Oddly rated engines?

[evilauthor]

You know how the deal goes. To determine engine rating, we multiply mech tonnage by walking MP. To get running MP, multiply walk MP by 1.5 round up. Thus we get this progression:

Walk/Run
1/2
2/3
3/5
4/6
5/8
6/9

And so on. But wait! Where's the mechs with a max run MP of 4? Or 7? What if I want a mech faster than say... 4/6, but don't want to or can't pay the tonnage for an engine that does 5/8? Well, that's where this idea comes from.

Take a desired running MP. Let's say 7. Now let's figure out an engine rating for it.

Premises:
tonnage x walk = engine rating
walk x 1.5 = run

Therefore:
walk = run / 1.5
tonnage x run /1.5 = engine rating

Test:
I want a 70 ton mech with a max run of 7.
7 run / 1.5 = 4.666667 walk
70 tons x 4.666667 walk = 326.6666667

Okay, since a mech can't walk fractions of a hex in game, it's walk MP is rounded down to 4 since 5 would require running.

And since fusion engines are only rated in increments of 5 and 325 would be too weak, round up to 330.

Result:
A 70 ton mech that moves 4/7 would use a 330 rated engine to do so.

So the more detailed rules would be:
1) Decide desired running MP.
2) Get Base Walk MP by dividing Run MP by 1.5. Round result down to nearest whole number to get Final Walk MP.
3) Get Engine rating by multiplying Base Walk MP by mech tonnage. Round up result to nearest increment of 5.

Addendum:
70 ton mech with 4/6: 300 rated engine 19 tons
70 ton mech with 4/7: 330 rated engine 24.5 tons
70 ton mech with 5/8: 350 rated engine 29.5 tons
Hmm... so would oddly rated engines be worth it?

[tomaddamz]

Wouldn't a 70 ton Mech use a 280 rated engine to walk at 4?

70 * 4 = 280

[majesticmoose]

Wouldn't a 70 ton Mech use a 280 rated engine to walk at 4?

70 * 4 = 280

sigh...

I liek the idea, but does it lead to strange BV calculations?  OF the top of my head, no, but it could create even stranger optimization issues than we already have...

I like it.

[evilauthor]

Wouldn't a 70 ton Mech use a 280 rated engine to walk at 4?

70 * 4 = 280

The idea is to get a slightly better running speed without paying the full tonnage for a full walk increment.

[nckestrel]

The idea is to get a slightly better running speed without paying the full tonnage for a full walk increment.

yes, but 4/6 isn't a slightly better running speed. it's standard, and that has been a 280 engine (70 tons * 4 walk = 280 engine).  i think you just have a typo in the 70 tons 4/6 300, should be 70 tons 4/6 280 (and the tonnage for the 280).

[evilauthor]

yes, but 4/6 isn't a slightly better running speed. it's standard, and that has been a 280 engine (70 tons * 4 walk = 280 engine).  i think you just have a typo in the 70 tons 4/6 300, should be 70 tons 4/6 280 (and the tonnage for the 280).

No, the idea was to get a slightly better running speed of *7* and then working backwards to see what kind of engine rating you need to achieve that running speed without going all the way up to 5/8. Did you READ my entire post or did you just skip to the calcs?

Because of the way engine ratings are calculated, some max run speeds are NEVER used, and I thought being able to have them might be useful. For some mech designs, you might want to be able to squeeze out just that extra hex of movement that an oddly rated engine can give.

[tomaddamz]

The idea is to get a slightly better running speed without paying the full tonnage for a full walk increment.

I was trying to point out a typo with the 70 tonner using a 300 rated engine at 4/6...it was late and I didn't want to bang out anything impertinent.  Since then I gotten some sleep, I feel I can make a more measured response.  Oh, and for completeness sake...

70 tons 4/6  280  16 tons engine SFE     2 ton gyro 3 ton gyro STD
70 tons 4/7  330  24.5 tons engine SFE  3 ton gyro 4 ton gyro STD
70 tons 5/8  350  29.5 tons enging SFE  3 ton gyro 4 ton gyro STD

I really don't mind the idea of "enhanced running" with suitably large fusion engines, at lower tonnages this may work out very well.  Also I am a big fan of using the engine you have, not necessarily the one everyone uses for that movement curve.  I personally like the idea.

[majesticmoose]

I was trying to point out a typo with the 70 tonner using a 300 rated engine at 4/6...it was late and I didn't want to bang out anything impertinent.  Since then I gotten some sleep, I feel I can make a more measured response.  Oh, and for completeness sake...

