adamnyholt

I've built a ramp for my XXl2/e and I'm getting the hang of controlling my vehicle angle by throttling and braking. I can land on my feet most of the time, and even do forward and backward flips. However since working on my ramp skills I've busted both my front and rear differentials.

What am I doing wrong? I'm assuming it has to do with landing hard and stopping too suddenly, transferring that energy into the gears and busting them. Do I just need to work on my landings? Or would I benefit from adjusting the slipper clutch to have a little more give?

Thanks!

Billy Kelly

iTrader: (9)

It’s kinda part of the hobby. I’m not familiar with that truck. There are a number of reasons for diffs to break/strip out. It’s not usually just a single bad landing. But it can happen. Land with throttle or brakes in wrong, tooth break on ring or pinion. A lot of the time it’s just the repeated force of impacts from landing. Diff housing flex’s a bit.

billdelong

iTrader: (33)

Which part of the diff is breaking?

Are you stripping gears? If so then maybe you need to properly set your mesh?

Are you snapping out drives? If so then maybe you have too much droop and/or have too much plunge with your drive shafts binding into the cups?

What is the condition of your out drives? Are there any pitted notches from the pins digging into the blades? Then they need to be replaced, this can be prevented if you regularly replace the pins on your shafts, the first hint of any flat spot on the pins and then you need to rotate the shafts to the opposite side of the car, when a flat spot starts to form again, then use a pin replacement tool to push in a fresh set of pins. If you start to see pitted notches starting to form on the blades, then rotate the cups to the opposite side to double the life and then replace when you start to see notches forming.

I like to use teflon dry lubricant for bike chains and I've got a set of out drives on my SCT410.1 that are approaching 5 years old. I apply fresh lube after every 10-15 battery packs.

Djr8505

As said above it is really hard to tell exactly what is wrong unless we know how high the jump is, how many times has the car hit the jump, is it landing on Dirt/grass/pavement/my brother's head the list of possible variables goes on and on...

kevinatfms

iTrader: (10)

If you can get a slipper clutch go for it. They can take the shock of the drivetrain with all that weight on those wheels/tires. That is what normally eats diffs. The sudden shock of 8+lbs going from 40mph(or more) and dead stopping when it lands.

The Slash 4x4 was notorious for this with the center diff installed on 3s. On 3s you would overspin the center diff which would shock itself when the truck landed shattering the teeth inside the center diff. I think Traxxas even put a memo in the user manual that stated the center diff should not be used on 3s.

adamnyholt

Haha. OK, some more data:

1. The ramp is about 18" high with a nice little curve towards the end. I'd say the exit angle is around 30˚.

2. I've done a lot of jumps on pavement while practicing at my home, but both times the diffs busted I was on grass.

3. I have a habit of just letting it land and come to a stop on the ground.

4. I often apply break just before landing to gyro it to land on it's feet.

5. The truck is about 1 year old, and it's my first, so it's been bashed and repaired plenty

In fact, here is a slow mo video of a jump I did before any diffs busted. (I can't post links yet so you'll have to copy/paste and fill in the blanks)

dub dub dub youtube. com/watch?v=5FLYGw14cNQ

adamnyholt

Both times the internal pin of the outdrive attaching it to the bevel gear inside the diff) snapped in half. One time the bevel gear cracked in half as well. I see your point about the outdrives. Rotating them is a good idea. But the outdrives themselves seem to be doing OK.

adamnyholt

The XXL2/e has a slipper clutch already. I've had mine dialed in nicely for regular bashing, and I locktite'd the nut it because it's notorious for loosening on this model, but I'm thinking I need to loosen it up for whenever I'm doing jumps. Thanks for affirming that.

the rc guy

there's a finesse in jumping and landing without finding the weak spot in drive train.. hitting the brake to stop wheels when jump so no mass is turning with that heavy a truck you will shear parts,..

adamnyholt

Yep, and I am totally aware that I lack this finesse Oh well. Learning is part of the hobby. And breaking things is part of learning.

I think I'm taking away:

1- No more time on asphalt/concrete. I know that stops those tires dead.
2- Make more subtle adjustments mid-air
3. Try to keep moving forward when landing
4. Adjust the slipper for a little more forgiveness on the drivetrain.

werner sline

i don't know the xxl's drive train but i have done a few jumps with different type of rc's ( do you know my channel ? )

i broke a few diffs :
the x ray ones have tiny pins : 2 or 3 pins broken
the mugen diffs are very strong but a planetary gear once broke

in my case, it is not because of the landings : it is because of the mighty torque during the take off and probably because of some crashes...

maybe you're bashing the wrong truck ? why not jump a 1/8 th buggy ? in my opinion they are more durable than trucks

fredygump

iTrader: (1)

I'd recommend asking in the monster truck section. Probably half the guys there either have an XXL or have a friend who has one, so there will be a lot more relevant experience. This section is more racing oriented, so less monster truck experience.

It would be worth doing a search. I typically use google and include "site:rctech.net" to pull results just from this forum. I prefer that to the forum's built in search feature.

platgof

iTrader: (4)

I never land on throttle. It causes all kinds of problems, like yours.