1/18 RC Sherman build...finished: pics and video (Full Version)

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borealis -> 1/18 RC Sherman build...finished: pics and video (4/8/2008 8:40:24 AM)

I always wanted an RC Sherman without paying for the Tamiya one. Now I have gathered enough courage and skill to try to build one by myself. Well, not from scratch, of course.

The basis will be the (imho) beautiful sherman from BBI: it's a 105mm M4A3, VVSS, weathered, a lot of stowage and accessories (ammo crates with 105mm shells, fuel and ammo tanks, 'grease gun' and binoculars), commander, motor internals and openable motor grills. And all hatches open (driver, radio operator, loader and commander + motor).
I bought it off evilbay from China, and it did cost about 55 dollars inc shipping, which in euros is a very fair price.

Tracks are a single-piece rubber, suspensions are non-functional, but the plastic wheels have metal axles.

(continues)









borealis -> RE: 1/18 RC Sherman (4/8/2008 8:50:44 AM)

The electronics would have been Heng Long S&S, but everything else had to be tried and discovered.
First step: the traction. After some talking with thomasjohnmurphy (which made a beautiful 1/18 Panther conversion some time ago, and convinced me about the possibility of success in such a project) I decided to try the VSTank 1/24 Tiger gearbox/motor assembly.
Lucky me, the width of the assembly is perfect for the 1/18 Sherman.
Therefore I removed the original sprockets from the tank (which was a very hard process, since their metal pin was 'welded' into the side plastic), and cut the Tiger sprockets from the gearbox axles, leaving the central part in place (it's glued or hardly connected to the axles, btw).

The with putty I mounted the sherman sprockets onto the tiger axles, adjusting their centering by connectin a power source to the motors.

The front plate of the sherman lower hull had to be cut off to make room for the gearboxes. It will be reconstructed later, using a thinner sheet of styrene and remodelling the front curve.

(continues)



borealis -> RE: 1/18 RC Sherman (4/8/2008 9:00:25 AM)

For test purposes, and since the HL receiver board I have ordered have not arrived yet, I will try it using a WSN T34/85 board, powered by a 7,2 battery pack.

The gearbox assembly was "dropped" into the lower hull with almost no reshaping of the internals. It will not require further screwing, just a retainer to avoid its rotation when put in reverse.

I put the tracks on and made a running test.
The test went fine, the tank runs and turns without problems on the flat floor, and the motors have great torque. I tested it on a 30° ramp and it climbed with no effort (sorry, no video).

I then rebuilt the front plate around the gearboxes, and the final effect was visually hardly noticeable from the original. After painting, It will be fine.

A notice here for anyone who would like to try the same conversion: if you start from the 21st century or FOV 1/18 shermans, the front plate is different, and there is even less room for such gearboxes, thats why I opted for the BBI one.
Maybe a solution like the one used in the WSN T-34/85 transmission would fit better.

(continues)



borealis -> RE: 1/18 RC Sherman (4/8/2008 9:49:31 AM)

Next step: the turret.
You know, the Sherman turret (except possibly the Firefly version and its stowage box) has little room. In 1/18 it's even less.

After cutting and filing I managed to put an airsoft gun inside the turret (the original project), but there was simply no clearance to elevate/depress it by a sensible amount. I don't mean room for the elevation mecahnism (which would have required to be put under or by the side of the gun), I mean the clearance needed for the gun mechanism to elevate or depress. Just a few degrees were available.

It didn't satisfy me, therefore I decided to reuse the spare barrel mechanism from the WSN T34 (which I converted to airsoft some months ago), and build a 'sparkling' Sherman.

The Wsn barrel has a red light + 'recoil' feature. The main flaw of the WSN recoil function is (apart from its not-so-real dynamics) is that first the barrel recoils, then the led lights up and you hear the 'boom' sound.

I decided to improve it, at least a bit. Therefore built a N.O. switch, operated by the recoil cam. It will command the barrel led and 'boom' sound, and then the barrel will recoil.
To make the recoil movement a bit better it would have also been necessary to re-design it, but I decided it was acceptable for a mostly indoor tank.

