Small, 38MM Minimum Diameter AV Bay

[K'Tesh]

I'm looking to make an AV Bay that would fit inside of a tube coupler for a 38 MM body tube (~5" long), with a redundant system, but space is limited. Am I dreaming? Can just such a system safely fit in that small of a space (including batteries)? Pictures greatly welcomed.

Just to be clear, the area for the sled is about 5" long. The charge well is not factored into this length.

Thanks!

 

[boatgeek]

You're probably looking at two Eggtimer Quarks or equivalent on one side of the sled and a pair of LiPos on the other side if you want full redundancy. I'd put the switches between the batteries. The Quarks are less than two inches long, so they should be OK for length. The only thing I'm not sure of is if the diameter would let you fit the altimeters on one side and the batteries on the other. You may need to get some long, skinny batteries.

 

[rharshberger]

I'm looking to make an AV Bay that would fit inside of a 38 MM body tube (~5" long), with a redundant system, but space is limited. Am I dreaming? Can just such a system safely fit in that small of a space (including batteries)? Pictures greatly welcomed.

Just to be clear, the area for the sled is about 5" long. The charge well is not factored into this length.

Thanks!

Contact Steve Thatcher at SMT Designs he can make you one at a reasonable price. Somewhere I have a review thread of his 38mm bay I used in my 38mm MD Rabid Weasel.

 

[dhbarr]

Bear AltiDuo SMT + AltusMetrum Telemini v3 , all sorted with plenty of space and weight budget left over.

AltiDuo SMT: ~8g, 18*56mm
Telemini v3: ~21g, 0.5*1.7in

 

[manixFan]

I've done a couple with a Perfectflight CF and a Featherweight and LiPo batteries, using magnetic switches. Fit inside a 38mm tube. Nothing fancy, just G10 plate. Overall length is just over 5" but could easily be made shorter. Using the magnetic switches really simplifies installation. That's the first photo. The second one fits inside a 38mm body tube (not a coupler) and is about 6" long. It could easily made thinner and shorter. Both have flown and worked successfully.

Using magnetic switches makes a huge difference when trying to fit into a small space.


Tony

 

[Worsaer]

Featherweight also makes a slick avbay that pairs with the Raven. It’s pretty slick.

 

[K'Tesh]

I've done a couple with a Perfectflight CF and a Featherweight and LiPo batteries, using magnetic switches. Fit inside a 38mm tube. Nothing fancy, just G10 plat. Overall length is just over 5" but could easily be made shorter. Using the magnetic switches really simplifies installation. That's the first photo. The second one fits inside a 38mm body tube (not a coupler) and is about 6" long. It could easily made thinner and shorter. Both have flown and worked successfully.

Using magnetic switches makes a huge difference when trying to fit into a small space.


Tony

View attachment 378446
View attachment 378447

Thanks for the info and the photos...

I cringe when I realize that I forgot to state that the AV bay shold take into account that it needs to fit inside a tube coupler for a 38mm tube.

 

[gtg738w]

Pulse batteries has added some long skinny sizes lately. I have used a few of the 2s 300s and if that’s too big I go down to the 1s 220. They also have a 2s 450 that is the same cross section as the 300 but longer.

https://www.pulsebattery.com

 

[manixFan]

Featherweight also makes a slick avbay that pairs with the Raven. It’s pretty slick.

Funny that I forgot I have one and should have mentioned it. It is very slick and only takes up 2". While it is a bit of a pain to put together, once setup it's very easy to use. The 38mm version fits in a coupler and includes a magnetic switch and integrated battery charger. I like having a barometer only and an accelerometer when doing redundancy because I like the data I get with an altimeter. But you could easily fit 2 Stratalogger CFs in a 5" 38mm coupler, especially with magnetic switches. The magnetic switches are a bit pricey, but once you use them it's hard to go back.


Tony

 

[cerving]

Two Quarks with two Featherweight screw switches and two 120 mAH 1S batteries will fit. It will still be tight... you will probably need to be a little creative with the bulkplate mounting, i.e. skip the allthreads and find another way to hold it together. On my Mongoose 29 CF, I epoxied one bulkplate to the coupler, and epoxied a brass tube across the inside of the other bulkplate... there's a hole drilled through the coupler that you slide a pin in to hold the bulkplate in. No allthread.

 

[PhysicsGuy]

Pulse batteries has added some long skinny sizes lately. I have used a few of the 2s 300s and if that’s too big I go down to the 1s 220. They also have a 2s 450 that is the same cross section as the 300 but longer.

https://www.pulsebattery.com

View attachment 378452

They do have a nice selection of batteries. Do you know if these have the over-current protection or not? I know at least PerfectFlite and Altus Metrum recommend using LiPo batteries that do not have over-current protection. I know that some RC batteries do not have the over-current protection, but the vendors are not very good about telling you if they do or not.

My smallest current (2.6 inch) e-bay has room for a 9 volt battery. But, I have an Apogee Aspire (29mm) that I plan to set up for DD with the Apogee e-bay and there is no way a 9-volt battery will fit . So, I'll be looking for a LiPo battery to use with my StratoLogger CF.

Thanks.
--MARK
NAR 65148, L1

 

[gtg738w]

They do have a nice selection of batteries. Do you know if these have the over-current protection or not?

They do not, they are bare cells assembled into packs. No over current or low voltage protection. You can use a small resistance in series to limit the voltage drop but otherwise they will give everything they can. The internal resistance is quite low.

 

[Eric]

My version is a little longer then you mentioned, but it could be made shorter.

I used a Raven3 on a power perch and an Eggtimer Quantum. The quantum will be plugged in at the prep table. And the Raven just uses a magnet. So no physical switches are needed on this sled.

I used a pulse 300 mAh 2S for the Quantum, but had to separate the cells and lay them flat underneath the sled. Double-sided tape and zip ties secure it.

The sled uses a single 10/32 all thread. And was offset low in the tube to give the power perch room to fit. The power perch wire terminals also needed to be sanded down on the top corner. And the battery plastic ring was removed for clearance.

 

[swatkat]

I've got one that does exactly what you trying to do, but with two quarks and two 260mAH LiHV's with the micro connectors. Same set up as Eric's (I printed those) but just 5.25" long with an M4 central rod. You could easily get it all into 5". Thin wall BT-60...