RC Tank Warfare community hobby forum

It's a stunning figure I'm sure you will make him look the part Louis.

Thanks Carl!

Now, starting with the turret.

The BMP-1 is equipped with a single man turret armed with a 2A28 73mm low pressure gun firing rocket propelled ammunition, and a PKT coax machinegun . The turret carries 40 73mm rounds in a auto-loader carousel. Also normally carried is a AT-3 Sagger anti-tank missile launcher on top of the barrel but these were removed in Afghanistan.
These are the 3D printed mantlet and barrel sold by Christian for 15 euros. The mantlet is a good base but the barrel is useless and needs to be replaced by one crafted with brass tubes.
The turret is sanded and prepared. However, I noticed that both turret and mantlet need modifications for accuracy.
The mantled does not have the right shape. However, it is a good base and some easy modifications can be done to make it really acceptable.
The position of the gun is too low compared to reference and Trumpeter kit. The bottom of the Ludwig mantlet touches the deck, which is not accurate and a problem rotating the turret. According to my calculations, the position of the gun need to be raised by 3.2mm. That will also make the hatch for the Sagger missile looking better on the top.
Once the bottom is trimmed, a plasticard part is made and positioned on top in order to rebalance the mantlet.
The central hole is re-centered after dry fitting of the mantlet.
It makes the turret look better. The Sagger missile loading hatch does not look so raised anymore.
The mantlet is temporarily in place. Some fine tuning and polishing is still required.
Continuing on following post with the gun barrel

Here is the gun barrel.

It is an important part of the model so it needs to look good. The turret will have rotation, and main gun will have elevation and recoil. Both main gun and coax machine gun will also have flash and sound.

The gun is made of brass and aluminum tubes of 5mm, 6mm and 7mm in diameter. Somehow, 7mm brass tubes are difficult to find so the 7mm aluminum tube is actually the metal center of the HL M-41A3 Walker Bulldog main gun that was discarded on the previous build and getting a new life with the BMP. Very useful to keep everything.
The tubes are assembled. I must admit that its design took a bit longer than anticipated. I had to redo it twice because i did not like my first attempt. Overall, it took about 3 hours of work.
The 73mm gun is a low pressure barrel with short recoil. Shown here is the area of recoil, this section is moving.

You can see the joint rings that were made with the same tubes as above. Once cut with the tube cutter, a single triangular hand file was used to create the grooves that you see. There the rings were glued to the barrel at the right location. It took some practice to get them to an acceptable look. The third attempt was good. Then everything was polished with a polishing nail file. Nothing complicated here, it was all done with simple hand tools.
You can clearly see the 3 tubes of 5, 6 and 7mm fitting into one another.
I had to expand the mantlet hole to carry a 7mm tube, and the locking rings were made with 8mm plasticard tubes glued to the mantlet.
Gun at maximum elevation. Looking at it for the first time in pictures, I can see that the central ring is somewhat too bit. I will have to file it to reduce it a bit. No big deal.
Looking good. I am happy with the result. Much better than the 3D printed tube.
Next step is to create the recoil and elevation mechanism.

Regards, Louis

Like a work of art. That gun is too pretty to paint Love the repurposed gun tube. I too save every bit I scavenge from another build. Or simply something that catches my attention at work on a site. Looking forward to your elevation and recoil systems

Hi

Here is the gun recoil and elevation systems. The following 2 short YouTube videos can be seen.

https://youtu.be/enh05j3tESE

https://youtu.be/ur11VToeKpk

A home made recoil mechanism is built within the gun tubes assembly. Holes were drilled on both side, and then a file was used to make a wide but linear slot for the recoil process. A brass push rod tip from my RC aviation modelling days will connect to the servo and act as a lever, but any metal rod would do.
It is better to run the wires for the flash unit through the gun barrel before assembling the gun that will put some obstructions on the way.
The push rod is screwed through the brass tube inside the aluminum barrel for a solid lever.
The arm of an E-Max servo (eBay purchased) is connected to the push rod lever. A home made mount is created to solidly install the servo on the barrel. There is no over engineering here, it is simple and efficient. The space within the turret is quite restricted and does not allow for anything fancy. The Servo is then connected to the TK-22 recoil servo connector.
The elevation unit is also quite simple and has a similar arrangement with a brass rod. I connected the servo to receiver channel 6 that is assigned the VRB knob on the remote. I found it easier to use the knob than the TK-22 elevation process using the 2 sticks, the lost sound effect is minimal.
Overall, it took about 5 hours of work to design and build the recoil and elevation unit.

Next step is to create the PKT coax machine gun, flash unit for main gun and PKT, and turret rotation.

