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Ari Holopainen / truck2 | |
| K. 16-speed Transmissions, 4 reverse gears: 16-speed transmission is the most effective way to get lots of gears in truck transmissions. Every main gearbox’s gear can be used in low and high range, also every gear can be splitted with splitter unit. Main gearbox has only 4 gears and a reverse gear, but altogether you’ve got 16 forward gears and 4 reverse gears. Forward gears are: 1L-1H-2L-2H-3L-3H-4L-4H-range_change-5L-5H-6L-6H-7L-7H-8L-8H. ZF Ecosplit is the best known 16-speed transmission but also Mercedes and older Volvos have 16-speed transmissions. I don’t count Eaton’s design as genuine 16-speed transmission while it’s actually automated 18-speed transmission without overdrive gears 8L and 8H. Eaton doesn’t advertise this fact but larger 1,44 gear step in shift 2-3 reveals the truth, it’s 18-speeder’s shift CH-1L. 16-speed ZF Ecosplit inspired transmission is also in my Lego 4x2 truck 16-speed, page Vehicles. K.1. Version I, overall gear ratio 15,43: Range + splitter + main gearbox Inspirer: ZF Ecosplit
This 16-speed version I is inspired by famous ZF Ecosplit. But it means that lego range-change unit and main gearbox are a little bit more complicated to get suitable overall gear ratio. Available is two lego setups. Old original setup is underdrive and suits best to high speed motor while new alternative setup is overdrive and for low speed motor. Gear steps and overall gear ratio are identical in these setups but reverse gears have some difference: in original setup reverse gears are slower than 1st and 5th forward gears but in alternative setup faster. After making pictures I found possible problem in alternative setup: reverse gear’s M(24)-Mu(20) gear pair has weak mesh so it can lose contact under high load. If this problem occurs you have to relocate XS(8)-M(24)-Mu(20) gear wheels next to bricks by moving other main gearbox’s front gear pairs one stud forward. This conversion is done in updated LDraw file and YouTube video Building example alter. There is also a ratio comparison between alternative lego setup and overdrive version of real ZF Ecosplit. Major difference is that ZF’s range-change unit has larger step than lego version, otherwise ratios and gear steps are very close to each other. If you don’t have transmission driving rings available is also sequential sister design. Check 16-speed truck in section R. Sequential Transmissions. One notable thing is that in ZF Ecosplit high range reverse gears are not mentioned in shift pattern or brochures. If you have double H shift pattern version high range reverse gears are not available at all. And in single H shift pattern 16-speed gearbox high range reverse gears are too fast to move off, so you need to start with low range and do difficult (large gear step) range change to get fast reverse gears. Non synchro reverse gear complicates job even more. But in lego version high range reverse gears can be used while you can move off with every gear. Actually you don’t even need reverse gears in lego gearbox while motor works in both directions. K.2. Version II, overall gear ratio 13,71: Range + main gearbox + splitter Inspirer: Volvo SR62
This 16-speed version II uses simpler gear pairs than previous version I and it leads to partly smaller gear steps and smaller overall gear ratio. When comparing them to real world’s transmissions closest inspirer is Volvo’s old SR62. When compared to my earlier lego designs closest is 18-speed transmission without crawler gears.
Range-change unit’s shift lever is locked by rubber belt. For shifting tilt lever slightly to right to unlock it and pull or push lever into new position. Main gearbox and splitter are located parallel with special design: There is a shortcut from main gearbox’s synchro axle to splitter’s output axle via two clutch gears when main gearbox’s gears 2 or 4 are selected with high split. So gears 2H, 4H, 6H and 8H have less stages in powerflow and better efficiency. When building this transmission note that three synchro axles on the left belong to main gearbox and the last one on the right is splitter’s axle. For main gearbox’s shift lever use 8 studs long axle, put longitudinal bricks at the both ends and bush on the right side of the left brick. For splitter’s shift lever use axle pin with 3rd longitudinal brick on the right side and locate shift lever right next to middle brick. This way both shift levers are well supported. If you don’t have old 14 teeth thin bevel gears you can do simple conversion with new 28 teeth gear (medium large ML in my notations). In main gearbox move left axle under synchro axles one stud to left and replace rear Th(14)-Mu(20) gear pair with Mu(20)-ML(28) gear pair. This leads to minor changes in ratios, gear steps and overall gear ratio but keeps design still realistic. This transmission has sister transmission E.2. Small step 16-speed for linehaul truck in section E. Flat Gearbox Designs on page Basic & special designs. K.3. Version III, overall gear ratio 15,75: Main gearbox + range + splitter Inspirer: ZF Ecosplit
This 16-speed version III is also inspired by ZF Ecosplit and is some kind of upgrade of earlier 16-speed version I. This time design is direct drive so it suits to both low and high speed lego motors.
