Leopard 2 No.12: General Improvements and Conversion to 2A4M CAN Standard

[Aaron Cheng]

Now that the last of my initial reference material has arrived, I am pleased to announce my plans for my Leopard 2 kit: A general detail up pass, as well as conversion parts to turn it into a Canadian Armed Forces Leopard 2A4M.

Clockwise from center:
-Trackpad Publishing's Canadian Leopard 2A4M CAN Photoreference book has a ton of good shots for details specific to the Canadian model of the 2A4, including close shots of hidden details like the appliqué armor panels on the hull, the modified headlamp base and more.

-Shinkigensha's Leopard 2A5/A6 Detail Photographs mainly cover German 2A5 and 6 model tanks, but also has a few pages each for other models, like the Leopard 2 HEL or the 2A7. Also has a bunch of shots of the fighting compartment.

-Rye Field Model's 1/35 Leopard 2A6M CAN plastic model. Not especially relevant to my subject matter, but RFM makes, in my opinion, one of the most detailed and accurate Leo. 2 models on the market today, and serves as a general reference for Leopard 2s. They also offer a Leo. 2A6 with a full interior, or as an addon set.

-Canadian Leopard Project: Leo 2A4M Juggernaut reference DVD by Anthony Sewards. Includes some material from the Trackpad Publishing book (which he co-authored), but also expands beyond that to cover pretty much anything you could want to see about the 2A4M. Over 4 Gigabytes of photos, video and documentation, all about the tank in excruciating detail.

-Hobby Boss' 1/35 Leopard 2A4M CAN plastic model. Has more subject-specific parts than the RFM kit, but also has some inaccuracies as well (for example, the rear grille has one more slat than it should).

-Tankograd Publishing's Leopard 2A4M CAN Photoreference focuses mainly on the 2A4M on deployment during the Canadian mission in Afghanistan, while the Trackpad book has more material from the tank operating in Canada, where the slat armour, Electronic Countermeasure modules and Barracuda Mobile Camouflage System are not used. This book compliments the Trackpad book quite well, as they focus on different things and provide detailed views in different areas.

Tankograd Publishing's Leopard 2 Maintenance Photoreference is all about the German 2A6 in maintenance, and contains a lot of photos and insights on the interior of the tank. A few pages near the end also cover things like the training simulator for the turret crew and the maintenance hall itself.


The planned modifications are as follows:
-remanufacture of the running gear components to improve detail and strength, namely the return roller housings, both types of bump stop and final drive housing
-modification of the track pins to more faithfully retain the end connectors, center connector will likely stay the same
-remanufacture of the bollards to better support load for use as the main tie-down points for transport
-possible remanufacture of the tail light cluster to better represent my specific subject matter
-scratch build of the late-model light side skirts
-addition of the NBC system access door
-scratch build of the late model smoke launcher rails and launcher tubes (6 tubes planned, but easy enough to mount the remaining 2 underslung tubes)
-remanufacture of the PERI R17 sight head
-scratch build of the 2A5 style turret rear, including the extra stowage bins and turret baskets on the rear quarters of the turret bustle
-remanufacture of the Muzzle Reference System to better match the subject

In addition, there are parts specific to the 2A4M that will need to be made, such as:
-welded appliqué armour for the hull sides
-composite armour panels for the hull and turret
-mine protection plate for the hull floor
-slat armour package for the hull and turret, as well as the mounting points to be added
-upper glacis plate appliqué panel
-driver's thermal camera array, front and back
-snow grouser brackets for the rear of the turret
-Canadian specific antenna masts
-a lot of velcro patches

Some things that could be considered for the future are the Barracuda MCS, but I haven't found a material that I am happy with yet so it will have to be shelved for now. There is no specific hull number that this model is planned to represent, but the current plan is to have it equipped with the ECM modules and slats, but in pristine condition (all 2A4Ms sent to Kandahar province suffered some damage to the slats as the tanks were unloaded). I also don't plan on posting a complete build log of the Leopard from the beginning, but if I notice something that I think is worth calling attention to I will probably make an entry, and I'm happy to answer any questions regarding the modifications or build advice in general.

Till next time,
-Aaron

[Aaron Cheng]

Starting off with some easy tasks for the running gear first.

Added a hole to pin the idler shaft to the adjuster crank, in the same manner as the trailing arms for the main road wheels. The thru hole for the adjustment screw socket is plugged with a set screw, and will be locked with retaining compound and ground flush later.

The pivot bushing has a washer to set the spacing between the bushing and the retaining cap; this washer is ground to a height that gives an overall clearance of 0.05mm, practically eliminating any slop in or out of the joint.

