Eggtimer as a two stage avionics package

[gdjsky01]

I am reading the eggtimer classic manual, and I am starting my FIRST EVER two stage MPR/HPR project, a LOC Terrier to LOC Sandhawk.
Is the Classic well suited to this?
I appears 'all' I have to do is enable channel B and set the time I think the booster will burn, and a delay after that before CH B will fire. The extra delay being long enough to let the drag separation happen, but not too long lest the sustainer heal over.

This SEEMS to be mode 6 of the classic? I know mode 4 is using a breakwire AND the burn time of the booster. But I am not sure of the difference from mode 5 and mode 6.

So I guess I am simply askin' has anyone out there used an Eggtimer Classic (v1.5x) to control a two stage rocket? The booster will be motor eject with a JLCR for the chute at 300'

The sustainer would be ignited by the Eggtimer classic's channel B AND the 'A' channel would deploy the laundry with yet another JLCR for the 300' deployment

No?

 

[rharshberger]

I am reading the eggtimer classic manual, and I am starting my FIRST EVER two stage MPR/HPR project, a LOC Terrier to LOC Sandhawk.
Is the Classic well suited to this?
I appears 'all' I have to do is enable channel B and set the time I think the booster will burn, and a delay after that before CH B will fire. The extra delay being long enough to let the drag separation happen, but not too long lest the sustainer heal over.

This SEEMS to be mode 6 of the classic? I know mode 4 is using a breakwire AND the burn time of the booster. But I am not sure of the difference from mode 5 and mode 6.

So I guess I am simply askin' has anyone out there used an Eggtimer Classic (v1.5x) to control a two stage rocket? The booster will be motor eject with a JLCR for the chute at 300'

The sustainer would be ignited by the Eggtimer classic's channel B AND the 'A' channel would deploy the laundry with yet another JLCR for the 300' deployment

No?

I would highly recommend a Quantum or Proton for staging if using Eggtimer stuff, both have safety lockouts to prevent upper stage ignition unless certain conditions are met.

 

[waltr]

Just did a quick read of the eggtimer Classic's manual. Looks like this will do what you want but I don't know enough about it's modes and programming.
It seems to have a 100fps min velocity lockout with is good.

I have been using an Eggtimer Quantum for a simple air-start rocket. So far it has worked fine.

A few notes:
1- Drag separation very RARELY occurs (read through the threads in the Cluster/air start forum section). So plan on active separation. This can be a separation charge fired by electronics or simply 2-nd stage motor ignition forcing separation. I use 2nd stage motor ignition and this has worked very well and no damage to ISC.

2- My 2nd stage motors have been AT Blue thunder since they claim to ignite easier but have found they take 1-2 second to come up to pressure. (I run a full 10DOF instrument for post flight analysis). I make ignites with 40ga nichrome and Pro-cast (from Quick Burst) which a 2S LiPO and the Quamtum lights easily.
CTI motors use an ematch and a pellet in the motor and a lot of people use these for 2nd stage due to easy and quick motor ignition.

On one flight the 2nd stage motor took over 4 sec to light and the rocket had slowed and was nosing over when motor finally come up to pressure. It then power downward through a tree (lucky away from flight line). Nothing in any air-start setup could prevent this since all conditions were good when the igniter was fired.
This was with a booster motor with marginal thrust for rocket. Next flight used a higher impulse booster. Cris at Eggtimer recommends a booster with a 10:1 TTW.

Down load and read the Quantum Air-start guide. Cris has a lot of good info there that is not in the Classic manual.

3- Simulate and TEST, TEST, TEST.
Ensure to motor igniter will work with the Classic and battery.

Set up the Classic for air start and install xmass tree light bulbs instead of igniter. Place in a vacuum chamber (I use a jar with a pin-hole in the lid. then put a vacuum cleaner onto the lid to draw the vacuum). Draw vacuum and you should see to motor bulb light. back off the vacuum and the apogee bulb should light.
Download the data and examine it to ensure all events happens as you want them. You may need to adjust settings and rerun.

There are a lot more things to go wrong but it is great when it all works.
Do read both the Quantum and Proton manuals and consider these as well.

 

[Jmhepworth]

I’ve used EggTimer altimeters successfully in a two stage rocket—a Quantum in the interstage coupler for a separation charge and recovery of the booster (single deploy) and a Proton on top for firing and recovery of the sustainer (dual deploy). I use Aerotech blue thunder in the sustainer but add a pellet of Pyrodex at the top of the motor when I build it. Then I light it with an MJG Firewire initiator. I also add a second Quantum to the sustainer and use motor ejection in the booster for redundancy.

 

[cerving]

Our choice in order of preference for staging would be Proton, Quantum, then Classic. The Proton has a 120G accelerometer which makes sensing motor burnout very accurate. It's easy to set your second stage to fire when the first stage burns out. It also has enough outputs to handle a separation charge, motor ignition, drogue, and main chutes, with a couple of channels left over. The Quantum has two outputs, it basically works as a staging timer with qualifications for altitude@time and velocity@time. It can handle two events in airstart mode: separation charge and motor ignition, or separation/motor ignition and drogue; the latter is often used in booster stages. The Classic's single airstart output is similar in function to the Quantum, but the Quantum (and Proton) have WiFi switches built into the deployment power, so the outputs are basically "off" until you arm them remotely AND launch-detect occurs. We believe that arming an airstart remotely is much safer than doing it with your face a few inches away from a "live" motor while fiddling around with a screw switch or a magnet...