|
|
|
Ari Holopainen / tractor | |
| S. Tractor Transmissions Part I: Here is first part of tractor transmissions. In notation for example 8+4R means that transmission has 8 forward and 4 reverse gears. Transmissions can be arranged many different ways so for example 12 forward gears can mean 3 main gears with 4 ranges, 4 main gears with 3 ranges or 6 main gears with 2 ranges. And reverse gear can be integrated in main gearbox, range unit or splitter, or there can be separate driving direction changer which is called shuttle in real world. In real tractors they don’t usually give transmission ratios but example driving speeds with certain engine rpm and tyre size. In this case gear step = speed upper gear / speed lower gear. In lego tractors idea is that in long and narrow inline setups you hide motor and front part of the transmission into tractor’s engine bay and only rear parts are between rear tires under or inside cabin. And in short and wide parallel setups you put wide part of the transmission between rear tires under or inside cabin. Some tractor transmissions have powershift which can be shifted under load by push of a button without cutting the torque in drive line. Real tractors’ powershift is not possible with legos, lego powershift needs two or more identical motors and at least one planetary gear so in some cases I have used splitter instead. These lego “splitters” are representing powershifts’ small speed changes instead of main gearbox shifting. Some real tractors have mechanical splitters for more accurate working speed control but these are not designed for splitting all main gears in upshifting procedure like truck splitters. More info about powershift is in chapter S.1. 8+4R-speed & 16+8R-speed. I have designed also sequential tractor transmissions which are located in chapter R. Sequential Transmissions. It’s worth to check also B.7. 15+6R-speed planetary gear set for tractor (theoretical only) and C.9. 9+9R-speed full powershift tractor transmission (usable) in page Planetary gears. S.1. 8+4R-speed & 16+8R-speed , overall gear ratios 11,43 & 14,29: 8+4R: main gearbox + range 16+8R: powershift + main gearbox + range Inspirer: Ford 6610 Dual-range & Dual Power (TractorData)
I met this kind of 8+4R-speed transmission in my teenage years when I drove shortly one Ford tractor (I don’t remember model number any more). This tractor was rear wheel drive and its top speed was 30 km/h. It had 4-speed main gearbox without a reverse gear plus range unit with ranges high, low and reverse. So altogether you’ve got 4 slow and 4 fast gears in forward plus 4 slow gears in reverse. This kind of transmission is ideal when you have to drive slow and change often driving direction. The idea is to choose suitable gear in main gearbox and then use only auxiliary. On the other hand this kind of transmission isn’t good at high speed driving although you can move off as high gear as 7th if you are unloaded and slide the clutch a little. When you have driven with 8th gear and need to reverse you simply choose gear R4 with auxiliary shift lever. But to drive forward fast again you have to shift with the both sticks to get 5th, 6th or 7th gear, which are suitable gears to move off.
Here is shown only 8+4R-speed alternative setup II (alter2) with redesigned auxiliary. Original inline setup and alternative parallel setup are moved to page Junkyard because I designed those earlier setups before finding typical ratios of 8+4R-speed transmission. So step between low and high range was too large and reverse gears were too slow. Alternative setup II has more realistic auxiliary ratios. Modification also makes transmission slightly simpler and more compact than original setup. Range unit can be also equipped with faster low and reverse range without losing reality. This alternative ratio set is used in next 16+8R-speed.
This 16+8R-speed is otherwise like 8+4R-speed transmission but like Ford’s transmission it’s equipped with additional 2-speed powershift. This doubles the number of gears and allows shifting between Hi and Lo under full throttle.
