Brummbär Conversion - Repost

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phyrephish
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Brummbär Conversion - Repost

Post by phyrephish » Mon Mar 27, 2017 10:25 pm

Converting a Heng Long Pz IV to a late model Brummbär Sd. Kfz. 166

-Repost from the old Hobby Havoc Forum-

I first got into this R/C tank thing barely two years ago. Back then there were a limited number of tank models and accessories available. If you wanted anything out of the ordinary you pretty much had to build it from scratch. However, in the past 24 months and particularly in the last 6 months there has been a virtual explosion in the tank models and accessories available.

To add to the increased variety of models now produced by Tamiya, Heng Long & Matorro there has been a corresponding increase in the number of resin conversion kits available. Two manufactures that have been very productive of late are Store-Juckenburg and Profiline. Both of these manufacturers have released in the past 6 months released Brummbär conversion kits for the Heng Long Panzer IV. The Profiline series of kits are marketed as limited edition kits and may not be around for long. Profiline currently offer an early/prototype Brummbär conversion kit for around the 129 Euro mark. Store Juckenburg offer a late version Brummbär kit for around 90 Euros.

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Being a Brummbär 'fan' I really wanted to build an R/C Brummbär. Having neither the skill nor patience to do a scratch build the only way the I could possibly have a R/C Brummbär was to buy a conversion kit, but which one? After much deliberation I chose Juckenburg's Kit. I chose this kit primarily because it models a late model Brummbär which gave me the options of adding zimmerit and schürzen. To me a Brummbär only lives up to it’s ‘grizzly bear’ moniker if it has that haphazard coating of zimmerit and late schürzen design with those triangular hooks.

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My only concern was at the time of purchase late version drive sprockets and idlers for the Heng Long Panzer IV were not available. Luckily for me this has changed and these are now available from Asiatam. So with decision made, payment and delivery complete lets see what's in the box.

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FIRST IMPRESSIONS
The kit comes in a sturdy box and is well packed. A set of instructional pictures are included. For those not familiar this is a resin kit and as such is quite different to the usual styrene model kits. Production of resin parts is a dark art and the process is not 100% reliable. Blemishes, usually caused by air bubbles are very common on resin parts whereas they are quite rare on styrene parts. Further, what is termed 'flash' on styrene parts is much more pronounced on resin parts. In fact in some cases there may be more 'flash' than part. With that in mind it was great to see all of the kit parts were for all purposes flawless.

There are 24 resin pieces in the kit and a short bit of brass wire to create a grab handle. The largest piece in the kit is the citadel which is well moulded with plenty of detail and very sturdy.

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With so few pieces assembly both on paper and at first glance appears to be relatively simple (we shall see). Oddly, the notek light and horn shown in the instructions and on the front of the box are not included. This is of little consequence as most of the wartime pictures of late Brummbärs that I have seen depict neither. However, a notek light is present on the Brummbär on display at the Munster Museum. Wartime photos typically show a single Bosch headlight is located on the left front fender while the jacking block is on the right. Another feature oddly missing from the kit are the prominent citadel lifting hooks. I suspect producing these hooks in resin would be a waste of time as they would be too 'brittle' to be placed where they are. These hooks would have to be cast in a white metal to be functional on a R/C model.

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While on the subject of corrections, the back deck of the Heng Long Panzer IV is inaccurate (i.e. wrong). If you going to spend time, effort and money on converting a HL Pz IV to a Brummbär then you probably are going to want to correct the back deck as well. Store-Juckenburg produces a corrected Pz IV back deck. This deck matches beautifully with the Pz IV metal operating hatches available from Asiatam. However, this back deck is not included in the conversion kit. I would suggest that the corrected back deck is purchased at the same time as the kit along with the matching Asiatam hatches.

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(seems I got the limited edition gold plated Asiatam hatches instead)

Finally, some comments on the gun. Without extensive modifications it is not easily attached to an elevation or recoil system. The barrel is not hollow and would need to be made so for the fitting of either a flash LED or IR LED. Tank-Modellbau offer an aluminum barrel for the late Brummbär. However, the product description is that it fits the Profiline kit. An attempt will be made during the build to hollow out the barrel and modify the gun assembly so that it may at least elevate. How easy this will be to do we shall see….

