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Riding the Inmotion V12 was fun for 5 months...then the rim exploded.


Nate1897

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2 stairs is all it takes to bust a rim so loud that you'd think someone's been shot.

Why is the rim so fragile? I know they just released the V12 HT with the reinforced rim, but if the old rim is defective they need to replace all of them for free.

Also, my screen broke from a tumble but the headlight? Unscathed. The screen is $90 but the front and back covers are $26 for both. Why is there no protection?

So fun until it wasn't.


The inside of the rim is a weak granular metal, it feels like concrete. 

EDIT: I was riding at 43 psi and I am 132 pounds (5 pounds gear). 

Edited by Nate1897
Clarification
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Back in the day when I worked in aerospace, the structures guys called aluminum castings "sugar cookies". There was a reason.

Sadly, it's how all our rims are made—the cost of something better would be prohibitive. One characteristic of a casting is the granular structure you observe, it's quite easy for a tiny micro fracture to grow into a large crack when subjected to bending forces. When you do a drop or hit a bump or pothole, the pressure increase in the tire as it deforms presses outwards on the rim and if there's a flaw in the casting...

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4 hours ago, Nate1897 said:

2 stairs is all it takes to bust a rim so loud that you'd think someone's been shot.

Why is the rim so fragile? I know they just released the V12 HT with the reinforced rim, but if the old rim is defective they need to replace all of them for free.

Also, my screen broke from a tumble but the headlight? Unscathed. The screen is $90 but the front and back covers are $26 for both. Why is there no protection?

So fun until it wasn't.


 

The inside of the rim is a weak granular metal, it feels like concrete. 

The owner's manual states that the 2.8 bar (41 psi) is suitable for this unicycle. Rim failure often occurs due to the incorrect tire pressure. The loud voice which came from the exploding rim and the forces which broken a screen are caused due to the fact that the tire pressure was obviously too low.

Unfortunately, you have no choice but to get new parts with your own money, as warranty does not cover this.

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35 minutes ago, TantasStarke said:

This guy also posted on reddit saying it was 43 PSI and that he weighs 132 pounds, I wouldn't call that too low

Are you suggesting the fracture was not due to impact?

Edited by techyiam
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2 hours ago, TantasStarke said:

This guy also posted on reddit saying it was 43 PSI and that he weighs 132 pounds, I wouldn't call that too low

Please look carefully at these pictures (3 of them), you will notice just like me that this rim has got a proper external impact. If the tire has the right amount of air pressure, this will not happen.

Here are the enlarged pictures:

https://drive.google.com/drive/folders/1vTK3_IAAPuwPi9L8dOS2bLSeJHwKpwWk?usp=sharing

Broken rim 1.jpg - how the rim should look like without external impact.

Broken rim 2.jpg - damaged rim, detected external impact, how it should not look like.

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7 hours ago, Tawpie said:

Back in the day when I worked in aerospace, the structures guys called aluminum castings "sugar cookies". There was a reason.

Sadly, it's how all our rims are made—the cost of something better would be prohibitive. One characteristic of a casting is the granular structure you observe, it's quite easy for a tiny micro fracture to grow into a large crack when subjected to bending forces. When you do a drop or hit a bump or pothole, the pressure increase in the tire as it deforms presses outwards on the rim and if there's a flaw in the casting...

So that's why Inmotion "Reinforced" the new HT model's rim. Because they don't want to make it stronger/more dense, they want to spend a little extra money on their HS models defect.

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7 hours ago, alcatraz said:

Bad luck man. Is the rim a part of the motor housing or can it be bolted off?

The rim can be taken off of the motor, you might lose a finger to the rim and motors sharp magnetized edge, but I'll take the risk.

 

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6 hours ago, Wolverine said:

The owner's manual states that the 2.8 bar (41 psi) is suitable for this unicycle. Rim failure often occurs due to the incorrect tire pressure. The loud voice which came from the exploding rim and the forces which broken a screen are caused due to the fact that the tire pressure was obviously too low.

Unfortunately, you have no choice but to get new parts with your own money, as warranty does not cover this.

Every 2 weeks I fill up my tire pressure using an electric pump.

When I refill my tire, I fill it to 43 psi

When I check the pressure after 2 weeks it's naturally deflated to 41 psi.

I've never rode the wheel unless the tire pressure is over 40 psi

If my tire was at a pressure lower than 35 psi, I would notice and stop riding. 

I understand it is recommended to ride on a high psi and in the past, I learned the hard way when first riding the Inmotion V5F on low pressure.

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4 hours ago, techyiam said:

I believe that is known as brittle fracture.  Not nice indeed. No ductility is evident. No dent rim here.

I wish it was just dented, but the material is so fragile that the material cracked and can't be welded since the metal is so granular that the better quality metal on the granular defective rim would be even less durable.

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4 hours ago, techyiam said:

Are you suggesting the fracture was not due to impact?

The fracture/crack happened on impact. After my tire blew out the 2 pieces were somewhat together until falling off with just your hand pulling lightly.

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4 hours ago, techyiam said:

The rim on the Begode T3 just bends when struck by impact. Now I know that the rim on the V12 fractures instead. Well, I better put back more air in the tire.

More air could help, but these companies should make stronger rims. If you look at a broken car rim that broke because of a large crash, the inside is smooth and dense, not granular like concrete.

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3 hours ago, TantasStarke said:

I'm just saying that the pressure wasn't "obviously too low" if OP wasn't lying about being 132lbs and the tire being at 43 PSI.

I've gone through 5 Inmotion V5F inner tubes last year and ended up riding 3 psi higher than the tube and tread was rated just to prevent the shrader valve from breaking. 

But the Inmotion V5F's rim seems way stronger than even the new Inmotion V12's rim. I know that the V12 is heavier but i've done wild stunts on that V5F and no problems. But I don't ride wild or even ride over large bumps and 2 feet destroys the V12's rim. 

2 hours ago, techyiam said:

The rim did not fracture until he went down two stairs. Just not enough information to rule out the rim was not hit by impact.

No direct impact on the rim.

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2 hours ago, Wolverine said:

Please look carefully at these pictures (3 of them), you will notice just like me that this rim has got a proper external impact. If the tire has the right amount of air pressure, this will not happen.

Here are the enlarged pictures:

https://drive.google.com/drive/folders/1vTK3_IAAPuwPi9L8dOS2bLSeJHwKpwWk?usp=sharing

Broken rim 1.jpg - how the rim should look like without external impact.

Broken rim 2.jpg - damaged rim, detected external impact, how it should not look like.

The Rim damage in both photos is likely from after my tire blew out from the rough broken rim edges, after the rim broke and my tire blew out, the rim may have impacted concrete and scratched the bent part. 

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