This 16+8R-speed lego design is remake with two improvements: splitter is replaced with lego powershift and too slow reverse ratios in range unit are changed to more realistic. So after update old original inline and alternative parallel setups are moved to page Junkyard if you want to check them. Lego powershift is done by two identical motors and planetary gear version II with basic ratio 4,00. You get powershift stage low by running only motor 1 (M1) while motor 2 (M2) is stopped, this gives ratio 1,33. In stage high both motors are run in same direction to get direct ratio 1,00. More info about this lego powershift is in chapter B.9. 2-speed powershift for tractor on page Planetary gears. There is also a cousin 8+4R-speed transmission in E. Flat Gearbox Designs, page Basic & special designs. All in all Ford is not the only manufacturer that has 8+4R-speed transmission, also Valmet/Valtra and John Deere have their own versions. 8+4R-speed is basic transmission which can be enlarged with powershift, mechanical splitter or creeper unit. It depends on manufacturers which enlargements are available. This 16+8R-speed is inspired by Ford’s powershift transmission and later shown 16+8R-speed & 12+8R-speed by Valmet’s versions with mechanical splitter or creeper unit. What is powershift? Powershift is gearbox which can be shifted with button under load without cutting the torque in drive line and without need to press clutch pedal. Powershift is close to splitter while both have small gear steps and are used by buttons but their use is completely different: splitter is preselected and allows to split all main gearbox’s gears but powershift shifts instantly and is normally used only once during upshifting procedure. Typically you move off with powershift in low but drive powershift in high. So if you have to slow down or engine rpm drops because of high load you can quickly downshift under full throttle with powershift to get more torque and engine rpm back in working range. When situation is over you shift back to high and get more speed. Powershift is handy for example in ploughing when driving resistance is so high that normal shifting with main gearbox ends to tractor’s complete stop before you get a new gear. Powershift is not designed for this but if you want to split main gearbox’s gears with powershift, for example shift from 5H to 6L, it is possible so that you downshift with powershift when clutch pedal is pressed down for main gearbox’s upshifting. But in many tractors powershift’s gear step is more than half of main gear steps so powershift splits gears too unequal and this maneuver is not practical. But there are also tractor transmissions in which powershift gives halved steps so this powershift splitting is in theory possible. While powershift can shift without cutting the torque in drive line it can’t be constantmesh or synchromesh gearbox. Normally powershift’s gear coupling is done by multiplate wet clutches and pressurised oil which means poorer efficiency than in constantmesh or synchromesh gearbox. That’s why tractors usually have only few powershift gears together with constantmesh or synchromesh main gearbox and range unit. Although real powershift gearbox is not possible with legos you can build lego 2- or 3-speed powershift that uses 2 identical motors and a planetary gear. Check for example C.7. 3-speed powershift for tractor version II on page Planetary gears for more information. If you use 3 motors and 2 planetary gears you can build simpler 5-speed powershift or complete 9+9R-speed powershift transmission. Check C.8. 5-speed powershift for tractor and C.9. 9+9R-speed full powershift tractor transmission in same link. S.2. 8+2R-speed & 16+4R-speed, overall gear ratios 10,50 & 13,99: 8+2R: range + main gearbox 16+4R: powershift + range + main gearbox Inspirer: Ford 6610 Dual-range & Dual Power (TractorData)
This basic 8+2R-speed tractor transmission (8-speed tractor version II) has 4-speed main gearbox with reverse gear and 2-speed range unit. 16+4R-speed version has additional 2-speed powershift which doubles the number of gears and allows shifting between Hi and Lo under full throttle.
When you look lego design and ratios you can see that design is not the simplest, gear steps vary very much and shift pattern is not standard. Well, this is on purpose while ratios and shift pattern are copied from real Ford’s transmissions. Here is my guess, why gear steps vary so much in Ford’s transmissions: Gears 1st and 2nd are for low speed operating, then there is larger step 2-3 to squeeze four gears (3-6) into typical field working speeds 4-12 km/h. Then there is again larger step 6-7 (same as step 2-3 due to range unit) before transportation gears 7th and 8th. This time larger step ensures that you reach allowed top speed 30 km/h with 8th gear. So, it’s possible that large varying in gear steps is on purpose, not because of bad designing.
