Bill's Tip o' the Day

[hinote]

Here's a neat way to form a nearly production-looking bell, on your intake tube:

Go to a good exhaust shop that has a hydraulic forming machine. If you can find a guy with some experience, tell him you want a trumpet end on the tube--he can find the correct forming insert for the machine, and with a little extra care the work can be done in a minute or two.

In the photo, a piece of 2.25-inch OD exhaust tubing has been formed as described, and then carefully cleaned up on a belt sander and polished.

BTW use a heavy tube (we used 14 ga=.065 inch thick); the thinner stuff will split.

My guy was going to do it for free--but I tipped him some beer money, for next time.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[paul skinner]

It's a very good idea. And. I'm disappointed that so many people have read this post. Yet, have neglected to take the two minutes it would take to add a comment.

:(

[marksteamnz]

Bill can your muffler guy do the same on stainless exhaust tubing?
The tube expansion slip joints I had put in for a straight 6 header hook up could only be done on standard tube and only enough to get the ID of one 2" diameter tube expanded up to the OD of the next 2" diameter length.
Might of been the machine or a poor operator.

[hinote]

Bill can your muffler guy do the same on stainless exhaust tubing?
The tube expansion slip joints I had put in for a straight 6 header hook up could only be done on standard tube and only enough to get the ID of one 2" diameter tube expanded up to the OD of the next 2" diameter length.
Might of been the machine or a poor operator.

I haven't tried stainless yet.

The intake runs cool enough to justify the continued use of mild-steel exhaust tubing.

The operator needs to select an oversize forming tool; the "nose" of the tool is the part that does the job of forming the trumpet flare--and the tube will just expand to the oversize diameter, if the "correct" tool is used. You don't want the tube to slip past the rounded nose area, and onto the constant-diameter portion of the forming tool. I'd say the tool for at least 2 sizes larger is going to be correct for the job.

Bottom line is, find a guy who has lots of experience.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[hinote]

The intake runs cool enough to justify the continued use of mild-steel exhaust tubing.

Here's a shot of M8E, after its first 7 hot-runs.

You'll notice the intake still has its shine--as though it's still an unused part (red arrow).

The hot (stainless) portions have a beautiful patina--it's a sort of bronze, with a grey tone thrown in.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[milisavljevic]

Awesomely awesome! And your thrust stand is looking rather awesome, as well (this comment may not be valid in Quebec).

Störgröße M.
__________________
"That was not my dog."

[Dave]

NICE!

[larry cottrill]

Now THAT is an engine!

L Cottrill

[Viv]

Awesomely awesome! And your thrust stand is looking rather awesome, as well (this comment may not be valid in Quebec).

Störgröße M.
__________________
"That was not my dog."

Quebec is now a comment free zone:-)

Viv

[Mark]

Nice lines. It has a modern look about it.
Mark

[Mike Everman]

I'm pretty sure I could hear it from here! Beautiful. Can't wait for you to come rattle the windows at my shop!

When i get a spare minute with the camera, I'll show you what happens when you try thin walled stainless in the hydraulic former. The gripper jaws really sink in, so a spud inside is required. For small flares, I've been putting a split collar around the tube and going at it with a ball-pien hammer. It comes out surprisingly nice.

[hinote]

Here's a neat way to form a nearly production-looking bell, on your intake tube:

OK guys--here's your chance to be doubly-bored:

Please see the attached photo.

It's a shot of 2 different sizes of exhaust tubing, both flared the same way (at the exhaust shop).

I want to reiterate that these parts are very production-looking in appearance.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[hinote]

Please see the attached photo.

It's a shot of 2 different sizes of exhaust tubing, both flared the same way (at the exhaust shop).

I want to reiterate that these parts are very production-looking in appearance.

BTW nobody has asked about the polishing method.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Mike Everman]

Wow, how about that polish?

Wow, how about that polish?

[hinote]

Wow, how about that polish?

Wow, how about that polish?

Thank you, thank you veddy mooch!! (bowing deeply)

I've discovered a pretty neat polishing device.

It looks a lot like a standard wire brush, like you'd mount in a drill or drill press. BUT, it's not.

Made in France, and sold at OSH stores in the US (and probably elsewhere), the "wire" parts aren't wires at all, but spikes of some kind of polymer (nylon?-or?) with an abrasive imbedded in them.

The resulting assembly can be spun lightly against a metal surface, and the abrasives do a great job of removing surface oxides and imperfections. I use 2 grades: grey in color (medium coarse) and orange (fine).

Note: It took me a while to realize that you can't force this product against your work piece; the result of that is a buildup of heat--and the polymer melts and coats the surface of your nice part!! A light touch and continuous movement yields the desired result.

Try it--you'll like it!!

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."