Comet A34- Ludwig kit

This section is for builds that are not strictly Tamiya or Heng Long. For instance, replacing the electronics from a WSN or Matorro, or even a scratch-build.
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

PainlessWolf wrote:Good morning, Roy!
You are doing a great job keeping the details in mind and making available parts work with some neat scratch building and modding. I'm looking forward to seeing this one finished and running. Barry! I hear your Alien Overlords and your Machine Shop calling. Get back to work!
regards,
Painless
Thanks for the encouraging words, Painless. Scratch building, or even improvising parts, can be very satisfying when the results are good. However, working on static components (the Tank furniture) is generally easier
than fitting an effective drivetrain, an electronic heart, and an electro-mechanical means of getting the turret and other parts to move- especially where none had existed before. Upgrading RTR models has the advantage of having ready-made screw holes, plastic lugs, working motors, and other means of attachment for the builder to be guided by. Here, there's nothing. :| :problem:
So, you make it up as you go along.
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

This sprocket has been beautifully formed by CNC tech, but that doesn't prevent it being a pain to assemble. It's not just all those wee bolts that have to be screwed in place (click to ENLARGE these images):
Comet build-drivetrain-sprocket assembly
Comet build-drivetrain-sprocket assembly
The two gear wheels on each sprocket will only align properly, when the pre-drilled holes match those the in the wheels. It's possible to spend ages twirling them until they appear to be synchronised (a bit like 'cracking' a safe, I image- though I've never tried it).
When provisionally aligned, I use a straight edge to judge whether the gear teeth match, and whether they're also in line (parallel) with the hub.
Comet sprocket alignment
Comet sprocket alignment
When they do look OK, a final check with a portion of track is a sensible next move. Prevention is better than cure in medicine, just as getting things right here at this stage is better than having to fix them later. :thumbup:
Comet sprocket test fitting to track
Comet sprocket test fitting to track
The track used here is the plastic Pz 111/IV type. I may even use it on the finished model, as it's fairly hard wearing.
Getting the drivetrain properly aligned is absolutely crucial in the build. Any excessive slackness, or toe-in/toe-out in the wheel mountings, return rollers, idlers and sprockets can add so much rolling resistance
to the drivetrain that it stalls the motors. :eh: >:< We all know what the consequences of stalled motors can be (they're often written in £s $s and Euros).
As the StuG motors I bought for the project simply won't fit in the precut orifices in the kit, and I don't want to force them in, I've ordered some premium Taigen StuG motors that look like the should be a better fit.
Right now, then, fitting the sprockets has stalled. Life's little ironies, eh?
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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HERMAN BIX
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Re: Comet A34- Ludwig kit

Post by HERMAN BIX »

Such microscopic details, just to get the sprockets to work!
I had a Matchbox Comet back in the day in 76th scale, liked it then, love yours now.
HL JAGDPANTHER,HL TIGER 1,HL PzIII MUNITIONSCHLEPPER, HL KT OCTOPUS,HL PANTHER ZU-FUSS,HL STuG III,HL T34/85 BEDSPRING,
HL PZIV MALTA,MATORRO JAGDTIGER,HL F05 TIGER,TAMIYA KT,HL PANTHERDOZER,HL EARLY PANTHER G,TAIGEN/RAMINATOR T34/76,
HL AN-BRI-RAM SU-85
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43rdRecceReg
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Re: Comet A34- Ludwig kit

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So...it's back to the idler issue. Yes, the idlers are not an easy fit either. I have no kind of axle (whether from HL or Taigen) that will pass through the metal idler bearing and the suspension arm of the Henntec unit. I have a brass screw that's a good fit for the bearing in the metal idler, but is almost 2mm too small in diameter to fit in the Henntec unit. Then there's the cheapo plastic idler with it's incorporated self-tapping screw. It almost Fits in the Henntec. With a bit of filing, and judicious use of the Henntec arm's grub screw, it could be made to fit. But... I really wanted to use the metal idlers, with their superior built-in bearings (The plastic Pz 111 unit only has a bronze bush...). :problem:
Comet build-drivetrain-idler options
Comet build-drivetrain-idler options
This is the plastic option. The screw almost passes thought the Henntec suspension arm. With filing, it would.
Comet idler- metal option 1
Comet idler- metal option 1
here the brass screw that fits the metal idler's bearing perfectly has been threaded into a tapped brass bush. Unfortunately, the bush is over 4mm in diameter, and the hole in the Henntec arm some 3.6mm.
With a lathe I could reduce the bush in size; but I haven't got one. Alternatively, I could drill the Henntec arm so that the bush would fit- but I really don't want to do that.
The third option is where I retain the metal idlers with brass screws, but make a sleeve out of brass tubing to make fit in the Henntec unit a tight one, when the grub screw is tightened. The brass collar could be sawn along its length to allow it to compress (a) around the brass screw; and (b) to slide tight inside the Henntec arm. The grub screw would prevent it from coming adrift. Well, that's the theory. The best laid plans o' mice and men, eh?
Here's the screw passing through the Henntec arm. Given that the Henntec's grub screw can take up play on one side, it might not even be necessary to have an insert sleeve that goes all the way around the screw.

