Sunday, December 30, 2018

Twilight: 2000 and the Art of Motorcycle Maintenance

Vehicle maintenance and breakdowns are an important part of the post-Twilight War setting, but there's not really a simple summary of the rules for GMs to make it easy to manage this in actual play without getting bogged down.

I've therefore decided to provide an example of the rules in play and look at some of the assumptions needed to solve the "mini-game" and attempt to simplify the mechanics while hopefully retaining the flavour and intent, like the recent "Still Week" simplified travel rules summary post.

For an example Mechanic character, see my pregen "Wheelman" character based on "Monk", one of the iconic characters from the original v1.0 Boxed Set in-character fiction.

Maintenance and Breakdowns 

"In the world of Twilight:2000, a good mechanic is worth his weight in gold, and is indispensable if the PCs have vehicles they want to keep running. A good mechanic, for all his worth, will sometimes be considered a pest by the rest of the group. He will want to spend as much of his time as possible with the vehicles, going over them and conducting minor re- pairs and preventive maintenance." - T2k v2.2, p151
For a mechanic character, Strength (STR) (also used for most combat skills) is the primary attribute for the Mechanic skill with Intelligence (INT) for Scrounging coming in second. Agility (AGL) is useful for more specialised repair tasks. Leaving out Constitution (CON) and Charisma (CHA) as outside of the Mechanic build focus, Education (EDU) is probably the least useful or "dump stat" attribute, so having a dedicated Electronics specialist may be a worthwhile consideration instead. 

The STR based Mechanic skill is a vital resource in T2k, regardless of which version you play. Secondary associated skills include EDU Electronics (for range-finders etc), AGL Gunsmith (for small arms <20mm, fabricating weapons parts), AGL Ground Vehicle (as a backup or support vehicle driver), INT Scrounging (to find needed parts), and CON Small Watercraft (for boats). AGL Machinist is optional and needed to manufacture vehicle and weapon repair tools.

Looking through the T2k v2.2 core rules, the following skill checks involve using Mechanic:

  • Change fuel type used by vehicle (EASY, p151)
  • Routine maintenance (AUTO, p152)
  • Avoiding an actual breakdown (DIFF, p152)
  • Preventative maintenance (AUTO, p152)
  • Fabricating non-weapons parts (DIFF, machine shop, p153)
  • Repairing a turret (DIFF, 1/2 hour, p153)
  • Repairing an autoloader (DIFF, p153)
  • Repairing a >20mm weapon (DIFF, p153)
  • Repairing an engine (DIFF, p153)
  • Repairing suspension (DIFF, p153)
  • Waterline patch repair (AVG, p153)
  • Permanent waterline repair (DIFF, p153)
  • Repair a rudder/screw (DIFF, average with Swimming, p153)

In addition, if using my "Still Week" based simplified travel rules, rigging extra fuel capacity for a vehicle with a "jerrycan" value of 3 or less is a Mechanic: AVG task and a Mechanic: DIFF task for vehicles with higher "jerrycan" values ie. those where a whole 80L or more spare tank is needed.

The following activities require associated skills:

  • Fabricating weapon parts (DIFF Machinist, p153)
  • Repairing range-finder / gun sight / night vision (DIFF Electronics, p153)
  • Repairing weapons <20mm (DIFF Gunsmith, p153)
  • Scrounging for parts (VAR Scrounging, no specific rules for parts)

As most tasks are DIFF (x 0.5), having an Asset value of 10 only guarantees a 25% chance of success - this is roughly the same as a Veteran character with an Asset of 11. A higher Asset value of 20 (eg. Attr 8 and Skill 12) is needed for a 50% success rate, so aiming for an Asset value of 15+ (Elite NPC level) and at least a 35% chance of success seems a reasonable goal when designing a specialist character. 

Aircraft Mechanic is used for similar checks for helicopters, jets and ultralights etc.

Example: Monk's Motorcycle

The usefulness of motorcycles in the Twilight World cannot be under overemphasised in my opinion: they are cheap, readily available, carry a significant Load, are inexpensive to run (in terms of fuel or days spent distilling fuel they require only a single "Still Day" - see earlier post on simplified travel using "Still Weeks"), and of relevance to this post, are very simple to maintain.

