PML AMRAAM 4" CPR build

[mtnmanak]

Just starting a new build of a PML AMRAAM 4" with their CPR 3000 kit. Looks like a pretty comprehensive kit:



Read through the instructions - very well written and thorough.

There are a lot of nylon straps that they tell you to glue together or tie. Planning to sew the straps together anywhere it calls for joining two portions of strap (i.e. - creating a loop). Their are only two centering rings on the 54mm "mother tube" for the Kwik Switch system. I plan to build the Kwik Switch as intended as I have not used that system from PML before and want to see how it works, but I plan to add a 3rd centering ring. I like to have a centering ring just fore of the fins.

The body tubes are all PML Quantum tubes. First time I have used their quantum tubes, so looking forward to trying them out.

Fins are G10, but very thin. They are just about 2mm thick. Compared to the 3mm fins I have in a couple of other kits, they seem quite flimsy. I was thinking of laminating the fins with CF. Anyone have experience with these fins and can opine on their durability?

 

[heada]

The kwik switch setup limits the length of motors you can use. You're much better off to build it as 54mm and use adapters like Aeropack to adapt down.

Also, some of the time they tell you to glue the nylon is to create an seal for the piston system. I would still use epoxy to seal the pistons.

The fins are thin but will withstand many flights unless you're going supersonic. I wouldn't laminate them with CF unless you're planning extreme flights and then using quantum tubing isn't recommended.

The altimeter that the original CPR system was designed around isn't available any more. Have you confirmed that you can get the correct electronics for the CPR3000 system?

I've built 2 of these and did my L1 with one with an AT I435.

 

[mtnmanak]

The kwik switch setup limits the length of motors you can use. You're much better off to build it as 54mm and use adapters like Aeropack to adapt down.

Also, some of the time they tell you to glue the nylon is to create an seal for the piston system. I would still use epoxy to seal the pistons.

The fins are thin but will withstand many flights unless you're going supersonic. I wouldn't laminate them with CF unless you're planning extreme flights and then using quantum tubing isn't recommended.

The altimeter that the original CPR system was designed around isn't available any more. Have you confirmed that you can get the correct electronics for the CPR3000 system?

I've built 2 of these and did my L1 with one with an AT I435.

Thanks for the suggestions!

I will make sure to epoxy the straps into the slots where indicated to seal them properly.

Great point on the Kwik Switch and understand the limitations. Now that I see how it works, I see how it limits the motor length. I am tempted to build this whole kit as intended, just to see how it functions, understanding the limitations it imposes.

Thanks for the recommendation on the fins, I will install them as is and see how they do - good to know you had a lot of durability with them.

The altimeter PML recommends right now is their CoPilot v3. It seems like a perfectly serviceable altimeter with decent functions, so I picked one up with the kit. I checked and it fits on the altimeter plate, no problem.

 

[Crazyrocket]

One other item you may want to consider is to put the piston in backwards with the bulkhead facing the ejection charge. When the charge goes off, the piston will tend to center itself in the tube. If it is put in the other way (typically as recommended by PML in their instructions), the charge will tend to cock the piston in the tube making it a little harder for it to come out. I have built them both ways and definitely like it backwards. You do need to make sure the inside of the body tube is kept clean or the piston will get stuck. Nice thing about QT is that you can wash it out with a hose!

 

[tsmmiller]

Great point on the Kwik Switch and understand the limitations. Now that I see how it works, I see how it limits the motor length. I am tempted to build this whole kit as intended, just to see how it functions, understanding the limitations it imposes.

I purchased my PML AMRAAM as a standard kit and then added the CPR3000 to it. A few changes I needed to do along the way vs building it from scratch as a CPR kit. I do have a build thread on it that follows most of what I did.
I will second the advice on the Kwik Switch.
I passed my Level 1 with the rocket as I built it, but following advice and some recommendations from the flying field I made some mods after, but have not yet flown.
I cut the top bulkhead out so longer motors can be used, and this one was the kicker, it also allows for motor back up at ejection.
I'll follow along and watch.

 

[mtnmanak]

One other item you may want to consider is to put the piston in backwards with the bulkhead facing the ejection charge. When the charge goes off, the piston will tend to center itself in the tube. If it is put in the other way (typically as recommended by PML in their instructions), the charge will tend to cock the piston in the tube making it a little harder for it to come out. I have built them both ways and definitely like it backwards. You do need to make sure the inside of the body tube is kept clean or the piston will get stuck. Nice thing about QT is that you can wash it out with a hose!

Great advice, will build it with the piston bulkhead facing the ejection charge.

Noted on keeping the tube clean. Is there any way to lubricate the tube prior to launch? Wouldn't think a liquid lubricant with be good, but maybe a dusting with baby powder or graphite powder?

