The 'Ideal' Obi ANH Derwent Interconnect Replica

[Darth Lars]

I did a little bit of searching on the web, and I have come up with an unusual suggestion: sulfamate-nickel plated brass.
- Sulfamate nickel plating has a dull grey finish. Sulfamate nickel plating is often done as an intermediate step during chrome plating, so the process should be generally available.
- Brass has a density closer to inconel than steel has, which would give it a more accurate weight.
It is also more machinable than steel which could reduce costs.

If the part is plated, then the color of the base metal is not too important... unless you want to weather it by denting it, of course. However, I am not sure if brass would require an intermediate layer underneath the nickel plating. More information is needed.
Maybe someone with a real balance pipe could get hold of a sulfamate-nickel plated part to compare the finishes?

 

[Serafino]

DL, interesting idea. There are additional issues though–brass alloys are usually pretty soft and easily damaged, and plating adds to the cost. On the other hand machining it should result in a cost savings and I like the idea of getting the color right.

So for those who don’t want to pay for inconel, what are your priorities? For myself this is the list in order:

1. Color
2. Colorability/Weatherability
3. Durability
4. Weight

Edit--it's a fairly minor issue, the weight and color: steel can be given just about any color you like through various controlled oxidation processes, it can be bead-blasted to give pretty much the exact finish seen on most balance pipes, and it weighs 92% of the heaviest possible relevant Inconel formula, and 95% of the more likely formulas.

 

[Serafino]

Ok, there are several trains of thought to pick up again here, I will come back to those soon. For right now, we have literally no information regarding the 'coatings' possibly used on some balance pipes of the type we are interested in.

So the current best idea is to bead-blast to a suitable finish. Later this week I will post a summary of known surface types ('known' only visually) and what I think would be the most accurate choice of surface to represent what appears on the prop.

In the meantime, this is a call out to anyone who can possibly find out anything about the metal coating processes Chris Trevas mentioned earlier in the thread--what sort of processes were in use in 1950?

Expertise in modern processes is a great start, but we really need to know what was possible back then.

Oh, and you can all consider it settled that if there were to be a run of these things, they would be done in two materials.

 

[Serafino]

I mentioned earlier in the thread that I would post a photo of an interesting balance pipe with what appears to be a black finish on the small tube. Kinda makes you wonder if there were some which were all black on the sides.

So here's the example with the black small tube, as well as two of the 3 finishes I have seen on real balance pipes--a very matte finish as seen on the left, and a satin bead-blasted-looking finish on the examples on the right. The third finish is plain metal, not illustrated.

On the original 'Chronicles' saber, the side shows a lot of shine, so it seems likely the original finish was either raw metal or the satin/blasted effect seen above. Although there does seem to be a more matte texture up on the step below the flange.

The Tunisia variation seems to show a more matte effect on the side: TUNISIA PIC (link).

Some shine on the sides can also be seen in some screen caps, a collection of which is HERE (link).

Now what about the front face? As seen in the screen caps, the flange face seems clearly to have the sort of matte grey finish as seen in the left-hand sample in the top picture. The dark area of the rings also seems to reflect in a very diffuse way. I think the whole face of the prop emitter was a matte finish, and I think that's the best match for the appearance here in the face view of the prop:

I am trying to find out more about the finishes used at the time the pieces were manufactured.

 

[ATL Kenobi]

Serafino,
You've probably already considered this, but I was thinking, what if the interconnectors were initially installed as unfinished machined parts much like the one I have (upper left). Then after the engine's ran for a while and the part gathers a bunch of burnt on carbon (the other pics), the routine maintenance would call for the outside surfaces to be bead blasted. Since the Inconel is so hard, one or two blastings would produce a matte finish, additional blastings would give it a bead-blasted look. The small inner tube and the ring-of-holes would possibly retain the black because they're subjected to much higher temperatures.

Just a thought.

ATL

May the PG's smile upon you soon .

 

[Serafino]

Boy the carbonizing on that lower one is really persuasive isn't it.

I would think they would use solvents for cleaning parts that are still in use. As shown in your photos, it's not really as though we need an explanation for how the ring of holes could end up black and the flange face grey, it seems like it can happen naturally--and given the way the parts are locked together, a clean flange face is not all that surprising.

I've gotten a new lead to Rolls Royce, so wish me luck.

 

[motivealloy]

Is this project still in the works? Now that Roman's is calling it quits for a while your balance pipe will fill the void.

 

[vaderdarth]

Yes I second that notion....

Dave

 

[yodakiller1138]

I know I did not get the booster as I got one from Roman. But I'm definetely interested in the Derwent replica. It's the only part I need to finish my Obiwan saber.

 

[Serafino]

Hear me loud and clear–I am not ‘filling the void left by Roman’. The only reason to participate in my projects is because you know the difference and think it’s worth the hassle.

If you donÂ’t know or care about the difference, then: nothing personal, but do me a favor and donÂ’t parade the fact in front of my nose because frankly it messes with my motivation and is just plain irritating. :unsure

Now, on to the subject at hand:

Yes the ideas in this thread WILL be realized in a project soon. Just search the Junkyard for topics by me once a week (or even once a month–how hard is that? ) and you won’t get left behind.

Speaking of which, hereÂ’s an update:

My attempts to research the finish techniques which might have been used came to nothing. Apparently Star Wars props are not a respectable hobby in the eyes of some people. :confused

I did get some clues that we may be able to approximate the finishes I described in the post with the pictures just by using different blasting media, so thatÂ’s something I am checking into still.

