Jett's Team Honda HRC shock linkage

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

cwtoyota wrote:

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot. It's possible that it's simply...

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot.

It's possible that it's simply there to aid the mechanics in pre-assembly.
With that brace, they can assemble the single pull rod to the knuckle (bell crank) on the work bench and torque up that fastener.
In that way, they can pre-assemble several different linkages in the shop and load them into the truck.

Without that brace, they'd have to fabricate a spacer and purchase a long bolt to span between the front pull-rods to keep them aligned during pre-assembly.   Also, if a pre-assembled linkage without a brace is dropped or bumped around pretty hard, it can mis-align the pull rods making it a royal pain in the ass to install on the bike in the pre-assembled state.

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

cwtoyota wrote:

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot. It's possible that it's simply...

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot.

It's possible that it's simply there to aid the mechanics in pre-assembly.
With that brace, they can assemble the single pull rod to the knuckle (bell crank) on the work bench and torque up that fastener.
In that way, they can pre-assemble several different linkages in the shop and load them into the truck.

Without that brace, they'd have to fabricate a spacer and purchase a long bolt to span between the front pull-rods to keep them aligned during pre-assembly.   Also, if a pre-assembled linkage without a brace is dropped or bumped around pretty hard, it can mis-align the pull rods making it a royal pain in the ass to install on the bike in the pre-assembled state.

Village Idiot wrote:

That's what I was wondering - if its primary function is to ease/speed assembly since side/torsional loads don't seem apparent there. But this is also the...

That's what I was wondering - if its primary function is to ease/speed assembly since side/torsional loads don't seem apparent there.

But this is also the Honda that gave us twice-pipes... 

Cayden Thompson wrote:

So let me get this straight , the current Honda frame sucks so bad they have to not only add to the frame in the front...

So let me get this straight , the current Honda frame sucks so bad they have to not only add to the frame in the front but also to the linkage as well? Am I missing something?

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

cwtoyota wrote:

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot. It's possible that it's simply...

Yeah, If it's bracing anything, it's adjacent to the stiffest part of the frame so it's not likely doing a lot.

It's possible that it's simply there to aid the mechanics in pre-assembly.
With that brace, they can assemble the single pull rod to the knuckle (bell crank) on the work bench and torque up that fastener.
In that way, they can pre-assemble several different linkages in the shop and load them into the truck.

Without that brace, they'd have to fabricate a spacer and purchase a long bolt to span between the front pull-rods to keep them aligned during pre-assembly.   Also, if a pre-assembled linkage without a brace is dropped or bumped around pretty hard, it can mis-align the pull rods making it a royal pain in the ass to install on the bike in the pre-assembled state.

Village Idiot wrote:

That's what I was wondering - if its primary function is to ease/speed assembly since side/torsional loads don't seem apparent there. But this is also the...

That's what I was wondering - if its primary function is to ease/speed assembly since side/torsional loads don't seem apparent there.

But this is also the Honda that gave us twice-pipes... 

cwtoyota wrote:

Every time I think of those Honda twice pipes, I also think of the time Yoshimura had a BOGO on muffler cores (see pic) and I...

Every time I think of those Honda twice pipes, I also think of the time Yoshimura had a BOGO on muffler cores (see pic) and I wonder... What if?

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

JM485 wrote:

It’s a little hard to see and I’m not super familiar with the newer Hondas, but from the photos is almost looks like the links on...

It’s a little hard to see and I’m not super familiar with the newer Hondas, but from the photos is almost looks like the links on either side are not quite parallel but actually taper in slightly towards the linkage knuckle?  If that’s the case then a bending moment would be applied to the link and its most intense point would be right about where that brace was added, wouldn’t it?  Although it seems unlikely, I wonder if Jett was putting so much load on the links in SX that they were noticing some early signs of stress in that area and decided to add some support.

 

I don’t know, I’m just throwing out ideas and could be way off, but if those links are indeed not parallel with each other that’s my best guess.  

Luxon MX wrote:

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see...

That's a bit of an odd brace. I wonder if they actually tested it (a bench test with indicators, etc., not physically riding it) to see if there actually was a binding issue. In a perfect world, the linkage should only see tension loads and no torsional load that would cause binding.

