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Motor manufacturing equipment
Here's a topic I think we're all interested in to one degree or another. We've all heard about the famous (or infamous) MABEL and her siblings and decendants. Reading Carl's interview in LAUNCH, we get another glimpse into the background of the equipment itself, when he describes SEMROC's first machine. The mechanism is air-driven, one supposes due to the need to eliminate sparks that might otherwise be created from electric motors.
What else is involved? For example: How do the separate powders get put into the paper cylinder? How do the cylinders move from one step to the next? How are the cylinders fed into the machine? How are the pressing rams powered? Pneumatic or hydraulic? How do you print the various nomenclatures onto the cylinders? I, for one, would be very interested in knowing this, just for the sake of having a better understanding... |
That is a lot of questions!
To listen to Vern (and Gleda) describe the original Mabel was very exciting for me. It was so different from our machine. Vern was a master of fluid logic design. The original and probably its siblings used no electricity at all. It was all hydralic rams and valves. Even the switches were valves. We started with hydralic and quickly moved to air. The red hydralic stains were a real nuisance, but the real problem was with speed. Air moves much faster than hydralic fluid. When I asked Vern how he moved the ram so fast (to complete one cycle in 5.5 seconds), he almost matter-of-fact said he moved it down until it hit resistance with a high volume, low pressure supply, then switched it over to a low volume, high pressure supply to do the final pack. Once it hit the pre-set pressure, it switched back over to a high volume, low pressure to move the ram back out of the way. THAT is something that I did not think of. Vern was a genius! I am not sure what the level of interest in actual engine machine design is. |
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STOP! When did the new Launch magazine go out? I havn't rceived mine yet. 'Course it'll probably show up today now that I've asked, buit JIC.... Sean |
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I've always had an interest in mechanical design, even as a kid. When I first heard about MABEL it struck a chord, and I have wanted to learn more about how it worked ever since. Now I've learned something about two different machines. Yours was pneumatic, and Vern's was hydraulic. One day I might surprise you; I might even surprise myself...:eek: :cool: :rolleyes: |
Sorry for my ignorance but what brand engines are the Semroc engines?
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Ohhh very cool. I learn something new every day. If I might ask, all of these are going to be A-E? hobby motors? Also will there be the "chance" if hobby motors, to get some different colored smoke in either the boost or delay charge?
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I'll go ahead and ask first. :D
What engine sizes are you looking to make (13mm, 18mm, 24mm, etc)? Composite, BP, or both? Core burners? Will the emphesis be to fill gaps in existing motor lines or make a complete line? Some motors that are no longer around that I really miss... MPC 13mm B4 (awesome awesome little motor!) Estes 18mm B4-6 (much better sustainer motor than the B6-6) Estes 24mm D11-9 (another nice sutainer or min dia motor) and of course...... Estes 18mm B14-anything :) |
Here is a preliminary lineup of the sizes we are looking at:Engine Family Portrait This list is tentative and will be made more final over the next month so we can apply for EX-numbers. This is confidential, but your input is needed so we don't overlook something.
The propellant for all this batch is BP, but we are looking at "steam generators" later for contests. The DECAP's will be a welcome addition for some. They will be available in 2-9 seconds in standard .5g load and -X with 1.2g load. A plugged version will be included as well as an Ejection Charge only version that takes standard igniters and will come in .5g, 1.2g, and 2.0g versions. The order of release will be based on discussions here. The smaller 18mm and under machine is being built first. Engines over 70mm long or over 18mm in diameter will be done on the larger machine. |
Too cool Carl!!!! I thought 29mm BP engines might be too much to ask for. The old Rocketflite 29mm's were a blast. This will make staging MPR a lot of fun!
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Now this is a huge step up for contemporary BP engines!
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What body tubes are available for the 15mm and 10mm motors? These look like they could generate some interesting models. Something I thought about as a possible sideline item -- Pre-packaged deployment charges (not delay chains) for use with electronic triggers, each with specific amounts of pyro, and with two firing ports (one at each end) for redundancy triggering. Not exactly what we'd be using with our smaller models, but possibly for some of those upper-end 29mm birds... I see the DECAPs used for the 13mm and 10mm motors, but can this be adapted for the 18mm as well? Or does the pressure generated in the 18mm package exceed the limits for whatever adhesive/mechanical fixatives will be used? |
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The 13mm DECAP (for 18mm standard engines) will probably be the one we do. If it is popular, we might add the 10mm. One of the primary advantages of the DECAP is precision times. The accuracy of a standard engine is only as accurate as how much of the propellant "runs" up around the ram. The DECAP eliminates this variable. Another advantage is the ability to pick in-between times for models that don't fit the 2 second spread. |
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Now I understand. Thanks. One presumes the "ejection-only DECAP" can be fired with an igniter, not just as part of a motor assembly? |
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One of the first things I did when stumbling back into the hobby in 2001 was buy a bunch of Apogee cones, rings and tubes. Somewhere in my shop I've got a mess of 10mm tubing that was part of the deal. I was all excited when I got the tubes, but he almost immediately ditched the 10mm motor line, so my excitement was short-lived. Guess I have to dig again. :rolleyes: |
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Is that what those tubes were? I've got a bunch myself, from the same source. I think I bought at least two bags of tubes a few years ago, before I knew about SEMROC or even BMS. I may have to look at these tubes again for future BARCLONE projects. They might be useful in some smaller "Schoolyard Sounders"... For Carl: Those Apogee bags were likely filled with Euclid's tubes, so they may still have the mandrels for making them. The last time I checked the Apogee site, like Bill said, I think those tubes had been dropped from the packs (TVM has dropped them; I just looked), but they've been replaced with 29mm tubes. |
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What will be the minimum delay tick? 1 Second or 1/2 Second intervals? |
Planned is 1 second to keep inventory down.
