Newbie with a Small Endeavour

New guy with questions...consider yourself warned.

Hi guys! I'm a BAR that's been back into it for about two years now, and a member of QUARK, getting into mid power (initiator, mustang, upgraded a prowler to composite 24mm, as I did with my Executioner and Phoenix). For my birthday, I got a Tiny Pterodactyl and a Small Endeavour (quantum tube version). I'm using the SE for my level one attempt this summer (knowing that political stuff and things will work out in our favor...I'm an optimist, too...). My question is, on both PML kits I have, I can't find T-nuts with a small enough base to fit the CR. I also wanna put rail buttons on the SE, but am not sure how to do that and not intefere with the piston. Suggestions?

Mark

Originally posted by Loopy
New guy with questions...consider yourself warned.

Hi guys! I'm a BAR that's been back into it for about two years now, and a member of QUARK, getting into mid power (initiator, mustang, upgraded a prowler to composite 24mm, as I did with my Executioner and Phoenix). For my birthday, I got a Tiny Pterodactyl and a Small Endeavour (quantum tube version). I'm using the SE for my level one attempt this summer (knowing that political stuff and things will work out in our favor...I'm an optimist, too...). My question is, on both PML kits I have, I can't find T-nuts with a small enough base to fit the CR. I also wanna put rail buttons on the SE, but am not sure how to do that and not intefere with the piston. Suggestions?

Mark

Click to expand...

Welcome back to the fold Loopy!

You should be happy with the Small Endeavour. It's a great flier. Instead of T-Nuts, try threaded inserts. They don't have the lip that's on a T-nut. On the rail buttons, mount the top one just below the top CR and the lower one just above the lower CR. Having them adjacent to the CRs help support the screw. You can see reviews of the SE (including mine) on EMRR

Good luck!

Hi Loopy!

Welcome to the rocketry forum.

For motor retention on smaller rockets what I do is to install "studs" instead of blind nuts. Take a couple of 4" lengths of light "all thread" rod, say #6-32 or #8-32, and glue them on opposite sides of the motor mount tube (MMT) so that they extend about 3/4" behind the MMT. You'll have to notch out the rear centering ring so it will slide over the threaded rod but otherwise you just assemble the rocket normally.

When the rocket is complete take a cresent wrench or pair of pliers and bend the threaded rod out slightly, about 1/16" will do, so that you have clearance for the thrust ring on reloadable motors. Now you can load a motor, either a reloadable or a single use with a masking tape thrust ring, and anchor it by running two nuts down the threaded rods so that they come up against the rear of the motor. Wing nuts work best but any kind will do.

With regard to the rail buttons you either need to install the forward button behind the piston or you need to eliminate the piston completely. An alternate would be the ACME Railguides that glue onto the outside of the airframe. I've used these with great success by installing them with JB Weld after really roughing up the surface of the airframe and the bottom of the railguide. Also with the Tiny Pteradactyl you might need only one quide installed at the center of gravity like a single launch lug on an Estes size kit.

Ken Holloway, NAR #78336, L-1

Loopy ,

A BIG welcome back to ya...I am trying to remember if we have met yet as I am a member of the Quarks and perform the majority of Cert's there. If not, I hope to meet and certify you sometime this summer!

As far as the Small Endeavour goes, it is a great rocket!!! I actually have one and it flies very well. Dick's suggestion of using the brass inserts is a good one and that is what PML uses for their PMR retainer. If you dont have the model built yet, you can use T nuts in 6/32 size and shave off one third if needed, which would be the side near the motor mount, so they will fit. I recommend you use three; that way if one comes loose, you still have two holding in the motor.

Regarding Rail Buttons, if your model is not yet built, glue a piece of wood block near the bottom for the lower rail button, or double up the thickness of the CR so you get good bite with a wood screw. Use a wood screw to mount the bottom button and a bolt with nut and washer works for the upper button. Mine is set up so the piston bottom lip rests on the "nut" for the button...this causes absolutely no problems.

Good luck and keep us posted...oh yea, pics...lots of pics please!!!

Carl

Carl,

I'm the guy with the red minivan and the two young kids that was there from spring through fall. Actually, if you're going to the build and fly tonight, I'm hoping to be there too if I can get directions. Anyway - thanks for your help everyone!

Mark

I've been looking for brass inserts, but can't seem to find them anywhere. Suggestions?

Mark

Lowes has em in their specialty hardware drawers...6-32 all the way to 3/8"...

Carl

I used rail buttons from https://www.railbuttons.com/rb for my Public Missiles Limited (PML) Tiny Pterodactyl. As indicated in the EMRR review of this rocket kit, you can use rail buttons in this rather small HPR kit and still have a piston ejection system. After I roughed up two 3/8"-diameter spots on the PML Quantum airframe with 120-grit sandpaper, I drilled two 1/8"-diameter holes 1/2" and 7-1/4" from the bottom of the body tube. The fine threads on the rail button screw goes nicely into the Quantum material, and the epoxy keeps it in place. You don't need blind T-nuts for this small rocket.

I was able to upsize my 18"-dia. PML parachute to a 24" size and use a PML Intellicone for my PICO Altimeter -- and there's still enough room left over for the piston in the body tube.

I've heard alot of talk about pressure relief holes in this forum. Do I need one in my Small Endeavour? If so, how big, and should it be right below the nose cone?

Loopy

On my Tiny Ptero, I used #8-32 T-nuts. I made room by cutting one side off of the T with a dremel. I also installed rail buttons from railbuttons.com. One at the aft CR, and the other about 6 3/4 inches from the aft end. This still left room for the piston, and chute.

David

On pp. 181-182 of Mark Canepa's excellent reference, "Modern High-Power Rocketry -- An Illustrated How-To Guide," there's extensive discussion about the appropriate size of air vent holes. It says:

"How large do the air vent holes need to be? Some have suggested that a single, one-quarter-inch hole is sufficient in most rockets with diameters of average size, while rockets with diameters of seven inches or more might require several vent holes of similar size."

When you drill your single 1/4"-dia. hole for the PML Small Endeavor, make sure that the nosecone doesn't cover up the hole. Put the hole near the top of the body tube, so that the piston still has enough gas pressure to push the parachute out.

Also, if you plan on flying this rocket REALLY fast (e.g. Mach 0.85+ with high acceleration), you may wish to drill a small (~1/8") hole behind the piston as well. I have an extremely vivid image in my mind of one event I saw happen when a certain rocketeer forgot to do this (don't worry, Erik, I won't tell anyone that it was one of the Gates Brothers ). Anyways, this nameless person E.G. put a K1050 in his modified PML Nimbus, and off it went.

It was MOVING when at Max-Q the rocket shredded. The piston had been vented on the top but not the bottom. Since there was higher pressure below the piston than above the piston, it rode up the tube (pressures trying to equalize). It shoved up the tube faster than the air pressure could vent out the upper vent hole, and off came the nose cone at 900 MPH.

I don't think that a Small Endeavour should have this problem due to its relatively low impulse-to-weight ratio, but it's something to keep in mind as projects grow inevitably bigger.

Gee, I can never seem to type a short post.

Thanks guys! I don't see my Small Endeavour going quite that fast, but thanks for the future considerations!

Loopy

That's really interesting about the vent holes. I plan to build a Mini-BBX and will eventually stage it to the Terrier booster. Guess I should keep that in mind.