MMX Launch Rack

[JAL3]

I tried several different methods of cutting the brass along the lines, mostly involving a Dremmel cutoff wheel with poor accuracy results. I then found to my surprise that kitchen shears worked better than anything else as long as SHE WHO MUST BE OBEYED did not catch me using them.

 

[JAL3]

The brass blank with template affixed was then set on a piece of scrap (an old head prototype) and a Dremmel drill press was used to pierce the three holes in the electrode. I should mention here that two of the hole were for mounting and the bottom hole is to give the igniter clips a better grip for connecting.

 

[JAL3]

With the piece drilled, some needle nose pliers were used to bend some contacts for the top surface of the electrodes. I learned that the brass was too soft to want to bend nicely along the marked lines.

 

[JAL3]

The electrode was then mounted onto the head with some #4 brass screws and nuts. Several things became immediately apparent. My drilling of the holes with a hand drill had been sloppy and the mounting holes were not in line; the flexing of the drill bit I had noticed in the press was enough to throw things off; and it looked like I was going to have to start again.

 

[JAL3]

After apologizing to the cat for my string of expressions learned in the USN, I tried another blank and got about the same results. This time I noticed that the bit had slipped and flexed even more than before. With my club launch fast approaching and the promised debut of this thing, I had to make some concessions.

I gave up the idea of the bent contacts for the original MMX style igniter (at least temporarily) and cut the electrode blanks to be a bit narrower. I still had some slippage problem with the press but it was less severe when I used some pliers to try to take all of the bends out of the blank. After a bit, a pair of serviceable electrodes were cut and affixed to the head.

 

[JAL3]

A little messing around showed that I had something that, while not yet perfect, was serviceable and seemed likely to be better than what I had before.

 

[JAL3]

In the meantime, the base and box were undergoing their final steps. I masked off the head supports and the fastening screws with masking tape in preparation for the final painting.

 

[JAL3]

The box was then sprayed with 2 coats of yellow Krylon. This was a paint that I got in an auto shop and is supposed to be very hard. It also dried very fast.

 

[JAL3]

The next day I gave the box another 2 coats of yellow to improve the quality of the coverage; that gray primer was hard to cover. I probably would have given it another coat but I ran out of paint. The base and support seemed to be done at this point.

 

[JAL3]

I was in the home stretch now. I cut out a big stack of electrode blanks and drilled them out. They were then mounted to the heads and I had some spare left over just in case.

 

[JAL3]

With that, I had 9 heads ready to go. I had planned for 10 but one of them disappeared someplace along the way. All that was left was the launch rods and to fit things together.

 

[JAL3]

The rods were fabricated from 0.047 music wire. I cut the 36" pieces in half to give 18" segments. The rods were bent at a right angle 1.5" from the bottom giving that much length to fit into the receiver.

 

[JAL3]

1.25" farther along, the rods were bent back to vertical. This gave a straight shot over the igniter slot

 

[JAL3]

Things seemed to line up right and I was feeling pretty pleased with myself. The rest of the rods were then bent into shape.

 

[JAL3]

Lucky for me, I had an MMX Vulcan sitting handy and was able to put it on and see how things lined up. It did fine!

 

[JAL3]

It looks like I never uploaded the PDF for the electrodes so here it is.

View attachment mmx electrode.pdf

 

[JAL3]

I was looking forward to trying out the new rack at my next club launch but rain made our field unusable. I used the sunny day to try fitting the heads to the rack and see how it went.

The first step of the mounting was to remove the winguts from the head mounting posts.

 

[JAL3]

The heads were then slid onto the bolts and secured with the washers and wingnuts.

 

[JAL3]

To get the full effect, I mounted the launch rods. Each seemed to have the proper reach.

 

[JAL3]

The system was designed so that it could be opened in the field if needed to retrieve extra parts.

 

[JAL3]

That means it also stores the rods and heads when I started to break it down. It was ready for the field test.

 

[kullas]

I like the storage very nice setup ya got there

 

[Micromeister]

Very Nice looking Micro Rack system John:
I Hope you'll keep us informed of the contact reliability of your micro open slot connectors. I feel your gonna have a crud build-up problem on damp and/or humid days. Hope I'm wrong, I'll be very interested to hear how it works out.

 

[JAL3]

Very Nice looking Micro Rack system John:
I Hope you'll keep us informed of the contact reliability of your micro open slot connectors. I feel your gonna have a crud build-up problem on damp and/or humid days. Hope I'm wrong, I'll be very interested to hear how it works out.

I have some worries about that as well. I don't have enough experience with MMX to know how bad or how fast the crud builds up.

I am planning on keeping a WD40 can and a wipe near the pad and ask folks to wipe things down as needed. I was also thinking of hanging a wire brush out there to keep it handy.

It will get tested this weekend, weather permitting. Right now, 90% of my club's MMX fleet belongs to me and I don't have too many so I doubt it will get a real workout, but its a start.

 

[JAL3]

I advertised the availability of a new MMX rack to my club and solicited everyone to bring out their MMX rockets to give it a try. Pretty much as expected though, I was the only one of the Alamo Rocketeers who had any MMX rockets and I only had two with me. One had never flown before and it was destined to have its maiden flight coincide with the maiden launch of the new system. That would be my MMX Centuri Vulcan.

For an igniter I used the Quest variety without the pyrogen. I straddled the leads over the electrodes and clamped the igniter in place with a clothespin normally used as a rod standoff. I tried to make sure the igniter itself was at the right height for the the rocket to set upon.

 

[JAL3]

As I tried to set the rocket in place, I noticed that the wooden clothespin holding the igniter in place tended to slip a lot. Then I realized that I could probably do without the clothes pin and use the alligator clips to hold the igniter in place and make contact with the electrode.

 

[JAL3]

The rocket and the rack then spent some time service as a static display before it was actually used. When the time came, though, the motor ignited instantly and the rack performed as wished. The flight was unstable but I could not blame that on the rack.

 

[JAL3]

The next victim to be launched on the new rack was a Fliskits Dead Ringer. Using the clips as before to secure the igniter, it was set in place with little or no fuss.

 

[JAL3]

When the launch button was pushed, this rocket too took to the air instantly and had a good flight except for the loss of the nose cone. Unfortunately, that loss precluded any more test flights for the new rack that day.

 

[JAL3]

This rack accomplished most of what I set out to do but I already see room for improvements and modifications. I hope to set it up for a few flights at an upocomming Freedom launch and then will consider some of those modifications.

This is not a light system but that mattered less to me that its durability and ease of use. So far, I am happy in those respects.

Persons interested in keeping up with this project as it evolves can follow it here: https://www.flickr.com/photos/23694991@N03/collections/72157622024797287/