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quality of a frame(15 posts)

quality of a framebm
Sep 10, 2002 9:15 AM
how does one tell the quality of a frame? it's bonding? comparable to other frames?

i've been hearing people lately say they can tell one frame is better than another. but how do you really tell?

i've also noticed that some frames, like my Felt, have 'rough' joints. that is the welds are not really smooth like they are on say a klein. i believe that the felt is a good frame . . . so i'm guessing there's no difference?
re: weldsfbg111
Sep 10, 2002 10:00 AM
I asked the same question a while back, about those welds. The answer was that smoother welds take more effort for the maker to do, but rough welds are no less functional and at least as strong. Smooth welds are mainly for looks (and perhaps ~.00001 less drag coefficient, if you *really* want to get technical).

Otherwise, a search of this forum will turn up some good info about frame quality, especially as it relates to frame material. Here's a few results:
Sep 10, 2002 10:02 AM
My links don't work. Just search Discussions for "frame quality", "titanium vs. aluminum", etc.
Smooth welds don't mean better...Dave Hickey
Sep 10, 2002 10:10 AM
Some builders like Cannondale grind their welds to make them look smooth. Other builders will leave the welds natural to show the quality of their welds. This is not to say Cannondale doesn't have good welds, it's just not a good way to judge the quality of the frame.
That's what I meant by saying...fbg111
Sep 10, 2002 3:13 PM
That rough welds are no less functional and at least as strong. Smooth welds look better but that's about all you can conclude from them.
re: quality of a framepinarello
Sep 10, 2002 10:58 AM
Well let me ask this. What kind of quality control on weld(s,ing) does a Mfg. have? Has anyone heard of a certain mfg. x-raying there welds? Paint can hide crappy welds. I just wonder if anyone is doing this or something else. Where I work we leak test our welds with a helium leak detector. In parts per billion. I would think stuffing a bike full of helium and sniffing it on a leak detector would surfice. Catapult
Excellent article on bike manufacturing in Bicycling July 2002js5280
Sep 10, 2002 12:17 PM
Talks about Cannondale's manufacturing process, very enlightening. I'm not expert but I worked at company whose product used welded tubes for the chemical industry (corolis mass flow meters, very cool instrument!). Nasty stuff you don't want spewing out to the general public (i.e. Union Carbide in India, 1984). I was occasionally responsible for some of the paperwork concerning weld quality, welder training certificiations, etc. and knew the people who worked in that area fairly well. One guy was highly reguarded for his knowledge, only a handful of people like him worldwide.

So in layman's terms. . .One of the best ways to truly tell a weld's quality is to do an x-ray. We had a x-ray facility on site and sampled completed welds regularly. Other metalurgy tests might also be used such as sectioning and using a SEM (scanning electron microscope) to see what happening at that level. We also used a Helium Leak Detectors. I think the idea there is to make sure the weld if contiguous, that is it won't leak nasty stuff out. Since Helium is a very small molecule, it can find even the smallest holes. I don't think the Leak Test has much to do with overall weld strength. While you can probably tell some bad welds visually, I know you can't tell all bad welds from visual inspection nor how "good" a weld truly is. The best way to get a good weld is to have good welders, who are highly trained, pay attention to detail, and have good equipment and materials to work with. It really is an art. I'm sure we must have some weld tech's or metalurgists somewhere on the board who can tell us all about it till our eyes glaze over. That's why they get paid the big bucks ;-)
re: quality of a frameozone
Sep 10, 2002 11:26 AM
There is a lot more to consider about frame quality. The miters, the frame alignment, material and welding. If you want to see a quality frame just look at a MOOTS. I believe they do a triple pass weld and they look perfect. The miters have to be exact to weld the first pass and they constantly check the alignment.

Paint can hide a lot. Have you ever seen a Cannondale with the paint stripped off?
No and I don't want to. Sounds like Rosie O'Donnell naked. nmdzrider
Sep 10, 2002 12:09 PM
Sort ofMel Erickson
Sep 10, 2002 1:07 PM
I stripped the paint from a Cannondale DD60 fork. The welds don't look any different from others I've seen. Maybe I should strip my old R400 and take a gander.
To each his own...NJRoad
Sep 10, 2002 1:46 PM
I've heard different things but some will tell you that a single pass weld is equally as strong, weighs less and stresses the tubing less.
Welds, alignment, geometry, sometimes metal quality.Leisure
Sep 10, 2002 7:35 PM
Most decent welds will do. A bad weld is one that messes up frame alignment. A really bad weld can make hotspots in the tubes, leaving areas where the tube is cooked and/or oxidized through, weakening the frame. You usually can't see it though because it mostly shows on the inside of the tubes. I've seen some frames where this happened on the BB tube or headtube.

