BigRock predetermined breaking point?

stefangun

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Hi there,

today I went bashing at a nice offroad track. Mainly I wanted to train on some small jumps to learn how to air-control the BR. I was really impressed with the BRs performance taking heavy landings from max. ~2m height. Mostly I managed to land on the wheels. That last jump however caused to snap one of the front left pivot balls out of the wheel hub. It was the second time this happened. The other day, I hit the curb with one of the rear wheels causing the same damage.

It is an easy fix, though, but I was wondering if this is supposed to happen to prevent other parts from breaking?


PS: BR was fitted with Louise MT Pioneer wheels. It was raining so the offroad track was very muddy. I myself hit the mud several times because it was too slippery to keep feet down. The BR however had no problems finding grip on the muddy road with these tires. Even some very steep hills were no problem for this 7kg monster. I had to switch to crawling mode, but I really was impressed by how this truck handled the track.
 

lonee

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Just turn out the pivot ball, put him from outwards ito the wheel hub and fix it again.
Better the ball slipped out than to break the hole axle.
If you want to make it more stable, Hot Racing has wheel hubs from aluminium.
But think about, the all-hub would not break, the crash force goes direct to the suspension arms and chassis.
 

stefangun

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Unfortunately, the wheel hub has a very small crack in it, exactly where the pivot ball fits in. Next semi-hard hit onto this wheel will certainly cause the ball to pop out again. So I'll have to order a spare hub. Think I'll take the alloy hubs and see what is the next weak part at the front axle. Will keep you updated.
 

Stitch

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I never had any problems with the pivot balls. My guess would be the hub is broken and that is the reason for the pivots popping out.

Even big jumps and hard landings cause no problem with my BR. (Besides the known rod ends)
 
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jimhinfl

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I had a similar problem with my big rock. Real bad tumble and the pivot ball popped out. I popped it back in and kept bashing. There was a small crack, but it never popped out again. I run every Friday with guys at work. We just bash. I did the next 2 Fridays before I noticed the crack. I didn't do a lot of jumping the next 2 Fridays though. When was checking the truck I noticed that joint was loose. That's when I saw the crack. I just replaced it and have had no issues since. I'm not a great driver and have had some spectacular end over end crashes since. Still haven't broken another one. I bought extra just in case. It's a pretty tough part and even the cracked one was holding up well. For now I'd rather leave the weak point there. It doesn't appear to be a huge issue so far. Those plastic knuckles don't seem to have a lot of flex in them so I don't think it's causing any performance issues.
 

338federal

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My front hub cracked today. Little hard landing but i ordered 2 sets of hubs. It was -2C° and much cold snow in the wheels. Maybe not the best to make hard jumps.
 

stefangun

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Next problem is that two grub screws just broke into two pieces so that they can't get unscrewed. One was a motor pinion screw and the other was the inner screw that holds the wheel nut on the axle. Very disappointing for such an expensive RC car. Now I hope to get them drilled out.

Also I found that most of the screws are literally drowned in Loctite. As their heads are relatively soft I had to be very careful with the hex driver to get them out without damaging them.
 
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