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Ari Holopainen / gearbox11 | |
| A. Auxiliary Gearboxes: Here is updated small collection of auxiliary gearboxes that are used in trucks and tractors together with main gearboxes. All designs are quite basic so you don’t need old 14 teeth thin bevel gears or new 28 teeth gear. Although all designs have brick frame they should be possible to build with studless frame. A.1. Range-change unit, gear step 5,00: Using examples: -heavy duty 10-speed (5x2) -heavy duty 12-speed (2x3x2) -severe duty 14-speed (2x3x2+2)
These two setups are 2-speed range-change units, which are used in heavy truck transmissions as an auxiliary gearbox. Range-change unit’s idea is to enlarge main gearbox’s speed range by adding two different ranges. So you can shift main gearbox through twice, first in low range and then in high range. Real range-change unit is pneumatic-operated preselector gearbox which shifts when main gearbox goes through neutral. These lego designs are not so clever, they are only mechanical and non-preselective. Available is two setups: direct drive synchromesh and direct drive sequential. Low ratio is 5,00 and high ratio 1,00 which gives quite large range gear step 5,00.
Note the shift lever position locking method in sequential setup. Idea is that shift lever axle goes slightly inside technic plate’s hole. When shifting you tilt lever to free it, move axle to new position and lock lever in another hole. It is simple and useful for all sequential sliding axle gearboxes. Other notable thing is that in direct drive synchromesh 12 teeth double bevel gear can be replaced with two 14 teeth thin bevel gears. This gives gear step 4,29 which can be used for example in heavy duty 16-speed transmission. A.2. Range-change unit, gear step 4,50: Using examples: -linehaul 10-speed (5x2) -severe duty 14-speed (2x3x2+2) -heavy duty 16-speed (2x4x2)
Here is three setups of another 2-speed range-change unit. Setups are: direct drive synchromesh, direct drive sequential and underdrive sequential. In direct drives low ratio is 4,50 and high ratio 1,00. In underdrive low ratio is 6,00 and high ratio 1,33 and it suits to high speed motor design. So gear step in these setups is middle-sized 4,50.
One note is that direct drive sequential can be difficult to shift to high range due to S(16)-S(16) spur gear pair. When problem occurs run motor shortly to move gear wheels’ teeth in new position and try shifting again. A.3. Range-change unit, gear step 4,00: Using examples: -8-speed & 9-speed (4x2 & 4x2+1) -heavy duty 14-speed (2x3x2+2) -linehaul 16-speed (2x4x2) -heavy duty 18-speed (2x4x2+2) -6+2R-speed & 8+2R-speed tractor (3x2 & 4x2)
Range-change unit with gear step 4,00 is quite versatile design. It can be used not only in many truck transmissions but also in some tractor transmissions. Available is three setups: direct drive synchromesh, direct drive sequential and underdrive sequential. In direct drive ratios are 4,00 and 1,00 and in underdrive design 6,00 and 1,50.
In underdrive version gear wheels are chosen so that you can easily add a third ratio in this gearbox. In that case you convert range-change unit to 3-speed splitter/range-change unit. Check A.7. Auxiliary 3-speed gearbox for further information. Range-change unit’s gear step can be also smaller than 4,00. Usually 10-speed and 12-speed heavy duty transmissions need largest range step while transmissions with crawler gear(s) can use smaller range step. A.4. 4-speed range unit for tractor: Using examples: -16+16R-speed tractor (4x4) -12+4R-speed tractor (3x4)
These are 4-speed range units (ranges A, B, C and D) and designed for tractor use. Available is both synchro and sequential design. Range steps A-B and C-D are both 2,00 but step B-C is only 1,50. Notable thing is that step B-C is smaller on purpose not because of simpler lego design. Idea is taken from John Deere’s transmissions and it’s to get more gears for field working speeds 4-12 km/h.
