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Old 2018-05-10, 08:20 AM   #31
Pinoclean
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Damn! Which year model is that? Has anyone experienced this problem with the lastest model?
That is the new model but the long neck. Now the neck is shorter. Whether there will be the same problems who knows.

This is a new model.

But it can happen with impacts also.
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Old 2018-05-10, 08:27 AM   #32
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If you ride hard enough, even though that rider is only about 65kg, you can break the KH's.

A rider who weighs 45kg broke his new KH like in that picture.
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Old 2018-05-10, 08:41 AM   #33
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That's crazy It must have been some pretty extreme riding. The Impact Gravity frame looks like it might be a tad stronger, at the expense of no foot-on-crown tricks. I have no idea how the sides attach to the neck though, can't see any welds.

Last edited by Scoox; 2018-05-10 at 08:54 AM.
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Old 2018-05-10, 08:53 AM   #34
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That's crazy It must have been some pretty extreme riding. The Impact Gravity frame looks like it might be a tad stronger, at the expense of no foot-on-crown tricks. I have no idea how the sides attached to the neck though.
The impact gravity and the mad4one are probably one of the stronger ones. They are an arch shape which probably helps. The new impact gravity actually has no welds as it is hydroformed. However it also has crappy 32mm bearings.
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Old 2018-05-10, 09:51 AM   #35
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The new impact gravity actually has no welds as it is hydroformed.
The IG is definitely welded, there's no way to create a weld-free hollow 'Y' shape without using a casting process, which would result in a very weak part. In the case of the IG what they've done is first weld three sections of tube and then smoothed out the welds by sanding or CNC machining, thereby creating the illusion of a weld-free product. Other than the added aesthetic appeal, smooth welds may remove stress risers resulting in stronger joints.

Hydroforming is usually performed prior to welding, and its purpose is to shape straight tube into a funkier shape (see the sides of the Impact Gravity). Hydroformed frames are usually stronger and look sexier.

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However it also has crappy 32mm bearings.
Can't remember where but someone who was initially sceptical about these bearings used them for 6 months without a hitch. They are a bit wider than the usual uni bearings, so they either employ two rows of spherical bearings or one row of needle roller bearings (which would have much greater load capacity than much larger ball bearings). I suspect they are two-row ball bearings though.

Edit: It's defo welded, according to UDC:

Quote:
This is the first production hydro-formed unicycle frame with smooth welding; this makes it stiff, light and beautiful.

Last edited by Scoox; 2018-05-10 at 10:16 AM.
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Old 2018-05-10, 10:10 AM   #36
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Notice how in the destruction photos the ruptures are right on the edges of the welds. Any sudden change in material thickness focuses the stress and that is where they break. Although a single impact can tear metal apart by simply exceeding its tensile strength, most failures are caused by fatigue.

This is why welds are either avoided by design or polished out in high quality gear. The Impact frame is on the right track with its curves.

A second problem, especially with aluminium, is the effect of heat. Heat treatment of the same metal alloy can double its strength. Then it is all lost by welding. Worse still, the change from the tempered alloy to the heat affected weld focuses the stress.

Aluminium is very susceptible to fatigue because no matter how small a stress is applied to the material, repeating it enough times will cause fatigue crack to develop. The smaller the stress the more repeats it will take, but things have a definite design life that can be calculated very accurately for well defined forces.

Compare this to steel which has what is called a "fatigue limit". Below a certain level of stress it is not susceptible to fatigue and the stress may be applied an indefinite number of cycles. Similarly with titanium.

If you want a seriously strong, light robust frame then get a Triton titanium frame. You won't see the welds on them either. Titanium also has the advantage being corrosion proof and polishing up like a precious metal. They aren't cheap though and the standard seat tube in a Triton is very short.

However I do think you should just get a cheapie to start with and see if you actually like riding. You can always lend the cheapie to your friends instead of risking "the Rolls".
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Old 2018-05-10, 10:51 AM   #37
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Can't remember where but someone who was initially sceptical about these bearings used them for 6 months without a hitch. They are a bit wider than the usual uni bearings, so they either employ two rows of spherical bearings or one row of needle roller bearings (which would have much greater load capacity than much larger ball bearings). I suspect they are two-row ball bearings though.
They're non-standard though, which is annoying if you want to be able to mix and match parts among your fleet or keep a common set of spares.
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Old 2018-05-10, 12:17 PM   #38
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A second problem, especially with aluminium, is the effect of heat. Heat treatment of the same metal alloy can double its strength. Then it is all lost by welding.
I don't have a link but I read not two days ago on this forum that frames are treated after welding. Apparently frame manufacturers usually have big furnaces where they can bake a whole batch of frames in one go.

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Aluminium is very susceptible to fatigue because no matter how small a stress is applied to the material, repeating it enough times will cause fatigue crack to develop. The smaller the stress the more repeats it will take, but things have a definite design life that can be calculated very accurately for well defined forces.
That is comforting news. Planes made of aluminium, right?

