Home Made Bikes

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flag R-M-R
Posted: Jan 4, 2020 at 13:57 Quote
Meet me at the plaza downtown and let's hit the stair set. #freerideaintdead

But seriously, that's a high instant centre, though it does drop quickly. Direct drive or idler?
flag ajax-ripper
Posted: Jan 5, 2020 at 1:05 Quote
R-M-R wrote:
Meet me at the plaza downtown and let's hit the stair set. #freerideaintdead

But seriously, that's a high instant centre, though it does drop quickly. Direct drive or idler?
The linkage and rear triangle seem to be from a zumbi f44
flag R-M-R
Posted: Jan 5, 2020 at 1:40 Quote
ajax-ripper wrote:
The linkage and rear triangle seem to be from a zumbi f44

Good eye! So, no idler.
flag DanAlmberg
O+
Posted: Jan 5, 2020 at 8:59 Quote
Yeah Zumbi f 44 on idler just a ss tentioner. Now its all done with the hope M4 on and a chain so just need some time to get out end test it Smile
flag ThoBoe
Posted: Jan 6, 2020 at 4:35 Quote
Bigtiresrbetter wrote:
It's not a full frame yet, but I'm starting to get excited! This is the bottom bracket junction of a gravel bike frame that I've been working on for a while now. It's compression molded out of fiberglass for now, and I'll re-do it in carbon fiber hopefully in the near future. This part was made in 3D printed molds using a removable 3D printed core material.

Bottom bracket junction molded with removable mandrel

Bottom bracket junction molded with removable mandrel

Bottom bracket junction molded with removable mandrel

Bottom bracket junction molded with removable mandrel

Fiberglass plies for a 20 layer mandrel layup of the bottom bracket junction

Looks nice, i want to work with 3d printed moulds aswell, which material you use for it?
flag Compositepro
Posted: Jan 6, 2020 at 5:57 Quote
R-M-R wrote:
jgmu97 wrote:
That was why I also asked about how deeply builders analyse the structural performance of their frames. Yes FE analysis would give you an idea of frame stiffness and you could optimise stiffness with tube profiles etc, but there’s still going to be compliance in the system and the likelyhood is most frame builders won’t have access to that level of computer program anyway.

I’m guessing for dampers you’d need to get a custom tune where the damper could be run on a dyno which is again out of reach for most one-off builds?

Seems like the best approach is experimenting out on the trail with fork/damper settings and tyre pressures.

Standard practice for designers is to just do the surfacing of the bike, often with little to no FE, and let the factory handle the lay-up and wall thickness. A particularly low-effort design firm once told me "we just draw whatever looks good and the factory sorts it out with lay-up". This firm has done only road bikes for the past decade, where the double-diamond shape and rigid frames are nearly impossible to thoroughly screw up; when tasked with doing a mountain bike, their incompetence forced me to take over the detail work and dimensions of the design, which I normally don't do.

Although this represents the lower end of the spectrum of competence, it's not completely unusual and illustrates the extent to which the industry is just guessing. Marketers create an image of teams of top gun engineers doing countless FE simulations to perfectly tune their precision machines. This is marketing, not truth. As an example, look at the weights of frames within a category and you'll find frames with comparable materials that differ in weight by pounds, yet the failure rates are completely independent of weight. Bikes are nowhere near as refined or optimized as they're made out to be.

At best, a modest amount of FE is done, and many companies do none. Those that do, rarely have a specific target in mind; they're just looking to smooth out the stress profile by reducing the worst hot spots, not unify the flex profile and tune it to achieve some known, ideal value.

A bit of CFD may be done for high-end road bikes, but again, some of these accomplish about as much as an F1 aerodynamics team could do over a lunch break.

I once did a job for a firm making forks they wanted less weight in their carbon schedule 25 g of that was telling them not to use as much glue honestly some of these places make trash
flag junipercycleworx
O+
Posted: Jan 7, 2020 at 3:42 Quote
@ThoBoe I still using PLA for the molds believe it or not. I've messed around with some of the composite filaments (PETCF AND PA6CF) but found them difficult to reliably print large parts with, and they're expensive. I'm using a room temp cure epoxy system so the low glass transition temp of PLA isn't really an issue.
flag rideonjon
Posted: Jan 7, 2020 at 11:02 Quote
Hey a question for any Canadian builders out there ,where are you getting your brazzing rod and flux from.