Other note is that these range units are designed to use only with main gearboxes. Gear steps 2,00 are simply too large for using these designs as single gearbox. These designs have replaced original sequential design in which all gear step were 2,00. If you still need that original design you can check main gearboxes of 12-speed Twin Splitter transmissions on main page. A.5. Splitter unit, gear step 1,25: Using examples: -12-speed (2x3x2) -14-speed (2x3x2+2)
Splitter unit is a different kind of auxiliary gearbox used in trucks. Its idea is to double the number of gears and halve the gear steps. Real splitters are pneumatic-operated preselector gearboxes which shift when you press clutch pedal (synchromesh gearbox) or cut torque in drive line (non-synchro gearbox). Again lego designs are only mechanical and non-preselective.
Available is three setups: direct/overdrive synchromesh, direct/overdrive sequential and underdrive sequential. Direct/overdrive designs can be used two ways: in direct mode low ratio is 1,25 and high ratio 1,00 but in overdrive mode (swapped input and output) low ratio is 1,00 and high ratio 0,80. Underdrive design is for high speed motor use and its low ratio is 2,50 and high ratio 2,00. One note about underdrive sequential is that shifting to low ratio can be difficult due to XS(8)-S(16) spur gear pair. If problem occurs drive motor shortly to turn gear wheels’ teeth in new positions and try shifting again. This splitter gear step 1,25 splits equally main gearbox’s step 1,56 and it’s useful for main gearbox steps 1,50-1,67. This leads to compound shift steps 1,20-1,33. If you want to enlarge overall gear ratio by adding progression in gear steps lower gears can have as high step as 1,80 (gives compound shift step 1,44). In heavy duty 12-speed splitter’s step can be larger like 1,28 or 1,31 when using geometrical gear steps. Also larger splitter step (1,36) can be in 10-speed splitter-type transmission (5x2). Examples can be checked from main page: splitter step 1,28 is in A.4. 14-speed transmission version IV, step 1,33 in L.2. 12-speed version IIA & IIB and step 1,36 in M. 10-speed transmission. A.6. Splitter unit, gear step 1,20: Using examples: -16-speed (2x4x2) -18-speed (2x4x2+2) -16+8R-speed tractor (2x4x2)
This splitter’s gear step 1,20 suits to transmissions with lots of gears, it can be used in 16-speed and 18-speed trucks or as mechanical splitter of 16+8R-speed tractor. In tractor use splitter is used for more accurate working speed control, not for splitting main gears while driving.
Available is three setups: direct/overdrive synchromesh, direct/overdrive sequential and underdrive sequential. Again direct/overdrive designs can be used two ways: in direct mode low ratio is 1,20 and high ratio 1,00 but in overdrive mode (swapped input and output) low ratio is 1,00 and high ratio 0,83. Underdrive design is for high speed motor use and its low ratio is 2,00 and high ratio 1,67. Notable thing in direct/overdrive sequential is that shifting can be difficult due to XS(8)-S(16) and S(16)-S(16) spur gear pairs. If problem occurs drive motor shortly to turn gear wheels’ teeth in new positions and try shifting again. Splitter step 1,20 splits equally main gearbox’s step 1,44 and it’s usable in main steps 1,40-1,50 which give as compound shift steps 1,17-1,25. Crawler gear’s step in 18-speed transmission can be larger 1,67 without getting too large compound step (acceptable 1,39). In 18-speed transmission splitter step can be even smaller 1,17 but here is no examples of it. A.7. Auxiliary 3-speed gearbox, compound splitter/range-change unit: Using examples: -13-speed (4x3+1)
