What did you do rocket wise today?

[BrendanH69]

Sent a couple of emails to TRA and Aerotech to see if there is any actual measured temp data available for the external case temps as recorded during motor certification.

I've reviewed several recent motor certification test data sheets on the Tripoli website and I can only see a "pass" statement with regard to the NFPA 1125 section 7.4.1 external case temp requirements. As the "shall not exceed" requirements are either 200, 220 or 316 degrees C, n

"Common sense" says there should not be a problem here because many, many level 3 F/Glass motor mount tubes and MD airframes have been flown over the years with big, hot motors. So, we'd have heard all about it and if there was a problem then kits would have been redesigned if the case temps were cooking the epoxy resins out of the F/Glass matrix. Wouldn't we?

The reason I'd like to know more actual data is that I'm preparing a build plan to roll a composite material motor mount tube for an M class motor, using a commercially available Bio-Epoxy rather than the more traditional products like West Systems. To help me assess its safe use in this particular component, I'd like to understand the typical operating temperatures that the Bio-Epoxy composite MMT would need to be capable of sustaining, all while retaining its structural integrity.

Anyone got an insight into this topic?

 

[prfesser]

I would check the specs of the Bio-Epoxy against West's; softening temperature, maximum-use temperature, etc. If the Bio-Epoxy's temperature ratings aren't materially different from those of West or other commonly used epoxies, it ought to be okay.

 

[jqavins]

BTW, when I win Powerball, I will purchase a large property, not too far out of town. It will have a rocket launching area, a dirigible hangar for indoor free flight and MMX rockets. There will be a pond for RC sailing guys, There will be a weather resistant, solar charged RC sailplane winch always available. Also a solar charged golf cart for retrieval purposes for anyone with limited mobility. The dirigible hangar will be oriented perpendicular to the prevailing winds for slope soaring. Maybe I'll build my subterranean mad scientist's lair underneath. In that case, fire and blast resistant areas with good ventilation and at least two exits will be provided for those who want to make propellant, as well as appropriate magazines for such material.

Sounds great. Please tell me there will also be fully equipped shops, separated into separate rooms with separate HVAC systems, for dirty work (wood shop, machine shop, etc.) and clean work (electronics, kit assembly, etc.). Also with a half bath and a kitchenette.

 

[jqavins]

The reason I'd like to know more actual data is that I'm preparing a build plan to roll a composite material motor mount tube for an M class motor, using a commercially available Bio-Epoxy rather than the more traditional products like West Systems. To help me assess its safe use in this particular component, I'd like to understand the typical operating temperatures that the Bio-Epoxy composite MMT would need to be capable of sustaining, all while retaining its structural integrity.

Anyone got an insight into this topic?

I would check the specs of the Bio-Epoxy against West's; softening temperature, maximum-use temperature, etc. If the Bio-Epoxy's temperature ratings aren't materially different from those of West or other commonly used epoxies, it ought to be okay.

That, and this: try going by the maximum allowed temperature under 1125, 7.4.1; if the epoxy can stand that, then you don't need to know anything else. That's what requirements and specs are for.

 

[KenECoyote]

More stuff on my 6" X-15...
View attachment 1000017461.mp4




I thought I grabbed gloss black, but it was flat instead, but no biggie since this is just an initial coat before the maiden flight (hopefully this weekend).

 

[Joekeyo]

Reloaded 3 motors for Saturday's launch. F24, G64, and F51. I also have a H550 SU I plan on burning. Hope I can get in 4 launches.

 

[lr64]

I would check the specs of the Bio-Epoxy against West's; softening temperature, maximum-use temperature, etc. If the Bio-Epoxy's temperature ratings aren't materially different from those of West or other commonly used epoxies, it ought to be okay.

West isn't particularly good with heat. Even PVC pipe is better. There's a reason so many homebuilt composite airplanes are white. If I was going to the trouble of making a motor case, I'd want something good for a higher temperature.

from reliable and unreliable sources on the net:
West heat deflection temperature 48- 53C
PVC heat deflection temperature 54-80C
ProSet HDT room temp. cure 55 C
" " post cure up to 88 C
System 3000, after post cure 154 C, but that post cure has several temperatures, ending up at 149 C!
You can find systems that will go higher.

I try not to leave anything made with epoxy like West in a closed car on a sunny day. But something like West is probably fine for body tubes, etc. if you take that precaution an don't live in a really hot place.

Sounds great. Please tell me there will also be fully equipped shops, separated into separate rooms with separate HVAC systems, for dirty work (wood shop, machine shop, etc.) and clean work (electronics, kit assembly, etc.). Also with a half bath and a kitchenette.

Of course! That should go without saying.

 

[jqavins]

Of course! That should go without saying.

Well, maybe it should, but then I went and ruined it.

And I don't think he's making a motor case. The words were "motor tube", by which I believe he meant MMT.

 

[RokitFlyr]

In 20 or so years, I've never had a problem with West Systems and heat in a vehicle or sun. Temps here in central Wa. are often in the 100 degree range.

