Best Practices -- Featherweight AV-Bay -- Active End Up or Down ?

[kjhambrick]

Question for the Experts ...

I am about ready to drill holes in my main chute compartment for Barometric Pressure readings and to attach some screws.

But before I do ...

I know the Blue Raven will work in any orientation but I like having 'natural' signs on my raw acceleration data so if it is all the same, I would prefer to install my 38mm AV-Bay Active End Up.

Assume I don't need an e-match on the Blue Raven channel 4 in my single-stage rocket ...

Is it still best to orient the Featherweight 38mm ( or 29mm or 24mm ) AV-Bay Active End Down ?

If so why ?

Does anyone know of any issues with setting up the AV-Bay with the Active side up ?

Thanks !

-- kjh

 

[Buckeye]

If it has a vertical battery connector like the Power Perch, then I orient the connector on the bottom, so that the battery accelerates into the connector during thrust. In theory.

In reality, it probably makes no difference if the battery is well-secured.

 

[kjhambrick]

If it has a vertical battery connector like the Power Perch, then I orient the connector on the bottom, so that the battery accelerates into the connector during thrust. In theory.

In reality, it probably makes no difference if the battery is well-secured.

Good Point re. Battery Orientation, @Buckeye !

That would mean Active End Down on the Featherweight AV-Bays and Power Perch Down when I fly that.

Turns out, when considering the female battery connector, I've been flying my Power Perch up-side-down

It hasn't mattered yet with the 20-G or so flights I've done but I should re-think my Power-Perch orientation too for when I start flying more aggressive motors !

Thanks !

-- kjh

 

[manixFan]

I fly a lot of the Featherweight stuff in many configurations, and the battery orientation should not matter. As @Buckeye says, the battery needs to be secured well enough no matter what orientation it is in during boost or deployment. With the PowerPerch, I use a jumper cable between the battery and PP so the battery isn't plugged directly into the board. It's just been too hard to keep it reliably secured otherwise in my opinion. With a short jumper, I can place the battery in a box that is secured to the AV bay mounting plate. If the battery moves, the jumper has plenty of slack.

For the Featherweight AV bays, I've designed and printed 3D mounting plates that secure the battery in place instead of the pre-cut mounts that come with the kits. That allows me to accommodate some of the batteries I've purchased that are slightly different lengths than the included mounts are designed for.

Lately I've been using all 4 outputs of the Raven to fly redundant charges with a single altimeter. I fly a lot of high value (to me anyway) carbon fiber minimum diameter rockets where I don't always have room for two altimeters, but I like the security of a backup charge. It's a bit of a challenge, but worth the effort. Adrian has been good about adding an extra solder pad on the small AV bay lids to make that possible.

As long as your connections can handle the forces that a sharp motor burnout or deployment charge can throw at it, you should be good. But I like to be prepared for the hard knocks of flying extreme flights.


Tony

 

[OverTheTop]

Don't just assume boost acceleration is the one you need to worry about. Depending on masses and charge size the impulse from the ejection charge can easily exceed boost accel. Consider both nudges.

 

[kjhambrick]

Don't just assume boost acceleration is the one you need to worry about. Depending on masses and charge size the impulse from the ejection charge can easily exceed boost accel. Consider both nudges.

Good Call, @OverTheTop !

Last night I reviewed my Acceleration -vs- Time Data for my flights and a couple other user's flights and in every case, the ejection charge shock exceeded the max acceleration ( edit: due to motor thrust ) by quite a bit.

In addition, there is usually a negative shock about the same magnitude or even a little greater than the initial shock due to the ejection charge.

And looking at the accelerometer plots that @Adrian A has posted, the same is true for his flights that I reviewed too.

Bottom line: maybe the orientation of the Blue Raven does not matter as long as the LiPo is secure ?

Thanks !

-- kjh

 

[kjhambrick]

I fly a lot of the Featherweight stuff in many configurations, and the battery orientation should not matter. As @Buckeye says, the battery needs to be secured well enough no matter what orientation it is in during boost or deployment. With the PowerPerch, I use a jumper cable between the battery and PP so the battery isn't plugged directly into the board. It's just been too hard to keep it reliably secured otherwise in my opinion. With a short jumper, I can place the battery in a box that is secured to the AV bay mounting plate. If the battery moves, the jumper has plenty of slack.

Thanks for the Idea, Tony ... I'll take a look at the power perch battery connection too !

I think I've got the LiPo locked in place axially and laterally but that female LiPo connector is going to wear out eventually.

Now that I think about it, a sacrificial male-female extension cable would be a good idea to reduce wear -n- tear on her.

For the Featherweight AV bays, I've designed and printed 3D mounting plates that secure the battery in place instead of the pre-cut mounts that come with the kits. That allows me to accommodate some of the batteries I've purchased that are slightly different lengths than the included mounts are designed for.

As for different Batteries and the AV-Bays ...

I broke my 38mm AV-Bay last weekend when I installed a new E-Flite 150 mAh 1S Battery and tightened the nuts on the passive end.

The breakage was odd ... when I tightened the passive end nuts, the APO squib lost the connection but the voltage returned when I loosened the nuts on the passive end.

MAIN and 3RD were fine but I didn't try 4TH ...

After I figured out what was happening, I measured the length of the new E-Flite LiPo and it was about 1/16 inch longer than the old one I used to set up the plywood LiPo pieces.

I am thinking I damaged something on the active-end underneath the female battery connector.

I ordered a new 38mm AV-Bay from @Adrian A and it should be here Friday.

I was also thinking I needed to come up with a different way to secure the battery and I have been messing with ideas too.

While I am at it, I also want to find a way to prevent any wiggle on the free-end of the Blue Raven down ( or up ) by the passive end.

Any wiggle at all in the Blue Raven would definitely mess with the quality of the accelerometer and gyro data so it needs to be locked down without placing any strain on it.

So I messing with ways to lock down the free-end of the Blue Raven at the same time I secure the LiPo in the female connector.

I would LOVE to see what you came up with for battery retention !

Lately I've been using all 4 outputs of the Raven to fly redundant charges with a single altimeter. I fly a lot of high value (to me anyway) carbon fiber minimum diameter rockets where I don't always have room for two altimeters, but I like the security of a backup charge. It's a bit of a challenge, but worth the effort. Adrian has been good about adding an extra solder pad on the small AV bay lids to make that possible.

Yes, I imagine I'll keep flying without redundant charges until it doesn't work one time ( well ... maybe twice )

As long as your connections can handle the forces that a sharp motor burnout or deployment charge can throw at it, you should be good. But I like to be prepared for the hard knocks of flying extreme flights.

Thanks for all the input Tony !

Good stuff here !

-- kjh

 

[Dave S.]

> If it has a vertical battery connector like the Power Perch, then I orient the connector on the bottom, so that the battery accelerates into the
> connector during thrust. In theory.
>> In reality, it probably makes no difference if the battery is well-secured.

Thank you - that is exactly what I was intending on doing for the rocket I have just started building.

 

[manixFan]

Here's an example of one of my early uses of a jumper for the battery. The BR is mounted to a 3D printed sled attached to the existing G10 board. It's for a 38mm MD rocket, and the height of the PowerPerch caused some mounting issues. Since I used the existing G10, the board was not wide enough for the battery. I printed a separate battery box that is stuck down with two-sided tape. The small screw puts a bit of pressure on the connector to hold it in place. The surface area of the battery box relative to the holding power of the tape is such that it is actually very hard to remove the battery box. I tested it with a hot air gun to make sure it didn't soften under expected operational temps.


Tony