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  1. #1
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    Default Tube press clearance thing... Sketchy, or no?

    I'll get a build thread once I get a little further along, but right now I just made a jig I can put in a press to indent tubing for clearance. I love been racking my brain to figure out a way to really squeeze my sporty engine in a frame i drew up, and part of the solution is pressing in the tubing where the oil drain plug and an adjacent primary bolt are. With it being pressed, do any of y'all think it will lose significant strength since the bend for the rear leg is right next to it. I've had a couple people say they've seen some really sketchy stuff and it will probably be fine, but I figure I'll throw it out to the cc guys as well. I'm not sure if it makes it stronger, being cold worked in, or weaker cause it's near an upward bend.l et me know your thoughts.Click image for larger version. 

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    Tubing is 1" 1020 dom .120 wall
    It will have an x brace to the other side of the tubing a couple inches in front of it, and a couple inches behind where the backbone will attach. The tubing was pressed in with a "metal hotdog" that is about three inches long and 3/4 wide. It's probably pressed in about halfway in the center of the tube and 3/16 on the edges.

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  3. #3

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    (*DISCLAIMER* - I am not a structural engineer nor do I pretend to be)

    That said, my comments are based on observation, anecdotes, and working with motorcycles every day for six years as a builder/flipper...

    I see reliefs/indentations like that all the time in OEM frames...I'm assuming you took inspiration from those yourself. It's wise to have a second thought where personal safety is concerned, but I don't see any instance where you've destroyed the integrity of any of the tubing. If you'd smashed it flat then obviously you'd lose most of the strength in one axis, but what you have done is what I see the OEM's doing on a regular basis.

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    I see no problem.

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    You see a section of 'squished' frame tube under the engine on the stock Sportster frames for certain years from the factory.

    For frame clearance, I have considered cutting out a section of the side of the frame tube where there is an interference issue, 1/3 to 1/2, then welding a piece of flat steel to replace the piece of curved section. This way it is not 'squished' which could distort the tube.

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    I got the idea from the factory evo sporty frame. Theirs is right in the middle of the cradle, and it's rotated sideways since there wouldn't ever be any lateral pressure. I would have liked to have it be a little farther away from that up bend and I'm still probably gonna run it, but I am feeling a bit better about it so far with yalls thoughts on it.

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    Quote Originally Posted by TriNortchopz View Post
    You see a section of 'squished' frame tube under the engine on the stock Sportster frames for certain years from the factory.

    For frame clearance, I have considered cutting out a section of the side of the frame tube where there is an interference issue, 1/3 to 1/2, then welding a piece of flat steel to replace the piece of curved section. This way it is not 'squished' which could distort the tube.
    I was also debating bending that section in solid bar with two solid slugged ends to fit in the rest of the rails and then machining the 3/16" out, but I'm not super savvy on a mill and I'm really liking the looks of the indentations, looks like a factory idea

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    Depends on HOW you do it, But I have seen many frames with notches, dog legs and flat spots, Slugged inserts with holes drilled up the tubes and danish welds * to spread the load besides the lap-Butt weld where the tubes meet.

    (I used to work for an aerospace company and we had engineers who studied this as well as a world class welding program, I am NOT a welding expert, but I know many who are. I am also a certified NDT-FAA inspector and using tech data, certed a lot of parts.)

    * So what I call a Danish weld, is you drill holes in the tubing and slide the slug inside. You tack it, and then purge the tube with gas, Nitrogen or if you are fancy a Helium-Nitrogen cocktail, Then using TIG you tack each hole, and the butt to hold it all, and keeping gas flow high and oxygen free, you weld up the holes first. The holes should be a 45 deg bevel with a 5 thou land at the bottom. You start your weld in the center and circle the hole round & round filling it and walking the bead up the sides of the beveled hole and when you are done, your stacked dimes beads should look like a danish. Leave it a little proud of the tubing so any dirt or dross floats to the top. When you grind it smooth, take off that 10 thou bead and all the contaminants with it. Stay on TOP of the weld and dont dig in on the sides as, you will leave a ring if you do, and that will be the failure point if its stressed.