I can find some 3/32 rod at airspruce but i can't seem to find the appropriate flux.

Thanks in advance.
flag aks2017
Posted: Jan 7, 2020 at 13:15 Quote
Plugging away. Taking my welding course this spring/summer, so I'm hoping to do my frame at the end of it. I need to get the chainstays figured out, and then I'm onto the jig. Only new components I'll need at first are a bottom bracket, headset, and hubs. Whole build will be XT 1x11. Short physical seat tube to accommodate long dropper. Yayyyy...
01 07 2020 progress on frame design. Redesigned seatstays still need chainstays designed.
flag R-M-R
Posted: Jan 7, 2020 at 13:29 Quote
aks2017 wrote:
Plugging away. Taking my welding course this spring/summer, so I'm hoping to do my frame at the end of it. I need to get the chainstays figured out, and then I'm onto the jig. Only new components I'll need at first are a bottom bracket, headset, and hubs. Whole build will be XT 1x11. Short physical seat tube to accommodate long dropper. Yayyyy...

Exciting project and I hope it goes as smoothly as possible!

A suggestion:

Before building, find a bike with almost exactly the same geometry and test ride it. If you can't find one with the same geometry, find two: one with the same rear geometry and one with the same front. Verify you like the geometry before building. Most first-timers overlook this!
flag shirk-007
O+
Posted: Jan 7, 2020 at 13:35 Quote
rideonjon wrote:
Hey a question for any Canadian builders out there ,where are you getting your brazzing rod and flux from.

I can find some 3/32 rod at airspruce but i can't seem to find the appropriate flux.

Thanks in advance.

I buy from the US online sources (Bike Fab Supply most recently) . Only Canadian source I found had a minimum order qty of 10lbs for GasFlux rod if I remember correctly, it's an industrial supply place in Edmonton.
flag mrti
Posted: Jan 7, 2020 at 13:38 Quote
R-M-R wrote:
aks2017 wrote:
Plugging away. Taking my welding course this spring/summer, so I'm hoping to do my frame at the end of it. I need to get the chainstays figured out, and then I'm onto the jig. Only new components I'll need at first are a bottom bracket, headset, and hubs. Whole build will be XT 1x11. Short physical seat tube to accommodate long dropper. Yayyyy...

Exciting project and I hope it goes as smoothly as possible!

A suggestion:

Before building, find a bike with almost exactly the same geometry and test ride it. If you can't find one with the same geometry, find two: one with the same rear geometry and one with the same front. Verify you like the geometry before building. Most first-timers overlook this!

I have to disagree: The first frame is usually barely rideable anyway... so better build a V2 right away.
flag R-M-R
Posted: Jan 7, 2020 at 14:03 Quote
mrti wrote:
I have to disagree: The first frame is usually barely rideable anyway... so better build a V2 right away.

Okay, sure, but I'm giving him the benefit of the doubt and trying to eliminate one source of problems. In the unlikely event it turns out fairly well, he might as well start with decent geometry.
flag rideonjon
Posted: Jan 7, 2020 at 14:40 Quote
shirk-007 wrote:
rideonjon wrote:
Hey a question for any Canadian builders out there ,where are you getting your brazzing rod and flux from.

I can find some 3/32 rod at airspruce but i can't seem to find the appropriate flux.

Thanks in advance.

I buy from the US online sources (Bike Fab Supply most recently) . Only Canadian source I found had a minimum order qty of 10lbs for GasFlux rod if I remember correctly, it's an industrial supply place in Edmonton.

Thanks Shirk,looks like Bike Fab Supply it is.

Cheers,
jon
flag jamieridesbikes
Posted: Jan 7, 2020 at 16:36 Quote
photo
Follow up to my post over a year ago when I built this. Finally got it finished and I'm very happy with how it rides

853 front triangle
Columbus stays
Paragon bits

130mm fork @20% sag
64 HA
75.3 SA
460mm reach
413mm CS
420mm seat tube
50mm BB drop

 


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