Don't imagine for one moment, future builders, that progress will be smooth with builds like these. There are more hurdles here than in the Grand National. :problem: :lolno:
Attachments
Comet metal idler. Brass screw needing a sleeve
Comet metal idler. Brass screw needing a sleeve
Comet idlers- plastic option
Comet idlers- plastic option
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

Before I go off for my much needed ugly-sleep, I thought I'd post this pic from the Czech museum I mentioned earlier. This one has some useful details of the return rollers, and suspension, on the Comet; but is also fronted, rather charmingly, by what must be a sort of Czech harvest festival lunch. I bet that's a nice tasty Budvar beer in the jug, as well. :thumbup:
Hmm..looking harder, is that some sort of whip in the foreground?
Image
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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PainlessWolf
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Re: Comet A34- Ludwig kit

Post by PainlessWolf »

Good afternoon!
Tanks, particularly, British ones, go well with any sort of regional specialty. Whips...Hmmmm. I don't know....
regards,
Painless
...Here for the Dawn...
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

PainlessWolf wrote:Good afternoon!
Tanks, particularly, British ones, go well with any sort of regional specialty. Whips...Hmmmm. I don't know....
regards,
Painless
:D
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

Well, I looked at the idler options (..and no, I don't mean the Life of Leisure ones :lolno: ). The plastic one was just about workable; but the assembly is wobbly and wonky. Then again, the plastic idlers for the Pz 111
are fairly cheap.
The option to make shims out of 5mm brass tubing had promise; but didn't deliver. It looked, and felt, messy.
Thus- it was down to the milling of the tapped brass sleeve option. These brass tubes are left over from a Tiger 1 suspension upgrade idea. They were originally fitted to a bar that stiffened the hull sides, whilst providing
anchor points for the swings arms. Chris Ludwig also sells a similar bar for the Cromwell:
Alloy support bar for suspension arms
Alloy support bar for suspension arms
DSC01720.jpeg (55.85 KiB) Viewed 2329 times
Anyway, by a stroke of good luck, I had some brass screws that were a perfect fit for these threaded studs/standoffs
Out came the trusty Dremel, as I don't have a lathe or hobby milling machine in my ever-burgeoning collection of specialist tools. As it happens, there's scarcely any room for additional hardware these days... :problem:
Comet build-axle sleeve for idler
Comet build-axle sleeve for idler
Sorry about the grainy quality of the image. It was taken in low light conditions.
Then I used a captive metal file as the cutting edge of the improvised 'lathe'.
Milling idler sleeve to fit Henntec suspension arm
Milling idler sleeve to fit Henntec suspension arm
Idler sleeves for Henntec stub axles.
Idler sleeves for Henntec stub axles.
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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43rdRecceReg
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Re: Comet A34- Ludwig kit

Post by 43rdRecceReg »

It's looking good. I added some washers either side of the metal idlers in order to support the axle bearings. Then, took a provisional measurement from the centre line of idler halves (where the track horns pass through)
to the sidewall of the tank. The gap was just around the 18mm mark. This means that when the Pz 111 return roller mountings are fitted, the 18mm alignment target for the complete drivetrain looks doable.
Image
Now that the idlers look ok, I should be able to fit the glacis plate as well as the front mudguards. :thumbup: (Barring any other unforeseen hitches :/ ...but, it seems, they can never be discounted.)
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
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PainlessWolf
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Re: Comet A34- Ludwig kit

Post by PainlessWolf »

Good morning, Roy,
Now that is building with hand tools. ;o) Clean work and durable. All that can be asked for.
regards,
Painless
...Here for the Dawn...
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