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Posted: Aug 9, 2021 at 7:46 Quote
azfreeride wrote:
Dabroski-5 wrote:
Hey does anyone have any first hand experience with high pivot bikes. I've been designing a high pivot bike, But I was wondering if anybody noticed any significant performance gains compared to a normal bike because there are some problems with high pivot bikes and I was wondering if I should just go to a simpler normal design.

My favorite bikes have all been high pivot, however, with the supple feel of the suspension comes a couple things. If you don't have an idler pully at or near the pivot, the pedal kickback when cycling through the travel is insane, and they are notoriously inefficient at pedaling, (I'm sure this can be negated somewhat through leverage ratio curves and lockouts).

Oh yeah no way I'm not using an idler but is the supple feeling youbget from the suspension just caused by the leverage ratio or is it the actual high pivot.
Thanks,

Posted: Aug 9, 2021 at 23:21 Quote
Hey guys.
Im starting to work on a cargo bike.
Will be E assist and internal hub.
Im looking at running a front end similar to a the Catan Ti.
I was wondering if anyone had resources for steering kinematics for a bike to help design the link\angles

Posted: Aug 12, 2021 at 19:57 Quote
[Quote="Dabroski-5"][Quote="azfreeride"]
Dabroski-5 wrote:
Hey does anyone have any first hand experience with high pivot bikes. I've been designing a high pivot bike, But I was wondering if anybody noticed any significant performance gains compared to a normal bike because there are some problems with high pivot bikes and I was wondering if I should just go to a simpler normal design.

I've made a few high pivot bikes. Mostly because until recently you couldn't buy good ones. The performance is worth it especially when gravity is on your side. Perhaps not so good for groomed parky stuff.

As a designer, it gives you another parameter to tune. Part of the fun is figuring out how to make it reliable and elegant. Anti-squat is achieved without as much chain growth. Brake squat is negligible on real-world surfaces. I have not managed to get my shifting and retention as good as a traditional system.

Posted: Aug 12, 2021 at 22:11 Quote
[Quote="antgreen"][Quote="Dabroski-5"]
azfreeride wrote:


I've made a few high pivot bikes. Mostly because until recently you couldn't buy good ones. The performance is worth it especially when gravity is on your side. Perhaps not so good for groomed parky stuff.

As a designer, it gives you another parameter to tune. Part of the fun is figuring out how to make it reliable and elegant. Anti-squat is achieved without as much chain growth. Brake squat is negligible on real-world surfaces. I have not managed to get my shifting and retention as good as a traditional system.

Interesting so it definitely sounds like high pivot is the way to go. Also so pretty much as long you dont have drastic anti rise numbers it doesent make a huge difference? Interesting I was about to use a floater brake which is so damn ugly.

Thanks,

Posted: Aug 12, 2021 at 23:24 Quote
[Quote="Dabroski-5"][Quote="antgreen"]
Dabroski-5 wrote:


Interesting so it definitely sounds like high pivot is the way to go. Also so pretty much as long you dont have drastic anti rise numbers it doesent make a huge difference? Interesting I was about to use a floater brake which is so damn ugly.

Thanks,

At the risk of being wrong on the internet: I think the graphical method for calculating AR comes from Tony Foale’s book from the 70's. It might be considered still applicable to motorcycles (with their higher normal force and friction), but I don't think any real bike engineers use it as anything more than a comparison tool. Not for rear suspension anyway.

My observation is that traction is broken at a lower threshold to the suspension compressing, even on flat tarmac. Obviously, it has even less effect on gradients, on trails, and when your front brake is also applied. The AR on my current build is relatively low at 130% at top out. Perhaps in a more extreme pivot layout, such as Forbidden's, brake squat is more of an issue, but I doubt it. Can anyone here answer this?

Please treat this as anecdotal. Climb up a hill / stare at a lake / think about it for a while. Maybe there are some other effects I have overlooked. Perhaps someone is frowning at their screen in disbelief at the wild speculation and ropey claims posted here. I would love to hear from you, Frowny.

Posted: Aug 24, 2021 at 15:28 Quote
Hey does anyone have any of the CAD files for the pinion gearbox. I emailed them and they wouldn't respondlol .

Posted: Aug 24, 2021 at 16:02 Quote
Ive got them somewhere. I'll try to find em tomorrow well at work

Posted: Aug 27, 2021 at 4:44 Quote
Dabroski-5 wrote:
azfreeride wrote:
Dabroski-5 wrote:
Hey does anyone have any first hand experience with high pivot bikes. I've been designing a high pivot bike, But I was wondering if anybody noticed any significant performance gains compared to a normal bike because there are some problems with high pivot bikes and I was wondering if I should just go to a simpler normal design.

My favorite bikes have all been high pivot, however, with the supple feel of the suspension comes a couple things. If you don't have an idler pully at or near the pivot, the pedal kickback when cycling through the travel is insane, and they are notoriously inefficient at pedaling, (I'm sure this can be negated somewhat through leverage ratio curves and lockouts).

