eight years, four owners, no mile

[Gerhard Michel]

Hello guys,

here I will show you some pics of my "new" Jagdpanther, manufactured in 2008, with at least three pre-owners and not yet ready to run:

[Gerhard Michel]

Mounting road wheels and idlers:





Mounting tread for testing. taperlock unscrew hole parts don't fit (meanwhile corrected):



Drive units changed to spiras:

[Gerhard Michel]

Spiras mounted:



Test running:

[Peter Silcock]

Gerhard it must be very satisfying getting the tank moving after 8 years of it being a static model. The paintwork detail is great.

[Gerhard Michel]

Hello Peter,

well, I am glad for finish, because painting and weathering are not mine. Much more I like it to get the tank moving itself, moving gun and recoil and making a good sound.

Gun elevation and side moving units are mounted for test:



Elevation is fine, but for side moving I prefer a servo. So I get an automatic centering and a simple way to adjust end points of way by transmitter. Therefore I replaced the side moving unit by a strong servo with a servo saver.

All modifications furthermore are planned to allow mounting the components out of the hull and finally inserting the complete gun unit (including movements and recoil) into the hull:

[Gerhard Michel]

Next step was the completion of gun elevation unit. The original planned elevation method was impossible to realize due to the now planned recoil function. A pre-owner already applicated 2 linear ball bearings.

These long bearings allow only half the necessary way for recoil, but I won't change this, and now I have to be satisfied to have at least 46 mm. The inner bearing is mounted only with 2 screws and can move a little to adjust itself in line to the outer bearing. This is not a good place to apply a lever for gun elevation.

Therefore I started some modifications; see pics:





















Now the elevation mounting ist completely detached from the recoil bearing. Side moving is still dismantled.

Then I tested to mount the complete gun unit into the hull. That was a big disappointment, because the gun elevation motor -though mounted without any modifications- collided with the right driving unit, and so the gun unit could not be set in place:








There were 2 reasons:

1. The spiradrive unit has its brush holders in 45 degrees to the vertical line. This holder is the collision point to the elevation motor

2. I don't know why, but one of the pre-owners relocated the gun unit in the hull (see new holes):





Both reasons together prevented the correct mounting of the gun unit. Further modifications were necessary.

[Gerhard Michel]

OK, the elevation unit had to be unmounted again to solve the conflict. I relocated the motor and had to adapt the steel lever which connects the elevation unit with the gun barrel. Now this simple part has a rather strange appearance.






After remounting the elevation parts the complete mantlet unit now can be inserted without any problems, and I could plan the recoil unit.

One of my pre-owners attached a thin-walled aluminium tube which was slightly grinded to fit with the linear ball bearings. However the aluminium was too soft and always a little too thin for a backlash-free gliding. I replaced it by a stainless steel tube which I had slightly to grind (about 0,04 mm) over the whole length; not a nice work. After 2 hours or so of grinding and polishing by hand in the lathe it glides smoothly and backlash-free for the needed 46 mm.



The rest was rather easy to do: a frame for a strong servo and a mounting adapter for a push rod at the inner gun barrel, and the recoil was finished:



Here the gun barrel is in frontmost position:



and here in rearmost position:



another view:



The distance between both end positions is wider than necessary to move the true gun barrel from its innermost position (impact to the outer linear ball bearing) to its outmost position (barrel comes out of the mantlet):



Now I have enough adjustment track for the widest possible distance of recoil, which I will finally adjust by the USM-RC2 sound module I use in all my tanks. This multi function module is rather popular in Germany for its various functions of sounds and movements. So it can control the barrel recoil with accurate adjustment of distance and velocity (of course fast back and slow foreward movement); triggered only by the shooting command from transmitter.

[Gerhard Michel]

The ESC has taken place for the first time. I use a 2 x 100 Amps TVC-B100 double speed controller from SGS in Germany with built-in mixer and seperate brake channel. It is modified to my particular wishes, so that also slight curves can be made when using spur gear motors (used in all my tanks except the Jagdpanther). For AT models this modification is not necessary, because worm gears are nearly self-locking, but it is also not troublesome. So I can use every esc in every model.

[Gerhard Michel]

Now it was time to make some thoughts about the control board. At my Jagdtiger I use the back door of the casemate to hide my control board; in my opinion a useful, practice-approved solution. Therefore I decided to do the same at my Jagdpanther.

