Infraction Oscillation center driveshaft issues. Sorry if this has been posted already.

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jondilly1974 said:
How tight is the fit of that shaft front to rear? Is there some play at the cups?
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Thats what I figured at first but then thought of guitar strings and harmonics etc. I'll see if I can find the entire thread to link. There are potential fixes but it looks to be too thin of a shaft, too long, or not tough enough steel, or need to split and add a bearing like the BRCC has on plastic shaft. Great opportunity for MIP etc if you ask me. Plus, how thick can we go if we're so close to that chassis brace?

I cant find it but it's at Arrma RC Army on FB. This is why I hate FB groups. Poor design and bad form to find stuff. I don't know why people start communities at FB for more reasons than that they're cucked anyway and untrustworthy.
 
crimsonfancy said:
Thats what I figured at first but then thought of guitar strings and harmonics etc. I'll see if I can find the entire thread to link. There are potential fixes but it looks to be too thin of a shaft, too long, or not tough enough steel, or need to split and add a bearing like the BRCC has on plastic shaft. Great opportunity for MIP etc if you ask me. Plus, how thick can we go if we're so close to that chassis brace?

I cant find it but it's at Arrma RC Army on FB. This is why I hate FB groups. Poor design and bad form to find stuff. I don't know why people start communities at FB for more reasons than that they're cucked anyway and untrustworthy.
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Haha I didn’t notice it was a @Aussie RC Playground video. I should have identified his voice. He’s far more qualified to answer this question than I am. I will kindly STFU and let him figure this out.
 
jondilly1974 said:
Haha I didn’t notice it was a @Aussie RC Playground video. I should have identified his voice. He’s far more qualified to answer this question than I am. I will kindly STFU and let him figure this out.
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He can't figure it out yet.
It happens at certain rpms only. Clearly oscillation / harmonics if we think of music instruments. It happens exactly in the center of length and splits again etc but in this case the shaft is thick enough to only really show at certain rpm.
You can click below the video possibly to see others respond. I can't find the thread.
 
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I've noticed this before in the flat chassis 6s line up, although I've not personally seen the center part of the shaft break plane like in the video Raz posted. It's reduced slightly while under load but the length of the driveshaft plays a huge part in the harmonics of a driveshaft. It's not detrimental to performance but it adds vibration to the driveline that will not play well with the bearings down the center of the chassis.
 
jondilly1974 said:
Haha I didn’t notice it was a @Aussie RC Playground video. I should have identified his voice. He’s far more qualified to answer this question than I am. I will kindly STFU and let him figure this out.
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Thanks for tagging me in this.
Well, there has been some development and I've had others share their videos to me of the same driveshaft in their cars. Here's what I know so far;
1. A little vibration is normal, so if yours does not spin totally straight and true that's fine. However, mine is very bad and shouldn't be like that at all.
2. My shaft has been this way since new, I have not crashed the car at all and have only used it a few times, so there's no excuse for it to be this way. It's possible my shaft has been faulty from new and during running, it has gotten worse. The solution is to replace the shaft and hopefully it won't happen again.
3. I have been discussing this with some of the guys at ARRMA and they are very aware of my video and want to follow my results. They have not found this problem before, so could be the usual "reviewer's curse" thing and hopefully a replacement shaft will fix the issue.

Lastly, on my Facebook post some people have suggested making a bearing support for the driveshaft similar to that found on the 4S Kraton, however, that's not possible because it's a dog bone. ARRMA would have to come up with a driveshaft you can dismantle in order to fit some sort of bearing support mid way.
If you have any other questions, please let me know, I'll do my best to answer them. I should have a new shaft by the end of the week, so I'll let you all know the outcome.
 
Aussie RC Playground said:
Thanks for tagging me in this.
Well, there has been some development and I've had others share their videos to me of the same driveshaft in their cars. Here's what I know so far;
1. A little vibration is normal, so if yours does not spin totally straight and true that's fine. However, mine is very bad and shouldn't be like that at all.
2. My shaft has been this way since new, I have not crashed the car at all and have only used it a few times, so there's no excuse for it to be this way. It's possible my shaft has been faulty from new and during running, it has gotten worse. The solution is to replace the shaft and hopefully it won't happen again.
3. I have been discussing this with some of the guys at ARRMA and they are very aware of my video and want to follow my results. They have not found this problem before, so could be the usual "reviewer's curse" thing and hopefully a replacement shaft will fix the issue.

