Kaelble Z6W2A 130 - Heavy load tractor for the WWII German Army.
Note: I would like to have url references to provide more insight into this relatively obscure vehicle, even though Kaelble made several hundred for the Germany army there isn't a lot of 'net based information available.
I've finally taken the time to put together a page for this model, the Kaelble Z6W2A 130. This was Jochen Maier's pet project it seemed to me. When I reconnected with him shortly after moving to me present home in 1990 he began telling me of his new project, he apparently had begun work on it some while after stopping the sales of him original 1/10 scale Panther A. At this time the 'net as we know it had not really blossomed and he didn't yet have a presence there and the information was limited to faxed copies of photos of the original. It wasn't until I visited Jochen on a trip to Germany in 1996 that I had the chance to see his protoype model. At that time we struck a bargain where I was to purchase a model from him at a 'friend's price' ( which was still quite a bit) however later neccessary work on my home precluded this. As often is the case way led on to way and we never revisited this and the opportunity passed. When Jochen sold his buisness later prices increased pushing the model quite a way beyond my comfort level. I later placed a 'wanted' post on a German armor forum and that turned up, ultimately 3 machines in various states but none nearly complete. Two were 'standmodell' or staic versions without mechanics and the third having a functional drive. I was able to get Jurgen Stehr to upgrade the rear axles to functional state on the first of the static models and I was able to making a functional 'diesel' engine in the same manner as sold by Hr Stehr using tandem 540 class electric motors. Below is a list of what I have thus far.
What follows will detail my work with these models. Since these are still sold by Jurgen Stehr I wish to say that any parts I may make for these are for my own use only and while I am willing to share technical knowledge gained in working with these models I am not at this time willing to sell any parts made by me which are in conflict with original work by Mr Stehr.
Two photos to start off, I'll replace these. Everytime I start a new project I have that feeling of being at the base of a new mountain looking up the side; there's a ways to go. No, I've not given up on my other projects, rather they're awaiting parts, creative urges, insights.... you know- all that jazz. Give up, never! As you recall I started a project on two other King Tigers but other things popped up with that and I gollowed a different path for a while when I thought I might be getting involved in a joint parts project but that seems unlikely now. I can work in tandem. Several of my projects have been waiting on parts or ways /means of getting/making parts to higher standards than in the past so some projects get streetched out. These Kaelble trucks will very likely be 'filler' projects and very likely they themselves will be temporarily suspended while I work out getting parts or how to make some items. The Kaelble trucks have the benefit of being electric, removing an entire layer of consideration I face in many of my glow powered tanks. In the final analysis if I want to continually engaged with a model project I have them, I'll likely never run out of things to do.... Jerry 02/22/2019
I'm busy cutting .080"(~2mm) and .125" (3mm+) aluminum sheet for the rear body of two of my trucks. Probably one of the messiest operations I've done as I'm using a Worm drive skill saw to cut the rough sized pieces/strips from a much larger sheet then using a small dremel table saw with a very efficient carbide tipped 48 tooth blade to make the smaller pieces. Messy in the extreme and I'm obliged to use both a face sheild and mask. I'm nearing completion on the first pass through the parts; next will be to make holes, openings and other facilities on the cut parts. Stehr( and perhaps Maier began this??) has made milled channels on his body parts with the intent, I'm assuming, that the parts be bonded together with an advanced adhesive. I'm not going to do that. I plan to butt my parts to each other end to surface and fasten them together with small aluminum angle and 2mm flat head stainless screws. Wherever the screw heads are visible I intend to conceal them with either a strong bonding filler or JB weld. I rather like the possibility of being able to disassemble the parts in the event of modification or repairs. I have to make my body parts smaller in those dimensions which depended on the slotted joints as I'm not using them.. Hoping it will all work well. Jerry 03/02/2019