Next up….
STARTING THE BUILD
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phyrephish
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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:26 am

STARTING THE BUILD

Upper Hull
First up you'll need a HL Pz IV. For this build very little actual Heng Long parts will remain. If you can get hold of a busted non S&S tank at a bargain price grab it. Once you have your tank 'STRIP IT'. Separate the upper and lower hulls and remove the turret from the upper hull. The first stage will be to assemble the basic superstructure, that is, replacing the rear motor deck and attaching the citadel to the upper hull. Remove the rear plate, air intakes and side panels from the upper hull. A dullish knife blade will do 90% of the work if you need a little more help use a dash of debonder. JUST A DASH, be very careful with the debonder DO NOT get it on surface parts that you want as it will seriously craze the ABS.

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Once all the parts have been removed serious modification can begin. Get out the trusty Dremel and razor saws and cut off all of the top deck. Carefully remove all the tools that get in the way of fitting the citadel. Since the saws were warmed up I decided to remove the front hatches as well as the front and rear mudguards. Part of the plan for this build was to replace the mudguards with brass operating ones. To make this easier I obtained some mini hinges from rctank.de.
http://www.rctank.de/product_info.php?c ... cts_id=500
The shot below shows just the front right mudguard removed

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The back deck of the Panzer IV is actually sloped not flat. So the rear part of the upper hull and air intakes will need modification. The replacement motor deck from Store-Juckenburg may vary in thickness. I sanded the deck down to approximately 3.5 mm in width. Using this dimension 3.5 mm was marked off at the front and top of the air intake supports. 5.5 mm was marked off at the top and back of the supports giving a rise of 2mm over the length of the deck. The air intake support and air intakes were then cut appropriately.

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LOWER HULL
Like the upper hull the entire lower hull needs to be stripped. Getting the motors out may be a bit difficult. You can either cut away the attachment posts or bend the gearbox casings. Cutting out the posts is probably better since they will have to be removed regardless. To help water proofing the lower hull and to provide more space the battery box was cut out.

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I am a big fan of the drive axle supports (Antriebsachsenabstützung) made by Tank-Modellbau.

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Hence the transmission covers were removed.

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Finally there are two major structural errors on the Heng Long Pz IV lower hull that need correction. Both, the rear idlers and last set of return rollers are situated too high on the hull. The problem with the rear idlers is very easily fixed by installing a set of Asiatam track adjusters.

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The last pair of return rollers are a little harder to fix as they need to be sawn off and reattached a little lower on the hull.

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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:27 am

Fitting the Asiatam Track Adjusters
As is the usual case from Asiatam, the Track Adjusters do not come with any instructions. Typically most Asiatam upgrades really don’t need them but still one or two pics and info like what drill diameters are needed would not go astray.

First step is to saw off the outer idler post flush with the rest of the idler assembly. I thought the next part removing the inner locking nut was going to be difficult. However, the nut itself is a separate part that is glued into place hence tricky sawing is not needed. If you are lucky and there is just a small amount of glue holding it on you may be able to simply ‘tap’ it out using a hammer and some metal rod. One or two drops of debonder down the hole can also help. If it still won’t budge you can drill it out using a 3 mm drill bit and if it still there use a dull blade to cut/pry it off.

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Here is where a little bit of info from Asiatam would not go astray. If you look at the pics above of the adjusters you would see that there is a small projection at the bottom (outer part) of the main shaft that increases the diameter of the hole needed for the shaft from 3mm to about 5 mm. To accommodate this projection I had to ‘countersink’ down to the depth of the projection with a 5 mm drill bit. It is still a tight fit and a bit of reaming will be required. If this is what is supposed to be done I don’t know but it all fits and fits pretty nicely.

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Air Intakes
Even though they will be mostly obscured by the toolbox and schürzen I decided to correct the air-intake boxes. Because of their position they needed to be worked on first before the rear deck could be installed. Modifications were made as per the photo below.

A. The front walls of the intakes were removed.
B. The middle vane was shortened at the front and a new divider was attached
C. The molding imperfections on the three original dividers were filled.
D. The middle vane was lengthened to reach the rear plate.
One thing I decided NOT to do was to make hinged doors for these intakes. New doors will be made but they will be attached in the open position. With schürzen and tools in the way it would be just asking for trouble to try and stick fingers in there to open and close the doors. The air intakes were then re-glued back into position marking the first step of the reconstruction.