Timing the socket to the correct orientation is done with steel shim stock; approximately 0.05mm for the left side, and 0.33mm for the right (pictured). The assembly is then glued with loctite 638 and torqued into position. The cup and ball for adjusting the idler position will probably be polished after painting.

The re-manufactured final drive casing adds a locating ring that aligns it with the receiving hole for the driveshaft. Any adjustment to spacing between the driveshaft and the driving gear from the motion pack I am hoping to do on the motor mount side, or failing that, simply revert back to the original casing and adjust from there. There is also a clearance spot face at the bottom of the main bore to clear the inner race of the ball bearing that sits at the bottom of the bore. On the original part, this is a 20mm clearance hole, but on the new part this is tightened up to 15.4mm, leaving 0.2mm per side clear of the driveshaft and to help reduce the ingress of contaminants.

[Chang]

... The pivot bushing has a washer to set the spacing between the bushing and the retaining cap; this washer is ground to a height that gives an overall clearance of 0.05mm, practically eliminating any slop in or out of the joint.

Hi Aaron,

Your project plan is very technically skilful.

My I ask something I am interesting so far :

(1) The pivot bushing was not included in the kit. Is it self-made ?

(2) Is the "washer" also a self-made one , or the M6 washer included in kit? No other washer shown.

(3) What does it mean " to set the spacing between the bushing and the retaining cap" ? Is the "retaining cap" the Idler spacer CV0218?

Thanks in advance.

Lerh Chang

[Paul Sparkes]

Chang,

All the parts pictured are in the kit. I did a very similar thing apart from I changed the kit washer for a thinner 6mm shim washer that suited.
The alterations are done to tighten up the tolerances as mine was a little loose for my liking.

[Chang]

Thanks Paul for clarifying the confusion. The "Pivot Bushing" is the "Idler shaft Bush CV0214".

[Aaron Cheng]

Hi Chang,

(1) Apologies for any confusion about that part; Normally I catch that kind of stuff during proof reading, so I'm not sure how I missed that.


(2) The M6 washer is indeed the one included in the kit, but really any standardized washer will do as long as the inside hole is at least 6mm in diameter. The main thing is modifying the washer though; I have access to a surface grinder, so I don't really have to worry about keeping the two faces parallel to each other. You could do it by hand with a whetstone for sharpening knives for example, or even a sheet of sandpaper fixed onto a sturdy surface, but one should take care to use circular motions to reduce the risk of having the faces not aligned, and to check your size in several places often.

Another thing to consider is your paint thickness; the idler shaft bush should be sitting just proud of the idler bearing it sits in, but after painting the idler shaft itself may rub against the paint on the idler bearing.


(3)If we look at our Leopard hull from a front view, the idler can rotate forwards and backwards as we need it to, but it can also slide left and right inside the idler shaft bushing (think of a telescope extending or retracting). This is normal, as all dynamic assemblies need to have clearance in order to function, but using the M6 washer as supplied gave the assembly a telescoping range more than I would like. By using a thinner washer we can reduce the distance of that telescoping action to a small amount, while still leaving enough room for the idler to freely rotate. Again, if you are considering this modification as well, it might be better to wait until after everything is painted and coated, in case you make the washer too thin to account for paint thickness.

Also, a bit of a teaser for the next report:

Hopefully I will get enough spare machine time to finish this in the next week or so.

-Aaron

[Chang]

Thanks Aaron for further explanations. I like to learn from builders with genius idea of modifications.

So far I haven't reached your or other builder's progress. Only have done two tracks , 81 links per track as per the instruction manual advice.
Read from many sources that 82 links per track on the real Leopard 2. I wonder if I used 82 links and raise all suspension angles a little , will the hull's ground clearance met 1/6 of (500~550mm of the real tank) ?

Maybe the idea of 81 links is based on R/C purpose.

Happy building.

Lerh Chang

[Aaron Cheng]

With the tank on a stand and a road wheel plus track in position, setting the trailing arm at -30 degrees to the horizontal gives a ground clearance pretty close to being in scale. The manual calls for an angle of 25-30 degrees which should settle to around 23 degrees, so maybe setting at around 32-34 degrees would do the trick? It's a bit early to think about right now since we're still waiting for electronics, but it probably wouldn't be a bad idea to have an extra pair of links ready just in case.

Also on the topic of track sets, every Leopard 2 plastic model I've built so far has anywhere from 80-82 links per side, so Armortek using 81 links per side sounds about right. It's also worth mentioning that the end and center connectors are a bit longer than scale, so there is more space between links which could explain the supposed 'missing' link.