I'm really wanting to be done with making the aluminum sheet body parts. Cutting out the parts, there are at least 21 pieces for each body super structure is about the messiest function I've had to do. I don't like it and if I could have purchased these parts easily I would have. While the major part of the work is done there's cutouts, holes and alignment slots to cut. I may have already said the original appears to have been designed to be glued together, to a greater extent something I'm hoping to avoid. Still I'm going to try cuting the alignment slots with my dremel table saw. It has zero issues cutting the .080" and .125" thickness aluminum; the carbide blade I purchased cuts it like butter but the mess is over the top. I have aluminum sawdust everywhere and I've been using a mask everytime I cut. I don't expect to have issues cutting the alignment slots that I want I just don't want to have to cut them! I think I can get away with just a few 'strategic' cuts, at least so I'm hoping... Below are photos of trial fitting of a few plates held together with cellophane packaging tape; the parts sag out of alignment quickly but gives an idea of how things begin to take shape. I'm not sure what the original owner of this Kaelble had planned for it and I've been forced to remove the servos they had mounted to operate the transmission and differentials as the body plates would not fit over their implementation. I will relocate the servos whe the body is complete. Jerry 03/04/2019
The rear superstructure/body is coming along nicely. I find using the aluminum angle with 2mm stainless steel flathead screws is working very well and is actually proceeding faster than I thought. As these pieces are copies of those that were intended to be assembled differently some fitting and adjust needs to be done but so far this hasn't been significant. Working with the thin material (~2mm) is actually refreshing, Jerry 03/06/2019
Mounted the front plate and partially the two longitudinal separators. I didn't use my usual aluminum angle as it would be relatively unsigghtly in this location. This will also be the case with other parts of the body that are fully or partially exposed. I decided the rivet in thin brass angles,one on either side of the part it is to hold however I do not fasten the held plate to these anles rather they provide a channel in which the plate may be slid into. I'll take a close up later but this also affords the ability to take out the internal member. I beleive all of them may be held in this way with some being held by mutual support and securely. More to follow. Jerry 03/07/2019.
I've been working on the two sand ballast bins on the model. As far as I can determine these were filled with sand used to give the full sized truck traction and stability by adding weight, Also I believe, however I've not been able to prove this, it was possible to empty these bins but moving a lever on the side of the rear upper body above and forwards from the wheel well. This lever, it is my contention would open a slide which allowed sand to escape from the bottom of the bin and exit between the rear wheels via a form of chute. This chute is molded into the cast aluminum fenders and it is my intent to may this eature a functional one. My last several days have been spent making the bin lids, hinges and assembling these. You made see the trial fitting of these parts in the photos below for the left side bin only. There is one thing that I should point out and that is the length of the ballast cover; it doesn't exrend all the way to cover the entire bin. This is by design but I'm not sure why as it surely looks odd or that it was a mistake. It isn't. The only reason I could come up with was to allow access to tha sand without opening the bin?? Most odd. Jerry 03192019
I've installed most of the structural members for the body, time consuming bits were making the hinges needed for both the ballast bins and the side access doors. In the two photos below the progress may be seen. Jerry 03/26/2019
Having completed most of the body work on truck number 1 I've begun constructing the body for number 2. The first part has gone very smoothly and well however I've paused at the rear plate. When I built number 1 basically ignored the fact that due to the difference between my copies and the original plates all my joints are butt type and not tongue and groove resulting in some plates being longer by the thickness of the depth of the missing grooves. This is apparent on the rear plate mostly and leaves a small gap which for some reason didn't bother me as I thought I'll just put a short section of the brass angle as a 'cap'. Well this time it does bother me somewhat. I'm planning to shorten the bed floorplate to allow the rear plate to be mounted flush. I may, and that's a big 'may' rework the plate for truck 1 the more I look at it assuming the impact to the surrounding components is managable. It's one of those things that makes me go 'hmmmm why did I do that, I know I could have figured that out before!'. Ah well, a senior moment if ever there was one; another way of describing something that had we done it in our youth we would have chalked it up to inexperience or impatient hastiness or lazy but in out later expoerienced years merely an 'oversight' brought about by temerance of years. BS - lazy is still lazy 50 years on... First things first - I'll fix truck number 2 and see how I feel. See progress below. Jerry 03/31/2019
