IRIS plans - confusion!

[Balltip]

Okay - I guess that a few of you might already have noticed that I am totally stuck on the IRIS sounding rocket! Well... so be it then!

Anyway... I am in the progress of scaling down a drawing using BT70. The drawing can be found, amongst other places, in my old IRIS build thread in the LPR section

But... the Horror!

I have tried to gather as much info as possible about the IRIS but I have missed one thing - and it makes me wonder what data I should be using for my next build!

So back to the above mentioned drawing... I rummaged through the IRIS folder on my 'puter and decided to make a few print outs (due to some program crash I have not had a printer installed for quite a while) and besides the mentioned drawing I also printed out this one:

https://plans.rocketshoppe.com/centuri/cenKC-14/Iris.pdf


And now, comparing the two, I find that the BT dia is off by .75 inches between those two.

Anybody got any idea on what drawing is the (most) correct one???
A faulty measurement by a rough 6% is baaaad trying to make a scale model!

 

[Balltip]

I might as well attach the other drawing here as well - so that you who reads this don't have to go looking for it!

 

[PopRocket]

Balltip, the information I have shows the IRIS sustainer to have a diameter of 12 inches (30.5 cm).

 

[tbzep]

Yep. Peter Alway's R.O.T.W. shows 12" also.

 

[rocketguy101]

Not sure if the "Hydra-Iris" is the same, but this brochure shows a dia of 30.8 CM (12.126 IN)

pg 1 first

 

[rocketguy101]

pg 2

 

[Stymye]

the- hydra- version is three finned, but it's still 12" diameter. atleast the sustainer is.

 

[melvyn]

Originally posted by Balltip
I might as well attach the other drawing here as well - so that you who reads this don't have to go looking for it!

Interesting... if you convert the metric units to inches (is, multiply the metric dimension by 39") the dimensions listed are all a little off. For example, the payload diameter is listed as 0.32m/12.5", but 0.32m is 12.48"; close enough for an illustration. The booster, however, shows 0.30m/12"; 0.30m is 11.7". Conversely, taking the imperial units and converting them to metric shows a little more accuracy. I can only conclude that the diagram in the IRIS Performance Summary document isn't totally accurate, but if it was written for committee approval, the readers wouldn't really care if the payload section is 12.5 or 12.48". I think the Centuri dimensions are also a little off, but for their needs are close enough, although the IRIS has bands around the airframe which may be enough to bump the overall diameter to 12.75".

Does anyone have any dimensioned drawing from Atlantic Research?

 

[rocketguy101]

Originally posted by melvyn
I think the Centuri dimensions are also a little off, but for their needs are close enough, although the IRIS has bands around the airframe which may be enough to bump the overall diameter to 12.75".

I found an old NARTS scale data plan for the Iris, dimensioned by G. Harry Stine. The text in that plan states the Iris is 12.75"--I wonder if he was getting the dimension from that band? I also wonder if the Centuri dimensions came from G. Harry?

 

[Micromeister]

From my field notes at Goddard Space Flight Center for the last known example of the Iris the circumference just above the fin area and just before the weld ring at the forware transition to the nose cone are both 38.75" (12.3334" dia.) I have No way of knowing how many layer of paint this includes

From my SP 16 Iris Packet from Narts. both 11 x 17 drawings show the steel motor tube (main dia) as 12.162" dia.

Hope this helps

 

[Balltip]

It seems to me that there are no definite answers, but I do have a theory...
You will have to excuse me for - maybe - sounding a bit weird, but I will blame the fact that I am tired and that English is not my native tongue.


The most "hands on" measurements that we got are those given by Micromeister and those does carry a risk of being off, just as he says, due to the paint that has been added to the display rocket over the years.

If we follow that lead and assume for a while that the drawings that Micromeister have are accurate, then the added layer of paint would be roughly 2mm (or 0,0857") on each side. That does seem to be fairly reasonable, does it not? (measured 12.3334" - 12.162" = 0.1714"/2 = 0.0857")


The one thing that bugs me then is the diameter of the bands...
Because if we assume that the measurement of 12.75" is the proper diameter at the bands then we get 12.75" - 12.162" = 0.588"/2 = 0.294"
They would then have had to manufacture the bands from material being 0.294" thick.