-Aaron

[Aaron Cheng]

Don't you love it when a prototype works perfectly the first time?

As you may be aware, the Armortek kit does not use cross pins for the track pins, as they are intended to be secured with loctite into the end connectors. I chose to add these features back to the track pins, and so I designed some fixtures to help me do just that.

I present to you, the Trackmaster 2000 and Mr. Pin Set:

With these two fixtures, I can add the holes necessary to the track pins, as well as fabricate the brass bushing that fills up the end connector. First, let's go over the larger fixture on the left and go over how it works.

The fixture is made up of 2 halves; the top half(bottom of picture) retains the parts and also contains the pilot hole for the drills, while the lower half(top of picture) provides alignment for the upper half and sets the correct spacing between the track pin and the end connector.

There is a pocket that locates the end connector in the correct orientation, and a countersunk screw from the other side to hold it in place and fully constrain the part. Just above is the channel where the track pin sits, with an M3 set screw (hidden underneath the pin right now) and an M4 screw with washer at the back to clamp the pin in place once the fixture is closed up.

The bottom half mainly provides location for the parts in the upper half of the fixture; The center M3 hole in the end connector tends to not be actually in the center of the part, so in order to have the track pin sit flush with the outside of the end connector, we need to be able to index the cross pin hole with the end connector. This means that each pin set should be matched to a specific connector set, but in practice the majority of pins will be interchangeable to some degree.

One side of the track pin is drilled 2.0mm with a carbide drill intended for PCB manufacture, while the other side is drilled slightly larger at 2.05mm. This is to make it easy to separate the cross pin from the track pin, allowing you to split the track set for maintenance or cleaning later. Pictured above is the 2mm side, with an M2x6 dowel press fit and ground flush.

As for Mr. Pin Set, this fixture allows for an all-in-one solution for shaping and sizing the brass bushing needed to bring the M2 dowel diameter to an M3 dowel; just big enough to fit in the slotted middle of the end connector. A piece of brass 3mm tube is fed into the hole in the side, and can be shaped either by running a round file through the hole on the right (sized 3.4mm after the file I currently have on hand), or by a 4mm cutting tool (the proper way to do this would be with an endmill, but so far I have had success with a sharp reamer as well).

After the end is contoured properly, the brass tube is put onto the track pin with cross pin, and placed in the channel on the shouldered side of the fixture. There is a 3mm hole at the bottom of the channel for the brass tube to sit in. The thickness of the plate is measured so that you can simply cut off the extra material with a hacksaw and grind to height with a file or bench stone/whetstone.

At the end, I get a brass bushing that I can either attach to the press fit side with retaining compound, or to another M2 dowel for use in the 2.05mm side as pictured.

After adding the M3 screw into the end connector, the screw prevents the brass bushing from going in any further, with the track pin sitting flush with the outside face of the end connector. When both end connectors are retained in this way, they won't be able to fall off, eliminating the need to use loctite to join the track pin and end connector.

I might fix the looser end of the track pins and cross pins with low-strength threadlocker, but as you can see there is not enough space for the cross pins to 'walk out', nor can they fall out from the front once the track links are assembled either.

I am planning to split the center connectors as well to be more faithful to the actual vehicle, so saw cutting fixtures for that are probably the next order of business.

Now, to do this another 646 times.

-Aaron

[Chang]

Hi Aaron. Thanks for sharing your method. It's not an easy job , even for one single time , yet 646 times ...

Regards,
Lerh Chang

[Martin Usher]

The beauty of having a wire EDM at your disposal, i had stacked them up 10 per and ran .012" wire to give .016" gap, plenty of grip now.
just drilling out one half for bolt clearance.

[Paul Sparkes]

The beauty of having a wire EDM at your disposal, i had stacked them up 10 per and ran .012" wire to give .016" gap, plenty of grip now.
just drilling out one half for bolt clearance.

Maybe consider a production run of these, even if its just a few per tank to allow for track removal as once loctited its not an easy job.

[Martin Usher]

All done Paul, I found just fitting i was not happy with grip on just the outside of two clamps so added the internal as clamp and not cosmetic.
break point of track will be marked for maintenance.

works better for me.
Martin.

[Aaron Cheng]

Finished prototyping for the center connector jig, and making 3 cuts with a 0.3mm saw blade gives this as a result. Using a wire EDM would make the task much easier, but minimizing machine time is one of my priorities, so hand cutting it is then. It's just a simple box with saw blade guides and a center screw hole to hold the connector in while cutting, so nothing special.