Looking over the two body hulls I had a revelation. Sometimes it takes a while for me to see the obvious when I'm too close, standing back is one of the best remedies ever. My hulls were both the result of the way I assembled them not the way I cut the plates or lack of grooves for the T and G method of assembly. I chose to align the plates a certain way and I'm actually going forward with that choice for these two hulls. I will either use thin brass angle on the corners or I may make thin( shim stock) steel angle myself. It might raise eyebrows as not authentic but there it is. As the manufacturer of the original models called for glueing the hulls together and I've chosen stainless steel 2mm screws and aluminum angle to effect assembly I rather like the sturdiness my method provides. The addition of the angle covering the rear plate- side plate joints gives a certain level of additional strength I appreciate....I will likely extend this to also using angle caps on the assembly of the OEM hull plates if/when I assemble them. I won't be gluing them together either. Jerry 3/31/2019
The photo below is an example of what I'm intending to do. This is .005" or .010" steel shim stock cut into strips and formed into a 90 degree angle on a small bending brake. My intent is to JB weld appropriate length pieces of this on the corners when building is complete. I rather like the way these look.. Jerry
As may be seen in the photos above I've mostly finished thesuperstructure of truck 1 and the larger part of that for truck 2. My intention was to work out a way of making the rear axles of truck 3 actually function; as they are they are the static version with no internal 'guts'. The other item is to revisit the electric 'diesel' motor of truck 2 which I built but haven't finished. There are a few more details to be added including simualted wiring, a few 'Bosch' decals on electricals and the 'cooling fan'; the front of the engine has a feed through power take-ff from the main power to drive the fan and 'generator' via a pulley belt. It's quite handsome. I used information I had at hand and photos from Hr Stehr's own documentation to build the unit. I took a slightly different approach with both the motors I chose and the way they are mounted however the end result should be servicable. I include photos of it below. I'm going to finish it up then try to work out a design for the differentials.
Axles. All trucks Have some form or another. In this area I am at a loss for the terminology as to the different types. What was implemented by the manufacturer of the original models is described on their web page and in a brochure which due to any possible conflict of copyright rules I choose not to copy and display here. I should be able to reference the manufacturer's page which still fairly well reflects what is stated in the printed brocure published when Jochen Mair had first partnered with Jurgen Stehr; the brocure I'm looking at is dated 2/96 - February 1996. In this brochure there is a description of the rear axles of the model. A prominent feature stresed in words and a brief diagram is that a core element of this axle is a Zyklo-Palloid-Spiralverzahnt in other words a Spiral tooth bevel gear. The virtues of the gear are extolled, and rightfully as they are strong and quiet and very effective. Other aspects are decribed namely how this axle, actually both of the rear axles really have only one driven gear and not due to odd differential action but rather one have axle is not, normally, connected to the driven side whatsoever. I say normally because here is the trick: These axles are equipped with a lock, a very positive acting lock that definitively locks the free side to the driven side very securely when maximum traction is required.. There is reference to a 'so-called crossover drive' similar to what 'Büssing NAG also built this principle until the beginning of 1960'. .........OK. I got it now. I've posted a few photos of my foray into of of the two axles I had Mr Stehr upgrade for me to be functional axles( they had been non-functional 'static' versions) a few years back. You may still see the description of these axles here- (https://www.stehr-modellbau.de/kaelble-z6w2a-130-c-1_8/kaelble-truck-p-1?language=de) under the section "Hinterachsen". It is only available in German but if you use Google translate you'll get the idea.