Oh yeah no way I'm not using an idler but is the supple feeling youbget from the suspension just caused by the leverage ratio or is it the actual high pivot.
Thanks,

The supple feeling you get is due to the idler being close, or concentric, to the pivot. For me, the variability of a high-pivot's COG as it cycles through its travel makes it a big no-no. Concentric BB pivot for the win!

Posted: Aug 27, 2021 at 15:55 Quote
gabodude wrote:
Dabroski-5 wrote:
azfreeride wrote:


My favorite bikes have all been high pivot, however, with the supple feel of the suspension comes a couple things. If you don't have an idler pully at or near the pivot, the pedal kickback when cycling through the travel is insane, and they are notoriously inefficient at pedaling, (I'm sure this can be negated somewhat through leverage ratio curves and lockouts).

Oh yeah no way I'm not using an idler but is the supple feeling youbget from the suspension just caused by the leverage ratio or is it the actual high pivot.
Thanks,

The supple feeling you get is due to the idler being close, or concentric, to the pivot. For me, the variability of a high-pivot's COG as it cycles through its travel makes it a big no-no. Concentric BB pivot for the win!

Hi Dabroski-5, to jump back to your first question about high-pivot designs, performance gains are relative to what you want to achieve. Every suspension layout has compromises, choose your suspension layout based on how you want the bike to ride. In my experience, from designing the Trinity MTB frame, I decided on a Virtual High Pivot layout. Our intent was to design a DH/Enduro race bike. We wanted a maximum grip, stability, and sensitivity. VHP layout fits those characteristics very well.

With regard to the natural suppleness of the high-pivot, that is a lot due to the axel path. Because the wheel moves in the same direction as the forces acting on it, less forces are translated into the frame and are directed to the spring & damper. Thus the rider feels less shock and vibration from the terrain.

The idler has very little effect on the suppleness feel. The idler is there to control the anti-squat character by way of managing the upper chainline tension and the forces put into the drivetrain system by the rider. The idler doesn't directly interact with the forces coming from the terrain which is where you experience suppleness in a suspension system.

Posted: Sep 1, 2021 at 4:16 Quote
kaimbell90 wrote:
SleepingAwake wrote:
This is gonna be neat!

Dont quite understand the suspension layout yet. is this a dw-link design? what is going on with the covered break caliper in the rear?

Will you be working with composite tools or aluminum? Or tooling board? Bladder inflation moulding or under vacuum? same process for the rear triangle? the "seat stays" look like they are going to be a pain in the neck to manufacture with the small cross section... Soo many questions.

But sure gives me another kick in the ass to invest some more nights in my bike!
Thank you! I appreciate that, your bike looks incredibly beautiful and I am really excited to see how it comes out!

As for the covered caliper, the small carbon piece you see in the corner is actually a brake cooling duct. Who knows if we will even move enough air through it to make a difference but I have to give it a try because it looks so cool in my opinion. Aside from the cooling duct you get a lot of added stiffness under braking load having it located like that, and I think it looks clean.

Tooling will be out of tooling board for the prototype. There is some good stuff out there with really low CTE that, thanks to my old place of work I can make a carbon prototype cheaper than an aluminum mule. I would also rather test in carbon so I can see the real world flex and clearances on this tightly packaged suspension layout. It will be a combination of compression (shock tunnel and some spots on the rear triangle) and bladder inflation, two halves for the rear triangle that will be bonded together.

Unfortunately, no it is not DW-Link. Although part of me wishes I did and just pay for the royalties (DW Link is amazing), I went for a VPP style setup with a mid-high instant center instead. Here is some X-ray vision for you:
X-Ray Vision

Love the frame design! Given that this is a VPP (Virtual Pivot Point) and the position of the idler is fixed, the anti squat will actually change through the travel, beyond the effect of using different gears, as the ‘Instant Centre’ will move. Typically the centre point for VPP is somewhere in front of the two pivots and crank set, and as it doesn’t stay in one place it’s definitely worth generating a dynamic model to see how the anti-squat changes. You might be able to tune the chain feedback characteristics to your advantage.

Despite what I just said, let’s go back a step. I don’t want to dampen your enthusiasm, but the point of the idler is to negate pedal feedback for high-pivot frames - they would be impractical to ride otherwise - so it’s worth going to the trouble of adding the complexity of idlers as the high pivot bikes absorb square edge bumps better (ie you can ride faster). As you don’t have a high pivot, you don’t actually need an idler in this design. VPP allows you to choose the pedal feedback / anti-squat anyway, so no loss.

What next? If you want the advantages of a high pivot and idler, the top link could become a single pivot, move the idler closer or concentric to the top link, and the bottom link could still drive the shock if you add a small dog-bone link. Not impossible with what you have so far!

Can’t wait to see how this progresses :-)

Posted: Sep 1, 2021 at 4:30 Quote
About to start a Cargo frame build,
Cad is mostly done, gonna try to keep it reasonably light with most of the front
I'm looking at building most of it from 1.25x.035 4130 steel. the 2 little side braces will be 1x.035 and the centre tube will be 1.25x.049.

