Help me design a working miniature tank gun

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LavaRed
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Help me design a working miniature tank gun

Post by LavaRed » Sun Jul 15, 2012 11:42 pm

So, crazy LavaRed project.
Working on the armoured tank drone, again. I have all of the steel armour plate cut (1/4" and 1/2" thick), but that's about it. I've designed the whole suspension and running gear, still need to design the transmission and final drives and acquire a small gasoline motor.
It'll be a fully propietary design in 1/6 scale meant to model a non-existing MBT.
But I'm getting ahead of myself. I need to design the gun on the tank. So far what I've come up with is a 12 gauge setup, with a 40" long barrel. I would prefer a semi-automatic setup, so that it can have multipl-shot capability. I would prefer a capacity of at least 6 rounds. Now the ammunition I've thought of would be propietary as well: Machined brass 3" 12 gauge shell casings with thicker walls so that a more powerful charge can be put in, and machined brass rifled slugs. The shells would also be re-loadable, so that I don't need to have more than 6 or so. But normal shotgun shells should also be used for other applications (hunting, etc.).
So, what I'd like some help with would be designing a suitable mechanism. Something simple enough to be built here, but sound enough not to break and reliable enough to be fully autnomous. I'm thinking of using a custom barrel blank and a machined receiver. I would also prefer a box magazine instead of a tubular one. and a non-gas operated mechanism.
Incidentally the gun would be set-up to recoil in a cradle inside the turret, just like a real tank.
I guess I want to get everything as near a modern MBT as possible. I'm even thinking of putting in miniature Chobham armour, if I can find a local ceramic manufactury that will custom-make miniature ceramic-armour panels.
So, what are your thoughts gentlemen?
Thanks,
Lava
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Re: Help me design a working miniature tank gun

Post by ghostdog662 » Mon Jul 16, 2012 12:04 am

Is it revolution time?
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Re: Help me design a working miniature tank gun

Post by LavaRed » Mon Jul 16, 2012 12:57 am

ghostdog662 wrote:Is it revolution time?
Thank God no! :D

I'm just having fun and trying to get into the future of land drones.
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Re: Help me design a working miniature tank gun

Post by rogerme » Mon Jul 16, 2012 2:17 am

A anti drone drone? I await the new daily to see who is the first to get arrested for taking a drone out somehow. You know it is gonna happen it is just a question of when and where.
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Re: Help me design a working miniature tank gun

Post by LavaRed » Mon Jul 16, 2012 3:30 am

rogerme wrote:A anti drone drone? I await the new daily to see who is the first to get arrested for taking a drone out somehow. You know it is gonna happen it is just a question of when and where.
No. What I had more in mind was a hunter-killer drone tank for areas where it's so heavily forested that an aircraft is not feasible.

Or failing that, a fun toy that I can use with my 1/6 scale figures. It's the whole reason why it's 1/6 scale in the first place.
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Re: Help me design a working miniature tank gun

Post by Baffled » Mon Jul 16, 2012 9:24 am

From a gunsmith/machinist perspective, why reinvent the wheel? Use a stock shotgun (like a Browning A5 recoil operated) and have that form the basis for your tank gun. Externally, it could be entirely different. Hide the breech inside the tank.

If you do this thing from scratch, it's going to be a bear. Look at an exploded parts diagram for a reliable, modern SA shotgun. Designers work on these for years before they succeed.

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Re: Help me design a working miniature tank gun

Post by rogerme » Mon Jul 16, 2012 11:18 am

Baffled wrote:From a gunsmith/machinist perspective, why reinvent the wheel? Use a stock shotgun (like a Browning A5 recoil operated) and have that form the basis for your tank gun. Externally, it could be entirely different. Hide the breech inside the tank.

If you do this thing from scratch, it's going to be a bear. Look at an exploded parts diagram for a reliable, modern SA shotgun. Designers work on these for years before they succeed.
That is sounds BA. Of course the fact I just took in and redid a savage a5 copy gives me idears....
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Re: Help me design a working miniature tank gun

Post by MCKNBRD » Mon Jul 16, 2012 12:39 pm

Pick up a Saiga shotgun. Or, conversely, a good machinist's diagram of one. Box-fed, semi-auto 12ga.

Springs and weights could be adjusted to change some dimensions, and you've got your mini-tank cannon.

I'd like to see your projectiles, too. Look at the APFSDS loads we have for MBT's now...and make it out of cold rolled steel instead of brass. Have the shell made of CRS, too, and have it thread together with a small, thin composite/cardboard disk on the front, but screwed together at the back to ease reloading and assembly. Heck, if I had the equipment, I'd love to build a sample just for S&Gs.

