Old Schwinn Road Bike Chop Chop Build

I thought some of you may be interested in what's going on with my Latest build - I am doing some radical engineering to rig up a swing arm dual suspension bike.

First, I started with a gigantic road bike that was given to me, set up for very tall riders. I chopped the head tube and the seat tube, removing almost 4 inches of tubing.

I'm going to affix a 1/2" axle perpendicular to the seattube with heavy welded steel. The swingarm axle hold a welded double sprocket offset about an inch that will feed the left side 36 tooth sprocket, anchored via clamshell on a 24" wheel. The swingarm width will be 7 inches, with my custom hub being 6 1/2" wide. The hub will ride on a 1/2" axle! It will take something to break that.

I am shooting for a 47" wheelbase.

I did some test fittings on the frame to get an idea of how it would look.

I'll need to dish out some money for sprockets, tube and tire, stepup drillbit (to put 5/8" bushing into swingarm), and two shocks to support the swingarm.

I will be running a 1' piece of heavy Duty unistrut along but slightly below the top tube/ down tube interface. That will hold a spring saddle and grab the top of the shocks.

 

[gary55]

Man I really hope that seat tube is sleeved. Welding on a thin tube like what you've done above the u-bolt clamps weakens it a heck of a lot as well. And those u-bolts also weaken it a lot. Also replace that crappy fork, that thing will fail someday too. Not to be a dick, but I wouldn't ride that thing without a motor.

I rode with a dual crown, rigid chopper fork pretty much till now cause I couldn't find a suspension fork I could trust for a low enough price. Same goes for bicycles. I just removed a Fox Shox fork off my 212 schwinn that was rebuilt by some idiot for a 1" steerer. The steerer had cracked somehow in its fit in the crown and rocked back and forth in the crown. Upon braking the front wheel would move back 2 inches at the axle. Was very scary and actually got me into one low speed accident in a parking lot. I thought I could trust a Fox supposedly rebuilt by a pro, but even that failed.

He already sleeved the seat tube.

 

[Timbone]

Man I really hope that seat tube is sleeved. Welding on a thin tube like what you've done above the u-bolt clamps weakens it a heck of a lot as well. And those u-bolts also weaken it a lot. Also replace that crappy fork, that thing will fail someday too. Not to be a dick, but I wouldn't ride that thing without a motor.

I rode with a dual crown, rigid chopper fork pretty much till now cause I couldn't find a suspension fork I could trust for a low enough price. Same goes for bicycles. I just removed a Fox Shox fork off my 212 schwinn that was rebuilt by some idiot for a 1" steerer. The steerer had cracked somehow in its fit in the crown and rocked back and forth in the crown. Upon braking the front wheel would move back 2 inches at the axle. Was very scary and actually got me into one low speed accident in a parking lot. I thought I could trust a Fox supposedly rebuilt by a pro, but even that failed.

Thanks for the concern. Yes, the seat tube was sleeved and I welded some thick metal around the seam. Believe me, this is by far the strongest bicycle frame I have ever ridden, but that's the idea. I see these guys on here slamming 212cc motors on Huffys and others hitting 40 mph and higher on junk bicycle frames and wheels. That raises my eyebrows!

A few comments: I have ridden dozens of thousands of miles on 18 lb aluminum and carbon fiber road bicycles. I've seen more than a few frames fail. Rarely are these failures catastrophic. A crankarm failure can be catastrophic. An axle break can be catastrophic. A wheel can fail catastrophically. Usually, the feedback from a failing frame catches attention: chain will ghost shift and jump; bottom bracket will feel loose; rear wheel will feel like it's loose, etc.

This is an old cromoly frame, surprisingly thick tubing. Very strong. Even though flux core welding is not the best, the tubing responds pretty well. It can take quite a bit of heat. Lots of spatter and it doesn't look great, though. I would think that if penetration is OK, the stress to the tubes wouldn't show for a very long time.

The front fork is junk and that is precisely why I want to use it! It will last more than long enough until I get something better. With my saddle pushed backwards, the center of gravity will be way back so the bike will be light on the front tire - I expect it to kinda skip along on the road like on a Chopper.

I've built MBs on 3 frames and I never saw one that didn't exhibit some kind of failure. I even bought one of those $150 GT-2A frames and it failed in two places (motormount pedestal and on the downtube). This is what I am trying to avoid.

 

[Timbone]

I am nearing the end of the build and getting both excited and scared. This bike has to be absolutely 100% right or I cannot ride it. Everything looks and feels OK so far.

I did two STUPID things: on my very first pedal ride check I turned a corner and the bike felt very mushy. I had forgotten to put nuts on the top connections of the shocks and one jumped out. Duh.

