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Rifled aluminum barrel vs PVC driveband?

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Rifled aluminum barrel vs PVC driveband?

Unread postAuthor: Alex345 » Mon Jun 10, 2019 10:49 am

This would be for a hybrid cannon. If the caliber would be 30mm using a 5mm (10mm also an option) thick aluminum tube firing projectiles with a PVC driveband; Would this be a durable design? Or would the aluminum rifling wear out too fast?
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Re: Rifled aluminum barrel vs PVC driveband?

Unread postAuthor: Moonbogg » Tue Jun 11, 2019 12:01 am

What's a PVC driveband?
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Re: Rifled aluminum barrel vs PVC driveband?

Unread postAuthor: Alex345 » Tue Jun 11, 2019 10:38 am

Moonbogg wrote:What's a PVC driveband?
Sorry, turns out the correct term is driving or rotating band, my bad.

It's used on artillery shells that are made of steel so they can't really use the rifling of the barrel. The driving band is a band that's wrapped around the shell near the bottom, and is made of a soft metal, often copper, into which the rifling can ding in.

Some machine guns and auto-cannons use rounds with a plastic driving bad because it makes the barrels last longer. Wich i why i was thinking of firing a steel projectile with a soft driving band like PVC thru an aluminum rifled barrel. Aluminum is quite cheap and easy to work on, which makes the whole rifling process a lot cheaper, faster and easier. If you could then keep this soft rifling alive as long as possible using the driving bands, that would be pretty nice.
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Re: Rifled aluminum barrel vs PVC driveband?

Unread postAuthor: Moonbogg » Tue Jun 11, 2019 1:20 pm

Thanks for explaining that. I wasn't familiar with that concept. It's kind of like a sabot but serves a different purpose. Pretty cool idea.
I have no idea how fast the rifling would wear out. Also, shoving the PVC sleeve into the rifling sounds like it could be a real pain in the ass. You'd have to hammer it in there, right? I'm sure it would work for a while at least.
Have you considered rifling the PVC instead and using the air resistance during flight to rotate the round? You could even come up with a simple way to heat a fixture and press it over the PVC to melt the grooves into the PVC or something like that.
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Re: Rifled aluminum barrel vs PVC driveband?

Unread postAuthor: jackssmirkingrevenge » Wed Jun 12, 2019 5:37 am

I think you'd need some pretty deep grooves in order to avoid the driving bands being stripped, and perhaps PVC isn't the best material either, I think something less brittle like UHMW would work better.

Synthetic driving bands are certainly used in some high performance machines, such as the 30mm projectiles fired by the A-10's legendary GAU-8/A cannon:

Image

You could even come up with a simple way to heat a fixture and press it over the PVC to melt the grooves into the PVC or something like that.


A pre-engraved driving band is probably a good idea, it worked well for the Kaiser Wilhelm Geschütz:

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