New Member / Estes Doorknob Build / High Power Mods

The Rocketry Forum

Help Support The Rocketry Forum:

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
Hello Everyone,

I am a first year college STEM student and have seen many builds in the past but this will be my first attempt. I am working on modifying the Estes Doorknob to fly on an H motor in order to earn my Level 1 Cert. on Saturday 9/18 (included build pictures) it's still in the finishing stages.

I am super excited to be apart of the community!!
 

Attachments

Last edited:

Joshua Smith

kernelsmith
TRF Lifetime Supporter
TRF Supporter
Joined
Sep 6, 2019
Messages
217
Reaction score
126
Location
Austin
Hello Everyone,

I am a first year college STEM student and have seen many builds in the past but this will be my first attempt. I am working on modifying the Estes Doorknob to fly on an H motor in order to earn my Level 1 Cert. on Saturday 9/18 (included build pictures) it's still in the finishing stages.

I am super excited to be apart of the community!!
Is it just me or does the 2nd to last photo look like a weird fish...looking straight at ya?
 

Adam3836

Well-Known Member
TRF Supporter
Joined
Aug 10, 2019
Messages
721
Reaction score
772
Location
CT
Welcome aboard and good luck on the Level 1 flight
What motor did you decide on for your cert flight
 

Joshua Smith

kernelsmith
TRF Lifetime Supporter
TRF Supporter
Joined
Sep 6, 2019
Messages
217
Reaction score
126
Location
Austin
You can use that nose cone sled to also add variable weight to the nose, which u might need since ur flying on a heavyish motor
 

Joshua Smith

kernelsmith
TRF Lifetime Supporter
TRF Supporter
Joined
Sep 6, 2019
Messages
217
Reaction score
126
Location
Austin
More pictures.. Primed & waiting to be painted!!
I have a Doorknob w/Vanderburn upgrade (plywood fins and centering rings) that is on pause for two reasons and your pics reminded me of one. I also cut the bottom of the nosecone off but now the length of shoulder remaining is quite short. They say it should be about 1 body diameter, but if your cut is like mine, it's about 1/2 the body diameter now. I've been considering trying to glue the lower half back on (with reinforcement) after I add some variable weight to the nose, but I haven't settled on a system for that, which would still be adjustable after I put the shoulder back together. I also thought about attaching the original card stock centering rings on the bottom of the cut nosecone. That doesn't buy me a lot of length though and still makes any variable weight system difficult to manipulate. Now I'm contemplating some kind of wireframe-like nose extension. Kinda like this https://www.thingiverse.com/thing:47015 but made of something more like popsicle sticks/tongue depressors
 

Bat-mite

Rocketeer in MD
Joined
Dec 5, 2013
Messages
11,668
Reaction score
2,414
Location
Maryland
Welcome to the forum. You seem to have some skill, and I have no doubt you will get your L1.

My only suggestion, based on what I've seen, is for future builds, if you move on to bigger rockets and motors: stop using bent-wire eye-bolts, and use one-piece lifting or forged eye-bolts. A little over-energetic pull on the bent-wire eye-bolt can pull it apart just enough to allow the harness to slide off.

Rare, and probably not a concern for you right now. Just something to keep in mind.
 

Zeta

Well-Known Member
Joined
Sep 11, 2021
Messages
46
Reaction score
16
Hi Spacey,

I ran an open rocket sim on a doorknob with plywood fins and rings with a little nose weight :
1.14 caliber stability
19 oz with an Aerotech H165R loaded
82 MPH off the rod
536 MPH
36 G's yikes !
2108 feet apogee
(don't blink you'll miss it)

Can't wait to see the vid !

Zeta
 
Last edited:

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
I have a Doorknob w/Vanderburn upgrade (plywood fins and centering rings) that is on pause for two reasons and your pics reminded me of one. I also cut the bottom of the nosecone off but now the length of shoulder remaining is quite short. They say it should be about 1 body diameter, but if your cut is like mine, it's about 1/2 the body diameter now. I've been considering trying to glue the lower half back on (with reinforcement) after I add some variable weight to the nose, but I haven't settled on a system for that, which would still be adjustable after I put the shoulder back together. I also thought about attaching the original card stock centering rings on the bottom of the cut nosecone. That doesn't buy me a lot of length though and still makes any variable weight system difficult to manipulate. Now I'm contemplating some kind of wireframe-like nose extension. Kinda like this https://www.thingiverse.com/thing:47015 but made of something more like popsicle sticks/tongue depressors
You are absolutely right, After running the sim, I realized my nose cone is way to light. Need to add some type of variable weight to the nose cone due to the HPM. I was thinking derby weights?
 

