The Chopper Compendium

I have most of an old Evo Sportster that has been sitting in my shop for years (frame,engine rear wheel and odds and ends). I have decided to finally attempt to build a long bike (something I have been wanting to do for quite a while).
I first learned to weld while in High School (in the late 1970's), however I never learned to weld in a manner to control distortion and shrinkage. (all the projects I have welded were not terribly precise in that way, or I just got lucky and they turned out "straight enough" think a couple different winch mounts, brush guard, winch bumper, trailer hitches, other small stuff and minor repairs).

Now to the prob at hand. My first attempt at building the top wishbones failed miserably. The "legs" of the wishbone sucked in 5/8" with the fender crossmember also welded in, when I realized this I started cutting it all apart, for 2 reasons.
1. to see how bad the distortion actually was (cut out cross member and the legs sucked in another 1/4")
2. to check penetration of the welds (no problems there, plenty of penetration)

It is my belief that I welded the WB legs to the backbone improperly (obviously, one of the mistakes I made). I welded that joint as I did the cross member "fish mouths" basically start at the ends and weld to the middle of the joint alternating corners in an attempt to minimize distortion (that didn't turn out so well).
Now since I fucked that up in the first attempt, I am going to do what I probably should have done to begin with and cut some similar "practice joints" and practice those welds. I'm hoping someone here can give me some advise and maybe a few tips on procedures to control distortion. (and hopefully waste a little less material).
Any and all help is appreciated.
Thanks.
Mark
Will post some pics when I have some actual progress.

Forgot to mention that I am only using the front part of the engine cradle and the steering neck from the original frame.
Front part of cradle being the front motor mounts and about 13 1/2 " of the bottom rails and 20" of the original down tubes.
I'm using a modified version of the BC 1 Sportster plans that are in the CBH downloads.
Some of the mods are skipping the out bends for the wide tire,
running the back bone all the way to the fender cross member,
and using 1.25- 1.88 round tube for the rear motor mount and running that up to the back bone to stiffen the structure of the frame. (That's my thinking anyway)
I need to figure out how to post pics from my flickr account and I'll post up the drawings with the mods and any progress I make.
Any advice is greatly appreciated.

have you read garys original writeup on frame welding in the handbook i read and reread the whole cd several times a ton of great tips

I got the 3 Handbook "cd's" as a download but haven't seen a section on just welding. I've read the Old School Frame Build article more times than I can count, but there isn't really any info about welding procedure. Do you mean the section 5) General Fabrication chapter? There is a couple pages in that chapter that discusses welding sequence but that is what I followed (the little welding joint diagram) when welding the wishbone that turned out so miserably.
Could you possibly walk me thru how you weld the wishbone pieces to the backbone? Maybe with any luck that will give me an Idea of where I went so wrong.
It really chapped my ass after spending so much time fitting the pieces together to have the welding turn out so terribly distorted.

If we knew what type of welding, i.e. stick MIG, no gas MIG tig, oxy acetylene you do the suggestions might be mor specific. Pics couldn't hurt.
Dusty

Sorry, I'm using tig. I'll admit that l am not the best tig welder, but I am improving with every bead.
Nothing to take pics of at the moment. (I cut it all up since it turned out so bad, and I wanted to "check my work", as far as penetration and all).
I'm going practice some more since I have some spare tube now. I'll post some pics when I have something worth looking at.

Found a YouTube channel by a guy named Phil Dolan from New Zealand that has a bunch of build videos. I watched a couple and figured out I was getting way ahead myself and I think that is about 85-90 percent of the problem.
Started on a new set of wishbones today.

i generally try to tack top center bottom center front then back . then ill weld from top center to front bottom center to back top to back bottom to front . i use a couple fireball squares as spacers between the wishbones to try and keep the space even but before that i just cut a couple tubes and fish mouthed them to the right size i have never seen them come out absolutely perfect the nice thing about tig is you can spot heat a spot and let it shrink to where you want it to be within reason

I did pretty much the same thing 'cept bass ackwards. Started top front to middle etc. etc.
Did not know about the spot heating thing, good to know.
Thinking about it though it makes sense, controlled shrinkage right where you want it (if you know how to do it right).
Oh boy more shit to practice at.
Keeps me out of the house and beats the shit out of sitting on my ass watching the idiot box.

Went back thru the CBH download info and I think I found the welding info Curt talked about earlier. There is a couple pages in the "General Fabrication" section, then in the "Tools, Eqipment and Supplies" section there was quite a bit more. I have also been reading some of the tech info on welder manufactureres websites, like Miller, Hobart and Lincoln. Also been checking out "welding tips and tricks" and the "Fabrication Series" along with more of Phil Dolan's channel on Youtube.
Now more practice, practice, practice.
Spent a couple hours in the shop fitting WB legs to the Back Bone ..... again. Almost ready to tack together.

measure as many factory frames as you can you will instantly feel better about your ability

curt wrote: ↑Thu Aug 07, 2025 10:36 pm measure as many factory frames as you can you will instantly feel better about your ability

Lol Thanks Curt, the only other Sportster frame I have is still a complete running bike and I'm not messing with that one for now.
I think I finally figured out how to use the old Flickr account
(I haven't used it for about 10 years or so) so I should be able to post some pics when I have something to show.
Bent tubes for the down tube extensions, have a little more fitting to do on the wishbones and then I'm going to have to get my son to do some math for me to figure out the bends for the lower rails.
He does the complicated math around here, he's a teacher now but when he was in High School the little turd could do calculus in his head as easily as I do basic addition and subtraction. I asked him if he could help me, his smart ass reply was , it's only trig what's the problem?
I almost told him. I'm a dumbass ... Here's your sine.

DSCN0101 by mark perkins, on Flickr

New wishbone I'm working on

[imgDSCN0100 by mark perkins, on Flickr][/img]


same stuff other end

[imgDSCN0099 by mark perkins, on Flickr][/img]

Modifications to the BC Sportster Frame drawing


[imgDSCN0097 by mark perkins, on Flickr][/img]


This is the jig I built, some chipboard axle plates for mock up and what I have done so far on the down tubes.
The lower rails are gonna be fun to figure out. I will be modifying the modified drawing again as I don't think I can come close to doing
those bends in the lower rail. I will have to adjust the angle and the position of the first bend to make it work.
(good thing my son is good at math because it's definitely not my strong suit)

the worst part is bending and fitting one side then having to mirror the other side but after you have done one everyone after that gets easier