    If you do this right, hardly ANY heat or distortion. The key is control your torch heat and with the purging and gas, without oxygen the temp will stay low so no work hardening, Hydrogen or carbon embrittlement and that welded up section will be stronger than the rest of the frame.

    But back to the topic of BENDING a frame.. I have several BSA pre unit singles and can take more pictures if you like, But here is one I just slurped off of eBay to illustrate. The BSA PU singles use basically the same frame as the twins but they use a jig and dog leg the lower frame tube to clear the singles oil pumps. This frames got some war wounds but it shows it perfectly.
    I have a Twin frame I am repurposing for a race bike and making a similar jig and using our new log splitter which has a 37 ton hydraulic ram. Should be really exciting when I try it. ** Will practice it a few times first.
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    Right now I only have a simple mig set-up, but that is really interesting. I've always heard to bevel the edges of your slug ends as well to eliminate stress areas too. I've been scouring the web for other pics of the indentations, but haven't really found much of ones that are in the vertical plane, as opposed to in the "sides" of the tubing. I don't know anything engineering so I've wondered if since the tubing is pressed back into the tube, if it really alters the strength at all?

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    Unlike extremely delicate vintage Britbike (Gold Star, Commando etc) frames, Sportsters are built for abuse and good basic welding practices are amply strong. MIG is fine. The frame was wire welded in the first place and all related WPS blessed by the engineers were for wire welding. If in doubt about any weld you intend to make, duplicate it on clean scrap then cut coupons and bend test 'em. Pipe and structural contractors use bend tests when hiring because they are reliable, quick and easy. See welding forums for pics so you get the idea. Every hobby weldor should make testing a habit like the pros do. My pipe weldor instructors stayed in practice by testing more than necessary for student demos and many weldors bend test at home on the thickness and material they'll be hired to weld.

    A modest press fit (~.001") won't bother anything. Beveling slug end edges makes them easier to insert. If you have questions re:induced stress by slug edges post on a welding forum and let the experienced weldor/CWIs weigh in. (It's possible to pass the CWI test and not be a kickass weldor. I've known some examples who got their CWI shortly after we trained them and with very little field experience. It's nice money though!) Bikers have been safely slugging frames with by stick and torch welds (and brazing, also used by the factory to assemble frames) long before hobbyist MIGs were common. HDs aren't heavy and crude by accident. That's why there are so many survivors compared to contemporary brands. Work clean and get good penetration and you'll be fine. Cold welds are the enemy of hobby MIG weldors.

    BSA used some thin tubing on those Gold Stars. Like Commando frames they dent if you look at it funny but lighter frames were one way to compensate for heavy drivetrains and lack of horsepower. Beautiful two-wheeled art though and they sell for big bucks.

    So what I call a Danish weld, is you drill holes in the tubing and slide the slug inside. You tack it, and then purge the tube with gas, Nitrogen or if you are fancy a Helium-Nitrogen cocktail
    Nitrogen purge for carbon steel is rare these days. The modern standard for many years is purging with your (typically argon for carbon steel) shielding gas. Most affordable, maintainable and convenient regulator setup is two flowmeters on a CGA 580 tee rather than a dual flowmeter because when one side of a dual has a seat failure or gets bashed in the field they cost more to rebuild and you have no flowmeter unless you bought backups. If one flowmeter fails ya swap it out and press on. We assembled all our training TIG rigs that way.

    This is a decent price, and try to avoid buying anything but gas and filler at your local welding supply because the usual markup is high:

    https://www.amazon.com/CGA580-Male-F.../dp/B00263YVS6

    Nitrogen was apparently popular before argon was affordable and still has specific uses:
    https://app.aws.org/forum/topic_show.pl?tid=14333

    https://app.aws.org/forum/forum_sear...ax=&order=desc

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