Early Tiger 1 from sPzAbt 503

[mrTyko]

Aha a 3d printer, I want one also.

Really well done.

Ha en bra dag
Robert

[cahlfors]

Indeed, MOSFETs is what it took:

The Benedini smoke controller is doing the basic control. I turned up the sound rather high, so you would not hear the grinding noise from the chinese geared fan motors. There is one motor per fan and they have a built in gearbox. They sound pretty much like an electric pepper or salt grinder. I may have to replace them with higher quality later on. Also, the rpm control is rather simplistic currently but, as usual, I may get back to that later. There are more important things to do first.

My first CAD project was the pistol port. Then Mike Stannard released his version and my unfinished CAD model was set aside. However, Mike's port is not quite correct. He said he made it so you could screw it to the outside of the turret wall and thus it's too thin. It's too thick for that, actually. The result is that a compromise had to be made with the port opening. Mike elected to keep the angle of the leaning port walls correct, but then the inner hole becomes too big. You can see it compared to my 3D printed part in the correct thickness below:

My rivets may be oversize, though. I didn't have any measurement of them and went for visual appearance. Now I see they come out marginally bigger than Mike's, which are probably correct.

Naturally, on tigers it's mounted on the port side:

I am happy with it for now, but of course, this is only a plastic prototype. It has to be metal, eventually!

Thanks for following this very slow build!

/Chris

[mrTyko]

It is a privilege to follow your building

Lovet the video of the fans.

Robert

[cahlfors]

Thanks Robert!

/Christoffer

[cahlfors]

Despite the lack of updates, there has been plenty of action in the workshop. The latest major project has been upgrading my mill to CNC.
The first CNC project was fabrication of brass hinges for the deck hatches. A careless turn of the turret crashed the old white metal ones (again...). A before/after picture would have been something here! But a hinge is really not that interesting. It was a mere warmup for more interesting things.

The second project became making something more permanent with the pistol port. A plastic prototype is just that: A prototype. Here comes the real thing:

Work in progress...

The finished part:


I am happy with the result and although I crashed both material and tools to make it, the concept of CNC has proved itself. This part could not be made by hand milling.
Oh, and I can delay the procurement of a lathe. Looks like I can make it without one!

Cheers,
/Chris

[mrTyko]

So beautiful that I get tears in my eyes.

[Hans K]

Ett mycket snyggt jobb.

Hans K

[Nafets]

[cahlfors]

Oh, wow, thanks guys!

I have also been expanding a bit on my CAD skills. In FreeCAD, it is pretty easy to do amazing things in 3D. I think I am over the hurdle now and somewhat productive. The next challenge was to see what could be done with the hull MG ball mount. I knew there was something wrong with the stock part, but not quite what.

Here are a couple of prints in different resolutions together with the stock part. The difference becomes obvious.


I am still not sure about the exact shape and size. It is modeled from Jentz & Doyle, but their drawings do not have the wedged cutout at the bottom, so theirs must be a postwar reconstruction...
Also, their drawings have no measurements. Does anyone know the size of the ball, for instance - that would help a lot?

Another area of doubt is the cutout for the watertight cover. It seems shallower on both the Bovington and Munster tigers. Especially the Munster one that I took closeups of, but there might have been a lot of rust on it when they found it.

While experimenting with different print settings, support and stuff, I found myself running really old slicing software and upgraded it. There is now support for variable layer thickness. I had first failed miserably with a print of 0,05mm layers that took 12 hrs to print. 0,1mm works fine, but 0,05 is a disaster. It should not be, so I started investigating. It turns out that the Z-screws have an increment of 0,8mm per turn. Divide that by the step motors 200 steps per turn becomes 0,004mm per step. The layer thickness has to be a multiple of that, meaning that 0,1, 0,08, 0,06 and 0,04 are all okay, but 0,05 leads to uneven layers, which might be what I saw. Anyway, the variable layers were a blessing for the ball mount, since there are some very shallow slopes that makes the different layers very visible, requiring thin layers, and at the same time plenty of rather vertical slopes where layer thickness is secondary. The final print has the lowest layers 0,2mm, 0,1mm in the middle and 0,06 in the sensitive top areas.


