F Motor Storage & Prformance

[VinceC]

Good Morning,

The ARC Team I mentor primarily uses Aerotech F size motors. Over the last two to three years they have accumulated a small inventory of unused motors.

Some of these unused motors could be between two to three years old and probably have seen temperatures between 30° and 90° F. The motors were probably stored stored most of the time in a conditioned space around 60°F but may have spent a winter in a unheated space where the outside temperatures could have dropped below 30°F. The motors were pretty protected while traveling but mostly lived in tackle boxes so they were banged around a bit. Humidity would have been fairly low.

The question is, does the age and the past storage practices of these motors effect their performance? Can the Team depend on these motors performing "just as good" as new motors they would buy this year?

The team does weigh each motor "to do something" before each launch but other than that do not know of any way to check for reliability or pre-launch performance.

Thank you in advance for your time, thoughts, and comments.

Vince
Onteora Rocket Club

 

[Antares JS]

Good Morning,

The ARC Team I mentor primarily uses Aerotech F size motors. Over the last two to three years they have accumulated a small inventory of unused motors.

Some of these unused motors could be between two to three years old and probably have seen temperatures between 30° and 90° F. The motors were probably stored stored most of the time in a conditioned space around 60°F but may have spent a winter in a unheated space where the outside temperatures could have dropped below 30°F. The motors were pretty protected while traveling but mostly lived in tackle boxes so they were banged around a bit. Humidity would have been fairly low.

The question is, does the age and the past storage practices of these motors effect their performance? Can the Team depend on these motors performing "just as good" as new motors they would buy this year?

The team does weigh each motor "to do something" before each launch but other than that do not know of any way to check for reliability or pre-launch performance.

Thank you in advance for your time, thoughts, and comments.

Vince
Onteora Rocket Club

Send 'em. They are most likely fine.

 

[techrat]

Considering that there are folks here on the forum who launch 20 year old motors, I would hazard a guess you're OK. Remember that before they were purchased, they may have sat in a warehouse for 6 months or more. These things do have a shelf-life, but it's definitely more than just a few years.

 

[Ronz Rocketz]

Look into the nozzle with a flashlight and see if there is any white residue blocking the opening. I doubt this is the case with a couple year old motors. What you can do (as recommended to my by AT) is to use a straightened paper clip and gently scrape the insides to ensure the propellent is exposed. This is what I do after a chuff to clear out the channel.

Lately, the chuffing has gotten to be a frequent problem here in humid Hawaii. For the MPR motors, I insert an inch of cannon fuse into the rocket to give it extra bite. This was not mentioned by AT, but seems to work... no more chuffing off the rod. Not sure if this is allowed in tARC...

I recently bought a pack of 20 Firewire Electric Matches. Haven't tried them yet. Time to experiment...

 

[Art Upton]

Cannon Fuse would not be allowed at ARC [used to be TARC] , but following the rest of the advice they should not have any problems.

 

[dpower]

Black powder motors would certainly not be ok with storage like this, because they rely on the bond between the propellant and paper case to hold it in place during combustion. Single-Use AP motors, are much more tolerant of temperature cycling, since sealing is done by O-rings and/or epoxy.

 

[smstachwick]

Good Morning,

The ARC Team I mentor primarily uses Aerotech F size motors. Over the last two to three years they have accumulated a small inventory of unused motors.

Some of these unused motors could be between two to three years old and probably have seen temperatures between 30° and 90° F. The motors were probably stored stored most of the time in a conditioned space around 60°F but may have spent a winter in a unheated space where the outside temperatures could have dropped below 30°F. The motors were pretty protected while traveling but mostly lived in tackle boxes so they were banged around a bit. Humidity would have been fairly low.

The question is, does the age and the past storage practices of these motors effect their performance? Can the Team depend on these motors performing "just as good" as new motors they would buy this year?

The team does weigh each motor "to do something" before each launch but other than that do not know of any way to check for reliability or pre-launch performance.

Thank you in advance for your time, thoughts, and comments.

Vince
Onteora Rocket Club

Some propellants have idiosyncrasies but they should be fine. White Lightning in particular might benefit from being scraped, as some variants oxidize. It’s also possible for grains to swell and close up the igniter channel, but if you can get the igniter to the delay element it’s probably OK.

 

[Ronz Rocketz]

Black powder motors would certainly not be ok with storage like this, because they rely on the bond between the propellant and paper case to hold it in place during combustion. Single-Use AP motors, are much more tolerant of temperature cycling, since sealing is done by O-rings and/or epoxy.

Yes and no. BP motors exposed to the elements tend to de-bond. The Composite motors have more propellent exposed and more likely to sweat leading to possible chuffing.

I had a bunch of AT motors given to me that were exposed for many years. I used a drill bit to lightly core out the channels and remove the residue that was blocking the opening. It mostly worked...

 

[smstachwick]

Yes and no. BP motors exposed to the elements tend to de-bond. The Composite motors have more propellent exposed and more likely to sweat leading to possible chuffing.

I had a bunch of AT motors given to me that were exposed for many years. I used a drill bit to lightly core out the channels and remove the residue that was blocking the opening. It mostly worked...

Back in November I bought an old F25W motor off @fyrwrxz , with a manufacturing date that is probably longer ago than he’d like me to mention here, and he went at it to fix a grain that had swollen completely shut. It chuffed and flamed gently for about a good 5 seconds before igniting in earnest. I’m pretty sure the delay burned for longer than the nominal 9 seconds too, but it worked.

I wouldn’t be using anything like that for an ARC flight though.