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20 minutes ago, Xoon said:

I don't really see the advantage to this design. 

What about a Ethanol powered Turbocharged V12?

Nowhere in the rules does it state that it needs to be diesel. And a ethanol engine would blow other engines out of the water when it comes to power density. Also, I would consider ethanol as more progressive and environmentally friendly, fitting for such a glories nation as ours. 

 

The problem with ethanol as fuel is all the crunchies will try to drink it :P 

 

on a serious note, diesel has a higher energy density per volume than most fuels that have ethanol in them (from pure ethanol to E10 gasohol). 

 

Anyway, I was messing around with numbers and if I change: 

 

piston diameter = 120mm 

Stroke = 125mm 

18 cylinders (3 banks of 6) 

39 kW/L 

 

i would have an engine outputting ~1950kW (2600hp), but still be surprisingly compact. 

 

For reference, I could simply stack 3 Jumo 205s on top of each other and place them in the front section of my vehicle, and still have enough room for a transmission/drives and some random air/fuel ducts (though cooling the middle engine would be hard). 

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5 minutes ago, Lord_James said:

The problem with ethanol as fuel is all the crunchies will try to drink it :P 

Add a bit of methanol, and they will learn quickly.

 

5 minutes ago, Lord_James said:

On a serious note, diesel has a higher energy density per volume than most fuels that have ethanol in them (from pure ethanol to E10 gasohol). 

While true, it does not translate into engine power. Look at every hypercar, they run on gasoline, and in some cases E85. 

 

5 minutes ago, Lord_James said:

Anyway, I was messing around with numbers and if I change: 

 

piston diameter = 120mm 

Stroke = 125mm 

18 cylinders (3 banks of 6) 

39 kW/L 

 

i would have an engine outputting ~1950kW (2600hp), but still be surprisingly compact. 

 

For reference, I could simply stack 3 Jumo 205s on top of each other and place them in the front section of my vehicle, and still have enough room for a transmission/drives and some random air/fuel ducts (though cooling the middle engine would be hard). 

I am most concerned about the intake and exhaust, cooling should be a non issue if it is watercooled. 

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4 minutes ago, Xoon said:

Add a bit of methanol, and they will learn quickly.

 

That’s just flavor :D 

 

4 minutes ago, Xoon said:

 

While true, it does not translate into engine power. Look at every hypercar, they run on gasoline, and in some cases E85. 

 

I think initial torque is a more valuable thing to have when you’re 10+ tons; those super cars might have some awesome speed, but they also weight like 200kg or something silly. Diesel provides that high starting torque to get moving, which is also why (when not using a turbojet) many MBTs use Diesel engines (I think). 

 

18 minutes ago, Xoon said:

 

I am most concerned about the intake and exhaust, cooling should be a non issue if it is watercooled. 

 

Oh, my intake and exhaust are going to be through the sponsons (intake on the starboard, exhaust on the port). 

 

For cooling, I was thinking of oil cooling, with an optional water/methanol system. 

 

 

Anyway, I’ve found some funny engine designs, like axial internal combustion, wankel, and opposed piston, opposed cylinder. I’m really tempted to use a wankel or an opposed piston axial engine because I like exotic, niche designs. 

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2 minutes ago, Lord_James said:

I think initial torque is a more valuable thing to have when you’re 10+ tons; those super cars might have some awesome speed, but they also weight like 200kg or something silly. Diesel provides that high starting torque to get moving, which is also why (when not using a turbojet) many MBTs use Diesel engines (I think). 

Not really, you can make gasoline engines with high start torque too. To main reason diesel is used by the military is fuel efficiency. 

The issue with having a good torque curve on a gasoline car usually gives it horrible fuel economy. 

 

 

2 minutes ago, Lord_James said:

 

 

Oh, my intake and exhaust are going to be through the sponsons (intake on the starboard, exhaust on the port). 

 

For cooling, I was thinking of oil cooling, with an optional water/methanol system. 

 

 

Anyway, I’ve found some funny engine designs, like axial internal combustion, wankel, and opposed piston, opposed cylinder. I’m really tempted to use a wankel or an opposed piston axial engine because I like exotic, niche designs. 

Just remember to factor in how huge exhaust can get. Especially turbo exhausts. 

 

And I am all for special engines. 

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Well, the D18-120 fits pretty well in the front of my tank: 

 

Spoiler

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location is only preliminary, I'll optimize it better, later. 