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With such drastic modification of the upper and lower hulls new means of securing the two halves needed to be found. I chose a simple 'tongue & groove' attachment made from spare brass channel for the front. For the back new supports were made from 3mm styrene and the original attachment posts cut down and reused.

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The rear plate was attached next followed by the rear motor deck

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With the rear deck in place the citadel was fitted to the upper hull. This was done for now using 4 micro screws (one at each corner)

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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:29 am

Once I was happy with the position of the citadel it was screwed & glued in place. Next were added the citadel hatches, bottom half of the cupola, periscope cover, machine gun mount and drivers block.

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As stated earlier resin is not always 100% perfect and thus the citadel once in place did not perfectly align with the HL upper hull. These gaps were filled with Milliput then Tamiya Polyester Putty and sanded. As can be seen in the shots below some corners are a few mm in from the edge of the hull. The next step will be to fill and shape these with Milliput to bring them out to the edge of the hull.

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With the upper hull proceeding nicely it was time to turn to the placement of the electronics. One of my pet Heng Long hates is the placement of the switches on the bottom of the tank. Turning the tank over to turn on or off, adjust volume, smoker or to take out the battery for charging increases the chances of a handling accident. Since the plan is to have schürzen added to the Brummbär turning the tank over is just asking for the plates to fall off. Hence all of the switches need to be mounted topside. Luckily with no turret rotation motor and those lovely large Asiatam rear deck hatches mounting all the switches under the rear motor deck is a breeze.

The photos below show how this was achieved.

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The last shot shows the lead that attaches to the battery charger. There is plenty or room left on the plate for any switches that I may want to add later or even a big cooling fan under the left hatch.

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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:30 am

On with the build......

One of the first things that I noticed missing from this kit was the lifting hooks. As I said before if these were made of resin it would be a waste of time as they would break off quite easily. Thus I made a set of lifting hooks from 1.2 mm diameter brass rod. Six hooks are required, two on the left side, two on the top, one on the front and one on the right side. The rod was bent to as tight a curve as possible and cut to size. The end of the hook was filed round while the shaft of the hook was flattened. Two holes were drilled into the shaft for the brass rivets. The combination of the rivets, CA glue and putty should keep these hooks firmly in place.

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Also added were the citadel spare track holders.

To further optimize space within the hull I decided to mount the receiver board on the new ‘control plate’. The original mounts for the receiver board were cut down and reused.

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Mounting the board here has the extra advantage of providing access to the crystal via the back hatches. The wire at the top of the board is the new internal aerial.

Late model Brummbärs featured a ledge over the ‘muffler’. When it came to building this ledge I noticed yet another correction for the Panzer IV. The output pipe for the exhaust is vertical. The exhaust outlet need to slant both backwards and to the right if viewed from the FRONT.
Here is the modification with a bit of scrap brass pipe of appropriate diameter. Also shown are the single spare wheel mounts

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The ledge was constructed out of styrene whilst the brackets and exhaust cover from brass

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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:31 am

LOWER HULL
Most of the work on the lower hull would be typical for all HL Pz IVs v F and later. The first thing that needed to be done was to increase the frontal armour. Hence 3 mm of styrene was added to the front.

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A 1 mm sheet of styrene was added below this and detailed with 1.2 mm nuts. The towing brackets were detailed with conical rivets and 1 mm styrene added to the back to allow clearance for the spare track links. 3mm wide brass bar was used for the spare track bracket. 2 mm brass rod was used for the new towing pins.

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The alignment of the drive sprockets, rollers and rear idler on your standard Heng Long Pz IV is all wrong. The track on the ground is not parrallel to the return track rather the return track is high on the drive sprocket and slopes downwards to the rear idler.

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The new Asiatam track adjusters easily fixs the position of the rear idler but to get the correct shape the drive sprockets need to be raised 3 mm and the last return roller needs to be lowered. To raise the drive sprockets a 3mm sheet of styrene is placed in the bottom of the 'motor compartment'.

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Since the motors have been raised 3mm so too must the casings.

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The rear return roller is lowered about 3 mm. Real 1.2 M brass nuts and bolts are perfect for the job of reattaching the return roller assemblies.

