GianFrancesco

I will be always happy to be able to be useful to a such dedicated modeller like you

abufletcher

Bit by bit, it's coming together. Today, I made the supporting block from 10x10mm mahogany. The brass ring on top is a slice from a 9mm tube. The bevels were first carved with an X-acto blade and evened out and smoothed with a file (and finally puttied). With the wider arms, the new (inside) width for the base support bracket is now 16mm. The metal "spreader" tubes in the rear are 3mm x 10mm and hold the M2 screws (8mm screws). The top one is aluminum and the bottom is brass because I will probably solder the "handle" onto this one. The "pillar" that supports the gun will be a mixture of soldered brass and wood. When it's all done, I'll fill in the screw heads with putty.

abufletcher

BTW, I've seen the "elevating handle" on both the top and the bottom tubes. On the top it was at 90Ëš to the arm; on the bottom is was parallel to the arm. I prefer the top since that way you can actually see it!

*****

Come to think of it, I think GF said the lever also functioned to lock the mount in place, so it would have to be on the lower arm with the "sexton" part. BTW, does anyone have a better, more accurate term for such a part? TFF, you're a technical wiz...

abufletcher

Mark I of the brass bracket. I extended the inside width to 16mm and also added 1mm to the "bend line" for the 0.5mm brass I've used. Here's what I learned: 1) the holes are in the right places it seems 2) there needs to be a slot in the back of the bracket to accept the "sexton" 3) the outlines on the drawings are too close to the holes (for my M2 screws) so I've extended the outline by 3 pixels and 4) there are still several things about this that I don't understand. For example, I don't understand the slot in the bracket. Structurally, that seems like the wrong thing to do. And why is the bracket at the angle it is? Why doesn't this bracket just mount "flat" on the bottom of the ring (which is what it looks like to me in the photos). And it seems like the sides of the brackets need to be taller. And need to be drilled to attach to the flanges on the ring sheeting.

It's likely that this is just my poor understanding of GF's drawings...but, maybe, just maybe, these questions imply that further "improvements" can still be made (like the thicker arms).

abufletcher

Ah-ha! [sm=omg_smile.gif] So my bracket is completely wrong...either that or I'm trying to put it in the wrong place! I do see the other taller bracket in GF's drawings. So what's this bracket suppose to be?

abufletcher

Oh...here it is! [sm=red_smile.gif] I wonder if I should solder this out of the thicker materials instead of trying to bend it from the 0.5mm brass. The thicker would be more scale...but also more weight. I could also try making it from the same circuit board material (G10?) as the arms. All this does at up in terms of weight and it is all behind the CG. So lighter is definitely better. The GFR material is probably strong enough for this purpose. I mean, if it's strong enough to trust on control horns, it's gotta be strong enough for a dummy gun mount.

abufletcher

I might have to make some minor adjustments to this to fit the slightly different turret shape on this kit.

GianFrancesco

I am sorry; this is the common issue when an "old" drawing made for myself is given to another person; may be that some thing is outdated and the time that is passed doesn't help to remember why.
It seems that the right side for the bracket is the wider one and not the "development" that probably was drawn bifore to "discover" the sexton and the relative use.
Sorry again

abufletcher

No problem. As I've said (but need to say again): There's just no way I could have done any of this without your help! You drawings are still the closest thing I'm aware of to actual technical drawings of the parabellem mount. [sm=thumbs_up.gif][sm=thumbs_up.gif]

abufletcher

When in doubt, check it out! As I suspected there are some slight differences between GF's turret and the kit's turret. Very slight, but still enough to need to make adjustments. And there also appear to be some differences between the turret on the kit and the particular one on the Krakaw CI (the original turrets seem to be slightly variable themselves). Also, the inevitable discrepancies between GF's CAD drawings and my hand-cut parts add yet another variable. These are all very slight differences, but all these difference turn out to be critical in designing a mount bracket what works on my model.

So it's back to the drawing board, so to speak. Or in this case the model. I made a slit with the razor saw through the "back" (i.e. "front") of the turret. This let me slip in a piece of paper that I'll use sketch the geometry of my model and to make sure that the support block (the mahogany part) is exactly parallel (and perpendicular) to the edges of the bracket. The critical point is where the bracket (and flanges) would be dead center on the tuttle deck. This is where it needs to clear the deck. As it rotates to the left or the right there is more clearance. This gives the size of the metal sheeting flange (which looks like it will need to be smaller than seen on the Krakaw CI). Next there's the location of the bolt for the bottom arms. This point determines how tall the mount looks and how far "forward" it is. So this is also critical. Once this point is established the rest must follow from that.

