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Before I can proceed with the chassis frame, I need to confirm the distance between the upper "axle" and the lower "uplock" of the truss. I am using a TR-4081 (3 meter) segment of F33 Global triangular truss, which has 2" vertical tubing with 3/4" individually welded diagonal bracing. Since the truss tower has to come off the base for transport (design spec - fitting inside my 10' vee-nosed trailer), I am using Global Pro Clamps to securely attach the truss to the hinge bracket. These clamps wrap around the vertical tube which limits their position in the areas of diagonal bracing. Here is progress on the axle bracket... a 4" x 12" x 1/4" steel plate with the Pro Clamps on one side and a pair of mounted sleeve bearings on the other. The sleeve bearings allow the whole truss to rotate around a 5/8" shaft mounted on uprights of the base.

Fortunately, my dad taught me how to drill steel when I was a kid. The drill bit is a much harder steel than the steel you are drilling into, and will have no problem shaving off metal as long as it keeps its edge. Keeping the edge is where the bit needs help. Drill a pilot hole first, and keep the bit cool, using a medium oil and keeping the drill turning slow. Torque is your friend, not speed. By switching belts around on the pulleys of my drill press, I got the speed down to a leisurely 240 RPM. After holes drilled, deburred edges with a larger bit.

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Assembled upper "axle" plate ready to go. Lower "uplock" plate next to fabricate.

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Sather- will we see this pad at MWP?

Probably not this year. First excuse is I tend to build really slow... I have discovered that whenever I rush, I mess something up. Since I don't really have a plan, I am intentionally going slow to avoid having to back-pedal. Grinding off welds is not fun. Secondly, this is technically a school rocket club project, so keeping the construction pace loosely tied to the school year. We hope to inaugurate her at a spring launch.
 
Continuing progress on the 1:4 scale model. I brought it to a Fox Valley Rocketeers meeting, where good friend Ed C. challenged me to make it functional rather than just be a parts buck. First thing it needed is a scale truss, which AFAIK is not available commercially. So, off to the workshop we go. The 10' Global triangular truss I plan to use on the full-size pad has 2" tubes, with 3/4" bracing, (perpendicular bracing at the top and bottom and 11 sets of diagonal bracing). Made a quick jig set to the angle of the diagonals and made 33 of them in 1/4" dowel, with 6 more straight cut shorter pieces for the top and bottom. The 2" x 10' tubes are 1/2" x 30" dowel. Used a pair of cardboard jigs to hold them in place when gluing the end bracing, then carefully cut the cardboard off. I found the easiest way to attach the diagonal bracing was with the truss vertical, letting gravity hold them in place I could work from the bottom up, around the tower, and do them all in one session. Will add some better fillets to approximate the welds and paint silver. Next step is to make scale models of the axle plate and uplock plate.

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methinks that you need a suitably sized rocket to pose on the small version :).
Rex
 
Thank you, Steve. And that is a really good idea, Rex - I will work on that.

In the meantime... math stuff goes here, which is what I've been stuck on for the last two weeks... (Bear with me here, writing this down helps me think it through and gives my fellow math geeks a chance to check my work).

I planned on using two 3/4" clevis pins as uplocks, sliding through holes cut into a cross beam of the upright support and the uplock bracket of the truss. A 3/4" hole drilled through a 2" x 2" leaves 5/8" of undisturbed steel steel on either side to take the load. I assume at least 1/2" should be adequate. (Shout out to the engineers in the crowd - call me on this if I'm wrong. I could go down to a 5/8" clevis pin , leaving 11/16" on either side.) The centerline of this hole is 1" from the truss-facing side of the 2" x 2", and 1" from the base-facing side. (Since the ends of the 2" x 2" square tube cross member is notched to fit flush inside the 2" x 2" angle iron vertical support, the centerline of the hole is 3/4" from the truss-facing edge of the vertical support.)

