SpudFiles

I got to play with one of these the other week:
It's a basic co-axial pneumatic but fairly well made and can take up to 300 psi - and is freakin' LOUD the pilot valve was leaking so I lathed a new stem, worked like a charm

It got me thinking.

It's a basic co-axial pneumatic but fairly well made and can take up to 300 psi - and is freakin' LOUD the pilot valve was leaking so I lathed a new stem, worked like a charm

Sweet!

Hey, Jack. Cool! Did you get to fire a t-shirt? That particular t-shirt gun retails for about $700 (including a nice looking case) and the sellers say it will shoot a t-shirt up to 150 feet.

Do you remember the approximate size of the chamber and barrel? I would ike to run it through GGDT.

700 USD for that? Now I don't feel bad about my pricings at all.

grumpyoldman wrote:Did you get to fire a t-shirt? That particular t-shirt gun retails for about $700 (including a nice looking case) and the sellers say it will shoot a t-shirt up to 150 feet.

First test at 300 psi caused considerable hearing loss, to the extent that I didn't do it again without the barrel muffled. Did I mention it was loud as f*ck I did however shoot a tyvek coverall into my colleague's chest at 100 psi and he didn't flinch, not very impressive.

Do you remember the approximate size of the chamber and barrel? I would ike to run it through GGDT.

The chamber was about 4 inches long and 2 inches inner diameter, while the "barrel" was a 1 inch inner diameter. The clear barrel was about 4 inches inner diameter and about 12 inches long.

700 USD for that? Now I don't feel bad about my pricings at all.

It's well made with machined parts, so it's not a bad price especially with their warranty. It was weird that they brought it to the shop though, I charged the equivalent of 65 USD for the repair.

Tipman paintball guns are well made too and with a life time warranty, a low-mid end doesn't cost 700 dollars.

wyz2285 wrote:Tippmann paintball guns are well made too and with a life time warranty, a low-mid end doesn't cost 700 dollars.

Tippmann paintball guns are made in vast quantities, assembled in the US from parts mostly made in Asia, and they carry a 2 year warranty. You can't really compare them to t-shirt launchers made entirely in the US in small runs. Remember, if you are doing custom work that no one else is doing, then it is valuable - don't feel bad about charging for your expertise!

Remember Charles Proteus Steinmetz.

Henry Ford was thrilled until he got an invoice from General Electric in the amount of $10,000. Ford acknowledged Steinmetz’s success but balked at the figure. He asked for an itemized bill.

Steinmetz, Scott wrote, responded personally to Ford’s request with the following:

Making chalk mark on generator $1.

Knowing where to make mark $9,999.

Ford paid the bill.

jackssmirkingrevenge wrote: The chamber was about 4 inches long and 2 inches inner diameter, while the "barrel" was a 1 inch inner diameter. The clear barrel was about 4 inches inner diameter and about 12 inches long.

Thanks, jack.

I ran it through GGDT and couldn't get it to anywhere near 150 feet. With a lot of tweaking, I only got it to about 90 feet. Me-thinks the sellers might be embellishing a bit. I used 155 ounces for the weight of the t-shirt to try and compensate for the aerodynamically challenged projectile. I think I saw that weight number on one of tech's GGDT images on the forum and it seems to work ok.

What number did you plug in for the drag coefficient?

jackssmirkingrevenge wrote:What number did you plug in for the drag coefficient?

I put in 0.5 psi for projectile friction.

edit: Also 1 inch port.

jackssmirkingrevenge wrote:What number did you plug in for the drag coefficient?

I put in 0.5 psi for projectile friction.

edit: Also 1 inch port.

edit again: I tweaked it a bit more.

The tweaks I made were:
Projectile:
Friction - 0.0 PSI
Weight - 135 ounces

Chamber:
Outer Diameter - 2 inches
Inner diameter - 0 inches

I made it a toolie so there's more room in the chamber. The Ballistics Calculator has it at 86 feet.

Here's a pic of GGDT:

135 oz? That is one heavy t-shirt!

Here's a more realistic model assuming that the t-shirt is somehow rifled and doesn't flip end-over-end:

I fine tuned it a bit. I changed the drag coefficient to 1.19, used CO2 instead of air. That gets it to 150 feet to match their advertised max distance. Now I can better design my t-shirt launcher. Thanks!

grumpyoldman wrote:used CO2 instead of air.

I would advise against it, you might get more shots per fill for a given tank volume using CO2 but HPA/Nitrogen is much more consistent and kinder to your internal components.

jackssmirkingrevenge wrote:
I would advise against it, you might get more shots per fill for a given tank volume using CO2 but HPA/Nitrogen is much more consistent and kinder to your internal components.

I would rather use HPA but in a commercial launcher I believe it should be able to use both. HPA bottles are much more expensive and CO2 is more readily available. Correct me if I'm wrong. Thanks again for all your help.

grumpyoldman wrote:I would rather use HPA but in a commercial launcher I believe it should be able to use both. HPA bottles are much more expensive and CO2 is more readily available.

Like most paintball guns the same design should be able to use both. An HPA tank is more expensive to buy, but usually cheaper to run - and if you buy a $700 launcher, shelling out an extra $25 for an air tank shouldn't be a big deal

Thanks again for all your help.

Pas d'trouble