My Madcow Tomach (Money Burner)

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I think you need a further thought on that battery from a retention standpoint.
 
markkoelsch said:
I think you need a further thought on that battery from a retention standpoint.
Click to expand...

You're probably right. Do you think it would work if I wrapped electrical tape around the sled and the battery, in addition to the velcro? The velcro would probably be enough, since the battery weighs almost nothing, and if you have used this velcro before you know it it heavy duty. I think I will try using the tape to hold it even more securely.
 
On an i600r under thrust, that battery weighs several somethings. Same story on any kind of chute anomaly or unplanned geological excursion.
 
dhbarr said:
On an i600r under thrust, that battery weighs several somethings. Same story on any kind of chute anomaly or unplanned geological excursion.
Click to expand...

The battery weighs 20g, so under a 100G acceleration, it has a force of 2kg, or 4.4lb. The max acceleration from the L935 is 32G, so it has a force of .64kg, or 1.4lb. I think that tightly wrapped electrical tape should be able to hold that. I even picked up the whole sled by the battery and shook it, and it wasn't going anywhere even with only the velcro holding it. Plus the bottom of the battery is against the bulkhead, so the force should be transmitted straight to the bulkhead, with the tape and velcro just holding it against the sled.
 
A battery jarring loose is the number one reason DD flights fail. Or maybe it's loose wiring. Either way, I'd DEFINITELY do something with that battery. Do not count on just the Velcro.
 
Good luck Kyle,

I see that you have made some thoughtful modifications. Keep in mind if you sand the Proline 4500 it will turn from shiny black to an unfinished grey look, not a big deal but it just looks different than what you might expect. I cannot recall if you have a min diam retainer on this, if so here is one thing that happened to me last year and a new practice you may consider adopting.

I launched my Tomach on a k830 to 16K, on apogee my main deployed (I did a post flight analysis and made some changes to mitigate this). When I recovered the rocket, 3.5 miles away in the middle of a farmers 8' corn field, I noticed that my motor was about a 1/4 turn from falling out. It was completely screwed in and tight however the ride down from 16k over 3.5 must have been rough.

So now I add some blue loctite to the screw adapter before I put it in the retainer. This provides enough resistance and is easy to unscrew and cleanup as my retainer is removable.
 
mpitfield said:
Good luck Kyle,

I see that you have made some thoughtful modifications. Keep in mind if you sand the Proline 4500 it will turn from shiny black to an unfinished grey look, not a big deal but it just looks different than what you might expect. I cannot recall if you have a min diam retainer on this, if so here is one thing that happened to me last year and a new practice you may consider adopting.

I launched my Tomach on a k830 to 16K, on apogee my main deployed (I did a post flight analysis and made some changes to mitigate this). When I recovered the rocket, 3.5 miles away in the middle of a farmers 8' corn field, I noticed that my motor was about a 1/4 turn from falling out. It was completely screwed in and tight however the ride down from 16k over 3.5 must have been rough.

So now I add some blue loctite to the screw adapter before I put it in the retainer. This provides enough resistance and is easy to unscrew and cleanup as my retainer is removable.
Click to expand...

I kinda like the look of sanded 4500. It looks almost like it has metal flake mixed into it, and still looks shiny when sanded to a fine grit (I did down to 600).

Thanks for the tip about thread lock. I packed some after reading your reply. Now that I think about it, the motor was a little loose after the I600 flight. From now on I'll put thread lock on every time, it can't hurt.
 
dhbarr said:
But when that load is coming unexpectedly on multiple axes?
Click to expand...

The battery is right next to the mount for the bulk plate, so it can only move in one axis, fore and aft. The bulk plate prevents it from going aft, so the tape and Velcro only have to resist fore movement, which it should do easily.

noffie79 said:
A battery jarring loose is the number one reason DD flights fail. Or maybe it's loose wiring. Either way, I'd DEFINITELY do something with that battery. Do not count on just the Velcro.
Click to expand...

This battery is only for the tracker, and I have two trackers onboard. I wasn't going to rely on just the Velcro, I was going to use a zip tie in addition, but have decided to switch to multiple wraps of electrical tape.

The batteries for the altimeters are securely mounted in a Landru 3d printed sled, so there is no chance of them coming loose. I appreciate the concern though.
 
SUCCESS!!!!!!!!

I had a long narrative written out, but my browser crashed and I don't feel like rewriting it all right now, so I'll just put up some pics and video for now. I'll also say that the flight was a perfect flight with a max altitude of 24,258ft according to the TeleGPS.

IMG_7478.jpg

IMG_2260.jpg

IMG_2267.jpg

IMG_7480.jpg

IMG_2296.jpg

IMG_2309.jpg


[video=youtube;vFqsQWw9W9s]https://www.youtube.com/watch?v=vFqsQWw9W9s&feature=youtu.be[/video]

[video=youtube;BbDnjfAb8z0]https://www.youtube.com/watch?v=BbDnjfAb8z0[/video]
 
rc dude said:
SUCCESS!!!!!!!!