But the world is not perfect, and I'm sure it sees some torsion. But I bet it's really small, not enough to bind anything up. In order for the linkage arm to see any load other than tension, you have to get some significant deflection between the knuckle attachment on the swingarm and the swingarm pivots or significant deflection between the frame's swingarm attachments and the linkage arm attachments. But both of those areas are massively stiff in torsion. And there's some slop in the bearings, so you'd need enough deflection to overcome that slop in order to start binding anything. 

I could be wrong, and a bench test would prove it one way or another, but from looking at it from a distance I don't think this would help much of anything from a binding or rigidity perspective. Maybe it has some other function? 

JM485 wrote:

It’s a little hard to see and I’m not super familiar with the newer Hondas, but from the photos is almost looks like the links on...

It’s a little hard to see and I’m not super familiar with the newer Hondas, but from the photos is almost looks like the links on either side are not quite parallel but actually taper in slightly towards the linkage knuckle?  If that’s the case then a bending moment would be applied to the link and its most intense point would be right about where that brace was added, wouldn’t it?  Although it seems unlikely, I wonder if Jett was putting so much load on the links in SX that they were noticing some early signs of stress in that area and decided to add some support.

 

I don’t know, I’m just throwing out ideas and could be way off, but if those links are indeed not parallel with each other that’s my best guess.  

Luxon MX wrote:

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose...

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose.

I ran some analysis on the Honda linkage arms, and the reaction moment at the bearing is surprisingly large. There's not much info that I could find about permissible moments on roller needle bearings, but the Koyo technical reference states:

"When a couple load (overturning moment) is imposed on a single row of needle rollers, the resulting uneven distribution of load can seriously affect bearing life. In such cases, two rows of needle rollers are generally suggested."

And that makes a lot of sense. The load ratings for a needle bearing assume that the full width of the bearing is taking the load. When a moment is also applied, that evenly distributed load becomes unbalanced and one end of the bearing sees more load than the other end. That end is more likely to exceed the load rating of the bearing. And the bigger the moment, the worse it is for that end. 

The bearings in the Honda linkage (and all others I've seen) are single row, so the moment is not good for bearing life. Honda has been using this linkage offset geometry since 2017 at least, and I haven't heard of any "normal" riders having bearing issues. But with supercross suspension (really stiff springs and valving) combined with top pro riders really pushing it, their loads are a lot higher than regular riders. 

The brace drops the bending moment at the bearing to just under 1/6 of what it would be without it. That's significant. Under big hits, the forces go beyond the load rating on one side of the rollers, which will lead to permanent deformation of the rollers/races and reduce bearing life.

But there's not really any evidence to suggest the brace does anything else. For normal mid-stroke hits, bearing forces are below the load limit, so there should be no binding present that would have an effect on "feel". Of course, if Jett blows out the bearings with a huge hit, they will be more likely to bind under "normal" riding as they're now damaged.

Longitudinal stiffness between the two link styles is nearly identical (5.4% difference of not much is basically nothing). Stress levels are essentially identical between the two as well. 

There's not a ton of room to work with on the frame side of the linkage to move the bearings to a more ideal location, which is probably why it's designed with this offset in the first place. But at the knuckle side, there looks to be more room for a fix. This would require a longer race/buckets on the knuckle and a longer bolt, but could remove the bending moment entirely without the need for the brace. I'd need to spend some time with a Honda to make sure there's enough clearance there, but that may be a more straight-forward and lighter solution than the brace across the linkage arms.
 

Money wrote:

I dont think a factory team is worried about bearing life….. there’s a feel difference there im sure or they would not be running it. All...

I dont think a factory team is worried about bearing life….. there’s a feel difference there im sure or they would not be running it. All the engineering and graphs are great but the true test is track testing.  If it didnt make a difference they would not be running it 

Luxon MX wrote:

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose...

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose.

I ran some analysis on the Honda linkage arms, and the reaction moment at the bearing is surprisingly large. There's not much info that I could find about permissible moments on roller needle bearings, but the Koyo technical reference states:

"When a couple load (overturning moment) is imposed on a single row of needle rollers, the resulting uneven distribution of load can seriously affect bearing life. In such cases, two rows of needle rollers are generally suggested."

