Timer Options?

The Rocketry Forum

Help Support The Rocketry Forum:

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
I'm looking to try my hand at air starting and two stage. My early luck with a/v bays has me making second guesses.

I've heard of timers that detect off attitude and prevent starting the second motor. As long as you get above your main deployment altitude, it recovers fine.

So what timers out there will do this?
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
TRF Supporter
Joined
Feb 3, 2012
Messages
4,254
Reaction score
1,567
The upcoming update to the Eggtimer Quantum (due in about a month) adds timed airstart capabilities with velocity, altitude, and breakwire checks. It's also WiFi enabled (i.e. you arm/disarm it remotely with your phone/tablet and a browser), you can use separate batteries for the altimeter and the deployment igniters if you wish, and it records your flight profile which can be read back to your wireless device and/or downloaded to a laptop or tablet for analysis. $40. The catch is that it's a kit, like all Eggtimer Rocketry products... you have to solder it together. See www.eggtimerrocketry.com for more details.
 

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
But if the rocket rolls over 90° before ignition of the second motor (let's say I set the timer too long), will it stop the count and not ignite the second motor?
 

ttabbal

Well-Known Member
Joined
Jan 19, 2009
Messages
1,082
Reaction score
22
None of the timers can detect the rocket going sideways. Detection of altitude could help a lot. I would like to have one that I could also use an R/C setup with as a kill switch. If I see the rocket doing something bad, let go. That would signal the staging electronics to disarm. Then the deployment altimeter would fire at apogee for the recovery system.

The R/C system wouldn't work for really high altitude flights, you have to see it, and radio range is limited. But for lower stage altitudes, it's a cheap easy way to deal with the problem.

I have built a Quantum, quite a fun project and I plan to build more. Particularly with the stage control feature coming. cerving: is the current plan for a software update or does it require revised hardware?
 

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
None of the timers can detect the rocket going sideways. Detection of altitude could help a lot. I would like to have one that I could also use an R/C setup with as a kill switch. If I see the rocket doing something bad, let go. That would signal the staging electronics to disarm. Then the deployment altimeter would fire at apogee for the recovery system.
Let me check on that. My club president said he found one that does detect if it's off attitude and turns off. I'll have to ask him what it was. I figured it there's one then there must be more. Maybe there's only one. Maybe he read it wrong.
 

timbucktoo

Well-Known Member
Staff member
TRF Supporter
Global Mod
Joined
Jun 13, 2014
Messages
8,187
Reaction score
1,320
Location
Cocoa Beach
I use a timer ONLY for ISC separation and deployment of booster main. RRC3 in sustainer for air start.
 

ttabbal

Well-Known Member
Joined
Jan 19, 2009
Messages
1,082
Reaction score
22
Let me check on that. My club president said he found one that does detect if it's off attitude and turns off. I'll have to ask him what it was. I figured it there's one then there must be more. Maybe there's only one. Maybe he read it wrong.
There was a device that could do it. It was called rocket tilt-o-meter or something like that. It's no longer made, due to a required part going out of production.

The currently available units like the Raven and RRC3 let you set altitude, velocity, or other limits. But they don't measure the tilt directly. Honestly, that's probably good enough. Using sims and test flights you can get a good idea of what the minimums should be. If the first stage is off-axis, you will get less altitude.
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
TRF Supporter
Joined
Feb 3, 2012
Messages
4,254
Reaction score
1,567
Off-axis flights are generally the result of either instability or too little velocity which leads to weathercocking. Both of those can be prevented with a good simulation, which you should be doing anyway with such a complex project. An altitude@time or velocity@time check can prevent firing due to either one of those; that's what the RRC3+, the Raven, and the Eggtimer (and soon the Quantum) use. The only production device that I know of with an IMU to do a direct off-axis check is the TeleMega, a very nice device but rather expensive for most hobbyists.
 
Last edited:

rharshberger

Well-Known Member
Joined
Oct 13, 2014
Messages
9,831
Reaction score
1,801
Location
Pasco, WA
The Missleworks PET2+ according to the website offers Off-Axis detection up to +/- 20 degrees, it does not have a altitude detection though iirc. I own one but have not had a chance to use it yet.
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,094
Reaction score
369
Location
Central Illinois
The upcoming update to the Eggtimer Quantum (due in about a month) adds timed airstart capabilities with velocity, altitude, and breakwire checks. It's also WiFi enabled (i.e. you arm/disarm it remotely with your phone/tablet and a browser), you can use separate batteries for the altimeter and the deployment igniters if you wish, and it records your flight profile which can be read back to your wireless device and/or downloaded to a laptop or tablet for analysis. $40. The catch is that it's a kit, like all Eggtimer Rocketry products... you have to solder it together. See www.eggtimerrocketry.com for more details.
I presume if the re-designed Quantum remains a two channel device, it will be applicable as a dual deployment altimeter or an airstart/staging deployment device
through programming?