 

Also, here's the new turret: 

 

Spoiler

ff1xTrY.png

 

yes, I know the mantlet is going to be big, but that's a given with a 6" gun. 

 

 

 

Completely off topic: 

Spoiler

how do I get the gif in my signature to play, like Jeeps and Loser? 

 

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7 hours ago, Lord_James said:

 

  Hide contents

how do I get the gif in my signature to play, like Jeeps and Loser? 

 

   I just uploaded gif to imgur, made sure that URL have ".gif" and copy-pasted into signature in user settings.

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20 hours ago, Xoon said:

but can do do something like 25mm Alu + 50mm air + 20mm Alu?

Yes.

 

18 hours ago, Lord_James said:

Edit: Can we use the Napier Deltic (or similar) for our vehicles? 

 

Also, can I use polyurethane for insulation? Or are we limited to Urea-formaldehyde and asbestos? 

Sure.

 

18 hours ago, Lord_James said:

1700hp

Sounds fairly optimistic for the size of that engine.

 

15 hours ago, Xoon said:

One thing I have been curious about, is if it is possible to make a X opposed piston, were the piston heads have a wedge shape, and four cylinders meet in the center.

Its possible but doesnt really do much. The Germans experimented with 3-piston OPEs in the 30s.

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Reduced front armour weight to 2.9 tonne per m2 with fuel.  And 2.5 tonne per m2 without fuel.  Defeats 360/960 CE, but only defeats about 800mm KE (depending on fuel).

 

Glacis top protection is still crazy high, but thats inevitable with ricochet angle plate sheathed with reactive armour.

 

 

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Mg Hull casting including glass inserts and 25mm textolite liner. 12.7 tonne

 

Armour packages 11 tonne

 

Frontal arc 60/160 resistant

Side 50/150 resistant. Limited 60/160 area

 

Turret incomplete

 Roof nera/era still to optimise

 

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Alright, so, the D18 engine (and its transmission / intakes / exhaust), I’m theorizing as such: 

 

the D18 itself is a 2-stroke, 18 cylinder, opposed piston, uniflow scavenging, turbosupercharged, turbo-compound, mixed cooling, diesel engine limited to 1850 rpm per shaft, and 2000hp; this should give a hp/t of 23.5 for an 85 tonne vehicle, and  22.2hp/t for a 90 tonne vehicle, which is pretty good if I do say so myself. 

 

The engine is placed in a similar location as my first picture (underneath the hump), with the turbo and super chargers above it, the transmission in the V shaped area between the lower and upper armor cavities, with other systems placed where I can fit them. 

 

 

The chargers are fed from intakes on the starboard sponson (and possibly the section of roof forward of the front propellant rack). These provide the air for ignition as well as cooling; cooling air ducts run along the piston tracks, both inside and outside, while ignition air ducts input from the outside of the engine. Ignition ducts may have a water/methanol system connected to them. Ignition air ducts also run through the liquid cooling system, functioning as a radiator and pre-warming the air. 

 

The liquid cooling system is a basic type using a water/glycol, water/betaine, castor oil based fluids, or other similar mixtures (just water if an emergency), with a pump circulating fluid from around the ignition air ducts, along the combustion chambers of the engine (both inside and out), and back to the ducts. 

 

Fuel is pumped from the tanks in the sponsons, underneath the crew compartment, and in 3 (or 4) forward fuel tanks and input through the middle of the engine. Fuel is typically 40-45 cetane diesel or bio-diesel. 

 

Exhaust is released from ducts on the outside of the engine, each with an expansion chamber for better fuel economy. 6 exhaust ducts (one row of pistons) merge into a single duct, where they pass through small power recovery turbines, (a la R-3350) each recovering 50-60hp, and connect to the turbocharger, the vehicle’s general electrical system and batteries, and a hydraulic assist on the crankshaft, separately. Afterwards, 2 ducts are taken through the bottom of the tank, through lightly armored pipes parallel to the tracks, and outputting along the rear 1/4 of the suspension, perpendicular and positively inclined to the tracks (so not to kick up excessive dust). The third exhaust is ducted into the port sponson, and exhausts horizontally, and to the rear, between the driver and the turret ring. 

