Just recieved Telemetrum, never built a sled before.

[topper]

I have,as far as rockets go:
1-1.9" Arreaux
1-2.6" Initiator
1-2.6" HV Arcas
as well as numerouse small LPR estes rockets.

Please give me some pointers, do's and don'ts of building a sled.
I did attempt one but it weighs WAY TOO MUCH(more than the Initiator).
Could I just build a simple bubble wrapped sled and throw it down the upper tube to the bulkhead? I know I'll have to drill a couple of holes to get altitude.
I'll probably have to secure it with 3-4 plastic rivets so I dont lose it out the nose, if it should come loose.

Any helpful tidbits would be awesome. Pics would be great.
Thanks
Topper

[Zeus-cat]

I would start with a sled for the largest diameter rocket you have. The more room you have the easier it is to work with. Is this going to be set up for dual deploy? If yes, then you need to run wiring out the top and bottom of the ebay, plus have a battery and a switch inside the ebay.

If you are only using it to record data then all you need is the altimeter and a battery on the sled. Heck, I have launched altimeters with them just stuffed inside a body tube with wadding to keep them from rattling around if I just use them to record data.

If I am doing a sled for dual deploy then I secure everything in the ebay to the sled. I put the altimeter on one side and the battery on the other just in case things go terribly wrong. A 9 volt battery can do a lot of damage in a crash. I use cable ties to hold the battery on the sled.

You also need room for the switch. The switch needs to be activated when the rocket is on the pad, so have some way to turn it on and off from outside the rocket. A popular way is to use a heavy duty push switch and have a hole in the ebay that you can pass a thin steel rod through to push the switch on and off. Make sure you can align the switch with the hole when the rocket is assembled. Making stuff fit only one way will help you get everything aligned when you assemble the ebay for flight.

I use birch plywood for the sled. This is the thin plywood found in some hobby shops that people use for model airplanes. It is strong, lightweight and easy to cut and drill. I drill holes for mounting the altimeter and use very small screws and nuts to hold in place. Make sure your altimeter sensor can breathe; you may need to drill a hole in the sled so that the sensor has access to the air.

I also try to get the sled to fit tightly between the bulkheads of the ebay. No sense having it sliding around in flight. I also use two tubes epoxied to on side of the sled to hold it in place on the steel rods that hold the ebay together. The tubes slide over the rods.

I hope this helps.

[cbrarick]

LOC/Precision sells ebay kits - every thing you need even directions.
Or you could do it yourself ....get Modern High Power Rocketry by Mark Campagna and you will have alll the instructions you need.

[topper]

Well here's pics of Attempt #2. LOTS lighter and built to fit a 2.6" tube.
Still have to bolt the board to the sled and tape down the antenna.

And a pic of my only 3 MPRs. Hot pink and neon green is awsome for visibility. Especially with my failing eyesight.(comes with age I guess)

I should have been thinking a little farther ahead of myself. I glued in the body couplers. A little cutting I guess.

How critical if any is it to have the weight of the sled centered on the longitudinal axis?
Recommendations on a trusty low power igniter for dual deploy. Telemetrum will be powering deployment.

[topper]

here's the pics

[Sandy H.]

Looks like a pretty standard DD set-up, but a quick question: Where are you going to attach the shock cord?

I've never spent too much time positioning the components for weight balance. About the only thing I tend to do is to put the battery on the opposite side of the sled than the electronics. That way, if it does come loose (never happened, but just in case) it won't smash the expensive stuff.

I do tend to use zip ties for the battery, but the electronics are connected to the sled with machine screws. I see you used balsa for the sled, which is probably fine. Most kits come with plywood, but I would be surprised if there were ever enough forces on the sled during a nominal flight to make the balsa a bad choice. Might not be good for multiple attachments of the screws, though.

I use Quest Q2G2's for deployment. They are the ones with blue leads and ignite with lower current than Estes and other common igniters. A lot of people use e-matches as well. Ground test with the Q2G2's and see if they will meet you needs as they aren't too expensive and are probably the easiest thing to get/posses without additional paperwork.

Maybe someone else will chime in with other pertinent comments.

Good luck.

[topper]

On my way uptown right now to find some eyebolts for the cord attachments..
I already figured out that balsa was a bad choice. Way too soft of material for screws.
Thanks for your input.
I just don't want a disaster on my first dual deploy.
I WILL BE GROUND TESTING. Lost 1 last year. It still hurts. Don't know if it deployed or if it lawn darted. GPS. I' find it now!

[bdale]

Please give me some pointers, do's and don'ts of building a sled.

Any helpful tidbits would be awesome. Pics would be great.

I just put a pdf copy of the insert we include with the Altus Metrum hardware installation kit sold through Apogee on our site at http://altusmetrum.org/Uses/InsertSheet.pdf. The pictures and hints may help.

Good luck, and let us know how things go!

[Handeman]

I saw an earlier post that said to build the sled to fit your largest rocket. I would recommend building it to fit the smallest.

My first sled was for my L1 which was build from 2" ID BT. The bay was about 1.9 ID. I used 6mm ply with the 9V battery on one side and the altimeter on the other. I put a tube along each outer edge of the sled, one on the front, one on the back, that the threaded rods run through.

When I build av bays for 3" and 4" rockets later, I made the threaded rods the same width as the 2" bay and the sled would drop into all the av bays. Much easier then moving the altimeter from sled to sled. I use very dense foam as spacers in the larger/longer bays so the sled wouldn't slide up or down.

I also build the switches into the av bays with long wires. I can pull the ends of the wires out and easily attach them to the altimeter before sliding the sled into the bay. Don't for get about twist and tuck, or variations. That is still a very reliable method of powering the altimeter.