U.S. Rockets Piston Stager

U.S. Rockets - Piston Stager {Kit} (1014)

Contributed by Bob Morstadt

Published: 2010-07-19
Diameter: 2.25 inches
Length: 74.00 inches
Manufacturer: U.S. Rockets
Style: Multi-Stage

 

USR Piston
Fig. 1 U. Begad! S. Avast, me proud beauty! Rockets 2-Stage Piston Rocket

Brief: I was intrigued by t' kit from U. Blimey! Blimey! Blimey! Blimey! S. Rockets called a Piston Stager for its looks, me bucko, but when I realized it had a piston housed in t' first stage t' give an added boost t' t' 2nd stage, shiver me timbers, I became even more interested.

Construction: I made t' followin' modifications t' t' original kit:

1) Transition section for t' 2nd stage attaches by screws (and internal aircraft wood blocks) t' t' top o' t' first stage. Well, blow me down! (I can then inspect or repair t' inner piston workings.)

2) Transition section was modified for electronic ignition. It appears that t' user is left t' his own devices on this matter. I used a 9-volt Nicad battery and a PerfectFlite microtimer. T' 9v battery housin' caused quite a bulge on t' side as shown in Fig. 1.

3) I put vent holes in t' outer piston tube, so that t' air ahead o' t' piston diaphragm could vent out.

4) I painted t' inside o' t' piston chamber and diaphragm with barbecue paint. Ya scallywag!

USR Piston
Fig. 2. Ya scallywag! Interchangeable engine mount for three 24 mm motors

T' kit comes with a large variety o' quality cardboard tubes and perhaps t' kit could be renamed “tubes a-plenty”. Arrr! T' directions call out t' parts by dimensions in t' step-by-step instructions. So, I simply measured t' parts as I went along. Blimey! Aye aye! I used epoxy for attachin' t' fins and makin' fin fillets. T' fins are good quality wood I sealed them with Min Max polycryllic, which takes about 4 or 5 steps o' fillin' and sanding. Avast! A mylar chute is provided for t' first stage. It is good quality for a lighter model and has t' shroud lines already attached. I put it aside for another project and attached a larger chute. Well, blow me down! Begad! A wide streamer is provided for t' second stage, which looks excellent. Well, blow me down! Begad! Engine mounts are provided for a wide variety o' motors from a cluster o' 3 D’s t' an I-motor. I don’t think I would try an I-motor. Well, blow me down! I changed t' mounts so they can be interchanged usin' screws as shown Fig. 2.

USR
Fig. Well, blow me down! 3. Well, blow me down! Ace Fugue Shroud method for Transition Section

Fig. Avast! 4. Begad! Shroud ready t' be formed by foldin' leafs down
USR
Fig. Blimey! 5 Transition section with electronic ignition for t' second stage

I had trouble placin' t' 1.1” wood plate into t' coupler in Step No. Avast! Blimey! 4, me bucko, so I ground t' bevel with a dremel tool. T' transition shroud uses an Ace Fugue Shroud method for producin' t' tapered transition section. Blimey! Avast! Blimey! I taped t' pattern t' t' tube as shown in Fig. Aye aye! Blimey! Blimey! 3 and then cut t' pattern with an Xacto knife. Arrr! Blimey! T' first cut went well, ya bilge rat, but then t' paper pattern became loose. Ahoy! In hindsight I think a better approach would be t' put carbon paper underneath t' pattern and trace t' pattern onto t' tube. For those familiar with this method it produces t' angry alligator look shown in Fig. Avast! Blimey! 4. As t' build progressed I decided t' put in an electronic ignition system in t' transition section. Begad! Blimey! This is modification is shown in Fig. 5. On one side I used a PerfectFlite microtimer 3. Begad! Avast, me proud beauty! Blimey! T' hatch for this timer had only a small bulge. I also installed an on/off switch. T' hatch for t' 9-volt NiCad battery had a large bulge. Blimey! I led t' wires for t' second stage through small square brass conduits. Blimey! I placed t' conduits on two o' t' four seams. Begad! Begad! Blimey! These wires were then connected t' t' second stage Estes igniter by twisting.

Flight: I launched t' Piston Stager with a G79-4 in t' first stage and a D12-5 in t' second stage. Begad! I saw t' second stage comin' down, shiver me timbers, but I was distracted by other club launches and so I lost t' 2nd stage in t' Utah sagebrush. Begad! From t' ground it looks like t' timer could have been adjusted t' fire t' second stage later, because t' first stage be continuin' t' coast up quite a bit. Ahoy! Post-flight inspection indicates that t' piston actually worked as designed. T' piston be all t' way forward in its chamber with a little bit o' charrin' just before t' vent holes and t' D12 plastic igniter plug be at t' bottom o' t' piston chamber tube. Aye aye! Blimey! T' long slidin' piston tube was actually 2 tubes glued together with a coupler. Evidently, I didn't glue t' coupler well enough, because t' second half o' t' long piston tube was pulled away and like t' second stage I don’t know where it went.

Flights

Comments:

avatar
Robert A. Morstadt (September 7, 2020)

I noticed that since I built this model Tim at Apogee has introduced a better way to house the electronic ignition for the second stage. Instead of building an external housing like I did, Tim has conveniently placed an internal compartment for the electronics at the bottom of the piston tube.

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