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Ari Holopainen / truck | |
| A. 14-speed Transmissions: Here is ideas how to build a 14-speed transmission. It’s a three-stage truck transmission with main gearbox, splitter unit and range-change unit. Forward gears are: CL-CH-1L-1H-2L-2H-3L-3H-range_change-4L-4H-5L-5H-6L-6H, C means crawler gear, L and H are splitter’s low and high. 14-speed version I is taken from my rear-engined Lego 4WD vehicle and 14-speed version II truck setup of it. My best 14-speed designs with realistic ratios so far are version III and version IV. A.1. My first version, rear engine 4WD, overall gear ratio 31,25: Splitter + main gearbox + range Used in my Lego 4WD vehicle version 6 Inspirer: Volvo and Scania trucks
This 14-speed version I is designed for my Lego 4WD vehicle version 6 which has rear mounted engine. Unfortunately there are no pictures of Lego 4WD vehicle version 6 but you can check page Vehicles for versions 5 and 7. Splitter unit, main gearbox and range-change unit were modeled separately but now available whole transmission in one LDraw file.
Note: Overall gear ratio is a little bit too large, in heavy duty trucks it’s usually 15-20. So this 31,25 suits to severe duty trucks. Another notable thing is that gear steps vary too much, but luckily they vary in right direction so there is progression in gear steps. A.2. Version II, 4 reverse gears, overall gear ratio 31,25: Range + splitter + main gearbox Inspirer: Volvo and Scania trucks
This version is near to real truck transmission because of front-mounted engine and rear-wheel drive. This time main gearbox has also a reverse gear, which means 4 reverse gears altogether. Ratios and gear steps are identical to previous version.
Splitter’s and range-change unit’s shift levers are unfinished so if you need an example how to build them check YouTube building example in B.1. 12-speed transmission version I. A.3. Version III, 4 reverse gears, overall gear ratio 20,83: Main gearbox + range + splitter, also 12-speed conversion Inspirer: Scania GRS905
This 14-speed version III has good geometrical gear steps while steps vary only between 1,25-1,28. Crawler gear has larger gear step on purpose so gear step CH-1L is 1,33. Actually this doesn’t follow Scania’s transmission which has smaller crawler gear step. But lego version’s overall gear ratio is closer to typical heavy duty transmission’s 15-20. Shift pattern may look odd but it should be same as in real Scania. Idea is to make two groups: seldom used reverse and crawler gear group and more used road gear (1L-6H) group.
This design is remake which has more compact design and better placed shift levers. Original design is still available on page Junkyard if you want to check it. Scania’s GRS895 12-speed transmission is actually 14-speed transmission without crawler gears, there are no changes in ratios or gear steps. So here is how to get 12-speed lego conversion of this 14-speed transmission, it’s just removing crawler gear’s 16 teeth clutch gear. New overall gear ratio is only 12,50 so 12-speed version suits to linehaul trucks.
A.4. Version IV, 6 reverse gears, overall gear ratio 40,00: Splitter + range + main gearbox, also 12- & 13-speed conversions Inspirer: Volvo I-Shift with crawler gears
I-Shift is Volvo’s 12-speed automated transmission. As four options you can have one or two crawler gears with or without reverse crawler (for more info check link above). Here is described maximum choice 14-speed with 6 reverse gears. In I-Shift crawler gear is not in main gearbox but extra gear pair in front mounted splitter. In normal use I-Shift with crawler gears is same as basic 12-speed (2x3x2) but when needed crawler gear is chosen with main gearbox’s gears 1st, 2nd and reverse giving gears C1, C2 and RC. So crawler position overrides normal splitter. In normal crawler gear transmission crawler gear step CL-CH is as small as splitter step but in this Volvo’s design crawler gears have large steps: gear step C1-C2 is as large as main gearbox’s step 1-2, and also step C2-1L can be chosen larger than splitter step. While basic 12-speed I-Shift has overall gear ratio suitable for heavy hauling adding two large step crawler gears give this transmission very large overall gear ratio, so it’s severe duty transmission. Crawler position can be chosen also with high range reverse so you have 6 reverse gears altogether: RC, RL and RH in both ranges. All in all this transmission is a little bit complex to operate but driver doesn’t need to pay attention while transmission is automated.
Lego version is remake with more compact design and easier range shifts but scaled ratio set is unchanged. Original design is still available on page Junkyard if you want to check it. Lego version has very good geometrical gear steps: they vary only from range shift’s 1,27 and splitter shifts’ 1,28 to compound shifts’ 1,30. As described earlier gear steps of crawler gears are larger: gear step C1-C2 is 1,67 and C2-1L 1,50. There is still problematic spur gear pair XS(8)-S(16) in sliding axle splitter but I don’t know other way to get suitable crawler ratio together with splitter’s step 1,28. While this lego version is manual gearbox you need to pay more attention with splitter unit. In normal use only splitter’s positions high and low are used so operating is like basic 12-speed range-splitter transmission (2x3x2). For low speeds or high torque you choose splitter’s position crawler with main gearbox’s gears 1st, 2nd or reverse. Other note is that lego version doesn’t have standard H shift pattern but so called Y shift pattern. This is due to more compact main gearbox design. As conclusion about operating check carefully shift pattern in picture Ratios 14-speed, available crawler positions are marked as red. This lego version is underdrive design for high speed lego motor. If you need direct drive version for low speed motor you can use main gearbox’s right axle under synchro axles as output instead of left one. Then scaled ratios become real ratios while underdrive auxiliary ratios and overdrive main gearbox ratio cancel each other.