First of all a little frame was needed to hold the board, because some space is necessary for the lever of the circuit breaker. I use aluminium scrap parts which are available for low cost:



Because the model is finshed already, I have to hide all new drilling holes behind available fittings as fire extinguisher, hinges and so on (the pic shows a test mounting before sluring the frame):




Here the board ist mounted (without wiring):



Fraom left to right you see the main circuit breaker, below it a fuse holder for the steering circuit, above three LEDs to indicate voltages and switch states, below 'dollhouse' pushbuttons to switch my 100 amps bistable relays in the main power circuits and right a switch to activate the sound module. Right to the bottom are the sockets for loading 2 lead silicone akkus in series with a middle tap to load them individual. LiFePO4 cells are rather expensive today, therefore I will test these silicone batteries which are extremely resistant in cycle use (up to 300 cycles at 100 % DoD!). If this is true, I could use them about 150 years due to my operation conditions!

This arrangement allows me to control the whole tank, the driving without sounds (e.g. for transport) and the use of the sound without activated motion possibilities. The USM-RC2 sound module has an option of background musics (controlled by RC) giving hours of songs for entertainment in 'pauses in the fighting' . It is an additional safety when there is no possibility for the model to move unwanted.

[Gerhard Michel]

And here is my summary of power electronics, not yet wired. At the other side of the hull I will place the control electronics (receiver, impedance converter, Beier sound module and possibly Beier extension module for more sounds and functions than the Beier basic module offers, depending on additional functions in future).

From left to right you see my 'power posts' (+24 V, +5 V and the combined ground), then 2 bistable relays (100 amps switching power), then the brand new 2 x 60 watts amplifier from Thomas Benedini, then my dc-dc converter 24 V to 5 V 5 amps (BEC for the receiver, my power servos and the Beier sound module) and at the right an up to 300 amps telemetry sensor for 3 summary voltages, 1 single cell voltage monitor (up to 14 cells e.g. of LiFes, LiPos and so on), the accumulated power consumption since starting (very important to satisfy the 50 % DoD rule of lead acid batteries!), 2 temperatures (e.g. esc and motors) and some other values which are more useful in model aircraft.

Best of all: all values can not only be displayed in transmitter, but I can program warning edges for all values with acoustic warnings given by the transmitter when exceeded! Therefore I don't need to look permanently at the display to realize differences and faults.

When I drive my tank I often am alone in the field, without the possibility of getting some quick help when a difficulty occurs. Therefore I try to prevent from those difficulties by permanently observing the most important driving parameters. Modern Rc-systems offer various possibilities for this monitoring; let us use them!

[Sam Hough]

Very impressive.

What is the "50% DoD" rule?

What temperatures do you plan to monitor?

Cheers

Sam

[Adrian Harris]

DoD is "Depth of Discharge".

So if you have a 20Ah battery, don't take more than 10Ah out of it.

That's why AGM batteries can be labelled "Deep Discharge", as they can typically handle 80% DoD without damage.

Adrian.

[Gerhard Michel]

AGM batteries can handle various DoDs, depending on manufacturer and the intended life cycle (amount of charges / discharges), which depends deeply on percentage of DoD. Therefore it is nice to have some info about extracted amount of charge. In my opinion this is the most important value in handling a lead acid battery.

This ist my first Armortek model; my others don't use worm gears. Without a worm gear it is not so easy to get slight curves, because in a curve the inner track rather moves its motor forward instead of moving sideways over the ground. Therefore it is necessary to shorten the engine in pulse pauses instead of only cutting the power. Thats why -together with the manufacturer- I installed a sharper 'flyback' to the esc which achieves this shortening of the engine.

This change causes some more heating of the esc (the flyback diodes); therefore it is helpfully to control its temperature range with telemetry. Also the drive engines should be controlled when driving hours in heavy grounds.

[Maarten Schutjes]

Great work Gerhard! Thank you for sharing. Nice to see the sgs tvc-b100. I use them too on occasion for tanks.

[Gerhard Michel]

Thanks, Maarten!

In this tank I will test lead silicone batteries ("Greensaver") for the first time. They should achieve 300 cycles even with 100 % DoD. If this is true it might be possible to halve the installed capacity of AGM lead acid batteries without larger handicaps, which means reduced space requirement and weight without shorter operating time (and also reduced costs ). 300 cycles in 10 years (estimated battery lifetime) means 30 cycles or about 60 to 90 operating hours per year using 24 ampere-hours capacity with 100 % DoD, which would be much more than I can use one of my four models in a year.