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  1. #1
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    Default Bondo bikes??? Molding questions

    Ok, so I know a lot of people call them 'bondo bikes" but this has to take the cake. Here is some close-ups of the molding done on my new frame.





    Call me dumb if you want, but I busted out my sandblaster the other day just too see the condition of the frame under the paint. If I'm going to strap my life to this thing at 80mph on the highway, I want to make sure the welds are good, and it ain't gonna snap under my fat ass. What the guy did was chop the front triangle off right above the front motor mounts, and at the kink in the backbone. He then extended the front legs (don't think he stretched the back bone at all), and welded it up for the rake (old cast Ironhead neck is intact under there). So here in lies my question. Did they really used to just pile on 20lbs of bondo on these things!!! Everything I have found online says yes! Am I stupid for taking this all the way back down to the frame, then gusseting it to get my rough shape, and filling in with body filler from there? This makes a hell of a lot more sense to me. I mean if you are going to add that much mass, why wouldn't you expect to get a little more structural integrity out of it? I'm not talking 1/8" plate, or anything ridiculous, maybe just 14-16awg sheet metal. But this makes a hell of a lot more sense to me, especially for longevity of the molding job. Has anyone here done what I'm thinking? Kinda like capping the inside of the gussets on the neck of a Santee frame to box it in, then shaping the bondo over it from there to smooth out my shape. What do you guys think. I can post a pic tomorrow of much bondo is in there, most of you probably have never seen this much filler in one place before. Thanks in advance guys.

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    when i used to build show cars for a living we'd always get the metal as close as humanly possible, then take out the grind marks and hammer tracks with filler. in my opinion anything over 1/4" thick is too much to expext to stay nice for any reasonable amount of time.

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    I don't see what the problem is with the molding job. Looks like whoever did it did it right.

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    MHM, think about it for a minute... You're asking if a job like this can last. How old is that frame? When was this done? Looks pretty good to me.

    Back then, they didn't know what ''structural integrity'' meant. These bike were thrown together in the backyard and the best was hoped for. Like a lot of stuff from back then, it worked, well.

    Blast it down to metal. You'll feel better. I would. However, do NOT underestimate the amount of time that is necessary to get a frame to look like that. Even if you box the neck and so forth. That shit takes forever. Putty, sand, repeat ad nauseum.

    That bike is f'n sweet. I can't wait to see your progress on it.

    C

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    I just don't think 25lbs of bondo is right under any circumstance, maybe my personal opinion. I agree with Nate, I used to build lowriders and mini-trucks and that much bondo is asking for cracks. That entire neck, and where the tube looks square is all bondo.

    Topher, my man! The guy I got it from got it in 99 from a guy who owed him money. All he knew was it done by some guy in Reno???? So who knows when it was done. But if you look at the backbone pic under the tank plate, it has several cracks in it. And the thing hasn't been on the road for over 10 years. So I'm with ya on taking it down for piece of mind. I also plan to drill a small hole where it's butted to the down tubes to see if he slugged it. I know it's gonna be a pain to remold, but hey, isn't that what it's all about? Makin it yours? I've done a ton work with glass and bondo from years in the high end car audio game. I know a few tricks (mainly custom rasps I have made for shaping, pretty neat trick huh?). I am hoping to get it done on my week off at the end of the month, I should get all the big chunks out tomorrow. I will post a pic of it as I left it before this work trip tomorrow. It's almost like one of those cut-away plastic human organs at the doctors office. Ha ha. You gotta see this shit. It really is deceiving in the pics. That arc at the back of the neck is probably 10-12lbs of bondo in and of it's self, and I am not exaggerating. I'm glad I'm at least not the only one who would tear into it to make sure it's safe.

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    Default Dynaglass

    You might try to do the majority of the molding with dynaglass. Its much stronger and less likely to crack because it has more flex than bondo. We use it to mold frames first and only bondo when absolutely necessary. You probably already know that though if you've worked with it before.

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    Quote Originally Posted by Local138 View Post
    You might try to do the majority of the molding with dynaglass. Its much stronger and less likely to crack because it has more flex than bondo. We use it to mold frames first and only bondo when absolutely necessary. You probably already know that though if you've worked with it before.
    Yup! But good call. I am still going to use sheetmetal first, then kitty hair. I used to use that a lot in enclosures then a thin skin of a polyester filler. It is a little easier to get the final layer nice and flat for painting. Maybe i'll skip the last layer just to not risk separation of the materials, and do the extra sanding.

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    Quote Originally Posted by MileHighMurdercycle View Post
    I just don't think 25lbs of bondo is right under any circumstance, maybe my personal opinion. I agree with Nate, I used to build lowriders and mini-trucks and that much bondo is asking for cracks. That entire neck, and where the tube looks square is all bondo.

    Topher, my man! The guy I got it from got it in 99 from a guy who owed him money. All he knew was it done by some guy in Reno???? So who knows when it was done. But if you look at the backbone pic under the tank plate, it has several cracks in it. And the thing hasn't been on the road for over 10 years. So I'm with ya on taking it down for piece of mind. I also plan to drill a small hole where it's butted to the down tubes to see if he slugged it. I know it's gonna be a pain to remold, but hey, isn't that what it's all about? Makin it yours? I've done a ton work with glass and bondo from years in the high end car audio game. I know a few tricks (mainly custom rasps I have made for shaping, pretty neat trick huh?). I am hoping to get it done on my week off at the end of the month, I should get all the big chunks out tomorrow. I will post a pic of it as I left it before this work trip tomorrow. It's almost like one of those cut-away plastic human organs at the doctors office. Ha ha. You gotta see this shit. It really is deceiving in the pics. That arc at the back of the neck is probably 10-12lbs of bondo in and of it's self, and I am not exaggerating. I'm glad I'm at least not the only one who would tear into it to make sure it's safe.
    Fair enough and good info.

    Any pics of those rasps you mentioned. I try and avoid bodywork at all costs, however I'm always open to new stuff (to me) that might help me enjoy it a little bit better.

    C

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    This ones about 40 years old and has held up very well,,the cracking it has gives more an antique look than anything else
    Attached Thumbnails Attached Thumbnails cal1.jpg   cal2.jpg   cal3.jpg   redone  tank.jpg  
    Last edited by HumblePie68; 01-17-2011 at 6:58 AM.

  10. #10
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    i don't like molding never have. when you have to take a tank off there you are,then there's cracking,and if I see cracking I'm not happy till I see the reason why! give me exposed welds,even if they are rough I know what I got!

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