RC Tank Warfare community hobby forum

Thank you Barry, Ecam and Herman for your interest and encouragements.

HERMAN BIX wrote:Almost looks like 'Hagenau' outside your window

Canadian winter. We had some additional snow this week, very white and cold.

Ecam wrote: Love those graphite tubes, I would never have thought they could be cut that cleanly with a hand saw and sanded. I would have figured they would fray.

Yes, it needs a fine metal saw blade, its pretty fast and clean. I did a test first with a large tube cutter i had for metal tubes, oh what a mess it did.

Now, the sliding breech... Here's the report and a short Youtube video of the howitzer in action at the end of the post.

The push rod is installed under the barrel embedded in the sliding component.
After some calculations, i made the hole in the cradle right there at a specific angle, aligned with where the push rod is coming out of the chassis at the front.
View of the mating process...
The howitzer was made to slide absolutely freely even with the rod attached to it. With some finetuning of the above steps, it is possible to remove almost all resistance.
First, i tried a regular size 20kg servo. The recoil was working well but the tension of the push rod on the servo was giving it a hard time. I could see that the 20kg servo was at the limit, was having some issues pulling back the barrel in the last 5mm. I decided to go with a stronger servo.
I had to use my beautiful and expensive 35kg servo that i had on inventory. I was saving it for the upcoming 234/3 Stummel build. I will have to get another one for the Stummel steering. Notice the battery in the compartment above the recoil servo. Every free space need to be used. Good thing i was able to put the elevation servo inside the mount, i would have been difficult to make it fit under the deck.
View of the electronics showing how i was able to fit it. The wiring is still loose. Very simple;
- Heng Long gearbox
- Clark TK-22 on the side
- Speaker and receiver at the back
- 35kg recoil servo with scratch built arm with an adjustable push rod
- Battery above the recoil servo
- Elevation micro servo inside the gun mount and connected directly to an available channel on the receiver, assigned to vrB knob.
The model as it stands today. I gave it the fenders at the front, no mud guards yet. The upper hull fits in place, every mm counted.
I also started to detail the howitzer, still has a lot to do.
And here is the model in action. Overall, i am satisfied and it is working relatively well. It gives a whopping 60mm of sliding breech recoil, seen below on the Youtube video thumbnail. It was not easy to do. The recoil is very powerful, realistic but maybe a bit too strong for an RC vehicle. The elevation servo is having a hard time keeping the gun steady in direct fire support mode when it is lowered, but ok when raised. I'll see if i can improve that a bit. Recoil is important on an howitzer, its the showcase of the model. Wartime pictures of the M12 in action show the sliding breech recoil to be quite dramatic.



Next step, detailing the howitzer and the inside of the fighting compartment.

Regards, Louis

lmcq11 wrote:Thank you Barry, Ecam and Herman for your interest and encouragements.

Oh! It goes way beyond interest!

This how most of us learn. Fantastic and inspiring work.

Good morning, Louis!
Amazing stuff, Doc! Watching the recoil and comparing it to footage of the vehicle in action, it struck me that this is one of the few times that something like Heng Longs maligned 'track recoil' could be put to good use. Following along!
regards,
Painless

Louis,

I think Painless has an idea there with the hated track recoil?! What a pleasure to watch! You keep upping your game with every new build! And the speed that you are able to fabricate these beauties is simply amazing! Keep up the good work!

Cheers,
Eric.

I think the recoil is worth all the effort! I can imagine the reaction: "Wow! Cool!"

You know, Painless has a point. If the shovel is dug in... the chassis probably wouldn't have moved as much as SHOOK. I'd bet that thing with a shovel would give off the same effect (as long as the forward part of track recoil would actually cause it to creep ahead?!?).

Top third of page two you wrote:

"Before building the gun base, its time to complete the interior. We can see that the single diamond style treadplate at the back is in 3 sections, two are missing in this photo. There is an horizontal metal rack on the floor to hold on to something."

Then lower on page two talking about the breach you mentioned the (cardboard?) tubes on floor.....
I think this is your answer.

PainlessWolf wrote:Good morning, Louis!
Amazing stuff, Doc! Watching the recoil and comparing it to footage of the vehicle in action, it struck me that this is one of the few times that something like Heng Longs maligned 'track recoil' could be put to good use. Following along!
regards,
Painless

Ecam wrote:You know, Painless has a point. If the shovel is dug in... the chassis probably wouldn't have moved as much as SHOOK

Thank you. Once the back blade is installed and lowered in the ground, the recoil of the chassis will be very good. The blade and mounts will need modifications to look and fit correctly.
Continuing with the build

View of the 1/35 kit cradle and shield for the sighting instruments. Looking good but compared to reference pictures, some of the detailing is wrong or simplified. Everything needs to be double checked against reference pictures.
Frontal shield pictures are rare. The M12 book is essential for the details on this build and highly recommended.
View of the Vandra shield on the left, it is undersized and needed to be redone mainly because the curve around the main no longer fit the new barrel. All the Vandra details around the cradle needed to be removed and redone.
Overview of the new frontal area of the cradle and shield.
The Vandra piping on the lower left side of the cradle was reused, but they need to be shortened because they were too long. As seen earlier, Vandra did not position the cradle correctly on the gun mount, they centered it instead of positioning it more towards the rear. They had to compensate by adding extra length to the piping, which is no longer needed. Now, it is as per reference.
The whole frontal detailing of the cradle needed to be redone as it only had a vague relationship to the real thing.
This Vandra resin part under the barrel at the front would normally enter the cradle when it recoils, but has been modified for accuracy and just for the look. It was positioned so that it does not enter the cradle for the sake of the RC recoil.
continuing on following post.

View from above, reference and model.
Of the breechblock, only the pins on the lower part were cut and reused. Not perfect but not too bad either. These are the kind of parts that are difficult to repro.
Reference picture of the breechblock.
The breechblock as it stands today. Not perfect but improved a lot compared to the Vandra kit.
Having a moving breechblock was important to me. It adds a lot of value to the model.
That's it for now. Next step, the sighting apparatus behind the shield.

Regards,
Louis

Louis,

Everything you are doing here amazes me, so this is an exciting build to watch. I have watched the YouTube video five or six times already. I don't mean to suggest any inadequacy--on the contrary--rather I wonder, will there be smoke from the barrel? Is that even possible with the substantial recoil you have replicated?