LPR Space Shuttle Build - just for neil_w

SRB aft skirt progress

Details

Didn’t see this thread until now.

I worked on a 1/110 model a few wears ago, as an intended kit. But the kit never happened.

Using the Guillow’s orbiter, BT-55 SRB’s and 3” Tube for ET. I’d made one the same scale in 1979 using a homemade balsa orbiter.

Link to the TRF thread about the 1/110 model: https://www.rocketryforum.com/showthread.php?8053-1-110-Scale-Shuttle-model-is-a-success!

Also on my website: https://georgesrockets.com/GRP/Scale/Shuttle2009.htm



Info on all my shuttles at the link below, leading to the final versions (1998 boilerplate and the 1999 contest model) that stepped the SRB’s, orbiter stepped from the ET by R/C, and used a Flight Computer in the ET nose to do various key functions (Commanding a servo in the ET to sep the SRB’s at the right time, and to fire the ejection in the ET 1 second after orbiter sep was detected or 7 seconds after liftoff was detected, whichever came first (Apogee was at 4 to 5 seconds). And ONE time the orbiter did not sep via R/C, so the secondary 7 second delay ejection back-up programming saved the orbiter and ET from crashing. ).

https://georgesrockets.com/GRP/Scale/Shuttle-G/shuttlehome.htm





I tried an orbiter with mixed elevons. Had issues. One of which was the orbiter was easy to roll and I was NOT an aileron model flier. I was always nervous when I flew my R/C X-1 in glide because of lack of any dihedral (normally I”m nervous for the boost of an R/C RBG and the glide is low-pressure fun). One day I lost orientation on it and the orbiter spiraled in, smashing the nose. When I rebuilt it, I locked the elevons together for pitch-only from one servo. And modified the rudder to move. But only the LOWER half of the rudder, not the whole thing. Because I had learned earlier that a full-height rudder could, in some cases, cause an intended left turn to become a right roll (rudder acting as a vertical aileron), rather than causing a left yaw to produce a gentle left turn. So, using only the lower half of the rudder solved that, and the orbiters using rudder have handled BEAUTIFULLY.

I know that highly experienced skilled fliers of aileron models don’t think it matters…… but it does if you’re not one of those fliers.

I still have the 1/110 kit prototype model. I keep intending, sometime, to modify it for rudder-only R/C. Not even elevator, just rudder-only. The Guillows orbiter glides with pretty good pitch trim when the CG is correct, and my first R/C B/G’s were rudder-only.

BTW - During boost when attached to a shuttle stack or some other carrier rocket, even the half-height rudder causes opposite roll. Left rudder movement causes right roll. So to fix that, I programmed my transmitters so that when the toggle switch for Boost Mode / Glide Mode is in Boost Mode, the rudder motion is reversed. So, left stick causes right rudder, which causes left roll on boost. Then I flip that switch for Glide Mode, which causes normal rudder, ET Sep (3rd servo), elevator trim from boost (neutral) goes up some for glide trim, and dual rates change (normally on an R/C R/G I have low rate for boost and high rate for glide, but for Control Authority of the shuttle stack I used high rate (lots of control surface throw) for boost, and low rate for glide).

Youtube video of my 1998 1/72 shuttle boilerplate (used a modified orbiter I built in 1984), after finally getting the on-again, off-again project to work like I wanted. Watch how smoothly the orbiter handles when it turns.

[video=youtube;OQbt2VoIuZo]https://www.youtube.com/watch?v=OQbt2VoIuZo[/video]

And this one of a 1/60 orbiter using a G12 powered booster that had to be hand-flown on boost (8 second burn). Much longer glide time, and a good indicate of how it handled (I will admit that at about 30 seconds into the video, I had dived it then pulled up hard to try to loop it… it stalled).

[video=youtube;e_cxNTnIYsA]https://www.youtube.com/watch?v=e_cxNTnIYsA[/video]

Thanks George, I've found several TRF threads that you have contributed to. I'm taking ideas from those, and a lot from your 2009 model. The 2009 URL in the older posts wasn't working, and I couldn't find it trough your normal website. But this link is - so thanks for the additional info.

I've switched back and forth on elevon v. rudder/elevator. But it turns out that my brick/transmitter combo just can't do the elevon - so I'm back to rudder/elevator.

Your drawing collection has been a great resource. The wraps are great. I think I'll end up doing a tapered wrap/decal for the SRB nosecone - I have an idea as to how to build a rectangular version, like your wrap details, then warp it to the right transition shape in Adobe Illustrator.

I'm working on the SRB attachment / detachment points now.

Took a break from filing excise taxes to make a little progress.



So now I've got rudder control. If all else fails, I'll balance for glide and say QED.

Since I'm barely into RC and heavy into lab scale process chemistry, my control line is 1/50" stainless tubing inside 1/16" PEEK tubing.