I had a long narrative written out, but my browser crashed and I don't feel like rewriting it all right now, so I'll just put up some pics and video for now. I'll also say that the flight was a perfect flight with a max altitude of 24,258ft according to the TeleGPS.
Click to expand...

Wow Kyle, nice! You look like you have quite the launch facilities, is that a bunker? BTW how far did she land from the pad?
 
mpitfield said:
Wow Kyle, nice! You look like you have quite the launch facilities, is that a bunker? BTW how far did she land from the pad?
Click to expand...
Thanks!

Yes that is a bunker. The Friends Of Amateur Rocketry site is used to test homemade liquid fueled motors, college team motors, etc., so they have bunkers, a machine shop, multiple test stands, and assembly buildings. It is an awesome place to be. It is also where Mythbusters filmed some of their rocket myths.

The rocket landed 4.2km from the pad, but we were able to go drive down a road so we only had to walk about 1200m to go get it.
 
rc dude said:
Thanks!

Yes that is a bunker. The Friends Of Amateur Rocketry site is used to test homemade liquid fueled motors, college team motors, etc., so they have bunkers, a machine shop, multiple test stands, and assembly buildings. It is an awesome place to be. It is also where Mythbusters filmed some of their rocket myths.

The rocket landed 4.2km from the pad, but we were able to go drive down a road so we only had to walk about 1200m to go get it.
Click to expand...

I saw that Mythbusters episode, very nice of The Friends of Amateur Rocketry to create such an amazing facility and provide it to hobbyists.

BTW I am interested in what you are planning for your L3? After your L1 and L2 certs there is no way you are sticking a baby M in a big rocket launching it to 3,000 feet, just to watch it float down and call it a day.

You will have to build a new rocket as an M won't fit in your Tomach anyway. Although Loki is apparently coming out with a baby M for their 54/4000 case, which I just happened to have. Problem is the case is 43" long so it won't fit in my Tomach either, so I will be building something custom, but not for the baby M. It will be for the L-2050 as I may take a shot at the Tripoli L single-stage commercial motor record.

This is more a dream at this stage and will come down to time, which I don't have a lot of these days, so we will see.
 
mpitfield said:
You will have to build a new rocket as an M won't fit in your Tomach anyway. Although Loki is apparently coming out with a baby M for their 54/4000 case, which I just happened to have. Problem is the case is 43" long so it won't fit in my Tomach either, so I will be building something custom, but not for the baby M. It will be for the L-2050 as I may take a shot at the Tripoli L single-stage commercial motor record.
Click to expand...

I've been thinking about this... any chance of using the motor as the coupler and going with a single nosecone av-bay, or do the lengths not line up right for that?
 
Provided the cg was ok, is there any reason a motor couldn't stick out the back of a MD rocket?
 
mpitfield said:
BTW I am interested in what you are planning for your L3? After your L1 and L2 certs there is no way you are sticking a baby M in a big rocket launching it to 3,000 feet, just to watch it float down and call it a day.
Click to expand...

I've been thinking of my L3, and originally I thought of a minimum diameter N, but that is too much money for a college student, haha. Right now my plan is an M2245 flying case, and attempting the M record. I am starting mechanical engineering in the fall, so I will have access to a full machine shop at college. I am thinking of machining a custom adapter to put a nose cone on the front of the case out of aluminum. I still have a few months to think about it, and my plan may change, but you can bet it will be extreme!
 
Man 25K for an L2 cert, that is serious! Has me re-think my L3 motor choice..hmm now where did the 98-6XL case go..

Congrats and the great flight
 
noffie79 said:
A battery jarring loose is the number one reason DD flights fail. Or maybe it's loose wiring. Either way, I'd DEFINITELY do something with that battery.
Click to expand...

Is this based on personal observation, or do you have data to cite?
 
Not a personal observation. I haven't had a DD flight fail...yet. I know many on here have had a 100% success rate. But I've done my fair share of reading. Even the owners manuals for my MW altimeters state that loose wiring is the most common cause of DD flight failures. And the 3D printed sled I have for my RRC3 has an enclosed battery compartment. Impossible for the battery to come loose. I'm assuming it was designed that way for a reason...
 
Batteries are important...but ah.... I think leading cause is a big jump.

I'd suspect too small/failed charges are the leading cause of failure... I've seen tons of those, none due to batteries.
 
I was really just stressing the importance of using more than just Velcro to secure the battery. I wasn't expecting to have to cite sources of data as proof. I'm sure we all know how important it is to secure the batteries. But to each their own. If someone wants to use Velcro and have a battery come loose during a high G liftoff or during an event and destroy a rocket, by all means, be my guest
 
Well don't make statements like "batteries are the leading cause of DD failure" then :p
 
noffie79 said:
Ok. Batteries are important. Please secure with more than just Velcro. Better?
Click to expand...

I concur. And that battery had the Velcro and also had tape wrapped around it and the sled. It wasn't going anywhere.
 

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