 

[mtnmanak]

Got a bunch of the various inner sections glued up today, going to let these cure overnight (using Aeropoxy 6209).

 

[mtnmanak]

The kit came with these gigantic 1515 linear rail lugs. Instructions say to epoxy them to the fin section and the aft recovery section.

Anyone have any experience with these? I am going to at least add 1010 rail buttons to one of the other sides, but just epoxying the rail lugs to the surface of the tube seems a bit weak. I guess if I use them, I will plan out where they will go and put some plywood backing in the body tubes to have something to screw into.

 

[manixFan]

I built a fair number of PML kits when I first started, they were a great way to learn about HPR since the kits and instructions are so complete. Here's a few additional pointers:

• I know you've already started, but read through all the instructions and supplements before continuing if you haven't already
• definitely use rail buttons and screw them into a bulkhead or a small backer glued to a centering ring (you probably don't need the 1515 ones)
• using the Kwik-Switch does limit motors as explained, but it is pretty slick. I put Slim-Line retainers on the smaller ones which worked well
• test fit the smaller motor adapter tubes and mark the location of the rear centering ring to ensure proper alignment
• don't just glue the recovery harness to the piston bulkhead - either knot it or hand sew it into a loop
• if you fly in cold weather the piston will bind - the Quantum tube shrinks quite a bit; test fit by putting the tube into the refrigerator until it's cold and then check piston fit and sand if necessary
• use billiard chalk to dust the chute and inside of the tube as lubricant for the piston
• clean the inside of the tube and the outside of the piston after each flight of BP residue or it may bind
• scuff up the Quantum tube as explained in the PML materials - failure to do so can lead to part separation under load
• when you are glueing the CPR parts into place, cover the threads with masking tape, make sure to keep the tops of the centering rings clean, and double check the depths and centering of the parts
• I would suggest against the switch they include (or used to with the kits I had) and use a screw switch or other switch mounted to the altimeter sled
• plug the e-match wire holes in the CPR altimeter mounts with sticky-tack or clay to prevent ejection gases from getting into the A/V bay
• very lightly dust the inside of CPR tube to allow the o-rings on the CPR mounts to easily slide into the tube
• enjoy the smooth surface of the QT when it comes time to paint the rocket

I did my level 1 and level 2 on a PML Sudden Rush with CPR. As I mentioned above, the very complete kit and instructions really helped get me going in HPR.


Tony.

 

[heada]

Are they for 1515 or 1010? Mine came with 1/2" lug and lineral rail guides like that for 1010.

They work but I'd replace them with buttons. The problem is alignment between the rail guides has to be perfect or they'll bind. Also the aft one tends to chip and break so you have to replace it sooner.

I ended up cutting them in half and using them on light weight 2.6" rockets.

 

[mtnmanak]

I built a fair number of PML kits when I first started, they were a great way to learn about HPR since the kits and instructions are so complete. Here's a few additional pointers:

• I know you've already started, but read through all the instructions and supplements before continuing if you haven't already
• definitely use rail buttons and screw them into a bulkhead or a small backer glued to a centering ring (you probably don't need the 1515 ones)
• using the Kwik-Switch does limit motors as explained, but it is pretty slick. I put Slim-Line retainers on the smaller ones which worked well
• test fit the smaller motor adapter tubes and mark the location of the rear centering ring to ensure proper alignment
• don't just glue the recovery harness to the piston bulkhead - either knot it or hand sew it into a loop
• if you fly in cold weather the piston will bind - the Quantum tube shrinks quite a bit; test fit by putting the tube into the refrigerator until it's cold and then check piston fit and sand if necessary
• use billiard chalk to dust the chute and inside of the tube as lubricant for the piston
• clean the inside of the tube and the outside of the piston after each flight of BP residue or it may bind
• scuff up the Quantum tube as explained in the PML materials - failure to do so can lead to part separation under load
• when you are glueing the CPR parts into place, cover the threads with masking tape, make sure to keep the tops of the centering rings clean, and double check the depths and centering of the parts
• I would suggest against the switch they include (or used to with the kits I had) and use a screw switch or other switch mounted to the altimeter sled
• plug the e-match wire holes in the CPR altimeter mounts with sticky-tack or clay to prevent ejection gases from getting into the A/V bay
• very lightly dust the inside of CPR tube to allow the o-rings on the CPR mounts to easily slide into the tube
• enjoy the smooth surface of the QT when it comes time to paint the rocket

I did my level 1 and level 2 on a PML Sudden Rush with CPR. As I mentioned above, the very complete kit and instructions really helped get me going in HPR.


Tony.

Awesome suggestions, thanks!

Good point on the switch. I have a couple Schurter 110/220 rotary switches hanging around, planning to use one of those. Need to figure out placement and wiring before I get too far down the build.

