Anybody tried to convert a rocket from a 54mm motor mount to a 76mm after
the rocket is built?
I built my PML Ultimate Endeavor intending to use it for my Level 2 last
year but ended up using a smaller rocket with a J350 based on motor
availability. Now I am mostly just flying sugar motors (a lot cheaper for
certain!) but my AMW 54mm casing will only get me up to a full "J" motor
with sugar. I am building some 76mm hardware and would like to reconfigure
the rocket to a 76mm mount. The endeavor has two sets of fins at the bottom
and they are quite large. Looks like a lot of tricky dremel work to me! Not
too mention the 3 half inch thick centering rings already installed.
Anybody do this kind of operation before? Any tips? Should I bother?
I haven't tried it but, I've thought about it on occasion. As I see
it, the difficulty would be getting the new motor mount attached
squarely & rigidly to the rest of the airframe. I was thinking about
something like a drillbit the size of the od of your new motor mount
that has maybe 2 or 3 inches turned down to 38mm.
If you come up with a good way to do it, I'd like to know.
On Fri, 25 Jul 2003 20:51:42 -0700, "Stuart Leslie"
You could easily build another bottom half for about $140.00.
get the phenolic tubing (MMT and Body) & centering rings from Red Arrow.
Order U. Endeavour fins from PML... Make sure they cut em for 75mm fin tab
and not 54.
Or rip the fins out cut em down to 75mm fin tab and just get new tubes and
CR's for $55.
Slot and cut your own tube.
Thanks for a bunch of great suggestions, my strange rocket logic goes like
I have this spankling clean, beautiful two tone paint job with future finish
on the rocket now that I spent a lot of time sanding/painting to achieve. I
don't think I could "rip the fins out" without great emotional stress! Same
goes for making a new bottom section as this is where most of the work went.
I do like the suggestion to go for the 98mm while I am at it though, never
know where future motors will go to! As to lengthening the 54mm with custom
hardware, This still does not let me get very far into the "K" range without
erosive burning concerns. The wider diameter motor also lets me get longer
burn times (2.5 seconds is long in the world of sugar motors!)
This leaves me with the challenge of having to cut out 3 centering rings,
cut out 54mm mmt and three 38mm motor mounts, as well as trim about 1/2 inch
off each of 6 fins. Trimming the fins is the part I can't really figure out.
A hack job would likely result in fins that don't bond to well to the new
motor mount. Can't fit a dremel into the long tube to reach the fins so I
don't know how I will trim them. Also will have to figure out how to fit the
center centering ring in without compromising the ability to apply the
internal fillets on all the fins.
I know it is crazy but somehow spending hours retrofitting my existing
rocket "makes more sense" than just starting with a new rocket. I will fire
up the dremel today and just dive in I guess. My initial plan is to fasten a
steel straight edge to each internal fin tab, then drum sand the tabs to the
straight edge at the correct depth. Wish I could fit the dremel in to use
the cutoff wheel but I don't think that is going to work. The middle
centering ring will likely have to be cut into thirds and inserted once the
fins are nicely secured to the motor mount.
I will take pictures and post the results on my web page
(http://home.mindspring.com/~sleslie/index.html ) if anyone is interested.
Thanks again for the suggestions.
Someone said about getitng the MMT alined. Fit a CR at one end. Smeaer epoxy
where it will stick in the bt say above the fins. Feed this down from the the
front of the body and then smear epoxy n the other inside part of the bt and
MMT and fit one more cr. Then do the tape thing that pml does and jsut slide
one more cr on. leave to set and in theroy it might work. i guese ou could foam
the can by drilling some holes and pooring it in and then a bit of 5 min epoxy
when it's in the gels stage to fill the hole.
I know not great woridng but you might get the idea.
Wow! That's a great idea! I was just about to start dremeling when I saw
your post. This looks like the best way to go so I will give it a shot.
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