ultraman6970

Hi anybody have done this? Since using carbon looks like easier (but messier), anybody have used carbon to bond an steel frame? Maybe kevlar mixed with carbon?

Thanks.

repechage

Done with Bamboo, the epoxy / steel interface or any metallic to composite structure is always the trick. The question is do you have a good reason to do it that way? At the bottom bracket things are going to get bulky fast.

ultraman6970

Well there is no reason, was just an idea. At least with me, brazing at least now is not an option more than nothing because of the cost of the equipment, i have one set of tubes moving around also and since my master builder is retired i got stuck with them and with the lugs also. So i was thinking in a good way to put the tubes together w/o incurring in high costs, work with epoxy after all is simple (apparently).

After seeing the bamboo bike this guy from brazil just built i thought, hmmm, why not do the same with steel? Little bit of kevlar here and there and some carbon here and there and see how it works out.

The BB can get bulky but if you use a lugged shell it might not get that bad, even the tubes can be glued 1st to the shell then use carbon to give more strength to the frame maybe? The only thing I would change is the front tube and use a 1 1/8 front tube with integrated headset only because is simple and works just fine.

This takes me to another idea, what about a FrankenFrame made of scrap CF tubing coming from 2 or 3 different broken frames? Have no idea if somebody has done this before.

meech151 

Not sure how the carbon wrapped steel frame would work but experimenting is pretty fun, especially if it works. Building a carbon frame out of scrap frames isn't such a bad idea if you can find the scrap, which got me to thinking. I wonder where someone could go to find broken, unused carbon frames. I am always looking to play with carbon fiber and this would be a good way to get some experience. Occassionally on ebay you can find a damaged frame but I am curious if there is a way to find an excess. Perhaps just start calling bike shops or bike companies? Carbon tubes for the main triangle aren't too costly but the rear triangle is a different story all together. Any ideas for locating unused carbon frames out there?

I was just thinking that this may be a whole new business idea, then I just found Ruckus Components online which experiments with broken carbon fiber bicycle parts as well as other things. Check it out.

NoReg

Sounds like it would be an awful bike, heavy and all the downsides of carbon. Makes some sense with aluminum, since you could go to ultralight tubes and get something in the end worthwhile. There are combos that combine the strength of two materials, or the deficits. I this case since you have full strength steel, it sounds like the latter.

Kevlar isn't going to get you anything in this kind of deal, though there is some cheap tow out there that is what it is.

I would consider carbon and carbon tubes. They don't need to be bike tubes, at least the main tubes, and can be reasonably cheap.

I would just stick weld, or bernzomatic braze a frame before I would carbon it.

The cool thing about bamboo is that people go gaga over it regardless of how awful it might be at some level, so just about anything that gets made is OK, but with steel the knives will be out from all sides. Not that it matters.

ultraman6970

Well u can get seat stays and chain stays combos pretty easy in the market, the deal is to get the main triangle coming from broken frames for example.

Well i do have a set of lugs that were made to be bonded with carbon or aluminum, cant remember the bike these came from, the other thing is that bamboo is getting pretty expensive if you are looking for good quality bamboo.

Carbon tubes and scrap MAST carbon tubes are available and can be used, the nice about mast material is that is already reinforced where it needs to be, specially the oval shaped one. Well lets see what comes around at ebay

squirtdad

Cost of brazing equipement was noted...... while not optimum, can't brazing be done with a Mapp/air rig? or worst case the the Mapp/Oxy rig? they are not terribly expensive and maybe cheaper than getting epoxy and carbon if you don't have a cheap source

fietsbob

buy lugs, and precisely miter the tubes , Silver melts at lower T than Brass,
but wont fill gaps, so tubes have to fit in the lugs tightly capillary drawn in to gap

You May have better luck with thin stuff since it all had to be up to temperature before the silver solder
is touched to the hot zone

Fork crowns and BB shells take a lot of heat to bring them up to solder melting point.

ultraman6970

Thats the problem with mapp gass, the temperature is not the optimum but maybe enough to stick the lugs ant the tubes enough or something? In my case i do have the whole set of tubes , lugs and dropouts so i just figureing out what to do with them now, but due to the temp issue im not considering any mapp combination. So why not just basically build a carbon bike but using a steel set of lugs and tubes a frame for it.

Regarding weight why not just taking tongues of steel off the tubes then wrap it with carbon.

squirtdad

This book https://www.amazon.com/Lugged-Bicycle.../dp/1442186305 is about building a frame simply...and it says Mapp/air will work.

as for personal experience I can say that mapp/oxy had more than enough power to easily remove shifter cable stops from a Univega. but those rigs go through the little oxy tanks fast.

ultraman6970

THats the point too, i been reading that for some stuff u really need like 2 mapp/o2 torches to get the right temp like for example a BB,, i don't know if anybody can confirm this??

velosprinter

You will use a whole bottle of O2 for the bottom bracket connection maybe two at $9 each. Be on the safe side and say one bottle for each joint. It goes really fast! As in 10-15 minutes tops. If you go this route use a cheap pencil torch with cheap fuel to get as much heat into things before firing up the mapp/o2. The mapp/o2 will get hot enough to do filets nicely and has the feel of an underpowered O2/Acetylene torch just no capacity in the O2 tank. I am at 6500ft elevation so if you are at sea level that might make a difference. If doing lugs the mapp/o2 would be fine but I would still use a cheap setup for warm up. I tried the Bernzomatic ts8000 that is their hottest/fastest mapp torch and it would not get the brass hot enough at the BB for a filet, I even tried bricks but no go there. I bet it would be fine for lugs however.