You're going to have a helluva time aiming, though...

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Re: Help me design a working miniature tank gun

Post by mx201er » Mon Jul 16, 2012 12:47 pm

^^like they said, I think it would be easiest to modify an existing firearm to fit the purpose if you are looking for semi auto..

I really like the idea and would love to see pictures as it comes along :D Good luck LavaRed
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Re: Help me design a working miniature tank gun

Post by Enfield577 » Mon Jul 16, 2012 3:34 pm

I got a Saiga 12 and think it would be the way to go, already prooven, has box mag and a short action (no recoil spring in the stock)

Can't wait to see this thing :lol:
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Re: Help me design a working miniature tank gun

Post by Enfield577 » Mon Jul 16, 2012 3:34 pm

I got a Saiga 12 and think it would be the way to go, already prooven, has box mag and a short action (no recoil spring in the stock)

Can't wait to see this thing :lol:
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Re: Help me design a working miniature tank gun

Post by LavaRed » Mon Jul 16, 2012 4:38 pm

Thanks. I guess it will be easier. I'll look for a used shotgun, temove the furniture and design my recoil cradle so that the gun can be screwed into it. I guess I'll weld on a barrel extension to make the barrel look thicker and longer like an MBT.

For aiming I have thought of using one of those small hobby cameras with some sort of adjustable reticle or red-dot. Same for driving. Both periscope mounted, so that they can be protected inside the tank.

Thanks for the shell idea. Having it threaded sounds awesome so that I don't need to crimp it for reloading.

In a while I'll post pics of progress so far.
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Re: Help me design a working miniature tank gun

Post by LavaRed » Mon Jul 16, 2012 8:09 pm

This is what I have so far:

Image

Image


This is what I want the end product to look like:

Image

Image

Image
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Re: Help me design a working miniature tank gun

Post by Historian » Tue Jul 17, 2012 9:20 am

LavaRed wrote:
rogerme wrote:A anti drone drone? I await the new daily to see who is the first to get arrested for taking a drone out somehow. You know it is gonna happen it is just a question of when and where.
No. What I had more in mind was a hunter-killer drone tank for areas where it's so heavily forested that an aircraft is not feasible.

Or failing that, a fun toy that I can use with my 1/6 scale figures. It's the whole reason why it's 1/6 scale in the first place.
Lava, having once or twice traversed 'heavily forested' country sides I tried hard to imagine a mini-tank operating in that environ.
In particular I recalled the WW II films of the battle in Normandy among the hedgrows.

Ref: << http://www.militaryhistoryonline.com/ww ... akout.aspx >>

For an anti-drone ground weapon, on the other hand, applying American ingenuity [ that
wonderful trait now so despised and reviled in the making of wealth by the Marxist-in-Chief ]
that solved the Normandy the tank stopping hedge row problem, consider the possibility
of some novel approach, say along the line of a device to blind the optical drone sensors : e.g.,
a Smatter Spray Foam Cannon.

Firing from a launcher the can would upon impact splatter the drone, covering it and its optics
with sticky goo. Right out of a Road Runner and Wiley Coyote cartoon.

Have you ever tried to remove bird guano from your windshield?

In fact, in a Mad Comic Cartoon moment, I just drew in my mind a set of frames
where one would collect a bevy of over stuffed birds and like hunting falcons
train them to perform 'evacuations' on the intruders.

OK, I will stop with the CRAPPY freewheeling.

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Re: Help me design a working miniature tank gun

Post by Blaubart » Tue Jul 17, 2012 11:48 am

Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
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Re: Help me design a working miniature tank gun

Post by LavaRed » Wed Jul 18, 2012 1:44 am

Blaubart wrote:Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
That is the general idea.

But right now I'm stuck on how to control everything with a 6 channel transmitter. I need to be able to control the throttle, engine clutch, forward and reverse, transmission speeds, left and right track brake/clutch asemblies, turret traverse, gun elevation, and firing.
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Re: Help me design a working miniature tank gun

Post by Historian » Wed Jul 18, 2012 8:54 am

LavaRed wrote:
Blaubart wrote:Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
That is the general idea.

But right now I'm stuck on how to control everything with a 6 channel transmitter. I need to be able to control the throttle, engine clutch, forward and reverse, transmission speeds, left and right track brake/clutch asemblies, turret traverse, gun elevation, and firing.
Pay attention to your communication link. Will a local garage door opener also trigger your system?