16+4R-speed version (16-speed tractor version V) has same Hi-Lo powershift as previous 16+8R-speed transmission. You get powershift stage low by running only motor 1 (M1) while motor 2 (M2) is stopped, this gives ratio 1,33. In stage high both motors are run in same direction to get direct ratio 1,00. More info about this lego powershift is in chapter B.9. 2-speed powershift for tractor on page Planetary gears. So, these 8+2R-speed and 16+4R-speed are complex lego designs while they copy ratios and shift pattern from real Ford’s transmissions. If you need more basic lego design with good geometrical gear steps you can build next main gearbox and range unit combination from page Basic & special designs: A.3. Range-change unit, gear step 4,00 & B.6. 4+R-speed synchromesh gearbox, overall gear ratio 3,00. They give usable 8+2R-speed design which can enlarged to 16+4R-speed with this same Hi-Lo powershift. S.3. 16+8R-speed & 12+8R-speed, overall gear ratios 12,86 & 42,86: 16+8R: splitter + main gearbox + range 12+8R: creeper + main gearbox + range Inspirer: Valmet 900 (TractorData)
These two tractor transmissions are based on 8+4R-speed transmission which has 4 main gears together with ranges high, low and reverse. Also Valmet (nowadays Valtra) has had this kind of transmission and they offered two optional equipment: either mechanical splitter or creeper unit but not both. Splitter doubles the number of gears to 16+8R-speed, halves the gear steps and it’s for more accurate working speed control (not practical to split gears in upshifting procedure). Creeper unit enlarges overall gear ratio and gives four extra slow gears in both driving directions so you got 12+8R-speed design. Creeper unit can be switched on with ranges low and reverse. In lego versions 16+8R-speed is new design (16+8R-speed version II, 16-speed tractor version IV) but 12+8R-speed (12-speed tractor version III) is remake. Original 12+8R-speed designs (original inline & alternative parallel setup) are moved to page Junkyard and they are junked due to too slow reverse gears and badly placed creeper shift levers. New 16+8R-speed and 12+8R-speed are based on same lego 8+4R-speed transmission which is S.1. 8+4R-speed with alternative ratio set in range unit. But adding splitter or creeper unit makes these two very different kind of transmissions: 16+8R-speed gives small steps and 12+8R-speed extra slow speeds. So depending on your lego tractor you can choose which enlargement to use, or you can use basic 8+4R-speed. These 16+8R-speed and 12+8R-speed transmissions have also cousin designs with slightly different range ratios in section E. Flat Gearbox Designs on page Basic & special designs. S.4. 18+6R-speed, overall gear ratio 22,68: 3-speed main gearbox + splitter + 3-speed range Inspirer: Massey Ferguson 4270 Speedshift
This inspirer has 3-speed main gearbox with a reverse gear, 3-speed range unit (ranges A, B and C) and Hi-Lo powershift. Altogether you have 18 forward gears and 6 reverse gears. In lego version powershift is replaced with splitter. If you need more information about powershift check earlier 16+8R-speed tractor transmission.
This time both real transmission’s powershift and lego version’s splitter split main gearbox’s gears equally, so you can split gears like in truck transmission if you need halved gear steps. But actually Massey Ferguson’s powershift is for slower move off gear before powershifting to higher driving gear in high driving resistance working like ploughing. Lego version’s splitter can be used to same small speed changes without powershift, other use is more accurate working speed control than without splitter. It’s also possible to add lego motor on splitter’s shift lever axle. This way you can get remotely button shifted splitter which is a little bit closer to real world’s powershift than manual lego splitter. One interesting thing is that Massey Ferguson’s range change is integrated to main gearbox’s H shift pattern. So if you drive for example in B range’s top gear and need to change range, you shift main gearbox to neutral, move shift lever to right for range selection, push forward to change to C range and then move back left to shift to main gearbox’s first gear. With this system you avoid difficult two stick shift. Lego version is not so handy so you have to shift both range’s and main gearbox’s shift levers to make simiral shift. But this is not a problem in lego world while you stop for shifting if you don’t have remote controlled gearboxes. I found also a building mistake: topmost axle in splitter and range unit has 3 support points which is too many (2 support points is enough). So if you build this transmission, forget the middle support point or use universal joint. In modified building example this error is corrected. S.5. 6+2R-speed & 12+4R-speed, overall gear ratios 12,00 & 16,00: 6+2R: range + main gearbox 12+4R: powershift + range + main gearbox Inspirer: Massey Ferguson 150 (TractorData)
These two transmissions are inspired by old Massey Ferguson 150. 6+2R-speed has 3-speed main gearbox with reverse gear plus 2-speed range unit. 12+4R-speed has same gearboxes but also 2-speed powershift which allows shiftings between Hi and Lo under load without cutting torque in drive line.
