Cromwell Mk 4 1:16 scratch build Ludwig kit

[43rdRecceReg]

Have just finished wiring the lower hull section; but creating a mounting for the elevation servo in the Turret feels like one of those dreams, where you're trying to run through a field knee deep in treacle, or liquid concrete
If the bracket is out by even a millimetre of two in the vertical or horizontal planes, the servo won't drive the elevation gear properly. More on that later. Meantime, if anyone has any 'Dos and Don'ts' of servos for RC tanks, I'd be glad of the input.
E.g: best type for RC tanks; travel limiters; direction of rotation; power etc., I'd be very grateful. I'm not only a scratch-build virgin, as I admitted at the outset, but also a servo virgin. Unlike many here, I had no experience of RC planes, boats, etc., before being seduced by RC tanks. In fact, when I was interested in planes, instructions were written in Runes, and the best ones were controlled by wires. This involved the 'pilot' spinning in a circle... with the plane buzzing furiously, at the end of the control lines until the plane crashed, or he vomited or fell over, as a result of extreme dizziness The only servos I've used before were on car brakes . The Taigen tiger 1 I built, was assembled from stock components, and required no servos. Ditto, for the Panzer IV project (still on the back burner). The two tiger 1's I have both contain a servo for the Taigen Barrel recoil system, but required no meddling from me as such. That's why I remained a servo virgin...but now I've elected to fit not one, but TWO servos to the Cromwell, on home designed mountings, I'm losing that 'virginity' in style..The 'Emax' servos I have for the Clark recoil/ elevation unit came with on instructions.
Pertinent details I've found online:
"..Operating voltage: 4.8V-6.0V
STD direction: Counter clockwise / Pulse traveling 1500 to 1900usec
Stall torque: 1.6 Kgf.cm /21.0 oz.in (4.8V), 2.0 Kgf.cm /28.0 oz.in (6.0V)
Operating speed: 0.12 sec/60° at no load (4.8V), 0.10 sec/60° at no load (6.0V)
Plug available: Futaba, JR compatible .."
Ok. Standard direction..counter clockwise. Yes, but from what viewpoint..front or back? Limit of travel 60deg? So where's the optimum position for the drive gear vis a vis the partial gear on the GUN? I'd rather have the answers to these questions before I connect the turret to the Clark unit. More on all of this later.
Meantime, I've added the Bow MG, and an antenna for the turret. The latter being a product of Woz (from this forum) on the Shapeways site, and not one I've fabricated myself

Antenna base from radio

After blending in, sanding, and proper layers of paint it should all look much better. The tank has a light coat from a rattle can currently, just to give an idea of how it will look.

Taigen MG fitted in bow position

Sorry, not enough depth of field there..
Here's the final arrangement of the Hull electronic components, with the circuits live. Turret and upper hull wiring yet to be settled.

Final arrangement for Hull electronics

and again:

Circuits live

Although my experience of using RC servos is, hitherto, non-existent, I've a fair knowledge of electronics through hi-fi, recording, and car digital systems..
Created a new profile or Cromwell on My Spektrum (for the first time)..tick!- success. Smoker working..tick! success... sound..working properly..tick! Thanks again to Stian (Maxmekker) for a superb soundset on the Clark TK60, and especially
that wonderful Rolls-Royce meteor sound! Success.Tick.
The lower hull is a runner..except that the right gearbox seems to lock solid (asiatam sh*te). Disconnected it from the TK60 in case it blew something. On inspection, the solder on the terminals looks fragile; but managed to get the drive and tracks moving with a remote 6Vdc supply. Even then, something in the drivetrain causes it to lock solid every now and then. Added Ptfe dry lubricant. Still, running rough. Left hand motor/ drive train easy to move by hand, right hand moved freely, then locks solid. Hmmm.I've not encountered that before. Ideas anyone? I may try 'running the motor in' before I reconnect it to the
Clark. If nothing else, the tracks seem to be a good fit, and everything else works properly. I have just created a Youtube channel, and so when I get things going, I'll add a video of progress (virgin in that department too!!)

Cromwell switch access hatch

I'm pleased with the access hatch for the power switch. The bar it sits in also contains a switch for the smoker, the volume control (Works! Tick!..success), and a remote battery charging point to boot..
Still have to refit the MG in the Mantlet, but have no plans to make it a 'working one' just yet.

Exterior nearly finished

Another angle

and the pert posterior:

Rear only needs tow shackles

Now, the abiding issue of servos.

Gun needs mounting point for elevation servo

I've designed a bracket to hold the servo for the barrel elevation. Thing is, as a fixed unit, it has to be perfectly positioned in the horizontal and vertical planes- and that's really hard to work out. Does the centre axis of the servo drive wheel line up with the middle of the elevation gear (seen through the Commander's cupola aperture), the bottom, or the top? That depends on the inherent travel of the servo..an unknown so far; and the rotation direction.
This Clark pic suggests a position below the median, and that's the one I'm going to try..
[/attachment]
That's the next challenge..and that crappy gearbox..