Elevator will be tricky. My original plan was to add flaps to the back of the existing wing - but that's a shallow V, not a straight axis. Still thinking about it.

All the parts are now in hand for the SRB mountings. Pics soon.

You could hinge the elevators separately, and run them off a split control rod from the elevator servo, routing them through the foam like you did with the rudder control rod.

Or you could make a bell crank with a central control horn and angled outriggers to the elevators, using that green tube as a bearing. That way you could run a single control rod from the servo.

I've done both ways for different projects.

kj

kjohnson said:

You could hinge the elevators separately, and run them off a split control rod from the elevator servo, routing them through the foam like you did with the rudder control rod.

Or you could make a bell crank with a central control horn and angled outriggers to the elevators, using that green tube as a bearing. That way you could run a single control rod from the servo.

I've done both ways for different projects.

kj

Click to expand...

Great ideas, thanks!

Okay, here's fit testing for the SRB attachment.

The system I came up with almost doubles the scale gap between booster. 6mm while scale would be 3.5. But I think it's sturdy and can be flown flexibly.

I haven't made a final choice for the push off springs. Shown are window springs. I might also use a bent and trimmed motor clip. I also have decided whether to put them on the ET or the SRBs

George, if you're still following this thread: did you calculate the axis offset for the motor in the ET, or did you wing it?

Charles_McG said:

George, if you're still following this thread: did you calculate the axis offset for the motor in the ET, or did you wing it?

Click to expand...

Wow, I taclked that in one of the very long shuttle threads years ago.

Basic thing is, build the WHOLE model, except for the centering rings in the ET, and do not glue the aft dome in. Make up a special disc to temporary go just inside the top of the ET tube, and have a clear plastic window on the inside, with fine markign lines. One solid line for the center axis (left would be the left SRB, right of it woudl be the right SRB). Cross-lines every 1/8" from the center towards the orbiter side. Weigh the ET nose, weigh the recovery system, and weigh the noseweight. Also, pre-cut the outer discs for the future centering rings, weigh them.

Add ALL of that combined mass (of things that will not be on the model when you do this procedure) to the center of this special disc.

Make sure this disc can't slide out from the top, I used some tape along the outer edge of the ET tube, folded inwards.

Reason for all of this, is you are going to balance a tire. Well, not a tire, but this method is LIKE balancing a tire. Except you won't be adding weight to one side.

The balancing tool will be a sturdy enough wood dowel, mounted vertically, with a point on the top end. You will place the assembled shuttle (with the special weighted balancing disc in place of the ET nose), to balance on top of that pointed dowel. This is where the clear window comes in, to SEE where the point of the dowel is. You align it so the point stays in the center about the left-right axis. But of course you move the model so the dowel point is somewhere between the middle and the orbiter side. That is what the 1/8" markings are, so you can see how far to go. If it balanced mid-way between a 1/8" mark, then that'll be an extra 1/16" (say between 7/8" and 1", it'd be 15/16"). If it balanced about 1/4 way, then that'd be an extra 1/32".

Now to really judge whether it is balancing level or not, I used a plumb bob method. Taped a scrap piece of 1/8" balsa along the outer top of the ET tube and taped thread to hang down below the ET, with a little blob of clay weighing maybe a gram. I moved the model on the dowel point until the plumb line seemed to be about 1/8" all the way down.

Once you find where that horizontal balance point is, MARK this special disc, and write down on it what the distance is from dead center. Keep this disc for future reference, and also write/type into a file what it is. If at some future time the model mass changed and you had to add "tire weights" to one side to re-balanced the model laterally, then you'd use the old disc again, but this time drill a tiny hole in the balance point and attach a strong thread (like 50-100 pound kevlar) inside of it, so the model could hang by that thread/cord and find out how much mass to add to the non-orbiter side (or towards orbiter side) to re-balance laterally along the pitch axis.

After you've done that, then you can get the Centering Ring discs, mark off and cut the holes for the engine mount tube.

Sort of a PITA , but there's no better way to do it to get it right. That I could think of anyway, without getting into higher-tech or more PITA methods.

The "simpler" brute force way is to ignore it, guesstimate, and most likely the model will pitch nose down or nose up at liftoff due to the imbalance. Which can be solved by adding a crap-load of dead mass to the opposite direction along the ET nose, but as long as the model was already going to be stable enough, then that dead mass hurts performance.

I suspect that many of the old Estes Space Shuttle stack kits that I saw pitch badly at launch were due to the builders building extra-heavy, which messed up the horizontal balance (tire balance) point that the kit was designed for.

And yes, this does mean to really balance it properly, it has to be painted and everything else, too, no significant mass added later, otherwise it has to be compensated for. So, no "mock-up" assembly, doing the above process, THEN painting it! Or adding some heavier R/C gear later, or removing the R/C gear later .