A more dangerous problem happened later when I did my rear disk brake check. I never tightened up the dropouts and, although I was going slow, the first pull yanked the left end of the dropout, bending the disk rotor.

I made repairs, bending the rotor back to close to flat with a crescent wrench. I also welded another cross piece to the caliper adapter I welded to the left chain stay. There is so much pressure that comes with braking, so you really can't take any chances.

I have all the small stuff done. Brakes are good. Motor is in place, although I need to add one more spacer piece to the front motor mount.

My jag pipe will not come close to fitting. I may weld up something, fill it with steel wool and use it as a temporary.

Pedally feels funny, because the bike is heavy and I don't have a perfect chainline. I used an old derailleur from a donor bike on the pedal side so the chain is always taut. It's working so far!

Here are some pics:

 

[Timbone]

I have a motorized bike now. Still confronting problems. I had miscalculated the placement of the engine - has to push it a bit higher which changed by front motor mount set up.

Took another look at my plan for the seat - it wasn't strong enough. More fitting, welding and grinding.

Biggest problem was my offset sprockets. Due to needed offset, I was unable to get a good weld. So I drilled holes laterally and used 13/64" hardened steel studs welded at the ends. Not perfect but should be good enough.

I have a motor to swingarm axle chain, and a swingarm to drive sprocket chain; both chainlengths were awful. I dug out a half link for the sprocket drive chain and it's still not what I want. The smaller motor chain is much looser than I want to see, but there's no way I can remove a link. It will be easy to add a tensioner if needed.

Also struggling with my pedal chain. It wants to pop off. All these are little things but each one takes time to fix properly. I bet I have worked a minimum of 30 hours on this since Saturday. It has been a real struggle.

Tomorrow I should have it running. Hopefully things will go well and a good running bike will make me forget all this hard work.

 

[5-7HEAVEN]

Wow!

Looks like it belongs in the movie Mad Max Thunder Dome!

I love innovation.

 

[Frankenstein]

A thin spacer between the motor and old seat tube will take slack from the drive chain.

 

[Timbone]

A thin spacer between the motor and old seat tube will take slack from the drive chain.

This was great advice! Thanks, Frank!

I found a rear motor clamp from a very old kit, cut the "ears" off of it, ground it down for good fit, then sandwiched into the rear motor mount. Perfect result!

Here are some pics: the bike is 95% finished, ready to run. Can't get good spark from the CDI. Got a spark tester from Autozone - it shows about 26kV. I'm guessing I need at least 30 to fire the spark plug. I've ordered a new one and it's in the mail.

You can also see the front in muffler clamps that I made welding up pieces of 20g steel. They really bite in! Motor is super steady! 5/16" u-bolt on the front should be more than enough.

And there's a pic of the rear motor mount spacer. Worked like a charm. Thanks, man!

 

[Frankenstein]

View attachment 79688 View attachment 79687 View attachment 79684

This was great advice! Thanks, Frank!

I found a rear motor clamp from a very old kit, cut the "ears" off of it, ground it down for good fit, then sandwiched into the rear motor mount. Perfect result!

Here are some pics: the bike is 95% finished, ready to run. Can't get good spark from the CDI. Got a spark tester from Autozone - it shows about 26kV. I'm guessing I need at least 30 to fire the spark plug. I've ordered a new one and it's in the mail.

You can also see the front in muffler clamps that I made welding up pieces of 20g steel. They really bite in! Motor is super steady! 5/16" u-bolt on the front should be more than enough.

And there's a pic of the rear motor mount spacer. Worked like a charm. Thanks, man!

That I believe was advice from either Butre or crassius maybe even bakaneko, heard it somewhere and I adopted it and even used it, way easier than dorking around with half links and trying to put the tensioner somewhere where it doesn't want to be.

 

[Timbone]

Well, wherever the idea came from, thanks for sharing it. You guys are so helpful, especially when, say, a builder is stressing with problems and unforeseen complications and can't see the trees for the forest.

 

[Frankenstein]

Well, wherever the idea came from, thanks for sharing it. You guys are so helpful, especially when, say, a builder is stressing with problems and unforeseen complications and can't see the trees for the forest.

Don't sweat it, I'm currently adapting a 36 hole hub to a 48 hole rim, after hours and hours of trying to find a good lacing pattern with the spokes I had on hand I gave up and marked and drilled new holes that correspond with a 36 hole layout. I was at least able to reuse 6 of the previous 48 holes.

Now the trees moved to a new piece of the bike, if I have too much trouble I'll ask you to pay back one of the IOUs if you're capable.