motorized pit bike chopper build

[4agshoob]

sup guys?

Ive been on the forum for a little over a year, just kinda lurkin', checkin out some of the incredible talent and knowledge in these posts. ive built several "bolt together" "manual" bikes, parts from this, parts from that, and pedal off. however ive been waiting to find a certain style frame to really dig in and "build" a motorized unit.

well, earlier this week, I finally got the come up on that particular frame: an OCC Schwinn stingray, adult size. rideable, but not the prettiest, missing a few things, like fenders, surface rust on the chrome, no front brakes, etc, but was a cool $20. a perfect price for cannibalization.

first thing I noticed upon riding the bike:

-my knees and elbows were having confrontations.....
-wheel flop from offset triple trees was horrible, almost like a severe negative trail....
-bike had been sitting in the rain, as my .... was now wet.....
-at 6'3" this bike was all wrong for me.....


feel free to follow me, as I build/modify my first custom frame/cannibalized bike. my first time motorizing a bike, and my first time diving head first in custom suspension geometry... on a bike. (deep root mini-trucker, ive played with plenty-o-suspension, lol) while im pretty experienced in small engines, welding, engineering, and general niggonometry; this is my first for a bike. feel free to constructive criticize, bust my balls, tell me when im wrong, and show me where im effing up, im a grown up, no cry babies here.

 

[4agshoob]

so, with the forks teedering on being ordered in reluctance to the whole rake angle dilemma of the OEM headtube, I focused on moving the rear wheel back. again I turned to google to see how other managed to move their rear wheel back, without frame modification. I found something on peddalchopper.com that bolted to the factory OCC drop outs.... and it got some gears turning in my head.

back story: I have about 10 20" bikes at my disposal ranging from freestyle, to girls cruisers, to full suspension mountain style bikes with derailers, etc. I also have about 3 26" and 1 24" full suspension mountain bikes. I collect them from garbage piles, thrift stores, etc for the right prices.

moving forward....

99% of todays mountain bikes have these:

well, as long as the 2 closest holes measure at least 3" or more, you can actually bolt them onto the OCC drop outs, to lengthen your wheelbase, and bonus, depending on how you flip them, determines the height in which your wheel will sit. a few 1" x1/4" hex bolts and some washers later:

But, upon doing this, i noticed it hosted a few more hurtles:

-brakes arent gonna work.
-i now have to install a chain tensioner, because the new brackets arent slotted for adjustment.

Which all really sucked, because i kinda liked the new seating position. I dig the whole low frame, sitting in front of the back tire stance.

What to do?

 

[4agshoob]

Meh....

Scrap that idea.

But dang it, i need that extra leg room.

Out comes the saw zall....

But first, i have this cool swing arm pivot/hinge thingy, and a magnet sticks to all the metal....

COOL!!

Chop, chop!!

 

[4agshoob]

Thats it....

After the thought of staying rigid frame, and looking at pictures of other "stretched" OCC rigid frames, and the thought of my 250 lbs rear end being on that rigid frame...

That swing arm style pivot started looking incredibly inviting. Screw it, here goes nothin'....

I seperated the rear forks from the frame, lined up my hinge, scourde the paint and welded it to the rear fork section. Then welded the other side to a piece of the original bottom frame rail.

Already have the rear of the bike cut up, heck, lets just correct this head tube/rake angle while were at it, so i can run these chrome springer forks im tasting.

So i cut the front frame rail, about 4" above the pedal gusset. First i found my angle in which i wanted, and then cut and bent 2 pieces of 1/2" sch 40 that will now be my bottom frame rails. I put the front frame well in a vice, and squeezed the tube into an oblong, ovalized shape that fit tight on the new 1/2" lower frame rails. Lined em up, welded em in temporarily. Those 2 rails will run parallel on both sides of that original lover frame piece i attatched the hinge, and rear fork too. Then i can add some gussets to "clamp" it all together when i do the final welding.

Heres a visual mock up:

Keep in mind:

- that teal top bar is just there for some angular reference.

- the rear swing arm will be sprung, and is sitting well below its final angle.

-the 2 lower frame rails are temporarily slid inside the oval tube attached to the rear hinge.

-the new forks wont wave any offset.

-the frame will be about 6-8" shorter than mocked up here.

The bottom of the frame will have about 3" of ground clearance once the rear is suspended, and the new forks are installed.