I once did a boilerplate test of a totally new fin system (one single fin on each SRB) using a boilerplate built for when the orbiter had R/C gear in it, but it no longer did. To test fly accurately due to the already-built-in engine mount, I had to add dead mass to the orbiter to simulate what it originally weighed, and using the hanging by a thread method described above to assure the horizontal balance was correct (good thing I still had the original balancing disc and knew the offset distance it was built for)

In theory, Rocksim could do this. In the real world..... no. Just..... no. This is way easier and more certain to be accurate.

georgegassaway said:

Sort of a PITA , but there's no better way to do it to get it right. That I could think of anyway, without getting into higher-tech or more PITA methods.

Click to expand...

Thanks for the detailed description, George. I think It's something I can emulate. I'll have to think about how I want to manage different fin/motor combinations, since I'm building for flexible flight options.

Charles

The SRBs can take the ET weight now.

Finally got the shuttle mounted. I decided to keep the rubber band launch hook, since we are still using it to test fly the orbiter, so I built a catch for it out of the same rail I used on the SRBs. Getting the elevators level and even, so it doesn’t roll is proving to be a challenge.







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Fin progress.



The first set of holes in the aft dome weren’t plumb. So we rotated 90 degrees, marked from the other side and tried again. They look okay this time.

And upright.

I thought maybe the fins would be ‘stashable’ - slide the rods into the ET so the model appears to be sitting on the SRBs, with the fins tucked under. No luck - the SRBs don’t fit in the angle of the fins.

I was struck by a clue by four. Rotate the fins for storage.

This looks slick, Charles. Do you plan to fly it at Bong this summer? I'd sure like to see it in flight.

I sure hope to.


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This is looking fantastic. Maybe I missed it, but did you consider making the fins out of lexan or something? I have never quite decided how I feel about fin add-ons for scale models, whether they should be invisible (lexan), camouflaged (Zooch) or just accepted (this build). I know of course that if they're necessary then they're necessary, and it doesn't detract from what a beautiful model this is.

It's interesting to me how, after decades, modeling the full shuttle stack is still such a difficult and complex proposition.

Neil, I didn’t consider lexan fins this time. They are just so bloody heavy, and I suspect I need to be as tail-light as possible.

Next week I hope to have the intertank wraps done. One mold was printing over the weekend.


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Charles_McG said:

Neil, I didn’t consider lexan fins this time. They are just so bloody heavy, and I suspect I need to be as tail-light as possible.

Click to expand...

Ah, I forgot about the weight. Carry on then.

I did lexan, a little thick, on my Titan IIIe, and it just took -so- much noseweight to balance. I wary of it now. Especially as I don’t have a source of a real thin stock.

For my 1/100 Titan GLV, I’m thinking of using the clear plastic from salad boxes.


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Practicing embossing while I wait for the rest of the plates to be printed, so I've got matching halves.

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This is on Tyvek. It doesn't tear. Once I lay my hands on some ammonia, I'll try cardstock again.

Charles_McG said:

Neil, I didn’t consider lexan fins this time. They are just so bloody heavy, and I suspect I need to be as tail-light as possible.

Next week I hope to have the intertank wraps done. One mold was printing over the weekend.


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Click to expand...

Charles_McG said:

Practicing embossing while I wait for the rest of the plates to be printed, so I've got matching halves.

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This is on Tyvek. It doesn't tear. Once I lay my hands on some ammonia, I'll try cardstock again.

Click to expand...

To be clear: you're printing compression mold halves for smooshing intertank halves out of cardstock? Fantastic!

dhbarr said:

To be clear: you're printing compression mold halves for smooshing intertank halves out of cardstock? Fantastic!

Click to expand...

Yes. I'm using the details from George Gassaway's wraps to make 3D models in tinkercad. A 'model' and a 'mold'. Then My Boyo prints them at his high school. And I try to make embossed wraps.

Charles_McG said:

Yes. I'm using the details from George Gassaway's wraps to make 3D models in tinkercad. A 'model' and a 'mold'. Then My Boyo prints them at his high school. And I try to make embossed wraps.

Click to expand...

That is pretty hard core. Like! :headbang:

A similar technique to 3d print cardstock embossing templates was used to reproduce the Centuri flying saucer in this thread by robnee. This is a one-sided template where you use an embossing tool to press the cardstock into all the molded depressions. Both are really clever techniques.

https://www.rocketryforum.com/showt...-Scout-Ship-Flying-Saucer-embossing-templates
https://www.thingiverse.com/thing:702871

That’s where I got the idea. One sided didn’t work got me; maybe the stringers are too close together.


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Hang test. Like what George described, but hanging from a string instead of poised on a stick. Weights to simulate the nosecone. You can see that I laser cut a disk with a series of holes into which I put an eye screw with the hanging line.

This pic is hanging, not resting on the table. The Cg appear to be -just- off center Z+ : toward the orbiter.

The current weight with an E15 and 2 A8s is 424g. Missing paint and recovery.


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