Insanity Plea: A sub minimum diameter M2245 project.

madcow rocketry
eggtimer rocketry
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
SUB-minimum diameter? That's awesome!

Composites are cool, but the aluminum will make this rocket really stand out.

Subscribed!

ChrisAttebery said:
There have been some major in the APE workshop over the last couple weeks. I was going to have a friend turn some parts for this project but it just felt wrong. I had a lathe a few years ago and sold it before I got back into rocketry. Ever since I got back in I've been kicking myself for selling it. So, instead of paying someone else to turn some parts I decided to buy another lathe. I had to move and redesign the enclosure for my CNC mill. I was able to open up a 7' length of the garage wall. I've been keeping my eyes open on Craigslist and on Saturday this lathe came up. It's a 13" x 40" gear head lathe. Besides the chinese branding it's identical to one that Birmingham sells now. It was pretty dirty but underneath the dirt was the original cosmoline grease. The seller bought it on a whim, didn't really use it much and really didn't know anything about it. I've spent about 6 hours cleaning it up and it's almost ready to move into position.

Stay tuned. I'll be back to making flying things soon.

View attachment 336822
Click to expand...

Maaannnn, I want one. :( It wouldn't fit in my apartment.
 
I’m finally getting back to this project. I ordered an M2245 reload from AMW last week. This weekend I made a 2.125 - 16 thread gauge. I’ll use it to check the fit of the threaded adapter from the forward closure to the nose cone coupler. IMG_5862.jpg
 
I'm finally working on this project again. I wound up having to put new bearings in my lathe but it made a huge improvement in the noise level and finishes I'm getting.

Over the last couple days I worked on a new forward closure for the Pro75 motor. I added a set of threads on the outside. I still need to finish the shock cord attachment but here's where it is at so far:

IMG_6075.jpg IMG_6076.jpg
 
Very nice Chris, I am keeping a look-out for a good deal on a used mini-lathe.

I bid on one at an auction last month but I got out bid. In hind sight there was still a lot of room to bid up, however when it comes to auctions I tend not to stay away from the "beat 'em at any cost" mentality and instead I take the "I will only buy it if I can steal it" approach.
 
This makes me want to learn how to thread. I've been working on lathes for ~15 years but the only threading I've ever done involved taps and dies.

Great work! What's the space with the reduced diameter for, weight savings? Seems like butting the coupler against the surface would be superior strength wise.
 
It just takes practice. I wound up making the closure 5 times and the adapter twice. I made a few mistakes and the machine had a couple problems. Each time it took a little less time and was a little less stressful.

The reduced diameter is just to reduce the weight. I tried to keep the wall thickness to .090" and I didn't see any reason to keep that mass there. The adapter will only be hand tight and the threads will take the majority of the load.

patelldp said:
This makes me want to learn how to thread. I've been working on lathes for ~15 years but the only threading I've ever done involved taps and dies.

Great work! What's the space with the reduced diameter for, weight savings? Seems like butting the coupler against the surface would be superior strength wise.
Click to expand...
 
I ordered a few things I needed for this project this week. I got a quart of Bonderite to prep the aluminum for epoxy. I ordered an RRC2+ from Missile Works for a backup altimeter. I ordered a set of 3/16" Kevlar shock cords from One Bad hawk. I also designed and ordered a fin guide wrap from Sticker Shock. The wrap will have cut outs that match the base of the fins. I'll apply the wrap to the motor case, sand the areas where the fins will be bonded, apply the Bonderite, rinse with water and then apply the fins with epoxy. A friend has some aerospace grade high temperature epoxy that made for aluminum to aluminum bonds.
 
I received the fin guides from Mark at StickerShock today. I managed to get the first one on straight and without any bubbles.

IMG_6183.jpg

First “Mach Up”
IMG_6175.jpg
 
The anodizing on these CTI cases is TOUGH. I started sanding with 60 grit sandpaper. After 20 minutes I still couldn't see bare metal. I decided to try my Dremel tool and a 1/2" sanding drum. It took a few minutes but I finally got down to the metal over 90% of the fin root area. 3 more to go.

IMG_6184.jpg
 
Nice design. Just a thought, did you ever think about leaving out the tracking smoke? You could probably save some weight if you left that out. I'm thinking a one piece flat faced fwd bulkhead and threaded ring with body adapter.
 
Yes, I thought about it. I decided to keep the motor internals stock and just tweak the hardware. The smoke may help reduce power off drag offsetting the weight penalty.

n3tjm said:
Nice design. Just a thought, did you ever think about leaving out the tracking smoke? You could probably save some weight if you left that out. I'm thinking a one piece flat faced fwd bulkhead and threaded ring with body adapter.
Click to expand...
 
I’ve been working on the recovery system over the last couple days. I received my shock cords and a Nomex blanket from Teddy at OneBadHawk Recovery. I made a pair of parachute sleeves from the Nomex using Fruity Chute’s design. They are 2.5” x 3” and 2.75” x 3.75”. I’m able to pack 9 yards of 3/16” Kevlar, the Nomex sleeves, a 12” drogue and a 48” Iris Ultra Light parachute into 4.75” of 3” coupler.

Here’s a picture of the 48” main packed into a 2.75” OD x 1.75” long puck. That’s a 1”x2”x3” block for scale.

IMG_6196.jpg
 

Similar threads

SteelyEyed
Project Aether Breather
2
Replies
34
Views
2K
Aeva
Aeva
Neutronium95
Bare Minimum: M2245 to 50,000 feet
2
Replies
58
Views
6K
311stylie
3
bandman444
Project Sasquatch (24" diameter Madcow Squat)
2
Replies
34
Views
3K
Rschub
Rschub
James Owen
“Risky Business” - Minimum Diameter mach 2 attempt
2
Replies
49
Views
4K
James Owen
James Owen
Kane
Design and Build Thread: ARO-B Two-Stage
Replies
22
Views
2K
Kane
Kane

Latest posts

Back
Top