Qoonpooka
10/27/21 03:46 PM
40.132.250.62
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Been prepping to run a MW tabletop campaign and thinking about the MacGuyver nature of periphery tech bases and how they make 'mechs work even with archaic equipment. Since the campaign is planned to run 3030-3080, I want to use the 'never say die' design philosophy of minor periphery states to foreshadow the PCs suddenly finding themselves in the opposite side of the equation in the 3050s.
One of the things that came up for me was engine power/mass ratios.
There's a couple of places where a dedicated engineer would realize that two engines in a given rating are lighter (but bulkier) than a single engine of double that rating.
E.g. the 50-rated fusion engine is 0.5 tons. The 100-rated is 1.5 tons. So 2x50-Rated saves you 33% on engine mass. Half a ton of engine savings for a 5/8 20-tonner is a pretty big deal actually. Hell, for a Locust, if you can shoehorn two 80-rated engines to replace the 160, you get your 8/12 speed for a whole ton less. Ask the LCT-1S if 1 ton more armor makes a difference....
I'm guessing this is literally where XL engine tech even comes from as a concept, but I'm curious for what sorts of rules/mechanics solutions people have devised for such shenanigans. Off the top of my head, it seems that engines take six slots, which conveniently maps to an XL engine's bulk. (You end up even lighter than XLs though, in many cases.) Redundant engines seem like they might not need to knock the 'mech out on torso loss, but I know enough about electrical systems to know that sudden loss of half your power supply will almost certainly cause your safety systems to trip and force the shutdown anyway. Given the duct tape & bailing wire grade of this kind of engineering, I can also see these systems being even more fragile in general since they'd need to be frequency-synchronized unless you had a bunch of rectifier equipment, etc. to condition the supplied power.
The problem I see comes towards the heavier side of things: a pair of 200-rated engines is comically superior to even a 400XL, so there's a need for some kind of introduced penalty or simply a hard cap beyond which "these engines are too powerful to be safely run in tandem, that's why the weight of their higher-rated parent is so huge." (I'm assuming the in-universe justification for engine mass bloat has to do with operating temperatures pushing beyond materials engineering of the day.)
Anyway, I'm envisioning some borderline franken-'mech bullshit from the deep periphery using stuff like this and packing rocket launchers, vehicle rifles, and BAR-rated armor.
What sorts of stuff have people already noodled on in this space though?
Edited by Qoonpooka (10/28/21 10:28 AM)
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Cray
10/27/21 08:09 PM
71.47.151.234
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Yep, my gaming group tried twin engines (even triple) back around 1986-1988 when we were doing some weird things. (For example, the original rules - before ultra-autocannons came out - didn't clarify how often you could fire a gun per turn. AC/5s and lots of heat sinks became the rule of the day once we incorrectly concluded that you could fire a gun as often as you had ammo and heat sinks to handle it.)
The multi-engine idea first came up in our aerospace fighter design but quickly carried over to 'Mechs. It wasn't hard to get a 100-ton 'Mech up to 6/9. 38 tons of engines is beefy, but not as bad as 52.5-ton 400 engine. Today, the Tech Manual rules explicitly ban separate engines. Oh, well. It was fun while it lasted.
Of course, if you asked me now I'd say that the "single" engine could very well represent multiple reactor cores or turbines, it just counts as a single system and the weight goes up along the rating scale regardless of the fluff details.
Mike Miller, Materials Engineer
Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
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ghostrider
10/27/21 08:27 PM
45.51.181.83
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Having multiple engines is a problem because each engine, no matter the rating, comes with 10 free heat sinks. This also means you can't knock out a mech with simply taking down the engine, like you can in a single engine unit.
But the game does not consider mass when dealing with engines. The 400 engine takes up as much space in a torso as the 10 rated engine. With the hidden sinks, the 10 rated engine hides only so many sinks in the engine itself before having to place crits for them. But they still carry the 10 sinks for no extra weight.
I can see where having an engine in each side torso would work, if they are both the same tonnage, and have a piloting skill roll or penalty if one of them is damaged, due to the massive weight loss.
It also means you need to hit more then 3 engine crits to keep the unit from firing weapons and such.
