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Found 5 results

  1. I finally took the time to write down the things I have come to understand with regard to LEGO 4-speed sequential gearboxes. I am receiving many questions about gearboxes and I hope these understandings can help you reason about a gearbox layout while you're building one or trying to design one. I hope this also answers a question I received from @nerdsforprez more than a year ago, which I did not answer yet. Gearbox layout Let's take a look at this 4-speed sequential gearbox layout. Black is input, red is output and orange is control. The main input is divided over a high input (black) with high input ratio and a low input (white) with low input ratio. The high input ratio is 1:1 (via a 12:12 mash) and the low input ratio is 1:2 (via a 8:16 mash). This makes for a combined ratio of (1:1) : (1:2) = 2:1 between the high and low inputs. I will refer to this ratio as the primary ratio. In fact this ratio is the ratio between the two driving rings. Both driving rings have a high output (green) with high output ratio and a low output (yellow) with low output ratio. For both driving rings, the high output ratio is 1:1 * 2:1 = 2:1 (via a 16:16 mash and a 16:8 mash) and the low output ratio is 5:3 * 1:2 = 5:6 (via a 20:12 mash and a 8:16 mash). This makes for a combined ratio of (2:1) : (5:6) = 12:5 between the high and low outputs of each driving ring. I will refer to these ratios as the secondary ratios. Rotary catch and quadrants Even though I will explain things in terms of the gearbox layout described above, the first understanding I want to address, applies to practically all 4-speed sequential gearboxes with 2 driving rings. Let's take a look at the rotary catch and driving rings from above and divide the layout into four quadrants. Each quadrant represents one of the four gears of the 4-speed gearbox. When we turn the rotary catch clockwise (seen from the left) with 90-degree steps, it will always make the following path through the four quadrants. From the path the rotary catch draws, we can see that it toggles from one driving ring to the other driving ring for every 90-degree step. So if we want to obtain a useful gear sequence (either a 1-2-3-4 sequence or a 4-3-2-1 sequence) along that path, we need to tie gears 1 and 3 to one driving ring and gears 2 and 4 to the other driving ring. Otherwise the rotary catch can never 'toggle' between subsequent gears. Now let's take a look at all distributions of the four gears over the four quadrants that meet this requirement. Starting top-left, this will produce a 1-4-3-2 sequence. Repeating the sequence will give 1-4-3-2-1-4-3-2-etc., which effectively boils down to a 4-3-2-1 sequence. Starting top-left, this will produce a 1-2-3-4 sequence. Starting top-left, this will produce a 3-4-1-2 sequence. Repeating the sequence will give 3-4-1-2-3-4-1-2-etc., which effectively boils down to a 1-2-3-4 sequence. Starting top-left, this will produce a 3-2-1-4 sequence. Repeating the sequence will give 3-2-1-4-3-2-1-4-etc., which effectively boils down to a 4-3-2-1 sequence. Starting top-left, this will produce a 2-3-4-1 sequence. Repeating the sequence will give 2-3-4-1-2-3-4-1-etc., which effectively boils down to a 1-2-3-4 sequence. Starting top-left, this will produce a 2-1-4-3 sequence. Repeating the sequence will give 2-1-4-3-2-1-4-3-etc., which effectively boils down to a 4-3-2-1 sequence. Starting top-left, this will produce a 4-3-2-1 sequence. Starting top-left, this will produce a 4-1-2-3 sequence. Repeating the sequence will give 4-1-2-3-4-1-2-3-etc., which effectively boils down to a 1-2-3-4 sequence. Surprisingly, every distribution that meets the requirement, will produce either a 1-2-3-4 sequence or a 4-3-2-1 sequence. What this tells us, is that it's enough to tie gears 1 and 3 to one driving ring and gears 2 and 4 to the other driving ring, to obtain a useful gear