That distinction should be clear because if one is interested in a smaller project that say needs an all-in-one device to do it all, it takes more than two channels
to perform that task. If the "new" Quantum is an either/or proposition then that would mean one would be stationed in the booster to light the sustainer and
then deploy the recovery chute for the booster. The sustainer would need it's own deployment device in that case. Kurt
 
Last edited:

MWC

Well-Known Member
Joined
Jan 4, 2012
Messages
672
Reaction score
33
For the record here, the off-axis check of the PET2+ is performed statically on the pad after booting the timer, not during flight. There are other options one can employ to further enhance non-spoofing the timer and increase your safety margin... these options include inertial integration timing and inertial thresholds, both of which can be combined with a break-wire permissive to establish a timer trigger.
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
TRF Supporter
Joined
Feb 3, 2012
Messages
4,254
Reaction score
1,567
I presume if the re-designed Quantum remains a two channel device, it will be applicable as a dual deployment altimeter or an airstart/staging deployment device
through programming?

That distinction should be clear because if one is interested in a smaller project that say needs an all-in-one device to do it all, it takes more than two channels
to perform that task. If the "new" Quantum is an either/or proposition then that would mean one would be stationed in the booster to light the sustainer and
then deploy the recovery chute for the booster. The sustainer would need it's own deployment device in that case. Kurt
Yes, there's an option to make it either a standard deployment controller or an airstart controller. In airstart mode, you can also use the drogue channel to fire like a real drogue, i.e. at apogee, for either the chute in the booster or the drogue in the sustainer.
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,094
Reaction score
369
Location
Central Illinois
Yes, there's an option to make it either a standard deployment controller or an airstart controller. In airstart mode, you can also use the drogue channel to fire like a real drogue, i.e. at apogee, for either the chute in the booster or the drogue in the sustainer.
That adds great utility to the unit. Congratulations. Folks with smaller two stage projects would likely still have to consider a small "Raven-like" multi-channel all-in-one unit. The key is simulating the heck out of a project to avoid what happened at MWP a few years back. A small obviously two stage, timer actuated project got up a bit on the booster (not very high mind you), did a few loops and then the sustainer fired at 20 to 30 degrees above the horizon. Fortunately, it went away from the crowd.

I'm sure the folks out west in the wide open spaces aren't "as concerned" but some sites that are more constrained are getting leary of two stage APCP projects. If I was really "into" that sort of thing, I'd likely bring video on a hand held device to show
the RSO that my project had flown before and was successful. Yeah, there's always a first time but perhaps that's best had at a less sparsely attended club launch.

Oh, I think the smallest multi channel controller was the precursor to the Raven the Parrot. (Anyone know of anything smaller?) It had three channels and is programmable. I had one that was lost in a crash. Landowner found it 4 days later but I didn't get it back for 18 months.

The buzzer was cracked and I simply replaced it and the onboard Lipo battery. Downloaded the ballistic flight and got a nice parabola. I keep intending to stick it in a beater rocket and try flying it again sometime but haven't got around to it.
I did hear that they could get out of calibration and weren't salvageable if that occurred. I don't know how one would tell.

One bad thing about the Parrot was if one had ematches on all three channels, if two were bad and one had continuity, it beeped one continuity message. One wouldn't be warned that the other matches/channels didn't have continuity.
That's what burned me. I was thinking MAWD while the rocket was on the pad, disconnected the apogee charge and then remembered the idiosyncrasy of the Parrot. I screwed the apogee ematch back into the terminal and missed one leg!
Main blew, cardboard main bay zippered, cord broke and the only thing I initially got back was a sliced plastic nosecone and the parachute that didn't look stressed at all.

Maybe it's good the Parrot went out of production. Kurt
 

BDB

Absent Minded Professor
Joined
Aug 22, 2015
Messages
2,196
Reaction score
432
Yes, there's an option to make it either a standard deployment controller or an airstart controller. In airstart mode, you can also use the drogue channel to fire like a real drogue, i.e. at apogee, for either the chute in the booster or the drogue in the sustainer.
This, plus a JLCR, is close enough for dual deploy for me. I'm planning to use two quantums for my initial HPR 2-stage attempts later this year.
 

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
Got with my club president. It was indeed the Telemega he found with the off attitude detection. He also referenced the PET2+ but was unaware that the off attitude was static at ground level.

So begins a new endeavor. I have an idea, just not sure how feasible it will be. A floating switch. Possibly a pendulum switch. It'll need some work, but it may be the answer for my concern. And may even have a place in the community.
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,094
Reaction score
369
Location
Central Illinois
Got with my club president. It was indeed the Telemega he found with the off attitude detection. He also referenced the PET2+ but was unaware that the off attitude was static at ground level.

So begins a new endeavor. I have an idea, just not sure how feasible it will be. A floating switch. Possibly a pendulum switch. It'll need some work, but it may be the answer for my concern. And may even have a place in the community.
Careful there. Sounds like a mercury switch situation which last I heard was a no-no. If you mean some sort of electronic detection (electronic gyros) etc.
and not an actual physical swinging pendulum you would be fine.