So, this lego design has some improvements compared to version I. First change is that splitter is synchro version and range-change unit sliding axle design. This change is to minimize sliding axle shifts. Range-change unit has also double bevel gear in all gear pairs to ensure easier shifts than in design that has also spur gear gear pairs. Range step is also larger 4,38 which gives lego design more accurate ratio set compared to real ZF Ecosplit. Actually lego range step 4,50 would be closer to ZF’s range step 4,57, but it would lead either underdrive design or less usable spur gear gear pair in range-change unit so I abandoned it. You can check ratio set differences between lego version and ZF Ecosplit from picture Ratio comparison. Other improvement is that range-change unit and splitter are fully parallel which leads to slightly shorter design. So, if you have both old 14 teeth thin bevel gears and new 28 teeth double bevel gear (ML, medium large in my notations) here is my best lego version of ZF Ecosplit. For lego European trucks like DAF, Iveco, MAN or Renault this transmission is your choice. But if you don’t have transmission driving rings available is also sequential sister design. Check 16-speed truck in section R. Sequential Transmissions. L. Basic Designs With Splitter: These are basic lego transmissions in which main gearboxes use basic XS(8)-M(24) gear pairs before synchro parts and Su(12)-Mu(20) gear pair after them. 10-speed version has 5-speed main gearbox with reverse gear plus splitter and 12-speed 6-speed main gearbox plus splitter. Splitter unit has several different designs but splitter step is always 1,33. But all splitter steps between 1,25-1,33 are usable with these designs. Smaller splitter step gives better performance in high speeds due to smaller step between two top gears but it also reduces overall gear ratio and makes gear steps vary more. L.1. 10-speed, 2 reverse gears, overall gear ratio 12,00: Splitter + main gearbox
This basic 10-speed is version X of my all 10-speeders and designed for medium duty and linehaul trucks. It contains 5-speed main gearbox with reverse gear plus splitter. This one is short inline design, length is only 17 studs with motor and it fits to 8 studs width.
This basic 10-speed is only simple and compact design for lego builders without direct inspirer from real truck transmissions. So it’s very lego builder friendly but for reality seekers I recommend to check M.2. 10-speed with splitter version II, which is inpsired by older Scania’s medium duty trarnsmissions. Although this lego design is very simple and compact upshifting procedure is not the simplest maneuver. In real splitter-type transmissions splitter is pre-selected and button operated. Upshifting procedure goes so that every other shift is easy splitter shift and every other shift more complex compound shift. Skipping gears is easy by ignoring splitter shifts. But lego splitter is pure mechanical so compound shifts are more complex. If you prefer simple operating it’s better to choose 9- or 10-speed transmission with range-change unit, then auxiliary is shifted only once during upshifting procedure. For lego designs check sections D. 9-speed Transmissions or I. 10-speed Transmissions. L.2. 12-speed version A & B, overall gear ratio 20,00: Main gearbox + splitter
This basic 12-speed is version IV of my all 12-speeders and it’s an example how to build very simple and compact lego heavy duty transmission that has 6-speed main gearbox and splitter. Essential in this design is to use basic ratios and to put main gearbox and splitter unit parallel. This way you get 12 speeds in gearbox that is as large as my 7-speed gearboxes. Note in this parallel design that three synchro axles on the left are part of main gearbox and they need 6-position H shift patterned shift lever. Splitter’s shift lever is shown in pictures and it uses right synchro axle.
