A herd of PzKw III!
I've been away far too long.
My involvement with panzer III types began nearly 27 years ago before I moved to my current home and decided I wanted a StuG III, a later type. Once I built the basic model I've not touched it since. Over the years I've collected the makings to 4 additional Pz III type models. The total beginning with my own scratch built which I've listed below:Panzer III types in the list
It's not like I don't have anything else to do! My other projects detailed on this site are not exactly finished! However it is more out of fear that if I don't move these forward there's the real danger of misplacing critical small parts. Make no mistake.. to finish 5 models or even to get them on their own tracks will be daunting...even my own scratch built will be reworked somewhat. The first order of business is to make/ or remake all 5 hulls as strongly and as uniformly as possible, much of the models I purchased in Germany ( ebay) were expoxied together - that has to go. I alsdo spent a goodly amout of time cleaning up 140 Pz III wheels casting I have in order to begin assembling them PLUS I made two rubber tire molds.. ....that's all for now... more to follow soon.05/28/2016. Jerry
I had actually done quite a bit of work on the Pz III family since I wrote here last. I have many photos and much to tell of what I've done. I should also say since last I wrote I've also retired! I am free! How cool is that right? Jerry 02/16/2018
As I mentioned the first thing I tackled was the 120+ road wheel castings and rubber tires. My goal was the make them as nearly identical to each other as possible. I say this as I did not cast these , don't know who did them all( some where from Thomas Wittgrebe) and there were variations. This represented days of machining so I could fit bronze bearings to them. I also made 2 vulcanizing rubber tire molds, magaing to crack one as I attempted to compress raw rubber into it before realizing I hadn't made expansion vent holes. The wheels are finished to the point of mounting but I still need to make and mount covers( hubcaps). I will make a die to press these from thin steel or aluminium.
The next parts I tackled were the final drives. These turned out to be a mini-project in their own right. I made a decision that I wanted the drives to actually be functional meaning they would have an actual functional reduction gearing. The housings went through two pattern revisions so I actually cast the parts twice to produce 10 finished drives. First to be cast were the sprocket bodies, I decided these were to be used with actual tooth rings as the originals. I actually used my original pattern of 28 years ago after I trued it and modified the profile and shape. See below. Next were the sprocket rings. Jerry 02/17/2018
Once the sprocket bodies were machined and assembled and trued, as much as possible I decided how I wanted to make the toothed ringed to engage the tracks. Here was a decision point. I knew I was to use two basic track types or rather materials; aluminum track from Thomas Wittgrebe and bronze tracks from Geisswerk. The bronze track need a steel sprocket ring, aluminum will not be strong enough. When I purchased the track from Geisswerks I also purchased the sprocket ring blanks. But I hadn't enough for the aluminum tracks so I decided to machine my own. I later purchased a full twenty steel sprocket disks but only used enough for the bronze track. My stubborn streak had me use my own for the aluminum track. To macine the blanks into the rings needed I made a crude but very effective fixture for my lathe that allowed safe machining of the disk while fully supporting it once machined. This was particularly important for the aluminium rings as they in their final state seemed to be fragile although once mounted to the sprocket body this didn't seem to be the case. Below are some of the steps I performed on these
While I was pleased with how my self made sprocket rings turned out I was ultimately disappointed by the error I introduced into some of the parts by being too aggressive when drilling the bolt holes in the disks initially. The small drill wandered sufficiently to make several disks unusable. I will likely use these as carried 'spare parts' aboard the tanks as I've seen photos that support this. It can't be readily seen in the photos but those showing the teeth being cut actually represent multiple rings at once. The more successful runs was where I limited the number of disks to 4 at a time. Not from the tooth cutting but rather the hole drilling. Also I think I used two different alloys as I generally use what comes to hand in my shop. It was a very useful experience especially making the fixture for holding while machining as I will be doing this again as I get to other models in my queue of which there are a growing number now thanks to Christian Ludwig's ability to deliver 1/10 scale plate kits, Geissworks tracks and a laser cutting firm I found who will deliver stainless steel sprocket blanks at a very reasonable cost given proper drawings! You should be able to pick out the different materials in the photos, steel and aluminium for the sprocket rings. I was concerned with maching the stainless steel rings as stainless is notorious for being cantankerous while machining but it all came off quite well. Jerry 2/17/2018
The next section will discuss the effort I follwed to make the final drive housings. As I mentioned earlier I decided that I wanted these units to be self contained components to simply be located in the right position on each model and then bolted in place more or less like the originals. To be included is a 3 or 4 to 1 reduction gear I believe I settled with a 4:1 ratio. For the pattern I used some parts that had been included with one of the parts lots I'd purchased years back but with significant modifations. As I also indicated above I revised these patterns twice and below I will show what I did and the considerations I had to take into account.
