Guidance on frame welding-what are you guys doing?

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by sfhellwig, Jan 6, 2011.

  1. sfhellwig

    sfhellwig New Member

    I was drawn to the site for the motored bike topic in general and while here found several motored "chopper" bikes with quite a bit of fab work. Which got my gears turning to modify my own chopper bicycle in prep for motoring. I have found an "old family friend" who is a highly accomplished welder, he just hasn't ever worked on bike frames before. I thought there was a fab forum but looks like everything but. So please help me to help him so my frame will come out right. If there is a sticky that already addresses this please point the way.

    The bike I am working on is the Jesse James WCC bike. Decent design but I am an adult, not a child. I want to leave the front end alone, stretch behind the bottom bracket/in front of the seat, and raise my bars that I have added. Basically cut the tube and weld in an extension tube. In the projects I have viewed I have seen this done somewhat. Is this strong enough if the weld has good penetration? During our first conversation the welder (Danny) said that he wanted the extension tubing to be able to sleeve and over lap the other tubing. While I'm sure this would be stronger I already have matched diameter tubing from other bike frames. I assume he is just trying to be safe but if I can go to him saying that others have welded tubing end to end and feel safe with it, I would like to do that. If these joints would require additional bracing, ideas would be appreciated. I can live with the asthetics of collaring the joints if the strength is needed but I could see the bike getting even heavier very quickly. He said he has access to a shop so I assume he would be MIGging this and not trying to stick weld it.

    I am photoshopping pictures of the stretch right now. Just finished the full height handle bars and it will be quite a change. Real 80's style V shaped ape-hangers. If I can get the 9 inch stretch on the frame it will be a real sky-high front end transition to a stretch low-ride frame. Hopefully this tubing is straightforward like I was hoping, or I will be starting over on materials.

  2. professor

    professor Active Member

    Maybe you can find some tubing that will fit inside the stuff you have so you can have sleeves like Danny wants.
    I have no problem streching a frame like you describe, I gas welded the extensions to the rear of a 20 inch bike, however I don't weigh 200+ lbs.
    Stretching the frame puts more load on the tubing regardless of welds. On my motorbike, I added another horizontal bar (the engine sits on it) - making the 3' stretch stronger. On that bike I stick welded the frame using tiny rods from HF and 60 amps.
    I don't have a mig at home.
  3. GearNut

    GearNut Active Member

    I don't recommend butt welding the tubing. You should "plug" it as professor suggests. The joint will be much stronger that way.
  4. sfhellwig

    sfhellwig New Member

    Just so I understand the process, because I am learning metal work and want to learn the welding: If we are doing an internal sleeve is it simply the physical structure or is it the fact that there is more metal for the weld to penetrate into. I agree this construction would be superior but now I have to find more material (and gain more weight). Luckily I have a frame or two to chop on, maybe the seat stays will work with the handlebars. I think the bars will get done as an experiment to make sure we like the process but may end up too heavy for final use. At least I can go buy a set of apehangers to fix that. I only want to cut on this frame once so more searching to do. Larger diameter tubing is harder to come by.
  5. GearNut

    GearNut Active Member

    The extra material (physical structure) strengthens the joint. Plain jane butt welded tubing has a nasty habit of cracking directly adjacent to the weld. The internal plug does a great job of preventing this. If you use hollow tubing for the plug then you should not get much weight gain at all. Do bear in mind that the tubing used as a plug needs to be a tight slip fit inside the frame tubing. If it just falls in it will not give the support necessary. Sanding down a slightly larger tube as a plug is your best bet. Even EMT conduit will work as a plug and can be found for free as trash at construction sites. If using EMT be very careful to remove ALL of the galvanized plating as it gives off extremely toxic gasses when welded.
    Also, EMT makes for a very poor frame tubing, so only use it as plug material.
    Oh yeah, the plug should extend about 1 inch minimum past the weld in both directions.
  6. Dave C

    Dave C Member

    And to really do it right drill 4 holes about 3/8"ths. in diameter in each end of the tubing spaced out around the area the plug will be under. Weld through these holes to the inside plug. These welded spots vastly increase the chances this weld will hold. I do it whenever I have to do a race car frame repair. You cut out the bad stuff and use spuds inside for strength when welding in the new replacement parts. Our inspectors won't let the car race without them, they need to see the evidence that it was done but you can grind them off flush without lowering their ability to stop the joint from separating if the weld fails.
    Jeffrey gagnon likes this.
  7. GearNut

    GearNut Active Member

    Too true, Dave C!
  8. sfhellwig

    sfhellwig New Member

    Somehow I managed to miss the last posts about the drill through and tack to the internal sleeve. Sounds like a great idea and I will remember it in the future but the frame is DONE and came out plenty strong. Good info though.

    And so I will post a preliminary pic. The first thing I will say is that Danny is a weldor, and not a bike designer. It came out differently than my original design and at first I thought it would be possibly very bad on the geometry. But I decided to get a chain on it and ride it around the block. To which I was pleasantly surprised to find the bike rather comfortable. And just as strong as the original frame I feel. By keeping the top tube straight it clocked both halves of the bike forward, advancing the head tube angle and the seat tube. Not a major deal on the seat tube except it put the chain clearances in the fender out of position so it had to be pulled for now. I like seeing more of the rear tire. I think if/when the fender goes back on it will be bobbed.

    But I am shocked. This thing is LONG. With the advance of the front end and the top stretch being 10.5" inches (bottom measures 9" like specified) I am at my exact reach to hold on. It's a real ab cruncher to have the seat down. But the front end is sharp. I have estimated right now that it is no further than but probably similar to the 70º of a BMX racing geometry. It makes the bike turn sharp but not too sharp and has actually taken out the low speed "chopper wobble" even though the original angle was no worse than 65º. It is a real bus-driver but I like it more than the original. My thoughts of "this will have to be redone in the future" have changed to "this is going to work, time to proceed to the next piece."

    When I picked up the bike we chatted about everything but the frame so I can't even tell you what the material is. It appears to be galvanized pipe. I can tell you he did not use any of the supplied frames, he had this metal and had the ends milled down to fit into the frame tubing. I'm not sure how far they were sleeved but he knew 1" was the goal. The welds are beautiful, as nice as the stock welds. The frame is solid, when you kick the bottom tube the bike rings slightly, like the stock frame did. All solid, no dead spots. It flexes slightly, but I did just limo out a stock frame.

    I need to get some taller bars. Should bring my grips a little closer back. Not sure if the motoring will happen this summer or if it will be a winter project. But the frame is done, and I think looks quite good. I have plenty of room to choose where the motor will go and plenty of solid tubing to design around for the mounting. Just wanted to update you guys on what happened and how it worked. Hopefully it will help anyone else looking to create a one off frame for their motored bike.

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    Last edited by a moderator: Dec 18, 2015