This also means that a unit such as the Locust will never run hot, even with the double laser load outs.
As most want some idea before they play a game that things aren't confusing like this, I would suggest any playing, should vote to use such a thing as a house rule. Any no vote should stop it entirely.
This WILL alter more then a few mechs, as something like an Awesome would have 20 sinks with the engines and move faster with two engines. 10 sinks for 6 crit slots goes a long way in cooling a unit. Almost as good as using clan double sinks.
I would suggest a few trial scenarios before really allowing a house rule like this.
It would be fun, but easy to get used to, so watch how often you even try it.
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Maurer
10/28/21 01:33 AM
107.185.100.70
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In my opinion, the use of two engines to try equal the power one engine for a reduction in weight starts to step into the land of munchkins. There would have to be some kind of drawback to using tandem engines and not just being bulkier or more expensive.
"Captain! We're completely surrounded on all sides." - Kiff, Futurama
..."Excellent, then we may attack in any direction." - Zapp Brannigan, Futurama
"A fool fights a war on two fronts; only an idiot defends on one." - Fusilier
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Maurer
10/28/21 01:55 AM
107.185.100.70
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Quote:
But the game does not consider mass when dealing with engines. The 400 engine takes up as much space in a torso as the 10 rated engine. With the hidden sinks, the 10 rated engine hides only so many sinks in the engine itself before having to place crits for them. But they still carry the 10 sinks for no extra weight.
When you factor in double heatsinks, I doubt this is too over powering. Double heatsinks are already 2x bulky for clan and 3x bulky for IS. I would say using using 2 tandem engines with double heatsinks (20 free double heatsinks) doesn't leave much room for the average extra weight gained of no additional heatsinks, which is probably around 5-6 tons (give or take) depending on the average design.
If you use something like 2x 160-rated over a 300-rated engine, that's only 12 double heatsinks covered, with 6 double heatsinks requiring 12-18 crit slots, not much room left for endosteel or ferro-fiberous armor if you plan to mount large weapons.
I would say tandem engines would have to only be available with single heatsinks, but then the design would be more prone to heat spikes and crit-prone to loosing heatsinks faster.
"Captain! We're completely surrounded on all sides." - Kiff, Futurama
..."Excellent, then we may attack in any direction." - Zapp Brannigan, Futurama
"A fool fights a war on two fronts; only an idiot defends on one." - Fusilier
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Qoonpooka
10/28/21 10:28 AM
40.132.250.62
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Quote:
Of course, if you asked me now I'd say that the "single" engine could very well represent multiple reactor cores or turbines, it just counts as a single system and the weight goes up along the rating scale regardless of the fluff details.
This is a great point, actually. For all we know, a Vlar 400 is just a quad-core setup with four 100-rated cores running with a bunch of power conditioning.
Here's what I've settled on as a second draft of my own houserule, settling on splitting the tandem-engine idea into two camps: the necessity camp and the high-engineering camp.
Necessity Tandem Engines:
Because fusion engines and battlemechs are both scarce in the deep periphery, it is common enough that a damaged 'mech will have its engine slagged but still be worth more as a whole 'mech than as parts to keep other 'mechs running.
Battlemech fusion engines may be replaced with two engines of the same rating whose sum equals the rating of the stock engine. There is no weight savings gained, and the repair is done at +5TN and takes three times as long. The 'mech's maintenance cost is recalculated as if the 'mech were higher mass (Stock mass + mass of engines being added, rounded UP to the nearest multiple of 5). The 'mech gains two 'engine' criticals in each side torso.
TL;DR - It's not a design feature, it's a scrapper's hackjob of a field repair. No real benefits aside from being able to use a wider array of parts to keep your 'mechs running.
High Engineering Tandem Engines:
With some extensive engineering work, a Battlemech may be modified with a tandem engine setup to trade bulk for useful load.
- The total mass of the tandem engine setup is the GREATER of: the sum of the two smaller engine's masses, OR the mass of the stock engine * 0.66 (This overrides the bullshit that you get at the 300-400 engine rating range.)
- Tandem engine setups require three 'engine' criticals in each side torso to represent the extra bulk of this layout.
