3.72" Proteus Downscale

Document your build here! Big or small, simple or complex.
mdutch
Posts: 72
Joined: Mon Nov 09, 2015 4:01 pm

Re: 3.72" Proteus Downscale

Postby mdutch » Tue Nov 17, 2015 10:33 am

I have to admit that I like to extend the fin slots all the way to the end if just for the convenience of being able to build a strong fin to motor tube joint. Most will complain that makes the end of your tube weak but that is easily fixed by installing a coupler tube from the bottom of your last centering ring to the bottom of the airframe tube.
Good Luck with your build, Dan.
Mike Dutch
URRG & MRSI Founder
TAP L3CC
"I just want to fly ROCKETS"

SMS Engineering
Posts: 12
Joined: Wed Nov 18, 2015 11:51 am

Re: 3.72" Proteus Downscale

Postby SMS Engineering » Fri Nov 27, 2015 6:54 pm

Looks great so far Dan. How did you like the angle grinder trick for cutting the carbon? Other then a CNC mill , it's the easiest I've found . Mike sure did a nice job on those fins. What are you doing for a coupler?

Eric

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Sat Nov 28, 2015 3:13 pm

SMS Engineering wrote:Looks great so far Dan. How did you like the angle grinder trick for cutting the carbon? Other then a CNC mill , it's the easiest I've found . Mike sure did a nice job on those fins. What are you doing for a coupler?

Eric


Thanks Eric!

The angle grinder with a 1/16" cutoff wheel easily cut the carbon. It takes a few tries to get used to it (the HF grinder is pretty crappy ergonomically).

The coupler is Aerotech 98mm phenolic liner. It's a slightly sloppy fit in the tube, but a few wraps of masking tape or possibly a layer of 4oz satin weave glass will take care of that.

I managed to slot my tube today! Using a 1/8" end mill in my dad's Bridgeport mill we cut the slots with ease.

image.jpeg


Here's the rocket pieced together. The slots are a perfect fit for the fin material. Assembly begins tomorrow!

image.jpeg
Dan Patell
TRA 10904 L3

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Sun Nov 29, 2015 11:23 am

Epoxy has been mixed and this rocket is finally coming together!

First step is to epoxy the fore centering ring. I use 15 minute hobby epoxy for non-structural tacking. The fast cure time and medium viscosity makes it easy to use and plenty strong for this purpose. I have the Great Planes variety right now.

image.jpeg


Here's the tube and CR's. The CR's have tiny notches as a result of my mill slotting, annoying but won't have any negative effect.

image.jpeg


This is how I locate my CR's from the end of the motor mount. I slather epoxy on the tube, press the CR over the end, then press the CR between these washers until the tube bottoms out on the bench. This makes sure it's straight on the tube.

image.jpeg


Once the fore CR cured, I located the mid CR and epoxied it on.

image.jpeg


The last picture for now shows where the mid CR is with respect to the fore edge of the slot.

image.jpeg


Next step is to sand the ever living piss out of the motor mount, epoxy the mid-aft CR to the motor tube, drill some holes for some rail buttons, sand the ID of the booster tube, and the epoxy the motor assembly into the tube. This rocket will use friction fitting for the retention and the shock cord will be attached to the fore bulkhead of the motor.
Dan Patell
TRA 10904 L3

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Sun Nov 29, 2015 5:52 pm

As promised, some more work!

I drilled my rail button holes. These rail buttons are from AMW and have an elegant weld but attachment method. These require a bit of foresight when installing them in rockets where the CR web is less than the shank of the weld nut.

image.jpeg


With the rail button holes drilled it was time sand all future glue surfaces, clean the same surfaces with alcohol, and mix up a large batch of RocketPoxy. For this application, I added the black pigment provided with the epoxy so I can see where it winds up inside of the tube.

Step one is to use a dowel and apply epoxy inside of the tube about 3/8" aft of where the foremost CR's final resting place will be. Then I apply a massive fillet to the Fore-mid CR. The idea is that this fillet will settle once the motor mount is pushed into place and form a fillet between the body tube and the CR.