70 tons 4/6  280  16 tons engine SFE  2 ton gyro STD
70 tons 4/7  330  24.5 tons engine SFE  3 ton gyro STD
70 tons 5/8  350  29.5 tons enging SFE  3 tons gyro STD

I really don't mind the idea of "enhanced running" with suitably large fusion engines, at lower tonnages this may work out very well.  Also I am a big fan of using the engine you have, not necessarily the one everyone uses for that movement curve.  I personally like the idea.

wouldn't those last 2 be 4 ton gyros?

The idea does make certain weights (45,55,65) more flexible, because you could avoid some of those odd engine ratings that cause all sorts of inefficiency problems.

[tomaddamz]

You are Right Majesticmoose...I'll fix that in just a minute.

There, I fix it too

[evilauthor]

Wow. Badly thought out calcs all around...  :D

[tomaddamz]

I know, time for a nap...

[majesticmoose]

You are Majesticmoose...I'll fix that in just a minute.

?????

[Mattlov]

I like the idea.  Construction would be a nightmare, but pranking the "new guy" with a SMALLER engine could be funny, too.

[majesticmoose]

I know, time for a nap...

Definitely nap time.  but I'm working... hmmmmm..... George Costanza is my hero, and I do have a big desk...

[mathesont]

Like the idea a lot.  These odd run speed mechs would not be something you wanted to add MASC to but improved jump jets would rock - 4/7/7.

[majesticmoose]

Yeah, these can actually make iJJ more versatile, because you wouldn't be wasting engine space on extra engine.

[evilauthor]

I'll admit that I did have iJJ in mind when I came up with this idea.

[majesticmoose]

I'll admit that I did have iJJ in mind when I came up with this idea.

Cheater.   ;)

[TJHairball]

Another reason for wanting to up engine rating is to bury additional heat sinks in the engine. 240 to 250, 320 to 325 - I would rather be able to just plug in whatever size engine I want into a BattleMech and then calculate the speed from it. Calculating the running speed separately from the walking speed just plain makes sense.

That said, 4/7/7 IJJ machines are kinda cheesy.

[evilauthor]

Another reason for wanting to up engine rating is to bury additional heat sinks in the engine. 240 to 250, 320 to 325 - I would rather be able to just plug in whatever size engine I want into a BattleMech and then calculate the speed from it. Calculating the running speed separately from the walking speed just plain makes sense.

That said, 4/7/7 IJJ machines are kinda cheesy.

Technically speaking, while it may make more sense to calculate speed from rating, in practice, people have a speed they want their machines to go and then calculate how much engine they need for it. In this case, you want a set running speed that isn't normally used because you can't multiply 1.5 with an integer to get it. You want just enough engine to reach the desired running speed without paying the full tonnage for an incremental bump in walking speed.

Now in the "real" world, mounting a 325 rated engine on your 100 ton assault mech might let you hide an extra sink and make you walk a tiny bit faster. In the BT game world however, that extra 25 rating only lets you hide the sink, but doesn't let you walk/run any faster, making the extra tonnage mostly worthless.

[Frabby]

This may be heresy to some, but I think the idea may actually be compatible with current construction rules (i.e. legal), depending on the exact wording of TechManual (which I don't have).

Does it explicitly say anywhere that you may not install an oversized engine for your walking MPs?
If no, does it explicitly say walking MPs have to be rounded before calculating running MPs from them?

[TJHairball]

Technically speaking, while it may make more sense to calculate speed from rating, in practice, people have a speed they want their machines to go and then calculate how much engine they need for it. In this case, you want a set running speed that isn't normally used because you can't multiply 1.5 with an integer to get it. You want just enough engine to reach the desired running speed without paying the full tonnage for an incremental bump in walking speed.

Now in the "real" world, mounting a 325 rated engine on your 100 ton assault mech might let you hide an extra sink and make you walk a tiny bit faster. In the BT game world however, that extra 25 rating only lets you hide the sink, but doesn't let you walk/run any faster, making the extra tonnage mostly worthless.

Going 140-150, 240-250,270-275, 320-325 can be worth the trade of 1 ton for 3 critical slots; 195-200 is 0.5 tons for 3 slots, which a heavily armed 65 ton "pocket assault" might want. 90-100 and 220-225 is no extra tonnage - just a little extra c-bill cost for saving slots on your 4/6 55 tonner, or your 3/5 Urbie upgrade. (Yeah, I ran into this issue a long time ago.)