There is still as small gap once the center connector is installed, so there is no problem with bottoming out before you can clamp the pins in place. The clamping action also prevents the track links from exerting pressure on the end connectors, further reducing the chance of damage due to the holes drilled for the cross pins.

I also assembled a test length of track to make sure everything works as it should before committing to modifying the rest of the components the same way. As Rolf Mönke mentioned before in another thread, cleaning the holes in the track pads and re-cutting the countersink that holds them into the track links were necessary. The M3 flat head screws now sit just below the face of the track link, so hopefully they do not stand out too much after paint is applied. The 'upside down' hex screw in the rear right marks the side with the removable cross pins, so I can keep them all on the same side. I probably will mark off a specific pin as the master pin, but I would like to be able to split the track at any point, so keeping the orientation the same means I don't have to worry about undoing the wrong end connector screw.

The process of modifying track pins, fabricating cross pins, cleaning end connectors, modifying center connectors and cleaning track links is likely to take a few months, so I will continue to work on the rest of the running gear as I work on a few track components in the background.

[Aaron Cheng]

Still cracking away at the track links. The amount of hours expected to go into a full 2 sets is actually quite high, especially since I'm doing almost all of the actual fabrication with hand and power tools as opposed to the CNC machines used to make the fixtures. Keeping machine time down to a minimum is a primary goal for me though, so it is what it is. However, the time I do get to allocate gets to be spent on things that you can't or don't really want to do on a manual mill.

--Bogie Housings--

I was a bit worried about how well the bogie housings would fare over time, bearing the brunt of the shock from suspension travel, so I opted to bore a hole to accept a sleeve bushing. The bushing also sits slightly proud of the outside face of the housing as well, so the suspension shaft rides on that face instead of the housing, saving it from wear and eventual replacement.

The bore is made purposely oversize, allowing the bushing to slip in easily, but still with enough friction to retain it and prevent it from slipping out casually. One of the M4 threads used to fix the housing to the hull floor actually bleeds into the bushing bore (seen in the first picture, on the left housing at the bottom of the bore), so I can purposely deform the bottom of the hole with an M4 screw to increase the retention force, or use a file to lessen it.

A simple fixture with 2 locating cylinders provides a stable base for machining and easy pickup, with an M6 cap screw to hold the housing in place. The left cylinder also acts as the depth stop for the fixture, so the bottom face of the housing hovers above the face of the fixture by a millimeter. The hole on the right is to allow for coolant and aluminum swarf to fall though. Originally it was supposed to be larger for easier clearance, but time constraints had me drill it the same 5mm as the hole for the M6 tap.

Also related to the bogies, I ended up slotting the hole where the hex cap screw normally goes in the housing. Installing the hex screws in-situ proved to be very challenging, so this way I can keep them threaded in all the time in case I need to remove the housings for any reason. Another option would be to loctite an M4 nut into a set screw so you can screw it in from the outside, but since I plan to seal the open holes, that won't be an option for me.

--Return Rollers--

From left to right: Replacement MR128-2RS front bearing with the original 608 ZZ still being used in the rear, Replacement short return roller with cosmetic M3 hex screws mounted, Assembled replacement long return roller without cosmetic screws mounted, and the original long return roller housing for reference.

The return rollers are completely remade from scratch partly to increase the level of detail, but also because the original return roller housings mount to the outside of the hull with screws; When adding the welded appliqué armor to the sides of the hull found on the 2A4M CAN, the external mounting flanges will be in the way, so I wanted to have them mount from the inside of the hull via M3 countersunk screws.

The rollers themselves also get a small modification; The return roller and hub cap are temporarily assembled onto an axle, and the positions of the 2.5mm hole used to mount the dummy studs are transferred to the roller. This is then drilled and tapped to accept an M2.5 set screw, which allows you to tighten or loosen the hub cap by rotating the roller itself, instead of acting on the hub cap and potentially damaging it.

A small adapter plate allows me to transfer the new hole positions from the new return roller onto the hull side plates. 2 M3 screws clamp the adapter to the hull side, while 2 3.7mm gauge pins provide a precise reference for the position of the original return roller housing.

After mounting the adapter to the hull side, the 3.4mm holes for the new housing are transferred (not pictured), and a large 22.23mm (7/8") clearance hole is drilled in the center. This should allow for bearing replacement of the return rollers after assembly, since I plan to braze most of the structural parts of the hull together for strength and weatherproofing.

Next task is likely to be the bump stops, both types being remade to more closely resemble the real vehicle.