Altimeters?

[John_lennon]

Hi,
I'm relatively new to the forum I'm getting into the hobby to have some bonding and learning time with my grandson. As we were out in the launch field he asked how do we know how high the rocket goes or what it's speed will be. I realize that an altimeter is necessary for this but can they go in any rocket? I'm unaware how large they are so I don't know if you need a certain size body tube for them to fit inside. If so what's the smallest tube they can go in? I've seen a couple builds with a dedicated electronics bay. Is this necessary for this type of electronics? I saw a video where they just attached it to the nose cone loop. Is this common practice with just the altimeter? Also which altimeter is a good one to get, that's not a huge purchase for a total beginner? Thanks, Dyl

 

[mtnmanak]

Welcome to the forum!

In my opinion, your best bet would be a Jolly Logic Altimeter 3:

https://jollylogic.com/products/altimeterthree/
It is a simple device, you can control it from your phone via bluetooth and it really can be just stuck in any rocket that has enough room for it. I often just attach it to the nosecone of a rocket with a fishing swivel or piece of kevlar string.

The unfortunate part is that, like most electronics right now, it is in extremely short supply and is difficult to find. If you can find one, grab it right away. If not, you may have to wait or go with another option if you want something right now. There are a lot of other simple altimeters on the market, but most of them are computer boards that need to be mounted to something.

 

[mbeels]

Hello, and welcome to the forum. There quite a lot of altimeter options, and some of them are small enough to fit into BT-20 (18mm tube) . Apogee has a list of some options, and FlightSketch is coming out with some cool products:

https://www.apogeerockets.com/Electronics_Payloads/Altimeters
https://www.rocketryforum.com/threads/flightsketch-products-for-2020.156285/
One choice to make is recording or not-recording. A recording altimeter lets you see the altitude data during the flight, and calculate such things as decent rate. Some use accelerometers which provide a better measure of velocity, but the barometer sensor works well for altitude.

 

[mtnmanak]

If you are comfortable mounting a board to some kind of holder, Perfectflite also makes some small, cheap altimeters.

I don't think you can find anything cheaper or smaller than the FireFly:

https://www.perfectflitedirect.com/firefly-altimeter/
Big problem is they have not had the FireFly Field Data Display available for a long time, so the only way to read the output is to interpret the flashing lights after the flight.

A step up is their PNut altimeter which adds a computer interface to download all the flight data:

https://www.perfectflitedirect.com/pnut-altimeter/
The Pnut is about the same size and functionality of the Jolly Logic, it just doesn't have a nice plastic case. It includes a built in battery which is nicer than trying to figure out how to get a battery and an altimeter mounted in a small rocket.

 

[user 35280]

I believe the FlightSketch Comp is one of the smallest Bluetooth altimeters currently available,
https://flightsketch.com/store/catalog/flightsketch-comp_229/

 

[mtnmanak]

Biggest issues you will encounter with all these circuit board based altimeters (like the FlightSketch, et al) on a Low Power Rocket are:

- How do you mount it in a small rocket so it doesn't get busted up?
- How do you mount the separate battery?
- How do you make it easy to move from one rocket to another? (It makes no sense to buy a $50 altimeter and only use it in one $20 rocket)

It is what makes the Jolly Logic so appealing for LPRs. When you get to MPRs, you may have more room to work with.

In the absence of the Jolly Logic Alt 3, if all you want is "good enough" altitude reporting, the Jolly Logic Alt 1 or Alt 2 should be fine and those are available now.

 

[mtnmanak]

Apologies, I did forget about Dino Chute's line of alti pouches:

https://www.dinochutes.com/Altimeter-pouches_c16.htm
For altimeters like the FlightSketch Mini or the Perfectflite PNut that have an integrated battery, the pouches work as a great alternative to the Jolly Logic products.

 

[user 35280]

When I use my FS Mini I mainly use it in a payload section. But if the rocket doesn’t have a payload section I put it inside my SDR 3D printed case. I haven’t had any problems with damage or anything.