To me that last measurement seems to be wrong... I do not know for sure but I assume (yes, I do assume a lot here LOL!) that 0.3" steel would be available over the counter at any good hardware store. It seems a bit unlikely that they would have stayed away from standard materials making parts - if the materials were easily available, why not use them?
So would it be nuts to imagine that they just went out and bought 0.3" steel for the bands?
Assuming they did, then either the BT dia of 12.162" is off, or the 12.75" diameter over the bands are.

To me it seems that a BT dia of an even 12" would be faulty too as the bands then would have to be 0.75"/2 = 0.375" thick. Not to mention that the paint layer would have to be over 4mm thick (or 0.1667") - again I am using Micromeisters measurements as a base for my assumptions.

The truth is out there - all we have to do is to sand blast the last IRIS and measure her nekkid! But that seems to be something they would oppose at Goddard...


But for my own use I will assume that the proper diameter of the IRIS sounding rocket was 12.162" + the missing 0.012" from the bands. Leaving me with the number of 12.174" as being the pure and proper BT dia of the IRIS sounding rocket.


Per





...yes, I am a nerd!

 

[tbzep]

Peter Alway is a master of scale rocketry has worked for the U. of Michigan in physics(smart) to boot. I'd imagine his measurements come from good sources, or if he had to measure the specimens himself, was able to factor in the paint situation. If he says the original was 12", I'd run with it.

 

[Stymye]

are you building something for scale competition ?

if so, stick with the data you have and provide that for the judges

 

[Micromeister]

I fully agree with stymye:
if your entering a competition, your model MUST match your data.

the Bands are just that, Steel Banding with tensioning metal standoff blocks. These details ARE accurately drawn in the NARTS packet, and match up very well to the Goddard example.
Peter Away will be the first to admit sometimes he like all of us who do Scale modeling has to make assumptions based on conflicting data.
It's my personal belief that the raw motor steel casing we are discussing was UNDER 12" actually (11.832" dia) from an unnumbers Atlantic Reasearch corp Drawing. After painting it came up the the 12.162" dia. we're using as a base line. Given a couple coats of primer and at least two color coats.. this discrepency(sp) isn't that unreasonable.
The reason I can't be sure of the number of coats of paint remaining on the Goddard Example is Its an artifact, I cant deface it to get an exact thickness. but as nearly as the goddard records show it's been painted at least 4 times possibly 5 or 6
the two forward bands are 1.1" wide while the rear band is 1.65" wide directly over a raised 3.67" casing reinfocing weld band
This photo is one of the 2 screw clamps and 1.1" banding detail, it may help you guys see what is actually happening at the fin attachment bands. The banding by the way is .080" thick. the 2 screw clamps are however 1/4" (.250") thick.

 

[moonboy]

Hello Guys,
Check out www.meatballrocketry.com The website has data on a small scale iris done at a Bt-60 size. It is in scale section.
Moonboy
"Where's my Pink and yellow rocket?
soon to be on tv friday 3pm Est on discovery channel.

 

[Balltip]

Okay, you win LOL!

Yes, I'll stick to 12" then

And no, I am not entering any scale competition with my oncoming build - I am just looking for what could be considered to be the best data available as I am planning on stretching my building skills as far as I possibly can on this one.
It would feel strange to not look for the most accurate data, that's all.

I am looking to make the fins taper the right way, make the nuts and bolts show (those are hex head, right?) and... well - everything! And it is this "strange" place full of of "strange" people (yes, that would be TRF
) that has influenced me! (For which I owe you all!)

So, maybe I should start building instead of writing? Yes, probably.

Thanks for your replies, all!

 

[rocketguy101]

Originally posted by Balltip
Yes, I'll stick to 12" then

Man Law?

 

[Stuck Fingers]

Man Law!!!!!!!!

 

[tbzep]

Originally posted by rocketguy101
Man Law?

LOL!

 

[OverLord]

MAN LAW!

 

[mrbusdriver]

If I read everything I have collected on the Iris correctly, the nose cone (and optional payload section, I think) are slightly larger diameter than the 12" propulsion section. It's the extra .75" there...
I'll see if I can fing the link than shows it...
Dave
here ya go... https://www.yellowjacketsystems.com/alway/eighteen/iris.jpg

edit...well, buggars...you have the original ARC drawings there (and my link above as well), of the Hydra and original model. I'd guess that might be the best source, tho it doesn't indicate the slightly larger diameter payload/nosecone. Not to say it's not there. I now see the midsection band in the photo as shown in the Hydra drawing, was it on the original 4 finned model as well? I don't see it in the standard pic.
A scaler's nightmare!