- A battlemech with tandem engines is considered destroyed if it sustains three engine critical hits in a single torso OR a total of four engine criticals across two locations. (Electrical systems are inherently susceptible to frequency/voltage disruptions and will trip if performance deviates too strongly.)
- Engine critical hits in the Center Torso induce +10 heat, instead of the usual +5, to reflect the proximity of the shared shielding.
- The second engine provides no additional 'free' heat sink slots.
- Engine repairs now take twice as long; the 'mech can no longer be repaired with its stock engine unless the reengineering is reversed first. (I already houserule that ANY deviation from stock designs requires an expensive, lengthy engineering phase with possibility for cost overruns and negative quirks to slip into the design.)
TL;DR - It's a poor man's XL engine. Slightly better in some 'mechs than a light engine, masswise. Virtually as vulnerable as an IS XL, with some outright NASTY surprises, including the possibility of sucking on +25 heat per round (two CT engine hits, 1 side torso engine hit).
I see this as a Solaris thing, the occasional one-off, or a go-to option for periphery states with access to lower-rated engines than their 'mech inventory otherwise requires.
To me the downsides feel sufficiently nasty, and the scheme as a whole feels like:
Tandem Engine:XL Engine::Electronic Warfare Equipment:Guardian ECM
Updated topic to reflect that this is a design houserules noodle thread. If that means it needs to move, I'm all for it.
Edited by Qoonpooka (10/28/21 10:30 AM)
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ghostrider
10/28/21 01:29 PM
45.51.181.83
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One thing to fix in the stats is you say 3 times the repair time, then later drop it to 2.
I would suggest having to increase the gyro in said unit, to be a ton heavier. So a 5 ton gyro would be possible. Expensive as hell, and even harder to find.
To my knowledge, there is nothing saying you have to use all 10 free sinks. Using just the hidden sinks, if doubled, would allowed greater heat dissipation in the unit, then a single sink engine would. Running with just 6 doubles does this.
Granted, there is nothing saying you can drop some of those sinks, but for normal units, this isn't a good thing.
A big down side to tandem engines is the critical space used. For some mechs, this will mean removing things like endo steel, ferrous armor, or even weapons.
I would also suggest a penalty for engine, gyro, and even movement crits repairs. Trying to sync the engines to keep power flow even, being the excuse for it.
Again, play with it before introducing it to a group, and make sure they all want to try it. This is something that will definitely change how the game goes. Crits to the center torso, without other items in there, will all go to the gyro, so the game may well be over with quicker.
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Qoonpooka
10/28/21 01:54 PM
40.132.250.62
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Quote:
One thing to fix in the stats is you say 3 times the repair time, then later drop it to 2.
Intentional. The "Necessity" model reflects the lack of engineering involved. You've taken a perfectly acceptable engine compartment and turned it into a spaghetti monster. The second version reflects someone actually taking the time to do some engineering and work it out so the penalty isn't as bad.
Quote:
To my knowledge, there is nothing saying you have to use all 10 free sinks. Using just the hidden sinks, if doubled, would allowed greater heat dissipation in the unit, then a single sink engine would. Running with just 6 doubles does this.
Granted, there is nothing saying you can drop some of those sinks, but for normal units, this isn't a good thing.
Correct. The "free heat sink slots" simply lets you have heat sinks without needing criticals taken up for them. We don't want someone able to shove 20, uncrittable DHS on the thing.
Quote:
A big down side to tandem engines is the critical space used. For some mechs, this will mean removing things like endo steel, ferrous armor, or even weapons.
Correct, though plenty of 'mechs run XL + Endo + FF just fine.
Quote:
I would also suggest a penalty for engine, gyro, and even movement crits repairs. Trying to sync the engines to keep power flow even, being the excuse for it.
I'll mull on this one. I hear what you're saying: the whole power system has to change if you screw with the supply like this, but I feel like having heinous penalties stacked on the engine crits themselves is enough punishment.
Quote:
Again, play with it before introducing it to a group, and make sure they all want to try it. This is something that will definitely change how the game goes. Crits to the center torso, without other items in there, will all go to the gyro, so the game may well be over with quicker.