The firing led was changed with a bright white led, mounted a bit inside the barrel (instead at its mouth), with the barrel interiors painted in silver to better reflect the 'flash'. Firing test were satisfactory, the flash is clearly visible even against a wall a couple of meters in front of the barrel, in daylight.

At the same time I reshaped the elevation mechanism, in order to fit it into the turret.


(continues)



borealis -> RE: 1/18 RC Sherman (4/8/2008 10:05:05 AM)

Time to fit everything into the turret.
In order to keep the shoot sound, I will put 2 speakers into the tank.
One will be connected to the small WSN sound board (which requires its own power supply), and one to the HL board.
I looked for a couple of speakers small enough to fit into the tank, and on a market desk I found a chinese made tape walkmen, radio, recorder, with two built-in speakers in the tape holder for 6 euros, including earphones and batteries.
Bought it and removed the speakers (the electronic beauty still works with earphones..if anyone wants to buy it, make your offers :D ).
The small speaker will fit into the turret, therefore I put both the speaker and the Wsn sound card aside the gun.

This is where I am, at the moment.

Next steps could take the easy path: removal of the interiors and fitting of a battery pack, standard speaker, boards and maybe a smoke generator. But since this is meant to be mostly an indoor runner on my wooden floor (which my other 1/16 tanks would spoil), I already dropped the smoker.

Then I decided that I WANT to keep the motor interiors accessible through the motor hatches, therefore I will take the hard path and try to fit everything without discarding it.

Stay tuned...




The hussar -> RE: 1/18 RC Sherman (4/8/2008 12:59:14 PM)

Fantastic job Borealis!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



The_Stuff -> RE: 1/18 RC Sherman build (4/8/2008 8:13:07 PM)

wow. never thought of the 1/24 parts for rc'ing a sherman. I have one of those 1:18 ones from FOV.



borealis -> RE: 1/18 RC Sherman build (4/8/2008 9:45:22 PM)

I bet you would like to see it running around, isn't it? [:D]



thomasjohnmurphy -> RE: 1/18 RC Sherman (4/9/2008 3:15:21 AM)

That's awesome. And thanks for the tip on the BBI vs 21st Century Sherman. I was looking at the 21st Century front plate and had difficulty seeing how a drive axel would work given its shape. Now I will get a BBI Sherman to RC it. I wonder how the 1/16th HL Pershing tracks (same as the Sherman) would fit your tank. The reason why I ask is that in my first 1/18 Panther conversion I used the stock rubber tracks with the stock drive sprockets (modified to fit with the HL gear box) The tracks caused a lot of friction and jumped off a lot when you turned corners. On my recent 1/18 Panther conversion I used the Tamiya drive sprocket and Tamiya individual plastic links. In as much as the sprockets are a little bigger , it is hard to tell they are slightly out of scale. To be honest, this is becoming my favorite tank. I had it our today driving in the grass (it was even able to do superspins in the grass as most people know it is difficult with even the most powerful HL tanks. I also had it climbing up a 30+ degree incline with absolutely no problem (and not once did the tracks jump.) I already know you can put a turret traverse mechanism in the tank so that won't be a problem. I am thinking of an airsoft unit for this one. I have to get a 190mm length madbull barrel machined (tapered) to give it the proper. I know it will be doable. Like you, in my last Panther I used the WSN recoil mechanism instead of the airsoft. In my most recent 1/18 Panzer IV smoke and sound conversion I was able to find a solution to the gun elevation problem. I bet you it would work in the Sherman. I took a s3003 servo and modified it so it would continue to go around. I put it vertical in the turret so that it sat flush with the airsoft unit. I glued a 1/4", 1" piece of sprue to the side of the airsoft unit on a 45 degree angle (+/-). When the servo arm swung around it brushed up against the piece of sprue pushing the unit up/barrel down. although not a perfect solution It did allow for the gun elevation to be remotely moved. When the servo arm brushed past the piece of sprue the barrel would spring back in its full elevated position. I use elastic bands to create a tension so the gun would spring back. Im my pics you will see the Panzer IV conversions. Someone on ebay had sold scratch built a Jagdpanther. I wish I had bought it now I know I could make it run without any problems. I'll get a thread going to show the work I've done on it. I am now thinking that you don't need the Tamiya sproket/ tracks. You could use the HL 1/16 metal Panther tracks. These are not as wide as the tamiya (I have both) and look more to scale. I'll know later tonight as I plan on trying those tracks on my panther. If they work then for less than $300
you could have an awesome fully RC Panther tank with metal tracks, sprockets, gear box , smoke and sound. the whole works

