Schwinn handlebar dissection

[rickpaulos]

For an art build I was sawing some handlebars off just by the center bulge and I found a surprise in a Schwinn dropped bar.

Schwinn dropped bars from a Varsity (probably) model number 7887, 39cm dated 1977.

The other unbranded bars were pretty similar in shape and size

There is some sort of liner/insert in the center bulge in the Schwinn bars! The liner seems to be tapered as well.
Was this an intended reinforcement or a sacrificial part during the manufacturing process or a broken off tool? I'll be sawing another set of Schwinn bars in a few days to compare.
BTW, Wald bars aren't bulged out, they have a c-shaped shim welded on instead.

Schwinn bars on the scale at 1.438 pounds, wall thickness about .050"
unbranded bars at 1.502 pounds, wall thickness about .054"

 

[rickpaulos]

I pulled 3 more Schwinn Varsity bars out of the parts bin

the one above and the 3 have the following numbers on them:

7887 - 73
7887 - 75
7887 - 25 - 76
7887 - 39 - 77

I'd say the last 2 digits are the year, if it has a second that may be the week of the year but certainly not the size as I was guessing above. I have some 20 to 40 more I could review. And then there are the upright bars on the Collegiates, Suburbans and the sting rays and the typhoons and......

Sawing commences on sunday for the 3.

Bonus photo. Another use for those spare dropped bars.
Once bolted to the studs in walls, they are useful for hanging coats, helmets, extension cords and other large items.

 

[68z27]

Interesting bits of information that may (or may not) give some insight into the manufacturer's thought process. Thanx.........
BTW, I wonder how many different styles of handlebars Schwinn made?

 

[rickpaulos]

3 more Schwinn bars cut apart for inspection.

7887 - 73 1.400 pounds 0.050" thickness*
7887 - 75 1.418 pounds 0.050" thickness
7887 - 25 - 76 1.342 pounds 0.045" thickness
7887 - 39 - 77 1.438 pounds 0.050" thickness

All 4 have the same insert. Thin on one end, thick on the other. So I'm guessing this is a sacrificial part from the manufacturing process. I think these bars were made before modern hydro forming became common place. I've also seen muffler/exhaust pipe expanders that use a series of wedges on a threaded rod with nuts at either end but to use one of those inside such a narrow and long pipe would surely be a problem. AFAIK, Schwinn made their own steel handlebars.

* hard to get exact measurements. The bars are gas pipe construction so the wall thickness varies as the sheet metal was bent into semi round shapes. And they all had some rust on the inside. The bar plugs should keep the moisture out but I've learned caps and seals are far better at keeping moisture in so they never dry out.