Let's say my example "Wheelman" pregen character Monk (STR Mechanic Asset of 15, Elite) owns a beaten up extra fuel capacity modified motorcycle (56L, 2 "jerrycans"), fueled with enough methanol for two 4 hour periods of travel ie 8 hours. Normally carried strapped to the back of an armoured vehicle such as a LAV-25 as external cargo (156kg) it is used for scouting expeditions or to run from camp into a local friendly town as needed. If not Monk then an Elite NPC Mechanic.

His bike has a base Maintenance 2 and Wear 5 (therefore valued at only $1000), equating to needing 2 hours of maintenance every 8 hour period travelled and a 5 in 10 or 50% chance of a potential breakdown every 8 hour period. The chance of a major breakdown relates to the Wear value, so Monk's bike has a 50% chance of having a serious issue instead of just a minor breakdown.

Spending an extra 2 hours (a full 4 hour period) of preventative maintenance between each 8-hour use reduces the risk of a potential breakdown to 30%, spending 6 hours in between trips reduces the risk to 20% and a full 8 hours (two 4 hour periods) drops this to 10%.

As the group is camped in some woods and avoiding the remaining roads, Monk rides into the nearest friendly town to buy some spare parts, fuel, and likely some food.

Assuming the bike has had 4x the amount of minimal maintenance ie 8 hours (2 periods) before the trip, he has only a 10% chance of a potential breakdown on the outward journey, and if the trip is less than 4 hours on the return leg as well. However, if he then uses the bike with only minimal maintenance of 2 hours before the next trip, he runs the usual 50% risk of a potential breakdown. As a dedicated mechanic, he's not foolish enough to skip the minimal maintenance - that would guarantee a 50% chance of an actual breakdown.

Let's say a potential breakdown occurs on the return trip despite his efforts.

Fortunately for Monk, he did the basic 2-hour maintenance and as he was the last to do maintenance on the bike gets to make a DIFF roll against his own Mechanic Asset (ST 7 + Mechanic 8) of 15 or less on D20.

He sadly rolls a 17 on the D20, so his bike suffers an actual breakdown.

He then rolls a 7 on the D10, a minor breakdown.

This means he may need or may not need parts, but he rolls a 4 on the next D10 so parts are needed.  His third and last D10 roll is a low 2 luckily, so only 2 parts are needed. He's not carrying his tools with him, so this would be a Formidable (FOR, x0.5) task with a modified Asset of 7 to attempt a repair.

He's not feeling lucky so he shoulders his pack and some of the extra food, preparing for the 2 day hike back to camp about 70km away (covered on foot with two 4 hour periods per day) to collect his tools and perhaps a few extra parts, cursing himself for not packing his tools.

Back a few days later with his tools and a few extra parts in hand, he uncovers the bike from where he's hidden it and attempts to repair it. He now rolls against a Mechanic: Difficult check (DIFF, x1.0) and scores a 12 - success! The breakdown adds a "experience point" to the motorcycle's Waear value, but fortunately a full 10 breakdowns or points are needed to increase the bike's Wear value to 6.

Rather than jumping straight back on the bike he then spends a full 4-hour period (2 hours minimal maintenance + 2 hours preventative maintenance). He's already wasted over half the week walking to camp from the bike and then back for what was meant to be a single day round trip (fortunately without any significant or hostile encounters), so the extra time becomes reasonable.

Note: it's probably easier to just roll a D20 and four different coloured D10s up front for a potential breakdown check, skipping the D20 if no minimal maintenance was performed. The D20 for the repair roll could be rolled at the same time if the correct tools and available parts are carried.

T2k v2.2 Rules Analysis

As the above example shows, breakdowns are a real potential risk, particularly with older / more worn vehicles, even when the party has an Elite level Mechanic Asset like Monk available. A good mechanic really is worth their weight in gold in the Twilight World. A 4-hour period or two of minimal maintenance over a week or two is easy enough given the slow "stuttering" travel of most groups relying on distilling their own fuel but at a significant risk of breakdown. Only a foolish group would forgo this very basic precaution, especially if they have high Wear value vehicles considered essential such as a "still truck" or their main APC / light combat vehicle eg. a LAV-25 or similar.