sequence. Nothing else matters! Primary ratio vs. secondary ratios The next understanding I want to address, concerns the relation between the primary ratio (the ratio between the high and low input) and the secondary ratios (the ratios between the high and low outputs of both driving rings). We have already seen that in the gearbox layout at hand, the high and low output ratios are the same for both driving rings. One thing we can say about 4-speed gearboxes in general, is that the ratios between gears 1 and 3 and between gears 2 and 4 need to make a bigger difference than the ratios between gear 1 and 2 and between 3 and 4. Now when we take into account that gears 1 and 3 need to be tied to one driving ring and gears 2 and 4 need to be tied to the other driving ring, and we use the same high and low output ratios for both driving rings, we can say that the secondary ratios, which constitute the ratios between gears 1 and 3 and between gears 2 and 4, need to be bigger than the primary ratio, which constitutes the ratios between gears 1 and 2 and between gears 3 and 4. The gearbox discussed in the beginning of this post has a primary ratio of 2:1 and secondary ratios of 12:5, so it meets the above requirement. Check! Swapping and reversing If we go back to the distributions we listed above, we can see that half of them generate a 1-2-3-4 sequence and half of them generate a 4-3-2-1 sequence. When we study them more thoroughly, we can see that all 1-2-3-4 distributions have a horizontally flipped counterpart with a 4-3-2-1 sequence. In other words, if we flip the distribution horizontally, we reverse the gear sequence. Example: Swapping 1-3 with 2-4 in a 4-3-2-1 sequence produces a 3-4-1-2 sequence. Repeating the sequence will give 3-4-1-2-3-4-1-2-etc., which effectively boils down to 1-2-3-4. Example: Swapping 1-3 with 4-2 in a 1-2-3-4 sequence produces a 4-3-2-1 sequence. What this tells us, is that when we mirror the gearbox layout left-to-right (top-down in the quadrants), which boils down to swapping the high and low inputs, the effect is that we reverse the gear sequence. Practical value: If you find yourself in a situation where you want to swap the upshifting and downshifting directions, simply swap the high and low inputs, like in the image above. Finally, if we take one more look at the gear distributions above, we can see that when we swap gears 1 and 3 or gears 2 and 4 in any distribution, we get a distribution with the reversed order. 1-2-3-4 will produce 4-3-2-1 and 4-3-2-1 will produce 1-2-3-4. When we swap both gears 1 and 3, and gears 2 and 4, we reverse the order twice and get again the same order. Example: Swapping 1 and 3 in a 1-2-3-4 sequence produces a 3-2-1-4 sequence. Repeating the sequence will produce 3-2-1-4-3-2-1-4, which effectively boils down to a 4-3-2-1 sequence. Example: Swapping 2 and 4 in a 1-2-3-4 sequence produces a 1-4-3-2 sequence. Repeating the sequence will produce 1-4-3-2-1-4-3-2, which effectively boils down to a 4-3-2-1 sequence. Example: Swapping 1 and 3, and 2 and 4 in a 1-2-3-4 sequence produces a 3-4-1-2 sequence. Repeating the sequence produces 3-4-1-2-3-4-1-2, which effectively boils down to a 1-2-3-4 sequence. What this tells us, is that when we mirror one side of the gearbox front-to-back (swap the high and low outputs of one driving ring), we will reverse the gear sequence. When we mirror both sides front-to-back (swap the high and low outputs of both driving rings), we won't affect the gear sequence. Practical value: If it's more convenient for the rest of your build to mirror your gearbox layout front-to-back, like in the image above, you can do so without any consequences. If it's more convenient to mirror only the left side or the right side of your gearbox layout, you need to also swap the upshifting and downshifting directions. If you want to inspect the gearbox used in this post in 3D, here it is in Stud.io format and here in LDD format.
