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Hi All,
Update 19 Feb 23
Front plate.
Weld detail completed Driver’s visor side blocks trimmed to allow for weld Exhaust
M3 nuts fitted to new top pieces in readiness for threaded rods. Smoker electrics
As mentioned a while back I am installing dual bespoke smokers based on the Benedini design. It is now time to consider the electronics that will drive them. Each smoker will have two pairs of 24V elements to give ‘idle’ and ‘max’ smoke generation. The units are fitted with 12V four wire fans so that I can control the speed via a microcomputer (Arduino Nano). I have laid out the electronic components to see if they fit in a standard Hammond enclosure... As you can see the design features: four dual MOSFET trigger switch drivers (3.3-20.0V trigger voltage, 5-36V operating voltage, 15A 400W output); two XL6009 DC-DC stabilized output voltage buck/boost converters (5V-32V input, 3V-32V output) which will be adjusted to deliver a steady 12V for both the fans and the Nano. The plan will be to have the Nano read a copy of the throttle signal and vary the fan speed and switch on the heaters as appropriate. The RC signal will be mixed with a switch position so that I can disable the smokers from the transmitter. I may also use the thermocouples supplied with the current/voltage sensor to monitor the smoker boxes and disable them if they get too hot. This sort of thing should be possible using OpenTX/EdgeTX

That's all for now...
Alastair

Hi All,
Update 1 Mar 23
Smoker electrics
Having positioned the electronic components it is now time to solder up the wiring... MOSFET switches installed...note use of common ground point to reduce amount of wiring that needs to go to microcomputer. (Steel M3 bolts will be replaced with nylon ones to insulate the point from the metal box.) Voltage regulators installed to ensure a steady 12V from the battery (can vary from 14.4V to a minimum of 10.0V) Nominal 12V input wiring fitted. Even though I am using XT30s you can see that I am not using the polarity provided by the plug. This is because they are identical circuits, the positive lines come from the fuses at the rear and the negatives go to the common ground at the front of the tank.

Installed a box to house exposed circuit boards, such as Beier USM-RC-2, and keep them safe. As mentioned earlier I want all the internals to be capable of removal so that I can get to the torsion bars should the need arise. The wiring is getting rather complex so I invested in a label maker... This model can print on to heat shrink tubing... That's all for now...
Alastair

Hi All,
Update 7 Apr 23
Exhaust stacks 14mm OD/10mm ID PVC tubing epoxied in place. Brass tube inserts used to align tubing whilst glue cures. Test fit of upper tube and top detail piece. Exhaust assembled and awaiting filling and texturing with Mr Surfacer. M3 cap head bolts used to protect thread for now. Texturing almost complete, time to fit the mounting flange. Brass tube will be pushed in, when glued, to help lock the parts together and provide additional strength.
Trial fit of completed stack (top plate detail to follow later). That's all for now...
Alastair

Hi All,
Update 14 Apr 23
Finishing the smoker electronics...Wiring complete: Next job: set the voltage regulators (buck/boost) to deliver 12V. A 13.8V bench supply was connected and the trim pots adjusted until a steady 12V was output: Programming the Arduino Nano.
First, I wrote the code to trigger the heater elements at specific throttle positions. The code was tested with LEDs as substitutes. Once again, the bench power supply was used with the regulated 5V pin on the Nano powering the RC receiver whilst a 12V feed from one of the regulators powered the Nano. Then followed code to control the fan speed with the same signal. (The fan speed is a linear function of throttle position. Although I arranged for the fans to run at a low speed even with zero throttle, -100%.) Once happy, the Nano was installed... ...and the enclosure closed up: Note: enclosure ends are not currently secured, just in case some reprogramming is required.
That's all for now.
Alastair

Hi All,
Quick Update (26 Apr 23)
Armoured exhaust covers
Lift pegs epoxied in place and weld detail added: Manufacturer (Henschel: DKR) and year (1943) casting marks added using Slater’s 5mm Plastikard Letters and Numerals. Followed by what I have assumed is the part number (021-?-2701-162): Then several coats of Mr Surfacer to blend the markings and add some cast texturing: Will probably add some more coats before applying the red primer.
That's all for now...
Alastair

Hi All,
Update 19 May 23
Finishing the hub details...
Sprockets:
Copying an idea seen elsewhere on the Forum, I made a boss so that I could secure the sprocket hubs using the central cone bolt. I started with 10mm A/F hexagonal bar stock, which was machined down to 5mm diameter on one end. Then a M5 thread was cut with a die, whilst the other end was drilled and tapped to M3. Boss in situ: Hub cover trial fit: Road wheels: Basic 3D printed parts Custom etched brass lock plate and 10BA bolts fitted. (I have some spare sets of the lock plates if anyone is interested; please PM.) Shown here with fitting/removal tool, which contains an M4 cap head bolt for strength. Trial fit, just needs some primer and paint.

