Need Advice on "H" Motor for Level 1 Cert

[Ronz Rocketz]

I still like the H115-DM sparky. That sounds awesome.

Shave off 1/32in for every second. If you want a 10 second delay, take off 4sec or 1/8in.

The case I’m using for my H135 is too small for the drilling tool, so I have to measure on a drill bit and insert until I hit the tape on the bit.

I asked our mentor why they use freedom units instead of metric. He said Sen. Thurman added in a funding bill the requirement for NASA to only use imperial. And that’s how we lost the Mars probe…

https://www.latimes.com/archives/la-xpm-1999-oct-01-mn-17288-story.html

 

[kjhambrick]

<<snip>>
Harbor Freight sells a digital scale that goes to about 11 pounds for $20 grams, ounces, or pounds.

Nice @dmaaero !

There are actually two models under one page for $19.99 ( CEN-TECH model 95364 and CEN-TECH Model 61641) at Harbor Freight - CEN-TECH Digital Scale

I can't determine the diffs from their web page but I need a new scale with a little more capacity so I am going to go take a look next time I am in Georgetown !

Thanks !

-- kjh

 

[bjphoenix]

H123 (RMS) is a perfectly good motor for level 1. It won't tax your construction that much, it will be easier to follow the rocket in flight, etc.
A person can make their L1 attempt easy or difficult. I use a 4" diameter rocket essentially a LOC IV and a H123, relatively easy to do.
Beware of "sparky" motors, some launch sites don't allow them.

 

[Buster]

Post office or UPS store and have them weigh it

I’ve done that. They were kinda surprised.

 

[Stargeezer]

Looks like my weight as it stands right now is 2 lbs. 10.9 oz.

That's without the motor, the 10# swivel I'm waiting on, insulation, shock cord protector and Nomex blanket I'm also waiting on.

I'm trying to learn what it means to set my delay (how I determine what delay is needed) and how to set the ejection charge? Those concepts are foreign to me and I want to learn them. ThurstCurve is too simple of a program, OR is too glitchy on my computer, and I cannot afford RockSim right now so....are there any other free programs out there I might be unaware of?

 

[tsmith1315]

OR is too glitchy on my computer,

Ask for help on OR here, and you’ll get expert assistance:

https://www.rocketryforum.com/forums/rocketry-electronics-software.36/

 

[mcderek]

Looks like my weight as it stands right now is 2 lbs. 10.9 oz.

That's without the motor, the 10# swivel I'm waiting on, insulation, shock cord protector and Nomex blanket I'm also waiting on.

I'm trying to learn what it means to set my delay (how I determine what delay is needed) and how to set the ejection charge? Those concepts are foreign to me and I want to learn them. ThurstCurve is too simple of a program, OR is too glitchy on my computer, and I cannot afford RockSim right now so....are there any other free programs out there I might be unaware of?

Hi Jess, I can show you how it works. It isn't difficult but trying to figure it out from printed instructions is a bit challenging. At least it was for me.

 

[cbrarick]

thanks for volunteering to help him, mcderek.

You know what they say about teaching a man to fish......

besides, it's his cert not ours! I think sometimes these things turn into a group project.......but by teaching him how to use one, he'll be set for his rocketry career, or at least until he needs to do a class 3 submission :>

 

[Buckeye]

Those concepts are foreign to me and I want to learn them. ThurstCurve is too simple of a program,

Too simple? If these concepts are foreign to you, how can you judge?

Simple is what you need right now. Thrustcurve has simple input, but the output is accurate and thorough. And awesome. Read the documentation.

In a mere 2 minutes, I tested your rocket with every Aerotech and CTI H motor in 29, 38, and 54 mm. Attached .csv has the output with all the info you need. Pick a good one.

 

[Stargeezer]

I spoke with the Apogee folks who suggested I try the H195NT and drill it down to a 10 second delay. Anyone have any experience with this particular motor?

 

[Stargeezer]

Too simple? If these concepts are foreign to you, how can you judge?

Simple is what you need right now. Thrustcurve has simple input, but the output is accurate and thorough. And awesome. Read the documentation.

In a mere 2 minutes, I tested your rocket with every Aerotech and CTI H motor in 29, 38, and 54 mm. Attached .csv has the output with all the info you need. Pick a good one.

View attachment 627206

Ok fair...lol.

 

[Jeff Curtis]

I did my L1 today with an H115DM. My rocket weighed 33 ounces and hit 1589'. Apogee has a good film on how to drill delays with the Universal too.

 

[bad_idea]

I did my L1 today with an H115DM.

Congratulations!

 

[Jeff Curtis]

Congratulations!

Thanks. It's quite a relief once its done.

 

[Wrightme43]

I had to go and find the link for @Art Upton 's rocket--found it on his youtube channel: Fins waving bye-bye I don't think you're going to find a better video of fin flutter leading to structural failure.

But, back to the thread. I often forget to use Thrustcurve.org as I gravitate towards OR, but I've used it a couple times. It's much faster than OR for commercially available rockets that are already in the database. Bottom line, there are some great simulation aids out there. Plug in some criteria, go pick a motor and fly it.

Thanks for linking that. Now there is something else to worry about.

 

[kjhambrick]

I did my L1 today with an H115DM. My rocket weighed 33 ounces and hit 1589'. Apogee has a good film on how to drill delays with the Universal too.

Congratulations @Jeff Curtis !

I've watched that Apogee Video ... Do you have any pictures or videos of YOUR flight ?

Thanks !

-- kjh( I like to watch TV -- C. Gardner )

"Being There" -- I like to watch TV ...

 

[2-0turbo]

Thanks for linking that. Now there is something else to worry about.

I wouldn’t worry about it. Think of it as a challenge to overcome! I am purposely fabricating some “disposable” rockets now to test the shred limit. Consequences if it turns to confetti are pretty low.

 

[Jeff Curtis]

Congratulations @Jeff Curtis !

I've watched that Apogee Video ... Do you have any pictures or videos of YOUR flight ?

Thanks !

-- kjh( I like to watch TV -- C. Gardner )

"Being There" -- I like to watch TV ...

 

[kjhambrick]

Beautiful Exhaust trail on that H115DM @Jeff Curtis !

Thanks for the picture and congrats again !

-- kjh

 

[Ron Soto]

Nice @dmaaero !

There are actually two models under one page for $19.99 ( CEN-TECH model 95364 and CEN-TECH Model 61641) at Harbor Freight - CEN-TECH Digital Scale

I can't determine the diffs from their web page but I need a new scale with a little more capacity so I am going to go take a look next time I am in Georgetown !

Thanks !

-- kjh

check amazon. they've got digital scales for less then 20 bucks.

r-

 

[kjhambrick]

check amazon. they've got digital scales for less then 20 bucks.

r-

Thanks Ron

One thing I like about local B&M Stores is I can inspect or even try what I am buying.

And the people at Harbor Freight in Georgetown know me so they don't mind if I carefully open a box to take a look.

Anyhow ... still lookiing ... the CEN-TECH scales were OK but not great so I'll make do with my old 1Kg scale until I find one better.

-- kjh