I would like a black-oxided emitter myself, which I would then dip just the face of the flange in a vinegar solution to get a nice matte grey look. Further weathering could be done either by mechanical abuse or careful application of vinegar solutions.

For inconel (which it appears may be ‘possible’ for those with $ after all), some other process will have to be figured out individually, as to date nothing has come to light.

 

[motivealloy]

<div class='quotetop'>QUOTE(Serafino @ Dec 21 2006, 04:04 PM) [snapback]1382572[/snapback]</div>

Hear me loud and clear–I am not ‘filling the void left by Roman’. The only reason to participate in my projects is because you know the difference and think it’s worth the hassle.

If you donÂ’t know or care about the difference, then: nothing personal, but do me a favor and donÂ’t parade the fact in front of my nose because frankly it messes with my motivation and is just plain irritating. :unsure
[/b]

:angel No disrespect meant, I was just wondering if the project was still on track. From what i've read you are doing fantastic research.

I didn't see this in the thread... Have you thought about using a magnesium alloy? The color and corrosion properties are similar to inconel. It's just not as heavy. It looks like the original pieces you have are cast instead of machined. That's why I'm thinking magnesium alloy would be a good substitute as you can cast it easily.

 

[Serafino]

Thanks MA, and no worries.

Correct me if I’m wrong, but as I understand it, magnesium has the same problems as aluminum for our purposes–a very light color and low weight. It’s even ‘whiter’ than aluminum right?

Inconel–at least the alloy used for the balance pipes–has a warm grey tone. And I think a lot of the people who may not be able to afford inconel would still like to come as close to its weight as possible–and magnesium is 2/3 the weight of aluminum.

 

[motivealloy]

Magnesium is whiter than aluminium when machined but it's very easy to get a good tint to the outer surface. When it is cast it comes out a very dull gray.

I used to work on old Porsche engines and they were made of magnesium alloy. You would be surprised by the similarity to color the mag will get when exposed to heat and burnt engine oil.

You are right about the weight issue. I'm guessing the inconel balance pipes have a pretty hefty weight to them.

 

[ATL Kenobi]

Yeaaa Inconel..

Inconel is 3 times the weight of aluminum and I like the heft. If Inconel does become a reality, that's what I still want.

ATL

 

[darthsnikelfritz]

If its goin over $100. Might as well go all the way and do Inconel.

 

[Serafino]

<div class='quotetop'>QUOTE(Motive-Alloy @ Dec 21 2006, 05:36 PM) [snapback]1382606[/snapback]</div>

I'm guessing the inconel balance pipes have a pretty hefty weight to them.
[/b]

They have heft, but they are thin-walled enough in some areas that it's not really striking--the difference between steel and the heavier alloys of inconel is only about 8%.

 

[motivealloy]

Ok, I'm going to throw a theory out to you that I've been thinking about.

Deducing from the provided photos and assuming common manufacturing practices in the late 50s and early 60s. I would say that the balance pipe was originally "die cast" then the top flange was milled, as noted in the photos. From doing some basic research it looks as if die casting inconel in the Aerospace industy is a fairly common practice as it assures a denser product.

I thought this tidbit of info was interesting...

"Wrought alloys tend to be better known by trade names such as Monel, Hastelloy, inconel, Incoloy, etc. Commercial nickel and nickel alloys from inconel and others are available in a wide range of wrought and cast grades; however, considerably fewer casting grades are available. Wrought and cast nickel alloys are often used together in systems built up from wrought and cast components. The casting alloys contain additional elements, such as silicon and manganese, to improve castability and pressure strength. Wrought grades by inconel and others are particularly resistant to corosion by caustics, halogens at high temperatures and hydrogen halides, and salts other than oxidizing halides. These alloys are particularly well suited for food-contact applications."

Food for thought. B) What do you think?

 

[vaderdarth]

I am definitely in for Inconel.

Dave

 

[Serafino]

MA–I think it’s very important to distinguish between information about current manufacturing processes and assumptions about how things were being done in the early ‘50's–and I would expect that things were constantly changing since then.

I think castingÂ’s an interesting possibility, and IÂ’ve looked into it a bit. There are points of evidence which do suggest the possibility that the originals were made from cast parts. I wouldnÂ’t call it conclusive at this point though.

I have one more chance of getting some further information from sources with access to historical information, and I will add this issue to the list of questions I send.

For our purposes casting adds a layer of uncertainty, required design skills, and just plain work building masters, which have to be taken into consideration, and some machining will still be required in any case. I'm afraid die-casting is out due the the costs involved. But given the high cost of machining inconel, it is possible that pattern or lost-wax casting could make a big difference in the price, so long as the cost of designing and making the masters correctly for shrinkage isnÂ’t too high.

Just to give folks an idea of what machined inconel costs, when I say there's hope, I mean that there are people out there who can make something like this for around $350-400 total instead of $600. :confused

 

[motivealloy]

Oh, fantastic info.

I too was thinking that casting then machining would be pretty spendy. I know from experience in the aftermarket auto parts industry that just getting a casting die made is pretty expensive. Lost wax may be a way to go as it is fairly inexpensive compared to die casting. But, there are inherent difficulties in that process I wouldn't want to deal with; most notably quality control.

I'll eagerly await your findings from the historical records to see what process was used to manufacture the BP.