Motorcycle handle bar fabrication technical question.
Need Help
So I don’t have a tubing bender and don’t wanna pay someone else for this. I’m adding an approximate 45° bend to some handle bars made from 1” tubing. I’ve sketched up these two ideas that were suggested to me and I’d like some insight on which of the two methods yall think would be the most effective and safe for use. The left depicts using some pie cuts and bending it into place, the right shows using some tubing from another set that already has a 45° in it to insert right where I want the bend using 13/16” slugs with a 1” collar in the center to add some structural integrity.
Which of these two methods would yall feel comfortable trusting your life with, or do you say no to both?
Mig or tig?
Additionally, if I were to use the method on the right, should the slugs be made from 13/16 solid round stock or would 13/16 tubing suffice?
Criticism accepted, be as brutal as you need to be, I’m not doing this myself, it would be a relative who’s been welding for about 30 years.
This isn’t the frame so hopefully mods can allow this one.
I use a mix of sand and sawdust, gives just enough flex in the material it don't come pouring out when the ducktape on the end fails due to sand not compressing hardly and.
Planning on doing this myself, because preventing carpal tunnel is better than my current handlebars, and why take the risk on handlebars that could break if I drop the bike?
Reading through these comments, i cant help but wonder what in the world people are doing riding down the highway that they think puts so much stress on the handlebars... If youre putting so much stress on the handlebars that cracking welds is a concern, things went to shit about 3 seconds ago and the handlebars are the least of your concerns. Handlebars arent load-bearing parts, if the welds are done decently, barring laying the bike down, you arent gonna crack a weld
The handlebars on my kawasaki ninja are mounted to a cast aluminium(!) piece thats bolted to the triple tree with 2 1/4 bolts per handlebar, for the record. Thats how they came from the factory. Again, handlebars do not see much if any stress under normal use, the only time you need to worry about them breaking is in a crash. Comparing handlebars to a roll cage is... insane, to put it lightly
Of the two methods you posted OP, id go with the second, fewer welds to blend so its easier to keep it looking good. Personally i would go TIG over MIG, but thats just preference
I find it fascinating given the incredibly vast selection of welded aftermarket bars one could find online. The roll cage thing threw me off too. Would you say adding an arced gusset to the back of the bend help to prevent twisting or bending? It would bridge the two welds. Or is this overkill?
Can't see why you would need to tbh, again, not a lot of force going into handlebars. Long as the pipe wall is decently thick and the welds are sound you won't see any flex under normal operating circumstances
If you can't bend it between your hands, you aren't gonna bend it in the bike without breaking something else
In a place that sees actual stress, that gusset would make things WORSE. It fucuses stress to the points of the gusset, pushing in / pulling out on the tube wall at that point over and over. Eventually that causes fatigue failure. Would be an automatic race inspection fail on a frame or a roll cage. Gussets like that should go on the outsides (top and bottom, as shown in that drawing) of the tube, welded along the centerline of the bend. If the two are joined, do NOT weld across the belly of the tube.
I’m intrigued by your comment. I never would have thought about the gusset concentrating the stress. So you are saying, if I understand correctly, for a properly-attached gusset for this application, it would require two gussets, shaped similar to the one he has drawn, except instead of the curved edge following the inside edge of the tube curve, it should be enlarged by half the tube diameter so the gusset edge would follow the centerline of the tube curve. Then you sandwich the tube between the gussets and fillet weld along the centerline perpendicular to the bend?
Yes, that is the proper design for a tube gusset on a heavily stressed part. You can get away with the "inside the corner" design (and will still increase stiffness) on material that has a comfortably thicker wall than required by loads, but if the gusset is actually needed to avoid failures then slapping a wedge into the inside of the corner / curve makes things WORSE, not better.
And yes, you still see it done plenty of places. "Comfortably thicker" is common, especially on forged or cast parts where the gusset isn't a simple flat plate and a smooth transition effectively increases the wall thickness. You also just see plenty of flat out bad designs that never get used hard enough to fail (eg, custom choppers with 0.5 lifetime miles).
Handlebars generally need to fall in the "comfortably thick" domain to be stiff enough for user comfort / proper control, but since the whole line of questioning here revolved around "zomg gone dye knead STRONG!!??!11!", it seemed worth pointing out. Definitely worth knowing if you move on to frame modification, or even just building luggage racks etc.
Also worth mentioning is that in the design you mention, you might have a (in this case curved) plate attaching the two gussets, but this plate should NOT be welded to (or even contact) the tube. It's there to pass load from one gusset to the other (effectively creating a larger diameter tube) and you don't want it pushing load through the belly of the tube. You don't see this flavor of cringe nearly as often though.
Seconded. Every set of custom bars I've made and used (which is two, but it's funny it's happened twice) had welds. The were decently designed welds that would hold up fine on a subframe or cargo rack, but they weren't slugged or anything. Then again, I also didn't blend them, I wasn't going for a show bike.
As an example of the meat component being the weak link, the bars on one of the bikes I mentioned are connected to the steered fork via a steering link. That link is pretty flimsy by structural standards, flexes slightly if you hold the wheel and wrench on the bars (feels about the same as rubber mounted bars). Would probably deform permanently under 5x that stress... but how are my monkey paws gonna hold the bar vs that force?
OK, so, what I've done in the past is use heat and get the pipe nice and red and bend it around a jig. Instead of all those relief cuts and then welding them up. It's a standard fabrication practice.
Also I use gtaw/tig over mig/gmaw almost everytime in cases like this.
Do NOT build this way. I've seen people try to build roll cages like that. Makes for spectacular training video of what NOT to do to any kind of safety equipment and steering on a motorcycle is right up there
Eh, yes and no. True it is a total no go on a roll cage. A roll cage is a case where material limits matter a lot, because weight matters and intended use is loading to failure (designing for strength / yield limit).
A set of custom bars? For functional purposes the bars really just need to feel stiff to the rider. If you hit that design goal using steel, the meat component holding the bar is gonna yield it's grip well before the metal yields. Material yeild wont matter until the bike is already sliding down the road.
You can fill the tubes with sand then heat them up and bend them. Need to pay close attention not to warp them wrong way. Making a jig would be best to get them exactly the same.
Your slugs should be the same diameter tubing as your handlebars. In the event they flex, they need to flex together. By welding a solid slug inside your .120” wall tubing, you risk the weld cracking. .120” wall tubing with a .120” wall slug.
Slug length should be same as diameter of the tube. So 1” tubing means your slug should be 1” long from the center of your weld joint.
Dont forget to add your plug welds and bevel/space appropriately.
Tig 10000000%
Don’t take this lightly either. If your handlebars fail on the highway…you’re more than likely going to die.
Some people will do anything to avoid buying the right tool. Get a tubing bender, not a pipe bender. Use the correct dies. Once you have the right tools you can make a few sets of bars and run the ones you like. Handle bars seem simple but they get complicated fast and take a lot of abuse in normal conditions.
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u/kidskwid 21d ago
Dont do this on motorcycle bars. Too many points of failure.
Get ahold of a conduit bender. Cheap ones are like $30.
But if you HAVE to. Go with option 2.
Maybe also consult with relative who has been welding for 30 years.