 

[cwbullet]

NICE

 

[Jeff Curtis]

Finished up a couple of rockets. The Estes Impulse is from the original Pro Series and a clone kit is available from Bad Boy Rocketry. It's a cluster with 2x24mm motors. I'll fly it on the 18th, weather allowing. The 2nd is the Estes Fox Fire. I love the looks of this one but retention is strictly friction fit.

 

[lr64]

In 20 or so years, I've never had a problem with West Systems and heat in a vehicle or sun. Temps here in central Wa. are often in the 100 degree range.

I once helped someone straighten out an epoxy/glass wing by strapping it to a door and leaving it in a car on a sunny day. It worked. I've also had a foam wing that was merely inside of a translucent bag have a melt down*. Not sure how much of that was the foam, and how much the epoxy.

*Maybe "sag down" would be more accurate.

 

[Antares JS]

Started on an Estes Patriot.

Sometimes a simple 4FNC LPR is like a relaxing palate cleanser.

 

[lr64]

That, and this: try going by the maximum allowed temperature under 1125, 7.4.1; if the epoxy can stand that, then you don't need to know anything else. That's what requirements and specs are for.

I looked that up. 200° C for motors under 160 n-s, 220 for above. Except for single use motors above 80 n-s, when it's 316. In other words, much higher than most epoxies are rated for.

 

[Tobor]

Almost finished designing my future EggFinder "Base Station".

(Click images to enlarge)


Base station features:
2x EggFinder LCD Rx boards: One for GPS tracking, the other for rocket telemetry
1x EggFinder LCD-GPS module (For GPS board)
1x LCD Module (For GPS board)
1x EggTimer Voice Module
1x EggFinder BT module (for cell phone connectivity)
1x AdaFruit 2.5W mono amp.
1x Pololu 5V step-down regulator (For powering amp & voice module)
1x Self-enclosed mini speaker
1x 10K audio-taper Pot for volume control
1x SPDT switch with BBM switching (For sending GPS or Telemetry to Voice Module)
1x 2S 1500mA LiPo pack
1x LiPo charging port with separate Run/Charge switch
1x On/Off LED laminated power switch
And last but not least, an adjustable cell phone cradle

 

[jqavins]

I looked that up. 200° C for motors under 160 n-s, 220 for above. Except for single use motors above 80 n-s, when it's 316. In other words, much higher than most epoxies are rated for.

I would assume, since the regulation is written specifically for these rocket motors, that the numbers are based on what is realistically achievable. It would surprise me if the actuals are much lower. There will be some margin built in, so I expect the actuals are in the ballpark of 10 to 20 degrees lower.

On the other hand, since we know that we don't get 2nd degree burns from removing cases after a flight, it's clear that those are peak temperatures, and the cases cool off quickly after the burn is complete. So the duration, or better yet the whole time-temperature curve, is important. And getting that from the test data is probably pretty difficult, and in reality it depends on the MMT's thermal properties as well as the motor's.

@BrendanH69, your best bet is probably to make a tube, stick the motor you plan to use in it, and ground test. If you're able, it'd be cool to place a thermocouple or two in the tube and get that time-temp curve.

 

[BrendanH69]

I would assume, since the regulation is written specifically for these rocket motors, that the numbers are based on what is realistically achievable. It would surprise me if the actuals are much lower. There will be some margin built in, so I expect the actuals are in the ballpark of 10 to 20 degrees lower.

On the other hand, since we know that we don't get 2nd degree burns from removing cases after a flight, it's clear that those are peak temperatures, and the cases cool off quickly after the burn is complete. So the duration, or better yet the whole time-temperature curve, is important. And getting that from the test data is probably pretty difficult, and in reality it depends on the MMT's thermal properties as well as the motor's.

@BrendanH69, your best bet is probably to make a tube, stick the motor you plan to use in it, and ground test. If you're able, it'd be cool to place a thermocouple or two in the tube and get that time-temp curve.

If I can't get real data, then maybe a home made test method could be possible. Motors are scare and super expensive here, so would be idea if it could be done on a flight. Let me think about that.

I'm thinking the same way as you - we all have experience that our cases (incl. DMS motors) are hot to handle when we recover them, but my impression is that they're never as "baking oven hot" as as the the NFPA 1125 limits. That being said, the peak case surface temps are going to be around motor burnout, which is usually significantly earlier than when we walk up to the rocket and recover it.

For the moment, I'm curious that the real data MUST be out there, because it is required to be measured and recorded during certification otherwise there'd be nothing to back up the "pass" declaration if the Fire Authorities were to ask for the evidence.

The temperature limits stated in NFPA 1125 7.4 of 200oC (392oF), 220oF (428oC) and 315oC (599oF) are pretty big figures and probably easy to achieve in the certification process. However, being 10 or 20 degrees under them as you surmise would still be very challenging for the epoxy within a composite structure of a MMT or MD airframe. So, how do we know which epoxies would be acceptable for the specific application when scratch building MMTs, especially for HPR and long burn HPR motors? What epoxy do Aerotech use in their DMS FWFG cases, because clearly it must be good stuff to survive both the surface temp requirement AND the structural, pressure and failure mode requirements that are also required.