I wouldn't go 300-325, and 340-350 would only occasionally be worth it, but there are cases where ticking the engine rating up is worth it in game terms.

This may be heresy to some, but I think the idea may actually be compatible with current construction rules (i.e. legal), depending on the exact wording of TechManual (which I don't have).

Does it explicitly say anywhere that you may not install an oversized engine for your walking MPs?
If no, does it explicitly say walking MPs have to be rounded before calculating running MPs from them?

In the BT game world, I am - technically - not allowed to do so in the base construction rules. You select a walking MP and then are told explicitly to compute engine rating from MP and tonnage. The rules don't explicitly prohibit a "bad" engine rating, but they do explicitly tell you how to assign engine ratings.

(I am allowed to do a retrofit of a non-standard engine as a "FrankenMech" in StratOps.  #P This has the effect of de-Omnifying an Omni. However, it does defines the Walk MP of a FrankenMech as the rounded-down value.)

[majesticmoose]

From TM page 48:

To compute the Engine Rating, the designer simply multiplies
the BattleMech’s tonnage by its desired Walking MP.

It never says that your walking MP must be an integer.  It is implied, since fractional MP as essentially wasted MP for the purposes moving (you can't get anywhere on .3 mp).

but from a very strict perspective, it probably permisible, though I'm gonna say completely against the RAW and the Intent (what ever that may mean).

so for 7 run, you would require 4.66666666 walking MP.

I will say that running MP is alwasy rounded up, so in essence you could become 4/7 by having as little as 4.01walking MP.  so I would say the rules should include normal rounding at that point, but then you screw up the walk/run calcs of other units.

like ripples in a pond...

[evilauthor]

I will say that running MP is alwasy rounded up,

I'm not so sure run MP is ALWAYS rounded up. Let's take a look at a canonical rounding up.

Walk MP: 7
Run MP before rounding: 10.5
Run MP after rounding: 11

Now IIRC from grade school math, when rounding up and down to the nearest integer, anything under 0.5 rounds down, anything equal to or greater than 0.5 rounds up.

So basically put, if I want a mech that runs 7 max, I don't need to pick integer 7, I just need a max run of 6.5, which translates into a walk MP of 4.3333333333. On a 70 ton mech, this translates into a 303.3333 rated engine, or more practically 305 rating.

Hmm... can any canon walk/tonnage combo actually result in a 305 rating? 305 / 5 = 61. IIRC, 61 is a prime number. So no, no canon mech can use this. MAYBE a vehicle can, but I don't feel like calculating that.

[tomaddamz]

Hmm... can any canon walk/tonnage combo actually result in a 305 rating? 305 / 5 = 61. IIRC, 61 is a prime number. So no, no canon mech can use this. MAYBE a vehicle can, but I don't feel like calculating that.

All vehicles can be built to single ton increments.

[majesticmoose]

I'm not so sure run MP is ALWAYS rounded up. Let's take a look at a canonical rounding up.

Walk MP: 7
Run MP before rounding: 10.5
Run MP after rounding: 11

Now IIRC from grade school math, when rounding up and down to the nearest integer, anything under 0.5 rounds down, anything equal to or greater than 0.5 rounds up.

So basically put, if I want a mech that runs 7 max, I don't need to pick integer 7, I just need a max run of 6.5, which translates into a walk MP of 4.3333333333. On a 70 ton mech, this translates into a 303.3333 rated engine, or more practically 305 rating.

Hmm... can any canon walk/tonnage combo actually result in a 305 rating? 305 / 5 = 61. IIRC, 61 is a prime number. So no, no canon mech can use this. MAYBE a vehicle can, but I don't feel like calculating that.

Ahem.  Grade school math aside... ::) I was refering to

Page 48 of the Tech manual
...The ’Mech’s
Running MP is also calculated at this time by multiplying its Walking
MP by 1.5 and rounding up to the nearest whole number.
...

I know you didn't mean to imply that I was a short bus rider, but I was actually refering to the RAW.

 :P

[evilauthor]

Ahem.  Grade school math aside... ::) I was refering to
I know you didn't mean to imply that I was a short bus rider, but I was actually refering to the RAW.

 :P

Ah, sorry. My apologies.

Wait a sec, so that means if you calculate an engine rating from an even walk MP as normal and then simply add 5 to the rating, you can get ONE WHOLE EXTRA run MP? Cool!  :D ;)

Hmm... to make a 5/8 get to 5/9, I need a base run greater than 8 (base run for 5 is 7.5). 8/1.5 = 5.333333. On a 50 ton mech, that would be a base rating of 266.666667, or 270. A 270 rated engine on a 50 ton mech gets an actual walking speed of 5.4, and an actual run speed of 8.1 which according to rules rounds up to 9.

