Hooben 1:10 Leopard 2A4 build log

[Jimster]

I admire your engineering tenacity. Certainly a quality build.

[Raminator]

An interesting build to be sure, Inger. Despite Hooben's less-than-stellar reputation, the alloy chassis with plastic skin looks like a good idea that's fairly well executed. Looking forward to seeing how you go with the build!

[inger]

Howdy,

While waiting for the turret armour parts to arrive from the printer, I have started to prepare the original turret parts for modification. This involved removing grab rails, smoke-dischargers and the like. I had assumed this would reasonably simple and quick process. However, Hooben used a unusual adhesive that was completely impervious to acetone. I had also assumed the adhesive used was a type of cyanoacrylate which readily de-bonds with acetone. Eventually, I tried some D-limonene solvent and that seemed work turning the adhesive into small grit-like blobs.

Turret with grab rails etc removed

Turret.JPG (42.42 KiB) Viewed 1774 times

Even applying great deal of care, I did manage to crack the left turret wall trying to remove a grab rail. Nothing serious and easily fixed with ultra thin super glue.

Once all the parts, were removed, I striped away the factory paint job. Aside from wanting to undercoat and repaint the model, I also want to make sure the new parts are bonded directly to surface of the original parts, not a to the paint layer.

The Stripped turret shown next to the 1:35 equivalent part

Stripped.JPG (45.42 KiB) Viewed 1774 times

Turret and detail parts removed and paint stripped

Stripped 2.JPG (53.13 KiB) Viewed 1774 times

Earlier in the week the replacement electronics arrived form SGS in Germany. I ordered these boards in late April and they spent close to two months holidaying at Frankfurt Airport.

"Full Option" control module

FOU.JPG (50.98 KiB) Viewed 1774 times

Gun stabilisation module

GSU.JPG (55.39 KiB) Viewed 1774 times

Speed controller

Speedcontoller.JPG (45.61 KiB) Viewed 1774 times

The following image shows the general arrangement of the electronics in the hull and turret. Communication between the two is the via IR boards at the bottom of the image.

Turret electronics on the left and hull on the right.

I also thought I would spend a little bit of time on the hull.

When I ordered the model form Hooben, the motor and gear box options were not terribly clear, and I ended-up brushless motors. In my opinion brushless motors don't perform well on tracked vehicles at low speed and also require an ESC for each motor and a separate mixer.

I ended ordering replacement brushed motors and gear boxes from Hooben. I spent a bit time swapping out the motors and gear boxes and removing the original smoke generator.

Tracks and drive sprocket removed

Drive shaft.JPG (47.48 KiB) Viewed 1774 times

The original motors. The smoke generator can be seen located below and between the motors.

Engine bay.JPG (44.29 KiB) Viewed 1774 times

The empty hull

Motors removed.JPG (52.4 KiB) Viewed 1774 times

[inger]

The new motors in position

Brushed motors.JPG (46.02 KiB) Viewed 1768 times

I also removed the original smoke generator, which was the standard Heng Long/Tiagen etc type.

Smoke gen.JPG (29.34 KiB) Viewed 1768 times

I will be using a more powerful, home made, smoke generator that will produce a more realistic stream of exhaust. The output of the generator will be controlled by the FO unit and will be proportional to the acceleration of the tank.

Replacement Smoke Gen.JPG (34.14 KiB) Viewed 1768 times

The are a number of gaps in the lower hull that are a result of the way the hull has been cut and folded to accommodate the suspension.

Daylight in the lower hull.

Gaps.JPG (26.98 KiB) Viewed 1768 times

Although I don't intend to run the tank in mud or water, I don' t like the idea the lower hull filling with huge amounts of dust and dirt. I will be blocking off all these sorts of gaps with a two part metal putty.

Now that I have the majority of the parts I need either in production or at least sourced, I will get back on to some sort organised build plan.

The plan is to complete things in the following order: the turret, including the electronics, the upper hull and finally the lower hull and electronics. I plan to complete each of the three elements up to and including priming ready for painting and weathering.

[lmcq11]

Wow, that SGS German electronics look complicated and expensive. Glad you seem to know what you're doing. I would be so scared of frying the board with my limited electronic skillsets. Amazing build.

[inger]

Hello,

I had a good amount of free time this week end, so I able to make some progress with the turret conversion. I wanted to get to the point where the spaced armour and extended turret bustle were ready to to permanently fixed to the original 2A4 turret.

During the week the first batch of printed arrived from the printers.

Turret parts less one stage basket which I forgot to add to the order.

34.JPG (43.79 KiB) Viewed 1682 times

The parts, less the basket have been printed in "draft quality" to cut down on the cost of 3D printing. This level of print quality results in fairly a rough surface texture but given the majority of the parts will be covered in camouflage panels, the surface finish is fine. Where the parts are exposed, the the surface will be sanded smooth or where sanding is difficult, covered with thin styrene sheet.

Basic arrangement of the spaced armour.

33.JPG (44.82 KiB) Viewed 1682 times

The side armour pieces were attached to the separate front pieces with two part rapid set epoxy adhesive.