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We will probably get a slightly smaller BT-4 (.410"ID/.436"OD).
Tim's micros were 10.5mm. We wanted ours to be as small as possible within FAI limits. |
Carl, how do you plan to make the core burners?
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The largest core burner initially will be the 3/4C19 - 7.5ns. That was the only booster I liked better than the B14. |
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Carl; Given the process in front of you, about how far away is Semroc from putting the first few on a store shelf somewhere? |
Hello Carl,
Do you plan to manufacture your own igniter to ship with these? It would seem the 29mm PB would need a special igniter. The 24mm and 29mm would be exciting for two stage rockets based on the LT tubing sizes. The first thing I think of when I see these 24mm and 29mm BP motors in your diagram is staging them. . |
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Seriously, you are involved in the earliest stages and will probably see the whole thing evolve, warts and all. |
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Carl,
Concerning those PB (Port Burner, or cored) motors, you said they would need to be drilled. What is the manufacturing problem about using, say, a Teflon-coated mandrel run up through the nozzle during the pressing operation? Couldn't the BP be pressed around the mandrel evenly and completely in a single pass of the ram? Or even have a double-piston, one pressing down from the top, the other pressing the mandrel up from the bottom, to ensure the even distribution of powder? |
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It is really hard to explain. |
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So the pressing action is multi-layered? You fill a small amount, press it, fill some more, press that, etc... until you build up the final amount of powder, then perhaps, you give the whole mass one final pressing to reach the desired compression density? That explains why the mandrel approach would be difficult. You would also need a mandrel at each fill and press station, and getting the mandrels aligned correctly each time would be difficult. The drilling process can be done in one pass after the cylinder has been filled and final-pressed. It's a shame the BP couldn't be hard-pressed into pellets separately, then soft-rammed into the cylinder during the final assembly. I know this brings possible deformation and cracking issues into the pellets, leading to grain failures (CATOs). I'm learning as we go along. This was new information to me. Thanks! |
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Will one of the objectives be then to actually produce a USA-based FAI acceptable competition motor? |
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As I understand it, B14 was drilled separately, but motors blowing on the drill became a problem. The C5 and B8 used a mandrel, but they had problems with the mandrels breaking or wearing down, or cracks developing in the BP around the mandrel. I'm looking at a late model FSI F100 and E60, both made in 1989, and they appear to have been drilled. |
Carl,
This is really exciting news. Please put me down as #1 on the reserve list for 5 packs of each motor and ejection charge. :p And as for the original theme of the thread, if Mark is reading, like Craig I'd love to read an in depth article about how Mabel actually worked. Lee Piester's description at Narcon of Centuri's engine works was also really fascinating, as was Carl's description here. And Carl, I've reconsidered. Make it a case of each. :D |
Hello Carl,
I noticed there isn't a port burner listed in the 24mm casing sizes. I know you said the 24mm and 29mm motors would be the last to be produced but I was just curious to see if you thought there might not be enough interest for a high thrust 24mm motor? Since we're bouncing ideas in this new forum, I was thinking along the design lines of a Semroc version of the FSI Mach-1 Dart with a 29mm port burner staged to a 24mm port burner using the LT tubing sizes. Either a slightly larger version using the same FSI fin patterns or a complete make over into a new unique Semroc design. If you thought there would be enough interest I'd be willing to create and submit some designs for your consideration. Just a thought. What do you think? . |
One small vote for different colored smoke if feasible. Either boost or delay/tracking.
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Colored smoke is something we are looking at. Orange has always been my favorite, but it leaves bad stains from the dye. Manufacturability and repeatability is also a problem. Getting the delay correct with a reasonable amount of smoke is our primary design goal. We used hexachlorethane in the 60's which made volumes of smoke, but it was volatile and the delay time decreased with age. We will probably start out with the a more conventional delay. |
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Unless you've got a way to undercut Estes on price on A8-3, B6-4, and C6-5's I think you should concentrate on motors that are different at first. I'll bet a 13mm B would be popular and if you can get a reliable black powder F or an E that has more power than the E9 there will be dancing in the streets. I think someone has mentioned that the cored B's and C's would fill a void. |
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On the other hand, one of the purported psychological barriers of entry in the hobby industry for small rocket kit manufacturers is the lack of a similarly branded line of motors. |
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But I still like the idea of pooling demand from the varied kit vendors to establish a critical mass of demand for new motors. I think the key is for the kit vendors to invent new designs which would use new, unique motors. For example, vendor X develops a kit which needs 1/2A boosters. Semroc private labels for the vendor who in turn promotes both the kit and the motor. The business is done over the web. Getting it onto store shelves would probably take painful amounts of effort :) But the key is that the motor manufacturing risk is shared with other kit vendors. Doug |
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Doesn't the existence of Semroc , Flis and a bunch of smaller manufacturers disprove that? |
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The 10-18mm engines will be much earlier than the larger engines. Basically, the larger machine would be capitalized from sales from the smaller machine. We have presented the entire proposed family for input and to see if we have missed any holes before we start the EX procedure. |
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