45 replies to this topic

[dodgem37]

I had mentioned in the K-4 build that I thought I would compile some imagery to determine if I could scratchbuild 21cm rockets. Well, I found enough stuff to start, so, here is a 2 picture update.


I found that the real-life tube is 1300cm long and, of course, 21cm in diameter. Divided by 32 equals 40.5mm long and 7mm in diameter. A 1/4" tube is 7mm in diameter. I used a 7/32 drill bit to thin the walls.

There are 3 rows of 9 exposed fasteners with each row 120degrees apart, or 7mm. The fasteners are 5mm apart beginning 5mm from the ends. The last fasteners are dropped in as close to the ends as possible. The fasteners are .020 hex rod cut, applied, then sanded down. Between the fasteners I drilled micro holes, sanded the inside residue with steel wool, . . .


. . and inserted super glue in order to glue down the guide rails (I've only done 1 of the 3 - I wanted to show what I had done before the possibility arose of me ruining anything). 1mm wide, bent in half lengthwise. The return isn't a sharp 90degrees. I guess I should use glass as a base, and not my cutting pad. I'll go fix that.

Thanks for looking in.
Sincerely,
Mark

[LSP_Typhoonattack]

Why don't you use Evergreen or Plastruct shapes for the angle iron guides?

[dodgem37]

'Why don't you use Evergreen or Plastruct shapes for the angle iron guides?'
They are too thick, too bulky, and too large.

Sincerely,
Mark

[JRutman]

Looks really good brother. You obviously have much better ref pix than I did when making mine. My pix were not clear or close enough to make out the angle iron or the rivits. I am waiting to see how you solve the support arms as they looked adjustable to me in my pix.
J

[big matt]

That tube looks great! Can't wait to see the ordnance.

[dodgem37]

Jerry, the arms are adjustable. The bottom fits into the hollow top and slides in or out. The top tube has a bolt at its foot, and the bottom tube inserts into that. But I think the bottom tube may actually be an all-thread, or a turn buckle. I'm still figuring out how I'm going to make the arms. Their diameter are relatively small. So far .020 rod appears to match well. I'm working with that and .040 hex rod. We'll see.

Matt, I'm using these:




Sincerely,
Mark

[big matt]

Cool!

[Troy Molitor]

Way cool, Dude. Keep us posted.

Troy

[dodgem37]

Thank you, Matt. Thank you, Troy. I hope to finish at least one and have everything posted before I run off Sunday for a week of holiday.


Parts for a rear arm. The left piece is insulation that represents the base which is welded to the tube. The 1mm hex, I suppose, is attached to the lower arm. It is rotated into or out of the top tube to shorten or and lengthen the bottom spacing. The .5mm nut, I believe, is a tension nut. Then the arm, which represents both top and bottom arms, is bent at the base to enter the wing, and finishing it off is a base washer. A little big, I think.


I mostly wanted to show the base and the location of the arms as they relate to the tube in this photo. The hole will receive the electrical conduit, rightly or wrongly. I punched out a disc and drilled a hole in its center, cut an access, rounded the lower lip then cut the top square to the top lip and applied it to .010 x .060 strip. I also punched a couple of hex bolts. I think from the bottom of the wing to the top of the tube is 6mm.

Rear arm is 11mm. Front arm is 10mm. The at-the-tube location of the arms is based on drawings and photographs. The rear is mid way between bolt heads 2 & 3, fairly in alignment with the bolts. The angle of the rear arm allows for a square enough attachment point. The front still needs work, tho. I've got to sand the face at an angle, which I'll do later.


My apologies for the poor focus. The three guide rails are in. The rear arm is assembled. The hanger ring is 2mm deep with a 2mm stem which inserts into the 2mm base (drilled .040 maybe?) which is attached to the tube. I don't recall the hanger ring rod diameter. I measured 2mm and squeezed the rod in a smooth faced plier, sanded the sides square, round sanded the top, drilled 2 holes, carefully scribed between the holes and scraped out that which I wanted removed. Luckily it fit the hook.

Thanks for looking in.
Sincerely,
Mark

[nmayhew]

errr, i think "wow" is the word i' m looking for!!

i still cannot believe there are not aftermarket options for these out there

any chance you can go into the mastering business??

pretty please?

[LSP_Typhoonattack]

'Why don't you use Evergreen or Plastruct shapes for the angle iron guides?'
They are too thick, too bulky, and too large.

Sincerely,
Mark

Aside from that, what's wrong with them?

[LSP_Typhoonattack]

They do look real good. I think I may have some nice illustratons around here for these, but it looks like you don't need any help.

[Kagemusha]

Crazy, but brilliant!

[dodgem37]

'any chance you can go into the mastering business??'
I don't know, Nick. If a Vender happens to peruse this thread and likes what they see and contacts me then I'll do it. But I just don't have the initiative to begin the process.

'I think I may have some nice illustrations around here for these, but it looks like you don't need any help.'
Kevin, If you have imagery I'd be happy to receive it. It could only help fill in the spaces.

A few more pics.

I wasn't happy with the way things were going when I was working on the kit. Things just weren't working out like I had hoped. I had drilled the holes thru on the aircraft during construction so the arm base was always moving. So I drew things up on a G-6 wing to find out what part of the problem was. As you can see, the outlying holes are not square to each other. Knowing that solved a big alignment problem.


So I drew everything up on an index card, and when set on my desk gave me a secure base.


I had read that the optimum mounting angle was 7 degrees, but it varied due to field installation and what-not. So I drew up a 7 degree angle and measured the front and rear end HOFF, height-off-finished-floor, as we used to say in the trade.


And made this. I used .020 rod for the arm, as the wire without the insulation is .020 in diameter. The rod allowed me to easily find the end angle cuts I needed to make for a snug fit. Arms sit on a punched disc. Ignition wire is .010 lead wire.


1 arm assembled and glued in place.


Here I just wanted to show how the ignition wire was worked out. This condition is speculative. The drawing I have shows the outside, and opposite, face and the ignition wire on the opposite side as a hidden line. Photos seem to indicate the wire enters the body at the top and the drawings show a travel line down the side and then straight back to a junction box. I ran the wire along the guide rail. The 'igniter' wire, the curved wire, is not shown in the illustration. That is shown on a 21cm Nebelwerfer. But on a 21cm Nebelwerfer all ignition stuff is on the outside of the tube. So maybe I interpreted the drawing wrong. I don't know. I had read that there is a base-plate as well. I need to do some sanding to get it in the round.


A 21cm Nebelwerfer. Notice the igniter wire can be rotated out of position, and the latch that I suppose is the stop.

Gotta go pack.
Thanks for looking in.
Sincerely,
Mark

[LSP_Typhoonattack]

I've got gobs of Luft stuff;... I'll root around and see what I can come up with that may help.