My son grows faster than I can keep up with for a build, so I’m jumping ahead to his first 26” (26/24 x 130mm travel) build. I started posting this thread to ask a couple questions, but figured why not do a build log?
He weighs maybe #75 with gear right now, so I’m guessing #100 at his biggest on this bike. So I’m going with a single pivot, linear leverage rate @ ~3.25.
So roughly 130mm travel with a 190x40 shock.
Current questions:
Does my leverage rate sound appropriate? I want to be able to put air in the shock and have effective damping without a revalve of a “stock” shock.
Sidluxe shock, or RS Deluxe shock? I like the idea of the SID being small form factor, but if it’s a “pogo stick” as I’ve read, then what’s the point?
Design-layout wise, what do you all think about the strength- weight appropriateness of my layout/ tube profiles of the front triangle (see preliminary layout sketch below)? My son willbe doing jumps, laying it down and being a normal kid with it.
Current Tubing Specs:
HT: Custom
DT: 35 x 9/6/9 NOVA bent
TT: 28.5 x 1.25 (1.125 x .049) straight gauge (considering .035 wall…)
ST: 35 x .9 straight gauge
Rear end: TBD, but a mix of 5/8 and 3/4 x .035 wall truss-style swingarm
So far it’s been lots of designing and procuring parts, and I have some design progress to share! Based off of techniques I learned here, I’m creating my first fully functional CAD model of a frame. Lots of my other frames have been 2d sketch only, but I’m pushing a short rear end and find learning more CAD skills super fun! Still need to add a few thing like brake and bottle mounts…
I would LOVE input on tube diameter and wall thicknesses …. My main question is .035 or .049 top tube (1-1/8” dia)? Shock forces are not my forte. I tried to place things to avoid buckling tendencies, and I would like to go with a lighter TT, but still unsure. I am, however landing on .035 straight gauge 5/8 for the rear end. Also any other constructive criticism or questions are welcome!
Locating a short shock, and building a decent quality matched 24/26 wheelset has been a challenge, but I got the parts and wheels built! Shoutout to Chromag for making identical 24” and 26” rims that are actually available! My buddy Josh said they built up really well.
I’m new to this forum and this ist my first posting here.
I really like your design! I also have a son that´s a little bigger than yours and I made a new 26/24” hardtail for him last year. It´s beautifull to watch kids on bikes that really fit them. About your tubeset. I think that you choose the right dimensions. What size will the DT be?
Which wall thickness the TT should have depends on the style you will design the shockmount. If you support it, in length and width, maybe with a tube, youre safe with 0.035” wt. You should avoid stress risers. You could also add a third tube between TT and DT and make a mount that’s much smaller or adjustable/flippable for different progression. This tube would also stiffen up the steering area without making the frontend to harsh. Rocky Mountain executed this design very well with their “Slayer”
Welcome to the forum! Thanks for your input~ That’s cool you did a mullet build for your kiddo, would love to see pics sometime! I do like the idea of the slayer type shock mount- I’ll explore that more as the shock mount pictured was thrown on there to give an idea of the concept I have in mind as far as mounting.
The downtube on this build is slated to be a 9/6/9 x 35 dia. chromoly downtube.
Dropouts are changeable for a longer RC or maybe a 26” rear wheel and I made an adjustable headset cup for more reach/FC. I also changed the XT crank set to 155mm length. The Skareb fork works just perfekt with only 40psi and the Oro brakes are, against their reputation, very reliable so it´s his third bike they´re mounted to.
I think, a Ø35 DT will make the Mollusks main frame a tad to stiff. The butted part is also quite dent sensitive. My sons bike has a Ø30x1mm DT and an ovalized 1” TT, rear end is made from ovalized Ø22x1mm and Ø10x0.8mm tubes and it´s pretty strong. I would use 1 1/4”x0.035” tubing for the DT and add the tube for the shock mount. This will make a strong but compliant ride.
Thanks for the ideas of what tube diameters and thicknesses you’ve used. Your son has an amazing bike to ride!
To be honest, I haven’t thought of compliance too much. I’ve been focused on strength, packaging everything with the geo/ kinematic I’m shooting for, and to some extent weight, but I’ll be thinking about it now!
Thanks for your input~ That’s cool you did a mullet build for your kiddo, would love to see pics sometime! I do like the idea of the slayer type shock mount- I’ll explore that more as the shock mount pictured was thrown on there to give an idea of the concept I have in mind as far as mounting.