Yeah the engine criticals in the CT remain in both instances, so the gyro won't be any quicker to die, but it seems likely that 'mechs with tandem engines will get cored out less frequently. They don't immediately drop on torso loss the way XLs do, but once the side torso is gone, if you so much as LOOK at a CT engine critical the wrong way, it counts as an engine kill.
Edited by Qoonpooka (10/28/21 01:54 PM)
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ghostrider
10/29/21 11:38 AM
45.51.181.83
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Ok. I thought each engine would go into a side torso, so the weight was distributed evenly. So basically, you are adding an engine into one side torso. Good to know.
The idea of the penalties for the engine and gyro some from a simple fact. Having two engines means losing one slows you down and adds 10 heat. It does not knock the unit out of the game, as it does with a single engine. I do understand not wanting to make repairs or even just installing the second engine extremely more difficult. If one of the engines is in the center torso, the gyro will have to work that much harder to counter the other engine weight. I know mechs are supposed to have things to help balance them, but it is odd that it isn't really discussed.
A 35 ton panther carries a 7 ton PPC on one arm, yet there is nothing to really counter balance it in the other. Only weight would do so, and there is nothing in the construction rules to support this. The Wardog (I believe) mech is the only mech I have seen that suggests this because of the Gauss rifle and more armor in one arm suggests gyro clutching to deal with it. The TRO 3055 has this information on page 74, but the wiki does not. I don't know if it was pulled out of the official mech design or just not put into the wiki.
The sync problem wasn't in combat so much as repairs. Much like trying to get a dual engine vehicle to put out the same power at the same moment. Though I guess you can say a power regulator in the system deals with it. It is not a physical connection of engine to driving mechanisms. It is just 'electricity', or how even they describe the power put out, in cables that power the myomers. Could require a regulator for the system.
Edited by ghostrider (10/29/21 11:42 AM)
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Qoonpooka
10/29/21 12:14 PM
40.132.250.62
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Quote:
Ok. I thought each engine would go into a side torso, so the weight was distributed evenly. So basically, you are adding an engine into one side torso. Good to know.
Both torsos. Basically each engine is straddling a side/center torso joint. This is also why the repairs become more difficult, it's not just tacking another engine onto the existing structure, you're completely rebuilding the whole engine compartment to put in two somewhat smaller units where the single larger unit used to be. You also end up needing to carve out space in both side torsos to do this.
Quote:
The idea of the penalties for the engine and gyro some from a simple fact. Having two engines means losing one slows you down and adds 10 heat. It does not knock the unit out of the game, as it does with a single engine. I do understand not wanting to make repairs or even just installing the second engine extremely more difficult. If one of the engines is in the center torso, the gyro will have to work that much harder to counter the other engine weight. I know mechs are supposed to have things to help balance them, but it is odd that it isn't really discussed.
Because of how damage, as a phenomenon, works just because something's destroyed doesn't mean it's not still there. Until the section itself is blown clear off, all that mass is still there, which is why you don't make PSRs every time you take a critical - the 'mechs balance isn't significantly disrupted, but whatever systems that crit represented were smashed. So to me it doesn't seem to make sense to induce balance issues just because the crit is an engine. You're right that the game rules don't do a good job of this even where it's warranted, blow off the Panther's right arm and it still stands up just fine, after all.
Quote:
The sync problem wasn't in combat so much as repairs. Much like trying to get a dual engine vehicle to put out the same power at the same moment. Though I guess you can say a power regulator in the system deals with it. It is not a physical connection of engine to driving mechanisms. It is just 'electricity', or how even they describe the power put out, in cables that power the myomers. Could require a regulator for the system.
It's precisely because it's an electrical connection that sync matters and a significant disruption completely knocks the unit out. A mechanical linkage that loses half its power, but still has power, can keep on chugging at a slower speed as you describe (as long as whatever power remains is able to break inertia and overcome friction losses).
But electrical systems (and this is where my background in energy policy kicks in) are EXTREMELY sensitive to disruption. Electrical power that deviates from specification is VERY damaging to electronics (this is why surge protectors are important). Too much power, not enough load = melting cable/fires. Not enough power, too much load = rolling brownouts or complete loss of system performance.