Lego powershift is done with two motors and a planetary gear. You get powershift stage low by running only motor 1 (M1) while motor 2 (M2) is stopped, this gives ratio 1,33. In powershift high you run both motors in same direction to get direct ratio 1,00. More info about this lego powershift is in chapter B.9. 2-speed powershift for tractor on page Planetary gears. For shift levers use three longitudinal bricks. Use six studs axle for main shift lever and put bush to right side of the left brick. Put middle brick between main gearbox and range unit, it’s main shift lever’s right support. Use right brick and axle pin to support range shift lever. This design is enough to prevent main shifter axle to slide to left or right. These transmissions use very basic lego ratios so main gearbox and range unit have very compact parallel design. So if you have lack of space to add gearbox it’s worth to test these two transmissions, especially basic 6+2R-speed version. If you need small tractor transmission but don’t have transmission driving rings I recommend to check 6+3R-speed tractor in section R. Sequential Transmissions. S.6. 12+12R-speed, overall gear ratio 13,89: 2-speed range + shuttle + 6-speed main gearbox Inspirer: Massey Ferguson 4608
This tractor transmission has 6-speed main gearbox, 2-speed range unit and driving direction changer which is called shuttle in real world. Altogether you’ve got 12 forward gears and 12 reverse gears, which means that you can drive rearward as fast as forward if you have the guts.
This lego design is remake which is more compact and more realistic three-range design with better ratio set than original design. In original lego design range unit and driving direction changer are combined to one auxiliary. Original design is moved to page Junkyard due to better remake but actually it’s not bad design at all. All in all this remake is quite basic lego design but still realistic tractor transmission. Massey Ferguson’s driving direction changer is a power shuttle, which means that in low speeds you can change driving direction simply moving changer’s shift lever, no stopping nor clutch pedal is needed during operation. In lego transmission driving direction changer is more like mechanical shuttle with synchro shifts. Actually it’s not needed while lego motor works in both directions but this way you get more realistic transmission to your lego tractor. Also Valtra A series has 12+12R-speed transmission that has 6 main gears with 2 ranges. S.7. 12+12R-speed version II, overall gear ratio 21,00: 4-speed main gearbox + shuttle + 3-speed range Inspirer: AGCO Allis 6690 (TractorData)
This 12-speed tractor transmission version II has 4-speed main gearbox, driving direction changer (shuttle) and 3-speed range unit (ranges A, B and C). Altogether you’ve got 12 gears in both driving directions. Driving direction changer is not necessary in lego world but it fitted perfectly between main gearbox and range unit: sliding axle solution of range unit needs anyway some space in front it.
One notable thing is that lego version’s overdrive main gearbox is not very practical in tractor use because slow speeds and large tires require large ratio in final drive. Problem is that I don’t know other way to make gear step 1,33 than overdrive gearbox. I found later how to make gear step 1,31 that makes not an overdrive gearbox but it was too late for this transmission. And I have found out that they use overdrive gearboxes also in tractor transmissions together with high reduction planetary gears in final drives. So lego design ain’t so bad design after all. Note that bush in the end of output axle is not in good place, 24 teeth crown gear will hit it when you slide the axle. Better place is at the front end next to two 24 teeth gears. I’m too lazy to fix the LDraw file and pics. In modified Building example this problem is fixed. In real world this kind of 4x3-structure is simpler, shorter and older (my guess) than 6x2-construction. 4x3 needs 7 gear pairs when driving direction changer is not included while 6x2 needs 8 gear pairs. Lego version is not shorter but thinner because more gears in main gearbox would increase its width not length. Also 3-speed sliding axle range unit needs more longitudinal space than 6x2-version’s auxiliary. When I have investigated tractor brochures I have found out that this 4x3-structure 12+12R-speed can be quite common design. This lego version is inspired by AGCO Allis but for example Ford and Massey Ferguson also have this kind of design. Probably also Valtra has their own version while 36+36R-speed powershift transmission has 4 main gears with 3 ranges. S.8. 16+16R-speed, overall gear ratio 14,00: 4-speed main gearbox + shuttle + 4-speed range Inspirer: John Deere 6430 PowrReverser (TractorData)
This tractor transmission has 4-speed main gearbox, driving direction changer (shuttle) and 4-speed range unit (ranges A, B, C and D). Altogether you have 16 gears in both driving directions.