Anyone built anything similar got tips on tube thickness? this will mostly haul 3x toddlers around mostly and have electric assist so weight isnt a massive issue. so tempted to bump it all into .049 wall

Posted: Sep 2, 2021 at 11:35 Quote
GregoryEpps wrote:
kaimbell90 wrote:
SleepingAwake wrote:
This is gonna be neat!

Dont quite understand the suspension layout yet. is this a dw-link design? what is going on with the covered break caliper in the rear?

Will you be working with composite tools or aluminum? Or tooling board? Bladder inflation moulding or under vacuum? same process for the rear triangle? the "seat stays" look like they are going to be a pain in the neck to manufacture with the small cross section... Soo many questions.

But sure gives me another kick in the ass to invest some more nights in my bike!
Thank you! I appreciate that, your bike looks incredibly beautiful and I am really excited to see how it comes out!

As for the covered caliper, the small carbon piece you see in the corner is actually a brake cooling duct. Who knows if we will even move enough air through it to make a difference but I have to give it a try because it looks so cool in my opinion. Aside from the cooling duct you get a lot of added stiffness under braking load having it located like that, and I think it looks clean.

Tooling will be out of tooling board for the prototype. There is some good stuff out there with really low CTE that, thanks to my old place of work I can make a carbon prototype cheaper than an aluminum mule. I would also rather test in carbon so I can see the real world flex and clearances on this tightly packaged suspension layout. It will be a combination of compression (shock tunnel and some spots on the rear triangle) and bladder inflation, two halves for the rear triangle that will be bonded together.

Unfortunately, no it is not DW-Link. Although part of me wishes I did and just pay for the royalties (DW Link is amazing), I went for a VPP style setup with a mid-high instant center instead. Here is some X-ray vision for you:
X-Ray Vision

Love the frame design! Given that this is a VPP (Virtual Pivot Point) and the position of the idler is fixed, the anti squat will actually change through the travel, beyond the effect of using different gears, as the ‘Instant Centre’ will move. Typically the centre point for VPP is somewhere in front of the two pivots and crank set, and as it doesn’t stay in one place it’s definitely worth generating a dynamic model to see how the anti-squat changes. You might be able to tune the chain feedback characteristics to your advantage.

Despite what I just said, let’s go back a step. I don’t want to dampen your enthusiasm, but the point of the idler is to negate pedal feedback for high-pivot frames - they would be impractical to ride otherwise - so it’s worth going to the trouble of adding the complexity of idlers as the high pivot bikes absorb square edge bumps better (ie you can ride faster). As you don’t have a high pivot, you don’t actually need an idler in this design. VPP allows you to choose the pedal feedback / anti-squat anyway, so no loss.

What next? If you want the advantages of a high pivot and idler, the top link could become a single pivot, move the idler closer or concentric to the top link, and the bottom link could still drive the shock if you add a small dog-bone link. Not impossible with what you have so far!

Can’t wait to see how this progresses :-)
Hey thanks for your response!

There is a limit with VPP as to how much you can tune the anti-squat and pedal kickback when you start to create a more rearward axle path via the linkage orientation. The idler is placed to where i get the anti-squat as close to 100% at sag as I can for the majority of the cassette (it does change drastically throughout the travel like you mentioned). All while keeping my pedal kickback below 5 degrees at 24t.

I did not have any luck trying to achieve those numbers with no idler while keeping the axle path I wanted. Is there something I am missing here? I did quite a bit of playing around with it before adding an idler to be honest so if there is another way of looking at it I am all ears. Thanks!

Posted: Sep 2, 2021 at 12:05 Quote
Update time:

So I 3D printed a full scale frame, the front triangle fell off the drying rack after paint and broke at all the seams after hours of filler work covering up seams and layer lines (it was printed in PLA and had no reinforcements or locating holes at the joints where it was glued, stupid I know). Anyways, with how much I put into it, I was obviously very frustrated, but I took it as a sign from the universe to start with a clean slate, take what I learned designing it, and make something better.

Here are some shots of the frame before it shattered:

3D Printed Prototype
3D Printed Prototype

The newest iteration is drastically different in looks (I went to an air show and was really getting off on the fighter jets and their brutal looks), and the suspension system has changed a wee bit. Still virtual pivot but as you can see it resembles the Banshee Legend and Canfield Jedi as opposed to the Santa Cruz/Intense style VPP.

Enduro Design Version 9

This iteration is still in the design/surfacing phase so no simulations have been done on the geometry yet, but the kinematics are pretty well established. I have tried to make this a semi community-driven design and have been making use of Instagram polls, posting different designs and surfacing options and letting the people decide.

If you guys would like I can post all of the graphs for the kinematics of the frame, I am not really trying to be secret about it,

Posted: Sep 2, 2021 at 12:12 Quote
looks so dang good!


 
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