Despite having measured and re-measured and then measured again, there was an annoying error in the angles and mismatch of the left side armour and left front armour.

Annoying mis-matched parts. In my defence, KMW (the tank manufacturer) could not have come up with a more complex set of angles. At first glance both sides of the turret are are identical. They are different and the side armour is also different to conform with original 2A4 turret.

32.JPG (25.36 KiB) Viewed 1682 times

Clear error....somewhere...

31.JPG (31.21 KiB) Viewed 1682 times

Similar error on the bottom of the right spaced armour.

30.JPG (23.18 KiB) Viewed 1682 times

Top angle is ok....probably pure luck

28.JPG (32.22 KiB) Viewed 1682 times

Top of right armour

27.JPG (32.05 KiB) Viewed 1682 times

The solution to fix the miss-matched angle was to use styrene sheet cut roughly to match the correct angle and file and sand to size.

Styrene sheet cut to fill gaps

26.JPG (48.46 KiB) Viewed 1682 times

All the small shims glued in place with super glue.

25.JPG (31.98 KiB) Viewed 1682 times

After some filing

23.JPG (39.65 KiB) Viewed 1682 times

[inger]

The next part to be tackled was the turret bustle. When I originally planned this step I wasn't sure if I would need to replace the entire rear of the turret or just add the additional storage. The original Canadian Leopard 2A4s came from the Netherlands with an extended rear turret and Leopard A5/A6 style baskets.

Ultimately, I chose to add just the extra storage rather then the entire 3D printed turret bustle. This meant cutting the extend turret storage away and fixing it to the original 2A4 turret.

Once again, what looked like a simple straight cut wasn't that simple because of the angle of the turret rear plates.

Cutting through the large 3D part was also more difficult then first thought. Aside the general toughness of the printed plastic, the interior honeycomb support structure was also hard to cut through, even with a new razor saw blade.

Complete turret bustle.

40.JPG (31.98 KiB) Viewed 1679 times

Separated parts.

18.JPG (43.54 KiB) Viewed 1679 times

The next step was very much the point of no return for this project. To fix the extended turret bustle to the original turret meant cutting of the back of the turret. Up until now I had not touched the original parts of the tank, or anything that I had removed could be easily restored. Now I needed commit absolutely to this build!

The point of no return.

17.JPG (54.26 KiB) Viewed 1679 times

The turret bustle extension in place.

16.JPG (39.16 KiB) Viewed 1679 times

The next part for surgery was the extended spaced armour mantlet. Based on a 1:35 part, it turned out that I had included the assembly structure for the 1:35 model - entirely redundant on this model.

Extended mantlet.

15.JPG (32.9 KiB) Viewed 1679 times

The same part showing the redundant curved structure for attaching the main armament in the 1:35 model.

14.JPG (31.35 KiB) Viewed 1679 times

With curved piece removed.

13.JPG (39.34 KiB) Viewed 1679 times

The 3D part has the top of the original turret mantlet incorporated. Again, a choice to be made about what part to cut away.

I choose cut the top off the original part and fit the complete 3D printed part.

The Original turret mantlet.

42.JPG (42.16 KiB) Viewed 1679 times

[inger]

The new extended mantlet fitted.

9.JPG (53.2 KiB) Viewed 1677 times

Opposite side.

8.JPG (40.62 KiB) Viewed 1677 times

With the upper turret part fitted.

7.JPG (46.53 KiB) Viewed 1677 times

The following images show the printed parts dry fitted to turret.

Dry fit

6.JPG (49.29 KiB) Viewed 1677 times

Rear view

5.JPG (44.45 KiB) Viewed 1677 times

Rear view 2

4.JPG (39.95 KiB) Viewed 1677 times

LH side

3.JPG (38.57 KiB) Viewed 1677 times

RH Side

1.jpg (39.32 KiB) Viewed 1677 times

More shims to close a gap on the left side

2.JPG (26.28 KiB) Viewed 1677 times

The next step will be to permanently fix the parts. This will involve adjusting the side armour so that it is parallel with side of the turret while leaving sufficient space for the smoke dischargers.

[lmcq11]

Good progress, minor issues and some rework are to be expected. Turret add-on armour is so complicated and risky. When I did the Mexas on the Leopard C2 build, each side of the turret armour had 25 asymmetrical facets that need to come together in 3 dimensions. One bad angle somewhere means impacts to many other areas, and rework. When you do plasticard, there is the benefit of being able to see issues and correct on the spot, and integrate the armour with the vehicle in a telescopic fashion with constant checks and dry fit. With expensive 3D printed parts, it’s difficult to plan and see everything at the design phase. Looks like you have only a few minor issues... it’s very good.

[inger]

I have solved the turret mounting issue by installing three pinion gears on to the attachment points for the original turret drive gear. The pinion gears create enough friction to hold turret in place while at the same time allowing smooth turret traverse.

Turret drive gears 2.JPG (31.36 KiB) Viewed 1629 times

Turret drive gears.JPG (62.7 KiB) Viewed 1629 times