial gearsets, of all three ratios. I feel the underdrives mesh the best. I've also never had an OD gearset that I was completely happy with. Seemed the shimming "window" between too loose and too tight was virtually nonexistent.

I agree the design of the OD gearset is flawed.

 

[Sneetches]

Yeah I've never liked the overdrive mesh, it never felt right to me but I figured I'd just run it anyways and see what happens. My Wraith has been running them for a while but I will definitely check for this next time if I ever take the cover off.

 

[youngblood]

I also haven't run the OD gears in many years because of this issue. I only run UD rear/standard ratio HD front.

On a semi related note I've had the webbing between the two pinion bearings "punch out" half way so that in bench testing the mesh feels fine but under heavy brushless load the pinion pushes away from the ring gear.