Mountain Bike Reviews Forum banner
1 - 20 of 25 Posts

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #1 ·
Hey team. As some of you know i cracked my beloved Rocky Mountain Slayer by massive over clearing of a step up.

I got an insurance payout and bought a replacement Slayer and so have ended up with the old cracked bike. I decided to repair the frame stronger and heavier than before and build it up into a park/dh slayer.

Here's the repair journey.

Initial crack discovery.... Bummer!
Yellow Rim Bicycle tire Spoke Bicycle wheel rim


Frame pull down and crack propogation identifying
Bicycle frame Bicycle part Bicycle accessory Bicycles--Equipment and supplies Bicycle


Carbon trimming and layup development. 600 gram uni directional used.
2 layers spiral wrapped sleaving the crack. One layer full length top tube. This will give me torsional strength, plus extension and compression strength. Extending the repair fill length of the top tube will add more strength than the original design.

Black Tool Bicycle part Kitchen utensil Household supply


Dry wrap, mask area.
Musical instrument accessory Shelving Shelf Household supply Cleanliness


A couple of hours of fasdidious sanding back to raw carbon.
Visual arts Paint Street art Art paint Graffiti


Crack propogation checking. 70% delamination around the circumferance of the top tube. The repair will essentially have to take all the load. Existing structures are broken.
Plastic Steel Tool Pipe Tool accessory


Hand layup.
Floor Household supply Electrical supply Fish Safety glove


Removing breather cloth and peel ply after curing. Heavy 600grm uni will need some fairing and filling to make smooth.
Motor vehicle Tire Wheel Automotive tire Vehicle


Fairing and filling complete.
Automotive tire Automotive exterior Automotive lighting Auto part Tread


Painted ready for assembly

Bicycle frame Bicycle part Bicycle accessory Bicycle fork Bicycle


Bicycle frame Gas Bicycle fork Carbon


Assembled and ready to ride!
Bicycle tire Tire Bicycle wheel rim Bicycle frame Bicycle part
 

·
Up In Smoke
Dirt Roadë
Joined
·
3,281 Posts
Cool project, well done! You trust it?

Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

They're asking $200, still seems a bit steep though.

Bicycle frame Musical instrument accessory Carmine Bicycle Home accessories
 

·
Registered
Joined
·
520 Posts
Cool project, well done! You trust it?

Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

They're asking $200, still seems a bit steep though.

View attachment 1247618
Both reputable carbon frame repairers state unequivocally that repaired carbon is stronger than original. As far as that frame goes: thats way steep. I bought a much lesser damaged Niner RKT RDO for 1/10th the price.
 

·
Registered
Joined
·
2,427 Posts
Is trust carbon repaired properly for sure.
I have a frame on the way back from bring repaired actually. I would not disagree that repaired carbon is stronger - they are not concerned with weight. If they add 5 layers of carbon, they effectively doubled the amount of material there. That is of course going to make it stronger. The trade off is the frame weighs more than when initially manufactured. (Who cares, in my mind!!)

How many layers of carbon were on your repair?
How did you remove voids? Any internal carbon?

Most repairs will involve internal supports being used to allow compression of the carbon layers (internally and externally). Usually they use an inflatable bladder so they can remove the air voids. This is absolutely important for long term strength and durability.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #6 ·
Do i trust it? Yes. i've over trippled the cabon in the top tube. It is definately stronger than before.

But, what i don't know if there is any designed flex it the top tube. If there is designed flex, i have just removed the flex and created a very rigid member (pun intended). It could created a stress point elsewhere to that could cause failure. My gut say no. There is no designed flex, they are simply optimising the weight of teh frame. So it should simply be stronger.


How many layers? see picture 3. 3 layers of 600gm uni. Note that a typical layer weight for a frame build will be 100 or 200gm. I've got the equivalent to 9x 200gm layers!. I could run the top tube over with a truck an it wouldnt break.

Did i have internal layers on the frame. No that is impractical for a frame repair that is is not fully broken. I used the existing top tube to provide the internal structure and externally compressed the layup by applying peel ply, breather cloth (the old towel you can see in picture 8, then i wrapped the repair tight with cling wrap. The breather cloth absorbs any excess resin and the cling wrap compresses the layers to remove voids.

Essentially i created a new top tube over the old one.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #9 ·
Cool project, well done! You trust it?

Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

They're asking $200, still seems a bit steep though.

View attachment 1247618
That adds another level of complexity. You have to jig that precisely or it will not be aligned correctly.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #10 ·
First ride yesterday back to back with the new Slayer. Its good, rides solid, no flex or noise of any kind. I hit some hard and rough features, some drops to bottom out and all good.
There is no creasing, cracking or shown paint work.

