Modding parts for pneumatics

[aol000xw]

Is there any specific glue recommended for ABS?

I have seen it is possible to use acetone and abs dust. I knew this was possible with acrylic, did not know about ABS. Is it a good option? I was thinking of model glue too, I remember it was able of melting the plastic, so I guess that could work.

Indeed I want not only to glue a few parts together but to achieve a perfect seal and a bond strong enough to keep the parts together at max pressure possible with the Lego pneumatic system.

Any idea of how ABS and epoxy bond together?

Any recommendations on how to keep hoses from coming off?

Also thinking of melting bricks...

I know, I know I will burn in hell for my unholiness

[Nalyd997]

I asked the same question when I made my rubiks cube and the answer I got was to just use generic superglue.

And I would use the glue on the outside of the tube

[zux]

What if you'd use tiny ring, that is just as the same size as hose.

[Tommy Styrvoky]

Epoxy is strong, but it's prone to flexing and breaking. Maybe use CA glue (superglue or use Gorilla superglue) if you use something that briefly melts the plastic, then hardens to form a solid part. Kind of like the 3502x cement here http://www.testors.c...dhesive/cement/

I use it on some of my 1/35 models, it works well and is very strong if bonded with the right amount of glue. If too much is applied, it will eat away at the plastic. It's not intended for filling spaces, only for direct contact fits. It usually sets up in 6 hours.

Edited November 27, 2014 by Tommy Styrvoky

[MajorAlvega]

You just want to glue some pieces or you want to create new and solid pieces?

You can try polymorph (or any other of the commercial names available). It's a plastic that melts at around 60 Celsius (just put it in hot water). It's not ABS, at room temperature it's a bit more soft/flexible but it's strong enough. You could mold it but I find it difficult to use with casts. It's not easy to paint but when hot you can add acrylic paint (I used Tamiya) to give it the color you want.

You can also use epoxy putty like Tamiya epoxy putty (smooth surface), more easy to mold and cast (and paint) but less plastic and not so strong.

I've used both to make small pieces for minifigs (hair, pauldron, skirt, weapon). And also fitting electrical (DIY) cables into bricks. Also tried sugru but didn't like it (and also too expensive).

Edited November 26, 2014 by MajorAlvega

[Blakbird]

I asked the same question when I made my rubiks cube and the answer I got was to just use generic superglue.

Standard superglue (cyano-acrylate) outgasses as it cures which will leave a white residue on the plastic. To avoid this, buy "foam safe" CA. This is a different formulation made to be safe for foam R/C models. You can get it at any hobby store.

[Boxerlego]

In the wiki for JB weld it says it can stick to ABS but its really made for steel. If you can deal with the cure time 4-6 hous and the surface preparations JB works really great. Tho molding for pneumatic parts, I cant say If it will work out good, depends on what you molding I would say.

Edited November 26, 2014 by Boxerlego

[Tommy Styrvoky]

what sort of an arrangement of parts will you be adhering together for an airtight seal ?

[weavil]

Normal 2 part epoxy works good with ABS, just make sure it is mixed right or it will fail.

I had thought of doing a MOC with this http://www.hobbyexpress.com/brass_tubing_3mm_od_31083_prd1.htm for most of the pneumatic lines.

[TheNextLegoDesinger]

I asked the same question when I made my rubiks cube and the answer I got was to just use generic superglue.

And I would use the glue on the outside of the tube

that's wat i would take if you want to get it loose you just put it in water for alolng time or cook it in water

[bonox]

Surface prep and cleaning is likely to be as big an issue as the choice of adhesive if you're taking the glue rather than cement approach.

It's not hard or expensive to trial a few options though if you're not sure...

As for the question on stopping hoses coming off, are you using the right sized hose and 'normal' air pressures or are you going way beyond the 40ish psi? If the latter you'll have to start working on adhesives, since i doubt you'll find a clamp that small, or mechanical backup right behind the cylinder nozzle. For example, pass the hose through a 1x2 brick with cruciform (axle) pattern in it to provide a little more grab just before it goes into the cylinder. The other alternatives are small inner diameter hoses, which are bad for the nozzles, stiffer material hoses or hoses with heavier walls.

Out of curiosity though, have you cleaned any grease off the nozzle/inner side of the hose? This could be a major problem for hose slip.

[rumpletump]

You need the kraggle.. trust me everything will be awesome

[TinkerBrick]

@ rumpletump

You beat me. As reading the thread form the top it was the first thing that came to my mind!

[aol000xw]

There are many different parts that I may need to glue together, some may need some kind of glue able to fill in some gaps while others are flat and narrow surfaces so anything might work. The hoses are standard Lego ones.

"foam safe" CA is something I didn't know of, looks promising for just gluing parts, however the air tight requirement makes me wary of it. I might have use for it in another project anyways so good to know.

I have worked with epoxy before but it isn't cheap so that will be my last option, although it has good filler properties.

From your comments and some more internet research I think acetone and abs dust made from old bricks might be a good all around solution and very cost effective. I guess it will take some practice to achieve polished results, and filling gaps may require a lot of experimentation with the mix..

I just remembered that I used some PVC glue in my aquarium installation and the type of bond is exactly what I have in mind. Not sure if it will work on ABS, It might be worth a try.

For the hoses I will make sure the nozzles are clean using some alcohol , but it might be complicated as at some point I want to make some experiments with silicone oil and everything will get a bit messy. But I might have that solved your mention of the clamp gave me the idea of tying some fishing line around the hose at the nozzle and that will give it some extra grip.

Thanks for the answers, I now have to do some tests before having definitive answers.

Edit: After looking more carefully into it acetone albeit cheap won't make the kind of bond I want, I guess it suffers the same process Blackbird explained for CA. So the "foam safe" CA may be better after all. The PVC glue looks perfect if it works with ABS, otherwise I will need an equivalent for ABS or go for the epoxy.

Edited November 28, 2014 by aol000xw

[bonox]

You've not said waht you're doing so I can only guess, but is there a reason you can't put a pressure vessel inside your model and hide it with the bricks rather than turn the bricks into a sealed pressure unit? A PVC pipe for example isn't lego, but kraggle-ing it to achieve something that can't be done traditionally isn't really lego either.

[aol000xw]

I want to do some custom air tanks to begin with, then based on exit/failure a full hydraulic system using silicone oil.

The reason for using Lego instead of other means is that I don't want it to be bulky.

Also there isn't a "ins't Lego" thing for me, some projects use Lego parts only, others don't.

Chocolate may be no 100% chocolate, you know, with the insect parts and all in it, I still call it chocolate.

And I still call this Lego all the way.

[bonox]

part of where i'm going with this is that there is a great reason pressure vessels are cylindrical or spherical rather than rectangular prisms.

My idea was something like this:

http://www.seas.virg...VC Air Tank.pdf

I've built a few of those for non-lego applications and you could work down to 1/2" pipe if you wanted to (about 3 to 4 studs once the caps go on) and gang a few together with Tee pieces if you want volume.

I've never seen it, but manufacturers make pressure pipe down to 1/8"

http://www.harvel.co...0-80/dimensions

if it's of any use to you, but you'd have a harder time putting fittings on it.

edit: hydraulics gets interesting, and you could keep using the pressure pump with air to build gas pressure over the fluid (ie as an accumulator). Just an idea, not of great use though if you're after more precision in actuation.

Edited November 30, 2014 by bonox