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If you are using the new idler adjusters you can probably get away without increasing the height of the drive sprockets BUT if the rear roller is not lowered the tracks will look quite odd.

Detailing the rear end

The following was added/removed from the rear end:

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A: Extra bolt detail added
B: Since there is no turret there is no turret motor muffler hence it is removed and the outlet is covered with a rectangular plate.
C: The adjusting levers of the rear idlers were relocated to the more typical 'top' position.
D: Aber clamps for the crank handle positioned.
E: Bottom plate for the towing assembly added.
F: Towing pin and chain added
G: Scratch built filler cap &b retaining chain

Rear deck & fenders

The rear deck where the fenders are attached need to be extended (again about the magical 3mm). New tread plate added along with the covers for the air intakes. Small hinges were used to attach the rear fenders/mud flaps. Rather than create new brass ones I decided to simply cover the original ones with brass shim sheet. Since these will be covered in zimmerit I thought it a waste of money to add expensive brass bolt detail so instead the brass was indented at the nut positions.

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The flaps are held in postion with a mini spring:

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Front deck detail

The small brackets used to attach the spare track to the front deck were a bit tedious to make and postion but finally there were made and operate exactly like the original. The wierd Heng Long inteprretation of slot headed screws were removed and real ones took their place.

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Although the front will be completely covered in zimmerit, tread plate and bolt detail is still added in case it shows through.

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The Dreaded Schurzen:
Constructing & attaching the schurzen was/still is what a have dreaded most about this project. More to come inthe next update but for now here are the main support bars.

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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:33 am

Time for another update on the old Grizzly Bear. Since we last met I have managed to solve two of the four main concerns of this bulid. The schurzen have been made and I've sorted out how best to separate the wheels (pics of these later). Now all that remains is the gun and the zimmerit. Also during this period I decided that some of the hatches supplied with the kit could be easily and cheaply replaced with custom made ones. The original plan for this build was to use all the parts supplied in the Juckenburg kit. However, the availability of the Heng Long Stug hinges as a cheap spare part was too good to pass up. Consequently, much of the recent work on the build has surrounded the the top and rear of the citadel.

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A - New functioning rear hatches made from sheet styrene and Heng Long Stug hinges
B - New rain guard fashioned from copper sheet
C - 1 mm sheet styrene was added to the roof of the rear stowage area to bring the roof closer to that of the main roof of the citadel.
D - Grab handle relocated to the mid point of the hatches.
E - New roof hatches made
F - Additional milliput weld seams
G - Bracing at rear of citadel added
H - Resin aerial mount added

Another view of the rear area showing the added triangular cover for the second aerial mount to the left of the rear box. I did not bother to finish smooth the rear box as this entire area will be covered in zimmerit.

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More detail was added to the rear intake area, mostly the latches for the air intake doors. The two holes at the corners of the citadel are for the attachment of the brackets that hold the schurzen. Also added were the rear fender reflectors.

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Some detail was also added to the front. The cast bolt details on the gun collar were removed and replaced with real 1.2M brass nuts and threaded rod and the wire eyelets for the canvas gun cover were added. Finally, the fitting for the jack block was made from some scrap brass angle.

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I had hoped to make a start on the zimmerit this ANZAC long weekend but that did not happen. Hopefully this long weekend....
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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:34 am

The Bear's Got Hair
AKA Zimmerit
Well it's taken a few weeks but 95% of the zimm has been applied to the Bear. I'm just waiting on some brass folding tools before I tackle the front fenders which are the last bits that will need zimm. I was happy that a lot of underlying detail shows through the zimmerit coating. The grey undercoat has shown up a lot of imperfections that need addressing. Many are with the resin mould itself which haven't been noticed till now.

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Sorry that the shots aren't all that good. Rush job since i haven't updated in ages
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Re: Brummbär Conversion - Repost

Post by phyrephish » Tue Mar 28, 2017 8:35 am

Well it's been over six months since my last post. Pity I don't update every time I glue a piece on or a courier arrives. Here are a few shots of the beast before the final touches get applied. Abandoned the idea of having the gun recoil so it only elevates. The only other thing of note is that the kit machine gun was replaced by one from Tank-Modellbau.

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