Lastly, on my Facebook post some people have suggested making a bearing support for the driveshaft similar to that found on the 4S Kraton, however, that's not possible because it's a dog bone. ARRMA would have to come up with a driveshaft you can dismantle in order to fit some sort of bearing support mid way.
If you have any other questions, please let me know, I'll do my best to answer them. I should have a new shaft by the end of the week, so I'll let you all know the outcome.
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Is there front to rear play in that driveshaft like the other 6S rigs? Or is it tight fitting in the cups?
 
jondilly1974 said:
Maybe try some rubber o-rings to snug it up but allow some flex? Just grasping at straws trying to help.
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Appreciate that, thank you. The thing is that the shaft has a very slight bent in it and at high RPM it does what you see in the video. You can also hear it when I do my speed runs with it and that was the very first time I drove it, so it's been like this since new. So I don't think rubber o-rings will help in this case, unfortunately. I'm just gonna chalk this one down to a faulty shaft that needs replacing and once I install a new one, we'll see if that fixes it. ?
 
Aussie RC Playground said:
Appreciate that, thank you. The thing is that the shaft has a very slight bent in it and at high RPM it does what you see in the video. You can also hear it when I do my speed runs with it and that was the very first time I drove it, so it's been like this since new. So I don't think rubber o-rings will help in this case, unfortunately. I'm just gonna chalk this one down to a faulty shaft that needs replacing and once I install a new one, we'll see if that fixes it. ?
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Does the shaft appear to be curved when out of the truck? Can you tell which way it is bent? You could try the @Mr.Duke 3 bolts in a vise trick?
 
Did you ever figure out any solution? I am having the same problem on a new Infraction. Never been wrecked. Manually checked the runout and there is about .5mm of runout on the driveshaft. My concern is sort of a chicken and egg thing, is that minor runout from the oscillation happening or is it due to a defect per se (as in it was never perfectly straight, it is too weak given the length, etc.). Has anyone from Arrma chimed in on this issue? I can only imagine that this problem would be even further compounded on the Limitless given the smaller gears resulting in a higher shaft rpm. My fear is that this condition is going to result in a catastrophic failure causing major damage to the model or even worse the battery cooking the model into a mass of molten metal and plastic.
 
I saw a video with the (8S) and it vibrates a lot too.
I checked my truck several times and I have no vibration. (y)
 
Aussie RC Playground said:
Lastly, on my Facebook post some people have suggested making a bearing support for the driveshaft similar to that found on the 4S Kraton, however, that's not possible because it's a dog bone. ARRMA would have to come up with a driveshaft you can dismantle in order to fit some sort of bearing support mid way.
Click to expand...

Some of the guys that make their own parts on CNC could make a split hub that clamps to the bone for the ID of the bearing and a stand/mount for the OD of the bearing to mount to the chassis. The ID of the bearing just needs to be large enough to clear the ears of the bone. Balancing the hub could be a chore... but once you figure out the weight, that could be dealt with.
 
olds97_lss said:
Some of the guys that make their own parts on CNC could make a split hub that clamps to the bone for the ID of the bearing and a stand/mount for the OD of the bearing to mount to the chassis. The ID of the bearing just needs to be large enough to clear the ears of the bone. Balancing the hub could be a chore... but once you figure out the weight, that could be dealt with.
Click to expand...

I have ordered these 8mm driveshafts from Amped RC. No more flexy, bendy shafts. ?
48084
 
Aussie RC Playground said:
I have ordered these 8mm driveshafts from Amped RC. No more flexy, bendy shafts. ?
View attachment 48084
Click to expand...
Nice! Steel or stainless?

There used to be a guy in the US that made something like those, back in my savage/big block t-maxx days. I never bought them as I didn't have a ton of issues with the engines I ran.

Was rcalloys.com... doesn't exist anymore :(
 
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