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Well, this looks awesome. 

 

I am concerned though about the tubular structure and being strong enough to support the weight.  Also I imagine that this structure would be quite fragile and susceptable to warping over time if 3D printed in resin or any type of plastic.

 

Have you considered making the structure from metal hobby rod or tubing, e.g. brass or aluminium?  Aluminium would not need any painting either and could be joined with an epoxy for metal (Araldite comes to mind).  On the other hand, brass would be a lot stronger and could easily be soldered which would be a lot neater and very strong. Especially if you have access to a resistance soldering unit, though the treasury might object as they are quite expensive, but really are the bees knees...

 

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(why someone didn't use this as nose art on a  B-25 is beyond me...)

 

Some discussion here on joining hobby scale metal tubing.

 

Then you could just 3D print the other components, engine and other details?  This way you could make the model quite big and save on resin at the same time.  You could use Solidworks to produce the drawings for the structural layout...

Edited by Peter Browne
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2 hours ago, Peter Browne said:

Well, this looks awesome. 

 

I am concerned though about the tubular structure and being strong enough to support the weight.  Also I imagine that this structure would be quite fragile and susceptable to warping over time if 3D printed in resin or any type of plastic.

 

Have you considered making the structure from metal hobby rod or tubing, e.g. brass or aluminium?  Aluminium would not need any painting either and could be joined with an epoxy for metal (Araldite comes to mind).  On the other hand, brass would be a lot stronger and could easily be soldered which would be a lot neater and very strong. Especially if you have access to a resistance soldering unit, though the treasury might object as they are quite expensive, but really are the bees knees...

 

image.png.7d5d2f9ad425b45b90376751a544a601.png

(why someone didn't use this as nose art on a  B-25 is beyond me...)

 

Some discussion here on joining hobby scale metal tubing.

 

Then you could just 3D print the other components, engine and other details?  This way you could make the model quite big and save on resin at the same time.  You could use Solidworks to produce the drawings for the structural layout...

Resin once cured is strong enough. there is high tensile resin available but I think depending on scale a normal resin would handle it.
Another option might be print the truss hollow and put rod through negating the need to solder brass rod?

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Hey Joe,

 

what do you think about this smart idea by ALBION ALLOYS by using brass pipes and these tiny PE connectors? smiley215.gif 

 

tSTUzU.jpg

 

You look here ... 

 

 

I'll use it for the Access Arms of the FSS Tower.

 

I think that should work well with your "grasshopper" too. up040577.gif

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I tend to agree that for this particular vehicle metal tubing is the way to go for the bulk of the structure. Not just because of strength, I think the 3D printed resin is plenty strong enough, but just the cost, time, and concern of keeping them perfectly straight. Perhaps model all of the corner joints and 3D print those with a male/female socket connection for each tube. That's my opinion anyway.

 

I also like the idea of a 3D printed assembly jig. This thing looks pretty spidery and not easy to get perfectly aligned. A good solid base to build on looks key.

 

Keep up the great work and keep us posted.

 

Bill

 

 

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  • 10 months later...
Posted (edited)
On 6/10/2020 at 9:12 PM, Peter Browne said:

..Have you considered making the structure from metal hobby rod or tubing, e.g. brass or aluminium? 

 

Hi Peter, thanks, yes metal tubes might work.

 

On 6/10/2020 at 11:44 PM, Aussie-Pete said:

Another option might be print the truss hollow and put rod through negating the need to solder brass rod?

Good idea too!

 

On 6/10/2020 at 11:00 PM, habu2 said:

How about 3-D printing an alignment template to facilitate building the trusswork from rod/tubing?

Yes, you're right.  Fashioning a jig will be necessary.  

 

On 6/11/2020 at 4:34 AM, spaceman said:

what do you think about this smart idea by ALBION ALLOYS by using brass pipes and these tiny PE connectors? 

Nice find, will have a look.

 

On 6/11/2020 at 7:10 AM, niart17 said:

Perhaps model all of the corner joints and 3D print those with a male/female socket connection for each tube.

Great idea, thanks Bill!   I really need to give it a whirl.  Already have the resin, the gloves, IPA, a pair of eye protectors, springtime temperatures in the garage.. Just kinda scared to turn the printer on and break something.   Still need to familiarize myself with the slicer, too.

 

Anyway, here's some old-school scratchbuilding for now... a little progress on the electronics package.  Checking out the last update it was last year.  Has it been that long?  Don't want this to become a decade-long build but it looks like it's turning out to be that way -- just 3 years to go and it will be exactly that. And 3 years is nothing.  I actually feel like I just sat in a time machine in 2014, spun the dish, and fast-forwarded through the years to here.

 

The Antenna is a strand of brush hair from a broom -- bought new for modeling purposes, so that's a clean strand you're looking at : )    I carefully examined the broom in the store and measured the thickness of the brush hairs with a caliper and found them suitable for 1/18 LLRV purposes : )   Actually I should have used a guitar string -- had a bunch I now regret throwing away.

 

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Edited by crackerjazz
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  • 2 months later...
Posted (edited)

I initially tried to extract just the star joints so I could use styrene or aluminum rods to build the trusses but it turned out too complicated for me to create all the various planes for cutting. So I thought I'd just cut up the whole frame into simpler and bigger symmetrical sections for printing.  Some sections look like they could stand up on their own structurally, but where long rods will be jutting out with nothing to hold the ends together I'll try putting temporary rafts.   Not sure how I'll be cutting up the gimbal frame but I'll cross the bridge when I get there.  