A home built frequency hopping transmitter/receiver ensures that only you can control the 'beast'.

( e.g., << http://www.arrl.org/files/file/QEX_Next ... eature.pdf >> )

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Re: Help me design a working miniature tank gun

Post by ghostdog662 » Wed Jul 18, 2012 12:30 pm

You might be able to borrow some ideas from the Howe & Howe badger personal tank.

There are plenty of youtube videos and stuff on discovery channel about them too.

www.youtube.com/watch?v=oSvyYNf68eg
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Re: Help me design a working miniature tank gun

Post by LavaRed » Wed Jul 18, 2012 12:59 pm

Historian wrote:
LavaRed wrote:
Blaubart wrote:Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
That is the general idea.

But right now I'm stuck on how to control everything with a 6 channel transmitter. I need to be able to control the throttle, engine clutch, forward and reverse, transmission speeds, left and right track brake/clutch asemblies, turret traverse, gun elevation, and firing.
Pay attention to your communication link. Will a local garage door opener also trigger your system?

A home built frequency hopping transmitter/receiver ensures that only you can control the 'beast'.

( e.g., << http://www.arrl.org/files/file/QEX_Next ... eature.pdf >> )
Excellent! I hadn't thought of that. I'll ask for my dad's input (and possibly the loan of equipment) since he's a HAM. Maybe he can build me a small repeater so that I can dramatically boost my signal range.
:D
You get a big thanks :D
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Re: Help me design a working miniature tank gun

Post by sillycon » Wed Jul 18, 2012 3:37 pm

LavaRed wrote:
Blaubart wrote:Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
That is the general idea.

But right now I'm stuck on how to control everything with a 6 channel transmitter. I need to be able to control the throttle, engine clutch, forward and reverse, transmission speeds, left and right track brake/clutch asemblies, turret traverse, gun elevation, and firing.
I'd be tempted to "mix" the throttle to the forward/reverse channel. The more forward/backward you move the stick, the more throttle/faster it goes. With a centrifugal gearbox and a slipper clutch you also don't need to bother with gear changing or clutches.

That basically leaves you with a 6ch setup looking like below:

1) Throttle/forward/reverse
2) Left/right (a servo controlling an additional slipper mechanism would facilitate this on a tracked vehicle)
3) Turret elevation
4) Turret traverse
5) Firing
6) [open] (or perhaps maybe a brake if you didn't want to tie that in with CH1)

Does your radio setup have a momentary switch on one of the channels for firing, or are you "stuck" having to use a SPST?

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Re: Help me design a working miniature tank gun

Post by LavaRed » Wed Jul 18, 2012 9:55 pm

sillycon wrote:
LavaRed wrote:
Blaubart wrote:Why does aiming have to be difficult? Attach a GoPro camera to the barrel and align it. Hook that up to a wireless transmitter and put crosshairs on the monitor. Aim by looking at the screen so it's natural, not by looking at the tank and trying to figure out where it's aiming.
That is the general idea.

But right now I'm stuck on how to control everything with a 6 channel transmitter. I need to be able to control the throttle, engine clutch, forward and reverse, transmission speeds, left and right track brake/clutch asemblies, turret traverse, gun elevation, and firing.
I'd be tempted to "mix" the throttle to the forward/reverse channel. The more forward/backward you move the stick, the more throttle/faster it goes. With a centrifugal gearbox and a slipper clutch you also don't need to bother with gear changing or clutches.

That basically leaves you with a 6ch setup looking like below:

1) Throttle/forward/reverse
2) Left/right (a servo controlling an additional slipper mechanism would facilitate this on a tracked vehicle)
3) Turret elevation
4) Turret traverse
5) Firing
6) [open] (or perhaps maybe a brake if you didn't want to tie that in with CH1)

Does your radio setup have a momentary switch on one of the channels for firing, or are you "stuck" having to use a SPST?
http://www.ebay.com/itm/Futaba-6-channe ... 3f19d65bc4

This is my radio system. Can the controls be mixed with that?
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Re: Help me design a working miniature tank gun

Post by sillycon » Thu Jul 19, 2012 11:26 am

I'm not sure if you mean that specific listing is the one you bought from, or "this is like the radio I have".

