No announcement yet.

Welding thinwall cro-mo (structual tip?)

  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Glenj, how are you cutting those saddles?
    "four to tow, two to go"


    • #17
      Belt Sander...

      I used to use bi-metal hole saws but found the course teeth would catch on the hardened thin wall tubing. I made a mill spindle mounted belt sander instead. I have a selection of drive spindle diameters to give me whatever size joint cut I need. The only pain using it is draping the mill in plastic before I use it to keep the grit from damaging the machine. I now have an old small horizontal mill I'm going to dedicate to a tube cutting sander.


      • #18
        Glen, a friend made a similar "different ODs of roller" stand-alone belt sander for making motorcycle frames.

        If it is a 90* or other easy angle I'll use an appropriate EM in the mill (this presumes a standard 3/4, 7/8, 1" tube butting on another standard tube, not a small tube going into a 2.5" OD headstock). I made some rectangular blocks to hold the tube in the vise so it doesn't crush it but does hold it securely. That's just a simple bore to size and slot on one side. Put the slot "up" and the vise will pinch it shut nicely. With a good fit in the block there is no problem taking it out of the vise and swapping it end for end as there is plenty of friction to hold the block in place. I suppose you could drill and tap for a pinch bolt but it has never seemed needed.

        You do need to watch that the EM doesn't grab the side of the tube at the very end and fold it over. What I found helped avoid that is to only feed the EM in to the point where it is just cleaning out the ID of the tube at the pointy-ends of the fishmouth and then stop. If you feed a 1" EM in .500" you are going to have to trim off those "tapering down to nothing" bits on the tube anyway. So just stop in time so the EM can't grab the tube and fold it over.

        The "commercial" tube profilers I see are usually pictured with a roughing EM in them. I've only used regular 4FL EMs so I don't know if the roughing EM is because they are using thick-wall tubing or if it is less prone to grab. If nothing else using a roughing EM would reduce the number of steel needles around the work that are waiting to imbed themselves into your flesh.

        I haven't yet tried using a small OD EM and letting the mill interpolate the circle to see if that makes it less prone to grab and fold.

        With some practice snips and a 1/4 or 1/2 round bastard file will get you plenty good enough. If the tube is too thick to file/snip, it is generally too thick for my frames.



        • #19
          Very Thin...

          The tubing I've been using recently is only 0.020" thick at the ends where the welds are and 0.015" thick in the center. It's also 195,000 psi ultimate tensile strength. Endmills and hole saws just love to catch and mangle this stuff. The advantage to sanding the joints is you don't need to hold the tubing as rigidly as you do for cutting. The forces on the tube are quite low. Also, some of the tubing is ovalized or tear drop shaped so making fully surrounding blocks like you suggested to hold it is much more difficult.

          A roughing endmill I have not tried yet and might work but I can get 3-4 frames worth of cuts out of one $8 belt. On thicker round tubing, un-heat treated 4130 etc you have a lot more choices available.



          • #20
            Nice work!

            Glen, to build a bike frame on your own and come up with 3 Lbs is amazing, my hat is off to ya,,, nice looking joints, is there any concern at all about using sanding belts and contamination of the joint?

            Very cool, iv got a bunch of true temper cro-mo frames that iv gotten from bike shops and will be cutting them up for practice this winter, I know it sounds crude but i will be building my frame and mapping all the angles out on a sheet of plywood, a typical frame jig does not have the needed travel to acomodate what im going to be trying out anyways, thanks for the post...


            • #21
              Originally posted by miker
              Isn't the Bicycle Wheel/Rim a Disc Brake itself? As in the Calipers with Rubber Pads, grab the Rim/Disc.


              Tattomike mentioned that "nice ones have disc brakes" and you made the above statement,

              Im in agreement with you -------- when you stop and think about it the typical V braking system IS a Disc/caliper system, and in my books its superior to an inboard disc, for one you can get ceramic coated rims now and run very hard pads so the worry about to much elasticity in the system is eliminated, two --- you have a "rotor" with aprox an 11 to 12" radius, Thats far bigger than any race car I know of and far larger than the internal 2 or 3" radius disc's for bikes, This large radius not only gives you unbelievable stopping power, it equates to massive amounts of control, some of your best trials Mt. bikes still run the V brake for this reason... Last but not least, the inboard disc superloads bicycle spokes, It torsionally twists the hub from the rim, thats a fuqe --- so bad that the early ones were snapping and disintegrating the entire wheel upon heavy braking until the engineer's finally figured out they better increase thier hub diameters (DUH +=more weight) I dont need any more stress on my wheels and spokes, last but not least the inboard disc sytems are extremely heavy, im already carrying my rotor,why not put it to use? and as far as the V brake component its still way lighter than the inboard caliper,

              The advantage to the inboard --- they work better in the rain, I could care, I live in colorado plus they make "wiper pads" that clear water and mud away, if i get caught in the rain it does effect my stopping power --- the solution is I just clamp down a little harder on my levers....