There's a lot of "math" here, but in the end, it's all about the ART of what looks right (to me).

abufletcher

After I get this main bracket worked out, I should be able to get back on track with GF's very detailed drawings. Here's the working sketch that I'll use to make a "test" bracket from circuit board material (GFR). I like the GFR because it's a scale thickness for the bracket. Also it's EASY to work with! The sketch started with the critical pivot points. Once these were located, the curves were freehanded around them to try to get something that looks like the photo.

abufletcher

The new bracket fits perfectly. It was a bit traumatic cutting into the ring, but it looks great. Now I can go ahead and think about fiberglassing the ring. Also now that I see that the bracket works, I can trim it down just a tad.

Mein Duff

excellent work !!!

abufletcher

Now where did I put that darned fiberglass????? [:@] You know how it is when you put something "somewhere special."

abufletcher

OK. Found the fiberglass cloth now I need rubbing alcohol since the the GP finishing resin is thick as molasses! [:@] BTW, did I mention today that I HATE HATE HATE fiberglass on WWI models? (And I did just try to work out a template for lithoplating the turret, but that just doesn't look like an option.)

GianFrancesco

Have you thought to the aluminium self-adesive tape 50 mm. wide that is used by the plumbers?
I have used it for covering of the turret; when doped it seems aluminium as it IS aluminium!
The only advice is to have a smooth surface to stick it to; the grey spray primer you have should work for it

abufletcher

My concern there is that the balsa structure underneath so soft. All of my prior tests failed the "thumbnail" test. But the new harder "body putty" I've been using could provide a somewhat more dent resistant surface. In which case I could try the aluminum tape.

allanflowers

I have read that first treating the balsa with thin CA is fundamental to using the aluminum tape products.

fliegertom

Ditto.....fülle da Balsa mit "dünnem " Sekundenkleber, bis es nichts mehr aufnimmt!
Das klappt schon! [8D]

abufletcher

I haven't give up entirely on the fiberglass. I may be one of the processes, I just HAVE to learn (like silver soldering). But I'm doing a test piece with the putty as well. I'm tried the CA saturation thing in the past and it still didn't pass the "thumbnail" test.

I would imagine the fiberglass is better in terms of "resisting breakage" but applied as thinly as I'd be doing here (thinnest fiberglass filled and sanded to a minimum) may be just a "dentable" at the CA method. And I don't really need the strength on this part. Anyway, I'm experimenting now and should be on my way by this evening.

fliegertom

ja....abu, Du machst das schon!......

TFF

If you have denatured alcohol it will work better than rubbing; the water in the rubbing messes it up. If you keep the epoxy at about 80 deg F, it will thin out more. They did not have fiberglass in WW1, but they have reinforced materials with fabric for thousands of years. I call it legal! It looks great.

abufletcher

Well, I've got the heat lamp going for the test piece. So we'll see. As far as the aesthetics of using fiberglass on WWI models, I guess I can live with it as the equivalent of reinforced fabric. And I'm sure if it had been available, it would have been the choice of the Pfalz DIII designers. I just don't like using it for modeling to get around shaping metal parts. In the case of the turret, I suppose it's just reinforcing the balsa. But unless it's somehow better than the putty and CA method, it's not worth the hassle...and working with epoxies of any sort is always a hassle.

But I accept that I may have to resort to fiberglass for the CI nose cowling. We'll see. I'll certainly try to do one in metal first.

BTW, what techniques do you all use for applying delicate fiberglass cloth? The only thing that even slightly works for me is to thin the epoxy WAY down (to about the consistency of cream) and then brush it on over the cloth. Attempting to "squeegee" on thicker resin just destroys the cloth.

abufletcher

Yeah, the putty and CA (or CA and putty) idea definitely fails the thumbnail test. While it does provide a smooth surface (and one that could be used with aluminum tape) only moderate pressure is needed to make an indentation. So far I'm VERY dissatisfied with all the finishing resins I've tried. They are all just miserable to work with...and seem to take FOREVER to cure (like apply this week and MAYBE it'll be sandable by NEXT week). Or maybe it'll just be a pile of goo that has now destroyed your part.

This is why I've put off doing this for so long.

BobH

My Feedback: (2)

Don,
Don't be discouraged. Put on one layer of cloth and let it set up. Sand it and then put on another layer. If need be add another layer. The mutiple layers help with the dent resistance.