You may or may not be aware, but certain frequencies are "reserved" for specific uses in the R/C "world" -- you have "surface" frequencies and "air" frequencies. The radio in that listing/auction is an air radio, not a surface radio, and as such should be used only for flying vehicles. If you swapped out to a 2.4ghz system, there is no difference (frequency wise) for air or surface, and it also would eliminate any sort of interference worry as the systems are generally trunking and/or keyed.

Anyway, frequency considerations aside, the "mixing" can be done outside of the radio system. This is especially true if you were to instead go with an electric motor as the speed controller will control the "throttle" and forward/reverse.

Going with a gas motor, you could use a mechanical linkage to make it happen, or you could use ch 6 to act as a fwd/rev switch (it could move a lever on the transmission) then your "throttle" stick would be either forward or reverse depending on the position of the selector switch.

The methodology you chose is going to simply come down to the parts/design you plan use in the build.

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Re: Help me design a working miniature tank gun

Post by LavaRed » Thu Jul 19, 2012 2:56 pm

sillycon wrote:I'm not sure if you mean that specific listing is the one you bought from, or "this is like the radio I have".

You may or may not be aware, but certain frequencies are "reserved" for specific uses in the R/C "world" -- you have "surface" frequencies and "air" frequencies. The radio in that listing/auction is an air radio, not a surface radio, and as such should be used only for flying vehicles. If you swapped out to a 2.4ghz system, there is no difference (frequency wise) for air or surface, and it also would eliminate any sort of interference worry as the systems are generally trunking and/or keyed.

Anyway, frequency considerations aside, the "mixing" can be done outside of the radio system. This is especially true if you were to instead go with an electric motor as the speed controller will control the "throttle" and forward/reverse.

Going with a gas motor, you could use a mechanical linkage to make it happen, or you could use ch 6 to act as a fwd/rev switch (it could move a lever on the transmission) then your "throttle" stick would be either forward or reverse depending on the position of the selector switch.

The methodology you chose is going to simply come down to the parts/design you plan use in the build.
Oops. Yes, that is the specific radio I bought. Is it possible to swap out the frequency?

Yes, I had thought of using mechanical linkages.

For forward/reverse, I thought of using the position of the throttle-stick on the vertical axis, mixed with the motor's throttle (would require mixing both a forward/reverse linkage servo and a throttle linkage servo.

For left track or right track braking, I had planned to use the upper left, lower left, upper right, lower right positions of the throttle stick, combining the throttle linkage, forward/reverse linkage, and left or right track brakes.

For pivot turns (tank turning on its axis with tracks moving in opposite directions, I had thought to use the position of the throttle stick on the horizontal axis. This is accomplished by putting the transmission in neutral and driving the tracks through the third differential, which draws power from the transmission input shaft. This would require having the transmission in neutral (with the speed-shifting control), and the throttle servo mixed with the forward/reverse linkage servo.

As you can see, the forward/reverse unit will be separate from the transmission unit, so as to enable the tank to use all speeds in forward or reverse.

Therefore, locomotion will use up three channels:
1) Throttle function and forward reverse (2 servos on the same channel)
2) Speed shifting (1 servo)
3) Track brakes (2 servos on the same channel, or 1 servo with linkages)

For the turret, I will require 3 functions:
1) Turret traverse (Simply accomplished through high RPM servo, worm and pinion gears)
2) Gun elevation (low RPM servo, worm and pinion gear).
3) Firing (High RPM servo or stepper motor, worm and pinion gear).

For the gun I have decided to depart from the original idea and using a completely manual shotgun. Therefore, the servo would have to carry out both loading, firing, and extraction. I have thought of performing this by programming the motor to respond to one of the 3 position switches. The gun would be gravity-fed from a flexible tray, and would extract out the bottom. A mechanism would allow a certain number of motor revolutions to ram the mechanism forward, feeding the shell from the "lips", a second number of turns would release the firing pin, and a further number of turns would extract the case and leave the mechanism open to prevent cook-off.

So I just need to figure out how to mix all of the servo functions. I may still need to buy a further 2 or 4 servos.
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Re: Help me design a working miniature tank gun

Post by sillycon » Thu Jul 19, 2012 3:45 pm

LavaRed wrote:
sillycon wrote:I'm not sure if you mean that specific listing is the one you bought from, or "this is like the radio I have".

You may or may not be aware, but certain frequencies are "reserved" for specific uses in the R/C "world" -- you have "surface" frequencies and "air" frequencies. The radio in that listing/auction is an air radio, not a surface radio, and as such should be used only for flying vehicles. If you swapped out to a 2.4ghz system, there is no difference (frequency wise) for air or surface, and it also would eliminate any sort of interference worry as the systems are generally trunking and/or keyed.