The first and most glaring observation you'll see is - where's the spiral bevel gear?? No such thing here! The bevel gear used looks very much like what you'd expect to see in any decent quality 1/8 scale R/C off road car or buggy; not a machined part. The locker is a relatively simplistic steel sliding drum with two steel pins which will engage corresponding holes on the driven bevel gear; the drum is designed to slide along a key held on the half axle shaft and is moved via a brass actuating arm on a pivoting shaft. I also realized, and I'd not been told this but the axle had been delivered bone dry, no significant lubricant was to be seen in the axle. The third image above shows the initial reduction and the cone driver to the bevel gear. All beautifully executed of course but the lack of the advertised gear was a disappointment. These Axles are decidedly NOT INEXPENSIVE! Lsstly one of the two initial gears appeared very roughly cut or possibly peened. While overall the execution as I said was well done it did leave a certain taste of lacking in some ways. So now I know how these work I want to apply this knowledge to make the axles for my third truck functional. I have included a photo of my initial experiment to this end below. I have had some beautiful spiral cut steel bevel gears for many many years and I am going to see if these could be adapted. I got these many years ago when my father and I used to make weekly Saturday expeditions to ALCO Metals in San Leandro when there were mountains of diverse and wonderful things in their active scrapyard. I'd had in mind that I wanted to use these in a braked differential gearbox for a tank but as they're really too large to be practical there I'll see if I can get them to work here. I do have a backup plan aa well as a second and third backup plan beyond that. These gears, having very large bores require that I make adapters which will introduce some level of inaccuracy but I will attempt to minimize that. Beyond the gearing the remainder of the axles including the planetary out drive should be simple to recreate. Jerry 04/10/2019
I've been tinkering with the two axles over the course of the last month and as always it seems there has been drama mixed in with sadness and joy outside of the play world of my modelling activities with the worst being the loss of my old girl dog Clio about a week+ back. She was a great friend and companion ( as was her sister) for me and others from 6 week old pups up to nearly 17 years, a Lab/Pit mix and a more gentle spirit you could not hope for; she is past the fear and confusion of her failing health and joins her sister who preceeded her in death by almost 3 years.
Anyway I tried several variations of bevel gears in my work to get these axles in order. First was the spiral bevel gears I had on hand but there was too much I needed to do to/with them to get them to work and when that was done they didn't run in a manner I wished. Next I purchased spiral gears for a Axial truck variation and again and more so there was too much to do to get them to work the way I wanted and the results were not satisfactory. So I broke down and purchased appropriate bevel gear pair sets from Maedler in Germany. Gads I love their stuff! And their prices to my mind are very reasonable but they always insist on DHL rocket mail and while it's great to get them in a few days it costs... Not being in the mood to write a lot (see above) I'll let the photos do the talking but this is a work in progress. You can see the bevel gears, meaty pieces, the reduction gears and the keyed sliding lock that will lock left and right half shafts on demand when finished. According to the documentation this is a mechanism in theory similar to one used by NAG-Bussing until the mid 1960s for heavy trucks. In the two rear axles only two outer wheel pairs are to be driven under normal driving conditions: the left side on one axles and the right pair on the other. Once locked all four pairs are driven. Turning must be problematic but the wheels are also to be driven by a planetary gear set in the inner hub. Jerry 5/5/2019
I've been making slow if not steady progress on the axles for my third Kaelble. They are a lot of work but in the end not THAT much. I've made the out flanges that mount the planetary( epicyclic) final drive to the wheel pairs. I have one axle nearly complete as I write this. Adding the epicyclic gearing has been a challenge. The gear layout is deceptively simple in appearance but in execution, planning not so much. You'd expect the planet gears to simply be laid out at 90 degree intervals, given set gears of a given pitch, tooth count, pitch diameter and tooth angle.. You'd think that. Yet it isn't that simple. I found that the math behind working out a epicyclic isn't trivial and tooth profile standards even come into the mix. Let me say I had to fudge two aspects of my implementation. I purchased high quality gears from Madler as may be seen and these likely worked against me in this instance... Suffice to say I have one axle completed or nearly so and I'll be happy to see this part of the work in the rear view mirror...! Jerry 05/28/2019
