Kevinti

cool kit thanks for posting it! I am not sure your comment about seat stays is totally correct. The compression loads are there. We need to see a picture of the damage to properly assess.

BBB_Adrift

I'd love to be able to import a photo but the constraints exceed my skills!
Without a very good set of photos, you probably would not be able to make an accurate assessment, the damage is not so severe that it stares you in the face. It was only picked up when the bike was put in for a tune-up service and it had a thorough deep clean. In essence, there is a 4-5 linear inch area where there is evidence of some crush damage (or impact damage) and some evidence of fissuration or cracking - all quite fine.

I do hoist onboard the point made that the stay is a predominantly compression piece.

grumpus

I think you need 10 posts before you can upload.

vespasianus

I am not saying that the seat stays are not needed for your frame, but they are not the most critical in terms load bearing. You can fix it at home and it will be fine. Also, watch the video and listen to the engineer from Cervelo not the buffoons on this site.

vespasianus

The UCI dictates what bikes can be used for racing. They must have a specific shape - which is a traditional triangle, which is why you no longer see tri-bikes for time trials. The difference between a tri-aero bike and a UCI legal aero bike is huge.

Bike manufactures make bikes mostly to adhere to the UCI rules, as that sell bikes.

vespasianus

Sure, I am going to listen to Yan on a bike forum, who claims to be an adult with a job over a bike engineer. I seriously doubt that and if I said you were an idiot, well, if the shoe fits. Another to the ignore list.

veganbikes

That first part is generally correct the UCI does dictate what bikes can be used for UCI competition. However probably the biggest sales for most companies are hybrids and more comfort orientated bikes which do not have to follow any rules and aren't used in UCI competition so if not having seat stays was so excellent and so unneeded why doesn't the Trek FX or Specialized Sirrus or Giant Escape all have them? Also again if they are so unneeded why did Rob English who makes really excellent bikes and is someone I want to own one of their creations really not have any seat stay-less bikes?

No need to hide behind the UCI because most bicycles used and sold in the world are not for competition. We can look at the Flying Pigeon who has made over 500 Million PA-02 bicycles which are all a pretty standard shape and not all because of the UCI as they are utility bicycles and that is what they are known for and beyond that make a huffy like assortment of stuff and I don't think are sponsoring any teams in UCI competition but they do have road bikes or what they consider road bikes.

If they aren't needed there would be a load of bicycles without them but as we know the real reason they exist is because they create a stronger structure as triangles are one of the strongest shapes. It has nothing to do with the UCI it is just a strong shape and makes for a better bicycle.

I would also be careful supporting the UCI they did give their highest award to a quite authoritarian leader. It was reported in CyclingTips.

vespasianus

Can you point to the data supporting this argument? I think for cheaper bikes, with small BB and poor tubes, their role is larger. But for a modern, quality carbon bike that might not be the case. In the video I posted, the Cervelo engineer states it carries less than 5% of the load - almost within the margin of error of nothing is what he actually states.

And again, I am not stating they play no role, but the load they bear is limited and is easy to fix.

Also, I have no love for the UCI, they like FIFA, are a corrupt organization that ruined everything they touch.

veganbikes

Wait are you disagreeing that a triangle is a stronger shape? That is a new one.

vespasianus

Oh for sure. Aero-Tri bikes have proven that. Their shapes are all over the place and bikes like the cervelo proved that a while ago. Modern triathlon bikes are the stiffest and most aero efficient bikes made. You don't need "seat" stays to make a stiff, fast bike.

I thought the question is how much seat stays contribute in a traditionally shaped but modern carbon bike frame to the frame stiffness. The cervelo guy and people like Rob English and others have said it is not much.

Kevinti

I want to be careful and not upset anyone since I'm new around here but "load paths" are a difficult concept and the reason that math majors make up a high percentage of stress engineers in highly technical fields. A picture from the OP would go a long way in understanding if any "advice" is going to be problematic IMO. I learned a long time ago that being able to post a picture or a video is the only way to properly approach an internet solution. Like I said I am new around here but I am surprised there isn't more push back, from the regulars, against posts that lack the supporting documentation to a "problem". Is this too high of a volume place? There is a lot here, that's how I became interested. Cheers.

vespasianus

No you are right and re-reading the OP's original post, 12 cm is a big area and his method of fixing it is not correct. But it should still be fixable. But you are right, it would be very useful to see it. And again, I am no engineer but when an engineer makes a point, with actual data and has real life experience to back it up, I listen and learn.

Yan 

This is wrong.

A space frame will always be lighter than a single member of the same strength. The bikes you are thinking of, the ones with unusual frames that are without seat stays, they are prioritizing aero. Since they don't have the benefit of efficient and lightweight triangulation, their frame shape has to be absurdly, massively thick to over compensate. They are still light because they are carbon but if these frames went with a regular triangle structure, they would be even lighter to get to the same strength.

BBB_Adrift

It does seem to be the case. I will bump my post count up a bit. no need to reply to this!

BBB_Adrift

Like you - I have been "switched to receive, not to transmit". After all, I posed the question hoping for opinion and solution. In the end, I've taken the conservative option and sent the frame off to what I hope is respectable repair shop (in the Philippines, due to a number of factors). However, someone (not of this forum) has subsequently offered the opinion that I would have been safe going to one of the local fishing/anglers shops here. It seems there is an active trade in fibre fishing rod repairs. I am not convinced though. The object of a fishing rod is to flex; not to prevent flexing!