This one is a 3-speed auxiliary gearbox with compound splitter and range-change unit. Structure is based on range-change unit where splitter unit is available in high range only. The idea is to get progressive-like gear steps for truck transmission use. Available is both original sequential setup and alternative synchro setup. Sequential design has underdrive ratios: Low range (LO) has ratio 6,00, ratio in high range with splitter low (HI-L) is 1,50 and splitter high (HI-H) 1,25. Altogether range step is 4,00 and splitter step 1,20. In real auxiliaries HI-L is usually direct and HI-H overdrive. For more realistic lego ratios you can add Su(12)-XS(8) or M(24)-S(16) overdrive gear pair between auxiliary and main gearbox. This way you get ratios 4,00, 1,00 and 0,83 without changing gear steps. This sequential setup is simple and compact design with good efficiency. Only problem is difficult shift to HI-H due to S(16)-S(16) spur gear pair. If shifting problems become annoying available is also direct drive synchro setup with identical gear steps. So, low range ratio LO is 4,80 and in high range low split HI-L has ratio 1,20 and high split HI-H 1,00. This synchro version has two high-low shift levers: left one for splitter and right one for range change. This arrangement allows remote auxiliary shifting if you add mini motors to shift levers. But note in this design that splitter must be in low position to enable low range. This feature is copied from real Fuller’s auxiliary. B. Main Gearboxes: Geometrical gear steps Here is updated small collection of main gearboxes to be used in trucks and tractors. Largest number of gears in single manual gearbox is 7+R and that is not usually enough in truck and tractor transmissions. This will lead either too small overall gear ratio or too large gear steps so they use one or two auxiliary gearbox to multiply main gearbox’s number of gears. This way you will get also slow gears without too large gear steps. Auxiliaries also mean that you can’t use progressive gear steps or progression must be small. These lego designs are mainly with brick frame but in many cases studless frame should be possible. Mainly reverse gear’s S’(16C)-XS(8)-Su(12) gear train is problematic in studless frame. In some cases you can’t avoid old 14 teeth thin bevel gears or new 28 teeth gear without losing realistic ratios. B.1. Basic 5-speed synchromesh gearbox, overall gear ratio 9,00: Using examples: -5x4 & 5x3 twin stick
This 5-speed synchromesh gearbox is based on very simple gear pairs. Front and back movement of the shift lever handles between ratios 1,67 (done by 12 and 20 teeth gears) and 1,00 after the synchro parts. Shift lever’s left and right movement chooses between ratios 9,00, 3,00 and 1,00 before the synchro parts (done by 8 and 24 teeth gears). Altogether, gear steps are quite good but not optimal: they vary between 1,67 (gear steps 2-3 and 4-5) and 1,80 (gear step 1-2 and 3-4). All shiftings should have the same gear step value (or almost same) in transmission with geometrical gear steps.
This 5-speed main gearbox is simple but realistic auxiliaries for it is another job. Easiest design is to add 2-speed splitter with gear step 1,25-1,33. It’s simple lego design but ratio set is not realistic. For 5x4 and 5x3 twin stick transmissions this 5-speed main gearbox suits quite well. But auxiliaries of twin stick transmissions are more complex designs. So for realistic lego twin stick transmission you’ll need to check section N. Twin Stick Transmissions on main page. This gearbox has two alternative upgrade possibilities: 6-speed gearbox or 5-speed gearbox with a reverse gear. 6-speed gearbox has overall gear ratio 15,00 and it suits to 12-speed splitter-type truck transmission (6x2). Suitable splitter gear step is 1,25-1,33, but this lego design won’t have realistic ratio set. In real 12-speed splitter-type transmission splitter step is smaller and main gearbox has progressive gear steps. For basic lego design with splitter step 1,33 you can check L.2. 12-speed version IIA & IIB and for more realistic lego design O.8. 6-speed & 12-speed on main page. B.2. Basic 6-speed synchromesh gearbox, overall gear ratio 3,47: Using examples: -12+12R-speed tractor (6x2) -18+6R-speed & 24+6R-speed tractor (6x3 & 6x4)
This 6-speed gearbox is also basic version but it uses different gear pairs than previous 5-speed main gearbox. Now ratios before synchro parts are 1,00, 1,67 and 2,78 and they are done by 12 and 20 teeth gears. After synchro parts ratios are 1,00 and 1,25 which is done by 16 and 20 teeth gears. Gear step are not very good because they vary between 1,25 and 1,33. All in all gear steps are smaller so this main gearbox doesn’t need splitter but range-change unit.
