Frame Design

Yeah, you won't see me putting them on any of my future designs unless I can't help it. I did a bit of a sanity check after the Vala got criticised for it, and checked all the bikes in my house. My brother's e-bike has one, but it's quite heavily braced in the area. The only other bike we have with single shear bolts had a failure where the aluminium insert de-bonded from the carbon rocker and wrote off the frame, and it didn't have a seat stay bridge either. All our other bikes are double shear, including my Vitus. We got the opportunity to test the new Ghost Poacha, and that has double shear as well.

i love my 2023 Optic. It has a press fit BB and these Vala seat stay bolts. Quit talking about this stuff or else it’ll hear and disintegrate thx

Do it creak tho? Also from what I can tell, the single shear bolts aren't so bad on a regular bike, only on e-bikes or when there's no seatstay bridge. 

Progress is being made on the frame design. I've got it set up to use as many off the shelf parts as possible to avoid the expense and weight of 3D printed bits, and I've got some tubes on the way. I should have a real one in my hands by the end of the year! Some of the bits have taken heavy inspiration from Devlin cycles (check him out he makes some cool stuff) and the down tube elbow has been made one piece with the shock mount to save weight and manufacture costs. I am very proud that the flip chip actually fits an m8 shock bolt, and is even able to hold a shock in both positions!

I've settled into my new digs at uni, and I've been told the uni DMLS printer only works with Alloy so my steel design won't be needed. Bit of a shame, but I'll live, i think I will have to be making my own tubes out of prepreg carbon sheets though. Making my own custom tubes is risky but gives me a lot of opportunities to control more parameters on my build. I'll see how things go from here. 

FYI Tony Foale's book MOTORCYCLE HANDLING AND CHASSIS DESIGN is back in print and available. It's being printed by Amazon books. 

https://www.instagram.com/p/DOqaPjmAkzj/

https://www.amazon.com/-/es/Tony-Foale-ebook/dp/B0FNSQV5WM

It's been referenced as the bible for frame and suspension design. I am keen to finally get my hands on a copy of it. 

Thanks! I just came here to share it after posting on instagram too

highly recommend 💯

I saw your post in IG. I had just skimmed your post and scrolled past thinking "yeah that's been out of print for ages". Then I noticed you had linked to Tony's IG and I scrolled back as I had never seen anyone link to him on IG. On his profile I realized it was back in print. Instantly ordered a copy. 

To carry over a question I posed in the rumours thread to a more appropriate thread:

[In response to the new Crossworx Dash 290 MKII] 

This bike brings to mind an inexperience-based question: What is the appeal of a linked-driven single pivot (LDSP)?  I have owned and ridden exactly one full-suspension bike, and it is a Horst link design.

I know that simplicity is a valuable thing in and of itself, but a linkage brings additional bearings and whatnot into play.  I know that other designs separate braking and suspension forces to various degrees in a way that a LDSP design cannot.  Given that LDSP bikes are still the preference for certain manufacturers in certain applications, though, I know that there must also be positive qualities that someview as outweighing the benefits of a Horst or what have you. 

Are LDSP bikes poppier?  More supple/sensitive?  Do they create cool leverage curves or something that gives a bike a nice ride feel  Can some suspension/braking cross-talk actually be beneficial in some instances?  Is the axle path particularly nice?  What's the pitch? 

To add to the above, I rode with a guy on an Evil Wreckening once, and he preached the Delta Link gospel with a level of gusto such that it seemed he may start speaking tongues. No detailed accounting, though, just 'It's awesome. It's the best at everything. This bike rules!"

What benefits might one realize with  LDSP vs a Horst or a twin-link variant or a split-pivot, etc.?  

Thanks in advance to anyone who is willing to enlighten me on this. Cheers. 

One thing to add when talking about antirise. You mention it oposes the weight transfer. That's true, but only for the weight transfer caused by the rear brake. If you move back and forth, if you ride steeper terrain or brake with the front brake only, the suspension will react freely (both front and rear) to the weight transfer. More antirise will only compress the rear when pulling on the rear brake. 

Not sure how antirise is calculated (in linkage) because there are theoretically two components to it, just like with antirise. One is the axle path component, the more rearward it is, the more the rear wheel will be pulled back and thus into the travel, and the other being the torque reaction to braking, the caliper trying to rotate the brake link forward and thus enacting a torque on the complete suspension system. Depending on the rotation of the brake mounting link through the travel it can rotate forward (more antirise) or backwards (less antirise). 

Theoretically 100 % antirise means the rear squats enough to just oppose the weight transfer. That should mean the suspension should stay around the sag point, ideally. In that regard it shouldn't lock the rear suspension, way more than 100 % would be needed for that. Maybe the difference in feel comes from the fact that a lower percentage has some weight transfer, opening up the rear suspension and moving into a softer area of the suspension curve? So it's not single pivots getting stiff, but Horst links getting soft under braking situation? 

Ah and to add one more thing, the antirise and antisquat are based on the height of the CoG, which then in real life is dynamic. And the designed for height vs. actual height is not necessarily the same as well. 

Excellent points, @Primroz. Since published anti-rise figures (and anti-squat as well) rely on assumed CoG of the rider, you cant really compare them brand to brand, or even within a brand over time. They usually publish a static figure, but its going to change from size to size within the same model too, since most companies have the same rear end and suspension linkage shared aross frame sizes, but of course its safe to assume larger sizes have riders with higher CoG, etc. 

I wish, instead, brands published something like toqure applied to the suspension during braking, and plot that on a graph. Its easy to understand anti-rise if you think of floating brake arms, and how when you compress the suspension the floating link keeps the brake stationary. A Horst link is just a way to use the same links for suspension actuation and to float the brake mount, to whatever degree is intended by your design. 

Sorry to keep ranting, but thats what most these 6 bar bikes are doing, like Intense, Specialized, Knolly, etc: use separate bars for managing suspension curves and managing anti-rise. It would be lighter and even more tunable if they just had 4 bars that only dialed in their axle path and compression curves, and then used a floating brake arm, but that doesnt look cool.