F-Motor Record???

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Oldboy
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Re: F-Motor Record???

Postby Oldboy » Wed Oct 26, 2016 12:22 am

Try a big mylar streamer as a visual reference. Heap of flights on my Blackhawk 24 and still going up and down
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Jordz
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Re: F-Motor Record???

Postby Jordz » Wed Oct 26, 2016 12:40 am

How big is your streamer? Ive been looking at doing a MD 26mm rocket with a streamer and im not sure if a 5m x 5cm streamer will be noticeable at high alts and long distances...

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Viking
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Re: F-Motor Record???

Postby Viking » Wed Oct 26, 2016 11:45 am

Go for a metallic mylar streamer like below, on a sunny day you should see plenty of flashes on the way down.
I got lucky a couple of weeks ago, the local newsagency was clearing a pile of old crap and and I scored a huge roll of gold streamer for 50 cents.
Do a sim for the length, you'll have to decide on a comprimise... visibillity (long) or descent rate (short).
You'll be surprised how slowly they can descend(and therefore drift) with a long streamer.
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OverTheTop
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Re: F-Motor Record???

Postby OverTheTop » Wed Oct 26, 2016 12:00 pm

I remember reading somewhere that about 13:1 aspect ratio would give the slowest descent. Not sure what material they were using but I suspect it would not make a big difference (assuming sensible materials are compared :) ).
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Happy Heyoka
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Re: F-Motor Record???

Postby Happy Heyoka » Wed Oct 26, 2016 5:37 pm

OverTheTop wrote:I remember reading somewhere that about 13:1 aspect ratio would give the slowest descent. Not sure what material they were using but I suspect it would not make a big difference (assuming sensible materials are compared


Appendix C of Sampo Niskanen's thesis "Development of an Open Source model rocket simulation software" aka the Open Rocket Technical Manual has a decent write up and there are some external references.

Here's a table of the width/length/CD:
streamer_drag.jpg
streamer aspect vs drag
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Re: F-Motor Record???

Postby jhurst7 » Thu Oct 27, 2016 7:29 am

I took out the PVC tube and baking paper last night and sanded back the edges.
The picture should be below. It is around 1mm thick, although I will be checking that today.

As for the suggestions about the streamer, I wasn't really planning on using one as:
a) They seem to take up a lot of space in my body tube.
b) It doesn't seem to be as effective as a parachute.

However, maybe I could attach a streamer to the top of the parachute, maybe above a spill hole, and could use that to visually track it with binoculars. I'm not sure about this at the moment. I'm still looking into tracking.
Thanks

-James
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Re: F-Motor Record???

Postby jhurst7 » Thu Oct 27, 2016 3:49 pm

After checking the ID and the OD I have encountered a problem.
ID=21mm
OD=23.5mm

As you can see, nowhere near 24mm.
I'm going to roll another tube, however, this time I will roll it onto this tube itself. Hopefully, that results in a better tube.
Thanks

-James
L1- AMRAAM 2- H54

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Re: F-Motor Record???

Postby jhurst7 » Thu Oct 27, 2016 4:35 pm

What does everyone think of this setup?
Has anyone used this before?
I'm pretty sure Vance has used on of these before, although I can't say.
http://rctimer.com/product-817.html

Thanks
-James
L1- AMRAAM 2- H54

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Re: F-Motor Record???

Postby vance2loud » Fri Oct 28, 2016 5:05 pm

I've used identical radios from another supplier.
So far I have received signals from 8000 feet and ground distances of around 1 km.
replace the supplied antenna with ones that are actually tuned to 915-928mhz and you will get a better range.
These 48mm antennas tend to be better than what is supplied, http://www.nicerf.cn/product_92_141.html
and they save you a bit of length inside the rocket.
search around and you will find even better options
For even better results look at the transceivers from RFDesigns,
The RFD900u http://store.rfdesign.com.au/rfd-900u-radio-modem/ is only 19mm wide, offers antenna diversity and supposedly up to 10km range.
combined with these http://au.mouser.com/ProductDetail/Anaren/66089-0930/?qs=pH7abCSN9NM0tHwbfikfEQ%3d%3d you have a very compact package.
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Re: F-Motor Record???

Postby Oldboy » Mon Oct 31, 2016 1:57 pm

A couple of meters of mylar rolled up doesn't take much space and you'd be surprised how visible it is flapping around on the ground even with little breeze and can be followed in the air
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Re: F-Motor Record???

Postby jhurst7 » Tue Nov 01, 2016 5:15 pm

Thanks guys,

What are some techniques that are used to create a Von Karman nose cone in a CAD drawing? I'm going to 3D print it.
Also, what would the thread sizes be on the interior of a 24mm motor hardware, something like an M23-0.5 or something like that?
Thanks.

-James
Last edited by jhurst7 on Tue Nov 01, 2016 5:27 pm, edited 1 time in total.
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OverTheTop
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Re: F-Motor Record???

Postby OverTheTop » Tue Nov 01, 2016 5:26 pm

You should be able to find on the interweb, or have someone send you, the 2D profile (a set of cartesian coordinates) that are for the VK nosecone of the correct size. I am not entirely sure if they scale. Have not checked the maths on that.

You can make a spline in your 3D cad program using the defined points, then build the rest of the NC around that. Your biggest problem will be the build height that the machine is capable of. You might have to print it in a couple of pieces and join them.

My 3D printed NC (4") was just able to fit into the build height of the machine I have access to, and that was only because I made an aluminium tip for it!:
viewtopic.php?f=6&t=5019&start=8
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vance2loud
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Re: F-Motor Record???

Postby vance2loud » Tue Nov 01, 2016 6:54 pm

Von Karman nosecone generator http://www.thingiverse.com/thing:804129

There's a few on thingiverse including one with the .SCAD files, just search for 'von karman' on thingiverse
TRA #15165 AMRS #50
I do it because i can, I can because I want to, I want to because you said I couldn't. - Unknown
I have not failed. I've just found 10,000 ways that won't work.
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jhurst7
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Re: F-Motor Record???

Postby jhurst7 » Tue Nov 01, 2016 7:37 pm

Yes, I had a look at that generator, it wasn't working on my computer though.

I'd tried it on another one and it worked...weird.
Thanks for that.

Just need to find out what the screw dimension are now for the Pro24 hardware!

-James
L1- AMRAAM 2- H54

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Viking
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Re: F-Motor Record???

Postby Viking » Wed Nov 02, 2016 3:37 am

It is just over 22mm major diameter, 24 tpi and 60°
Which makes it a 7/8" Unified "special" (UNS) thread.
Simon
WARS #24 / AMRS #54 L2


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