It came out okay in my thinking. The fill around the top is because the cutout is too high on the model. Possibly, there is a size difference as well. There is now, anyway.
This is just a plastic prototype, but I expect it to sit there for quite a while, before I have bought a CNC-controlled round table and can mill this part in aluminum. Maybe there is a way around that, but it depends on the necessary depth of the cutout for the water seal. My current software does not allow undercuts...

In all, I think it will at least spawn some discussion at coming events.

Cheers,
/Chris

EDIT: Gee, I see now that these photos are pretty revealing! There are details I can not see with the naked eye. Oh, and I got the ball in tilted! Ha ha!

[cahlfors]

For quite a while, I have known that I need to do something about the suspension. I broke it pretty much from the very beginning, but it is not until now that I have a plan on how to fix it. The newer models have an adjustable suspension and I figured that would take care of all possible issues. No matter how careful you are, things either change or do not come out quite as planned and that is where an adjustable suspension shines.

So, off with the tracks and look what I found!


The model is listing forward and to the left. Some torsion bars have worked themselves loose in the fixed end. This is part of the explanation...

The new suspension will be adjustable from the outside, which is good for me, since removing the batteries and stuff inside, is something I really want to avoid. On the other hand, adjusting the new suspension will require removal of the tracks and road wheels. This is something I do occasionally to reglue rubber tires that have worked loose. No big deal.

Work started with emptying and cleaning out the hull. After quite some mileage, this was a good thing to do. The right side is cleaned out and the right suspension bar removed for processing:


The fixed end of the torsion bars will have a bushing similar to the one in the moving end, with two grub screws to hold it instead of one in the old fixed end. The single grub screw would eventually eat its way into the torsion bar and the preset angle would change accordingly, leading to a sagging suspension. The new bushing will be fastened axially from the outside. Adjustment wiill be done by simply loosening the screw from the outside and turning it to the preferred angle and then torque-tightening. I have tested it in the bench and it works nicely.

I made the new bushings in the CNC-mill rather than in a lathe, simply because I do not have one. It took forever, buit it is possible to do....
This is what they look like:


The right hand suspension bar has had recesses milled out for the new bushings. Here the bar is installed again with the new bushings:


Phew - halfways!

/Chris

[Ragge]

Some Dark Yellow on the outside this time ???

[Nafets]

Some polish

[cahlfors]

Holy cow!
That sure is a piece for the living room!

Makes mine look like something out of Kelly's heroes...

Anyway, I have tons of work to do before I am anywhere near painting...

The whole day has been spent hard working in the workshop with the milling machine, watching it making holes...



With the new bushings, the torsion bars need shortening slightly. A few have been finished and test fitted. Looking good so far, but the real test comes under full load.

/Chris

[cahlfors]

Both sides now done, torsion bars shortened, with new flats filed and assembled:



Filing flats on the torsion bars is really cumbersome. Not the actual filing, but finding out that the bars twist in the bushings despite the grub screws holding them and trying to tighten those grub screws enough without slipping. Quite annoying...

Anyway it is done now and the suspension is adjusted and test loaded.

Next is putting the interiors back in and fiting the tracks and we are done!

Too bad winter is over - driving in the snow is great fun!

/Chris

[cahlfors]

While I was at it, I decided to disassemble the final gear housings. They have never been taken apart before, so I figured it might be time. After cleaning up, it turned out that things were in mint condition!



There was quite some goo in the gears. I think at time I built this model, the instructions were to add a minimum amount of lithium grease and I suspect what I cleaned out was the rest of that mixed with metal powder from the gears wearing in/polishing the teeth against each other. The current instructions are to leave the gears dry, as grease assimilates dirt and becomes a grinding paste. I put some dry PTFE lubricant on them and reassembled.

/Chris