Dropouts for carbon frames. Who wants some?

[CarbonNeutral]

I totally hear you...I was just sharing what I had learned on my journey looking for dropouts to work with carbon stays . I want to be able to buy some dropouts for these carbon bikes I am making (4 so far) just like I would for a metal bike by calling up paragon.
I think your dropouts look great and I would be all over buying them...again, I was just sharing what I have learned. I know Alu is used widly and I am not opposed to using alu at all. I am no expert, that is why I ask engineers and refrence the ASTM book.
Chris

Well as I mentioned, my preference is for titanium bullets - at least for the chainstays - but really, they could be made out of anything.

I'm keen to get some feedback on the design, so if anyone wants to weigh-in, please feel free.

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[DrByrne]

Hi,

Good to see what you are trying to do here. What are your thoughts about the diameter of the inserts and compatibility with existing tubing IDs?
Have you thought about how long the inserts will be relative to the tubing ID?

Owen Byrne

[progetto]

Why adjustable bullet on the bottom? Should only alter by a couple degrees for most frames.

Well as I mentioned, my preference is for titanium bullets - at least for the chainstays - but really, they could be made out of anything.

I'm keen to get some feedback on the design, so if anyone wants to weigh-in, please feel free.

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[crumpton]

this known issue related to bonding carbon to aluminum is a real one for sure. in the presence of oxygen there is anodic and cathodic activity between the 2 which causes galvanic corrosion on the surface of the aluminium and thus increased chances of decoupling the bond. when the bike industry first starting doing this kind of bonding it learned pretty quickly how to deal with it.

the best thing you can do is decouple the direct aluminum to carbon contact. this is done in a few ways. first thing to NEVER do is co-mold carbon directly to aluminum. if you must co-mold to aluminum, use a glass insulator as the first ply in your laminate. depending on how thin you glass is, you may need more than 1.

better results can be gained from secondarily bonding carbon to metal anyways(at least on my bench tests).

1. good quality carbon is treated in a sizing that is the first step in helping decouple but its not enough. still, don't use junk or old carbon.

2. when molding parts to be bonded to carbon, its a good idea to use glass in and slightly beyond whatever surface area will be bonded

3. unsealed anodizing. preferably t3. this is a special request from your anodizer and is not cheap but shows good results.

4. and my fav, secondary bonding with a thixotropic epoxy like DP420 or Hysol 9430(or is it 9340?) where the bond gap in maintained at about .010" +0/-.003" or whatever you like. the dielectric strength of those epoxies is more than suitable when the bond gap is correct and filled.

happy bonding.

[crumpton]

2. when molding parts to be bonded to carbon, its a good idea to use glass in and slightly beyond whatever surface area will be bonded

correction

2. when molding parts to be bonded to aluminum, its a good idea to use glass in and slightly beyond whatever surface area will be bonded

[Will Neide]

this known issue related to bonding carbon to aluminum is a real one for sure. in the presence of oxygen there is anodic and cathodic activity between the 2 which causes galvanic corrosion on the surface of the aluminium and thus increased chances of decoupling the bond. when the bike industry first starting doing this kind of bonding it learned pretty quickly how to deal with it.

the best thing you can do is decouple the direct aluminum to carbon contact. this is done in a few ways. first thing to NEVER do is co-mold carbon directly to aluminum. if you must co-mold to aluminum, use a glass insulator as the first ply in your laminate. depending on how thin you glass is, you may need more than 1.

better results can be gained from secondarily bonding carbon to metal anyways(at least on my bench tests).

1. good quality carbon is treated in a sizing that is the first step in helping decouple but its not enough. still, don't use junk or old carbon.

2. when molding parts to be bonded to carbon, its a good idea to use glass in and slightly beyond whatever surface area will be bonded

3. unsealed anodizing. preferably t3. this is a special request from your anodizer and is not cheap but shows good results.

4. and my fav, secondary bonding with a thixotropic epoxy like DP420 or Hysol 9430(or is it 9340?) where the bond gap in maintained at about .010" +0/-.003" or whatever you like. the dielectric strength of those epoxies is more than suitable when the bond gap is correct and filled.

happy bonding.

Quick question on epoxies. I've used the 9340 stuff with good success in the past for bonding carbon to various metals, but I've also used E-120HP for other projects and that worked well too (both bike and non-bike related). I've seen you mention the 9340 various times (in addition to the DP420 from the 3M line), but what are your thoughts on E-120HP?

Also, would you recommend using glass bead bond line controllers?

Thanks!

[CarbonNeutral]

Thanks for clarifying the bonding (non)issues, Nick.