Version A has brick frame but also version B with studless frame is available. All axles and gear pairs are same in both versions except that splitter’s 4 studs long axle is changed to 5 stud axle. Studless frame is not so colorful as brick frame so download LDraw file or check Building example B if you have difficulties to figure out the construction. Note that shift levers are located parallel and they have own support axles. Put axles only half studs inside middle axle support part called 180 degree angle connector. This way you get both shift lever axles supported at the both ends. There is also Lego gearbox tutorial part II from this transmission, available with Brickshelf Gallery pictures and YouTube slide show. Unlike versions A and B tutorial version is direct drive. Also this lego transmission doesn’t have inspirer, mainly because of large overall gear ratio and geometrical gear steps. For reality seekers I recommend to check O.8. 6-speed & 12-speed in O. Medium & Light Truck Transmissions. It’s inspired by older 12-speed ZF S6-66 + GV66 which has 6-speed main gearbox with some progression in gear steps and smaller step in splitter so also overall gear ratio is smaller. M. 10-speed Transmissions With Splitter, overall gear ratios 10,21: Main gearbox + splitter Inspirers: -Scania GS771 (original lego setup) -Scania GS770 (alternative lego setup) 10-speed transmission with splitter is very special for me. When I was training for my driving license, I drove Scania, which was equipped with 10-speed GS771 transmission containing 5-speed main gearbox with reverse gear plus splitter unit. Version I original setup is my old lego design and alternative setup was added later. Version II original and alternative setup are modernized more compact lego designs. These transmissions have sister transmission D.1. 10-speed with splitter for truck in section D. Gearboxes With 2-speed Motor, page Basic & special designs. Transmission parts are exchangeable so you can replace splitter of these transmissions with 2-speed motor or use these splitters with main gearbox of that 2-speed motor transmission. M.1. Version I:
Here is version I original and alternative setup of my 10-speed transmissions with splitter (version III of my all 10-speeders). Like Scania’s GS771 transmission original setup has swapped 8th and 9th gear to get halved gear steps in gear pairs 7-8, 8-9 and 9-10. Construction of this lego transmission is a little bit large and complicated, but gear steps are good. Gear steps vary only between 1,35-1,38 and halved gear steps are all 1,17. I didn’t know Scania’s ratio set when I designed this setup but lego version’s ratios are surprisingly close to Scania’s GS771. Check picture Ratio comparison. Alternative setup is based on earlier Scania’s GS770 gearbox. Only difference between these Scania’s transmissions is that in GS770 main gearbox’s 4th gear is slower. But this makes transmission’s behavior different because 8th and 9th gear have almost same ratio so GS770 is more like 9-speed transmission. For more info about this feature is in chapter M.3. These old lego designs are not very optimized, for lego builders I recommend to check next version II original and alternative setup. M.2. Version II:
Here is version II original and alternative setup of my 10-speed transmissions with splitter (version IX of my all 10-speeders). These setups are re-investigated designs from setups of version I. New designs are more compact but ratio sets are unchanged while they are pretty realistic already in version I. You can check differences from picture Ratio comparison. There are only minor changes between original and alternative setup so they reflect better Scania’s modular designs of GS770 and GS771. Again, original setup (GS771 inspired) has swapped 8th and 9th gear to get halved gear steps in high speed driving (gear pairs 7-8, 8-9 and 9-10). And alternative setup (GS770 inspired) has almost identical ratios in 8th and 9th gear so it’s more like 9-speed transmission. Check idea of this advanced “9-speed” design from next chapter. These version II setups are lego builder friendly designs. They both contain new 28 teeth gear wheel (ML, medium large in my notations). If you don’t have this new gear wheel you can copy front axles before synchro axles from version I setups and add them to version II setups. M.3. More about Scania’s splitter-type transmissions: GS770 and GS771 are older Scania’s 10-speed splitter-type transmissions for light and medium duty trucks. They contain 5-speed main gearbox with reverse gear plus splitter unit which is planetary gear design. Only difference between GS770 and GS771 is different ratio in main gearbox’s 4th gear. Neither has basic geometrical gear steps so here is more about designs and why they are done so. In GS770 main gearbox’s 4th and 5th gear have almost same gear step as splitter so 8th and 9th gear have almost identical ratios. Shifting sequence in high speeds is ...-6-7-9-10 or ...