This 6-speed design is for tractor use, in truck world 6-speed main gearbox with range-change unit is not used. So, in tractors 6-speed main gearbox can be used with 2-speed range unit and driving direction changer (shuttle). This gives 12+12R-speed design in which range gear step 4,00 is quite typical. Other use for 6-speed main gearbox are 18+6R-speed & 24+6R-speed tractors with 3+R-speed & 4+R-speed range units (ranges low, medium, high and reverse, additional creeper in 4+R-speed). In these designs ranges overlap heavily. For more info check T.5. 18+6R-speed & 24+6R-speed on main page. For truck world you will need modification: replace 1st gear with reverse gear to get 5-speed gearbox (overall gear ratio 2,78). It suits to 15-speed truck transmission (5x2+5) which has 10 road speeds in two ranges plus 5 deep reduction gears for low speed operating. More info about this is in section F. 15-speed Transmissions on main page. B.3. Basic 3+R-speed synchromesh gearbox, overall gear ratio 3,00: Using examples: -3+R-speed personal car -12-speed (2x3x2) -6+2R-speed tractor (3x2)
This basic 3+R-speed gearbox is a small brother of the earlier basic 5-speed synchromesh gearbox: 1st and 2nd gear are removed and reverse gear is added. Reverse gear adds some complexity for this design but it’s still as small as basic 4-speed. Available is two setups: in personal car/truck setup reverse gear is slower than 1st gear but in tractor setup faster. This difference is typical for real transmissions.
Gear step 1-2 is 1,80 and gear step 2-3 1,67 so this gearbox has actually progressive gear steps (the higher gear the smaller gear step between gears). So this gearbox suits straight to be used as old 3+R-speed personal car gearbox. In truck use this main gearbox will need both splitter and range-change unit which leads to 12-speed design (2x3x2). Suitable range gear step is 5,00 and suitable splitter steps are between 1,25-1,33. Larger splitter step leads to higher overall gear ratio but reduces gear step progression and performance in high speeds. My recommendation is splitter step 1,25 with stronger progression in gear steps, it gives overall gear ratio 18,75 which still suits very well to heavy duty trucks. In tractor transmissions range is not usually changed during driving. So range step is smaller than in truck use, or ranges can even overlap. For 6+2R-speed tractor with this main gearbox suits range unit with gear step 4,00. This design can be enlarged to 12+4R-speed version by adding Hi-Lo powershift. Typical powershift step will be around 1,33. B.4. 5+R-speed synchromesh gearbox, overall gear ratio 4,00: Using examples: -as 4+C+R-speed: heavy duty 13-speed & 18-speed (4x3+1 & 2x4x2+2) -as 4+R-speed: linehaul 16-speed (2x4x2) -as 5-speed: 15+15R-speed & 45+45R-speed tractor -as 4-speed: 8+4R-speed, 16+8R-speed & 12+8R-speed tractor
This 5+R-speed main gearbox is quite versatile design although it’s never used in its basic form. Available is two setups: old school setup has 14 teeth thin bevel gears with 20 teeth gear (ratio 1,43) and modern setup 20 teeth gear with new 28 teeth gear (ratio 1,40). These are for smaller gear step after synchro parts, front ratios 4,00, 2,00 and 1,00 are done by 8 and 16 teeth gears.
When you use this as 4-speed gearbox that has crawler (C) and reverse gear you can build heavy duty 13-speed and 18-speed truck transmissions. They have range-change unit and splitter but in 13-speed version splitter is available in high range only. And crawler gear is used in low range only. Suitable range gear step is 4,00 and splitter step 1,20. 13-speed version can use earlier 3-speed auxiliary that has compound splitter/range-change unit. When using as 4+R-speed design (no crawler gear) you can get linehaul 16-speed transmission. It uses same range and splitter steps as previous 13-speed and 18-speed. But you need some modifications in main gearbox: when removing crawler gear reverse gear becomes too slow. So I recommend to make reversing gear train XS(8)-XS(8)-XS(8) as front ratio between left and middle synchro axle and put reverse gear next to 1st gear. When using 5-speed design without reverse gear you can build 15+15R-speed and 45+45R-speed tractor transmissions. They have 3-speed range unit and driving direction changer (shuttle), 45+45R-speed version also 3-speed powershift. For more info you need to check 45+45R-speed designs on main page. When you remove crawler and reverse gear you can use 4-speed main gearbox in 8+4R-speed tractor transmission in which auxiliary has ranges high, low and reverse. And this 8+4R-speed design can be enlarged with Hi-Lo powershift (16+8R-speed), mechanical splitter (16+8R-speed) or creeper range (12+8R-speed). Suitable gear step for splitter is 1,20. For more info you need to check section S. Tractor Transmissions Part I on main page. And one note: if you build 16-speed and 18-speed without splitter you get 8-speed and 9-speed (4x2 & 4x2+1) truck transmissions. But quite large gear steps lead to bad performance in high speeds so they make top step 7-8 (and step 3-4 due to range-change unit) smaller than others. This helps to keep suitable engine rpm in all speed limits 50, 60, 70 and 80 km/h. In lego world this is not so big issue so you can use this main gearbox in 8-speed and 9-speed transmissions. B.5. 5+R-speed synchromesh gearbox, overall gear ratio 3,33: Using examples: -10-speed (5x2)
This 5-speed main gearbox is designed for 10-speed transmission with range-change unit. 10-speed transmission is quite simple and logical for truck transmission but realistic ratios lead to quite complex lego main gearbox.
