Downscale Estes Magnum

Around 1992, I bought my second rocket, the Estes Magnum, #2032.
On it's maiden flight, it was sent up with a D12, a C6, and an “If found, please return to ….” note in the payload bay. I remember the first stage popping off and then the sustainer canting over to some non-vertical angle and vanishing. There may have been a glint of yellow as the huge 18" parachute deployed. As if on cue the wind picked up. I now think of the 1.5 hours after the launch as time well-spent with my father as we wandered aimlessly through a recently harvested corn field. Somehow we found both the booster and upper stage.


The magnum survived a number of other interesting launches. The failure to stage lawn dart. The failure to fully deploy the parachute core sample. Then there were multiple amazing vertical launches where I swore I’d never find it again.


Yet here it is, 23 years later, pretty beat up. (Yes, it's missing a fin). I really like this rocket, but it always made me nervous every time I launched it.





In addition to rehabbing the old rocket, I wanted to make a new version. I don't have access to large corn fields anymore, and I've never built anything that flies on mini engines. There was some extra BT-50 tubing laying around, so I thought why not make a down-scale I can fly in a small park?


Though, it does seem sacrilegious making a mini powered magnum.

I measured the fins and tubes on the original, then down-scaled everything by about 59%. I ended up using open rocket to play around with the design. I was trying to place a standard engine in the booster, but ultimately couldn't make it work out aesthetically. In the end, I settled for one mini engine staging to another.

View attachment bt50_magnum_mini.ork

And here are all the parts laid out, ready to go.



I'll update this whenever work allows me to make progress

op:

You have my interest. Looking forward to your updates.

I'm really interested too. The Magnum was my favorite. I'm currently going the other way with a Magnum rebuild--I'm keeping it original scale, but souping it up for 29 mm black power engines. Please keep us informed.

Thanks folks. I saw your post, BDB, and 29 mm in that thing is really going to be impressive.

Well, the simple engine mounts went together pretty quickly, and before I knew it I was gluing fins on.



And thankfully, after carefully taping the fin tips together, it seems after gluing the booster and sustainer fins still match up, so there's a success.




I had a question. In the past, I've had multi stage rockets eject the engine out of the booster (instead of decoupling the booster) subsequently allowing the upper stage engine to torch the booster. On this rocket, I have an extra 1/8 inch of engine tube protruding aft of the booster. My idea is to glue a thrust ring in the bottom of this engine tube to act as a positive stop for the spent booster engine.

My only concern is that this thrust ring will end up too close to the exhaust port of the mini engine and may also be burned.

Are there any opinions on this? The above incident only happened once for me, so maybe I'm overbuilding things here a little.

You may be over designing it, but it is always fun to be innovative. There isn't much risk here because, if it burns, you will likely only have to rebuild the booster.

In essence you need a motor retainer, like the ones that are used on MPR or HPR rockets. I don't think I've ever seen anything like that on a mini engine. Usually they just use an engine hook, but its a little too late for that now (plus, I've never seen one in a booster before).

So.....Maybe someone on the forum will have more experience with these smaller motors, but I vote for the thrust-ring-retainer-thing. It sounds interesting to me.

A thrust ring at the aft end of the booster has been an occasional design feature all the way back to (at least) the Estes Apogee II in the late 1960s. They used a skinny thrust ring (only 1/8 of an inch tall - EB-20B) but I expect even a regular one would be OK.

What he said. The thrust ring at the bottom of the booster insures that the booster engine casing takes the booster stage with it.

Great, thank you for the input - I'll keep the thrust ring.

I was able to get a bit of work done over the last week with regards to paint. I though I would try Rusto primer and just keep applying and sanding until the fin finish was smooth. I don't think I'll ever take this approach again. I'll stick to the Elmer's Fill and Finish, papering, or composite fins in the future, thank you.

I didn't get any photos of this repetitive process. Instead, here it is after a coat of white, silver, and Testors bright blue (thank you K'Tesh).



The next step is to make the nose cone shiny and blue:



And I've got to get a new payload bay, since the one I bought online was unexpectedly translucent red .

ama said:

Great, thank you for the input - I'll keep the thrust ring.

I was able to get a bit of work done over the last week with regards to paint. I though I would try Rusto primer and just keep applying and sanding until the fin finish was smooth. I don't think I'll ever take this approach again. I'll stick to the Elmer's Fill and Finish, papering, or composite fins in the future, thank you.

I didn't get any photos of this repetitive process. Instead, here it is after a coat of white, silver, and Testors bright blue (thank you K'Tesh).

View attachment 272101

The next step is to make the nose cone shiny and blue:

View attachment 272105

And I've got to get a new payload bay, since the one I bought online was unexpectedly translucent red .