 

The transmission is a semi-automatic, continuously variable transmission with “5 forward and 3 reverse” gears. By this, I mean the driver manually puts the transmission into a gear, but the transmission itself has different gears which switch automatically, to smooth out acceleration and power to the sprocket*. The first 2 forward and reverse gears are low speed, high torque gears, and the final 3 forward and last reverse are for higher speed. 

 

 

*There are 2 sets of gears: one set the driver controls, and the other is automatic via the transmission. The driver has his 8 manual, main gears, and the transmission has 10 automatic, intermediate gears. 

 

The driver inputs a gear, and the transmission automatically applies it’s gears in sequence. It looks like this, for speeding up: 

F1-1 

F1-2 

F1-3 

... 

F2-1 

F2-2 

F2-3 

... 

and so on. The transmission always reverts to its first gear when the driver switches his gear, and gears are ratio-ed so that the [X]-10 gear is similar to (but not the same as) the [X+1]-1 gear. This is to minimize lurching, making the ride smoother for the crew. 

 

 

There is also a 80hp 2-stroke, 1 cylinder opposed piston diesel APU mounted in the starboard sponson midway between the propellant rack and turret ring, which powers the electrical system when the D18 is off. 

 

 

Im also looking into OPOC, OP V, and a Wankel engine, but for now, it’s the OP Delta. 

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2 hours ago, Lord_James said:

Exhaust is released from ducts on the outside of the engine, each with an expansion chamber for better fuel economy. 6 exhaust ducts (one row of pistons) merge into a single duct, where they pass through small power recovery turbines, (a la R-3350) each recovering 50-60hp, and connect to the turbocharger, the vehicle’s general electrical system and batteries, and a hydraulic assist on the crankshaft, separately. Afterwards, 2 ducts are taken through the bottom of the tank, through lightly armored pipes parallel to the tracks, and outputting along the rear 1/4 of the suspension, perpendicular and positively inclined to the tracks (so not to kick up excessive dust). The third exhaust is ducted into the port sponson, and exhausts horizontally, and to the rear, between the driver and the turret ring. 

Are you sure you can use compound turbo and a ordinary turbo? Wont the compound turbo rob the exhaust of all its energy? 

Also, will the engine run at a constant rpm? If not, I am not sure if a compound turbo would be worth it. 

If you want the maximum out of the turbo, you can use a 3 stage turbo setup, and small, medium and large turbo to cover the entire range and pressure.  I don't remember if variable geometry turbos are invented yet. 

Also, is the vehicles auxiliary power, powered by the exhaust? 

 

 

2 hours ago, Lord_James said:

The transmission is a semi-automatic, continuously variable transmission with “5 forward and 3 reverse” gears. By this, I mean the driver manually puts the transmission into a gear, but the transmission itself has different gears which switch automatically, to smooth out acceleration and power to the sprocket*. The first 2 forward and reverse gears are low speed, high torque gears, and the final 3 forward and last reverse are for higher speed. 

Why do the driver need theses gears? 

Also, if you want better economy, why not simply have a economy and power option for the driver. 

 

9 hours ago, Kal said:

Mg Hull casting including glass inserts and 25mm textolite liner. 12.7 tonne

 

Armour packages 11 tonne

 

Frontal arc 60/160 resistant

Side 50/150 resistant. Limited 60/160 area

 

Turret incomplete

 Roof nera/era still to optimise

 

How weld-able is this magnesium alloy? 

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Magnesium alloy is generally better for welding than aluminium.

 

But 

 

Aluminium makes better sheet and plate than Magnesium.

 

But 

 

Magnesium makes better castings than Aluminum.

 

So while Magnesium is better for welding than Aluminum, much less welding is used with Magnesium because its generally a casting anyway.

 

Magnesium is sweet for castings, but its just not worth it for sheet or plate work. 

 

The alloy i would suggest is ZE41, popular from late 1940s to late 1960s.

https://www.slideshare.net/mobile/GkhanBier/mg-alloys-in-industry

Edited by Kal
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2 hours ago, Xoon said:

Are you sure you can use compound turbo and a ordinary turbo? Wont the compound turbo rob the exhaust of all its energy? 

 

Pretty sure, the super charger is run via a mechanical system, and the turbocharger is powered by one of the turbo scavengers. 

 

2 hours ago, Xoon said:

 

Also, will the engine run at a constant rpm? If not, I am not sure if a compound turbo would be worth it. 

If you want the maximum out of the turbo, you can use a 3 stage turbo setup, and small, medium and large turbo to cover the entire range and pressure.  