I have most of the work completed on both axles. I have to say making the planetary drives was more work than I expected and I know my implementation is not optimal but they do seem to work well. I was somewhat disappointed that even though I was careful to purchase what I thought to be identical parts to the OEM ones the fitment was extremely tight, unpleasantly so even though rudimentary calculations demonstrated that the pitch diameters, tooth counts and placement on the planet gears was correct the results were not as expected. I can only surmise some sort of different tooth geometry was used in the OEM implementation. I don't want to have to do these again! Nor determine replacements for an original.... That all vehemently laid out except for sealing the units, making the universal ( Cardan) couplings and finalizing the driven spiral gear pinning these are complete. I spent some while making the universal parts and now I'm waiting on some specialty end mills to finish these before I can finish the milling and assemble them. I fould a very nicely made driveshaft made for some offroad truck, I believe 1/10 scale. It is very nidely made from what appears to be stainless steel. Cleanly machined with an impressively machine spline allowing a degree of telescoping; they maker even chose to use tiny circlips to retain one of the cross pins which allows the units to be dissassembled for modifications or maintenance. I'm glad I found these as it's saves me a boatload of work or at least should do. After all the hours of machine work and fitting I've done so far I feel a little guilty that I actually found an 'off the shelf' item that looks like it will work. My little Canon camera has a tough time with focus on complex parts so please excuse the blurry photos Jerry 06/13/019 >
As I mentioned previously I purchased a transmission from a fellow in Germany, very good luck that was. I do believe this unit was examined by the previous owner and possibly at least partially disassembled. When I put oil in it it did not hold it well. That and another thing I noticed while determing how to mount this thing to the frame of the second truck is that there are no mounting holes on the gearbox body! These two factoids regarding this gearbox prompted me to want to disassemble this unit to reseal the entire AND make the required mounting holes. Also as an added bonus; since my third truck will need it's own gearbox and since I have a set of machined gearbox castings I'm thinking I might borrow some ideas to help make a simplified version to use in that truck. More to follow on this. Jerry 06/13/2019
The transmission is in pieces now on my work bench. I'm trying to decide how I want to proceed in making the third version. I see now how the thing should work but there remain questions as to why the method I see for engaging the gears was implemented as it was/is. The gears and drive dogs are cut with curious angles. As I'm no expert or even have experience with automotive or other relatively advanced gearbox designs this may well be a normal, 'standard' method. I've thought I'd use steel pins( dowel pins) and holes to effect engagement but I have to believe the method chosen was for very good reasons. I'll post photos of what I see..Jerry 06/24/2019
The photos below show the details of the gearbox. There are some 18 gears and some dozen ball bearings. I'd like a simpler version; I don't believe 10 speeds are really needed but in fairness I don't have any experiece operating one of these models. In two of the photos you may see the gearbox housing - before and after without and with the four threaded mounting holes. Adding these was really my initial purpose for dissassembling this unit; that and the fact that it leaked oil like a sieve. If you look closely at the perimeter of the top cover (or 'lid' if you prefer) you will see vestiges of the lacquer-like substance that was used to seal the unit. Before I reassemble this unit I will thoroughly clean all parts and faces and then I will reseal it as I reassemble it. I was surprised to find that the main gear clusters ride on brass shafts no bouby to minimize friction. I imagine this was simpler than making the shafts of steel and provide the movable (selectable) gears with brass or bronze bearings. More to come. Jerry 06/26/2019
I'm going back to the rear axles to finish up some of the items that needed doing. I was awaiting 2mm endmills and 2mm harded steel dowell-pins. I made the universal assembly that joins the two together. The axles on the right has a single 2mm spline that locks the axle input/output shaft to the universal but allows for easy removal. The left axle's input shaft has the universal pinned to it, permanently attached. I'd made a number of universal parts, enough to made 5 or six regulat unions and a couple of the double versions seen here. I didn't really need them all but is seemed silly to set up my machines just to make 2 parts. Next I need to more securely attahed the larger driven spiral bevel gear to its shaft. Lastly I need to install a o-ring oild seal to prevent the locking arm shaft from leaking lubricant then seal the axle housing parts to prevent leakage. I plan to use Maier's original mathod of sealing using lacquer or lacquer-like material. I found silicon rubber isn't as good as you'd expect. Jerry 07/01/2019
