Testing the RRC3 Altimeter

So I've read about hooking up Christmas Tree lights, the small ones, to the Pyro Terminals
and using a Vacuum Cleaner to test the Altimeter. Drogue lights up first then a few seconds
later the Main lights up.
Not in my case:
Both light up at the same time. One time the Altimeter was beeping out an altitude but came
short of the last digit or maybe not. It beeped out 497 then the low buzz occurred.

Has anyone experienced this from their RRC3?
I take it it's not a successful test having "both" lights come on at the same time?

JP

JP, your test sounds like it worked as supposed too. If you didn't change the main default that's set to main deploy at 500' you will get both drouge and main firing the same time reading that it beeped out an altitude of 497'


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ksm2001 said:

JP, your test sounds like it worked as supposed too. If you didn't change the main default that's set to main deploy at 500' you will get both drouge and main firing the same time reading that it beeped out an altitude of 497'


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Click to expand...

Ken,
That's fantastic news then! I was afraid something might be wrong.
No I haven't changed the default settings of 500' AGL Main Deployment.
Again thank you!

JP

Yes, you should try to draw more vacuum with your test fixture to get a higher apogee altitude. Also, the RRC3 has a very comprehensive flight simulation capability available through the PC interface. I have used that extensively for testing.

Instead of using a vacuum cleaner, I just put the altimeter in a glass, put a latex glove around the top of the glass, hold, and pull. This simulates a vacuum. I have had results similar to what you described but have also simulated flights to 900'. However, with whatever method you use, disengaging the vacuum will simulate an instant drop in altitude so you will likely see your main fire quickly after your drogue.

dixontj93060 said:

Yes, you should try to draw more vacuum with your test fixture to get a higher apogee altitude. Also, the RRC3 has a very comprehensive flight simulation capability available through the PC interface. I have used that extensively for testing.

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More vacuum, I thought I was doing good with that. The machine was almost completely sucking no air from the room.
I sealed up the screw switch holes and 2 of the 3 vent holes just to get the lights to come on.

The Rocket is the Magnum III, 5.5" diameter. I drilled three 3/16" vent holes. Maybe I need slightly larger vent holes?

I've got the LCD Terminal I can use, still, I have lots of reading to do with these 2 devices and I've ordered the RRC2
as a "back up" Altimeter.

I'll do this a few more times to see if I can get higher readings.

JP

Oh, you are testing inside your av-bay? You really need to make a chamber out of a see-through jar w/lid.

I had similar issues while testing my RRC2+. As Tim said what you need to do is build a pressure/vacuum chamber to test it.

I've built two, the first is a large one, big enough to fit an entire av-bay in it. I use a hand pump to draw out the air by connecting it to the rubber tube. It's not a perfect air tight container though, so I can only simulate to around 2500' or so. I use it to test the entire av-bay setup


The second is much smaller (again I use a hand pump to draw out the air), and way more airtight (I can simulate altitudes to almost 40K). I use this one to test the altimeter on it's own, as only a really small av-bay would fit inside.

Yes, I'm testing inside the Av-bay.

OK, second time around.
This time I got the Apogee to light up by itself and then a few seconds later the Main light lit up.
I'm satisfied now. Before, it was both lights at the same time that had me bothered a bit but the altitude it gave
was appropriate for that scenario.
This time I got 1,129'. Much better results!

I guess at this point I don't need to worry about a test chamber, with a reading like that.
Thank you for posting guys, all very good information.

*Do you guys think the three 3/16" vent holes are good or do you guys go larger?

JP

Yep, good enough.

dixontj93060 said:

Yep, good enough.

Click to expand...

Thank you, Thanks everybody!

I may do one more test just for giggles, mainly to see if I get more altitude...

edit to add; third vacuum test came out to 1,521'.
More than pleased with my Missile Works RRC3 Altimeter and the LOC Magnum 3.
https://www.missileworks.com/store/#!/~/product/category=5760485&id=25239688



JP

I picked up a medical vacumn pump at Goodwill for $20 and use mason jars for vacumn chambers.
i Have seen mason jars as big as 8-5/8" diameter and 12" high.
I added a small inline value so that I can slow my descent rate and I can get simulated altitudes of 45,000'

First, I have a question. Do people seal the connections between the lid, container, hose, and pump with petroleum jelly before pulling the vacuum?

JP, is that a 75mm motor mount on the Magnum? Looks like it has a boattail. Burt and Mike told me you were building the version with the central 54mm motor mount and two outboard 29mm motor tubes. You going to have it ready for September's launch?

RandyT0001 said:

First, I have a question. Do people seal the connections between the lid, container, hose, and pump with petroleum jelly before pulling the vacuum?

JP, is that a 75mm motor mount on the Magnum? Looks like it has a boattail. Burt and Mike told me you were building the version with the central 54mm motor mount and two outboard 29mm motor tubes. You going to have it ready for September's launch?

Click to expand...

I can't speak for others, but I just seal the connections with hot glue.

rocketgeek101 said:

I can't speak for others, but I just seal the connections with hot glue.

Click to expand...

That's what I do (except for the lid) and have a 100% success rate with testing. I'd recommend it
Nate

RandyT0001 said:

First, I have a question. Do people seal the connections between the lid, container, hose, and pump with petroleum jelly before pulling the vacuum?

JP, is that a 75mm motor mount on the Magnum? Looks like it has a boattail. Burt and Mike told me you were building the version with the central 54mm motor mount and two outboard 29mm motor tubes. You going to have it ready for September's launch?

Click to expand...

Hey Randy.
The Magnum 3 is built stock with the 75mm motor. Yes, I made a Tail Cone for it. Personally I think it looks more like a
rocket with a Tail on it.
I'll use an Aeropack aluminum adapter and borrow Mike's 54/1706 case.
I've ordered a few 38mm H motors for the LOC IV and one 54mm K550W. It's been a few weeks now and still no motors!
I plan to be there in September but won't launch the Magnum 3 until October or November.
If the motors don't come in it will be October before I get up that way...

I'm headed outdoors today to test the upper half with the Main Chute in it. My first time to do so. I hope the nylon screws
don't rip my tube! I added fiberglass and epoxy to each end of the tubes...

JP

rocketgeek101 said:

I can't speak for others, but I just seal the connections with hot glue.

Click to expand...

View attachment 182740

I am referring to the places where tube meets spigot, lid meets container, etc. I see that you use hot glue where the blue arrow points but do you use peroleum jelly where the red arrows point?

The reason that both lights appear to light up simultaneously with a vacuum cleaner is that the vacuum is pulled and released very suddenly. It's actually good for testing mach effects because the ascent looks like it's Mach 3 or so, but when you release the vacuum it drops nearly as fast. If you can download the data and graph it, you'll see what I mean; the main will actually fire one or two baro samples after the drogue, so you know that it's working properly.

A hand pump or something with a plunger is much gentler, and will give you a more realistic baro flight profile.

Good information here.

Got some Data from the Missile Works LCD Terminal from the tests performed using the Vacuum Cleaner.
https://www.missileworks.com/store/#!/~/product/category=5895759&id=25232679


Altitude 2,649'.

Max Velocity 1,278 fps

Drogue 77 fps
Main 1,550 fps

JP

Something to consider, and not expensive....