              One last note, i stop my bike with how a wheel is designed to work, its basically the same type of tension that a wheel see's while rolling, inboard discs utilize half of the spokes in the wheel (the other half go limp) to not only create more elasticity in the system but also increase the internal loading of the rim and aid it in collapsing --- the result is you will see far more "tacoe'd" front wheels if someone hits a massive bump under heavy braking loads, Inboard discs are junk on a bike --- but thats just my humble opinion...
              Last edited by A.K. Boomer; 08-24-2007, 09:56 AM.


              • #22
                I'm a little baffled about the extremes of frame construction. It makes sense to reduce weight for any racing apparatus be it bicycles, rowing shells, or jockeys but isn't there some point of diminishing returns?

                There are many variables affecting the outcome of any race. In bicycle racing there are rider variables like physical conditioning, state of health at the moment, rider response to weather, course, competition, psychological factors (placebo effect over a new frame is but one) etc. Then there are bicyle variables like tuning for the course, tires, weight, ergonomics, etc. Also there are bike rider interactions, strategy, teamwork, execution, ect. All this makes a long list of variables that have to be considered and provided for - many of which can trump the effect of a gram more or less in the weight of the bike frame.

                Seems to me chasing individual grams at such trouble and expense passes the point of diminishing returns. It's not the lighest bike that wins races consistantly, it's the most effective bike/rider combination; one that's well nourished, well tuned, well trained, well prepared; who is guided by the most effective strategy and is quickest to exploit opportunities that wins.

                Has anyone studied this aspect of the equation? Are the bulk of bicycle ethusiasts focusing on ever lighter stronger frames to the neglect of other variables that each or severally might have a greater (but less quantifiable) influence on race outcome?

                I recall a local fellow who had me build him some fittings for his bike rack. While we was waiting he spoke of his favirite topic bicycles. In the meantime he swilled about a gallon of coffee from a thermos he fetched and glanced feverishly at his watch until the time finally came when he could have a smoke. I said nothing but the image lingered. Here was a guy driven by the need to excell by racing bicycles yet he was hag ridden by caffine and nicotine addictions both known to reduce physical performance.

                A reduction of bicycle frame weight is readily objectified and quantified. The assessment and quanfification of the many other variables are not. Is it possible that pursuit of frame weight reduction has been substituted for a far more productive but exruciating task of coping with ever-shifting variables?
                Last edited by Forrest Addy; 08-24-2007, 01:58 PM.


                • #23

                  I suspect you're completely right, but what we're seeing is some of the interesting human dymamics that keep life from ever being boring or predictable.

                  One factor, the guys on the bikes in the race aren't typically the bicycle builders. If I'm interested in bike racing, but really don't have the physique or whatever to race myself, the next best thing might be to build bicycles for the ones who do. And since fitness, aerobic training, (drugs) etc, aren't relevant to my particular discipline, I turn to what I can have control of - obsession about the physical machine.

                  The next factor is the racers or team managers themselves. Since there are so many things that go into winning, including just luck, good or bad, they might as well try to cover as many bases as possible to reduce the number or things they can't control. Which in this case gets to be like snapping your fingers to keep the elephants away. You mean there aren't any elephants in 300 miles? Must be working pretty well. So the combination of obsessions and superstition translates into $1000 for those next few grams.

                  In other words, if you just came in second in the race, and all the other factors seemed to balance, more or less, but you were a cheapskate and spent the $1000 in the team budget on say a trailer instead of the more expensive but only marginally lighter bike, wouldn't everybody just kick you? Kind of like the aphorism in the IT departments that no one ever got fired for buying IBM. So, they just spend the money if they can because no one can ever prove that it doesn't help.
                  "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill


                  • #24
                    Originally posted by TGTool
                    In other words, if you just came in second in the race, and all the other factors seemed to balance, more or less, but you were a cheapskate and spent the $1000 in the team budget on say a trailer instead of the more expensive but only marginally lighter bike, wouldn't everybody just kick you? Kind of like the aphorism in the IT departments that no one ever got fired for buying IBM. So, they just spend the money if they can because no one can ever prove that it doesn't help.
                    Let's examine that last line... Let's say you are in a 100mi MTB race, loop race so elevation loss=elevation gain... say you average 10% grade on the loop you do 5mi of climbing or (5280*5)=26400ft. Let's say you carry an extra 1lb of non-rotating weight... you have expended an extra 26400 ft-lb of energy, just looking at the change of potential energy without taking any recovery on downhills. Converting to nutritional calories you burned an extra 8.55 calories to lug the weight up the hill. Let's say rolling resistance, and hammering out of the saddle with the weight shifting around doubles the figure, I have no idea if this is close. We are at around 17 nutritional calories.
                    Suppose the race was 6 hours long.. 52800 ft-lb=9.94 watt-hr, so your rate would be about 19.9/6=3.32 watt. I don't know a lot about putting this in perspective, maybe someone here would? Is this significant? Am I way off?

