1/8th Merkava Dor Dalet

[jdflute]

Hi All
I'm going to post this from another forum that I have used to record my build so far, so I hope you enjoy and don't mind the repetition.
Jd


OK guys, as you know I have been working on the Merkava project for about two years now. Plenty of research, a lot of trial and even more error.



Due to the intervention of mother nature, arrival of my second son and moving house yet again, things have gone somewhat slower than planned, but as I have made some recent progress, I thought that I should document the build in it’s own thread.
If my track record is anything to go by, don’t expect that many updates, but every now and then I will put up something new.

So the build starts in 2mm aluminium sheet which I cut and folded to make the tub and install a ladder chassis for the suspension system.





Unfortunately I cut it some 10cm short, so I had to cut and fold a new chassis. Doh!!

Next came the upper deck, again from 2mm sheet aluminium



I found an good, all aluminium lazy susan at my local hardware store which I will be using as a turret ring, just about the right diameter with only minor tweaks to the deck.

At this point in time I discovered that the Academy kit I had been using as a guide was considerable wrong, which resulted in me having to remake the entire front deck



Rough detailing of the front deck has been aided by the application of some paint, without which I struggle to see the wood from the trees.

The rear door proved to be a challenge as is a clam shell two piece system. Again, due to a total lack of CAD skills, the final product was developed by trial and error







The tracks and sprockets were purchased (OK I cheated, so shoot me) from Kenny Kong in China. They are in fact 1/8th scale Chieftain tracks, but since the Merkava was developed after the British had withdrawn their loaned Chieftains, they are surprisingly similar.



From there I was able to develop the road wheels. Each of these have been fabricated from two 4” nylon casters, with one face sliced off (ask me how much molten nylon hurts, I dare you). Detail was then added with a little bit of milling and polymorph plastic.







I have also prototyped an idler wheel out of one of my son’s bicycle trainer wheels. Not too shoddy but definitely could try harder.





I also accidently punched my pillar drill whist working on the front drive train.



As a result it took me an awful lot longer to get it all up and running, again it took two attempts before I was happy with the results.



The motors and chain drive are now installed, two 300W 24V scooter motors with integrated gearboxes from the manufacturer in China.



I have fitted them into a skid which then bolts down onto the ladder chassis, there is slight binding on the left hand unit but I’ll be able to tweak that later.

I managed to finish cutting out and shaping the side skirts last night, detailing began a little while ago with the introduction of brass rivets and bolt heads.



All this detailing is basically due to the fact that I can’t be arsed making the trailing arms for the wheels. Twelve of them (my first attempt) have just gone in the bin, and my circular mitre saw is set up with 25mm aluminium bar stock ready to start again. Ho hum, guess I should pull my finger out.

Jd

[jdflute]

To begin with more details of the road wheels.





If you imagine that they begin life as two nylon 4” castors, I cut off one side of each of them, and butt them together, spaced with some large washers. The nylon is as hard as steel and a real @%*&#!#$ to work with, and in the end I used a diamond tile cutter disc on an angle grinder cooling all the time with water.
The bolts go through both sets of wheels and allow me to fine tune alignment of the wheel to keep it true, and the detail is added using molded polymorph and miniature brass fixings from http://www.microfasteners.com" onclick="window.open(this.href);return false; in the States



The paint is added purely to help me see imperfections.

The idler wheels started life on my son’s bicycle as trainer wheels.



Using my pillar drill as a makeshift milling machine, I was able to thin the wearing surface by 50% getting rid of the grooves in the process. Then it was a case of shaping more detail with the ‘mill’ until it resembled something approximating the real thing.



I’m not 100% happy with it and if I can find another identical wheel I’ll start from scratch and get it right second time around. Yet another case of trial and error.

Now the rear door, did prove to be quite tricky. It’s a two piece affair, the top accounting for two thirds of the overall size, and the bottom third acting as a step up into the tank.



As a result, the amount of travel for each door is different. The principle was trialed and mocked up in section with bits of cardboard and wire, before transferring it in to metal.





The biggest problem I found was making the mechanism rigid enough whilst allowing for smooth friction free movement. The servo has a speed control and limit modification fitted to it, so that I can slooooow it’s movement down and stop it exactly where I want, control will be off the undercarriage toggle switch on the transmitter

Now in answer to Stuggy’s question on metal folding, the method I developed was to lightly score the metal on one side and then clamp the piece between two pieces of 15mm square bar in the vice and with g clamps. Then I would ease the metal into shape with whatever leverage came to hand, quite often more 15mm bar, and a lot of grunting, sweating and swearing. Oddly enough, large pieces were the easiest to bend but the hardest to get right, shway, shway, (Slowly, Slowly) as they say in these parts.

I have just finished the mechanism to the headlights which you can see next, here they are in the closed position.



The Merkava stows the lights when not in use, and these have to be manually opened by the crew. Being a lazy sort, I decided to have them pop up at the flick of a switch, so using some micro servos mounted just behind the motors and some cable push rods, they will now pop up and (eventually) switch on when I want them to.



Now in answer to Olly’s question about a test run, I did mention before that I had just binned my control arms, so whilst I would love to take her out for a test run, I don’t think I would get very far ;o)



The arms incorporate the suspension on the outside of the tank as you can see in this photo.



I have the shocks and springs courtesy of Tower Hobbies and will make the control arms out of 25mm square bar. I did think of trying to add detail, but to be honest, no one will see the arms when it is finished and I have a real problem getting enthusiastic over the idea of manually filing down twelve lumps of aluminium. Unfortunately this is where a home made mill just doesn’t cut it.

That’s all for now folks
Jd

[jdflute]

First of the reworked control arms,



Might be a little time before I post an update since I have another eleven to make
Jd

[jdflute]

Well after making the sixth trailing arm, I needed a break from filing, so I have set about putting it all together, on one side at least.





I set about installing a 12mm square bar to mount the springs a guide wheels on to but need to get some longer m3 machine screws to finish that off.
I hope that the suspension will be just right for the overall weight, but only time will tell. If it prooves not to be up to the job, then I'll install a secondary spring system inside the hull.
All this sudden progress make me think I should take another break.
Jd

[jdflute]

Just finished prototyping my idler wheel mount and track tensioner.





Given that I sketched out the design over a couple of a couple of evenings and built it with the aid of grape juice lubrication I am shocked it came together so smoothly. I should finish it up tonight and hopefully build it's opposing number tomorrow.
Will post some more photos once it has been finessed.
Jd

[jdflute]

Well I worked late last night to complete the production versions of the idler mounts and tensioners. Some minor modifications to the prototyped version that makes it function more smoothly and look more like the original. All together very happy with the results.







I hope to get them mounted to the chasis on Monday night and with a little work to the running wheels I should be able to test fit the tracks at long last.
Jd

[jdflute]

Test fit the track on one side last night, I'm very very pleased with the results. Couple of minor issues to deal with nothing too major.



Jd

[jdflute]

After a prolonged absence from the workshop I pulled my finger out and did a little bit of work yesterday.
After machining two new idler wheels, I finally managed to get the Merk on to both its tracks



I need to do some alignment on the drive sprockets, but sometime in October I expect to be able to test out the drive system!!!
Still on for a rolling chassis by the end of the year.

[jdflute]

I have been busy working on my boy's T34 and Panzer IIIH with new electronics and now a little painting is all that is left. For me I finally finished mounting the sides!!!!



I'll need to take them off now to do the detailing, but I'm pretty stoked that they came out so well.

Jd

[jdflute]

Just a little update with a little bit of paint so I can see what I'm doing.





Jd