 

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Edited by crackerjazz
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Posted (edited)

Hi Joe,

 

I know how difficult it is to pick up where one left off after a long time ... :hmmm: That always takes a lot of overcoming and effort, which is why I take my hat off. e050.gif

 

So good luck and lots of fun. up040577.gif  

Edited by spaceman
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  • 2 months later...

Hi Manfred, thanks!

 

Test prints!

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Some tubes sides are pock-marked with support rod ends.  They're sandable but I wouldn't dare paint these trusses in metallic colors.  Alclad paints show every little flaw on the surface.  But for 3D prototypes they're nice enough to display unpainted for what they are.  Still, there should be some orientation that will eliminate the need for a lot of supports and make for smoother tubes.  

 

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I think I'll finally get to see a miniature LLRV on my desk, however rough-hewn : )   

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Hey Joe,

wow, that's what I call a milestone, :banana: you have successfully printed your first 3D prints, congratulations! 00003423.gif

Now you will see that it gets easier step-by-step and that it will become more and more fun. I am happy for you that your courage has overcome respect. up039822.gif

 

How thick are the thick and thin struts? :hmmm:

 

Keep on printing! up040577.gif

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How are you removing supports?
I use side cutters and a needle file to take away support marks
Best to leave some support to file away than leave holes.
Can it be printed so the supports are on the underside to reduce visibility?

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Hi John, thanks!  Yes they were -- until I started removing them   : )     Thanks, Manfred, the tubes on the legs come at various diameters from 1.4mm to 4.6 on the shock body.  Hi Pete, only the printer part, lol.   You can see how I removed the supports like a kid would tear off gift wrappers : )  

 

Tamiya seems to have an ingenius way of using the least number of sprue gates on kit parts and hiding them.  I realize you can't do that with 3D printing and removing supports is a nightmare everyone has to deal with.  The orientation I used was best in recreating the shock absorbers and bolts well but will try to print this again upside down. The trusses come at various angles, though, and printing it one way necessitates supports where they're least wanted.  It seems LLRVs aren't printer-friendly, haha.   I may need to start breaking it down into different parts -- but it will be more work if I wanted to print them in other scales.

 

I tried searching online for similar truss structures to see what kind of printing problems they had.  Found this guy who printed a Mercury capsule and tower and I see he had the same issues with having a lot of supports to remove:

https://www.tested.com/making/how-tos/534215-bits-atoms-3d-printing-mercury-capsule-miniature/

 

My other problem is these tent ridges.   I tried filing/sanding them down but they just wouldn't smoothen out properly.   I'm gonna try putting a low thin wall where supports can maybe attach to that I can maybe score/break off later -- that might make sanding easier than dealing with tents. 

 

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Edited by crackerjazz
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Hi Joe,

 

as one can see, with Shapeways' 3D prints one has the unsightly problem with removing the residual support wax, :woot.gif: and now you have a similar tricky problem with removing the support struts. :hmmm:

 

But you will find a solution, hang in my friend, you will solve the problem, I'm sure! up040577.gif

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18 hours ago, crackerjazz said:

My other problem is these tent ridges.   I tried filing/sanding them down but they just wouldn't smoothen out properly.   I'm gonna try putting a low thin wall where supports can maybe attach to that I can maybe score/break off later -- that might make sanding easier than dealing with tents. 

uhmm , i using a old rotating toothbrush , i change the top head place  a little piece  round sanding paper , fine sanding paper , works perfeckt and you need not much press on the thin parts , it,s a idea 

oscillating-rotating-powered-toothbrush-Oral-B-Vitality-2D-Sensitive-Clean-Procter.png

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I had already seen the same idea somewhere a long time ago, which I liked immediately and had tried it out, as described here by bubble:thumbsup:

 

Bristles removed, double-sided tape stuck on and fine sandpaper (500), done! :whistle:

 

gBz45Z.jpg

 

Very suitable for larger and accessible parts, but SW's filigree Gearbox Combos would be too delicate for this method. :hmmm:

 

But for your struts, Joe, it should work if you're careful enough. up040577.gif

Edited by spaceman
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Looking GREAT! And I totally understand the "tent" dilemma. I've been trying to work on better ways to print to avoid this and it's an on going battle. Often what works for eliminating pits and zits, as I call them, on detail areas makes the prints not print well and vice-versa. It's the biggest set-back in 3D printing becoming a mainstream replacement for traditional in my opinion. We'll get there. Keep up the incredible work and keep us posted.

 

Bill

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  • 2 weeks later...
Posted (edited)

Thanks, Bill!  I'm looking forward to the day when we see ads for Elegoo or Anycubic support-free 3D printers : )

 

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The sanding tool did help a little.   It caught my eye at the LHS so I picked it up along with a polisher.

 

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I wish I could read Japanese.  But the drawings were helpful enough.

 

I'm also thinking about cutting up a styrene pipe in half and gluing a piece of sandpaper along the inner wall so it can hug the rods and maybe use that.   

 

I may have to reprint the legs, though.   I realized it might actually be better to print the whole quarter leg.  I've also packed more detail into it, with some additional thinner struts and various other stiffener plates that I was planning to scratchbuild after printing.   After seeing what's possible and seeing that the printer has no problem printing plates as thin as 0.2mm, I might as well include all of them.   I've thickened them to 0.4mm on purpose, however, so they can still print in 1/32.

 

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Got rid of the top rods...

 

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And set the tanks aside....

 

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And cut off a whole leg for 3D-printing.   

 

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Initially I was thinking about separating this so I can mount the legs on the scratch-built gimbal frame.  Then I though maybe I might as well include the portion of the frame as well and print a new one.

 

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Estimating the build volume..

 

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I may need to print the shocks separately.

Edited by crackerjazz
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