Didn't know the Quantum tubes were so susceptible to cold - will definitely test them in the fridge since I plan to fly it this winter and it will def be cold.

Hadn't thought about billiard chalk either. When you refer to billiard chalk, do you mean the little blue cubes you use for the end of pool cue? Or does that chalk come in a powder form?

 

[mtnmanak]

Are they for 1515 or 1010? Mine came with 1/2" lug and lineral rail guides like that for 1010.

They work but I'd replace them with buttons. The problem is alignment between the rail guides has to be perfect or they'll bind. Also the aft one tends to chip and break so you have to replace it sooner.

I ended up cutting them in half and using them on light weight 2.6" rockets.

The ones that came with the kit are definitely 1515. In the pic below, that is a 1515 rail butting sitting on the rail lug and the lug is a solid 2mm wider than the 1515 button. I looked on the PML site and these appear to be the "Large Linear Rail Lugs". PML says they will work on 1515 and 1530 rails.

These are the only lugs the kit came with (no rail buttons or 1/2" lugs). Not a big deal, I have buckets of 1010 and 1515 buttons, I am just going to use the buttons I have for now and try these out later. Will probably try cutting them in half, as you suggest.

 

[tsmmiller]

I roughed up the surface of mine with 180 and glued down with JB Weld.
As others have mentioned they must be perfectly aligned.
I used an 8 ft piece of aluminum angle. (Very useful for later builds!)
At the launch site several mentioned just using one, cut in half, placing half one each section. The size of these lugs is really overkill.
As you mentioned defiantly place a backer of some sort for added strength if using a fastener.
(This I’ve done on my subsequent builds or build up an area of a centering ring to tap into.)

 

[Jim Hinton]

I've owned two of these, the second one is still a great flyer. The tricky bit on this kit is properly aligning the threaded couplers at the avbay. Pre mark your rail guide positions to make sure that the rail will clear the fins. Mounting of the rail guides can be a little tricky. One must mount them in a manner that they will not interfere with the recovery pistons. The rear guide is not really an issue, but the forward one is. I mounted mine just aft of the NC. That puts it close enough to the end of the airframe that any protrusions can be sanded flush with the id. Check the fit with the piston, of course.
This is a really awesome rocket, well worth any extra effort. I disposed of the kwik switch mount. Mine has a 54mm mount with Aero-Pack retainer. 38mm motors can be used with an Aero Pack adapter. I've never been tempted to fly this rocket on a 29mm motor. You will really enjoy this rocket.

Jim

 

[Hobie1dog]

and no stinking spirals to fill, great kit, keep the pictures coming for us.

 

[Hobie1dog]

Awesome suggestions, thanks!

Good point on the switch. I have a couple Schurter 110/220 rotary switches hanging around, planning to use one of those.

where do you get the switches that use a key?

 

[mtnmanak]

A lot of great points on the rail buttons/launch lugs positioning. As noted, the lower ones are easy. Going to put 1010 buttons, 1515 buttons and cut one of the 1515 rail lugs in half and install those too. I know it will create drag, but not going for altitude records here, just want rail versatility. Going to install the cut in half rail lugs because I want to try them, not out of necessity. For the upper buttons/lug, I am thinking about putting them in the middle of the canards through the coupler. That should keep them away from any pistons. Diagram below - the blue dots are where I am thinking about placing the rail buttons.

 

[mtnmanak]

where do you get the switches that use a key?

The switches I have are made by Schurter and you rotate the switch with a screwdriver. Very secure in that they stay in the position you place them in and have very little chance of switching off. Pic below. I can't remember where I got these - got them on a sale at some point in the past. It looks like Apogee sells them now, but there may be a cheaper source somewhere.

Been a while since I played with them, I need to do some testing to remember which posts to use and which ones to cut off.

Also need to think about where I am going to install these. They are much deeper than the slide switches, so will need to place carefully without interfering with the altimeter plate.

 

[mtnmanak]

I am going to build out all the sub-components today and get the canards and fins on (without the rear centering ring glued in) and then dry assemble everything tomorrow to determine best placement for all the electronics, rail buttons, etc. Will post some photos tonight once I get all the sub parts done.

 

[Joshua Smith]

The kit came with these gigantic 1515 linear rail lugs. Instructions say to epoxy them to the fin section and the aft recovery section.

Anyone have any experience with these? I am going to at least add 1010 rail buttons to one of the other sides, but just epoxying the rail lugs to the surface of the tube seems a bit weak. I guess if I use them, I will plan out where they will go and put some plywood backing in the body tubes to have something to screw into.