Regards, Louis

Hi,

This post is for the coax machine gun and the turret rotation.

The BMP-1 is equipped with a coaxial 7.62x55mm PKT machine gun. The gun barrel and flash suppressor extend outside the turret.
Brass tubes of 1mm and 2mm diameter are used to create the body of the machine gun extending outside.
The PKT barrel is created. A 1mm fibre optics from DKLM fits inside the 1mm tube. The flash suppressor is hand made with a file.
The 2mm brass fits correctly inside the Ludwigs mantlet hole for the coax MG. A slot behind the mantlet was previously drilled to allow for elevation with the machine gun.
A home made flash unit is created with the fibre optics and a 5mm LED.
The LED is installed at the back and the fibre is kept flexible in the area of the mantlet for elevation, but kept lower than the recoil mechanism so that they do not ever touch.
For turret rotation, a Vex Robotics 9cm gear is of the perfect size for the turret and fits the HL rotation unit gear pitch. A good find by Carl.
The wheel was made totally hollow to fit the turret like a real one.
The ring was superglued under the turret and the turret can be simply lowered into the hull, and raised. It will have a turret basket that should be fun to make and to see rotating from all the hatches at the back.
Rotation unit is installed, all working perfectly. For a very small one man turret that has rotation, gun elevation, gun recoil, gun flash, coax machine gun flash, i kept it relatively spacious and clean.
Next step is the interior and turret basket.

Regards, Louis

Wow Louis excellent work. Really like the turret ring hollowed out. Brilliant

Hi,

Now starting with the interior of the fighting compartment. This will take a while to complete.

The first step is to prepare the basic structure of the interior so that the turret basket can be created as per available space. There is no raised floor on the BMP. The torsion bars are simply concealed.
I did my best to repro the look and feel of the torsion bars by doing something similar on the RC model.
The interior of the BMP-1 needs some serious study. Use of graph is limited by so many small items left and right, lots of pictures must be assembled. Its complicated and in comparison, the M113 and Marder interior were more simple.
The BMP was designed to fight Nato in an NBC (Nuclear, Bacterial, Chemical) war in central Europe. It is therefore NBC protected and although low and very cramped, it is designed to provide shelter for the crew. The infantry can fight from inside the vehicle through the gun ports at the rear. Each rifle port position is equipped with a periscope and fume extractor that is attached to the AK assault rifle to evacuate the fumes.
The engine bulkhead and turret rotation unit are installed. There is room to represent the commander's station at the front but not the driver's position, it is taken by the gearbox.
Now starting the turret basket. The BMP single man turret is equipped with an autoloader associated with 40 rounds of ammo on a rotating chain mechanism. I knew this would not be easy to repro...
The machine gun ammo is on a large container at the right front and standing on the bottom. There are also a few Sagger anti-tank missiles on reserve, something that I will not repro because they were removed for Afghanistan.
The gunner has a seat directly under the hatch.
I found a picture of the ammo rotating mechanism on a disassembled turret. It was quite useful.
Continuing on next post with the turret basket build up.

Hi,

This is the turret basket.

The inside of a tank turret basket is difficult to study. It is generally small. cramped and the few available pictures show only specific areas at a time. It takes a while to develop a 360 vision of what it looks like. The task is much complicated by obvious differences between BMP model interior. For this BMP, being totally scratch built with no available parts on the market and no instructions, some guessing was required for grey areas. Here I am starting with the base and the structure for the ammo belt.
After a lot of effort, the ammo belt is created to a good level of resemblance, it has the required 40 holders for the rocket ammo. I will build a couple of ammo rounds later for display inside the turret.
In order not to get discouraged by the task, each BMP turret component is studied separately and created one by one with a cool head and lots of patience. This is something I have never seen before. I am learning about the vehicle as I go. It will not have much secret left once i am done with it. Doing such work therefore brings a good challenge and much satisfaction once done.
The core of the turret basket is done. I still have to repro the autoloader arm that displays at the back of the basket. Placement of the RC cables is an issue to be resolved one by one. They need to reach the bottom center of the basket.
The box at the front is the machine gun ammo, with what seems to be a receptacle for the spent cartridges on its right side.
The scale turret electrical cabling will be done at the end of the build once it is all painted.
The turret is lowered inside the hull for rotation testing. It works perfectly. I will post a video of the turret in action once all the RC cabling is connected.
As planned, the turret basket is quite visible from all the large open hatches on this vehicle, and so will be the rest of the interior. This will be interesting to see in action.
Next step is to finish the turret installation and continue with the interior build.

Regards, Louis

Just outstanding work Louis I applaud your ability to go beyond and achieve what many of us would never attempt.