For this reason, electrical systems have safeguards built in (there's all kinds of schemes but modern versions are called 'circuit breakers') that will shut the entire system down if supplied power deviates too far from operating specifications - this is known as 'tripping.'
This is why a single transmission line in Ohio touching a single tree branch for half a second was able to cause the entire New England electrical system to crash at once: the safety system for that line did NOT trip, and so it caused a major voltage and frequency drop to spread throughout the network. Once it was loose, every time another generator's safety breaker tripped, the size of the problem from the line in Ohio compared to the "size" of the remaining grid got worse and worse and worse.
I suppose it might be possible to restart the 'mech with the remaining engine and try to run on half power, but generally speaking electrical devices - and especially electrical mechanisms - don't handle low power very well: they're designed to present a certain degree of load and when you undersupply the voltage, the frequency drops which can result in damage to systems that are tuned to operate on certain frequencies - it's like messing with the timing of your car's injection system. We don't know enough about myomer to know if it can handle lower voltage like an incandescent lightbulb can (the lightbulb is unique in this way), but I'd bet the rest of the 'mechs systems, especially energy weapons, are all-or-nothing affairs, they won't take half-power. So maybe half movement and all energy weapons are offline? Given that you're sporting 3 engine crits at that point, it's not like you want to fire them anyway...
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Reiter
10/29/21 12:35 PM
107.185.100.70
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Extra weight, same speed? Its too perfect, Suggest adding in -1 movement penalty for light and medium mechs exceeding 5/8, it becomes too good for a slap job.
Alternative is more heat generated when moving, as its 2x engines which is more power required to move a bigger mass than the engines rated moving by themselves; but you only have 1/2 the heat sinks to cover two engines.
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ghostrider
10/29/21 07:13 PM
45.51.181.83
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I am confused now. Is each engine in each side torso? Or is there one in the center torso?
I ask because I was talking about having the center torso being basically empty except for the Gyro, unless you add in things like sinks and weapons.
Or are you making it so each engine has part of their mass in the center torso?
The perceived idea in this concept is that you use two smaller engines to make or exceed the speed for the unit. So the 300 vlar for a marauder, for instance, could be replaced with a pair of 150 engines. In some cases the half rated engines will be less weight then half the tonnage of the larger engines. I believe there should be a few more penalties in it, to balance this out, as the 10 free sinks that come with each engine can really tilt things. For some engines, like those under 10 tons, it becomes a mega bonus.
The loss of an engine wasn't meant as a weight issue, but the fact that a normal unit losing their engine is out of the game. I was thinking their should be something to balance this fact out. With two engines, you still move, fire and what not as well as vent heat when one is shut down.
Which brings up the question of how do you handle a heat roll for shut down? Does each engine roll separately, or one roll for both?
Mechanically, two engines that aren't synced right will cause issues with power to each wheel. This will throw off a vehicle as one side tries to move faster then the other. Not sure about a real tandem engine set up, but I believe it puts a huge stress on the drive shaft between the two engines. It can cause it to shatter, and fling debris through out the entire area, potentially destroying both engines.
One example can be the MASC/Supercharger set up. More speed for little weight, though they do have issues.
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Maurer
10/30/21 06:47 AM
107.185.100.70
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Quote:
A 35 ton panther carries a 7 ton PPC on one arm, yet there is nothing to really counter balance it in the other.
Can you cite an example of how a battlemech carrying extra weight on one side requires it to have to have a counter balance on the other? The only examples I can think of are the Javelin and War Dog, which could be attributed simply to gyros not calibrated very well for the specific designs. Other counterbalance issues that I can think of are 20+ damage received in a single turn and limbs blown off, but those both only require 1 piloting roll and don't require the mech to make another piloting roll the following turn. Even gyro crits (memory is a little hazy) require a piloting roll for that turn and make any additional piloting roll more difficult, but don't require a mech to make the roll every turn, unless it needs to.
Heck, in real life, I can probably carry something 20-25 lbs in one hand and not feel like I would tip over or need a counter balance. I remember having to carry the same amount of text books (for the youngsters, those are like tablets, only made out of trees) in high school and I always felt like I was gonna fall over because it was on my back - What? I wasn't as physically fit then as I am now, plus I have a gut in front to counter balance a load on my back now.