$75 1/18 Panther
$90 Matorro metal Panther tracks and drive sprockets.
$50 HL Smoke and sound upgrade kit
$30 metal gear box with motors
$20 old 1/24 HL tank for parts (turret ring/turret traverse/upper wire harness -and airsoft unit if you want it
$10 s3003 servo

You could probably do it for less if you find a good deal on the parts.



The_Stuff -> RE: 1/18 RC Sherman build (4/9/2008 4:49:57 AM)

I was thinking of more like finding a 1:24 that had been broken physically on the body or something that was cheap to buy or just cheap in general and then gut it and put it into the sherman.



Planedev -> RE: 1/18 RC Sherman build (4/9/2008 7:01:26 AM)

I thinkyou can get the VStanks drive unit as replacement spares, these will be cheaper than waiting for a tank to break?



blitzkrieg65 -> RE: 1/18 RC Sherman build (4/9/2008 7:10:31 AM)

Alright, good work Borealis, I will be posting my own unique Sherman in a few days, but I really leike what you did in the Turret!

The Blitz



borealis -> RE: 1/18 RC Sherman build (4/9/2008 7:34:48 AM)

@thomasjohnmurphy:
I too have a 1/18 Panther sitting there and waiting for being RC'ed (after the Sherman) and was thinking about the track compatibility with the sprockets.
So it is necessary to adopt the Tamiya sprocket, but how do all other wheels behave? Do the 1/16 tracks fit well between the 1/18 wheels?
And could you post a picture of the s3003 modified elevation mechanism?
About the tracks: the VVSS Sherman mounts different tracks from the Pershing ones, which would rather fit an HVSS type.
I have tried to fit the Pershing tracks on the Sherman, using only one half of each track, but what you miss is the side teeth which keep the track in place on each wheel.
Also the track sections don't fit perfectly on the sherman sprocket.
In theory, it would be possible to build a compatible set of track starting from those of a Pershing, but that would be a very long and boring process.


@The_stuff:
You can order the gearbox/motors alone as spares, as Planedev said, and it's not costly. The other VS tanks (Abrams, T72 and Leopard) have a different gearbox assembly, more compact in lenght, but higher and not suitable for tanks with traction on frontal sprockets.

@Blitzkrieg:
Can't wait to see different solutions on the subjecT!



Planedev -> RE: 1/18 RC Sherman build (4/9/2008 8:40:25 AM)

I dun suppose any of you dare to use one of those tamiya educational dual gearboxes? I got one of those gear box but have yet to think of whatto put it in.



borealis -> RE: 1/18 RC Sherman build (4/9/2008 8:45:39 AM)

That was also one of the options, even though the tamiya kit will surely hold less torque than a Vstank or HL gearbox unit.
From the datasheets and pictures I have seen, its width is less than the Vstank gearbox.
That's why the Tam gearbox kit is a popular choice to convert to RC the 1/18 halftracks.