 

[tsmith1315]

Yes this is heresy, but...

To start out, you could go old school with a plumb and show your grandson why math is a good thing. It wouldn't take much more than a piece of cardboard, a weight and string. Measure the angle and use a calculator to find the height.

Let him track the rocket, it doesn't matter if it's accurate. He'll have an answer, your wise grandpa status will elevate, and the curiosity generated may endure far longer than expected. There's plenty of help here if that sounds interesting.

My opinion only.

 

[mtnmanak]

Yes this is heresy, but...

To start out, you could go old school with a plumb and show your grandson why math is a good thing. It wouldn't take much more than a piece of cardboard, a weight and string. Measure the angle and use a calculator to find the height.

Let him track the rocket, it doesn't matter if it's accurate. He'll have an answer, your wise grandpa status will elevate, and the curiosity generated may endure far longer than expected. There's plenty of help here if that sounds interesting.

My opinion only.

If you go down that path, at least get the cool, old school Estes Altitrak!

https://estesrockets.com/product/002232-altitrak/
(BTW, you can find this way cheaper online than from Estes site)

 

[cerving]

If you don't mind a little soldering, you can get an Eggtimer ION kit for $20, which will wirelessly give you your apogee and other data via WiFi to your phone. That could be a good project with your grandson too... especially if they are interested in electronics.

 

[teepot]

I think any of the Jolly Logic altimeters would be a good choice. I have 2 Altimeter 3's and 2 chute releases. As mentioned above there are quite a few options. Take a look at all the options mentioned and then you can decide which one fits your budget and provides the information you want.

 

[tjkopena]

To start out, you could go old school with a plumb and show your grandson why math is a good thing. It wouldn't take much more than a piece of cardboard, a weight and string. Measure the angle and use a calculator to find the height.

Recently discovered this highly sophisticated piece of technical instrumentation in a box of rocketry stuff that's been in my parents' basement ~30 years...



No reason you can't use and teach about an inclinometer alongside also flying an altimeter.


Plus side of the Jolly Logic altimeters for this kind of use with kids is they're very physically robust, have a built-in USB-rechargeable battery, are super straightforward to use, and no phone required (though the 3 can use one). Big downside is they won't fit in less than a BT50 (24mm). I have a Jolly Logic 2 specifically to have an altimeter my daughter and other kids could handle easily and get basic flight data immediately on retrieval.

To get an altimeter into a BT20 (18mm, A--C motor diameter), which many beginner rockets use, there are several options, and some are actually lower cost. But as far as I'm aware they're all somewhat less robust because of exposed circuitry, and not as accessible---you either have to interpret beeps or blinks to get the data, connect a phone, or use an adapter to a computer or display. Flight Sketch Mini, PerfectFlite Firefly, and the Altus Metrum Micropeak are examples.

To get into a BT5 (13mm, 1/2AT diameter), like many other beginner rockets use, you need a very small altimeter. Doesn't necessarily mean more expensive, but based on size alone I wouldn't consider them kid friendly. Similar robustness and accessibility questions also apply. FlightSketch Comp is an example though that's pretty easy to use other than requiring a phone and the LiPo battery requiring extra care compared to a coin cell or so on. Adrel's altimeters are another, but they don't seem especially beginner friendly.

EggTimer has a bunch of cool units too, but AFAIK none of them fit in less than a BT50.


This is a subject that's been a good bit of interest to me, flying a lot of small rockets w/ my daughter, hence the comments. I confess though that I lost some enthusiasm for putting altimeters in rockets when it turned out hers always fly higher than mine...

 

[user 35280]

Estes has a basic no frills altimeter and it’s very reasonably priced here,
https://www.acsupplyco.com/estes-model-rockets/estes-rocket-parts-and-accssories/estes-altimeter

 

[user 35280]

https://www.acsupplyco.com/estes-mo...6-mini-altitrack-model-rocket-altitude-finder
https://www.acsupplyco.com/estes-mo...and-accssories/estes-altitrak-altitude-finder