Mounting Flight Computers

[LarryC]

There was a threat like this on the Parrot Featherweight forum. Figured the discussion would work here as well, so here's an opening shot:


I have an extremely simple way to mount accelerometers/altimeters with an existing electronics bay. It invloves plastic cutting mats, which have largely replaced kitchen cutting boards. These are available at kitchen supply stores and departments. (I get mine at Sears, for example) Cutting mats come in a variety of thicknesses and stiffnesses. They are frequently sold in packs that reflect that variety.

For HPR and mid power rockets, I cut out a piece that just fits vertically in the electronics bay. Ideally, it can be held in place by the nose cone. In such rockets, I use a piece that is a tad wider than half the inside circumference of the bay. I simply screw the instrument to the plastic strip and insert the (stiff but flexible) strip inside the rocket, allowing the flexible material to conform to the inside of the body tube. I then secure the nose cone with a single screw.

***
The trick is that it conforms to the circumference, and it doesn't buckle under acceleration in the curved state. (Naturally don't obstruct the static port...) Adjust the mat thickness to expected accelerations.
***
I have never tried it in model rockets, which have flimsier body tubes. For these I would try a thinner cutting mat, and I would size it such that it goes almost all the way around the inside of the body tube, allowing just enough space for the static port.

Regards,
-LarryC

 

[LarryC]

Replying to my own post to add the way batteries are mounted.

Since the plastic strip in the above technique extends from the bottom of the electronics bay to the bottom of the nose cone, there is normally plenty of room to mount a 9 volt battery below the instrument.


Duct tape (I like Gorilla Tape) works nicely.

-LarryC

 

[skycopp]

That seems interesting. Never thought of a kitchen cutting mat, but will have to check into it. thanks for the tip.

 

[jcsalem]

This sounds cool and a lot easier than cutting a G10 electonics sled which it what I usually use.

Can you take a picture of this? I have a hard time picturing the whole layout.

Jim

 

[LarryC]

I can snap a picture, but it will be a few days. Leaving town on business just now.

This sounds cool and a lot easier than cutting a G10 electonics sled which it what I usually use.

Can you take a picture of this? I have a hard time picturing the whole layout.

Jim

 

[LarryC]

This sounds cool and a lot easier than cutting a G10 electonics sled which it what I usually use.

Can you take a picture of this? I have a hard time picturing the whole layout.

Jim

Here is a picture of an ARTS flight computer so mounted in a LOC Weasel. (The picture has the unit pulled partially out for adjustment.) I have flown the same instrument in a LOC Vulcanite and an Aerotech Initiator with the same technique. Note the screw in the side of the nose cone. That holds the cone and the assembly in place during flight. Naturally, the instrument is screwed onto the plastic sheet too.

(My wife asks that I tell you the floor is in my dirty little workshop and not in he sections of the house where she holds sway...)

The plastic-wrapped assembly can be slid in and out while the rocket is on the rod. The loose wires in the photograph are connected with tape to turn the unit on. The unit will begin calibrating at the correct launch angle when it comes up. (For me, that angle was not always vertical. That's another story.)

View attachment DSCF26911.JPG

 

[pyrovette20]

Why dont you just use fiberglass or good ply. How much do the cutting mats go for. I can get good ply for a couple dollars a foot.

 

[LarryC]

Why dont you just use fiberglass or good ply. How much do the cutting mats go for. I can get good ply for a couple dollars a foot.

I guess the point is that Fiberglass and plywood have to be mounted. Cutting mats conform to the inside of the tube without mounting, and can be held in place by the nose cone. The technique is practical through level I stuff.

The mats are dirt cheap.

Hope that helps.
-LarryC