Range steps are relatively small so ranges overlap each other, especially ranges B and C. Major idea in this overlapping is that you get large variety of gears for field working speeds with small steps. But choosing right gear is not always easy while sequential gears are often in different ranges. Check Ratios sorted in picture Ratios. These small steps are only for working speed control, not for upshifting procedure. But small range steps allow you to change range while driving without main gearbox shifting. This way you can avoid difficult two stick shift. For example in heavy loaded transport situation John Deere recommends upshifting sequence (A1)-(B1)-C1-D1-D2-D3-D4. This lego design is remake in which range steps A-B and C-D are 2,00 and step B-C is only 1,50. In original design all range steps are 2,00 while I didn’t first realize how clever John Deere’s 16+16R-speed transmission is. So after modification I got simpler and more compact range unit with more realistic ratio set. Original lego design is still available on page Junkyard if you want to check it. Although this transmission and earlier 12+12R-speed transmission version II are inspired by different tractors, main gearbox’s ratios of 12-speed transmission fitted perfectly to this 16-speed transmission. So this transmission’s main gearbox and driving direction changer are taken directly from 12-speed transmission, the only new part is 4-speed range unit. It reduced a lot LDraw file design time. On the other hand main gearbox is again overdrive version which is not so practical in tractor use. In this remake shift levers are located quite front close to each other. Idea is that you hide shift levers inside tractor’s engine bay and pop the hood for shifting. So this time you can build realistic cabin above range unit’s axles. S.9. 16+16R-speed version II, overall gear ratio 13,78: Shuttle + 4-speed range + 4-speed main gearbox Inspirer: John Deere 6430 PowrReverser (TractorData)
Also this 16+16R-speed tractor transmission version II (16-speed tractor version III) has 4-speed main gearbox, 4-speed range unit (ranges A-D) and driving direction changer alias shuttle. Unlike previous version I this transmission has synchro range unit, sliding axle driving direction changer and direct drive main gearbox. So this one is more like next 12+4R-speed and its upgraded version 21+7R-speed. Available is two alternative setups, short but wide parallel setup alter and long but narrow inline setup alter2, and both have double bevel type gear wheel in driving direction changer for easier use. For shift lever axles in parallel setup put longitudinal brick with holes also between main gearbox and range unit and axles only half studs inside middle brick. Like in previous 16+16R-speed ranges overlap each other, and range step B-C is smaller than others. Idea is copied from John Deere’s transmission and is to get more gears for field working speeds (4-12 km/h). When you sort gear ratios you can see that there are good small gear steps in middle gears so you can get right speed for every working situation. But choosing right gear is not so easy while most of the sequential gears are in different ranges, check table Ratios sorted in picture Ratios. These small steps are for working speed control and you are not supposed to use all these gears in upshifting procedure, two stick shifts are just too complex. John Deere’s recommended upshifting sequence from stop to full speed is (A1)-(B1)-C1-D1-D2-D3-D4. Because range steps are larger than steps of main gearbox you upshift between ranges first. But you can always keep things simple so that you choose first suitable speed range with range unit and then use only main gearbox and driving direction changer. Changing between forward and reverse is these lego designs’ weak point while driving direction changers are sliding axle versions. Especially original setup has problematic XS(8)-S(16) spur gear design so due to bad usability it’s moved to page Junkyard if you want to check it. Alternative setups are a little bit easier to use while they have Su(12) double bevel type gear on the sliding axle. When main gearbox and range unit are synchro versions 3rd synchro gearbox would be too much because of the backlash problems. So I guess that those who will build this transmission will use motor to change driving direction. S.10. 12+4R-speed & 21+7R-speed, overall gear ratios 10,50 & 63,00: 12+4R: 4-speed range + 3-speed main gearbox 21+7R: creeper + 4-speed range + 3-speed main gearbox Inspirer: John Deere 6420 SyncroPlus (TractorData)
This 12+4R-speed tractor transmission is a little brother of previous 16+16R-speed transmission version II. Both have 4-speed range unit (ranges A-D) but 4-speed main gearbox and driving direction changer are now replaced with 3-speed main gearbox that has also a reverse gear. While this transmission has only 2 gearboxes which have only 4 positions in shift patterns this transmission is quite compact structure. Note that right synchro axle of main gearbox has only 2 support points so it doesn’t go inside range unit’s rear support brick.