Anyway, frequency considerations aside, the "mixing" can be done outside of the radio system. This is especially true if you were to instead go with an electric motor as the speed controller will control the "throttle" and forward/reverse.

Going with a gas motor, you could use a mechanical linkage to make it happen, or you could use ch 6 to act as a fwd/rev switch (it could move a lever on the transmission) then your "throttle" stick would be either forward or reverse depending on the position of the selector switch.

The methodology you chose is going to simply come down to the parts/design you plan use in the build.
Oops. Yes, that is the specific radio I bought. Is it possible to swap out the frequency?

Yes, I had thought of using mechanical linkages.

For forward/reverse, I thought of using the position of the throttle-stick on the vertical axis, mixed with the motor's throttle (would require mixing both a forward/reverse linkage servo and a throttle linkage servo.

For left track or right track braking, I had planned to use the upper left, lower left, upper right, lower right positions of the throttle stick, combining the throttle linkage, forward/reverse linkage, and left or right track brakes.

For pivot turns (tank turning on its axis with tracks moving in opposite directions, I had thought to use the position of the throttle stick on the horizontal axis. This is accomplished by putting the transmission in neutral and driving the tracks through the third differential, which draws power from the transmission input shaft. This would require having the transmission in neutral (with the speed-shifting control), and the throttle servo mixed with the forward/reverse linkage servo.

As you can see, the forward/reverse unit will be separate from the transmission unit, so as to enable the tank to use all speeds in forward or reverse.

Therefore, locomotion will use up three channels:
1) Throttle function and forward reverse (2 servos on the same channel)
2) Speed shifting (1 servo)
3) Track brakes (2 servos on the same channel, or 1 servo with linkages)

For the turret, I will require 3 functions:
1) Turret traverse (Simply accomplished through high RPM servo, worm and pinion gears)
2) Gun elevation (low RPM servo, worm and pinion gear).
3) Firing (High RPM servo or stepper motor, worm and pinion gear).

For the gun I have decided to depart from the original idea and using a completely manual shotgun. Therefore, the servo would have to carry out both loading, firing, and extraction. I have thought of performing this by programming the motor to respond to one of the 3 position switches. The gun would be gravity-fed from a flexible tray, and would extract out the bottom. A mechanism would allow a certain number of motor revolutions to ram the mechanism forward, feeding the shell from the "lips", a second number of turns would release the firing pin, and a further number of turns would extract the case and leave the mechanism open to prevent cook-off.

So I just need to figure out how to mix all of the servo functions. I may still need to buy a further 2 or 4 servos.
Some radios are more flexible than others. On some, you can change "channels" within a frequency with a crystal change, but typically I don't believe you can move from 72mhz to 75mhz that easily. Frankly, it's been a good ~15 years since I've messed with the non-2.4ghz radios so a lot of the details have faded from memory.

I honestly have to wonder if you can really extract all the functionality you're looking for from a basic analog 6ch radio. I think you may find yourself better off moving to a more modern 2.4ghz computer radio with additional channels.

For a project like this, I'd do the radio last. Get everything together, and the systems figured out, and then get the radio to match.

As for the gun, I'd look VERY heavily at the Saiga suggestion myself. There is PLENTY of recoil energy left after the action cycles to also have your reciprocating gun carriage and all it will need is a mount. There are already high-cap mag systems available for it as well. All you'd really need then is perhaps a SBS stamp (I'm not sure what OAL would be on a 18" bbl Saiga with no rear stock, but it seems to me that it could be under 26") and a mount.

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Re: Help me design a working miniature tank gun

Post by Historian » Thu Jul 19, 2012 4:24 pm

Lava,

An added thought. If you are dealing with 'line-of-sight' then you can control
via green laser and corner reflectors on the tank actuators and computer.

I actually knew the physicist who in the mid Century invented it from "just knowing high
school geometry", said with a Canadian twinkle in his eye. He was also
a world class shooter ... 1938 Camp Perry at 1,000 yards, iron sights on
his Star-Guage Springfield rifle.

Fact on a corner reflector: no matter from where you aim at it it will
reflect back to you ... as evidenced by the corner reflectors left by the
Astronauts on the Moon so that earth based lasers can track movement.

Ref: << http://en.wikipedia.org/wiki/Corner_reflector >>

Using FORTH programming language you can program the system
to let you send corrective commands and get feed-back with no signal jamming.

It might be complicated but worthy of consideration.

Best.

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