The gearbox choices out there for converting tracked vehicles in 1/15-1/18 are not infinite:
- the Heng Long 1/16 series, plastic and metal gears, normal, compact, 3:1 reduced, etc. Prices go from cheap (spare/used) to rather costly (low profile and reduced gearboxes).
- the VStank 1/24 series: "Tiger" type and "Leopard" type, similar to the HL 1/24 series. Affordable.
- The 21st century PzIV RC gearboxes. They are not available as single spares I think, so you have to dismantle a tank.
- The WSN T34/Tiger gearboxes. Difficult to find as spares.
- The Tamiya RC tanks gearboxes, different types. Expensive.
- The Tamiya gearbox kits for robotic purposes. Affordable.



thomasjohnmurphy -> RE: 1/18 RC Sherman build (4/9/2008 2:38:35 PM)

I put the HL sprokets/metal tracks on my 1/18 Panther this morning. They do fit HOWEVER, You will have to place the gear boxes closer together to bring in the sprocket (the HL sprockets are wider than the Tamiya) This will also mean you will have to cut down the outside drive axel sheild (the curved part of the tank that protects the inside of the drive spocket. It probably wouldn't be that hard to do. You will need a dremel for this. I'll try to get some pics posted.



borealis -> RE: 1/18 RC Sherman build (4/9/2008 3:20:39 PM)

I have just found an occasion on a set of Tam Panther plastic tracks, I think I will then buy a set of sprockets and go that way. Did you also replace the idlers with metal ones?



thomasjohnmurphy -> RE: 1/18 RC Sherman build (4/9/2008 5:31:40 PM)

No, the stock sprokets work great. You just have to cut the rear axel in the middle then slide a brass sleave inbetween. I used milliput to secure the sleeve. It allows the idlers to operate independantly



borealis -> RE: 1/18 RC Sherman build (4/11/2008 7:21:56 AM)

Some progress in design.
I will adopt 6 x AA size batteries to power the tank. The best I have found are some 3900 mAh capacity batteries, which will provide alot of running time.
Of course it will be possible to charge them onboard, therefore I have bought two AA battery holders.
The two packs will be connected in series and they will find place on the tank upper hull, on both sides.
Pack 4x will get the left place, pack 2x the right. The weight difference is negligible, anyway the turret rotation gear will stay on the right too, balancing it.




borealis -> RE: 1/18 RC Sherman build (4/11/2008 7:31:59 AM)

Since the upper hull is open downwards over the tracks, I will need to build a support structure for the batteries.
These batteries get hot while charging, therefore the support structure will be metal (aluminium), to work as a heatsink too.

After some measuring I drawed on pc and printed a paper model of the structure.
For added srenghtness, it will be made in one piece, cutting and bending a 20x50 cm, 0.5 mm thick aluminium sheet.

Some pictures of the cardboard model and the fitting test.
Notice the bar which will run over the gearboxes: during the running test, I found that in reverse the reaction torque tended to rotate the gearboxes counterclockwise. The bar will counter that torque.

The model was good enough, just needed some minor corrections and improvements.

Next steps will be the delicate process of cutting and bending the aluminium.



thomasjohnmurphy -> RE: 1/18 RC Sherman build (4/11/2008 2:48:36 PM)

Someone must be an Engineer (great work) I just secured another set of Panther sprokets to go with my Panther tracks. Looks like I will have 2 1/18 RC Panthers in the works soon. I'll get a pic of the servo driven gun elevation unit posted soon.



borealis -> RE: 1/18 RC Sherman build (4/11/2008 2:53:43 PM)

Thanks, I will remain in wait.

Engineer... indeed I am ;)



thomasjohnmurphy -> RE: 1/18 RC Sherman (4/16/2008 4:06:46 AM)

As requested, here are pics of my 1/18 Panzer IV conversion gun elevation solution. Its a servo that have been modified to continually spin. You can see how the servo arm brushes the gun''s side to push it up.



thomasjohnmurphy -> RE: 1/18 RC Sherman (4/16/2008 4:08:43 AM)

more pics



borealis -> RE: 1/18 RC Sherman (4/16/2008 7:19:55 AM)

Thank you! That''s a very compact solution indeed!
I have a suggestion: why don''t you cut (or build) and mount over the servo arm an elevation wheel like the one used in the standard elevation unit, minus the geared border? If the stock wheel is too big, you can cut your own profile (it''s just a triangle) and fit it to your needs.
That would allow for a smoother movement, without sudden returns of the gun to the starting position.
I hope the picture helps to make myself clear.
Another question: which is the rated voltage for the servo you used? I just found max 5V ones.




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