The motor mount was then quickly pushed into place, and actually a little beyond. I had to push it beyond to allow me clearance to push the aft rail button's weld nut into the tube. Once that was done, the motor mount was pushed to where it is supposed to be and left alone to cure.

Here's a pic of the mess that results. As you can see, there's a lot of epoxy in there. The majority of the strength will come from the fin bond to the motor mount and the body tube, so any adhesion achieved here is gravy!

image.jpeg
Dan Patell
TRA 10904 L3

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Tue Dec 01, 2015 12:52 pm

Time to get some fins on this rocket! But first, I epoxied the aft-most centering right into the rocket. This really makes for a tough tail end for the rocket and allows me to coat with epoxy, fill, sand, and paint the aft of the rocket to match the rest of it! I also drilled some holes on either side of the slot for epoxy injection.

IMG_3168.JPG


Step one is something you've all seen/done before...apply some 15 minute epoxy to the root (and sides of the root) and tack the fins to the motor mount. Applying some epoxy to the sides of the root also tacks the fins to the body tube at the slot edges as well.

IMG_3173.JPG


Once the fins were tacked and the internal fillets injected, I taped off for the external RocketPoxy fillets:

IMG_3174.JPG


Laid down my fillets (with a 0.875" diameter tool), leveled:

IMG_3175.JPG


...and now we wait for this to cure!

IMG_3176.JPG
Dan Patell
TRA 10904 L3

FMarvinS
Posts: 9
Joined: Tue Nov 17, 2015 11:24 am

Re: 3.72" Proteus Downscale

Postby FMarvinS » Wed Dec 09, 2015 5:13 pm

Hi Dan,

I'm thoroughly enjoying your build thread. I'm curious, why did you decide not to extend the fin slots fully aft which would have been an easier path? The only recommendation is to "speed up" your posting of progression in your build (LOL)!

Regards,
Fred

dixontj
Posts: 18
Joined: Thu Nov 19, 2015 9:21 am

Re: 3.72" Proteus Downscale

Postby dixontj » Wed Dec 09, 2015 9:11 pm

FMarvinS wrote:Hi Dan,

I'm thoroughly enjoying your build thread. I'm curious, why did you decide not to extend the fin slots fully aft which would have been an easier path? The only recommendation is to "speed up" your posting of progression in your build (LOL)!

Regards,
Fred


+1. Nice build.

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Thu Dec 10, 2015 8:29 am

Thanks guys! It's been a little slow coming recently, just whittled out these 5" motor components for a "customer."

5in Components - 1.jpg


I'm also awaiting a nosecone from a buddy. The goal is to employ a 4" FWFG cone that will be modified in my lathe to better fit my purpose. This will require chopping it down to match my diameter, then making a custom adapter piece to mate it to my shoulder/coupler. Should be cool when it's done!

Stay tuned, and please feel free to post your own projects!
Dan Patell
TRA 10904 L3

User avatar
patelldp
Posts: 160
Joined: Thu Nov 05, 2015 5:07 pm
Location: New York

Re: 3.72" Proteus Downscale

Postby patelldp » Sat Jan 02, 2016 7:51 pm

Still here!

Next up is the nosecone. The shoulder is made from the aforementioned (I think) 98mm liner from Aerotech (thanks Griffin!). I added a layer of 4oz satin weave glass to clean up the slop...lo-and-behold it's a perfect slip fit now!

I then acquired a damaged 98mm nosecone from a friend. This was clipped such that the remaining cone was a smidgen over 3.72".

image.jpeg


Next step was the taper on the nose shoulder. Some quick trigonometry resulted in a 4.4 degree cone, so that was cut into the shoulder so the coupler and the cone will lock together.

image.jpeg


Now that they fit snugly because the taper, I epoxied the shoulder into the cone using RocketPoxy and my lathe to compress them tightly together.

image.jpeg


Here's the cone on the bottom half of my Proteus downscale. Looks good from here! I'm going to utilize my cable cutter to fly the rocket in this configuration at some point.

image-2.jpeg
Dan Patell
TRA 10904 L3


Return to “Build Threads”

Who is online

Users browsing this forum: No registered users and 2 guests