The pivot bracket plate - taking in to account the two opposing bearing brackets, the Global Pro clamp, and the 1/4" steel plate sandwiched between them, the legs of the truss and vertical support for the pivot end up being 2.34" apart, inside edge to inside edge.

The uplock bracket - the distance between the legs of the truss and the centerline of the clevis pin hole, when the truss is vertical, is 1.59". (2.34" less the .75" the hole is from the inside edge.) I couldn't use a 2" x 2" for the uplock bracket, as leaving the requisite 1/2" of undisturbed metal on the outside edge of the drilled hole would bring the truss past vertical in order to line the holes up.

Since the vertical support is 1/4" thick, an angle iron attached to the truss as an uplock bracket, and fitting BETWEEN the vertical supports must also be less than 2.59" deep or it would hit on the frame of the base before the truss becomes fully vertical. So a 3" x 3" is also ruled out as the uplock bracket.

The initial solution is to take a 3" x 3" and rip (a woodworking term) 1/2" from one edge, essentially creating a 3" x 2 1/2" piece of angle iron, to give it just under a tenth of an inch (0.09") of clearance on the frame when locked up. Putting a 10" abrasive wheel on my table saw should allow me to (slowly) cut off a strip on one side, allowing for the thickness of the wheel, to leave a 2 1/2" piece on the base facing side. Drilling the 3/4" clevis pin holes 0.91" from this edge (1.59" from the other edge) gives a 0.535" piece of undisturbed metal on the outside of the hole. With the truss vertical, the distance between the truss leg and the upright support, edge to edge, is 2.34" (1.59" + 3/4").

First photo shows the initial cut on the uplock bracket. 13" long, to allow for U-bolts to attach it to the truss. Edges to be deburred, faces to be wire-wheeled (grind rail factory evidently didn't bother to paint parts that didn't show), and then 1/2" ripped off one edge before drilling.

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I drilled 8 holes in the uplock plate for the 4 U-bolts. The truss advertises a 290mm total width, with 50mm (roughly 2") main tubes. Doing a little math, I figured 240mm center to center, marked these on the uplock plate, and then marked holes for the 2" I.D. x 3/8" U-bolts at 1 3/16" on either side of that. Bracket fits nicely between diagonal bracing, with the ability to move up or down a total of 3". Next up is ripping off the 1/2" from the top side of the plate. Then starting the vertical supports of the base.

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With the pivot (axle) plate and the uplock (lower) plate complete, I have the spacing dimensions needed to work on the superstructure. The angle irons for the front vertical supports needed to be cut to 31 1/4". I drilled holes for the pivot axle bearing in each 2 x 2 individually, then using the holes to bolt them together, cut the two pieces simultaneously to be the exact same length.

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The rear vertical support is a bit easier. Knowing where the truss will pivot sets the height (above the frame) where it will be level when folded down. Using 13" diameter turf tires and setting the bottom of the frame 18" above the ground gives the total length of the rear vertical supports at 43.6". The truss will rest on the top cross bar when down, a second cross bar will be at the same height as the upper side rails. Even though this is a one-of build, I am building a jig to ensure the parts are in the correct position when welded. Should go together quicker now that the dimensions are set. The last 2 attached images show trial fitting the base to the rear vertical support. (Lying on its back. When finished, the yellow base will be the bottom of a framed rectangle with vertical supports at the front and rear.)

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2 1/2 hours of welding today, good progress on ANFSCD. Rear vertical support built with two 2"x2" cross members and a 3/4" axle, then mounted on rear of frame with 2 added drag braces. Also built one 24" long spindle by welding a 5/8" I.D. tube to a C-channel and a 1/8" shim. This allows it to clear the spindle bracket around a full 120° of motion. At home, I later cut this up into 2/ 1/2" sections. Still need to clean up the cuts, but interesting to note how in the cross section the weld is indistinguishable from the original steel component. Next session, several go kart spindle brackets will be welded to the front vertical supports, with corresponding spindles welded to an upright part of the legs, essentially creating a pair of hinges for the outrigger legs.