Suitable range gear step for this main gearbox is 4,50. Combination gives overall gear ratio 15,00 which suits to linehaul and easier heavy duty purposes. So, this lego design is not the simplest but it gives simple and logical operating. Only reverse gear uses old 14 teeth thin bevel gears and this is for slightly slower reverse gear than 1st gear. If you don’t have those gear wheels you can copy reverse gear train S’(16C)-XS(8)-Su(12) from 3+R-speed main gearbox and transfer torque to output axle via S(16)-S(16)-S(16) gear train. B.6. 4+R-speed synchromesh gearbox, overall gear ratio 3,00: Using examples: -heavy duty 16-speed (2x4x2) -8+2R-speed tractor (4x2)
This 4+R-speed main gearbox is designed for heavy duty 16-speed transmission so it needs both splitter and range-change unit. Also this one is more complex design due to realistic ratio set. Suitable splitter gear step is 1,20 and suitable range step 4,50 or 4,29, the latter you get when you modify range-change unit with gear step 5,00.
Other use for this main gearbox is 8+2R-speed tractor in which range-change unit has gear step 4,00. Although reverse gear is already faster than 1st gear you can modify it as fast as 2nd gear when using this main gearbox in tractor. To get it use XS(8)-XS(8)-XS(8) gear train between middle and left synchro axle and keep reverse gear’s clutch gear next to 2nd gear. This ratio set is not possible without old 14 teeth thin bevel gears. If you have them you can build lego 16-speed transmission with very realistic ratios. If you have only new 28 teeth gear you can build 16-speed linehaul transmission with smaller overall gear ratio. For more info check 4+R-speed setup in chapter B.4. 5+R-speed synchromesh gearbox. B.7. Simple 2-speed synchromesh gearbox version A & B, gear step 1,71:
Here is simple 2-speed gearbox if you have only one transmission driving ring. In real automotive transmissions gear steps are usually under 2,00 because combustion engines are not good at handling large steps in shifting. So this lego transmission has ratio 12/7=1,71 in 1st gear and 1,00 in 2nd gear. Available is version A with brick frame and version B with studless frame. Transmission is quite simple to build but there are also building instructions available, check link BuildIt in Brickshelf Gallery or YouTube.
