First time newbie, so hope this post works. The frame was free and my son and friend worked on it over the winter and I was elected the electrical wiring guy. Finished electrical last week. First ride steering is horrendous. It can be ridden with finesse, but there is definitely room for improvement. Then I noticed the fork is bent. I don't know if its an incomplete springer/rocker mod, or if fork is from a different version of minibike, or if its original equipment and just bent. Anyway I need experienced input to decide how to fix it.
Blisters, forks, and recovery
- Thread starter rdragons
- Start date
I would cold bend it; heating would anneal (reduce hardness) the steel. If it's only been bent once or twice, straightening it shouldn't be a problem, just be careful not to overshoot and bend it back and forth repeatedly as each cold bend will harden/fatigue the steel a little more. The good thing about FOMOGO's method is that it works both tubes together, keeping them even, but you could do them individually by sliding a larger tube over the fork tube to concentrate the bending force where you need it (if you just pull on the fork tube, it will tend to bend in another area rather than straightening the existing bend). If you can weld, or have a welder nearby, there are a few ways to reinforce the fork. You could cut the flattened ends off and slide a smaller tube inside or a larger tube outside, then weld the end back on (and weld the ends of outer tube if that's the way you go). Another option would be to add a "bridge" to the front or rear of the fork tubes (rear would look better, IMO, but may restrict steering). As for seeing cracks before something breaks, the black paint would make that difficult, but you could remove the paint and inspect the bent areas, just avoid removing metal with the paint (use paint remover or hand-sand) as you don't want to thin/weaken the tubes. Of course, if the fork is super-strong/rigid and someone runs the DB into a tree or other solid object, the frame would probably bend instead of the fork, but that may be the least of your problems in that situation (Helmet!). I tend to overthink things, so I'll add that just straightening the tubes and inspecting afterward would probably do.
Here's one idea for a bridge design, the triangulation should add a lot of strength.
Here's one idea for a bridge design, the triangulation should add a lot of strength.
Bending them back will not create a problem. You have to bend a piece of metal multiple times before it becomes work hardened and then brittle and then fractures.
They will tend to bend a little easier the next time they are run into a solid object. The metal is stretched when bent and compressed when unbent. The stretched portion will be slightly weaker than if it had never been stretched. They will not be weak by any means but they are not as strong as they were before they were bent the first time.
They will tend to bend a little easier the next time they are run into a solid object. The metal is stretched when bent and compressed when unbent. The stretched portion will be slightly weaker than if it had never been stretched. They will not be weak by any means but they are not as strong as they were before they were bent the first time.
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Charles S.....................You have a beautiful mind. Thank You again!
massacre......................When I first looked at I thought they had put the fork on backwards, and they pointed out they didn't want the handlebars in their lap. It is bent at 22 degrees just like FOMOGOS picture.
FOMOGO.......................I agree.
chipper........................"shop press easy". Unless you don't have a shop press! I already nixed the jack between front of motor mount and bottom of forks (Nissan has weird jack and I don't want it slipping off into a new engine. Option 1: Wrap a chain around the fork and the bed post and throw it out the second floor window. Option 2: F150, nylon rope, and the tree, but I don't think the tree is big enough to survive. Option 3: Clamp forks between 2x4s and 2x2's, but I haven't figured out how to hold the frame vertically. 3.5+1+1.5=6 and my C clamp are only 5". Oh well, back to the drawing board.
It appears the consensus is cold bend.
I was hoping for a quick fix without taking it apart so I could ride it for a few days, but it's getting complicated and it is their bike so will probably delegate it back to them to fix.
Thanks to everyone for the input. Will try to post some pictures of whatever happens.
massacre......................When I first looked at I thought they had put the fork on backwards, and they pointed out they didn't want the handlebars in their lap. It is bent at 22 degrees just like FOMOGOS picture.
FOMOGO.......................I agree.
chipper........................"shop press easy". Unless you don't have a shop press! I already nixed the jack between front of motor mount and bottom of forks (Nissan has weird jack and I don't want it slipping off into a new engine. Option 1: Wrap a chain around the fork and the bed post and throw it out the second floor window. Option 2: F150, nylon rope, and the tree, but I don't think the tree is big enough to survive. Option 3: Clamp forks between 2x4s and 2x2's, but I haven't figured out how to hold the frame vertically. 3.5+1+1.5=6 and my C clamp are only 5". Oh well, back to the drawing board.
It appears the consensus is cold bend.
I was hoping for a quick fix without taking it apart so I could ride it for a few days, but it's getting complicated and it is their bike so will probably delegate it back to them to fix.
Thanks to everyone for the input. Will try to post some pictures of whatever happens.
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FOMOGO..................Thank You.
massacre..............I do have a trailer wench rated at 900lbs.
manchester1...............Son said he had bending machines at work, but thought to complex because he would have to setup separate machines for both left and right bend.
Son decided to pull fork last night. First pass 4x4s, 2x12s and bar clamps (four clamps made cranking easier). Then we fine tuned it with some shims and C clamps (no picture). Final tweek with truck receiver hitch (his truck the trailer electrical plugin interfered so moved to my truck) in both cases end of fork was against spare tire. Fresh coat of black paint and reassembly tonight.
There is a quarter inch gap between the fork cross braces and the column upper and lower bearings. He selected two washers to fill the space and I told him to fill the gap on the bottom????
massacre..............I do have a trailer wench rated at 900lbs.
manchester1...............Son said he had bending machines at work, but thought to complex because he would have to setup separate machines for both left and right bend.
Son decided to pull fork last night. First pass 4x4s, 2x12s and bar clamps (four clamps made cranking easier). Then we fine tuned it with some shims and C clamps (no picture). Final tweek with truck receiver hitch (his truck the trailer electrical plugin interfered so moved to my truck) in both cases end of fork was against spare tire. Fresh coat of black paint and reassembly tonight.
There is a quarter inch gap between the fork cross braces and the column upper and lower bearings. He selected two washers to fill the space and I told him to fill the gap on the bottom????