And that makes a lot of sense. The load ratings for a needle bearing assume that the full width of the bearing is taking the load. When a moment is also applied, that evenly distributed load becomes unbalanced and one end of the bearing sees more load than the other end. That end is more likely to exceed the load rating of the bearing. And the bigger the moment, the worse it is for that end. 

The bearings in the Honda linkage (and all others I've seen) are single row, so the moment is not good for bearing life. Honda has been using this linkage offset geometry since 2017 at least, and I haven't heard of any "normal" riders having bearing issues. But with supercross suspension (really stiff springs and valving) combined with top pro riders really pushing it, their loads are a lot higher than regular riders. 

The brace drops the bending moment at the bearing to just under 1/6 of what it would be without it. That's significant. Under big hits, the forces go beyond the load rating on one side of the rollers, which will lead to permanent deformation of the rollers/races and reduce bearing life.

But there's not really any evidence to suggest the brace does anything else. For normal mid-stroke hits, bearing forces are below the load limit, so there should be no binding present that would have an effect on "feel". Of course, if Jett blows out the bearings with a huge hit, they will be more likely to bind under "normal" riding as they're now damaged.

Longitudinal stiffness between the two link styles is nearly identical (5.4% difference of not much is basically nothing). Stress levels are essentially identical between the two as well. 

There's not a ton of room to work with on the frame side of the linkage to move the bearings to a more ideal location, which is probably why it's designed with this offset in the first place. But at the knuckle side, there looks to be more room for a fix. This would require a longer race/buckets on the knuckle and a longer bolt, but could remove the bending moment entirely without the need for the brace. I'd need to spend some time with a Honda to make sure there's enough clearance there, but that may be a more straight-forward and lighter solution than the brace across the linkage arms.
 

Luxon MX wrote:

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose...

After diving into this a bit more, I suspect the brace is just a band-aid to improve bearing life, and doesn't really serve any other purpose.

I ran some analysis on the Honda linkage arms, and the reaction moment at the bearing is surprisingly large. There's not much info that I could find about permissible moments on roller needle bearings, but the Koyo technical reference states:

"When a couple load (overturning moment) is imposed on a single row of needle rollers, the resulting uneven distribution of load can seriously affect bearing life. In such cases, two rows of needle rollers are generally suggested."

And that makes a lot of sense. The load ratings for a needle bearing assume that the full width of the bearing is taking the load. When a moment is also applied, that evenly distributed load becomes unbalanced and one end of the bearing sees more load than the other end. That end is more likely to exceed the load rating of the bearing. And the bigger the moment, the worse it is for that end. 

The bearings in the Honda linkage (and all others I've seen) are single row, so the moment is not good for bearing life. Honda has been using this linkage offset geometry since 2017 at least, and I haven't heard of any "normal" riders having bearing issues. But with supercross suspension (really stiff springs and valving) combined with top pro riders really pushing it, their loads are a lot higher than regular riders. 

The brace drops the bending moment at the bearing to just under 1/6 of what it would be without it. That's significant. Under big hits, the forces go beyond the load rating on one side of the rollers, which will lead to permanent deformation of the rollers/races and reduce bearing life.

But there's not really any evidence to suggest the brace does anything else. For normal mid-stroke hits, bearing forces are below the load limit, so there should be no binding present that would have an effect on "feel". Of course, if Jett blows out the bearings with a huge hit, they will be more likely to bind under "normal" riding as they're now damaged.

Longitudinal stiffness between the two link styles is nearly identical (5.4% difference of not much is basically nothing). Stress levels are essentially identical between the two as well. 

There's not a ton of room to work with on the frame side of the linkage to move the bearings to a more ideal location, which is probably why it's designed with this offset in the first place. But at the knuckle side, there looks to be more room for a fix. This would require a longer race/buckets on the knuckle and a longer bolt, but could remove the bending moment entirely without the need for the brace. I'd need to spend some time with a Honda to make sure there's enough clearance there, but that may be a more straight-forward and lighter solution than the brace across the linkage arms.
 

CarlinoJoeVideo wrote:

Hey Billy, cool work on this analysis!  Which direction is that load when showing the stress test?  What if there was a side load, like going...

Hey Billy, cool work on this analysis!  Which direction is that load when showing the stress test?  What if there was a side load, like going around a turn then up a jump face or a long sweeping corner, can you see the stress points from something like that?