"In the world of spuds today"

[mark.f]

I don't know what kind of school you go to SB15, but at our school, that is the advanced Grade 11 level. And by using that formula, I came out with an answer of 0.19635 units2

Are you using n=16 and r=10, (r being the radius of the circle the polygon is inscribed in)?

If so, then I don't know why you'd be getting that off of an answer. Are you in radian mode on your calculator?

That formula again is Area = nr²sin(pi/n)cos(pi/n)

Also, make sure you use parentheses correctly for the trig formulas.

[SpudUke5]

"In the world of spuds today"

Its getting warmer outside (at least where i live) so in the spirit of spring i decided to go shoot my advcanced combustion.

And let me tell you that i have been getting the performance that all of you guys talk about here. It worked out very nicely. My psi i add to my chamber is 62-63 psi and then after that i add air to the mix by opening the back and let the fan run for 2-3 seconds. Its getting that big bang effect even though my C:B ratio is 1:1 which was what i learned as optimal although .8:1 is also good. But either way, i am satisfied at how high potatoes can fly.

I would say that its airtime might have been around, lets say 10-15 seconds. Then it landed in my nieghbors front yard, luckily he wasnt outside. Now i gotta find a less urban area to shoot that beast.

Also my 4 inch piston valve should be done sometime soon. I have a 10 ft section of 4 inch pipe but i dont think i am going to use the whole thing for the chamber but most of it will be. I currently have a undersized barrel so i think i am just going to buy a 10 ft section of 3 inch pvc pipe rather than just a puny 4ft barrel. And i need a barrel support, any ideas besides wood?

[DYI]

I would say that its airtime might have been around, lets say 10-15 seconds.

Really? Because the SCTBDC can get an absolute maximum of 15 seconds hang time with a spud, and that's at about 1,100 fps, using what is likely a very optimistic drag coefficient.

[SpudUke5]

When do you begin to measure its airtime?

I never officially counted, but i guesstimated from the time of when it left the barrel. Im guessing that you count the seconds when it starts to fall after it reached the highest point it could achieve.

So then i would say that the airtime maybe 6-10 seconds? That sound reasonable?

[SpudBlaster15]

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

[SpudUke5]

Yay i got a supporter

This combustion shot was seemed to be a bit more powerful than some of the others. I watched it fly straight out of the barrel, then curve slightly because of the speed and its shape, then it ended up flying backwards.

But his was a just about complete vertical shot. But i did use a potato that fit 2 inch sch 40 pvc with a 114 inch barrel length, IIRC.

[DYI]

In the world of spuds today, I got some interesting equipment from McMaster-Carr (which had to go through USPS, Zep, UPS, Muskoka Delivery, Canadian customs, and a man by the name of Phil Wight to get here).

This includes all of the specialty bits for my new hybrid metering system, as well as a QEV that I got for a quick valve option (works quite well).

The gauges are, to say the least, quite impressive, with 4" faces and weighing about 2 pounds each, and that 1/2" ball valve has "2000WOG" printed on the side



A 4 000 psi $60 pressure washer handle is a bit of an overkill pilot valve for a 150 psi QEV gun, but it's been disused and needing a new launcher after I realised that it wouldn't seal with 2.4kpsi helium.



Quite fun shooting, but essentially the same as any QEV gun, and not worth making a topic about.



And finally, I present the new concrete breach for the SCTBDC. I don't like it when parts break at 500 psi, and I won't allow it to happen again.



Who said ABS bell reducers aren't rated for 500 psi?

[starman]

In the world of spuds today, I got some interesting equipment from McMaster-Carr (which had to go through USPS, Zep, UPS, Muskoka Delivery, Canadian customs, and a man by the name of Phil Wight to get here).

And finally, I present the new concrete breach for the SCTBDC. I don't like it when parts break at 500 psi, and I won't allow it to happen again.

LOL...OK I'm still laughing at that concrete chunk you have there...looks like you just unearthed your mailbox footing or something. Yes, 500 psi should be a breeze now.

Dang, customs is a bear isn't it. Are there no suppliers of this stuff anywhere in Canada?

[bigbob12345]

God i need to get my hands on one of those 1/2in ball valves rated to 2000psi.Then a 15x hybrid may be a possibilty. and a part number for it would be nice

[pizlo]

Ah DYI you can set my mind at ease, is that QEV this one?
Part: 6646K23
I know Mcmaster images aren't acurate, but it would seem that the pilot would be on top of the valve(in the position you have it there). So is this the one?

[DYI]

LOL...OK I'm still laughing at that concrete chunk you have there...looks like you just unearthed your mailbox footing or something. Yes, 500 psi should be a breeze now.

I don't half do anything

I haven't got the bill for customs yet, but last time it was more than the entire order had cost

@Bigbob: The ball valve is listed under "steel and SS" ball valves on McMaster, but I can't be bothered to look for a part number right now. The 1/2" valve cost $25.54, which might not be too easy to swallow with your current "pay". The gauges were a steal, at $35 each.

@Pizlo: there's only one type of QEV useful for spudding available on McMaster (the rest vent to the atmosphere), and that's the one I got. It is configured properly, as I've already shot it 10 times (and accidentally hit my neighbour's window once ). The port labeled "EXH" is what we would refer to as the barrel port.

[pizlo]

this is all I have to go on, and you have the number in my other post, is it this one?

[DYI]

Yes, it is.

I won't get around to putting the hybrid together until Saturday, as I'm not doing anything half-assed on the meter; if the weld on the back plate was bad and it broke off when I did a test fire, well...

The lowest that I can really expect this to work at is 5x or so, and even that may be pushing it. The reasoning behind a 0-15 psi gauge was that, after I make sure it works, I can cast concrete or aluminum around the whole contraption, and bring it to 20x (~12.8psi fuel pressure by the current thinking). That, and the 0-10 gauges cost more, and were less accurate

An interesting tidbit: the 0-15 gauge is so accurate across the whole scale that you can move it significantly by blowing on the opening, and its needle actually moves with natural changes in ambient pressure (as is evidenced by the fact that it can vary about 1kPa or so depending on the weather )

[Ragnarok]

INWOST, whether or not you noticed me leave, the 'Rok is back.
I've been in Spain since last Tuesday, and got back at stupid o'clock yesterday, so you won't have seen any posting from me since last Monday, as my laptop stayed at home.

The break itself was nice enough. The wind was a bit of a problem, but it was certainly good for sailing and kite flying - if not the bikes we hired.
Made the return flight a little interesting too, not great for someone like me who's not a fan of such things anyway.
Also ended up with, like I always do, sunburn. I'm particularly susceptible to such things.

Anyway, I'm back, with the usual shed load of nutty ideas.

An interesting tidbit: the 0-15 gauge is so accurate across the whole scale that you can move it significantly by blowing on the opening, and its needle actually moves with natural changes in ambient pressure (as is evidenced by the fact that it can vary about 1kPa or so depending on the weather )

Quite a weird effect, and one you'll only ever see in sealed gauges (glycerine filled or those filled with other fluids). A dry gauge, being unsealed, won't ever exhibit such a phenomenon.

...Yet another mildly useless piece of information.

[Jared Haehnel]

I did notice your absence hopefully you had a good trip 8)