I have adjusted the connecting universal to attach to the forward axle more securely. To assemble the two I've found it's better to connect them to the central arm assembly along with the control arms before attaching the completed assembly on the chassis. There are just too many pieces to keep aligned otherwise. I also came across an issue with the forward axle in that the input shaft was able to move forward ( it runs straight through the body) so I made a small retaining collar and implemented it and an additional bearing on the inner side to support it. This prevents any excess movement and protects the pinion gears. I did implement a large hardened pin, retained with a set screw to fully lock in the driven spiral bevel gear. I lubed the assemblies with moly grease, sealed the casings on assembly with laquer. I tested the axles under power from a srong cordless drill and they performed perfectly including the operation of the lockers. I consider these complete. Jerry 07/07/2019
As seems to be the case more often I'm spending as much time making specialty fixtures and tool/cutter holders as actually using them. Work on the transmission for my third truck I found that I can only do so much with gears I was able to purchase from Maedler. The transmission requires 0.7 module gears and several are of a configuration I assume are 'custom' made. In order to replicate the function and since I could not find these gears anywhere I looked I needed to make these gears myself. I've had gear involute gear cutters for some while but always rather use off the shelf gears which are usually available. No such luck this time. Not having an appropriate arbor to hold the cutters of this size I needed to make one as well as a mandrel to hold the blanks.
The first photo shows the gear blanks, the second horribly blurry photo shows cutting and the third the cut gears. The forth also blurry photo show the trans in progress with three of my cut gears in the middle of the top three shafts. All the other gears are from Maedler. The last photo is just me closing up for the night putting on the trans cover; there is a lot of work yet to be done and I'm waiting on a tapered end mill to arrive.( to cut the selector engagement teeth).This little unit has been a lot of work but I've learned quite a bit. Jerry 07/22/2019
I've just about finished the transmission. I had to wait for some 7 degree tapered endmills to cut the drive dog engagement features on the gear selectors and gears. This wasn't terribly a lot of fun as these parts were difficult to hold while cutting. There are a few things I will want to revise at some point as the alignment of some of the gears, face to face is offset a bit and one gear I should probably remake as it is noisy. The gears on short output gear shaft are merely press fit, not pinned! I realized I didn't do this last step until after I sealed and assembled the unit. They might be slipping but I'm not certain. Fortunately it isn't so much work to disassemble and reseal. The last piece I was waiting for is the 4mm ball plungers(they look like set screws but with spring loaded balls protruding from one end) that are used to keep the gear selectors in place until you need to move one. I just implemented these this evening. I've testing the gearbox multiple times and while it's a bit still in some ways it actually appears to work reasonably well. I need to finalize a few things but still I'm going to consider this complete. I also reassembled and sealed the OEM unit I had which actually needed a modified pin on one of the internal shafts, while testing the unit this pin cam out of a gear and jammed itself in another gear which I fear suffered some damage because ot it. This was not a part I had disassembled so I don't know why the pin was loose. Upon reassembly the unit seems to work as expected so hopefully that's the last of it. with the completion of my third transmission my three trucks have complete drive trains with the third truck only needing an (electric) engine to be complete mechanically. I plan to make the required drive lines to connect the rear axles to trnsmission for truck 2 and 3. Truck 2 already has the transmission and engine coupled together and tested together. I did have to modify the output of my self made engine to have an appropriate coupling for the transmission. I must remember that the axles of truck 2 need to be disassembled, cleaned and greased reassembled and sealed as none of this had been done by the maker. I was pleased that neither my self upgraded axles nor either transmission has leaked a drop since reassembly and sealing. Sokme of this latest work I've described you may see in the photos below. Jerry 08/08/2019