I had the same fear about the rail lugs (on a PML Striker), however I didn't change anything. It's flown once with no problem. I also have a PML Bull Puppy with the same lug. I can't really screw it in because it would interfere with the piston. I opted to use 2 screws that barely had any depth in the tube and they protruded just the slightest bit into the tube so I filed them down from the inside after the epoxy dried. I also chose to drill little divots in the area below where the lug meets the tube to give the epoxy even more to hold on to. Seems to have worked well, but haven't launched it yet

 

[Crazyrocket]

Noted on keeping the tube clean. Is there any way to lubricate the tube prior to launch? Wouldn't think a liquid lubricant with be good, but maybe a dusting with baby powder or graphite powder?

When I have built mine, I put the QT in the freezer to get it cold and then sanded the piston as necessary for a nice fit. This will prevent binding of the piston if you launch in colder weather. I have never lubricated with anything. I just made sure it was clean and that it slides into and out of the QT without sticking or binding.

 

[Nytrunner]

A word to think on before placing the forward rail button very far forward.
For the round buttons: once the forward button leaves the rail, the rocket is free to pivot around the rear button. This decreases your effective rail length to the distance between forward button and end of rail.
Straight rail guides are possibly better at the aft since they resist twisting slightly (Until they break anyway)

The key is making sure you have sufficient speed for stable flight once you no longer have rail guidance.

(I like to place the forward button between CG and CP)

 

[mtnmanak]

I had the same fear about the rail lugs (on a PML Striker), however I didn't change anything. It's flown once with no problem. I also have a PML Bull Puppy with the same lug. I can't really screw it in because it would interfere with the piston. I opted to use 2 screws that barely had any depth in the tube and they protruded just the slightest bit into the tube so I filed them down from the inside after the epoxy dried. I also chose to drill little divots in the area below where the lug meets the tube to give the epoxy even more to hold on to. Seems to have worked well, but haven't launched it yet

Thanks Josh, appreciate the feedback from someone who has used the lugs

 

[mtnmanak]

When I have built mine, I put the QT in the freezer to get it cold and then sanded the piston as necessary for a nice fit. This will prevent binding of the piston if you launch in colder weather. I have never lubricated with anything. I just made sure it was clean and that it slides into and out of the QT without sticking or binding.

Great idea, will do that, thanks

 

[mtnmanak]

A word to think on before placing the forward rail button very far forward.
For the round buttons: once the forward button leaves the rail, the rocket is free to pivot around the rear button. This decreases your effective rail length to the distance between forward button and end of rail.
Straight rail guides are possibly better at the aft since they resist twisting slightly (Until they break anyway)

The key is making sure you have sufficient speed for stable flight once you no longer have rail guidance.

(I like to place the forward button between CG and CP)

I agree that the high placement of the upper rail button decreases the amount of control on the rail. Once I dry assemble the whole rocket, I will have to look at where best to place the buttons based on not interfering with the pistons, but still near the CG.

 

[mtnmanak]

Canards are on and filleted - putting aside to cure overnight

 

[mtnmanak]

Motor tube is ready to install so I can get the fins in today

 

[mtnmanak]

While getting all the subcomponents ready to dry assemble to rocket, I installed the CoPilot 3 altimeter in the CPR3000 system. You attach the altimeter straight to the end caps, no plate. It works and is designed for this altimeter, but while I was fitting the pieces together, I realized you have to be really careful about twisting this assembly when you put it in / take it out of the altimeter tube. The o-rings are a tight fit and my first reaction was to twist the assembly to get it out of the altimeter tube, but I stopped when I realized the circuit board would take all the torque. It was easier to reach in from the other end of the body tube and push it out. Although, this altimeter it shorter than the altimeter tube, so the charge will go off in side the altimeter tube. Not sure how difficult that will make it later to remove the altimeter assembly when live charges have been used.

I do like that the altimeter comes with a slick battery retention bracket. Saves trying to figure out how to get a zip tie or something on there.

 

[heada]

Mine had the same config but with the CoPilot2. I dusted the o-rings with baby powder for them to slide in and out easier. They weren't under hardly any compression in mine so I wasn't worried about dust vs grease like you would in a motor.

I keep saying "had" or "was". Its a great rocket but I wouldn't recommend a J1999 in it. It didn't end well for mine. It underwent rapid disassembly at about 200' going near mach. I recovered a fin and the motor casing.

 

[Joshua Smith]

Mine had the same config but with the CoPilot2. I dusted the o-rings with baby powder for them to slide in and out easier. They weren't under hardly any compression in mine so I wasn't worried about dust vs grease like you would in a motor.

I keep saying "had" or "was". Its a great rocket but I wouldn't recommend a J1999 in it. It didn't end well for mine. It underwent rapid disassembly at about 200' going near mach. I recovered a fin and the motor casing.

Ouch. 1 fin is just adding insult to injury. Tho I guess that's balanced by you getting the motor casing back