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However I do think you should just get a cheapie to start with and see if you actually like riding. You can always lend the cheapie to your friends instead of risking "the Rolls".
Sounds like a solid plan, and a good way to get people to "join the club". I really think I'm going to get the cheaper Nimbus II.

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[32 mm bearings are] non-standard though, which is annoying if you want to be able to mix and match parts among your fleet or keep a common set of spares.
Yeah that is pretty annoying. I was expecting these bearings to be an off-the-shelf product. After all, making decent ball bearings requires a lot of expertise and very expensive facilities. Most manufacturers buy bearings from a third party e.g. SFK, NSK, etc. I've bought bearings for my trials bike before off Taobao.com, just done a search and was able to find 42x22x12 (the 'standard' unicycle hub bearing), but indeed could not find any 32x22x12 ones. Do the bearings on a trials uni degrade that quickly?

Last edited by Scoox; 2018-05-10 at 12:22 PM.
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Old 2018-05-10, 12:28 PM   #39
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That is comforting news. Planes made of aluminium, right?
Yes. Engineers do a lot of calculations and the parts are replaced on schedules.

I remember an episode of "Air Crash Investigation" where the repairers fitted two rows of rivets where there should have been three. The repair still handled thousands of pressurisation cycles until it failed catastrophically. Engineers calculated the expected life of the faulty repair and were out by twelve cycles from what actually happened.

They use titanium in critical parts and increasingly, carbon fibre parts glued together. I do hope it is very good glue.
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Old 2018-05-10, 01:19 PM   #40
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Originally Posted by Scoox View Post
The IG is definitely welded, there's no way to create a weld-free hollow 'Y' shape without using a casting process, which would result in a very weak part. In the case of the IG what they've done is first weld three sections of tube and then smoothed out the welds by sanding or CNC machining, thereby creating the illusion of a weld-free product. Other than the added aesthetic appeal, smooth welds may remove stress risers resulting in stronger joints.

Hydroforming is usually performed prior to welding, and its purpose is to shape straight tube into a funkier shape (see the sides of the Impact Gravity). Hydroformed frames are usually stronger and look sexier.



Can't remember where but someone who was initially sceptical about these bearings used them for 6 months without a hitch. They are a bit wider than the usual uni bearings, so they either employ two rows of spherical bearings or one row of needle roller bearings (which would have much greater load capacity than much larger ball bearings). I suspect they are two-row ball bearings though.

Edit: It's defo welded, according to UDC:
My mistake about the welds. Though not a mistake about the 32mm bearings being rubbish. I know a 48kg 13 yr old who has broken 4 pairs of them. I know a good rider who is 68kg who destroyed them in 3 weeks of flatland. Any serious riding even for a light person will break them, and if you tighten the bearing holders too much (I suspect this may have been an issue with the 13 yr old) it also destroys them. When I say too much I mean the amount you need to tighten them to stop them coming undone when you don't have Loctite. Loctite is a necessity of you want them to not come loose.

Doesn't happen with 42s.

Udc Brought the size in using dual 32mm bearings to make up the width, those were rubbish so they ended up making double thickness single bearings, they are still almost as bad.
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Old 2018-05-10, 03:29 PM   #41
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That is comforting news. Planes made of aluminium, right?
Yes, a neighbor of mine was killed 17 years ago on American Airlines Flight 587, which went down after the rudder fell off. Metal fatigue was partly blamed, I think. Metal fatigue was also mentioned in the case of that Southwest Airlines flight a few weeks ago where a passenger was killed by being sucked halfway out of the plane after fragments of one of its turbines knocked out the window next to her. Airport security keeps getting more invasive, but maintenance of aging fleets of aircraft keeps getting outsourced, cut back and downsized. Many US airlines now have their maintenance done in the US South, where the mechanics have no unions, or even in Central America.

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I really think I'm going to get the cheaper Nimbus II.
Even if you end up doing a lot of unicycling (which most unicycle buyers do not), it will probably be months or maybe even years before you are attempting stuff that would destroy a Nimbus II (unless you are very heavy).

I never had a Nimbus II, though. I went from a $30 unicycle (which I had to replace many parts of in order to free mount or ride more than a short distance without extreme discomfort or even occasional bleeding) to an Impact-Nimbus-KH hybrid almost-trials unicycle.
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Old 2018-05-10, 05:05 PM   #42
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Originally Posted by Pinoclean View Post
My mistake about the welds. Though not a mistake about the 32mm bearings being rubbish. I know a 48kg 13 yr old who has broken 4 pairs of them. I know a good rider who is 68kg who destroyed them in 3 weeks of flatland. Any serious riding even for a light person will break them, and if you tighten the bearing holders too much (I suspect this may have been an issue with the 13 yr old) it also destroys them. When I say too much I mean the amount you need to tighten them to stop them coming undone when you don't have Loctite. Loctite is a necessity of you want them to not come loose.

Doesn't happen with 42s.