Click to expand...

Can't help you with translucent red... Can help you with shiny and blue...

Well, I've been seeing Cabernut and BDB posting about the Magnum, and I felt like I should try to join the party.

Had a lot of changes with work recently which completely stopped my hobby efforts for the last several months, so the build has sat dormant. I finally got my act together a couple weeks ago.

I took K'tesh's advice with the nose cone:



Here was the initial CA and sharpie treatment. I later determined that I probably used too thick of a CA for this application.



And here it is after 400 grit sanding. I had never tried this method before (I previously used Elmers wood filler on a couple of nose cones...) and I have to say I really liked how it turned out in spite of using the wrong CA.



Here's a photo of the first coats of primer. It was at this time I received a new payload bay (via the Estes payload bay assortment). Next, spent some time shaping a BMS BT-50 nose block to try and match the original plastic one. The BT-50 ring was cut from some left over scrap.

For the nose block, I though I'd try something different and make a shock cord/parachute attachment with some kevlar I had on hand... in other words I was too lazy to drive to the hardware store for a screw eye. I started by drilling a large hole in the payload end, and two small holes on the opposite side.



Next, ran the kevlar through and tied a knot.



Finally, I took some thin CA and hardened the balsa and glued the ring.



Not sure if this will be durable long term.

Finally, got things painted, again with the bright blue.



And here's a shot of the final assembly.



There is a little orange peel going on which I'm going to try to buff out. May have been a little too cold at the time for painting.

ama said:

I took K'tesh's advice with the nose cone:

View attachment 276661

Here was the initial CA and sharpie treatment. I later determined that I probably used too thick of a CA for this application.

View attachment 276662

And here it is after 400 grit sanding. I had never tried this method before (I previously used Elmers wood filler on a couple of nose cones...) and I have to say I really liked how it turned out in spite of using the wrong CA.

View attachment 276663

Here's a photo of the first coats of primer. It was at this time I received a new payload bay (via the Estes payload bay assortment). Next, spent some time shaping a BMS BT-50 nose block to try and match the original plastic one. The BT-50 ring was cut from some left over scrap.

Click to expand...

The CA I recommend is the stuff that flows like water (actually, I think it's faster than water). Still, looks good! Glad you're doing the simulation of the plastic nose block with the scrap. I think when it's left off, the (full scale) rocket doesn't look quite right (it's a touch over 3/8" too short).

Yes, after the nose cone I did go out and get the very thin CA for the nose block. Sanding that part smooth was practically effortless. Will be doing this for all nose cones in future.

I recently got the decals applied. Here's the final result:



The blue doesn't quite match, but hey, it's is in line with the theme of the original:

Looks great!!! I'm looking forward to hearing how well it's first flight went.

Sorry about the Bright Blue difference. I should have prefaced that with the original (full scale) decals, and not any aftermarket decals. The problem you have there is one of the reasons I don't like trying to match blue decals. Unless you can find exactly what shade the manufacturer used (or the aftermarket decal supplier used), you've got the odd color change at the joint.

Three possible solutions...

1) Try purchasing every shade of blue you can find until you manage to match the decals (which is what I did to find the match to the original decal).

2) Find a shade that is somewhere between the decal and the bright blue, and then fade it as if the color change was deliberate

3) Get your decal supplier to provide you with decals of a known color value (such as I did... Thus the gloss black decals I bought).

Looks wonderful!

Going to give it a unique name like "Magnum Jr." or something?

It looks nice. I have a Magnum waiting to be built, and this is good inspiration to get it going. Great looking rocket.

Who did you use for the decals? They look great (even though they don't quite match the paint).

Cabernut said:

Going to give it a unique name like "Magnum Jr." or something?

Click to expand...

I think the "mini-mag" is taken already.

Rocket86 said:

It looks nice. I have a Magnum waiting to be built, and this is good inspiration to get it going. Great looking rocket.

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Thank you. The full size one is a great rocket.

BDB said:

Who did you use for the decals? They look great (even though they don't quite match the paint).

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I've ended up getting a lot of my project decals from Excelsior rocketry - he does a great job. Unfortunately, the BT-60 size decals seem to be out of stock: https://www.sandmandecals.com/product.php?id_product=747

K'Tesh said:

Sorry about the Bright Blue difference. I should have prefaced that with the original (full scale) decals, and not any aftermarket decals. The problem you have there is one of the reasons I don't like trying to match blue decals. Unless you can find exactly what shade the manufacturer used (or the aftermarket decal supplier used), you've got the odd color change at the joint.

Click to expand...

No need to say sorry - I kind of expected some difficulty matching the decals. One day I might get some tamiya yellow tape and try to paint the upper decal pattern, but for now I'll just fly it like it is.