Tool making day.

[nesikachad]

Totally non RC airplane related, but what the hell.

Whipped up a few sets of barrel spinners when my old cast aluminum bearing cassettes developed a crack. These are nothing new as barrel polishing centers have been around for a long time. Just a little different twist on an old idea.

You mount a rifle barrel between the brass centers and rub up against a belt sander/rouge wheel to put the bling bling on a gun barrel. The old standand ones are cast and have a nasty habit of developing cracks, which then causes them to break right as you finish up with a full mirror polish benchrest barrel and it goes cartwheeling across the shop floor-after it busts your face. (true story)

enjoy

[rcpilot82]

Nice Machine work! Just out of curiosity, what RPM are the barrels spinning in those bearings? Sounds like you need a flak jacket when doing that operation!

[askforplanes]

Nice work!

JP

[nesikachad]

Well, my square wheel grinder uses a belt that's around 60" in length.

Top RPM is 3600.

Gun barrels range from 1.15 to 1.25 in OD at the cylinder and from around .6 to 1 inch so lets say the average diameter across the length is .95

Pi x D='s c right? so .95x3.14='s 2.9"

we'll round that up to 3 inches. so a 3" C arc is making about 20 rotations for every one rotation of 60" abrasive belt. Multiply that by 3600 belt rotations a minute and that barrel can race upwards of 72000rpm by my math.

Is this really right? Can someone check this for me?

[CatalinaWOW]

Really slow response to math check request. The math is right, but the problem is wrong. The entire 60 inch belt doesn't rotate once per motor rev. The barrel rpm will be the ratio of the belt drive wheel diameter to barrel diameter (less slippage). Say 3 inch as one common size for drive wheel, so 3 times 3600 or 10800 rpm. Still damn fast. The surface of the barrel is going close enough to 33000 inches per minute ~ 3000 fpm = 500 fps ~ 350 mph.