Carbon Seat Mast

[cammaysmith]

I'm thinking of building my next road frame with Life tubing and a carbon seat mast but could use some direction as to tubing size, wall thickness. The idea was to use a 31.75 tube with 1.375 x 0.065 steel lugs and sleeve the top of the mast with a carbon tube to 34.9mm so as to fit the majority of seat mast toppers on the market. I was looking at this tube from Rock West but wasn't sure if a filament wound tube would work as most of their bike tubes are uni. The wall thickness is slightly thicker than the tubes they sell to make seat posts so I figure that would be a good place to start. Also does anyone know if 0.065 steel tubing in the next size up will give a proper fit or gap for bonding to the carbon tube, or do I have to get someone with a lathe to bore out the ID a bit.

Thanks,
Cam Maysmith

[Will Neide]

I'm thinking of building my next road frame with Life tubing and a carbon seat mast but could use some direction as to tubing size, wall thickness. The idea was to use a 31.75 tube with 1.375 x 0.065 steel lugs and sleeve the top of the mast with a carbon tube to 34.9mm so as to fit the majority of seat mast toppers on the market. I was looking at this tube from Rock West but wasn't sure if a filament wound tube would work as most of their bike tubes are uni. The wall thickness is slightly thicker than the tubes they sell to make seat posts so I figure that would be a good place to start. Also does anyone know if 0.065 steel tubing in the next size up will give a proper fit or gap for bonding to the carbon tube, or do I have to get someone with a lathe to bore out the ID a bit.

Thanks,
Cam Maysmith

Carbon Fiber Composite Adhesive - Rock West Composites

Under bond line controller is some info on proper gaps. Assuming your gap is OK (I didn't do the math), I usually knock the wall thickness (OD) down to something more reasonable. 0.065 will work, it's just really excessive. I make my own toppers.

[cammaysmith]

Thanks for the info on the bond line Will, looks like I should be using .058 tubing for a .0045 slip fit. I just wanted to make sure I wasn't way out to lunch on the filament wound .12 wall thickness tube.

Thanks
Cam Maysmith

[Will Neide]

Thanks for the info on the bond line Will, looks like I should be using .058 tubing for a .0045 slip fit. I just wanted to make sure I wasn't way out to lunch on the filament wound .12 wall thickness tube.

Thanks
Cam Maysmith

Rockwest has a "bicycle specific section" on their page. Not to say you can't use something not in the bicycle specific section, but it gives a good idea on wall thickness and tube type. I'm pretty sure I use something with a thinner wall, but I can't remember off the top of my head. Probably something in the .06"-.07" wall range is what I used for myself. Depends on your needs and design.

[Mike Mcdermid]

Ive had this thing floating about because other builders were basically asking for help with this but its a butted carbon seatmast with all the specifics you would need to take common size tubes allow a proper blathering of glue and also have enough reinforcement near the seat cluster to eliminate stress risers

its kind of a half and half job because i can use it for some other projects im also working on including a custom fit TT tubeset

first i need to finish chainrings

[jgrano]

Any more updates with this? Thinking of doing the same thing for an upcoming build.

I guess checking out the great work of English Cycles would be a nice start - Irvin’s V3.1 | English Cycles