Hopefully more progress tomorrow.

 

[GuitarlCarl]

They ain't the best frames for big guys. But my first build here was a "softail" OCC. Headbanger still has a place in my heart even though I recently stole the forks for another build. I'm thinking of replacing the missing forks with stretched full suspension.
I like what you've done so far.

Guitarl.

sent from a banana phone...

 

[4agshoob]

Progress today.... we have a roller!!

Here it sits about 2" higher than its final height. As soon as the forks come (about 2.5" shorter than OEM) i can begin mocking/building the rear suspension assembly. For it to sit level.

 

[4agshoob]

The springer saddle will sit a bit further back than the scrap seat on the picture. (I had to sit on it, for feel )

Heres the forks im going with:

Still searching for a decent looking tank. I had the thought of modifiying a heiniken mini keg, but i want this thing kinda clean when im finished.

Anyone know where to find a chrome 20 x 4" rear wheel?

Ill be using a lowrider style 72 spoke 24" up front, id like to have some bling in the back to match as well.

 

[Fv2]

I'm pretty sure that stock rear wheel is aluminum, it'd be much cheaper to polish it up.

 

[4agshoob]

I'm pretty sure that stock rear wheel is aluminum, it'd be much cheaper to polish it up.

Ya know i thought on that last night after i posted this, and searched for one. I beleive your right.

 

[4agshoob]

They ain't the best frames for big guys. But my first build here was a "softail" OCC. Headbanger still has a place in my heart even though I recently stole the forks for another build. I'm thinking of replacing the missing forks with stretched full suspension.
I like what you've done so far.

Got a link to that? Im interested in checking it out.

 

[MotoMagz]

Hey it's lookin great. Nice to see someone adding suspension along with the stretch. I was at Portland this past year guy had a nice looking stretched out Cruiser. But let me tell ya that thing was flexin so much,that it will snap one day.Nice work!

 

[Fv2]

Hey it's lookin great. Nice to see someone adding suspension along with the stretch. I was at Portland this past year guy had a nice looking stretched out Cruiser. But let me tell ya that thing was flexin so much,that it will snap one day.Nice work!

I think we saw the same bike.

 

[GuitarlCarl]

Got a link to that? Im interested in checking it out.

Yep. It was my first build HERE.
it's been slightly redesigned since...

Da Bears

Carl.

 

[4agshoob]

Yep. It was my first build HERE.
it's been slightly redesigned since...
View attachment 44568
Da Bears

Carl.

Looks comfy. For some reason im wanting this thing as low as possible.

As for mine having pedals, its up in the air at the moment. I gotta check with local laws. I know in GA, anything under 50cc doesnt require a tag, ins, or liscense, as i rode my debagged venom motorsports x19 110cc as a "50cc" and never had an issue.

But after watching youtube today at a few of "sinister bikes" videos, alot of his stuff made sense.... of why to keep pedals.

I want to run a 48t or 50t rear sproket on a 20" wheel to keep from having to pedal assist it up any hills, as mentioned im a pretty hefty fella. I dont really care about top end speed, i just wanna cruise, 18-20mph. Maybe my next build will be a bit more about speed.

 

[GuitarlCarl]

Illinois and many states, require the bike to be pedal assist, and under 80/50cc (I've read there's two ways to figure it) pedals also allow for a coaster brake which would be a nice e-brake.

Guitarl.

 

[4agshoob]

Illinois and many states, require the bike to be pedal assist, and under 80/50cc (I've read there's two ways to figure it) pedals also allow for a coaster brake which would be a nice e-brake.

Guitarl.

There again with the coaster brake, im using the stingray rear wheel. I dont plan on riding this on public roads. Ill probably save that for the next build. This will be a car show cruiser/track bit bike/camping/etc.

 

[GuitarlCarl]

There again with the coaster brake, im using the stingray rear wheel. I dont plan on riding this on public roads. Ill probably save that for the next build. This will be a car show cruiser/track bit bike/camping/etc.

Yeah duh
I wrote that coaster bit without thinking about your parts, just motored bikes in general. Sorry.

Carl.

