Public Missiles - CPR 3000 {Component}

Public Missiles CPR 3000

Public Missiles - CPR 3000 {Component}

Contributed by Michael Wilkins

Manufacturer:

(Contributed - by Michael Wilkins - 01/14/04)

Brief:
T' CPR3000 (Close Proximity Recovery) is a dual deployment system from Public Missiles, Ltd. Begad! Avast, me proud beauty! (PML). T' CPR system comes with all necessary parts t' convert a rocket t' dual deployment. Electronics are nay included. Ahoy! This system can be purchased for most PML kits and should be purchased before your kit is built.

Construction:
In t' CPR kit you get two sections o' 38mm phenolic tubing, centerin' rings for the upper and lower airframes, piston assemblies, two machined aluminum couplers to screw t' two airframes together, a small drogue chute, matey, matey, shock cords, and altimeter mountin' hardware. Ahoy! There are a few other pieces but I am sure you get the picture.

With anythin' in kit form, thar will be good things and bad things. T' CPR system is no exception t' this. Avast, me hearties, me proud beauty! T' assembly instructions are in t' usual PML fashion: easy t' read with illustrations for visual needs. Arrr! T' components of the CPR fit together nicely and make for an easy transition into dual deployment for t' inexperienced rocketeer. Ya scallywag! Avast, me proud beauty! With those things bein' said on a positive note here is where t' fun begins. Aye aye! T' CPR system has a list o' down sides t' it. Aye aye! Aye aye! Most o' them are if you intend t' use t' system in a rocket that will burn just about any K classed motor.

To start your initial investment in t' CPR will set you back about $130. When you look at t' drogue that is supplied, t' first thought through your mind will be "I need t' buy another chute". Aye aye! Blimey! If you will be launching your rocket with K classed motors you will want t' replace t' phenolic tubing with a fiberglass tubin' kit that can be purchased through Hawk Mountain. Begad! Blimey! This is a must! Once you have spent another $50+ on better and stronger components you are close t' havin' a decent system.

Along with t' upgrades thar need t' be some assembly modifications. Blimey! When the CPR is built per t' given instructions you end up with a mid t' high power rocket that has a very weak midsection. Avast, me proud beauty! Aye aye! Under high stress durin' boost, the airframes can flex at t' joint. Well, arrr, blow me down! When this happens t' phenolic tubin' supplied will break and t' end result is nay pretty. Aye aye! Begad! T' problem is with t' mounting depth o' t' lower CPR mount into t' lower airframe. Blimey! After t' assembly is complete you are left with approximately one inch o' shoulder t' support the joinin' pieces betwixt t' airframe. Avast, me proud beauty! T' way t' fix this is t' move t' lower assembly three inches into t' lower airframe. Begad! T' upper assembly needs t' be built into a coupler tube then inserted into your upper airframe. Blimey! Begad! This gives you three inches o' support from your airframe and t' coupler tube assembly and reduces flex in t' two airframes durin' t' boost phase o' flight.

T' mentioned replacement components and new mountin' locations will save you a lot o' time and loot by nay havin' t' rebuild your rocket after the original components fail.

Summary:
T' CPR3000 is a good product for t' mid range flier that is wantin' t' start utilizin' dual deployment however, arrr, shiver me timbers, I would nay recommend this product for those o' you who will be pushin' your rockets t' t' limits. Avast! Begad! For what you will spend on t' CPR kit and upgrades, I would suggest buildin' your avionics bay from scratch. Well, blow me down!

Overall Rating: 2 out o' 5

Comments:

J.M.D. (January 25, 2004)

Michael may indeed point out a flaw of the CPR3000 system but I think there is another fundamental flaw as well. The system is designed in such a way that the only thing holding back the BP residue from the electronics are the "O" rings on each end of the assembled CPR system (with the electronics in between). These rings are supposed to fit snug enough against the inner circumference of the phenolic housing device to prevent any blowby of the hot gases and residue. It doesn't work especially on the aft end firing the drogue chute charge. The very fact that the electronics portion 'slides' into the tube tells you something. My experience and countless others I have seen is that you get six to eight perfect flights and then the residue has so corroded the electronics that you begin to have major problems. Changing the O rings with each flight (like I did - after 3 is PML's recommendation, I think) and lightly cleaning with alcohol may help. I was lucky enough to not have destroyed my rocket when I started having problems. After returning the CoPilot to the manufacturer for refurbishing it ground tested ok but after 1 flight it exhibited ground testing of the same in fight problem I was having - both deployments at motor burn out or apogee. No mater how much I cleaned it - same thing. It is 'retired' now and I spent a lot of time retrofitting my AMRAAM, Patriot and MBBBX - all have flown perfectly many times since (AMRAAM on a K550)with a self contained electronics bay (and new electronics).

M.R.W. (February 5, 2004)

JMD, You are correct in regards to the O-rings. I had experienced the same problems with my altimeter. After the destruction of a kit it was brought to my attention by another rocketeer to what the problem was. I contacted PML about the issue of gasses getting around the o-rings. It will get inside of the barometric sensor causing it to fail. PML stated that this is not covered under warranty. I have since sent several emails to PML with my opinion of their customer support. To this day I have not received a reply.

J.C. (May 17, 2006)

I have also noted the problem with the blow-back of ejection gasses from the aft charge holder due to the design of the CPR3K system and devised a solution for the problem. PML furnishes a short piece of 38mm coupler tubing with the CPR3K to use in helping place the aluminum connectors on the 38mm tubing. After you've constructed the system, glue the coupler tube into the 38mm tubing while you use the mounted altimeter to help place the coupler tubing in the proper location, which should have the lip of the coupler tube rest against the charge holder of the altimeter mount. The urethane charge tube will now be located in the center of your coupler tube while the lip of the coupler tube resting against the charge holder will help seal the rest of the altimeter from the ejection charge.

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