There are also two optional ratio sets available: When you replace 14 teeth bevel gears with 12 teeth gear you get ratio 2,00 for 1st gear. If you swap 14 teeth bevel gears and 12 teeth gear ratio of 1st gear will be 7/3=2,33. (If you replace this gear pair with 8 and 16 teeth gear pair you get synchromesh range-change unit with gear step 4,00.) As an other option you can make remote shifting system by adding small motor on shift lever axle. When you don’t use neutral position shift lever has only two positions and shift lever’s movement is limited with bricks. So you can do remotely simple up- and downshiftings between 1st and 2nd gear while driving. Actually this design is not a real main gearbox but ancient 2-speed personal car gearbox. But you can use this with splitter and range-change unit to get 8-speed transmission that has three Hi-Lo gearboxes. Suitable range gear step is 3,00 and splitter step 1,25-1,33. This kind of transmission doesn’t really exist but can be used as remote shiftable design with realistic ratios for lego playing. C. Transfer Cases: Transfer cases are used in off-road vehicles and they are needed for two reasons. They devide power to front and rear axle to get 4x4 design and with 2 speeds allow also low speed driving. Transfer case’s high (H) is for everyday use on the roads and low (L) is for off-road driving when low speeds are needed. C.1. Version I, gear step 2,25: With 5-speed version I This transfer case is together with 5-speed version I so check it on main page if you need more info about main gearbox. Transfer case is continuous 4WD with lockable centre differential so there are four options: H4 (high 4WD) and L4 (low 4WD) with centre differential in use or locked. High ratio is 2,00 and low ratio 4,50 so gear step is 2,25. Usually transfer case’s high ratio is direct but these ratios gave smaller construction with proper gear step. You can think this transfer case as part of final drive so you don’t need so large ratios in front and rear axle differentials.
C.2. Version II, gear step 2,25: With 5-speed version III Here is another transfer case for off-road vehicles and it’s together with 5-speed version III. Again transfer case’s high ratio is 2,00 and low ratio 4,50 so gear step is 2,25. This version II is updated version of previous transfer case version I and it has 5 options: H2 (high RWD) plus H4 (high 4WD) and L4 (low 4WD) with centre differential in use or locked.
This transmission uses original setup of 5-speed version III, check alternative setup or tutorial version for more compact and simpler main gearbox. C.3. Version III, gear step 2,40:
This is alternative setup for transfer case version III, original design P.17. Old 3-speed & transfer case version III is now on page Junkyard. This transfer case is old-fashioned two stick design: one stick for high and low selection and other one to switch front wheel drive on or off. High ratio is 1,25 and low ratio 3,00 so gear step of this transfer case is 2,40.
This design is part time 4x4 without centre differential so on the road and other good conditions it’s recommended to use only rear wheel drive. But when conditions get worse you can switch on front wheel drive and perhaps low selection if low speeds are needed. Available is also a remake for this type of two stick transfer case. For more information you can check P.17. 3-speed & transfer case version VI in section P. Personal Car Transmissions on main page. C.4. Version IV, gear step 2,50:
This is alternative parallel setup for transfer case version IV, original inline design was introduced in now junked 3-speed semiautomatic & transfer case version IV. This is another part time 4x4 design but it has one shift lever with three positions: H2 (high RWD), H4 (high 4WD) and L4 (low 4WD). So in good conditions you use rear wheel drive (H2) and in bad conditions high or low four wheel drive (H4 or L4). High ratio is 1,33 and low ratio 3,33 which gives gear step 2,50.
With 3-speed semiautomatic Inspirer: Ford Bronco II This is remake of 3-speed semiautomatic & transfer case version IV. It is based on off-road vehicle that has 3-speed automatic gearbox with torque converter and 2-speed part time 4x4 transfer case. In lego version 3-speed semiautomatic “main gearbox” is actually 2 motors and a planetary gear. For more information you can check B.8. 3-speed semiautomatic in Planetary gears.
In this remake transfer case’s low ratio is 2,50 and high ratio is direct 1,00, so gear step is still 2,50. Reason for this remake is more compact design. Original design was very space consuming and it’s moved to page Junkyard. C.5. Version V, gear step 2,25:
This transfer case version V uses smallest possible gear wheels so gearbox itself is very small design. But shift lever needs some more attention while there are not much places where to put it.
Again design is part time 4x4 and shift lever has three positions: H2 (high RWD), H4 (high 4WD) and L4 (low 4WD). So on the road you drive with rear wheel drive (H2) and four wheel drive positions H4 and L4 are for bad conditions only. This time high ratio is direct 1,00 and low ratio 2,25 so gear step is also 2,25. This transfer case has modified version together with P.8. 4-speed version III in section P. Personal Car Transmissions on main page. That 4-speeder is wide ratio design with typical ratio set of off-road vehicles so it’s logical to offer also additional lego transfer case.
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