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Lessons learned

New rule - Never use a Shop Vac to vacuum up all those little metal shavings you get from drilling metal. The shavings look like little springs with sharp edges, and the inside of the hose is not smooth. When one catches, the rest dog pile it and you end up with what looks like an Aerotech baffle steel wool insert. Way up inside the hose like a plugged coronary artery. Took hours with a length of 3/4" PVC pipe to clean it all out. Better to just sweep them into a dust pan and toss directly into the trash.
 
The first two menu items didn't have any spam.

[video=youtube;anwy2MPT5RE]https://www.youtube.com/watch?v=anwy2MPT5RE[/video]
 
New rule - Never use a Shop Vac to vacuum up all those little metal shavings you get from drilling metal. The shavings look like little springs with sharp edges

This wasn't titanium, was it? :) If so you could sell those for a good amount of money :)
 
This wasn't titanium, was it? :) If so you could sell those for a good amount of money :)

Naw, just low carbon steel. Remember I still have a budget, and a staff administrator to keep it (and me) on track.

I am running the project much as the folks at NASA do... behind schedule, over budget, and with the constant reminder that the person with the checkbook might cancel the program at any time.
 
I envy you guys with CAD skills... I'm still paper and pencil. Here is what I sketched for my welder to envision where the pieces go to lock the truss vertically. There are some additional holes in the lower bracket for a removable tow bar which is reversible to be the third leg. Oh, and I settled on 5/8" clevis pins, which, if good enough for my trailer hitch receiver should be good enough for the pad.

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methinks that you need a suitably sized rocket to pose on the small version :).
Rex

okay, here it is. The BT-50 (Alpha) at 1:4 scale is approximately a 4" diameter rocket (Extreme Wildman), while the BT-60 (Patriot) is just slightly larger than a 6" diameter rocket (Ultimate Wildman). For length, the truss is 30" tall and the real one is 10'.

Notice the addition of jacks to the model's legs. I used a 1/4"-20 threaded coupler epoxied to the leg, with an all-thread as the jack to level the pad base. On the actual pad, I plan to use Bulldog 190756 trailer tongue jacks.

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and with a blast deflector you now have a very nice demo unit for whenever you give a rocketry presentation, nicely done!
Rex
 
Thank you, Rex.

Whenever possible, pieces were clamped together and drilled simultaneously to ensure the holes will line up when assembled. Here is the pair of angle iron 2" x 2" identified in the drawing in post #49 as the locking braces on the frame. They are in position to drill the holes for the uplock clevis pins (vertical), with a scrap piece of square 2" x 2" filling in for the tongue. (The horizontal holes have already been drilled to 3/16" at this point. They eventually will get drilled to 5/8".) But I have a couple questions to be resolved before continuing...

1. I added a cardboard shim to allow a little tolerance so the tongue won't be too tight a fit to remove in the setup process. Which begged the question, is that shim enough? I want to run a small weld bead up the inside of the angle iron where they lay against the bottom of the floor pan, and the square 2" x 2" of the tongue does have a radius, but if the beads bump the 2" x 2" out a little, the holes for the tongue clevis pins (horizontal) won't line up.

2. It wasn't obvious to me when I sketched the drawing in post #49, but the vertical holes for the uplock clevis pins and the horizontal holes for the tongue clevis pins interfere with each other's use. So, one set will have to be moved.

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I had an image in my head when this started, but didn't really draw out very detailed plans. Luckily, making a scale model identified a few mistakes prior to welding those sections on the full size version. Number One - I planned the (2" x 2") front vertical supports going inside the (17" I.D.) frame, leaving 13" between them for the truss. While this could have worked, it would require everything to be perfectly straight and exactly aligned. On the model, the wood has a little warp and the frame isn't perfectly true, and the truss was a tight fit between the verticals. To solve that on the actual, the verticals were moved from inside the frame to the end of the frame, opening the space between them to 17". I will add spacers on the axle shaft to keep the truss centered between them.