Alignment just has to do with how well the tubes line up to the designer's intent. Welding can change alignment a bit, as will the factory equipment used when building the frame. For me alignment is most easily felt in how cleanly the frame tracks and handles. Most frames feel fine when I'm on them really, but some just seem more buttoned down.

Geometry is complicated, but the various aspects of it influence ride quality, handling, stiffness under power, and fit. Geometry changes more between brands than it does between pricepoints, but I think (and this is only my opinion) that when you're looking at better quality frames you can expect that they paid more attention to the geometry, and if the alignment is better the geometry will show through more consistently. Or maybe I'm expecting too much.

Metal quality is usually going to be fine on most road frames, but sometimes you'll get companies running lower grade alloys. Most often this just means they'll build the frame heavier to maintain durability, but not always.
Why welds matter.PaulMC
Sep 11, 2002 12:01 AM
People will often say that what a weld looks like doesn't matter. They're wrong.

The first criteria any weld is judged by is appearance. This is true for the entire welding industry. If you have certified welding inspectors performing their inspections under a variety of codes, such as AWS, ASME, API, etc. their first inspection criteria is appearance.

A poor weld appearance is evidence of sloppy workmanship or lack of experience. Lumpy, bumpy, ugly, uneven, undercut, or porous welds can all fail and be rejected based solely on the visual inspection. The thought process is if the weld looks like crap on the outside, do you really think it's going to look better on the inside? It's an indication of craftmanship and workmanship. If a company allows crappy looking welds to get by, what else are they allowing to slide by. If they took to the time and trouble to train and retain the skilled welders required to make beautiful welds, it probably indicates that they take the time and trouble to ensure that the miters are good, the frame is straight, and the employees care about their work. Notice I didn't say "gaurantees", I said "probably."

Can a poor looking weld be structurally sound? Yes. Can an excellent looking weld be structurally unsound? Yes, but put your money on the good looking weld as being the better bet because it's harder to get a good finished weld (assuming the welder is following a tested welding procedure) if the weld is not internally sound. In other words, many internal flaws are telegraphed to the surface of the weld and reflected in the welds appearance. Look at this link to see what I'm talking about: That shows terrible workmanship, poor weld preparation (notice burned paint so near the welds), and probably lack of experience. You can't hide welds that poor under paint either as shown in this picture:

As mentioned by another poster, radiographic inspection is the best method of inspection welds short of destructive testing. How many bike companies do this I don't know. Radiographic testing is expensive and due to the nature of bicycle frame assembly, may require film interpretation and understanding of joint characteristics not commonly found in other industries. In the industry, radiographic testing is only done on random samples unless requirements demand otherwise (as often occurs in nuclear energy projects and other critical applications) so testing each frame is not necessary, the radiography is just used as a QA process. If you find a bad weld, you test more often.

Smoothing welds on aluminum bikes does make some sense if done properly. By smoothing down the ridges of the weld, you are reducing stress concentrations that occur in the ripples of welds. Smoothing welds is a bad idea if it involves removing, intentionally or accidentally, any of the tubes wall thickness. On aluminum bikes, the good quality welds will have a even, rippled, appearance like a stack of dimes laying on their sides. I'm convinced that many companys smooth their welds just to hide the fact that their unfinished welds may not be very pretty to look at.
From the Bontrager Websitecdnrider
Sep 11, 2002 12:50 PM
An except from an interesting essay on the Bontrager website, for what its worth.

"What about the appearance of a ti weld? The concept of quality doesn't work well in this case either. There are a lot of ways to make a marginal weld look good. It's part of the art. Welders learn how to do it. I know how to do it. It is not a big deal. (Don't worry. It's rare that a truly fatal weld is covered up with a cosmetic pass. That's not what I'm talking about here).

There is very little connection between the smooth, regular appearance of a weld, in any material, and the performance or durability of a frame. In fact, given that a straight frame with minimal residual stress often is best achieved using a weld sequence that requires running beads of relatively short length, alternating about the center plane of the frame to achieve (almost) mirror symmetry in the distortion the welding creates, a slightly irregular weld appearance may be optimal. A smooth weld is not a deception if it is represented as nothing more (or less) than a smooth weld. It is a deception if it is used to demonstrate anything else about the frame."
Sep 11, 2002 6:46 PM
It's always important to consider perspective. My perspective comes from being a professional in the weld engineering field. Mr. Bontrager's is from selling bikes. a "good" welder utilizing proper techniques for starting and stopping weldments can blend the stitches together in such a matter as they are indetectable. Bumpiness resulting from the start and stop of stitch welding indicates poor technique. Poor technique indicates poor workmanship or lack of experience.