RC Tank Warfare community hobby forum

There has been some conversation in 43rdRecceReg's post about his Comet build relating to the No 19 Radio Antenna Base. Rather than continue it and 'hijack' the topic I have started this thread.

I made an antenna base for my Cromwell build and it needs replacing on my Cromwell as it has suffered battle damage (grandson).

I originally obtained some measurements by scaling the base in the Tamiya 1/35 Cromwell but had no means of verifying their accuracy. I tried to print the base using my 3D printer but failed dismally and resorted to using the brass shim and solder. After several failed attempts I managed to make a base but was not completely happy with it.

In addition to making a replacement I would need a further one for my Black Prince although completion of this is a long way off. I will start a build topic shortly when I have finished the plans and other prep work.

Stage 1

Having fitted a smaller .25mm nozzle to my printer I again tried to print the whole base. Parts of the cage on the base are only 0.5mm thick and these break when removing the support material created in the build. Again this, for me, proved a non starter.

Stage 2

My next step was to split the build into two parts, the base/mast and the cage.

The mast printed ok but it was fragile, particularly at the top where it was only 1.8mm thick. It was not possible to create a hole for the aerial when printing and trying to drill one broke of the top, insulator, part. Any wire for the aerial would have to just be fixed with glue.

Again the cage printed ok and the support material could be removed, usually, without destroying the cage.

Stage 3 to follow

Nicely realised, Peter I made the base and centre section with styrene, but when I tried to use 2mm styrene strips to create the 'halo' supports, it all became a bit too flimsy.
If you're minded to print more than the ones you'll need for your pending projects, I'll happily pay you for a couple for my Cromwell and Comet!

Thanks 43rdRecceReg. Not a problem to print more for you but I am not happy with the durability if working strictly to scale. Might need to beef them up a bit. Let me finish prototyping the options and we can then chat.

enginepeter wrote:Thanks 43rdRecceReg. Not a problem to print more for you but I am not happy with the durability if working strictly to scale. Might need to beef them up a bit. Let me finish prototyping the options and we can then chat.

Wilco.

continued..

Stage 3

As mentioned the printed parts are fragile. I could beef up the print by making things thicker but this would result in 'non-scale'.

With this in mind I decided to see whether or not I could make the base part from brass.

A bit of time on the lathe, taking things slowly and making very fine cuts resulted in a brass mast. All this it not easy on my large Boxford lathe with a fair bit of unwanted movement everywhere. Holes were drilled in the base for dummy bolts.

With a central hole at the top, this enabled a thin wire aerial to be fitted more easily. The printed cage just fitted with care so this was a step forward.

Having got to this point I had to see if I could make the cage from brass and to scale without spending lots of time fiddling with the soldering iron.

That will be the next step and I will report back in Stage 4.

continued ..

Stage 4

My next trial was to see if I could fabricate a cage for the mast from brass. I considered two options, marking out the profile on 0.5mm brass sheet and rolling/cutting and soldering or using some thin wall brass tube. I decide to try the latter.

I had a small piece of ? inch thin wall brass tube that I turned down to 8.5mm o/d. This gave me 7.5mm I/d. I was then going to cut and file it to shape before bending. In an attempt to cut straight and accurate lines I printed a small block with saw guides to a tight fit on the tube. I only printed 2 pairs of slots to the full depth with index marks for the others so as to preserve strength of the block. Allowance was made so the prongs were 1.5 mm wide when cut and then needle files would be used to trim to size, 0.7mm wide.

After making the 8 cuts with a razor saw, the scrap pieces were cut out and the prongs filed to size. The saw block proved useful to hold the tube. And was again used when the embryo cage was cut from the tube.

To get a consistent bend on the prongs I printed a further profile to hold the cage for bending.

Rather than try and solder the cage direct to the mast I decided to solder it to a piece of 4mm o/d tube that would slide onto the mast which in turn could then be soldered or glued in place.

The short length of tube provided an easy way to hold the work, making it easier to solder. The excess solder was cleaned off. Four 1.2mm holes were then drilled in the wall of the tube to give the impression there were two bands holding the cage together before cutting it off from the tube.

This proved one effective way to make the brass cage to fit a brass mast.

3d Printing the mast and cage proved easier and looked a little more accurate/detailed. The brass one took far longer, not as detailed but is more durable.

It all depends what your priorities are!!

All I have to do now id to find somewhere safe to store the bits until needed in 6 months and more importantly remember where!

Very nice work, they look great

Cheers, Lee.

Some fine attention to detail, Peter. PM sent.

Thanks Lee and Roy