Like in Volvo’s I-Shift also lego version has 13-speed and 12-speed conversions. In 13-speed version crawler gear ratio is different and splitter’s crawler position is only used with main gearbox’s gears 1st and reverse. There are still 6 reverse gears but ratios are partly different. In 12-speed version crawler gear pair is removed which gives two studs shorter design. Now you have only 4 reverse gears. Modifications are done in auxiliaries while main gearbox is identical in all versions. Available is also sequential sister transmission if you don’t have transmission driving rings. Check R.17. 14-speed truck version II in R. Sequential Transmissions. For another severe duty transmission with extra slow crawler gears I recommend to check section G. 11-speed Transmissions inspired by Eaton Fuller 9ALL. B. 12-speed Transmissions, 4 reverse gears: These 12-speed transmissions contain 3-speed main gearbox with reverse gear plus range-change unit and splitter. So forward gears are 1L-1H-2L-2H-3L-3H-range_change-4L-4H-5L-5H-6L-6H in which L & H are splitter’s low and high. This kind of transmissions are quite common in trucking world: For example Mercedes, Scania and Volvo have their own designs. Also European trucks like DAF, Iveco, MAN and Renault can have 12-speed version of manual ZF Ecosplit, automated ZF AS Tronic or automated ZF TraXon. And American trucks can use 12-speed automated Eaton Endurant HD. In lego designs version I is universal design (although inspired by Volvo & Scania) with some progression in gear steps. Version II is inspired by Eaton Endurant and for lego American trucks. But these are not all possibilities. For lego Scania you can check 12-speed conversion of A.3. 14-speed version III and for Volvo’s I-Shift 12-speed conversion of A.4. 14-speed version IV. B.1. Version I, overall gear ratio 18,75: Range + splitter + main gearbox (original setup) Range + main gearbox + splitter (alternative setup) Inspirer: Volvo and Scania trucks
This 12-speed transmission version I (version II of my 12-speeders) is inspired by Volvo and Scania but it’s more like basic lego design without accurate ratio set. It has the same design as the earlier 14-speed transmission version II, but the crawler gear is replaced with a reverse gear. Overall gear ratio is now good but gear steps still vary quite a lot. Luckily they vary in right direction so gear steps are progressive-like. Actually progression gives quite useful ratio set for heavy duty purposes while gear step between two top gears is smaller and overall gear ratio larger than in transmission based on geometrical gear steps. For splitter’s and range-change unit’s finished shift levers check YouTube video Building example.
Available is also an alternative setup with several modifications: Splitter unit is synchromesh, overdrive and located parallel with main gearbox (left and middle transmission driving rings are for main gearbox and right one for splitter). Reverse gear is more compact but to get it I had to change slower ratio. These modifications haven’t changed gear steps or overall gear ratio so this is only alternative setup not new transmission. Main gearbox and splitter have interesting design while there is a shortcut from main gearbox’s input axle to splitter’s output axle via two clutch gears. This means that in splitter low gears 1L, 3L, 4L and 6L have less stages in power flow and better efficiency. For main gearbox’s shift lever use 6 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. All in all this alternative setup is quite simple and compact design for low speed motor so it’s good choice for lego truck builders. If you don’t like progression in gear steps and want geometrical gear steps instead check next B.2. 12-speed version II or 12-speed conversions of A.3. 14-speed version III and A.4. 14-speed version IV. Ratio set of this 12-speed version I has also sister designs in my lego vehicles: Project 5590 II (page Project 5590) has sequential version and Lego 4x2 truck (page Vehicles) synchro version as an optional transmission. Main gearboxes of this 12-speed version I can be used directly as 3+R-speed personal car transmission. On the other hand you can use main gearbox of P.17. Old 3-speed & transfer case version III (page Junkyard) together with splitters and range-change units of this chapter to get alternative 12-speed transmission. B.2. Version II, overall gear ratio 19,69: Main gearbox + splitter + range Inspirer: Eaton Endurant HD
This 12-speed version II (version V of my all 12-speeders) is inspired by Eaton Endurant HD, 12-speed automated transmission. Design is same 2x3x2 but ratio set has geometrical gear steps like Endurant HD. And ratio sets of lego version and Eaton Endurant HD are quite close to each other, check picture Ratio comparison.
Also this lego design has parallel mounted main gearbox and splitter which means that in some low split gears there is a shortcut in power flow between main gearbox and splitter via clutch gears. And to get shift levers for this parallel design check YouTube clip Building example, or description in previous version I with the difference that main gearbox and splitter are mirrored. Eaton’s 12-speed Endurant HD and 18-speed Endurant XD are sister transmissions with identical main gearbox and range-change unit. Only difference is that HD has 2-speed splitter with larger gear steps while XD’s splitter is 3-speed with smaller gear steps. Also this lego version has sister design: for 18-speed big sister check chapter E.3. 18-speed version III.
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