Scratch build SDKFZ 251 / 23 Ausf D Recce vehicle in 1:11 s

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midlife306
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by midlife306 »

Blimey, I love the subtle re-engineering


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Herr Dr. Professor
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Herr Dr. Professor »

"[W}hen the pivot mount is engaged the coil springs are already under slight compression; this is to stop them popping out." If I have any sense of mechanics, the slightly compressed the coil springs will also stabilize the vehicle as it moves.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by 43rdRecceReg »

:clap: Small scale engineering at its enviable :thumbup: best
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

Hi,
Thx,
Mr Midlife and Mr RecceReg.

Herr Dr, you are most correct in your thinking, adds pre load.
Thx for looking in, appreciated chaps.
Sub.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

Hi.
The front axle now just needs the upper chassis mounting beam cut to fit the tapering front of the model and the 2 long steering knuckle pivot bolts shortening and it is finished.

Moving on to the wheel hubs.

As mentioned earlier i am making this model from various items i have left around from previous build or items not used and in the parts bin.
The wheels i have chosen for the front wheels of this model are left over from a UN 6 wheel drive APC i made a while ago, 6 wheels were changed for WPL units and the original ones kept for further use.
The Tyre pattern on these is identicle to a real SDK.FZ 251 so off i went, although the wheel is slightly wider but the correct diameter for my model.
The issue with the wheels is that they did not have a through axle and were only pushed onto a stub axle to hold them on, this would not be good enough for this model so i hollowed out the wheels in order to fit some brass wheel hubs with phospher bronze bearings that i made that would be glued into the wheel giving it a through axle mounting and secured onto the stub axle via a 4mm Nyloc nut.
These wheel hubs will be recessed into the wheel itself so that the nut and axle do not protrude beyond the face of the wheel.
I then turned up some aluminium wheel centers that matched the full size vehicle, these are hollow in the inner center to fit over the nyloc nut and locate into the recessed brass wheel hubs and can be prised out to remove the nut and wheel.
Pics should make this clear.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

One more pic.
Just need to alter the studs from 12 bolts to 8 (maybe)
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

Hi Folks
More insane ramblings.
The scale of this model is 1:11 scale, quite an odd one i admit but there was method behind my madness, in 1/16 scale to me personally it would be too small and fragile and the main reason was that it would be built from what was available to me.
I was looking around for a suitable doner for the wheel arrangement, that being overlapping wheels and a suitable spacing between them, the only thing i could see that would be any where near was a Tiger 1 hull, i measured every thing up and the axle spacings and wheel diameters and the hull tub width were spot on for 1:11 scale, so thats how it ended up at 1:11.
The hull was too long, the gearboxes were wrong and in the wrong place, the wheel configiration was wrong, it had too many axles and the wheel width spacing was wrong...all of which i thought i could overcome with some lateral thinking and jiggery pokery.
A very good friend of mine had an old Tiger hull surplus to requirements so he graciously donated it to science (Cheers Si).
I removed the wheels, axles,suspension, gearboxes and all the internal mouldings, battery tray etc,etc,.
I cut 2 inches off the front of the hull and 1/4 inch of the rear of the hull and removed the idler wheels.
All i had now was a plastic tub.
As we all know the Tiger hull slopes from front to rear, this was no good for my purpose as the Hanomags hull is level from the rear up until it reaches the drive sprocket, it then goes up at a slight angle as it goes over the sprocket.
I cut off both sponsons from the tub and levelled off the hull from the rear up until the point where i decided the gearboxes and sprockets would be placed and angled this part upwards,
I had decided right from the start that the entire body of the vehicle would be removable in one complete piece, only leaving the hull tub and front axle together for easy maintenance etc.

The Tiger tracks were of no use due to their width and niether were the gearboxes so these were returned to my friend.

I calculated the Hanomags outer hull dimensions which gave me the amount of room that i would have to fit a set of tracks into that would look right from the side and not stick out past the hull line nor rub up against the inner hull wall.

I searched my spares pile and located a brand new set of Panther tracks, these looked promising so i measured them up and they were spot on, i also had the sprockets too.
The Tiger has short shaft gearboxes but the Panther needed long shaft gearboxes and i just had a pair that needed a little TLC so these were rectified ( drilling a loose gear and pinning it to the shaft ).
New holes were cut into the side of the hull for the output shafts after measuring all the axles and wheel diameters etc.
I fitted the sprockets to the gearboxes and measured where they needed to be placed inside the hull to give correct wheel allignment and made a 1/8 inch Aluminium plate that both gearboxes were bolted to, this was in turn bolted to the hull floor when i was satisfied with its position.

I removed the front 2 axles and suspension parts from the hull tub and replaced the rest, now i had 6 each side.
The adjustable idler wheel on the Hanomag is the same diameter as the rest of the road wheels so i worked out where that needed to be and also its axle is slightly higher that the other road wheels so this was catered for at the same time.
I decided to fit a 4mm dia solid axle into the hull running full hull width for the idlers and would build some form of tensioner system onto it when i had got all the wheels in their correct places and spaced right.

The Tiger wheels were turned in the lathe to get rid of the Tiger details.
The Hanomags wheels had holes in them, the outer sets have 8 equally spaced holes on a pitch circle diameter and the inner ones had a 6 hole PCD, i calculated these and set about drilling the inner and outer wheels accordingly, these looked ok when done, now all i had to do was to get the correct wheel orientation and wheel widths to fit the tracks,sprockets and idlers that would allow the track to rotate without any binding or fowling, after much experimention and the addition of spacers and cutting axles down to suit it was all fitted and rotated without any problems.

Now to make the idler wheel tensioner system.

Sorry for the long boring, explanation but thought it necessary as it would make the coming photos more understandable

Photos to follow...
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

Hi,
A couple of pics showing the tracked section that i came up with, hopefully all the previous splather i was on about now makes sense.
In order to disquise the panther sprockets and make it look more scale true to the originals fluted sprocket i looked at the original Tigers idler wheels, i checked the diameter and they were perfect to fit over the panther sprocket just leaving the teeth visible and were nice and snug where the track overhang sits where the sprocket engages , obviousy way too wide but i decided to cut them in half and thin them down a bit and glue a half reversed onto the panther sprockets, they came out quite well i think.
Still needs more work on the wheels.
Next rear idler wheel tensioner.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by Sub »

Hi,
Rear idler wheel adjustment completed.

1/16 thick steel bent to 90 degrees to the height of the axle and drilled to bolt to the hull and for a 2ba brass bolt to pass through with 2 nuts either side of the steel bracket, a further 2 ba nut soldered onto the end of the bolt head which the 4mm axle is a good snug fit with no play, to adjust the tension on either track just undo and tighten the corresponding nuts, which moves the axle and lock it up.
Prefer this than the original set up as its inboard the hull away from any muck, mud etc and is so easy to adjust, and its so simple. ( i operate the K.I.S.S. system where i can)

It may look a bit agricultural to some but this design has been in use for decades on motorcycle rear wheels to adjust the chain drive and it will be ok for years of use.
Few pics.
Cheers.
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Re: Scratch build SDK.FZ 251 / 23 Ausf D Recce vehicle in 1:

Post by tankme »

That track adjuster is the same concept I use in my 1/6th scale tanks and it works great. Nothing wrong with that design. My old Suzuki SV650S worked that way to align the rear wheel.
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