win a rabbit

what are the real disadvantages of using apoxy on a lugged tube set it the tubes are prepared and mated correctly? frame builders have been using apoxy for all types of applications. is there a super obvious reason i am overlooking?
racking my brain.
xjosh

Joshua A.C. New

Are you asking why epoxy isn't used instead of brazing? If so, I'm curious, too. I'm learning a bunch of stuff now in preparation for building my first frame and I've been curious about different materials and why they are or aren't used. I'm used to building RC planes where there are lots of well considered but odd material choices based on local situations.

I'd speculate that the shear forces in the epoxy would be sufficient to make stress fractures over time, but I'd like to hear from someone who knows better than I.

Nessism

Glue together frames use lugs with much greater surface area than brazed frames. You can not simply use regular lugs and epoxy them together, the joints will fail.

Joshua A.C. New

Who makes such lugs? What are they called?

(I'm just curious about this, by the way. If I have access to a frame jig, I have access to an oxyacetylene torch, but I'd like to know all about the various technologies and techniques)

nitropowered

There have been plenty of glue-together frames in the 80's. They are really heavy

Joshua A.C. New

What makes them heavy? Do the lugs need to be superbig or something?

superhotbug

I build exxon grafteks using hysol 9320 epoxy gluing graphite to chromed lugs specially designed for the application. This is one of a few epoxys that are strong enough to hold up and very expensive, $200 a quart. Weldind, brazing or soldering is far less expensive. If you need lugs, I have extras

NoReg

Nessism is dead on. There isn't any reason why epoxy couldn't be used, it just can't be used with lugs designed for metal brazing.

Lugs are a kluge that has developed into an art form. Today if you want to escape brazed lugs with a steel frame the better alternatives are TIG or fillet brazing. The bigger gain there is unlimited geometry in how the tubes fit together.

Nice bike shb!

Joshua A.C. New

Yeah, wicked wheels.

superhotbug

You haven't e-mailed me on lugs yet, dpowers@harris.com 321-259-4394 graftek lugs, perfect for epoxy

ultraman6970

Do u still have lugs? It would be fun to play with those lugs.

thanks

zonatandem

This is a modern day example of beautiful lugwork, with window cutouts.
Carbon fiber lug joined to c/f tube on our custom Zona tandem.
While this is not 'apoxy' it's a space age glue used in the aerospace industry
Joining dissimilar tubes/lugs materials can be problematic.

superhotbug

e-mail me with your address and I;ll send you a set

MichaelW

Check out the lugs on this Alan alu cyclo-cross frame.
It uses threaded lugs to improve adhesion and for safety. This was the standard cyco-cross frame of champions for most of the 1970s and 80s.

superhotbug

alan frames were under alot of stress due to the lugs having the same exact angle on the bottom steerer tube to down tube for every size frame so when you went small or large frame sizes, the tubes were bowed and I saw a few crack the tubing, also, they had an internal part of the lug that went into the end of the tubing so it was a 2 piece lug.

superhotbug

e-mail me at dpowers@harris.com and I'll mail out a set of lugs, they need chroming which is on these lugs, expensive

danielmramos

There was a guy who built some awesome recumbent aluminum tadpole trikes without welding or brazing. He epoxied them together. The performance was excellent.

https://www.trimakazi.com/

Little Rider

Epoxy has a tendency called creep. When under constant load it will stretch causing your frame to fail.

Nessism

Better not tell all the people riding carbon frames...the carbon cloth material is embedded in epoxy which is what holds it in place. Also, literally hundreds of thousands of frames have been "glued" together with epoxy glue and lugs. Do some research on "Look" and "Trek", both brands use epoxy to hold together their marque frames.

Falanx

This is probably one of the few times you'll find Nessism and me agreeing, but epoxy doesn't creep to any degree worth mentioning. Not until you surpass it's glass transition temperature, the lowest of which in any epoxy system is about 120 degrees C.

The problem is it's brittleness and much lower shear strength by comparison to other bonding joint systems...

NoReg

That's not altogether true either. The gougeons have a notch test that is a standard way of comparing the creepiness of different brands of epoxy glue. They will send you a booklet, or perhaps they have it on their website. They are respected testers of epoxy and structures to the extent that one of their more useful tests was adopted by SNAME. The creep, and failure occurs at room temperature, but it does require a constant significant force, which would be unlikely to occur with a frame assembled and at most times not signifcantly loaded. The GTT on WEST is relatively low due to the room temperature cure. Though it can be post cured.

Falanx

That's the definition of creep, though - constant deformation under constant load. The mechanism of creep may change depending on your materials and the temperature range, but it all falls under that heading.

Very few epoxy-system bonded fibre reinforced polymer structures are under a load that is a significant proportion of that required for measureable creep at ambient temperature. And yes, *all* systems cure at room temperature. Its just that some do it reaaaaaaaaally slowly ;-)

Although its fair to say all polymers are viscoelastic in their behaviour, above *or* below their glass transition temperature, in most stove-cured systems, the actual viscous portion of that behaviour is immeasurable at room temperature. For all intents and purposes they are strong, brittle solids.

maddog17

i remember hearing years ago that some of those earlier Look frames had problems with the tubes coming apart from the lugs in areas that were close to salt water, ie the ocean. something about the salt eating away at the epoxy causing the failure.

Nessism

Some early glue together frames failed due to corrosion in the joints. Fix was to anodize the lugs before gluing to reduce the galvanic reaction between the parts.

I have friends that had some glue together Trek bikes, with carbon tubes, and these people got a reasonable service life out of the bikes. After a few years there was paint bubbling at some of the joints indicating the start of corrosion. Not good. My understanding is that it's common to use a wrap of fiberglass as an insulator of sort these days. Works well or so it seems; failing joints are not very common despite hundreds of thousands of frames on the road.

yellowjeep

i sent you an email and a pm