I honestly believe mech gyros are similar to Fly-By-Wire, where the pilot inputs controls, but the computer calculates the necessary systems to achieve the specific movement and can't adjust itself quickly enough during detrimental incidents, unless the pilot intervenes..
"Captain! We're completely surrounded on all sides." - Kiff, Futurama
..."Excellent, then we may attack in any direction." - Zapp Brannigan, Futurama
"A fool fights a war on two fronts; only an idiot defends on one." - Fusilier
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ghostrider
10/30/21 12:06 PM
45.51.181.83
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Nothing in the rule books deal with balance of units. The jump jet situation shows this by allowing you to put all the jets in on location, IE the left leg or a side torso.
The novels are the only thing besides the War Dog and Javelin that suggest this is an issue.
It is possible the Gyro resets after a few seconds to account for the loss.
Starting out with a load on one side of the body is only a small issue. it makes things like a run harder, as the weight causes you to have to compensate for it. On a mech, the gyro should be set for it. Losing it would be even more of a problem, as the unit would have been built to handle the mismatched load.
This seems to be one of those things that to keep it simple, they just went with a single roll. I can agree with it.
I was not trying to say a piloting roll should be used every single turn with the gyro issue on a tandem engine set up. Just once after repairs and such. Get it recalibrated for the odd weight on the sides, especially if only one of the engines are in a torso.
But the gyro reset concept would deal with that.
Much like a pilot starting up a mech laying down, the gyros would be 'programmed' for that position, so standing would cause a piloting roll. That isn't in the rules, but something that should be noted.
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VurGhent
04/28/22 10:07 PM
76.14.216.124
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A bit late to this conversation, my apologies.
Many years ago (okay, a couple decades), I ran across a magazine with a Q&A section that included the question as to why there are not multi-engine mechs (and other vehicles).
The reply given was a technical one and not just a gameplay answer. Therefore, by reading the reasons why it is not done, the rules were presented as to how it would be done.
As I recall (can't find the magazine anymore), it was something to the effect of ...
"Due to the interference caused by multiple engines operating in close proximity, it was found that additional shielding, cooling and control systems needed to be added to each engine, resulting in a significant increase in weight, bulk and expense." (Similar, but not likely the exact wording.)
It went on to explain that each engine would require additional shielding equal to half the weight and spaces of said engine. Think expense was at least 50% if not 100% as well.
Again, please don't quote me on this, I am pretty sure it is close, but it has been a few decades and while I bought that magazine for that one Q&A, I have not been able to find it for a while.
It is possible (and fun) to make functional mechs within these rules, but torso hits can really ruin your day.
When designing my own 'mechs, I also ensured I maintained that each fusion engine came with 10 heat sinks that needed to be placed and also doubled the heat generated by movement (not including jump jets)
By the way, if anyone has or comes across this magazine (sadly, forgot which one) and finds this Q&A, would you please send me the name and issue (or just a picture of this answer).
"I don't know how much value I have in this universe, but I do know that I've made a few people happier than they would have been without me, and as long as I know that, I'm as rich as I ever need to be." Robin Williams
Edited by VurGhent (04/28/22 10:21 PM)
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Karagin
04/28/22 10:29 PM
70.118.172.64
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That sounds like StarDate or StarDrive magazine. I recall that same answer given and folks didn't buy into it then and still don't but like a lot of things not thought of or dismissed as not needed in the game.
Karagin
Given time and plenty of paper, a philosopher can prove anything.
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ghostrider
04/29/22 10:32 AM
45.51.181.83
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The game reason for not allowing multiple fusion engines in a mech boils down to weight. A single 10 rated engine, that weighs a whole .5 tons, might take up 6 crits, but given the fact it comes with 10 sinks free, means for .75 tons, you gain the 10 tons of sinks for free.
With the advent of double heat sinks, this becomes even more of an issue. Granted the engine doesn't hold that many being a 10 rated engine, but there are a few larger ones that are light weight, and can hold more.
This is also why vehicles can't multiple fusion engines.
Having a pair of engines half the size of what is needed to move the vehicle at speed might well just add up to the normal engine, the extra sinks goes a long way to making it too over powered.
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