To be honest, if my filling and paintwork job was a tad better and you didn't know Rocky paint schemes you would have no idea the bike has been repaired. I'm pretty stoked really.

Tire Bicycle tire Wheel Bicycle wheel Bicycle wheel rim
 

·
Elitest thrill junkie
Joined
·
39,573 Posts
What did you use for resin, cured at room temp?
 

·
Elitest thrill junkie
Joined
·
39,573 Posts
I use West system with 105 slow curing resin. Been using it for years. It cures at room temperature.
Cool, ill probably be doing something similar, banged up a chainstay the other day doing some service.
 

·
Elitest thrill junkie
Joined
·
39,573 Posts
Got my CF, my resin and hardener. Gotta take a vacation, but when I come back gotta get a respirator and some more sandpaper and my friend that works with CF recommended a ribbed roller to get the air out. Stoked to try it all out.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #16 ·
Got my CF, my resin and hardener. Gotta take a vacation, but when I come back gotta get a respirator and some more sandpaper and my friend that works with CF recommended a ribbed roller to get the air out. Stoked to try it all out.
Talk to your buddy about peel ply and absorber cloth. Then wrap to remove excess resin.
Be very carfull when you sand back the paint, you dont want to remove carbon if possible. Also talk to him about the ideal layup. You want the fibres running in the direction that want the strength.

Buy yourself some paper overalls and disposable gloves, Carbon dust is itchy as all hell and carsenagenic. You dont want to breath it in or get it on your skin, in your clothes.

If you have never worked with glass/carbon before do a trail run first to get the techniques down. Even ask/pay your CF experienced buddy to help you out the first time. Once you mix that resin up you have 15-20 minutes to layup/wrap before the resin turns "green" You need to know what to do and how to react when/if something doesnt go to plan before the resin turns green.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #17 ·
Awesome repair! I take it you work with carbon fiber or at least fiberglass for a living? Or is this just a serious DIY endeavor? Sounds like you did your homework and overbuilt out of safety / caution. If you're still alive to read this, great job!
Haha, Yep im still alive. I don't work with glass/carbon as a day job. But I did manage a glasss/carbon devision in a previous job many years ago. So guess you could call me a serious DIYer with some professional knowledge.

Here's my latest build. A hydrofoil kiteboard. A somewhat harder endevour than a mountianbike frame repair!

Siding Lawn Yard Model aircraft Backyard
 

·
Elitest thrill junkie
Joined
·
39,573 Posts
Well, I don't have pictures of each step of the process, but I sanded down to carbon, laid some opposing helix strips, then put a few layers on top of that, then let it cure. Then went to town sanding it down. Some clear-coat on top and hopefully this holds up. Originally, I had damaged it from a sharp impact and I noticed some delamination on the chainstay. It wasn't visibly cracked, but sanding it down it appeared similar to the sanded down top-tube above, where there appeared to be some underlying delamination. I was in my full-on ebola suit for this and yes, those carbon fibers can get everywhere.

Safety glove Plastic bottle Plastic Glove Metalworking hand tool
Bicycle accessory Bicycle wheel rim Bicycle tire Bicycle Bicycle part
Automotive exterior Synthetic rubber Carbon Shadow Steel
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #19 ·
Well, I don't have pictures of each step of the process, but I sanded down to carbon, laid some opposing helix strips, then put a few layers on top of that, then let it cure. Then went to town sanding it down. Some clear-coat on top and hopefully this holds up. Originally, I had damaged it from a sharp impact and I noticed some delamination on the chainstay. It wasn't visibly cracked, but sanding it down it appeared similar to the sanded down top-tube above, where there appeared to be some underlying delamination. I was in my full-on ebola suit for this and yes, those carbon fibers can get everywhere.

View attachment 1250967 View attachment 1250968 View attachment 1250969
A worthy looking repair.

2 months in and my repair is still going strong. No creeks or growns or any sign of an otherwise awesome repair. I'm using this bike for my super chunk fest mountain runs. Its getting a good work out.
 

·
Registered
Joined
·
2,456 Posts
Discussion Starter · #20 ·
Well we are a full 12 months on from my carbon repair.

How is the long term test going?

Excellent. The bike has performed as expected and is still going strong.

In fact unless you are a perveyor of slayer frames you can tell it has been repaired unless i point it out to them. Even then you have to have 2 slayer frames next to each other to tell the difference.

It is safe to say the the repair is a total success. Plus i get to enjoy the decadence of a 2 slayer quiver.
 
1 - 20 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top