The Chopper Compendium

Greetings folks. I'm new to the forums but, I'm hoping this place will be a good resource for a project I'm working on. I'm also new to chopper building but I'd like to think I'm mechanically inclined enough to handle a small personal build. (With all of your help of course. )

Here's a quick run down of where I started. I scored a couple Honda XR Dirt Bikes on the cheap so I thought "why not?" I'll chop one up. So currently I'm looking to figure out a way to use the existing axle plates & brake stop mechanism on the swing arm and tie them into a hard tail. If you are familiar with these bikes they don't have a single backbone down tube. The backbone stops just behind the gas tank and splits into two down tubes that mate with the bottom of the frame (essentially the front portion of the frame is like a cage around the engine). A quick google search for a Honda XR200,250, or 350 and you will see what I'm working with.

All of that being said most pre-fab hard tails and even custom built stuff I've seen use solid flat steel axle plates 99.9% of the time. (aside from some of the "boxed in" plates). The swing arm on the XR's is a little different, where as the axle plates are flat steel with a box steel plug that's just jammed into the square stock steel swing arm and welded together. Or at least that's what it looks like to me. So before I get to the real crazy question; My first question is would there be any potential problems by just welding the frame tubes on the top and bottom of the square steel swing arm and then cutting the swing arm away and putting in some gussets? I know that with the flat axle plates the tubes are generally "slotted" and pushed over the plate. What's the extra mile I could walk to ensure this is a safe connection? Below is a quick diagram I whipped up that will hopefully make sense.
(Diagram is not accurate dimensions just for visual aid)


REAL Crazy question:
Could I just extend the square swing arm steel back into the frame where it originally pivoted, run an additional bottom tube, ladder bar brace between the square tube and the new bottom tube, and then extend the backbone down to a cross member? Could I do that and eliminate the seat stay down tubes? If it would be a death trap waiting to happen from an engineering stand point I'll pass....but only having lower tubes in the rear would totally look bitching.... diagram below. Thanks in advance for any advise and input!

i don't really think the second option would offer enough resistance to flexing (i.e. not much triangulation from the looks of it).

using your first idea, how about just making one plate to comprise the axle plate, gussets you have drawn in, and welding in an appropriately sized bung for the brake stay?

sounds like it's gonna be a fun project (already is) and a light chop built around one of those engines should be a whole lotta fun. can't wait to see it come to life.

welcome to the CC!

-dan

budoka wrote:i don't really think the second option would offer enough resistance to flexing (i.e. not much triangulation from the looks of it).

using your first idea, how about just making one plate to comprise the axle plate, gussets you have drawn in, and welding in an appropriately sized bung for the brake stay?

sounds like it's gonna be a fun project (already is) and a light chop built around one of those engines should be a whole lotta fun. can't wait to see it come to life.

welcome to the CC!

-dan

Hey thanks for the response and input! Primarily the reason I wanted to stay with the existing axle plates is because I don't really have a jig or the experience with building a proper jig. If I can weld everything in place with the wheel on the existing swing axle I figured the axle plates would stay lined up at least by the standards of the Honda factory. I'm trying to make up for my lack of knowledge (and tools) with a little clever ingenuity. I even went as far to fashion some brackets out of angle that would bolt to the original pivot point on the frame and allow me to bolt the swing axle to the bracket. It stretches the wheel base x inches (currently 3 but I may make it 5) but keeps everything lined up center.... Or at least that's what I' hoping it does.

That being said I've thought about it. I was going to order a weld in universal hard tail kit to fabricate this from that comes with axle plates anyway. It's not off the table. I just don't want to have a whacky wobble because I screwed up the alignment with a careless error someone more experienced wouldn't have made.

I'll try and post some pictures of where I'm at so far but...It's really early stages of just being cut apart.

I really really would like to do the second option. I think it would look bad ass. However for a first time builder I may take the tried and true route. I will say mocking stuff up with PVC and junk around the shop it does have more "triangulation" than that quick diagram... sort of. But I don't wanna risk falling all to pieces on the highway either.