Finishing the exhaust pipes:
The top cover supports were made from 3.2mm (1/8) brass rod that had an M3 thread on one end and were drilled and tapped to M2 on the other: Trial fit of cap, ready for primer, paint and rusting up... That's all for now...
Alastair

Hi All,
Update 20 Jun 23
Radiator fans
The 3D printed fans were designed around a Pololu hub (product code 1996) that was intended for a 3mm shaft. The stepper motors I chose (Pololu product code 1204) have a 4mm shaft. After several failed attempts to open the holes out using gradually larger drill bits, I decided on a different approach. (The drill bits would not cut into the existing hole exactly on centre even though the hub was secured using a collet in my mini lathe.) Therefore, I drilled and tapped the hole for some M6 threaded brass rod, secured this with thick CA, squared it off and then redrilled the hole using a 1mm/4mm centre drill on the lathe. The drill bit was driven in until a short length of 4mm hole was produced. This enabled me to centre up a 4mm drill to finish: The headed hole for the hub retention grub screw was drilled through and tapped for M3. As the hole was already there, I simply used some 2.5mm drill rod (drill bit reversed in chuck) to centre it on my mill.

The electronics will be distributed with the controller in the front and the drivers (A4988) close to the stepper motors as there is a convenient space where the radiators would have been. I decided to use Perma-Proto board so that I could simply copy the layout from the prototype... One of the two driver boards (front side). Notice I will have the boards permanently set for 1/16 microstepping. Rear side Controller board featuring a Teensy 3.5 and a socket for a 5V voltage regulator.

Road Wheel Hubs Primed and ready for base coat Base coated to match wheels, ready for weathering. Basic weathering applied and matt coated to protect paint finish during fitting. Similar treated applied to sprocket hub caps.

Hubs installed... Finished look. (May apply more weathering when hull finished) Reference image, I am pleased with the match. That's all for now
Alastair

Great update as usual Alistair.
Any particular reason for using 1 / 16 microstepping?

Vince

Thanks Vince.
The NEMA8 stepper motors are quite low torque so the maximum micro-stepping available was selected as an attempt to reduce the acceleration on start up. This will hopefully reduce the likelihood of stalling. A Teensy microcontroller was also selected as there is code available that will generate sufficient steps/sec to give a realistic RPM whilst limiting the acceleration. There are 'stronger' NEMA8 steppers available now so an upgrade may be required...

Alastair

That makes sense. I guess those nema 8 steppers can't handle a lot of current.

Vince

Hi All,
Update 9 Jul 23
Radiator Fan Controller
Time to populate the enclosure... Breadboard installed along with a 12V relay onto an ABS sheet. The relay will be activated by a signal from the Beier soundcard (USM-RC-2). The relay can operate with the nominal 12V supplied to both COM and VDD, so a binding post was added. Wiring almost complete.... On the left
Red & Black 18AWG 12V supply from service battery.
Yellow & Black 22AWG throttle signal from Rx (FrSky Archer R10 Pro).
White & Black 22AWG switch signal from Beier USM-RC-2.
On the right
Two pairs (left fans and right fans):
Red/Black/Red 22AWG 12V and 5V supply to steppers and A4988.
Two pairs of two pairs (one for each A4988), only one pair in place
Green/Blue/Yellow 22AWG Enable/Direction/Step signals to A4988. Enclosure fully populated. Note the M4 button head screws for affixing the box into the Wanne. I intend to place it underneath the busbars that take the 12V supply from the service battery and send it to the on/off relay, the charging point and another set of busbars for distributing the supply to the various services (Beier USM-RC-2, smoker controller, radiator fan controller and RC receiver)

Recharging points
I decided to access the recharging points for the 12V batteries from the Radio Operator’s hatch as the Driver’s hatch is used for the service ON/OFF, power ON/OFF and JOIN/SPLIT switches. Recharging points mounted on Speed Controller plate, next to service distribution bus bars. Checking access through hatch, looks OK.

That's all for now...
Alastair

Hi All,
Update 20 Jul 23
Radiator fan control (part 2)
Enclosure labelled... Note that the wires have been twisted to reduce chance of interference.

Power electrics
I have got around to making a cover for the 24V power circuit distribution busbars as they were a little exposed. I used some more 1.7mm thick ABS sheet, which was doubled up for added strength. Note the use of extended securing fasteners to provide support for the cover. Cover in place, the busbar terminals are now shielded adequately. Cover separates the positive and negative terminals. Supporting fasteners will be isolated using rigid PVC tubing.

