Types of Schwinn frame construction

[AS-1]

Thanks @AS-1 for adding these photos to this thread for me. The three parts are Salesmen's samples that were handed out at a sales meeting when Schwinn introduced the new frame building that would be done at the "then new" Greenville, MS factory. They show the way that that the new single piece head tube was investment cast. The lugs are crisp and clean, no clean up or fitting was required as this was a precision cast part. Just insert the "prepared frame tube", heat it up to melt the brazing slug, and it was ready for paint.

The bottom bracket is interesting in that it has two steel threaded sleeves inserted "after" the case part was made. The sleeves have four large spot welds (two on each side) securing them to the cast part. The casting is the same as the head tube.

The seat lug is also investment cast. But it has a steel "crush tube" added inside the area where the seat post clamp bolt would be placed. The steel stiffener (crush tube) is TIG welded to the cast lug to hold the very small part in place during the frame building and heating process. After the frame welding was completed, "All of the TIG Welding" was cut away when they slotted the back of the seat tube to allow the clamp bolt to tighten the seat post.

These are visual samples of what I call the Uni-Lug design that was used on every "steel framed" bike built in Greenville. This was to be the next generation of Schwinn's "after Electro Forged" production ended.

John

(added per request from John)

 

[Schwinn Sales West]

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(added per request from John)

These are examples of the conventional lugs that Schwinn used on the Paramount models.

The Red head tube has chrome plated Nervex lugs from an early 1970 23" P15 that I wrecked in the early 1970's when a car pulled out in front of me at 25 MPH while riding home from work on Northern Ave in Phoenix. Nervex lugs (as were most early lugs from all sources) were stamped in a right and a left-hand side. Then they were carefully welded together. It was the same way an Electro Forged head was made only using much thinner material. The downside was they were not very precision and required a fair about of hand clean up and filing, especially if the frame was to have the "chrome plated" lug option. It shows the strength of the lug and soldered joint. The lugged joint did not fail, and the impact force was transferred back through the joint, into the thicker end of the Reynolds "double butted tubing". Damm......I wish I still had that pretty bike!

The Yellow and Blue lugs are the actual "low melting temperature" plastic/wax? slugs that were spray coated with a white ceramic material. After the ceramic material dried, it was placed into an oven and the plastic/wax? melted out leaving an internal void of the exact three-dimensional shape of the lug. These were samples of the lugs used on Paramount's during the 1980's, and I believe they were supplied to Schwinn (at Waterford Cycles) from Henry James(?) if my memory is correct.

The grey part is the actual Investment Cast "slightly rusted" steel lug made from a Blue Slug. It is a clean, and a very accurate steel version of the plastic/wax? model slug. This lug is ready to be assembled into a frame. The tube inside dimension is accurate and tight to a frame tube.

Thanks again to @AS-1 for helping out in posting these photos to help visualize the topic.

John

 

[cyclingday]

 

[SirMike1983]

Were the pawn-shaped early lugs on the Paramounts produced here in the US or were they produced in England and imported?

 

[Schwinn Sales West]

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That photo is from the earlier "steel" quality board that hung in most Schwinn dealerships. I have the next "newer version" which used a wood "Masonite" silk screened back board (not steel) and they dropped the Electronically Forged verbiage on the newer Sales Promotion tool. It's interesting to compare the subtle differences that occurred over time. I have no idea why?

Also, the "parting weld joint" (what Schwinn called Electro Forged, or resistance seam weld) seen on your bottom bracket shell is completely ground smooth on the shell that was shipped with the newer 1970's Quality Board. Again, I have no idea why, and never thought about the subtle differences.

John

 

[Schwinn Sales West]

Were the pawn-shaped early lugs on the Paramounts produced here in the US or were they produced in England and imported?

It's my guess that English companies supplied a lot of the early Schwinn three piece cranks, caliper brakes, and frame lugs. I do not believe enough sales volume warranted a U.S. company investing into the tooling. It was more cost effective to purchase from a vendor.

John

 

[coasterbrakejunkie1969]

There have been questions about the Schwinn claim to a heavy duty frame on some of there HD bikes. I understood there to be additional brazing on the cantilever welds. My '64 and '65 Heavy Duti bikes have extra, when did they stop brazing the cantilever bars? There is issues with mid '70s and later HD frames not having any extra or only in one spot. I wondered if the stoppage of brazing the cantilever bars coincides with the frames no longer being reinforced.

 

[Rusty Klunker]

If it's about a Schwinn frame, it's all good here.

Is this a question, or comment? Millions of Schwinn's were built with some or full brazing. It would be too costly to tool up and build a handfull of low volume Cycle Trucks, Paramount Tandems, etc. The brazing was the fastest, cheapest way to do custom items in low volume. The brazing process does not produce "hot metal splatter" (from electronic welding) and is easier/faster to clean up for painting. Again, it was all about production, faster, easier, less time. The forged forks were outsourced by Schwinn. Schwinn purchased the forged legs (without the threaded stem) from Ashtabula Bow and Socket Company. Schwinn then welded their own stem onto the forged legs. The weld was by Butt Welding/Resistance welding/ or Schwinn's term Electro Forged. It was easier to just braze the Cycle Truck kickstand bosses onto the forged legs. Cycle Truck sales volume was a drop in the ocean compared to Schwinn's annual volume, so they made the best choice of how they did certain processes by the cost versus volume factor.

John

I saw when the tread was first started then wasn't on for a few days... didn't expect it to grow.
I didn't want to take it in another direction.

But I have found add on items brazed on including kick stand mounts that weren't a repair, they had factory paint.
The CT has a lot of brazing on it the only thing I'm not sure of was the lower sign tube.
I haven't stripped any down but wouldn't be surprised if the additional welds on the HDs are brazed too.

 

[Schwinn Sales West]

I saw when the tread was first started then wasn't on for a few days... didn't expect it to grow.
I didn't want to take it in another direction.

But I have found add on items brazed on including kick stand mounts that weren't a repair, they had factory paint.
The CT has a lot of brazing on it the only thing I'm not sure of was the lower sign tube.
I haven't stripped any down but wouldn't be surprised if the additional welds on the HDs are brazed too.

This thread was started on Monday night at 11PM PST, it's not even three days old as of this point. I think you might have it confused with the Heavy Duti frame thread.

We are discussing all types of Schwinn Frame construction used over the years, not any specific Schwinn model.

Thank you for your interest.

John

 

[coasterbrakejunkie1969]

This thread was started on Monday night at 11PM PST, it's not even three days old as of this point. I think you might have it confused with the Heavy Duti frame thread.

We are discussing all types of Schwinn Frame construction used over the years, not any specific Schwinn model.

Thank you for your interest.

John

Did Schwinn discontinue using brazing or was it used through out there time in some capacity? Would there always be the ability to add brazing to a weld?