2022 new build Jagdpanther Part 7

graham pipe · Post by **graham pipe** » Thu Apr 20, 2023 12:37 am

So, lots has happened since the last update - mainly around the final thing to be addressed, the gun elevation and traverse system.

More to follow with photos over the next few days.

It's been somewhat of an Odyssey getting to this stage but there's now light at the end of the tunnel. Hopefully, it's not somebody with a torch!!

Stay tuned, much more to come...

graham pipe · Post by **graham pipe** » Fri Apr 21, 2023 6:38 pm

So, where have the last 4 months gone - seems like only yesterday that I scribed part 6 of this build.

Well, having got the beast downstairs and taken delivery of a compact 12 volt, 18 Amphour gel battery of the type used on garden tractors, emergency lighting and alarm systems, I was at last able to do some test running. The battery is a perfect fit thickness-wise to sit between the torsion bars in the rear engine compartment with just 1mm clearance so it doesn't really need any form of restraint. A switch panel was constructed from aluminium angle section and fitted just below the rear loading hatch so is very easily accessible. It features the normal sliding switch for the receiver power, a single throw 20 amp toggle switch for the Tamiya DMD's nicad pack and a hefty 40 amp single throw switch with red flip up safety guard for the main battery supply.

Switching on, the engine sound goes through the inertia starter spool up process before bursting into life with a nice deep idle sound. Advancing the throttle on the left stick, the engine revs increased and the JP moved for the first time. Up and down our long lounge she rumbled turning almost on a sixpence on our polished tiled floor and leaving nice track imprints on the rugs – much to the irritation of the wife!

Driving through to the kitchen and out of the patio doors, she performed well on the gravel drive and paths surrounding the house but then it refused to turn. Had to manoeuvre it by hand and drive in straight lines back into the house. Just goes to show how powerful it is as it was driving on just one track with the other freewheeling and being dragged around. Cause? A blown fuse – had fitted 4 fuses but, at the time, only had 3 rated at 40 amps so had put a 15 in until I could get to the shops. Popping in a 40 amper solved the problem briefly but on the second test after maybe 100 metres of running, it now refused to turn right or pivot about its own axis.

The fuses were OK but only one motor was transmitting drive. Investigation revealed the final drive's small chain cog to be turning on it's shaft as the locking grub screw was inadequate to hold it against the considerable torque from the E-scooter/electric bike drive motor. Therefore, had to split the track, remove the first 3 wheels, withdraw the sprocket and drive spindle, add a further pair of flats to the shaft and drill/tap the cog to provide 3 screw locking. Replacing everything and Loctiting the screws (now cap head rather than the tiddly M5 grub screws), further driving and all was fine.

Was about to repeat the process on the other sprocket spindle when it now refused to turn left. Aha, one thought, just the same issue as before. But it wasn't. The small cog sprocket is a very tight press fit onto its hub but this one was of inferior quality and, under load, the cog was able to turn around its hub. So, repeat process as above but this time TiG welding the cog to the hub. Addition of a further pair of M5 cap head lockscrews et voila, problem solved. It runs very well, sounds great, has a good but scale turn of speed and bags of power. Was impressed...

So, apart from further detailing, some touch up paint here and there, weathering and application of decals, the last thorny issue was that of gun motion.

After much searching of the spares store, Monique had managed to find all the parts needed for elevation and slew and the small package arrived in Normandy 3 working days later – despite the Easter weekend being in the middle. So many thanks To Monique and the team for getting the order despatched ahead of the Easter break and to UPS for their normal super efficient service!

Of course, with the tank no longer on the bench, I was having to work on hands and knees on the floor to do the aforementioned repairs/ modifications which was no fun at all. Not possessing an elevating platform (one is now on order!), the prospect of working on the gun system did not fill me with the joys of Spring. Additionally, with the model fully assembled, access to the gun mount was going to be restrictive to say the least so I removed the whole unit and made a plywood mock up of the glacis so one could work on it at the bench.

It didn't take long to fit the 12 components in a dry run before painting – I had only purchased the one geared motor for elevation as it was my intention to use a 35 Kg pull digital servo for the slewing. Seeing as it is only 10 degrees one way and 12 the other, the servo option seemed the most sensible. However, I had always been worried about the huge mass of the barrel and Saukopf and firmly believed that a counterbalance would be needed.

Applying first 12 then 24 volts to the little elevation motor and it just would not budge – unless I took the weight of the gun by hand. So, a quick calculation using my schooldays equation of balance moments and the equalising weight needed was apparent. Just under 5 kilos!! The tank was heavy enough already so recalculating with a weight further from the pivot point reduced it to 2.8 kilos with a 40mm extension to the breech block.

My gun barrel was mounted on a 14 mm bore steel tube so this was extended by 4 cm then scrap lead plumbing pipe was cut to the required weight, hung off the end of this stub with duct tape and there it was, a barrel in equilibrium with only the slightest effort required to lift or lower. Testing with the geared motor and it worked perfectly with no strain on motor, leadscrew or threaded brass pivot. So now to tidy it up.

I took an aluminium beer can (German lager of course!), cut off the lid, placed it in a steel cat food tin to prevent toppling and distortion when the molten lead was poured, then smelted the scrap bits of pipe, scraped off the dross and poured into the makeshift mould. I then immediately plunged a 14mm diameter Kettenkrad track pin into the lead to provide a “cast in” spigot to fit inside the barrel tube extension. I had this pin left over from one of the 3 Kettenkrads I have restored in my time so a genuine WW2 vehicle part being recycled for use on 1/6 scale armour!

When cold, the beer can was peeled back, the nice shiny lead scurfed to provide a “key” then primed and painted white. The breech extension was drilled and tapped M6 for a grub screw, the spigot slid into place, nipped tight with said grub screw and yup, she worked a treat – even with the 24 v motor running on 12. A bit slow but motion nonetheless!

Just waiting for delivery of the metal geared servo next week - model shops in France are few and far between so most people shop online. My nearest is in Rouen, a 2 hour drive away.

More to follow plus photos. As normal, just click on the pics to see in full size.