There is available also alternative setup in which main gearbox and range unit are located parallel. For shift lever axles use longitudinal brick with holes between gearboxes and put axles only half studs inside it. This brick comes very close to range unit’s 24 teeth gear but they shouldn’t hit each other. If hitting becomes a problem you have to test 24 teeth crown gear, move XS(8)-M(24) gear pair outside of the frame or use 9 studs long beam instead of brick. In these transmissions ranges B and C overlap each other but other ranges don’t although gear steps are very small between lower range’s top gear and higher range’s 1st gear. Overall gear ratio of one range is quite small but you can change range without main gearbox shifting while range steps are quite small too. In lego version steps A-B and C-D are 2,00 and while step B-C is only 1,50. Reason why range step B-C is smaller than the others comes from real world’s farm tractors and is to get more gears for speed range 4-12 km/h which is usual speed range for field working. If tractor’s top speed is about 30 km/h needed ratios are between 2,50-7,50. There is also available a sequential version of this transmission. Check 12+4R-speed tractor in R. Sequential Transmissions for more info. John Deere offers creeper unit as optional equipment for 12+4R-speed transmission. Creeper unit can be used with 3 lowest ranges giving creeper ranges LA, LB and LC. This gives 9 very slow speed gears in forward and 3 in reverse so altogether you get 21 forward and 7 reverse gears. So available is lego version of 21+7R-speed transmission, based on alternative setup of 12+4R-speed transmission.
S.11. 12+4R-speed & 24+8R-speed, overall gear ratios 8,93 & 10,71: 12+4R: main gearbox + range 24+8R: powershift + main gearbox + range John Deere 9400 Syncro & PowrSync (TractorData)
These two lego transmissions are inspired by John Deere 9400 monster tractor. 12+4R-speed transmission has 3-speed main gearbox with reverse gear together with 4-speed range unit (ranges A-D). 24+8R-speed has also additional Hi-Lo powershift which doubles the number of gears. In John Deere’s transmissions range D is not available in reverse so they are 12+3R-speed and 24+6R-speed designs.
This lego 12+4R-speed version II (12-speed tractor version VI) is new design in which ratios are close to John Deere 9400’s transmission. 24+8R-speed lego transmission is remake and now equipped with lego powershift. Old lego 24+8R-speed has only splitter instead of powershift and its ratios are based on different John Deere model that doesn’t have powershift as optional equipment. So old lego design is moved to page Junkyard if you want to check it. These transmissions are used so that range A is for lower field working speeds, ranges B and C are for higher field working speeds and range D is for transportation. Other ranges don’t overlap but ranges B and C overlap so heavily that they actually work like mechanical splitter: you get progressive speeds by gear order A1-A2-A3-B1-C1-B2-C2-B3-C3-D1-D2-D3. This gear order with halved gear steps helps to choose right speed for the most working situations but it’s too difficult to use in upshifting procedure. Additional powershift allows small speed changes by button shifts under heavy driving resistance without cutting torque in drive line. Idea is to move off in powershift stage low and drive in stage high. More info about real powershift is in chapter S.1. 8+4R-speed & 16+8R-speed. Lego powershift is done by two identical motors and a planetary gear (2-speed setup of C.7. 3-speed powershift for tractor version II on page Planetary gears). It works so that you get stage low by running forward only motor 2 (M2) while motor 1 (M1) is stopped. In stage high both motors are run forward. This lego transmission has reverse gears but you get both powershift stages also when you run motors in reverse. John Deere 9400 is a real monster tractor that has 4WD, large tyres and articulated steering. So in lego design my idea is that lego motor and additional powershift are located in tractor’s engine bay. Main gearbox is in cabin and after it there is a universal joint for articulated steering. Finally there is range unit located between rear tyres. It’s not modeled but then you can add enough speed reduction before differentials and another universal joint to get front wheel drive. For suspension front axle is supposed to be pendular design. There is also simple example for lego articulated steering: 40 teeth gear wheel is in the middle of the turning point and it’s connected rigid to rear frame. Steering wheel axle with 8 teeth gear is located to front frame.
|
|
Primary content in this document is © Ari Holopainen. All other text, images, or trademarks in this document are the intellectual property of their respective owners. |
| |
©2005 LUGNET. All rights reserved. - hosted by steinbruch.info GbR |