BTW I have wondered the same thing about composites and may just go bamboo. If you want to do steel right, plan on a $500 O2/Acetylene torch.

unterhausen

If you are going to go to carbon, it makes the most sense to go ahead and buy carbon tubes.

ultraman6970

Carbon tubes, i found a few places where to get them in a matter of fact looks like make the tubes my self is not that hard also. Found like 3 ways to do it and there is one that is the simpliest. Well still need to get the money to start buying materials. Meanwhile i have my steel tubing in here moving around together with the lugs. Probably i'll get a junk bike and i'll do a test joining tubes using carbon and see how well it works.

I never been a weight fanatic so if at least i get the bonding right in a test it could make my life easy.

I thought years ago to get the columbus Mekano carbon tubes but those are disocntinued, i believe dedaccia is still making carbon tubes, anybody know?

Leisesturm

Another poster who has tried it says Mapp/air and even Mapp/Oxy don't work. Likely experience or, more acurately, inexperience plays into it. If you have experience welding with different kinds of equipment you will spend much less time on a joint than a novice and will consume less gas and distort the frame less with overheating. I have spent most of my adult life being a musician and computer engineer. Lately the urge to build recumbents has hit. Like the o.p. I don't think welding is the way I want to go but I am going to come right out and say that I don't think that a course at the local community college is going to make a professional welder out of me and its one thing to put my own butt on the line but I will be building a tandem and putting my pretty s.o.'s butt on that line as well. The bamboo frames intrigue me but I grew up around bamboo. The dimensional stability and long term endurance of bamboo in a temperate climate does not impress me. I read somewhere though that in terms of tensile strenght and modulus of elasticity and what other terms you guys use to compare frame materials, bamboo and aluminum come out fairly close. I was already where another poster in this thread was with using aluminum instead of steel for the tubes. Where I would differ is in the use of carbon fiber as a lug material. AFAIK there is a galvanic reaction when dissimilar metals are bonded. Apparently carbon fiber acts like a metal when put against steel and also aluminum. Most bamboo frames are lugged with hemp or sisal fiber and, although it is not a look that I really like, I wonder if hemp or sisal fiber in expoxy could not be used to bond aluminum tubes as well.

H

ultraman6970

Probably it will work fine also, well when i get a steady job I'll start buying materials so far i have a cheap idea of how to make the molding for carobn tubes, even a good way to make tubes w/o leaving stuff inside of the tubes. Again, need the money

As for the galvanic corrosion thats an easy way to bypass it, use glass fiber 1st, then continue wrapping in carbon, another way to fix the problem is to use a special paint/glue/paste, you basically cover the aluminum piece with it and no more problems, besides it etch the aluminum for better cohesion with the carbon or what ever u are bonding to it also.

cujet

As I'm sure many of you know, we in the aviation industry are having all sorts of issues with the carbon composite/metal interface. Aircraft generate static as they fly and the result is often rapid corrosion of metal parts. First and second generation carbon fiber composite aircraft parts are being replaced with aluminum parts (it worked out that well!).

The modern composite construction is often carbon/Ti.

ultraman6970

hmm interesting comment

NoReg

Well finally a data point indicating corrosion in some context isn't a myth. I always thought it sounded more myth than fact. And bikes aren't planes.

As far as making tubes, be careful about some of the instructions, they can be 0.45.45 tubes that are not all that longi strong. The ones that are made from tubelar braid. The work for what they work for, but probably not bike tubes at a low weight. Carbon tubes are relatively cheap in the smaller sizes. The biger ones can be cheap, but they are rarely locally available, which is too bad for us yachties.

velosprinter

I can verify that the Oxy/MAPP torch is not a very good setup. I have years of welding experience back some 20 years ago when I worked in industrial industries. The problem is not really the torch but the Oxygen tanks are too small and filed with compressed O2 not liquid. This means that running the flame hot enough you burn through a tank in about 15minutes at most. Using a cheap torch with cheap propane will get your joint up to a good temp and then you can come in with the Oxy/MAPP and do a fillet with no problem. Just figure on one O2 tank per tubing joint and you will not be disappointed. If you are going to do this work on more than one frame get a real torch.

@Leisesturm I am now on the recumbent trike kick and have been thinking how to do a light tandem trike frame, wondering if bundling bamboo would be stronger...?

Leisesturm

Probably, but not very light. On Calfee's website is a recumbent tandem trike done in carbon (they have a bamboo one too I think). I am extrapolating that the tubes have got to be over 4" in diameter. That's one way to get light and stiff but I have to think that 'I' beams would be just as stiff in the planes that matter and the overall weight of the finished trike would be less. BTW have you considered a back-to-back design?

H