In building the final drives I had to consider the spacing in the sprocket with respect to the tank hull- this spacing is critical to the proper 'tracking' of the track and if incorrect by any significant amount would contribute to the model 'throwing' its track particularly under load and during turns. This spacing, assuming the sprocket itself is made correctly is primarily influenced by the thickness of the final drive housing and associated parts. As many of you know I generally do not work from prints but rather sketches and simple drawings I make as I go. I wish I did have prints. I realize I could make them using any number of CAD programs but even though I've wanted to learn one of them I've never sat still long enough to do it. So I continue to use my tried and true methods.
Below a test part I did casting the brass bearing into the casting directly. I decided I didn't like this
Next two photos show castings still in the sand
Next several photos show brass bearings in place and beginning machining operations.
Next photos show bolt pattern holes drilled. I made a special counterbore to machine the flat bolt head recesses. Also made a steel drilling template to drill all the mounting holes the same( except for first parts).
The following photos show making and installing the support bearings for the pinion gear shaft I used a very fine thread for the bearing shell mounts.
I used a keyway broach to cut the keyways on the driven gears and a woodruff ket cutter for the output shafts. The keyway in the gears may be seen in various photos. One of the other decisions I'd made early on was that the sprockets would mount on the final drive output shafts in a way similar to that of the originals meaning the twenty bolts on the output shaft 'flange' would do actual work. These are 20 1-72 stainless steel screws and I think they will be strong enough! I am skipping ahead to show the final drives in nearly complete form with one mounted to show essentially the progress up to the point I stopped in August of last year. I made backing plates to which I could also attach support beaings for the driven and pinion gear shafts. I also have a short video of on drive under power using an cordless drill. I have moved on to making the idler wheel assemblies and that is where I am beginning to get traction. Jerry 02/18/2018
Compounding my current struggles in focusing is the realization of how much work I yet need to do. I have also supplemented my cable TV with NetFlicks and Amazon Prime this past year- there is so much wonderful content there!! I find myself curling up on my sofa after dinner and bing watching then falling asleep getting nothing done on any project! I am struggling with the idler wheel assemblies. so far I have made the mounts, arms and the wheels of course; the wheels are from the best of the castings I had. I have made 10 assemblies so far with two having cutouts for the wheel axle. On the other end I have the tow / tension adjuster bracket in the works as well mostly as semi machined castings. See the images below. Jerry 02/22/2018
Cutting one of the last tension adjustment/ tow hook brackets
Baby steps. made some progress on the idler assemblies. I proceed slowly with these as I don't want to remake them or make mistakes I'll pay for later. One example is this. When I attahed the mounting or main shaft to the arms I silver brazed them with an idea to running a pin through them later that would also catch the adjacent shaft for the idler wheel itself pinning them both. I still may do that however when fitting a snug idler shaft I tapped the assembly on a steel block on my workbench. To my horror the main shaft snapped like a twig! An 8mm steel shaft. You guessed it I cooled the braze joint too quickly embrittling the shaft. I hastily annealed the remaining parts. One has to think at every step. See the progress below. Jerry 02/26/2018
I wanted to test out assembling the idler wheel shaft to the tensioner arm. I debated how I would attach these as I brazed the tensioner shaft and was concerned about fiddling with the hardness of the assembly again. I decided that nothing satisfies like a good old fashioned rivet so that's what I did: I riveted the idler wheel shaft to the tensioner arm. I prepared one assmbly and liked what I saw so on to the 9 others. I used steel washer as spacers and also cut grooves on the idler wheel shafts to use "C" clips to serve as retainers. After this it will be cutting the pivot point and making the connector for the threaded adjusting point and the threaded tension adjuster. Jerry 03032018