[c.rainford73]

Ah the memories of my first Rc .... A Cox string controlled gas powered airplane my father purchased for me as a child. The spinning nooooo!

Anyway I just encountered a locking gearbox issue with a Mato gearset ( there's that name again) . After multiple checks I feared that I would damage my Clark board and I found an obstruction in one of the track links that was jamming on one side ( actually a scrap piece of metal cast I to the tracks). I opted to replace both gearboxes to be safe with a new steel set from Forgebear! major headache resolved and much smoother drivetrain

[PainlessWolf]

Good afternoon,
This is beautiful work! I am surrounded by the Giants of The Hobby in here. 43rd R&R, you definitely are among them. ;o) Following along!
regards,
Painless

[43rdRecceReg]

Ah the memories of my first Rc .... A Cox string controlled gas powered airplane my father purchased for me as a child. The spinning nooooo!

Anyway I just encountered a locking gearbox issue with a Mato gearset ( there's that name again) . After multiple checks I feared that I would damage my Clark board and I found an obstruction in one of the track links that was jamming on one side ( actually a scrap piece of metal cast I to the tracks). I opted to replace both gearboxes to be safe with a new steel set from Forgebear! major headache resolved and much smoother drivetrain

Thanks for the observations, Carl. Apart from my dizziness- inducing experience of Control line planes..eons ago, I also tinkered with gliders and glow=plug engined planes. That was when 'planes and gliders had their controls fixed in a gradual turn pattern, as that's about all you could do without RC, and RC wasn't really option in the 1950s, and early sixties. I graduated to scratch building a Hawker Hunter with balsa, tissue paper and dope (always like the dope ). It was to be powered in level flight by a 'jetex' engine. But when said engine was launched with the plane,
it reduced it to an aerial bonfire. ...a sort of homemade Comet. After that, I ditched models and went into making music...(which I still do), as a hobby.
Yep, I'll have to think about better quality gearboxes. I think the track is OK on that side, but will check every link for obstruction. A real bummer, now that I've come so far...For the moment, though, I'm going to finish the elevation unit.

[43rdRecceReg]

Good afternoon,
This is beautiful work! I am surrounded by the Giants of The Hobby in here. 43rd R&R, you definitely are among them. ;o) Following along!
regards,
Painless

You're very kind, Painless, and generous with praise. After this latest setback though, a setback among many..(glitchy right hand gearbox, this time) I feel like a Lilliputian of the Hobby

[PainlessWolf]

Good morning, 43rd R&R,
You may need to remove those gearboxes and do a run in on them ( attach a drill and lubricate them and run them for a bit with the drill to smooth them out or at least see what the issue is. If those are the Asiatam low profile gearboxes, they should have steel gears and be almost bullet proof ( got a set in my early StuG ) Following along,
regards,
Painless

[maxmekker]

the model looks amazing on those photos. Happy you like that soundset .

Are you using those low pofile 'taigen 5/1 steel ..... smooth .. durable etc etc.. ?

I bought 1 set of those for my kv 1 last year, and man were they rubish.. wow. I can steel 'hear' that awfule noise they made , soo loud and noisy, binding, pulling Left. Just closed my eyes and tossed them

[43rdRecceReg]

the model looks amazing on those photos. Happy you like that soundset .

Are you using those low pofile 'taigen 5/1 steel ..... smooth .. durable etc etc.. ?

I bought 1 set of those for my kv 1 last year, and man were they rubish.. wow. I can steel 'hear' that awfule noise they made , soo loud and noisy, binding, pulling Left. Just closed my eyes and tossed them

Yes, the TK 60 setup looks like a winner from the start Max, and thanks for all the trouble you took...and the chocolate, of course As for the motors, they look exactly like the low profile 5/1 Taigen ones; but, according to Christian (who supplied them) they are Asiatam 5/1 low profile boxes, and yes, the one on the right is incredibly noisy. Having spent a king's ransom on the project so far, I'm reluctant to splash out on extra hardware. So, I think i may follow Painless's advice, and try running the motors in.
As they were a fiddle to fit in the first place, I'll put the tank on blocks, and run the motors and tracks in using a 6/ 7.2 vdc independent power supply.

[43rdRecceReg]

Good morning, 43rd R&R,
You may need to remove those gearboxes and do a run in on them ( attach a drill and lubricate them and run them for a bit with the drill to smooth them out or at least see what the issue is. If those are the Asiatam low profile gearboxes, they should have steel gears and be almost bullet proof ( got a set in my early StuG ) Following along,
regards,
Painless

yes, they are described as Asiatam, and have steel gears..superficially, anyway. Early in the build, I was taken aback when i dropped one of the motors, only from the table onto the laminate floor, and was astonished at how metal of such a thick gauge could bend so easily. (Part of the frame near the output gear, and it's nearly 2.5mm thick!)

[UZI]

The model looks great
In the future I also intend to build it, preferably in the version used by the Polish army