Frame Design

Bit of a shop rat question. I know santa cruz have lifetine warrantee on pivots but im wondering how much a shop would charge for labour to replace all the pivots? Is there a bike company that has the easiest most inexpensive pivot replacement set up? Im kind of looking at devinci as well

I'm super frustrated, as this has happened to my previous design as well. 

My single pivots keep cracking right here, around the main pivot shell. I knew this would be a high stress area so I even added a gusset here. My guess is that the angle between this gusset and the downtube is too acute and putting stress on the weld, causing the crack. 

What are people's recommendation? Add yet another gusset on top at a shallower angle? or just change the angle of the existing one? 

This is a short travel titanium single pivot that hasn't been hucked off anything more than probably 5 feet. 

if theres a way to do one smooth gusset, thats the move cause a lot of sharp corners are going to cause a lot of stress in a small area.

Could also help if i could see the frame woithout the rear triangle on it and where specifically the cracks are helping. 

Does this give you a better view? 


So you're saying just modify the existing gusset to meet the downtube at a less sharp angle, like this below?

On my current build I have used a set of plates to tie the bb/main pivot/shock mount all together with the downtube. So far it has worked well. The plates are probably a touch on the thin side, I had Send Cut Send do them and they have limited options in 4130. 

Mainly talking about where the gusset sections meet each other and the frame to make a sharp angle. That 4030 plate looks really cool!

Titanium for now. 

I'm exploring steel for an ebike. 

Maybe you could increase the wall thickness of the down tube in addition to the gusset with a shallower angle?

Hi guys, i'm about to build a frame with the help of a local builder. It's going to be a single pivot and i was wondering about the pivot placement: above the BB or concentric to the BB ? 140mm of travel with 230x65 shock. What would you suggest and why ? 

Definitely not concentric. 

i totally get where you are coming from about concentric, for a dirt jumper that could be the way to go. For a trail bike you definitely wont want to go concentric. the construction is a little more challenging but the kinematics wont come out the way youd likely want it for a trail bike. single pivot layouts tend to have a linear leverage rate. as for the length and stroke for the shock, most bike companies run 50-55mm of stroke for a bike around 140 mm of travel. cascade components had a good explanation about it in this forum. they know what they are talking about. 

Above the BB - a concentric pivot has extremely low anti squat and anti rise characteristics so is pretty awful and hyperactive under pedaling and braking. Have you played with linkage software at all? Most single pivot bikes are around the top of the chainring because it has an OK balance of pedaling efficiency without too many drawbacks

Agreed on the 55 mm shock. The 65 mm shock will actually have low pressures. I ran about 150 psi in the SDLX on my Bird Aeris AM9 at 150 mm travel at 75ish kg. 

The main problem with a leverage ratio that low is that you will have problems finding a shock with a tune opened enough for it to work properly... 

Thank you all for the answers ! I was also perplexes when the builder proposed the concentric option...so i asked here.

Regarding the shock longer than usual: i'm kind of heavy 96kg and i do drops that many will describe as dumb and useless, currently on a raaw jibb with a progressive 550-670 or 700lbs coil, i was hoping that with this layout i could use a lighter spring and have both better tracking and better bottom out resistance, the shock will be a canecreek kitzuma to have a wide compression range.

What about an air shock and/or a progressive linkage frame design? 

I don't really like how they perform and reliability is not up to the task in my experience.

Regarding a progressive linkage, i would like to try it but in a second iteration similar to stanton (they use both a linkage and a long shock 230x65 for 140mm of travel) with this frame i would like to learn the basics.

While I haven't done it, probably depends on the type. For carbon I guess it's a single part (the shell is the main feature anyway) the important part with carbon is to have a way to make a mold for it. 

For welded frames I guess you could make it tube by tube and do a welded assembly (CAD generally can differentiate an ordinary assembly from a welded assembly I think). That way you get single parts (plates, machined pieces, tubes) that you can easily make drawings of. And probably size it up and down easier. 

I design it all in one which admittedly might not be the “best” way to do it but the designs change a lot so if I need to make more room for the tire, I can adjust something like how wide the main pivot is on the front triangle, and it will move everything else.  The main pivot yoke gets wider, the chainstays still connect and I don’t have to manually redesign different parts.  

I haven't modelled anything quite as complex as an entire full suspension bike (not completely anyway, lots of rough models though) but I feel like modern Parametric CAD software makes designing them in one file a lot easier as if it is constrained properly, you can make single changes and the rest of your design will automatically update. Having them in separate files could get risky with managing versions and make it more likely to break the links.

If you use Onshape there are tons of free models you can browse to get an idea of how people do it (good and bad), I also remember Fusion 360 came with a sample model of a suspension bike you could explore too. 

One thing that may or may not be important is that rendering lots of different parts at once gets pretty complex computationally - some desktops will struggle to display them well, so that might influence how you design things too

i very briefly used solidworks for a couple of projects, i almost exclusively use fusion 360. It helps to model it all in one place and have each part defined by some other parts around it. just in case someone tell you they want a different head angle or slightly different pivot placement half way through the project, you can do that in a few seconds instead of possibly having to start over. 

Speaking of CAD, does anyone have resources for components? Forks, shocks, cranks, derailleurs, brake calipers? Wheels are probably easiest to handle when doing a frame design...

BTW, when you guys are doing single part front triangles in CAD, how do you do the drawings for parts like headtubes, BB shells, mounts and co and even where to cut the tubes themselves?

I’ve got some shock files (very rough) that I made from copying measurements from manufacturers websites. Cane creek has their drawings available. SRAM also makes their UDH files available publicly. You can find forks and drivetrain parts off of GrabCad

As for the head tubes and bottom brackets, paragon machine works has some good ones And they provide STEP files and PDF drawings. 
To get separate drawings for stuff I create the front triangle in separate bodies in fusion 360 and I can export the individual parts to make them into drawings 

Hey guys? I'm sure everyone has heard of the Bonell "ebike" that uses a 6000 watt CYC bolt on kit. What most people don't realize is they have an "All Mountain" model that uses a much slimmer, lighter, and Class 1 compatibility: 

https://ridebonnell.com/products/bonnell-775-am?variant=50135965040956

I want to build my own frame and try out that other motor (CYC Photon), as the gen 2 of it has just been announced. I'm trying to see if Marino will build me a steel fully like the one below that Ferrum Bikes used to sell with a shock yoke to get a tiny bit of progression out of the suspension. 

My question is, has anyone ridden a Marino? I'm worried it would be too flexy for a 55 pound ebike (even though I love steel/ti flexy frames). 

I know that @CascadeComponents will say anything with less than 30% progression is unrideable, but I need to keep this cheap as its more of a proof of concept. 

I wouldn't necessarily say anything less than 30% is unrideable. I mean the Stumpjumper 15 is rideable and that's all of like 12% or 4% if it's a 27.5 rear wheel. That said, i actually maxed out the IMU in the BYB at 16 g when testing the stock Stumpjumper.

Compression damping was invented recently...