1970 Schwinn Heavy Duty

lennyharp · #1 (**permalink**) 08-12-2008, 01:09 AM

These photos are my remedy of a cruiser frame not quite fitting the motor. I am just a little slow and started today with a few bikes I could mount a motor on. I chose the one that needed the most modifications. This will be a temporary replacement for the bike I crashed 2 weeks ago tomorrow.

**Bikeguy Joe** · #2 (**permalink**) 08-12-2008, 08:29 AM

Nice... Keep us updated (with pictures of course!)

jasonh · #3 (**permalink**) 08-12-2008, 01:04 PM

Pretty cool.

I'm curious as to why you chose to braze the brace on instead of welding? (at least that's what it looks like you did)

lennyharp · #4 (**permalink**) 08-12-2008, 03:11 PM

Brazing was the preferred way to build quality frames for a long time. Schwinn even makes their frames look brazed at all levels of quality 1940-1980 era and maybe more. Fillet-Brazed Schwinn Bicycles 1938-1978 is an article that talks of Schwinn quality but I know Colin Lang who uses brazing exclusively and has had his frames in the Olympics and world championships. I always regretted that he refused to take me on as an apprentice as he only wanted to apprentice his sons. But I do a fine brazing job and have a lot of this type of work I have done.

One reason to braze is that you work the metal at a cooler temperature. Welding temperatures crystallize the chromium in 4130 cro moly steel. This is also one of the preferred metals for bicycle frame fabrication. Frame builders who braze use a lighter gage butting because they can get away with it. Welders use about 40% thicker butting because of the loss of strength to crystallization problem. It is a trade off because Brazing takes either a fillet of brazing rod or lugs for the cooler temperature silver brazed frames. All this detail is what makes me want to braze a fillet similar to Schwinn and some of the bikes I have appreciated most.

jasonh · #5 (**permalink**) 08-12-2008, 03:22 PM

Good to know. I had heard about the crystallization thing, just didn't know how accurate it was.

Your brazes do look really good btw.

lennyharp · #6 (**permalink**) 08-12-2008, 04:09 PM

Thanks JasonH, I am waiting on the paint to dry and bake at 110 in the sun. This is an advantage of desert dwelling. I hope to get it built and running tonight. Nothing fancy from here out I think as I have a buyer who wants just a basic bike and I can use it as transportation till it is broken in.

datz510 · #7 (**permalink**) 08-12-2008, 07:44 PM

Hey Lenny, looking really good!! That is going to make mounting the engine very easy to do.

Large Filipino · #8 (**permalink**) 08-12-2008, 08:23 PM

It will make it strong too. When your front mount actually hugs the frame,you'll NEVER get sheared off bolts.

lennyharp · #9 (**permalink**) 08-13-2008, 01:19 PM

Well I got it together today after some advice & help from datz510 last night. I cruised up and down the street popping the clutch with no spark I could hear with blue to blue wires and black to black, or blue and black mixed. You can see on the non gear side of the crank where I had to heat and bend the crank arm out about an inch to clear the motor and exhaust. The pedal wobbles a bit but since clearance is good I will leave it as is. I opted for a BMX bar and stem for upright sit and strong solid mounts for everything imaginable.

jasonh · #10 (**permalink**) 08-13-2008, 01:33 PM

Bike looks good. Lower that seat, and it'd be a comfy cruiser

I need to get some higher handlebars like that for my bike...

So onto the no-spark issue....have you tried pulling the plug and laying it on top of the head and just pick up the bike and spin the rear to make sure there's no spark? If you connect an AC voltmeter to the blue and black wires, you should see the needle (or numbers if digital) jumping around as the motor turns. Is this a brand new kit?