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Mistake #2 - There is a little play in the leg hinges that I did not account for. When the legs are folded for transit, they sag and rest on the tires. On the actual, I raised the frame an additional 2", and will add a piece for the leg to rest on when folded.

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Mistake #3 - A piece I call the floor pan sits under the frame, and attached to that are some pieces of 2" x 2" angle iron that stop the legs at the correct 120° position. (attached photos 1 & 2) Unfortunately, I didn't allow for the tongue / tow bar which also goes thru here. I was able to get a razor saw on the model and cut away the conflicting section (photo 3).

Computer modeling really aids in 3D visualization and component interference / conflict resolution. Lacking CAD software, physical modeling makes a reasonable substitute.

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Next step is to make scale models of the axle plate and uplock plate.

Keeping with the new found importance of the model and the fear of progress on the actual pad passing it, (and with the rain we've had over the last few days), I took the opportunity to do a little inside work on the model. I found a few tiny stainless blocks that make a good approximation of the mounted bearings in use on the pivot plate. Two on the vertical supports (now cut to length), two on the pivot plate (on the truss), and a rod for the axle. Voila... the model has a functional, pivoting truss.

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Had a productive day with my welder today... forward vertical supports jigged and welded together, and then welded to front of pad base. 19" x 19" floor pan plate also added under frame. I had previously drilled holes for the mounted bearings and axle on the verticals, so temporarily bolted everything together to check for fit and function. Photos 1 & 2 show the structure with the pivot axle and bracket in place, saddles open awaiting placement of the truss. Photo 3 shows the truss in place horizontal, photo 4 & 5 with the truss vertical. It balances nicely, with easy swing in either direction. Uplock plate not installed yet, so small scrap of wood placed to hold it in the correct position. Truss has plenty of room inside the verticals to swing, will need to cut some spacers to go on the axle to keep the truss centered between them, as well as cut off the excess length of axle.

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Had a productive day with my welder today... forward vertical supports jigged and welded together, and then welded to front of pad base. 19" x 19" floor pan plate also added under frame. I had previously drilled holes for the mounted bearings and axle on the verticals, so temporarily bolted everything together to check for fit and function. Photos 1 & 2 show the structure with the pivot axle and bracket in place, saddles open awaiting placement of the truss. Photo 3 shows the truss in place horizontal, photo 4 & 5 with the truss vertical. It balances nicely, with easy swing in either direction. Uplock plate not installed yet, so small scrap of wood placed to hold it in the correct position. Truss has plenty of room inside the verticals to swing, will need to cut some spacers to go on the axle to keep the truss centered between them, as well as cut off the excess length of axle.

Looking great, Sather! I am thoroughly enjoying watching the dual build! I soooo want to see something fly off of the small scale version!
 
Busy weld session today...

1. Had some leftover scraps from the original donor grind rail set. Added a 3" x 3" angle iron cross beam to lower frame at aft end of belly pan. Added two 3" x 3" angle iron cross beams at aft end of frame, nested to each other with the bottoms overlapping to make a "C" channel. Both pieces to be future support of removable tongue / tow bar / third leg.

2. Added 2" x 2" square tube side rails between forward and aft vertical supports, and 45° supports from the side rails to the forward vertical so stiffen it further.

3. Found a footlocker-style tool box that fits nicely between the side rails, and used the last of the 2" x 2" angle iron to make a tray for it to sit in. Haven't cut the brackets to install it yet, but tray shown temporarily in position in third photo, sitting on scraps of wood. Footlocker in place in fourth photo. It is plastic, so will be removable to a safe location not in exhaust blast zone.

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hmm, aren't the wheels in the blast zone? or am I missing something?
Rex
 
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