-6-7-8-10, so you never shift between 8th and 9th gear. So this transmission more like 9-speed design. This design may look weird but but there is a clever idea behind it: At highway speeds you drive in 10th gear which means splitter high. So if you have to slow down or engine rpm drops due to uphill situation you can make easy splitter shift from 10th to 9th gear. This procedure is common to all truck transmissions with splitter. But in slower speed limits when you have to drive in 9th gear you have splitter in low position so there is no easy splitter shift in slow downs and you have to shift with main gearbox. But in Scania’s GS770 you don’t drive with 9th gear in this situation but choose 8th gear with almost same ratio. So you are again in splitter high so you can do easy splitter shift from 8th to 7th gear for small slow downs. This is why 8th and 9th gear have almost same ratio, to give more easy splitter shifts in high speeds. In GS771 main gearbox’s 4th and 5th gear have smaller step than splitter and this causes 8th and 9th gear to swap in shift pattern. This swap makes halved gear steps in high speed driving meaning shifts 7-8, 8-9 and 9-10. So you still have two high split gears (9th and 10th) in high speeds giving easy splitter shifts for little slow downs. But you have also three halved steps with better performance when needed. Usually you can do basic splitter shift 7-9 and use halved step 9-10 only so typical upshifting sequence with some gear skipping is (1)-3-5-6-7-9-10. All in all these halved gear steps make GS771 more versatile so that’s why it finally replaced GS770. Together with these splitter-type transmission Scania had 10-speed transmission with range-change unit (like GR871) for medium and heavy duty trucks. Range-type transmissions had larger overall gear ratio giving better move-off and climbing capability. Lego version of GR871 is introduced in chapter I.4. 10-speed version IV. N. Twin Stick Transmissions: Inspirer: old Spicer transmissions Here are my 5x4, 4x4 and 5x3 twin stick transmissions. Also my Lego 4WD vehicle version 8 had twin stick transmission, it’s located on page Vehicles. N.1. 5x4 version A & B, overall gear ratio 15,43: 5-speed main + 4-speed aux
This one is a good old fashioned twin stick truck transmission. It has 5-speed main gearbox and 4-speed auxiliary gearbox, which is used as a 3-speed splitter. Altogether, the number of gears you’ve got is 5x3+1=16.
Links above belong to version A which is the original version with brick frame. Below is version B which has studless frame. Axles, their positions and gear pairs are same in both versions, so ratios and gear steps are also same. Version B is not so colorful as version A so download LDraw file if you can’t figure out structure from next pics. Some notes: Lego version’s gear steps 1,17-1,20 are typical for twin stick transmission but steps 1,26 are slightly too large. And auxiliary has basic shift pattern while in real twin stick transmission gears 3 and 4 are always swapped. N.2. 4x4, overall gear ratio 13,13 REMAKE: 4-speed main + 4-speed aux Inspirer: Spicer 8041-A & 8341-G
Here is another type of twin stick transmission. This time main gearbox has only 4 speeds. 4-speed auxiliary is used as 3-speed splitter like in previous 5x4 transmission so the number of gears you’ve got is 4x3+1=13. Available is both inline and parallel setups so depending on lego truck’s design builders can choose between long and narrow setup and short and wide setup, ratio sets are identical. These twin stick 4x4 setups are remakes with more realistic ratio set and shift patterns including swapped 3rd and 4th gear in auxiliary. In these remakes inspirer is real Spicer’s main gearbox and auxiliary combination, you can check differences between lego version and real transmission from picture Ratio comparison. Original lego setups had some reality issues while some gear steps and further overall gear ratio were too large for old twin stick transmission. Twin stick transmissions need small gear steps while in old trucks usable engine rpm range was very narrow. And lego auxiliary’s shift pattern didn’t have that gear swap. If you want to check old version it’s still available on page Junkyard. N.3. 5x3, overall gear ratio 12,60: 5-speed main + 3-speed aux
This twin stick 5x3 transmission is easier to use than previous versions with 4-speed auxiliary. Now auxiliary’s all 3 gears are used to split main gearbox’s gears so number of gears is 15. Compared to 5x4 this 5x3 has about same gear steps but one gear less means smaller overall gear ratio. Also this transmission doesn’t have same versatility given by 5x4’s extra gears and overlapping ratios.
This lego version has swapped gears in auxiliary’s shift pattern like real twin stick transmissions. Gear steps 1,17-1,20 are realistic but steps 1,29 are too large. For alternative ratio set you can use auxiliary of next 5x4 version II without its 1st gear. N.4. 5x4 version II, overall gear ratio 18,00: 5-speed main + 4-speed aux Inspirer: Spicer 8052 & 8341-F
This 5x4 version II is updated design of earlier 5x4 twin stick transmission. Main gearbox is pretty much the same but auxiliary is more realistic: it has swapped 3rd and 4th gear in shift pattern and it gives better ratios and gear steps. 5-speed main gearbox covers whole speed range so it has large gear steps. When needed main gears can be splitted with auxiliary’s gears 2-4. Auxiliary’s 1st gear is used with 1st main gear and it’s for low speeds or move offs in difficult conditions. So number of gears is 5x3+1=16 but pro user can take advantage of extra gears by using auxiliary’s 1st with main gears 2-5.
