TRACKS!

I'm back again with another update, the tracks are now on! At this stage it starts to look like a tank!



Close up shot of the tracks, they are made of treadmill belt and polyurethane resin.

Idler wheel, this is by far the hardest thing I've had to make yet. I wanted it to be cast in a single piece which made the mould making process very tricky...

Batteries, 24v 24ah setup. Also visiable is the kill switch at the bottom of the pic.



Very Tank like indeed.

Some stats on the resin im using.

Comp strength: 4500psi

Tensile strength: 3000psi

Shore Hardness: 70D

Next up, electronics! Stay tuned, I'll upload a video of it tearing around soon.

=Mr.TigerAce=

Idler wheel

A little tricky to make the mould, but it looks the part I think.



=Mr.TigerAce=

WHEELS

I decided to make the wheels look semi accurate in terms of scale, and as I wasn't keen on machining 24 wheels to look good, I decided to cast them in a urethane resin. This means, I only need to make 1 "master" which looks right, then simply make a mould using silicone rubber which captures every detail perfectly. I'll go further into mould making in a later post.

Here is an overall shot of the running gear (minus idlers). All wheels, return rollers, idlers and drive sprockets are cast from "smooth cast 305" its a very rigid urethane resin, casts very nicely, easily tintable. The road wheels, idlers and return rollers all ride on sintered bronze bushings. The drive sprocket is bolted to a flange which is welded to the drive shaft, the bolt heads will be covered in a scale looking "hub".


These are the masters for the road and return wheels. They are just made of styrene, mostly to get the look close, once these are made its easy to cast stronger parts using resins.



Same deal as above, styrene, little bit more complex as the teeth need to be perfect to mesh with the tracks.



The adjustment plate mods I was talking of earlier. Just makes them less likely to flex



Here are the motors installed, tight squeeze, but I guess that's the pay off when its all planned, everything fits! everything is kyed so its all solid as and never gonna slip. Thats very important in a vehicle that constantly changes direction (turning) as the shafts are under huge stress!



Smoth cast, www.smoothon.com
chains, kyed shafts www.surpluscenter.com

Next tracks! as promised.

=Mr.TigerAce=

THE HULL

As the hull was lasercut it went together beautifully, it's very important to make sure everything is square whilst assembling so that the swing arm shafts and drive sprocket shafts run true to each other, no one wants a crab walking tank.... Also because the entire thing is 2mm steel, it was easily welded together in a matter of hours with a gasless mig welder.

You must make sure to "tack" weld it all together first to check for square, then only do very small seem welds, as you don't want to introduce to much heat into the steel as it will warp. It's best to take your time and do it properly once.

here is a pic of the assembled lower hull with road wheel swing arms, idler shaft and return roller shafts installed.



This is the suspension setup. I used eyebolts so I can adjust spring tension and ride height, the shafts ride on sintered bronze bushings. A simple "cotter" pin holds the shafts in place (temporarily fitted) as they see virtually no "pull" load at all. note, I have since added supports to the adjustment plates as they were flexing under load.



This bulkhead removes a lot of the "flex" from the hull, its also there to hold cooling fans, as well as provide support for the battery mount.



Here are the drive shaft bearings (acquired from, http://www.surpluscenter.com/), located in the front of the hull. Notice this area is reinforced with 5mm steel plate as it has to handle a decent amount of force. The drive shaft are 5/8" keyed steel, the swing arm, road wheel and return roller shafts are 1/2" bright steel and the idler shaft is 5/8"



All eyebolts, springs and bushings were purchased from www.mcmaster.com

Stay tuned, next up wheels and tracks!

=Mr.TigerAce=

DESIGN

Designing an RC tank is not an exact science, a few factors to take into account.

• The scale detail, do you want your tank to look like a replica, or are you happy with reduced detail to speed up construction?
• The performance, race tank? scale speeds? run time? these are all decisions that need to be made before you start designing
• Materials, wood, steel, aluminium? this is usually determined by the workshop facilities you have access to.

Once you know what you want your tank to do, you can start designing. For me this is my favorite process. I use a basic drawing program (coreldraw x4) which lets me get the basic dimensions down in vector format, which also enables me to send plans to laser cutters and other cad type machines.

For this tank I have decided to go all steel and composite materials. Reason being, steel is easy to work with, you can cut, shape, weld and manipulate it relatively easily. Steel also allows the most internal space as you can use thin sheet metal with a limited amount of reinforcement.

I have also decided to get the entire hull lasercut, this ensures a perfect fit with minimal effort required for final Assembly. The biggest con being, the entire tank needs to be designed from top to bottom before sending off your drawings to the cutter, this can take literally hundreds of hours. Worth it in the end though.

Once I had established the hull material its time to look at motors. I want this tank to have about 350-400 RPM at the drive wheel, this gives me roughly 8.5 - 9.5 km/h. As its made of steel, its going to be heavy so I need some beefy drive motors. I came across these (http://www.monsterscooterparts.com/24v-350w-motor-dirt-quad.html) which look perfect for my application. Reasonable price too.

I now know, I need a 24v battery setup, I've chosen to use 4, 12v 12ah sla batteries, this gives me 24v at 24ah which should give me 45-60min run times.

At this stage its also wise to pick any other components you may need to use, speed controllers, RC transmitters, elevate and rotate setup to name a few. (browse through, http://www.robotmarketplace.com/ to find suitable parts)

Setting a speed of 8-9 km/h means this tank is going to be relatively fast, in harsh conditions a tank of this speed with no suspension will tear itself to pieces. So I'm going for a complete suspension setup, each road wheel is independently sprung, this gives a nice smooth ride to protect the delicate electronics, not to mention it looks sweet! (springs and other misc parts can be found here, http://www.mcmaster.com/)

For the tracks I'm going with a "TTS" (Tyng track system) which is basically a belt with "cleats" attached to both sides to form the track. As the tank is suspended, I need to use a sprocket driven track to allow road wheel movement, a friction track can not handle such movement. This system is good because its light, cheap and performs really well. Cons being, labour intensive to build.

More to follow...

=Mr.TigerAce=

STEP ONE; SELECTION

There are a number of factors that have helped me decide which tank to build, first and foremost is looks.

I tend to stick to German tanks simply for looks alone, the vast majority have a menacing look about them.

The second factor for me is size, I like the smaller style tanks because they are cheaper to build, easier to handle and most importantly, harder to hit with paintballs!

The third and final factor is, whether or not I want a functional turret. I tend to say no to this and end up with assault guns, or tank destroyers.

So for my latest build I'm going with a Sturmgeschutz 3 Ausf G, in a 1943 "kursk" style setup.



Once I have selected the vehicle I want to model, I buy a 1/35th plastic kit of it and use that, along with reference photos to get scale measurements.

1/35th models www.dragonusaonline.com
reference pics and info www.wwiivehicles.com

=Mr.TigerAce=

Welcome!

Hi all, welcome to my blog! Basically I set this up to document the processes involved with building 1/6th scale RC Tanks and equipment, specifically designed to participate in scale battles. At 1/6th a typical tank is around 1400mm long.

The idea is, two or more tanks are pitted against each other on a battlefield, each trying to destroy the enemy. The tanks fire paintballs so its a simple matter of hitting the enemy with a predetermined number of rounds, well in theory...

This raises a few very interesting design challenges, some of which I will try to document shortly.

=Mr.TigerAce=