                    Oh, and on topic, I know reynolds has some really good information on their website for various tubesets and recommended welding procedures.


                    • #25
                      Weight is a "perspective" thing, their are many many variables, Iv seen many many "racers" that were counting the grams on their bikes when they should have been counting the pounds on their bodies, We call those guys Techno weenies, they either have to much dollars and not enough sense or just plain dont get it, The best one liner that shuts them up is "you still gotta peddel em" Iv also seen kids with the heart of a lion on bikes as heavy as a huffy win novice races (not a small feat) Yet Bike weight can be extremely important or in some races not even relevent, Rdesign just pointed out some interesting specs, and it is with the altitude gain that its the most critical, riding on the flats at a constant speed with the best tires and ceramic bearings a few extra pounds is tough to calculate and pin down, Mt bike circuit races that start from a set place climb and then descent and repeat over and over do not always give back the energy return on the downhill from the extra weight because on many of the tight courses your maxed out on speed anyways and the extra energy just goes into the binders, then theres the Table reverse from road to MT. In hardcore Mt biking its the weight that is enemy #1, in hardcore road its the air, there are so many tricks of the trade and strategy in road riding and how to use up your opponent ------ it gets into psychology with major head games ------- if its road climbing enter in both factors to the extreme, same with Mt. bike races that would allow vast sections for stretching out your legs, then theres the difference between wheel weight and frame weight --- wheel weight is twice as difficult to get moving -- and twice as hard to stop -- so when Mt. bikes hit the circuit everyone thought it was like the Mt. road riding and the lighter the better for responce, yet now its found that their is a limit to lightness, After all --- this is also your gyro effect, extremly light stuff can not only disintigrate from underneath you, it can also make your bike to tweeky so you have a DNF because you never crossed the finish line either because your bike broke or you crashed... One thing about running over heavy boulders at great speed is that if your bikes wheels have some beef to them they will not only take the shot ------ they will keep you upright after hitting it --------- cycling is a juggling act, and there are many factors involved, its why I used to show up at a course a day or two ahead of time and ride it, ----------------------- its also why i used to bring about three different sets (style's) of tires to run, depending on the course it was always about how efficient I could go with still being able to keep good purchase on the terrain...

                      As far as what Forest mentioned and frames having to stick to certain guidlines I basically agree with him -- till you re-design the wheel, My bike cranks operate totally different from any other on the planet, so much so that it will allow me to take advantage of some very radical cycling positions, the next couple three years will be interesting to say the least ---- I dont work on them in the summer but make some strides in the basement in the winter, I wonder how many others here have trouble being in their basement when its nice out, Im glad its not my living or i think id starve to death.


                      • #26
                        Bike Weight...

                        The main reason so many people seek the lightest possible bicycle is because it's the one part of the performance equation that can be purchased. You can't buy better fitness or pay someone to train for you. It's hard work trying to generate a few hundred watts of power and takes a long long time in order to be able to do so consistently over hours.

                        As others have said, it's not the best bike that wins the race. It's also not always the strongest rider either. Most of the time it's the person who used what little energy there is available in the most efficient manner, when it was required while using equipment that did not put them at a great disadvantage.

                        Fitness, brains, experience and equipment...that's what it takes to win a race. Oh, and luck, a lot of luck.


                        • #27

                          A.K. Boomer...

                          I clean the tubes quite well after sanding to avoid any weld contamination etc. The 3.0lb frame is made from True Temper S3 real magic involved other than trying to weld it together.

                          I made my own frame jig since the available ones are so expensive. If you have a radical frame design I'm sure you could build your own jig to accommodate it. Look at what's available and start your own...I find it's actually more fun figuring out and building the jigs and fixtures than actually building the frames.


                          • #28
                            Originally posted by glenj
                            Most of the time it's the person who used what little energy there is available in the most efficient manner,.

                            In Mt. bike talk back in the day (and actually quite recently) that person would be Ned Overend, in my books the king of efficiency, Ned was a saab mechanic and got a late start but the late start did not matter as he kicked ass pushing into his fifties, imagine being some new 20 something pro thinking your hot stuff and getting totally "wheeled" by a fifty year old, I remember talking with him at an annual race in durango at a few different occations, he was specialized best PR man as he was very technical and made time to talk... nicknamed "deadly Nedly" and "the Lung" --------- He will always be one of the best minds in Mt. bike racing.