New to HPR

[SkyFire]

New to this site too. A lot of good information!

Flew Estes rockets as a kid in the 60's and 70's. Launched a mouse once. He survived but was quite dizzy!

Got a 4" Madcow Black Brant II for my first high power rocket.

 

[o1d_dude]

Welcome back to rocketry.

Can’t help but notice that have some nice toys in your garage. Most of us do.

 

[mo2872]

Welcome!

Way too tidy of a shop/garage, though......

 

[Louis Wu]

I think the rules have changed since the early days. Mice are no longer allowed as passengers..

 

[SkyFire]

I think the rules have changed since the early days. Mice are no longer allowed as passengers..

Yeah, the ASPCA probably frowns on that too.

 

[David Schwantz]

I spy a P-47 in the background.

 

[samb]

Welcome back to the party ! Seriously, how do you decide which ones to play with ???

 

[crossfire]

Welcome to HPR. Be safe and have fun.

 

[SkyFire]

I spy a P-47 in the background.

Yep, there's a couple more too!

 

[Nathan]

Welcome. I also got my start in rocketry launching mice in the 60's. The rocket ride didn't hurt them but after that they became snake food for my pet boa constrictor.

 

[David Schwantz]

Very nice. Do you get out to fly them much?

 

[SkyFire]

Very nice. Do you get out to fly them much?

Quite a bit! I live in Tucson, AZ. The weather here is 'severe clear' most of the year!

 

[David Schwantz]

Lucky you.
Ours is severe snow.

 

[Joekeyo]

Looks like I am resurrecting an old thread. No doubt a reoccurring theme.

I , too am new to HPR and I have questions. Big surprise, right.
The instructions call for a 1/8" vent hole in the "chute compartment". Ok. Is one place better than another or does it really make no difference ? I was thinking of putting it up near the NC just below the shoulder.

Someone said their rookie mistake was anchoring the shock cord to a motor mount with any eyebolt. What? I thought this was state of the art and would expect it to be strong. I would consider coating both sides of the 1/4" ply centering ring with white glue to add strength, if necessary???

Is there a better way to anchor the shock cord?

Engine retainer. Where can I get a Z retainer about which I read? I assume this is a bent piece of metal that holds the motor using a screw. Is this so? I was thinking using a threaded rod and a wing nut. Has anyone done this? If so what's the pros and cons?

 

[Joekeyo]

Sorry. 4" Madcow Little John

 

[David Schwantz]

Z retainer = LOC Precision for one. Eyebolt in a MMT CR is fine. Can also glue to MMT tube through a CR.
Threaded rod and wing nut would work. Also just a bolt with washer going into a blind will hold motor in place. Vent hole placement any where is ok, just do not put it where chute may plug the hole. I would do larger than 1/8" myself. I also like to align holes with fins. Makes for a clean install and also makes them easier to find.

 

[T-Rex]

When I built my Little John, I used the supplied eyebolt. I added a washer to the back side of the centering ring for extra strength. If the parachute deploys at high speed, it could pull the bend out of a conventional bent eye bolt. Many people say not to use them for that reason. Instead it is recommended to weld the eye shut or use a forged eye. Some of my rocket have bent eyes, some do not. Your rocket, your choice.
As was mentioned, some will epoxy the shock cord to the side of the motor tube, then feed it through a notch or hole in the upper centering ring. Many ways to do it. None are necessarily more right than others.

The purpose of the hole is to vent pressure from inside the tube as the rocket ascends. The parachute and protection will slide back toward the motor mount so could easily cover the hole in flight if it is down in that region.

Z type retainers are just pieces of bent into a square z shape. You can find them at hardware stores or on line sold as mirror or picture clips. this link gives an idea of what I am talking about: https://www.amazon.com/OOK-50228-4-...ocphy=9018800&hvtargid=pla-343219994314&psc=1
As mentioned, a screw or bolt works, so does a couple wraps of tape for friction fit..... There are many styles of motor retainers in many different prices. (but you asked specifically about z-clips)

Enjoy!

 

[Joekeyo]

These are great answers. Thank you for your consideration. It looks like it cleared up my suspicion about the z engine retainer often being of the homebrew variety. Tape alone sounds scary, twist ties were recommended by the motor seller for mid-power 24mm reloads.

I got a little overexuburant with the epoxy, so the screw eye is now a permanent fixture. ☹. At least it is oriented in the right direction. I was able to add a washer to the bottom, a lock washer. Cheap insurance. I don't think the bolt is going anywhere. Can the eye open? Let's hope not. Thanks again.

 

[tsmith1315]

I got a little overexuburant with the epoxy, so the screw eye is now a permanent fixture...

... I don't think the bolt is going anywhere.

A screw eye threads directly into the centering ring, like a self-tapping screw. When boatgeek mentioned screw eyes on page 1 of the "Rookie HPR mistakes", this is what he probably meant, because LPR and MPR often use screw eyes. It would be an easy mistake to continue with them in larger rockets.


An eye bolt passes through a hole and secures with a nut on the backside. IME, that works fine for the average 3" - 4" cardboard kit on a nominal flight.

 

[Joekeyo]

A subtle but important difference. Mine has a bolt ☺