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Comet A34 Scratch build

Posted: Wed Dec 28, 2016 1:22 pm
by wibblywobbly
For no other reason than I have sheets of styrene and a 3D printer, I have decided to have a go at scratch building a Comet A34. Despite the box shape, it will be neither easy or quick, so don't expect rapid progress, quite apart from which I am clean out of printer filament, and need new nozzles from Australia. :|

I have cut out the hull side panels so that's one job done, and have another piece done for the hull base. A test fit of HL gearboxes miraculously allows them to be bolted to the hull floor and the shafts will line up with where the sprockets should be.

The road wheels are my current challenge. I could use Bulldog/Pershing/Leopard wheels, but they are 800mm on the real thing, which makes them the same size as Tiger roadwheels, so quite a bit bigger. I am currently trying to design wheels as one piece two wheel setups, with recesses for bolt heads and a roller bearing. If I could find a way to obtain rubber rims that would fit that would be the icing on the cake, maybe Tamiya Tiger ones might fit? If that doesn't work, the cheap and cheerful option might be to get hold of Tiger wheels and print inserts to turn them into the Comet design. I could then use Tiger suspension arms and save the hassle of printing those. :clap:

A couple of pics, ignore the print quality, I am using up the dregs of some old filament that is never going to give me a good finish in a million years.

Re: Comet A34 Scratch build

Posted: Wed Dec 28, 2016 1:57 pm
by tomhugill
Hey Rob, my Cromwell uses Taigen metal suspension arms with some small modification for the suspension Spring. The wheels are looking excellent! The tyres on mine are what looks like a rubber tube of correct diameter cut down to thickness. Are you planning on using pz iv tracks? If so the gap between the wheel halves looks on the narrow side for the guide horns.

Re: Comet A34 Scratch build

Posted: Wed Dec 28, 2016 2:58 pm
by wibblywobbly
I have a couple of PzIII track links so tested the setup using one of those. 3.5mm between the wheels seems about right. The gap in the pics is just a rough mock up, there is no spacer in there, and the wheels are seperate items, so they are closer than they will be.

These pics are what I am aiming to print when I have got the printer, filament, bearings, and bolts.

Re: Comet A34 Scratch build

Posted: Wed Dec 28, 2016 3:50 pm
by tomhugill
Excellent! They look pretty identical to the ones chris sells which are on my Cromwell, they seem to work well so should be no issue with yours

Re: Comet A34 Scratch build

Posted: Wed Dec 28, 2016 5:50 pm
by AlwynTurner
Hi Rob, looking forward to this, following along.
Alwyn :thumbup: :wave:

Re: Comet A34 Scratch build

Posted: Thu Dec 29, 2016 8:08 am
by Ad Lav
Nevermind

Re: Comet A34 Scratch build

Posted: Fri Dec 30, 2016 9:45 am
by wibblywobbly
I had a quick whizzover on the wheel design. Looking at the pics of the real ones, mine were nowhere near right. This is pretty close, the one on the left is the later version, which is what I need.

I may have a go at trying a drive sprocket, though I know nothing about gear teeth size/spacing etc. The idler and return rollers should be fairly straightforward though. Suspension arms are fairly simple, I have an idea for spring mounts that should work, hidden inside the hull...we shall see... 8O

Image

Re: Comet A34 Scratch build

Posted: Fri Dec 30, 2016 11:35 am
by wibblywobbly
Does anyone know the diameter of a Comet idler wheel, and drive sprocket??

It seems that a PIII roadwheel is almost identical to a Comet idler, if I take that route it will save me some hassle. Idiot that I am I sold off a box of crap that included metal idlers, and a full set of metal return rollers and mounts months ago...kicking myself now.

It might seem a daft question, but I have never owned a P IV, are the tracks exactly the same as the PIII, it seems wise to ask before I order two sets...one pair won't be long enough.

Re: Comet A34 Scratch build

Posted: Fri Dec 30, 2016 12:05 pm
by HERMAN BIX
H/L PzIII tracks definitely fit a H/L PzIV running gear.
Any other brand of track/drive sprocket combo I cannot say for certain.

Re: Comet A34 Scratch build

Posted: Fri Dec 30, 2016 3:25 pm
by tomhugill
wibblywobbly wrote:Does anyone know the diameter of a Comet idler wheel, and drive sprocket??

It seems that a PIII roadwheel is almost identical to a Comet idler, if I take that route it will save me some hassle. Idiot that I am I sold off a box of crap that included metal idlers, and a full set of metal return rollers and mounts months ago...kicking myself now.

It might seem a daft question, but I have never owned a P IV, are the tracks exactly the same as the PIII, it seems wise to ask before I order two sets...one pair won't be long enough.
Mine uses a panzer iv road wheel modified to look like a Cromwell idlers