If one thinks about it, if it's set up like a physical "Tilt" switch in a pinball machine any little jitter could set off the safety inhibit
and the stack could still be at a safe attitude to fire the sustainer or next stage. In that case, your failure mode would be trusting the sustainer electronics to salvage the recovery. Something that happens a lot if the sustainer motor fails to ignite. At least the flier
gets a free do over in that case with a successful recovery of the pieces.

I'd be very leary of counting on a physical pendulum to account for anything in the dynamics of a rocket flight. Kurt
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,800
Reaction score
382
Location
Stafford, VA
Got with my club president. It was indeed the Telemega he found with the off attitude detection. He also referenced the PET2+ but was unaware that the off attitude was static at ground level.

So begins a new endeavor. I have an idea, just not sure how feasible it will be. A floating switch. Possibly a pendulum switch. It'll need some work, but it may be the answer for my concern. And may even have a place in the community.
Careful there. Sounds like a mercury switch situation which last I heard was a no-no. If you mean some sort of electronic detection (electronic gyros) etc.
and not an actual physical swinging pendulum you would be fine.

If one thinks about it, if it's set up like a physical "Tilt" switch in a pinball machine any little jitter could set off the safety inhibit
and the stack could still be at a safe attitude to fire the sustainer or next stage. In that case, your failure mode would be trusting the sustainer electronics to salvage the recovery. Something that happens a lot if the sustainer motor fails to ignite. At least the flier
gets a free do over in that case with a successful recovery of the pieces.

I'd be very leary of counting on a physical pendulum to account for anything in the dynamics of a rocket flight. Kurt
++++ what Kurt said.

You have to remember that mercury and pendulum switches won't work in flight like they do static on the ground. ref. Vomit Comet. When the rocket is slowing down after burnout it's at negative Gs and as it coasts over the top, everything inside is weightless with no up, down, or sideways. As Kurt said, some type of gyro is needed to determine direction under those conditions, not physical devices that depend on a constant pull of gravity to work right.
 

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
True. I admitted it would need consideration and research. To be honest, this might be a project to involve someone like missileworks, jolly logic, or stratologger.

Just imagine a simple, in line device that could prevent cruise missile staging. Automatically, by the sheer design, would work with any timer or staging device, regardless of manufacturer. It could be a game changer. And I can't imagine that production cost would be very high. Development cost not considered in that statement. It's probably several years out if I'm trying to design it alone.
 

FredA

Well-Known Member
Joined
Jan 19, 2009
Messages
2,185
Reaction score
357
Just imagine a simple, in line device that could prevent cruise missile staging. Automatically, by the sheer design, would work with any timer or staging device, regardless of manufacturer. It could be a game changer.

Sound like the Tilt-o-meter. A short lived product that was wired in between the control avionics and the motor igniter that inhibited ignition if the rocket was tilted too far. Wasn't exactly plug&play simple, but it worked. Use it on our 2-stage with an "N" moonburner so we don't end up in Idaho if it gets sideways.
 

Kruegon

Well-Known Member
Joined
May 21, 2014
Messages
1,885
Reaction score
4
I'm assuming the device is no longer available?
 

ksaves2

Lifetime Supporter
TRF Lifetime Supporter
Joined
Nov 25, 2009
Messages
6,094
Reaction score
369
Location
Central Illinois
I'm assuming the device is no longer available?
It went out of production when a component was no longer manufactured. It was not by the makers choice. In fact a small cache of the needed part was found later and
production resumed for a short time. When they were gone, that was it. The only option now is a Tele-Mega or Easy-Mega at $400.00 or $300.00 respectively. When one figures in the cost when used in a project like Fred describes above it's not
that much to have the peace of mind it brings. Fred, do you remember what the Tilt-o-meter cost? I thought it was $250.00ish? It wasn't the smallest thing either if I recall but I think they were used mainly on large
staged rockets so the size wasn't as much a factor because of the room available.
The Altus devices have 3axis magnetic detection AND 3axis 2000degree/second gyros. One programs the degrees off axis after which the channel is inhibited and done. It's the most reliable method to detect a launch gone
awry. I think someone asked a question about a totally unstable stack that is flying continuous loop the loops. I don't know if Keith or B'dale answered that extreme situation.
If the device locks out "permanently" once it goes off axis for enough for that flight, I guess one would be fine (as long as the errant boost doesn't skewer anyone and the sustainer is inhibited)
One pointed out what if the Mega removes the inhibit if it comes around on the loop to an acceptable position for a moment would it still fire?

Kurt
 

FredA

Well-Known Member
Joined
Jan 19, 2009
Messages
2,185
Reaction score
357
I seem to recall the Tilt-o-meter was $300....but it was a long time ago (>5 years) when I bought it.
Will probably fly it at Balls this year.
 
Top