Why does this keep happening?

[Mrgoodwrench35]

Every time I run this rig at the skate park, I end up ripping the back bumper off. The two screws going into the bumper from the bottom sheer off and the two going in from the rear just pull threads out of the rear diff housing. Anybody else had this problem?

It seems to me that there aren't enough attaching points to secure the rear bumper. I'm just not sure where to add more. Any ideas are welcome.

 

[Tunedfrog]

Possible a weak spot in the design?
This is the very reason I don't run at skate parks.

 

[Mrgoodwrench35]

I don't often, but occasionally it's fun. Most of the jumping i do is from the concrete park to grass landing so it's not too hard on the cars.

This is the 3rd time this has happened. I'd agree that it's a design flaw, just not sure what I can do. I'm going to check into aluminum bulkheads but I think the same thing will happen. Just make it more expensive to repair.

I was hoping someone else had the same platform and has experienced this before.

 

[xjtorc]

I wonder if the chassis is flexing enough to cause it. Have you laid a ruler across your chassis to make sure it's still straight?

 

[Mrgoodwrench35]

I have verified the chassis is straight. I currently have an M2C chassis installed, along with their motor mount and bracing system. Definately not flexing.

 

[xjtorc]

I have verified the chassis is straight. I currently have an M2C chassis installed, along with their motor mount and bracing system. Definately not flexing.

well, dang!

 

[WickedFog]

Is that from landing on the back with the nose in the air?

 

[Mrgoodwrench35]

Is that from landing on the back with the nose in the air?

No. While I can't say all the landings were perfect, they were pretty dang close. On tires every time. The jump that broke it, I got a triple backflip and landed perfect.

The damage always occurs when leaving the ground. I have the jump when it broke on video but it's 4k and I'm having issues dumbing it down in order to share. The breakage always occurs as it leaves the concrete.

 

[Mrgoodwrench35]

At first, I thought the back bumper was catching on the edge of the concrete at the tip of the jump but the video shows no contact at all. Could it just be torque? I am hitting close to WOT at the end of the jump to get the flips. Currently running a Castle XLX2 with the 1100 kv motor on 8s. It's pretty dang lively to say the least.

 

[Mrgoodwrench35]

Like I mentioned before, this is the 3rd time this exact failure has occurred. Shears off the 2 screws in the bottom and pulls the threads out of the rear. I see that vitavon makes a rear diff housing. I may have to go that route but I'm concerned that the same thing will occur but to a more expensive part.

 

[WickedFog]

Is the suspension compressing really hard transitioning to the jump? Like is it bottoming out hard?

It's like a straight ramp is a lot harder on your suspension than a curved ramp.

 

[CertifiedMike]

Would 12.9 screws help? I'm just throwing it out there, never tried in a basher.
A broken chassis was the first thing I thought of when I read this.
I dunno what else.

 

[Mrgoodwrench35]

The jump it keeps happening on is a half pipe. I'll openly admit I'm pushing this thing to it's limits but this failure shouldn't be happening. I think it's a pretty poor design to only have 4 screws attaching the rear arms to the chassis. This is a 30lb truck if memory serves. Maybe my expectations are too high......

 

[WickedFog]

The jump it keeps happening on is a half pipe. I'll openly admit I'm pushing this thing to it's limits but this failure shouldn't be happening. I think it's a pretty poor design to only have 4 screws attaching the rear arms to the chassis. This is a 30lb truck if memory serves. Maybe my expectations are too high......

That's exactly what happened to the Jato I sent Chewy. It has two screws going into small bumps in the diff housing, which broke right off. Should be like 4 more screws holding the shock tower on. Piss poor design work.

 

[Mrgoodwrench35]

I guess I'm just surprised this thing is aparantly fragile when all my other arrma stuff has been near bullet proof. It's a shame cause I really like how this truck handles. Has more air control than anything else I own.

 

[Greywolf74]

I guess I'm just surprised this thing is aparantly fragile when all my other arrma stuff has been near bullet proof. It's a shame cause I really like how this truck handles. Has more air control than anything else I own.

Is the suspension compressing really hard transitioning to the jump? Like is it bottoming out hard?

It's like a straight ramp is a lot harder on your suspension than a curved ramp.

This is exactly what I was thinking. I know my K8 was bottoming out so hard on my curved wooden ramp I build it was actually busting a hole through the thin plywood I used for the top.

 

[Mrgoodwrench35]

That is exactly what i thought as well. If that is happening, it don't hear it, and I don't see signs of it on the bumper. Being plastic, I would think I'd see impact marks where it was catching.

I'm currently making a small aluminum 'wedge' of sorts that will mount to the bottom of the chassis just barely forward of the rear bumper. If it is catching the peak of the ramp, my hope is that the wedge will catch/take the brunt of the impact. That's all I've came up with so far.

I appreciate all the input gentlemen.

 

[gragner66]

I’d see if there is a carbon fiber or aluminum replacement piece out there some where or make one. I’m sure your not the only one with the same problem