Preventative maintenance becomes critical for essential vehicles with high Wear value - a HumVee or UAZ has a similar minimal maintenance requirement to a motorcycle sure, and most trucks only require a 4-hour period to keep in shape, but a LAV-25 or a M113 APC requires 6 hours of minimal maintenance. This is a real investment and means three full 4 hour periods are required between each 8-hour travel period to reduce the chance of a potential breakdown by 2, so a vehicle with a Wear value of 4 or more still has a 20% or greater chance of risking an actual breakdown.

Tools are essential. Although carrying the combination of hand tools and wheeled vehicle tools adds 15kg to the load on a motorcycle, not carrying them has a significant negative impact. A full set of tools for other vehicles seems a must, and while weight may be a minimal consideration, the combined cost of a full complement for a tracked vehicle (hand, tracked vehicle, small arms, heavy ordnance, electronics) is significant at around $3000.

Parts play a vital role. Unfortunately, there's not a lot of details on vehicle parts as a resource other than the rules to fabricate them on p153 using a machine shop. Even the Scrounging rules are vague about parts, requiring a GM ruling to assign a Difficulty level. This is perhaps a design flaw as for beginning players on the run a machine shop is not only prohibitively expensive ($75,000) and inconvenient, requiring a 60kw generator ($8000, 40L fuel per 4-hour period). The scrounging option becomes the default unless the characters can barter for the components or salvage them and most repairs require 1D10 specific parts (engine, tracked suspension) so this may be difficult.

So my suggestions, based on the above:
  • Protect your mechanic, preferably have more than one in the group
  • Always do at least minimal maintenance between trips
    • If the vehicle has a high Wear value, invest time in preventative maintenance
  • Always carry a full complement of relevant tools
  • Always carry a varied selection of spare parts

Simplification & Risk Approach

Initially I wasn't too sure how to go about simplifying these rules, but I think I've instead settled on a way to build in a degree of "risk management" as a standard travelling approach based on the importance of Wear and minimal maintenance time as interacting variables with the number of 4-hour periods that are part of the stationary time in a typical "Travel Day", in most instances this is only 2.

Wear is far, far the most important in influencing risk. As a variable it influences not only the chance of a potential breakdown but also the severity of the breakdown (major vs minor) - the former can be modified by preventative maintenance (time) whereas the latter is fixed and results in the need for parts, compounding the difficulty of resource management aspects.

To abstract all this for a GM's use in play, I think it's easier to work out a risk approach based on the chance of a potential breakdown derived from the vehicle's Wear value and then factor in the success rate of preventing a breakdown attributable to an Elite mechanic (Asset 15, ie only 25% of actual breakdown when checked for) and then work out the maintenance time needed:

  • Cautious - 10% chance of potential breakdown, 2.5% (1 in 40) chance of actual breakdown
  • Safe - 20% chance of potential breakdown, 5% (1 in 20) chance of actual breakdown
  • Normal - 40% chance of potential breakdown, 10% (1 in 10) chance of actual breakdown
  • Risky - 80% chance of potential breakdown, 20% (1 in 5) chance of actual breakdown

Note: if the group (or vehicle) only has access to a Experienced mechanic (Asset 11, ie ~45% chance of failing a DIFF skill check), this roughly doubles the chance of a breakdown, shifting the risk up one category eg from Safe to Normal or Normal to Risky - this is exactly doubled if the mechanic has an Asset of 10 in Mechanic, just one point higher than a Novice NPC Asset of 9.

Minimal maintenance is expressed in 2-hour increments, ranging from simple vehicles (motorcycles, HumVees etc) with a value of 2 hours up to 16 hours for main battle tanks (M1A1, T80 etc). These are therefore effectively multiples of 4-hour periods similarly ranging from 0.5x to 4x, which are a component of the standard "Travel Day".