Exhaust
Trial fit of exhaust pipes and laying out of smoker tubing Both stacks in place. Armoured covers fitted. Right-hand smoker unit in position Smoke tubing roughed out... needs support at second elbow to ensure pipe run rises gradually to outlet.

That's all for now...
Alastair

Hi All,
Update 2 Aug 23
Firewall
Beginning to detail the firewall as I am starting to fit-out the engine compartment... Vent detail added... decided on the second type (out of three) rather than the initial design as I figured it would have been modified when the HL230 P45 was fitted. Painted ready for installation. Close-up of vent, just needs a bit of weathering.

Bow MG Animation
Custom support and servo mount (servo is a FrSky Xact H5701)... Servo horn linkage... In the end, I decided to use the outer most hole (opened out to 2.5mm) to get more travel. Mounted in position. The MG34 is located using the hole for the optics.
Next job... fit the gun barrel and muzzle. Test fit... Muzzle and flash hider dry brushed with gunmetal. Driver’s vision port
Have been working on an appliqué part to mimic the driver’s direct vision block and armoured visor control unit. It has been designed to fit around the existing fixings although the ones for the lower part of the visor were replaced with countersunk screws. 3D printed parts with ‘fixings’ secured in place. Painted, ready for installation of vision block, locking levers and control wheel. Just needs a little weathering (dry brushing) before final fitting. Some subtle light grey and gunmetal dry brushing applied. I will apply a pin wash around the visor parts before installing this detail.

That's all for now.

Hi All,
Driver's Direct Vision
Update 17 Aug 23 (4 year point)
I did an initial pass of pin wash to weather the front weld before installing the driver’s direct vision system: Interior view Exterior view, note that the vision block is translucent Rear electrics Final configuration of the plate. Holes cut/drilled for the receiver voltage regulator and to allow cables to pass through to the underside.

Radiator covers Fan cover latch clip (from Sixth Scale Icons) test fitted. Photographs of surviving Tigers showed that the clip had a lipped base. I assume this base made it easier to weld the clip to the armoured cover. Image shows the first attempt to size this feature. I ended up making the plate square and moving it slightly further back.

Decided to reprofile the covers... Insert epoxied in place, note the roughened surface to aid adhesion. First pass with Milliput. Second pass with Milliput, sanded ready for Mr Surfacer 1200... First coat of Mr Surfacer 1200. Another coat, after sanding down the first. Final coat (fourth I think) ready for some cast texture. Will do this when other holes have been filled.

Electrics (final fix)
Having acquired some light strength (Purple) Loctite I have started to refit the electrics/electronics... Ready to refit speed controller, relay switches and charging jacks... Front plate installed... Electronics refitted.

That's all for now. Next job... plumb in the smokers and fit dummy lower fuel tanks.

Hi all,
Update 21 Sep 23
Lower Fuel tanks
As you may know from earlier posts, I plan to have a fully detailed engine in F01. I want to able to remove it for display but have something reasonably prototypical left to look at when the engine is removed. I have decided therefore to include the lower fuel tanks. These will have added bonus of hiding the plumbing for the smokers and the wiring for the radiator fans. Right tank tension strap detail (0.5mm rivets, 1.4mm threaded rod and M1.4-2.0mm A/F nuts) Straps for left tank and fuel valves. Lining up the strap ready for 1.5 x 8mm dowel pins. Straps fitted Valve detail dry fitted, ready for painting. Will be primed in black and then sprayed with some metal colours to simulated aged aluminium.
The aim here was for something that had the ‘feel’ of the full size item without going too far with the accuracy. Hence the lack of heat shields which would make the tank less interesting to look at.

Radiator Fan Electronics Stepper motor driver board installed and motors wired up. Fan blades installed, will require some additional hub detail.

Turret Rotation Electronics
Started on the turret rotation electronics. I want to have position feedback so that I can stop the rotation when the main gun gets close to the radio antenna. On start-up, the controller will ‘assume’ the antenna is fitted. A switch will need to be set in order to get full rotation. I plan to use a three-position switch on the transmitter so that the third position can be used to set the current azimuth angle to zero. This will enable me to ensure that the correct zero position is established once the tank is ready to operate. I anticipate that the turret azimuth angle for storage or transport will not be with the gun pointing straight ahead. These requirements necessitated the use of a micro-computer (Arduino Nano). Components fitted. Left: motor driver (Pololu G2 High-Power Motor Driver 24v13, #2992), middle: adjustable voltage regulator to provide 9V for the Arduino and right: the breakout board for the Arduino. Power wiring added. Note the addition of some more capacitors to provide additional decoupling. Driver control wiring and motor wiring installed on the right hand side.

That's all for now.