 

Not quite, but it’s not suppose to vary past 1600-1850 rpm. 

 

3 hours ago, Xoon said:

 

Why do the driver need theses gears? 

Also, if you want better economy, why not simply have a economy and power option for the driver. 

 

More precise control? Idk

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BMP 3

30mm 2a72 has ke about 180,000j, exit velocity about 960-1120m/s

100mm 2a70 has ke about. 480,000 to 840,000j, exit velocity 250-350m/s

 

Resolve for different durations, turns out that the 30mm and 100mm have same force on vehicle structure, but the 100mm has a longer duration.

 

Hmmmm

 

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So if proposed tank uses russian 57mm autocannon, ke is 1,425,000j, exit velocity 1000m/a

 

To balance force on vehicle allows HEAT

91mm At 940m/s

105 mm at 760m/s

125 mm at 660m/s

160 mm at 500m/s

 

Seeing how easy it is to defeat smaller HEAT warheads, the complementary cannon is either the 160 mm at 500m/s. (Is is similar ratio to BMP 3 guns)  or just go with the 90mm and make that an auto cannon also.

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18 hours ago, Kal said:

Magnesium alloy is generally better for welding than aluminium.

Interesting, I always thought magnesium was very hard to weld.  I guess it stems from the fear of the entire work piece catching fire, even if it is very unlikely. 

 

 

15 hours ago, Lord_James said:

Pretty sure, the super charger is run via a mechanical system, and the turbocharger is powered by one of the turbo scavengers. 

Do you use the supercharger as a blower or for better torque and low end RPM? 

 

For the compound turbo, is it something like this:
800px-NomadSchematic_185kBpng360kB.png

 

I suppose that you could have a compound turbo sized so that it spools up at a large way of the rev range. 

For example. Lets say the tank spends most of its time between 800-1400 RPM, then it would be able to produce enough exhaust gas to power the turbine at roughly 8-900 RPM, and for the higher rev range rarely used, a turbocharger would be employed? 

 

So, if I understand the engine correctly, at low RPM, the supercharger would be used to provide power and compression instead of using the crank to compression.  At medium RPM the recovery turbine would have been spooled up to max, and at higher RPM the supercharger would be decoupled by a magnetic clutch or similar and the turbocharger would kick in. 

 

Am I correct? or am I completely off?  

 

Also, are gas turbine turbochargers allowed, @N-L-M

 

Quote

Not quite, but it’s not suppose to vary past 1600-1850 rpm. 

 

 

More precise control? Idk

Well, the thing is, a CVT, is a continuously variable transmission, meaning infinite gears in theory. 

Which means you can have a gearbox with a ratio of 1 to 20, with anything in between. Like 15, 12, 7, 2, 10,12312321 etc. 

 

This means that the engine will always have the appropriate gear ratio for the RPM. No gear selection, just the engine humming happily at its optimal RPM. 

You can, however have a selector for economy and power. 

 

Lets say the engine produces its max power at 3000RPM, but runs the most efficient at 2000RPM, then the transmission would aim to always have the engine at 2000RPM for economy, or 3000 RPm for max power. 

You should have a "first gear" and reverse gear though, as a conventional CVT provides poor torque initially,  and is incapable of switching direction. 

 

It would have 3 gears, first gear, continuous gear and reverse. 

 

 

Love your engine so far btw, certainly a neglected design in the automotive world. 

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3 hours ago, Xoon said:

Also, are gas turbine turbochargers allowed

Sure, but complex engine designs like these are bound to lead to trouble. In particular, trying to squeeze significantly more power per dispacement than the Kharkovite engine is not going to make you a happy camper.

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Re Mg vs Al for welding.

 

The Mg is easier for fine welding like bikes and lightweight structures, but is unsuitable for thick welds.  Mg welding uses only about 40% of the heat for the same thickness as. Al welding but is unsuitable for deep penetrating welds because the Mg boiling point is a lot lower than Al boiling point.  (Even though the melting points are almost the same.)

 

Al obviously conducts heat away from the weld a lot faster than Mg.

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1 hour ago, N-L-M said:

Sure, but complex engine designs like these are bound to lead to trouble. In particular, trying to squeeze significantly more power per dispacement than the Kharkovite engine is not going to make you a happy camper.

Pfft, of course not, who would want to squeeze more power out of  it? he he

 

* discreetly crumples paper and throws in trash*

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