  • x0.25  Mnt 1: Bicycle, Wagon, Cart, Trailers
  • x0.5    Mnt 2: Motorcycle, HumVee, UAZ, 3/4 ton truck
  • x1.0    Mnt 4: 2.5 ton truck, 5-ton truck, 10-ton truck
  • x1.5    Mnt 6: M113, LAV-25, BTR-80, OT-64
  • x2.0    Mnt 8: M2A2 Bradley, Leopard I, T-55
  • x2.5    Mnt 10: AIFV, M8 AGS
  • x3.0    Mnt 12: BMP-2, BMP-3
  • x3.5    Mnt 14: M1, M1A1
  • x4.0    Mnt 16: M1A2, T-80

Combining the two, use the following table to calculate the number of 4-hour periods of maintenance required to achieve the desired risk of breakdown for the next 8-hour travel window:

Breakdown Risk (Assuming Elite Mechanic Asset)

Preventative maintenance can RAW reduce the potential breakdown risk to 0%, but the concept of a vehicle never breaking down in the Twilight World seems unlikely so I'd keep the minimum risk as 10%, regardless of the amount of maintenance undertaken.

For an average group, allowing for two rest periods per day, travelling only one or two 4-hour periods per day, spending up to 7 periods a week is no issue and even 14 hours a week is achievable if the group travels one period per day. For vehicles with a "Still Week" value of 1 where the group must wait 7 days before travelling again, a mechanic can easily spend up to 21 periods in maintenance and still have a free period and two periods for sleeping.

Example #1: Monk's motorcycle, with Wear 5 and Mnt 2, needs two 4-hour periods of maintenance to travel at "Safe" risk ie 10% chance of a breakdown or only one and a half 4-hour periods if wanting to travel at "Cautious" risk ie 20% risk of breakdown. 
Example #2: the group's LAV-25, with Wear 6 and Mnt 6, needs six 4-hour periods of maintenance to travel at "Cautious" risk ie 20% risk of breakdown and three 4-hour periods at "Average" risk ie 40% risk of breakdown. To reduce the risk to "Safe" or 10% risk of breakdown, a mechanic must spend seven and a half 4-hour periods in maintenance.
Example #3: the group's HumVee barely limps along with Wear 9 and Mnt 2 so needs four 4-hour periods of maintenance to travel at "Safe" risk or 10% chance of a potential breakdown. Due to it's high Wear value and risk of destruction if it reaches Wear 10, it should command the priority of mechanic time.
Example #4: the combined fleet of vehicles (including the motorcycle) requires 13.5 periods of maintenance to travel at "Safe" risk - slightly less if the motorcycle is only maintained when needed, slightly more if it used to travel while the other vehicles are stationary for 10-11 days and the group is distilling enough fuel for the next burst of travel. This should not be a major issue if the Mechanic is readily available and the group is stationary but they need to spend at least 2 periods a day in maintenance.  


The need for maintenance is a readily winnable mini-game within the core T2k v2.2 rules.

For most groups not carrying significant reserves of extra fuel, the typical stuttering movement between distilling enough methanol to travel one 4-hour period provides ample time for appropriate maintenance to ensure "Safe" risk travel ie a potential breakdown risk of only 10%. Coupled with even a Novice/Experienced mechanic (Asset of 10), this equates to only a 1 in 20 actual breakdown risk, even less with an Elite mechanic (1 in 40, 2.5% risk) provided appropriate tools and a supply of spare parts are available - these should be a priority for all groups.

As breakdowns are time-consuming, expensive (in terms of spare parts) and potentially dangerous (stranding the group stationary in often hostile territory), a typical group should try and avoid them whenever possible unless the GM feels the added risk serves a narrative function.

Compared to fuel scarcity, breakdowns are readily solved as a major limiting factor for overland travel by spending time, so unless the group needs to travel continuously at 8 hours per day and their fleet of vehicles requires more than 7 (or 14) periods of maintenance per week the mini-game does not affect play significantly.

A group containing a mechanic/driver character like my pregenerated "Wheelman" can travel in relative security, provided the fleet of vehicles has a 4-hour maintenance period multiple of less than 14 per week, which seems readily achievable... 


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