Udc Brought the size in using dual 32mm bearings to make up the width, those were rubbish so they ended up making double thickness single bearings, they are still almost as bad.
So basically all the supposedly high-end unis have issues. The KH20 snaps, the IG has cheese bearings, pick your poison. What's the word on the trials Nimbus Equinox though? The frame looks skinny and flimsy but is it? I'm beginning to get the feeling all unicycles are made of cheese.

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Yes, a neighbor of mine was killed 17 years ago on American Airlines Flight 587, which went down after the rudder fell off. Metal fatigue was partly blamed, I think. Metal fatigue was also mentioned in the case of that Southwest Airlines flight a few weeks ago where a passenger was killed by being sucked halfway out of the plane after fragments of one of its turbines knocked out the window next to her. Airport security keeps getting more invasive, but maintenance of aging fleets of aircraft keeps getting outsourced, cut back and downsized. Many US airlines now have their maintenance done in the US South, where the mechanics have no unions, or even in Central America.
That's worrying...

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Even if you end up doing a lot of unicycling (which most unicycle buyers do not), it will probably be months or maybe even years before you are attempting stuff that would destroy a Nimbus II (unless you are very heavy).
I'm probably underestimating the time it takes to get to even level 1.

The one I bought (and returned) a couple of weeks ago, branded 'Knight' (local Chinese brand) had a very beefy frame. The crown was forged aluminium. The frame itself seemed solid. It was a bit on the heavy side at 5.4 kg with the Maxxis CC tyre. Then there's this other one branded 'Teliang' (特亮)which looks similar to the IG but uses proper 42x22x12 bearings, price is about 200 USD:

Name:  Teliang uni (Custom).jpg
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Unfortunately with this local Chinese brands you get very little info on specs, so there's no way of knowing what material the thing is made of etc.

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I never had a Nimbus II, though. I went from a $30 unicycle (which I had to replace many parts of in order to free mount or ride more than a short distance without extreme discomfort or even occasional bleeding) to an Impact-Nimbus-KH hybrid almost-trials unicycle.
Which brand was the frame?

Last edited by Scoox; 2018-05-10 at 05:13 PM.
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Old 2018-05-10, 09:13 PM   #43
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Only issues with equinox is many don't like the 25.4 seat post diameter and if you get good at trials which usually requires a very good tuck the big square corners of the crown can be brutal on the knees. See the tuck here

https://youtu.be/tp9ZuZoszvQ

Old KH model
Old impact gravity model
Current mad4ones seem to not have any major flaws. The Old KH did break but not as fast as the new one.

To be honest though the breaking doesn't occur so much from trials only from tricks. You need to be practicing a LOT to end up stressing it that much.

I did still bend the new KH from a smaller volume of tricks however I'm 90kg.
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Old 2018-05-10, 11:20 PM   #44
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Originally Posted by Pinoclean View Post
Only issues with equinox is many don't like the 25.4 seat post diameter and if you get good at trials which usually requires a very good tuck the big square corners of the crown can be brutal on the knees. See the tuck here

https://youtu.be/tp9ZuZoszvQ

Old KH model
Old impact gravity model
Current mad4ones seem to not have any major flaws. The Old KH did break but not as fast as the new one.

To be honest though the breaking doesn't occur so much from trials only from tricks. You need to be practicing a LOT to end up stressing it that much.

I did still bend the new KH from a smaller volume of tricks however I'm 90kg.
Wow that video is pretty breathtaking, is that unicycle level 2 o 3?

Anyway, isn't the white frame in the video the IG with the thin bearings?
The mad4ones look solid in every way, that could be the answer.

Last edited by Scoox; 2018-05-10 at 11:22 PM.
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Old 2018-05-10, 11:30 PM   #45
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That Teliang might be a Chinese ripoff of the Impact Gravity, though since all these things are made in China anyway, perhaps it isn't fair to call it a ripoff. If you do get one, a lot of people on this forum will be curious to know how it holds up.

The hybrid unicycle I got was -I assume- made of parts that UDC was trying to clear out of its inventory in 2013. The frame is Impact Reagent, the wheelset was KH20 flatland, and the rest is mostly Nimbus, though I think the seat is some sort of KH/Nimbus joint venture.

Any frame will snap if you are a crazy enough rider. Pinoclean provides details above. The only really serious problem with my uni was the KH Moment hub, which started to creak almost immediately. As I learned from this forum, KH hubs had had this problem for a number of years, but the more recent KH Spirit hub apparently does not. I finally persuaded UDC to give me a replacement Nimbus hub- the same hub that is in the Nimbus II. No problems there, and it's been several years. The other things that broke on my uni were only after extended periods of heavy use.

It took me months to learn to hop, but that was partly because I started on a $30 unicycle and knew that hopping would destroy it, so I learned other basic skills first. I met one guy who learned to hop before he could even ride, but he had just bought himself a very solid municycle, and I guess hopping was the most obvious thing to do with it.
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