 

[4agshoob]

ok, well, after part searching a bit more this evening, I found myself again on pedalchopper.com. there, I found possibly another option. withen those options I also found some upsides... way more than any drawbacks, other than monetary.

jim sells the 3 speed kit for the OCC bikes. but, he sells it in a kit. this kit is $700 and includes everything you would need to retain functional pedals. that kit also includes a custom built 20x4.5" wheel, with a sturmy archer 3 speed hub, and disc brake adapter, caliper, new cranks (off set) shifter, jack shaft, and brake cable adapter to also use the v brakes.

I messaged jim, asking about pricing on just the rear sturmey archer wheel with brake disc, and jack shaft. I wont need anything pertaining to the pedals, as well as a shifter, or the v brake dual cable setup.

im currently awaiting his reply.

I kinda like that idea better. getting rid of the v brakes on the rear forks clears up a lot of room for the chain, and tensioner. no huge fixed speed sprocket to bolt onto the hub. I also like that idea as having an under drive gear, a 1/1 gear, and an overdrive gear. my real question is: ive never experienced a sturmy archer hub... how under driven is it in low gear? do they make higher tooth count cogs, say can you change out a 14t for a 18t?


like I said this is my first. I have a vision, and a desire to keep this thing pretty clean, and well functioning. ive even found a 5 speed sturmy archer hub, and im almost tempted to see if jim would be willing to let me ship it to him to build my wheel out of it. just keeping of closer ratios, and possibly and even higher low gear for pulling.

 

[4agshoob]

Tonight, $35 later... i managed to get all the hardware for the rear shock assembly. Why so much?

All stainless.

Acorn nuts, finish washers, all of it is stainless. For the strength, and asthetics. Nice and shiny, no rust, etc. 5/16"

I also got a 3' stick of aluminum 7/16" O.D. 5/16" I.D. to cut for my bushings on either side of the shock. I did get nylon washers for the swing arm side of the shock, as it will be the pivoting point.

I also decided, ill be bolting the shock mount on. A few reasons. The shock mount plates are 3/16" steel. The parts where they mount is the roundest part of the oval on the bottom tube, and the seat tube. Welding this, and making it look good (mounting a flat plate onto a rounded surface) are 2 different sciences. So bolting it is. Also, when it comes time to paint the frame, there is alot going on in that area, the paint would get kinda heavy trying to cover all the angles.

Lastly, i might actually polish these, and clear them to make em appear like chrome. Ill know when it comes time to assemble.

The spring will be painted to match whatever color we decide to paint the frame. The shock body and hardware will remain polished.

Colors are in disscusion between me and the wife. There will be chrome wheels, chrome forks, any thing that can be polished, will be. White walls and a white saddle is a must. The 2 colors where discussing at the moment are:

Tiffany blue gloss
Deep purple metallic

 

[4agshoob]

Got the suspension all bolted in today, and my fear was confirmed....

The way i had designed the shock mount was too "efficient". At 250lbs, i bottomed out an 850lbs shock, and set the frame on the ground .

Faaaack.

That design, looked like this:

The intended angle was more maximum absorbsion (comfort) but it was a little too much.

Then i played around with the idea of dual linear shocks. I had wanted dual shocks to begin with, but i felt like they would get complicated with the jack shaft and chain drive. I played with this idea for about 30 minutes before realizing i didnt have the proper geometry angles to run this setup. The rear shock was still taking the blunt of the load. Would have been cool though.....

So i piledged up a shock mount from another mountain bike, and welded it at a different angle on the swing arm. This became a very progressive angle. The closer the bike came to the ground, as the swing arm moved forward, the more linear pressure it put on the shock. However, im still too heavy.

So i sat and marinated on a smoke and looked over the bike.... then it hit me. With this setup, a can run dual shocks, one on both sides, have clearance for my jack shaft and chain drive, and enough support for my weight with both shocks.

(the spare tail of metal behind the seat post tube will be gone when finalized)

Now, my next hurdle. Every, single, friggen, 6.5" (165mm) or 7"(178mm) [eyelet to eyelet] shock i find is some $50 fox fancy rig.... and i need 2 of em.

I know this 6.75" one i have came off a genesis 26" mtb, and is a cheap chinese spring/sleeve combo with a mongoose 4" 850lbs/in spring i put on it.

Cheapest ive found is a DNM unit:

In which i need 2. Ouch. Definitly looking for alternatives before i drop that loot.

I guess this is where i ask who has a possible 6.5" -7" mb spring laying around they wanna part with on the $free.99, ill cover shipping, lol.