This time inspirer is specified combination of Spicer’s main gearboxes and auxiliaries. Lego version follows ratios and gear steps quite closely with two exceptions: gear steps 1-2 and 3-4 (1,80) in main gearbox are too large because of simple lego design. These exceptions make lego version’s overall gear ratio much larger than Spicer’s one. You can check differences from picture Ratio comparison. This transmission has underdrive sister design in my Lego 4WD vehicle version 8, it can be found on page Vehicles. Lego 4WD vehicle is rear engine design but you can check the idea of underdrive auxiliary if you need higher total ratios for high speed lego motor. Gear steps and overall gear ratio are identical in these lego sisters. N.5. More about twin stick transmissions:
Twin Stick Transmission means that driver has two shift levers without help of preselector gearboxes (splitter or range-change unit). First driver shifts only auxiliary gearbox in upshifting procedure. When auxiliary gearbox reaches top gear, it’s time to make a compound shift. This means that main gearbox must be shifted up one gear, but auxiliary gearbox must be shifted down from 4th to 2nd gear (in 4-speed auxiliary) before the whole transmission is in desired gear. And then, only auxiliary gearbox is needed to make next upshifts. When auxiliary gearbox has reached top gear again, it’s time to repeat the compound shift. This is repeated until you reach top gear in both gearboxes. Notable thing is that two top gears are always swapped in auxiliary’s shift pattern. I haven’t copied this feature to all my lego twin stick transmissions. This swap comes from overdrive gearbox. In direct drive gearbox gear pairs are located so that frontest is direct top gear (input and output shafts connected together), then in decreasing order other gears until rearest is 1st gear and then possible reverse gear. For example in direct drive 5+R-speed main gearbox it goes like this in downshifting procedure: In shift pattern’s right gate shift lever movement to rear moves shifting linkage forward to top gear and lever’s move to forward gives linkage movement to rearward to first underdrive gear, and this gives gear pair 5-4. Then in middle gate same moves give gear pair 3-2 and in left gate gear pair 1-R. So there is nice harmony in shift pattern and inside gearbox from front to rear. But in overdrive gearbox direct gear is still frontest and after it is gear pair of overdrive top gear and this ruins the harmony: In overdrive 4-speed auxiliary right gate’s shift lever movement to rear connects direct 3rd gear from front and lever’s move to front gives overdrive 4th gear from rear. So there is swapped gear pair 3-4 (not 4-3) in right gate while left gate gives normal gear pair 2-1. If you want to normal H shift pattern to overdrive gearbox right gate needs extra reversing lever in shifting linkage to eliminate gear swap. Nowadays they always eliminate this gear swap but in older transmissions like twin stick auxiliaries this swap is reality. There are two reasons for that extra 1st gear in 4-speed auxiliary: Firstly you get slower starting gear and a little bit larger overall gear ratio. Secondly you can have more downshifts without main gearbox shifting for example from 3-2 (main-aux) to 3-1 instead of 2-4. The latter compound shift is not normally used in uphill situations but direct downshift to 2-2 because driving speed drops too much in compound shift before you are back in gear. There can be alternative ratio setup in auxiliary so that 1st and 2nd gear has very large gear step. This gives two slow gears (1-1 and 2-1) before gear 1-2. It also means that auxiliary’s 1st gear can’t be used in downshiftings. So this setup is usually together with smaller gear step between main gearbox’s 4th and 5th gear. Then you shift after gear 4-4 direct to 5-3 without 5-2 (or direct to 5-4 without 5-2 and 5-3) so these overlapping gears give versatility to shifting in high speeds. Twin stick transmission with 3-speed auxiliary is simpler to use because it doesn’t have extra gears: in compound shift main gearbox is shifted up one gear but auxiliary is shifted down from 3rd to 1st gear. But remember that also 3-speed auxiliary is overdrive design so it has gear swap between two top gears. Too complicated? Check out next YouTube clips. Maybe it helps... or not. I needed several repeats before I understood what really happened in these clips. :-)
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