Brief:
Here is a couple of new timers from Xavien, at www.xavien.com . The XSSRT-1, 'Xavien Single Stage Rocket Timer'. This is a 1 second to 63 seconds single event timer. I tested this one for future use in air starting. I also have the XDSRT-1, 'Xavien Duel Stage Rocket Timer'. This one is a 1 second to 63 seconds dual event timer. I used this timer wired in as back-up for altimeter ejection. They both come with an easy to read 7 page manual and a 1 year warranty. Their website at www.xavien.com has the manuals for these in pdf files. Bonus!

Specifications:

XSSRT-1 Single Timer

• Power Requirements 8-15 VDC
• PEAK Firing Current 2A @ 10sec.
• Dimensions 0.95" W x 2.5" L
• Nominal Battery Load 15mA
• Delay Settings 1 second to 63 seconds (in 1 sec. increments)
• Weight 14.2 grams

XDSRT-1 Duel Timer Specs

• Power Requirements 8-15 VDC
• PEAK Firing Current 2A @ 10sec.
• Dimensions 1.225" W x 3.8" L
• Nominal Battery Load 15mA
• Delay Settings 1 second to 63 seconds (in 1 sec. increments)
• Weight 21.4 grams

Setting the timer:

There are six DIP switches to set the delay timing. The dual event has two separate banks of switches. Here is a breakdown of the switch positions and their corresponding delay.

Switch # Adds:

1. 1 second
2. 2 seconds
3. 4 seconds
4. 8 seconds
5. 16 seconds
6. 32 seconds

Each DIP switch adds seconds to the total. For example: if you have switches 1, 2 and 3 on, you'll get a 7 second delay. It's actually very simple and easy to do. Just flip a switch to add time.

In Use:

I put them in my Prometheus; a 12 foot tall, 7.5" scratch built rocket with a central 54mm and four 38mm motor mounts. For this first flight, I used a K1050 in the center and air-started four Pro 38 J330's. I used the duel event timer as a backup for deployment. The rocket went somewhat horizontal just before the four motors lit. This threw off the calculations on when to deploy the chutes. When using a timer, you have to calculate the flight based on motor burn time and assuming a straight boost. If the rocket doesn't go straight, the events happen sooner than you calculate. Thus, the altimeter deployed the drogue and the main but the duel timer did light its ejection charges.

I used the single event timer to test its ability to light 4 Davyfire igniters. As I put the rocket together at the field, I decided not to use the timer to air-start the motors because the air-start system that was built into the rocket was mounted and wired much better. I also didn't want to put two igniters in each motor in fear of clogging the nozzles. I wired four igniters outside the rocket and tested its ability to light four of them. Although I didn't have them in the motors, it did light all four igniters.

Summary:

Limitations:

• There is no internal trigger to start the timers, like a G-switch. The timer is started by a physical break in an electrical contact. The example given is using a piece of solder that melts in the heat of the exhaust to start the timer. Because I have so much power in the Prometheus, I went with a wire tied to the pad being pulled apart at a point where I twisted them together. This worked well.
  
• Timers are just that: a timer. If the rocket doesn't fly as expected, the timing can be thrown off. This is no fault of this timer though; it is true with all timers.
  

Advantages:

• These things are pretty tough. They both survived an extremely violent flight, a 3 foot zipper and shredded drogue, when the drogue came out at high speed. They were also an 'afterthought', so the mounting was not planned during the build. Because of this, they were mounted and wired less than perfect and yet still performed perfectly.
  
• Setting the delay is easy. Unlike some other timers, the timing is digital, not set with a potentiometer. Thus, timing is exact.
  
• The single event timer lit four igniters, impressive.
  
• They both have a super-bright power indicating LED that was real easy to see in the full sun. A real nice added feature.
  
• Even the battery connecter is better quality that other ones. It's not the cheap flimsy type; it's a hard plastic heavy duty connector.

Overall Rating: 5 out of 5