[johanngr]

johanngr

johanngr

Visit johanngr's website.

Show johanngr's last posts.

Show general stats for johanngr.

• 
• Administrator
• Model Rocketeer
• Posts: 61

Hi Guys!

I'm busy with a 2-stage rocket for the 17th.  So far I have the airframe, recovery and motors sorted.  It will be 68mm OD on both stages.  Staging from a Full_J to an 51mm I.  This is for starters.  I designed it to take a full_J to full_J.

For the second stage ignition I'm using a simple mercury switch in series with a battery, on/off switch and the igniter.  On 1st stage burn-out the mercury sw will start the 2nd stage motor.  I was considering putting the circuit into the 2nd stage to ensure the motor starts even if the stages separates too early.  The problem is the wiring to the motor.  The easier option is the one I'm doing.  Put the air-start-circuit in the booster and prevent drag separation by keeping the booster's drag to a minimum.  If they still drag-separate, the 2nd stage won't start but still land safely.

I'm planning to use an Altimeter in the 1st and 2nd stages.  This will make sure the booster ejects it's chute on-time without any guesswork.

The sustainer will be a near standard StarChaser2.  The fins will be smaller and the motor retention is different, but that's all.

The Rocket's name is not fixed yet but I like Sparkplug.  What do you think?

[Ryno]

Ryno

Ryno

Visit Ryno's website.

Show Ryno's last posts.

Show general stats for Ryno.

• 
• Administrator
• High Power Rocketeer
• Posts: 164

Aha ! This will be interesting!

How did that carbon fibre 2 stage rocket switch between motors?

[johanngr]

johanngr

johanngr

Visit johanngr's website.

Show johanngr's last posts.

Show general stats for johanngr.

• 
• Administrator
• Model Rocketeer
• Posts: 61

According to the owner, Freddie, he used a timer first and on the second try a mercury switch.  On the second try the 2nd stage started but wasn't pointing in a good direction when the motor started.

I hope mine will be on a near vertical trajectory at 2nd stage ignition.

As I always say, there is only one way to know.

I hope I see you all at the launch on Saturday.

[Thruster]

Thruster

Thruster

Show Thruster's last posts.

Show general stats for Thruster.

• 
• Water Bottle Rocketeer
• Posts: 48

I  like to know how do he manage to hold the igniter in place on the top grain?
something like a toothpic or just leave it like it is.

[johanngr]

johanngr

johanngr

Visit johanngr's website.

Show johanngr's last posts.

Show general stats for johanngr.

• 
• Administrator
• Model Rocketeer
• Posts: 61

Two-stage rockets have always had a problem with starting the 2nd stage.  Some use the toothpick method to hold the igniter in place.  My idea is to glue the igniter to the top grain segment.

We'll see on Saturday!

I have attached a picture I took recently.  You'll notice it was taken before it was painted and that the 2nd stage payload section is a loose fit on the 2nd stage booster section.

What do you think?  Will it fly?  I am planning to try a 51mm Hot-I to a 51mm Long burn Full_J and then maybe a Full_J to Full_J.  We'll see how the weather looks!

See you there!