So for a 50 tonner:
5/8 move = 250 rated engine = 12.5 tons
5/9 move = 270 rated engine = 14.5 tons
6/9 move = 300 rated engine = 19 tons

That one extra run MP only costs you 2 tons. An exta walk MP costs 4.5 tons more than THAT. So a 5/9 certainly looks like it's worth the cost.

Of course, all this is rules lawyering. Realistically, a 50 ton mech with a 270 rated engine barely moves faster than one with a 250 rated engine. And of course the original rules never envisioned anyone getting a run MP that was x.0 or x.5. If you have to get the run up to a more realistic 8.5, then you wind up needing a 285 rated engine which is 16.5 tons. That's 4 tons more than the 250 and 2.5 tons short of the 300. That may make it more worthwhile to simply take the full 6 walk instead.

[TJHairball]

All vehicles can be built to single ton increments.

Also, the suspension factors can do it for you even with vees that land on the nice round 5 ton increments. A 65 ton wheeled vee going 5/8 needs (325-20) a 305 rating. ;)

[majesticmoose]

Ah, sorry. My apologies.

It's ok.  Yeah.... Given how the rules are worded, even though it isn't expressley forbidden, I would say that for "legal" odd engine weights, that you would break from the formula, and find the run MP first, calculate the walk MP (with decimal) find the appropriate engine weaight, then drop the decimal on the walk.  Just to be fair.

Otherwise, yeah, juice that engine by 5 and get 1 bonus run MP.

[evilauthor]

Time for some rules abuse...

100 ton mech
Internal Structure, 10 tons
3/6 move = 335 rated standard fusion engine = 25.5 tons (19.5 for LFE, 13 for XL).
Gyro (no fractional accounting) 4 tons
Standard Cockpit 3 tons
Standard Armor 19 tons
Payload:
 SFE: 38.5 tons
 LFE: 44.5 tons
 XLE: 51 tons

Is that 1 extra run MP worthwhile?

Note, the above assume you only need to get just above 5 MP to get 6. If you need a minimum 5.5 MP to get 6, the required engine rating jumps to 370 (36.5 / 27.5 / 18.5 tons for SFE/LFE/XL)

[Onisuzume]

Hm... already started something like this on my own some months ago using OpenCalc...
Thanks for mentioning the round-up rule, btw, might make things easier.
Also included in said ods file are speeds in km/h, engine weight (various engine types) and gyro weight (standard only).

My method of finding out the run MPs is different, though.
Find out walk speed (in km/h), find the increase in km/h per 5 engine ratings for the weight class, multiple result for run speed in km/h, if divisible by 10.8, speed goes up by 1. No rounding up/down in my calculations.

Mostly started it to find out if putting a more common-rated engine into a different 'Mech would make much of a difference (engine/gyro weight, followed by speed). The former is mostly useful for light 'mechs. And, to be honest, I never thought of iJJs before. o.0

[Rhyshaelkan]

Personally I like the idea. However the whole thread falls apart if your opponent does not allow for custom 'mechs.

Also, I like the rounding rules as they stand :P That way I get that rounding up factor from odd walking speed.

My favorite chassis is a 60 tonner with 5/8 movement. At (8 / 1.5) * 60 that would leave me with a 320 engine instead of 300. For this 'mech with 5/8/7(as previously stated the holy grail of 7J is what we seem to be after) we have 9.5(assuming XL) + 14 = 23.5 for motive functions.

Now by your calculations trying to achieve 7J we have.
7 / 1.5 = 280.  That is 8 +14 = 22 for a 4/7/7 60 tonner.

Now, before you all go crazy. I know a 55 tonner 4/7/7 would be light-years better for podspace. However my original desire for my 5/8 60 tonner is to have a basic all duty chassis. After trying to squeeze this way and that. I could never quite get two Arrow IV systems onto a 55 ton 5/8 machine. Without sacrificing other things like armor. So I have a stock 60 ton 5/8 omni-chassis with 201 armor and no built in heat sinks. Giving me 31 tons and 29 crits. I like the versatility there.

The economist in me likes commonality in parts. One chassis one engine one armor one inner structure. So that I can keep my men on the line.

I like the rules option, truly. However I can see where it would be abused. Not that I am an angel when it comes to munchy min/maxing.