Apogee "Simple Timer" ? Unexpected Results???

[gary7]

Just happened across this Apogee video about their simple timer. Interesting.

youtube.com/watch?v=n12e9dXkajA&t=15s

 

[sed6]

I think that is a great unintentional demo video! I've been looking into building my first two stage and this is definitely the way I will go to control it. The built in tilt sensor is a fantastic safety feature! Preventing both second stage ignition and deploying a parachute; who else does that?

 

[kjhambrick]

@gary7 and @sed6 --

I don't mean to take anything away from TVM and Apogee and the Simple Timer but there are a few full featured Flight Computers that do that and a lot more.

For example, this one: Featherweight Altimeters: Blue Raven Altimeter

It does cost just a little more but it does a lot more than fire squibs at Time = t and at Apogee based on the Tilt Angle ...

Check it out !

There are a lot of posts here, including beautiful graphs of flights if you like that sort of stuff.

HTH

-- kjh

 

[SolarYellow]

Eggtimer Proton is another that seems to be good. I have the new version in my build pile. However, due to packaging in various projects, I expect to eventually end up with both the standard Blue Raven and the circular one. So I'm not partial to either company.

 

[Buckeye]

@gary7 and @sed6 --

I don't mean to take anything away from TVM and Apogee and the Simple Timer but there are a few full featured Flight Computers that do that and a lot more.

Well, it is the "Simple Timer" after all.

 

[mtnmanak]

I am usually of the opinion that most products on Apogee are overpriced (they have a great selection and provide a lot of info, so not complaining about it - just noting that I can usually find similar products cheaper elsewhere), but a simple timer with an airstart channel, a deployment channel and tilt monitoring, that can also handle 16V, is actually not a bad deal for $100. The Altus Metrum Easy Timer is cheaper, but it doesn't include a real deployment channel.

If there is one feature I would love to see in a Proton like product from Eggtimer, it is tilt monitoring. It would make the Proton a complete airstart solution.

 

[cerving]

I view tilt lockout (and other lockout mechanisms such as altitude@time) as secondary safeties. The #1 requirement for airstarts is that your rocket must be stable to begin with, in any possible configuration that you're gonna fly. Have you ever seen an Estes two-stager, with no lockouts at all, skywrite? (Not counting fins shredding off...) Nope... that's because they are designed to be stable. Secondary mechanisms prevent bad things from happening when something doesn't go right... they're not a way to make it "easier" to do airstarts by letting your electronics take care of the messes. If you build your rocket well, do a good simulation prior to your flight, and set up your electronics accordingly (which you should be doing anyway), there isn't much difference between using tilt lockout or altitude lockout.

This assumes that you're the average rocketry hobbyist and not going crazy high... at 100K+, everything is different, including instability remediation. If you start tumbling at 100K, your electronics aren't going to save your butt there, either.

 

[mikec]

A friend of mine got one of these, and I was surprised to see that it has no audible way to tell if it's armed or not. This seems like a serious safety issue. It has a couple of LEDs, but with an internal mount it's not practical to see them.

Also, they claim that you can't change the 45-degree angle because of processor limitations -- "The only way to get some arbitrary tilt angle setting would be to use sins and cosines. Our inexpensive little processor on the device can’t do that kind of math as fast as it would need to for rockets! So instead we just do a compare." Makes me wonder how they are doing the orientation calculations in the first place, and if they are doing them correctly.