[NRVR-Members] Meeting with NRVR

Thomas (Tweeks) Weeks tweeks at rackspace.com
Mon Dec 7 13:44:55 CST 2015

[CCing the nrvr-members mail list so this will be archived]

Wow.. if large autonomous roverer/rocket design is going to be at the meeting, that would rock! (but also really suck bc I'm going to miss the meeting. I'm a huge arduino geek and would LOVE to see an autonomous arduino-rover pop out of a big bird! [😊]  ) Here's one of my little arduino bots I was thinking about popping out of my next big rocket (currently seeking a nice big fat rocket for this):


I'm eager to hear what Bob has to say about 1inch standoffs, but I've done some 3/4" standoffs for rail buttons on one of my fat-nose rocket designs. It can be done very robustly if you do it right.

But you're rocket is going to be pretty heavy it sounds.. so before showing how it should be done there's a common way you should probably AVOID doing it.  Below is the common way to make rail-botton standoffs for smaller/lighter large nose rockets (which you probably want to avoid):


It looks nice, but taking that design out to 1" would give you too much button torque on a large heavy bird. Plus the screw/epoxy nipple inside your BT (body tube) will create a snag point for any recovery gear/chutes. But the torque from the 1inch of clearance is the real problem with a rocket as heavy as yours.

Instead, here's a graphical view of how I did it (on this smaller 2.6" rocket design) using streamlined basswood blocks and T-nuts creating a much wider "hugging footprint" to the standoff (VERY solid):



The block is sanded to fit the tube by simply putting the sandpaper (rough side up) and sanding the button-block directly against the BT.. creating a perfect fit to hug your BT and give you a solid anchor.

This design yields MUCH more lateral rocking resistance (than a simple, columnar plastic standoff).  If interested, I have some more pics of this design at home I can put on my webserver tonight.. I did a longer 3inch block standoff like this that will give you room for both outward and inward facing T-nuts. Tricky getting it all screwed down without any snag-points, but VERY solid, and you end up with nuts and bolts anchoring the button base to the BT, (not just some epoxy or a 1inch plastic cylinder).

For an even more solid anchor, you could also go with a larger triangular block base with three outward facing threads (t-nut style) with flush-nut-head inside and screw bolts from the outside with an internal re-inforcing ring (fiberglass or aluminum ring) that the internal flush-nut mount the block to to give it a super solid mount point.  Email me off list and I'll get you the other design photos.

If this is your first HP rocket.. I would recommend comparing deisng notes by the experienced experts in the nrvr.org mail list (CCd).  If you're not a member, students can join for free here http://nrvr.org/membership/.

However, to beef up on HP rocket design best practices I recommend picking up a copy of this excellent HP rocket design book that has decades of big-rocket design wisdom:

Any of you other guys have feedback?

Bob? You done any heavy rocket button standoffs?

p.s. Fareez.. with a rocket this big/heavy.. you ARE using the larger 1515 buttons right? http://aeroconsystems.com/cart/launch-and-recovery-accessories/rail-button-8020-style-1515-pair/  (unless Bob recommends something beefier)

From: Fareez Chowdhury <fareez.chowdhury at gmail.com>
Sent: Monday, December 7, 2015 1:17 PM
To: Bob Schoner
Cc: Kevin Shinpaugh; james desposito; Jim Farley; Jordan Truesdell; Carlos Zapata; officers at nrvr.org Officers; Pat Artis; Brad Smith; Eric Plevy; Magda Moses; Johnny Jaffee; Ishan Arora
Subject: Re: Meeting with NRVR

Mr. Schoner,

Any and all advice would be appreciated. I've CC'd the remainder of the team so they can be in on this. In case anyone is curious, I am also attaching the PDR we've submitted to the competition organizers and for which we'll present on Wednesday morning, as well as the OpenRocket file we've got going on right now.

An additional question would probably be: how would you recommend going about building a 1" standoff for railbuttons? If you'll see from our rocket file (and alluded to in one of the other questions), our rocket has two diameters, and the lower stage is of smaller diameter than the upper. Since it is not possible to mount the rail buttons on the upper section due to payload reasons, we need to build standoffs for our railbuttons so the buttons (attached to the smaller diameter tube) can reach past the larger diameter upper stage and connect to the rails. What kind of shape/material/size would those stand-offs be, etc.?

On Mon, Dec 7, 2015 at 9:16 AM, Bob Schoner <bob.schoner at gmail.com<mailto:bob.schoner at gmail.com>> wrote:

Lets's put this on our calendar and move forward with it.  I will update the calendar on our webpage.


We still have interested VT students that we can help out.  These are some great questions and are always preferred over assumptions when folks are getting into high power rocketry.  I don't mind addressing one or two of these, but would like more people to help out and add their perspective too.

I feel like I can offer something on any of these and will volunteer to speak on #2.

Officers and NRVR members, please reply all to:
 - indicate if you can make this meeting for 12/9 at 6:00 p.m.
 - indicate which topic you want to address or research

We can certainly invite all our members as this may be of interest to them.  I know December is busy and we are not giving them too much notice.  Any objections to open this up to the whole NRVR community?

I'm inviting the L1 and L22 people that I can remember.  Think back to some of the assumptions you made when you first started and see if you have some advice on any of these topics.

Since Time is short, please reply no later than 11:00 pm of 12/7.



On Sun, Dec 6, 2015 at 4:03 PM, Kevin Shinpaugh <kashin at vbi.vt.edu<mailto:kashin at vbi.vt.edu>> wrote:
I think we can get an NRVR meeting with you all for after 6pm on Thursday.
Space at VT will be a good meeting location.

On Dec 6, 2015, at 3:16 PM, Fareez Chowdhury <fareez.chowdhury at gmail.com<mailto:fareez.chowdhury at gmail.com>> wrote:

Dr. Shinpaugh,

At the last meeting, you wanted us to remind you to ask NRVR if we can schedule a meeting at Space at VT on Thursday (12/10) at 5:00 PM, to discuss some rocket concepts and verify some things you guys are doing. We also have a preliminary list of questions we wanted to ask:

  1.  Advice for cutting accurate fin slots
  2.  Filleting fins to body tube at root
  3.  How to prevent parachute tangling at apogee (booster main chute and capsule drogue chute)
  4.  Adding a shoulder to a modified LOC PNC 7.51 in nosecone to convert it into a 7.51 in to 5.51 in transition piece
  5.  Advice on parachute deployment bag selection for capsule main chute
  6.  Amount of black powder and Pyrodex required for recovery

Please let us know as soon as possible. Thanks!
Fareez Chowdhury
Mechanical Engineering
Virginia Tech, Class of 2017

Fareez Chowdhury
Mechanical Engineering
Virginia Tech, Class of 2017
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