Monday, March 30, 2020

Manufacturing processes

 These 1960's chopper pipes were on display at the Motorcyclepedia museum in Newburgh NY when we stopped there last fall. I don't find them  attractive but I'm curious about the process used to make them. I'm not sure how a piece of 1/3/4 or 2" diameter 16 gauge steel tubing could be put into three full twists and remain that regular in appearance. Heat must be involved? Ideas?


JP said...

Something like this:
I used to operate the "torsadeuse" when I worked at ornamental ironworks, it would twist 2" solid square section mild steel like putty. The trick was to judge the mandrel's inertia and stop it with the ends dead square to each other.
The bottom pic looks like a different technique ?

Mister G said...

Impressive. It's just brute force under control. Would that machinery have been available 50 years ago? The video makes the job seem trivial. I wonder what the short piece of square tube that he put inside the round tube is for.

JP said...

I think it might have existed back then. The machine I used already looked ancient in 1985.
By the looks of it, the bit of square tubing helps to pinch the round tube in the jaws of the "puller" carriage.

rats said...

Dang, that's a cool video and machine. Thanks for sharing.

I asked a buddy, and his response was:

"End round tube sections welded to centre square tube section, then centre section heated red and twisted in a lathe or suitable jig to keep it straight... "

Given that these gaudy twisty chopper pipes were probably (hopefully) made in small quantities, and using low-tech means, I think he hit on the likeliest answer.

Don in Oregon said...

The short piece of square bar stock is placed inside the round tube so the machine can crimp the round tube down onto the square bar, in order to grip it to apply the required torque.

Mister G said...

Thank you, all makes sense.