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
Welcome to the forum. You seem to have some skill, and I have no doubt you will get your L1.

My only suggestion, based on what I've seen, is for future builds, if you move on to bigger rockets and motors: stop using bent-wire eye-bolts, and use one-piece lifting or forged eye-bolts. A little over-energetic pull on the bent-wire eye-bolt can pull it apart just enough to allow the harness to slide off.

Rare, and probably not a concern for you right now. Just something to keep in mind.
I was unable to find them @ HD, next build I'll have to order online. Thank you!!
 

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
That's a lot of negative gravity!
?? Would adding weight to the nose cone fix this, I plan on adding just trying to figure out the best way to do that. Was looking at Derby weights from the hobby shop but not 100% sure.
 

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
I finished the fillets last night, still need another coat of primer then paint but hoping to figure this stability issue out before the launch this Saturday AM! o_O
 

Attachments

tsmith1315

Well-Known Member
Joined
May 16, 2020
Messages
1,344
Reaction score
1,198
Location
Doerun, GA
You are absolutely right, After running the sim, I realized my nose cone is way to light. Need to add some type of variable weight to the nose cone due to the HPM. I was thinking derby weights?
A common way is to cast your own by mixing BB's, lead shot, fishing line weights, etc into epoxy. For a permanent weight, pour it where you want it. Cast it in slugs to stack in a tube, cylinders to slide into all-thread, dowel, smaller tube...
 

Joshua Smith

kernelsmith
TRF Lifetime Supporter
TRF Supporter
Joined
Sep 6, 2019
Messages
217
Reaction score
126
Location
Austin
?? Would adding weight to the nose cone fix this, I plan on adding just trying to figure out the best way to do that. Was looking at Derby weights from the hobby shop but not 100% sure.
A lot of folks do lead shot mixed with epoxy, but I personally never have any shot laying around. I tend to use nuts/bolts/large washers. You could scuff up some large washers and epoxy them to your nose cone e-bay sled. I would try to stay away from putting the weight at the tip of the nose cone (where you'd normally want to put it) because I think that would exacerbate your short nose cone shoulder. It'll make the nose cone want to pivot back and forth while it's seated in the tube if u know what I mean. If u keep the weight closer to the shoulder, you'll have less of an issue with that.

I you wanted to do something removable you just have to make it removable from the sled, so you could put a stubby bolt or two though the sled and put some washers and a locking but in the other side to hold it in place. Then u could change the number and size of the washers, nuts, bolts etc
 

Bat-mite

Rocketeer in MD
Joined
Dec 5, 2013
Messages
11,668
Reaction score
2,414
Location
Maryland
?? Would adding weight to the nose cone fix this, I plan on adding just trying to figure out the best way to do that. Was looking at Derby weights from the hobby shop but not 100% sure.
If your margin of stability is 1.14, then you don't need nose weight. But I would suggest a lower thrust motor. 36G might tear up a cardboard rocket. How about the H128W? Little longer burn, lower thrust, less G's pulled.
 

samb

Lifetime Member
Joined
Jan 22, 2009
Messages
4,145
Reaction score
561
Location
Plano, TX
Hello Spacey. I think you’ve set yourself quite a challenge for your first rocket. Your build photos look fine but flying and recovering one of these hotrodded Estes models might be a step too far. Are you still planning on going for it tomorrow ? Where are you flying ?
 

Zeta

Well-Known Member
Joined
Sep 11, 2021
Messages
46
Reaction score
16
You are absolutely right, After running the sim, I realized my nose cone is way to light. Need to add some type of variable weight to the nose cone due to the HPM. I was thinking derby weights?
I use stacked fender washers on a central eye bolt through the bulkhead.... there is a 2.75" that is space efficient for a 3 inch tube.
 

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
Hello Spacey. I think you’ve set yourself quite a challenge for your first rocket. Your build photos look fine but flying and recovering one of these hotrodded Estes models might be a step too far. Are you still planning on going for it tomorrow ? Where are you flying ?
I still hope to launch tomorrow at the SRA monthly launch. Ive equipped it with tracking on the nose cone sled, and deciding on maybe a smaller motor.
 

samb

Lifetime Member
Joined
Jan 22, 2009
Messages
4,145
Reaction score
561
Location
Plano, TX
Ok, good luck. Motor deploy of recovery device, right ? Not dual deploy or delayed deploy ? What’s the SRA field like ? Have you talked to those folks yet ?
 

Spacey

Member
Joined
Sep 15, 2021
Messages
17
Reaction score
18
Thank you! Yes, It is motor deploy recovery. I have never used their fields, but have spoken to them a couple times as far as their inventory and directions.
 

Latest posts

Top