SpudFiles

there is a store almost a mile from my house that sells 2.5 in. pvc.... but its schudale 80. can i still use that?

Maybe, but it will be a really tight fit. In SCH 40, the fit is already pretty tight.

You should just take a tennis ball with you to the store and see if you can jam it in.

2.5" should be the inside diameter of the pipe, SCH 80 is just the wall thickness.

so a tennis ball should fit in any 2.5" bore tube.

ALI, 2.5" is the nominal outside diameter of the pipe. The actual OD is 2.875". Both SCH 40 and 80 pipe have the same OD but different wall thicknesses, and therefore different IDs.

ID of 2.5" SCH 40= 2.445"

ID of 2.5" SCH 80= 2.29"

So a tennis ball may not fit in SCH 80 pipe.

a really tight fit is good. right?

daberno123 wrote:ALI, 2.5" is the nominal outside diameter of the pipe. The actual OD is 2.875". Both SCH 40 and 80 pipe have the same OD but different wall thicknesses, and therefore different IDs.

ID of 2.5" SCH 40= 2.445"

ID of 2.5" SCH 80= 2.29"

So a tennis ball may not fit in SCH 80 pipe.

Really? in the UK, imperial pipe sizes always refer to the nominal bore, so 2.5" means a 2.5" bore, then our metric system refers to the OD, so 75mm pipe is 75mm OD.

it appears you are right http://www.engineeringtoolbox.com/pvc-c ... d_795.html

zach12 wrote:a really tight fit is good. right?

A loose fit is bad, because air can rush past the projectile, hurting efficenticy

A tight fit is bad, because friction will greatly slow down the speed of your projectile

You are looking for a firm fit. In my opinion, the fit of a tennis ball in 2.5" SCH 40 is the tightest fit that is still acceptable. 2.5" SCH 80 will be way too tight, and in fact, probably won't fit the tennis ball at all. Look for 2.5" SCH 40.

Yep sched 80 2.5 won't work...go sched 40 2.5. Also, as you shoot tennis balls, especially with a combustion, the fuzz will wear or burn down and they will fit in the barrel a little easier.