Bill the chainstay bullet is currently canted at 7º. My calcs say this is the middle of most stays between 405-425mm. However, this dimension can be whatever it needs to be. Happy for input here.

It's also not 'adjustable' - the dropouts are replaceable, meaning they can be replaced for whatever reason.

[Mark Kelly]

3. unsealed anodizing. preferably t3. this is a special request from your anodizer and is not cheap but shows good results.

If your friendly local anodiser can't / won't do this, it's not hard to set up small scale phosphoric acid anodising. PAA naturally has a larger pore size than is produced by the sulphuric or chromic processes and the surface is more resistant to hydration (which reduces porosity).

The trick is to control the temperature so as to achieve a balance between phosphate deposition and metal etching. If you let it get hot you just get heavily etched aluminium.

[crumpton]

but what are your thoughts on E-120HP?

Also, would you recommend using glass bead bond line controllers?

Thanks!

i'd start by comparing data sheets for mechanical props. i don't know anything about glass beat bond line controllers but can guess what its about. good machining and fit up works well.

[jerk]

Way way back when I was building the first "gaulzetti" frames I was working exclusively with carbon....exclusively as a hobbyist to try to dial geometries before I took the plunge with my aluminum project. DP420 is pretty freaking cool stuff.

[crumpton]

Aluminum doesn't bond well to carbon. Neither does steel. Ti is the best material to bond to carbon. Aluminum actually can corrode when bonded to carbon. Materials engineering phd friend had to explain this to me when my aluminum dropouts I bonded to a frame turned green .

more than you can imagine sets of aluminum drops bonded into carbon stays here without a single failure. many of my frames well over 100k mi. @ 10 years plus. in fact there are probably 1000:1 carbon/aluminum to carbon/anything else dropouts in the history of carbon bike frames with very excellent results.

you are doing something wrong. this discussion is so 2002 it hurts. no debate needed. not trying to be harsh, its just not an issue anymore.

I'd like to recant my curt comment in the last line of this post "you are doing something wrong. this discussion is so 2002 it hurts. no debate needed. not trying to be harsh, its just not an issue anymore." and simply offer my comments further in this thread as help or discussion in resolving the issue you have had with aluminum bonding. Certainly Ti is a good choice for this for many reasons but dont discount aluminum. At this point though the smart money is on carbon/carbon right?

I am sorry if my comments were taken as snark.

[zank]

Sheesh. If that was considered snark, somebody has some thin skin.

[CarbonNeutral]

Certainly Ti is a good choice for this for many reasons but dont discount aluminum. At this point though the smart money is on carbon/carbon, right?.

I think if you can afford the tooling - or are emulating traditional steel methods of attaching dropouts, but in carbon - then yeah, carbon/carbon is the way to go. However, I think 'composite' dropouts have some advantages -

1. Easier to thread
2. Modularity has its advantages
3. It's a marketable difference - nobody will mistake your work for a Giant
4. Distancing yourself from the majors in terms of design is good for the industry
5. Let's face it, CNCd parts are sexy!

I guess it all depends on the style you're after. For me, I like a more traditional look and having something the mainstream doesn't, so for me at the moment, that means something like what I'm suggesting.

[CarbonNeutral]

Design is progressing. It's Summer holiday season here so that as well as some other projects have diverted my attention.

To reduced costs I'm considering them in aluminium. Nick C, which flavour of aluminium would you recommend based on your experience?

FYI weight for these as currently designed is sub 90g a pair, including the bullets.

If anyone with a small machine shop would like an RFQ, drop me an email at warwick(at)gresswelldesign(dot)com.

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[progetto]

Why dual bullets?

[Will Neide]

I'm assuming that the dropout is replaceable in the event it gets bent or mangled? Looks like it would be simple to make a TA version as well.

As a casual observer here, I would think 6 series aluminum would be too soft and bend quite easily. I've bent a few 60xx hangers on my Paragon dropouts. 70xx seems to hold up better for me.

[mcgovski]

Looking forward to seeing the final drop out. I made these recently. IMG_3306.jpg
I do think metal would be better like what you are doing.

[CarbonNeutral]

Why dual bullets?

Replaceable dropouts. If you bend a hanger or want to use a TA or whatever, you just unbolt and bolt and ride off into the sunset.

[crumpton]

Is the Chain stay bullet mechanically keyed to the dropout? I'd recommend that if not. Lest you wind up with a tiny travel suspension rear on that bike.

[CarbonNeutral]

Is the Chain stay bullet mechanically keyed to the dropout? I'd recommend that if not. Lest you wind up with a tiny travel suspension rear on that bike.

Yeah Nick, it's keyed in. It also utilises a chainring bolt so it's also a 'thru-axle' (I don't know the engineering term).