  2. RC Off-roader with Dual Diagonal Drive I think I'm onto something that will get me through the winter. Summary Dual diagonal drive means: 1) dividing torque over two separate drive trains while 2) preserving the advantage of having open differentials when cornering and 3) passing diagonal tests without using differential locks. Background I have been playing with this idea for a while already, especially after seeing @KevinMoo's dual drive models (Mitsubishi Pajero and Dual-Driveshaft Pickup). @KevinMoo rightfully addressed the vulnerability of LEGO parts in RC models and the fact that using independent drive trains for the left and right sides, loses the benefit of differentials while cornering. This got me thinking. Using independent drive trains for left and right in a 4WD model does indeed drop the benefit of differentials while cornering, but what if we would pair the wheels diagonally, so pair the left front (LF) wheel with the right rear (RR) wheel, and pair the right front (RF) wheel with the left rear (LR) wheel? The resulting 'dual diagonal drive' (I borrowed the term from the electric skateboard scene) would serve two major benefits: While cornering, the LF and RR wheels will average to a speed that is very close to the average speed of the RF and LR wheels. So not having an open distribution by means of a differential between the two drive trains is much less of a problem as with separate drive trains for the left and right side wheels. On a very uneven surface, where one or two wheels may lose contact with the ground, the wheels that do have contact are typically lined up diagonally, see image. With dual diagonal drive, the vehicle would still have traction, even without locking any differentials. Only on slippery surfaces, there are chances of spinning wheels. So this is what I'm thinking of. We start with the basic dual diagonal drive setup: Two separate drive trains, one for the LF and RR wheels and one for the RF and LR wheels. The drive trains cross using two 24t gears and an auxiliary 16t gear that sits right underneath the auxiliary axle for the other drive train. So no clutch gears are involved in this crossing. I inserted a 1L Technic liftarm inside each differential - idea from @Madoca 1977's Toyota Land Cruiser 80 - to prevent the bevel gears from popping out. Next we add a manual locking feature, which closes the differentials with a single lever. This locking feature will force each pair of wheels involved in one of the drive trains to have equal speed. Now we connect each XL-motor to one of the differentials, using a small 4-speed gearbox. That means; two separate 4-speed gearboxes. This may be a bit ambitious, we'll have to see in real-life whether this is feasible or not. I might fall back to two 2-speed gearboxes. I did pay attention to the amount of torque in the transmission though. I geared up the XL-motor outputs and geared down the transmission output. That makes the transmission spin faster with less torque. The gearboxes are operated synchronously using a 90-degree stepper, which is controlled by a Servo-motor. Each gear shift axle has its own 90-degree limiter. And finally the outputs of the XL-motors are transferred to a fake V8-engine via a normal differential. The sole purpose of this differential is to combine the XL-motor outputs for the fake engine. For the steering I'm thinking of using a servo motor. I don't really like the directness of steering with a servo-motor, but the steering link attachment points are moved one stud backwards, which confines the steering angle. This adds to better handling and protects the CV-joints in the wheel hubs. I don't know where this is going to end. I'm not even sure about the exact kind of car I will be targeting, but it sure needs to be some kind of all-rounder. Comments and suggestions are welcome.
  3. Sequential AWD 4-speed gearbox with V8 fake engine Features - AWD with center differential - Sequential 4-speed gearbox - One-finger shifter - V8 fake engine This gearbox is an excerpt from my rugged supercar project. The mid-console has an important role in the overall stiffness of that model. It had to be narrow as well. If you build (have built) it, you will also notice it has very little torsional flex. I wanted a 4-speed sequential gearbox covering a wide range of ratios. So not something like 1:2.5 upto 1:1, but rather something like 1:3:5 upto 1:0.8. Another requirement I had, was that I didn't want red clutch gears to transfer drive on axles rotating at different RPM. This is a common practice, but from modding the Porsche I know it induces a lot of friction on the axles involved. When not engaged, red clutch gears better only make dummy rotations and not transfer drive. And finally, all had to fit underneath the engine; I didn't want the gearbox to be routed through the entire chassis. Instructions available on Rebrickable.com. Have fun!
  4. Video Found Here: Specifications: Number of Gears: 4 Gear Ratio Spread: 5:1 - 1:1 Shift Reliability: 99% Friction Level: Low Transmission Type: Dual-Sequential Synchronized? Yes Auto-stop? No Optimal Transmission Motor RPM: 15 - 40 Length: 10 studs Width: 11 studs Height: 5 studs (6 with optional support) Note on dimensions: dimensions are measure to the furthest protruding point of the transmission; that is to say, the transmission does not actually occupy all of the space designated above. Also, I know that the measurement for width is greater than that of length, (which is against their very definitions) but length was measured as being parallel to the drive axles. This is the transmission I used in my RHM Wutzwerg (http://www.eurobrick...opic=125571&hl=) supercar. It is a dual-sequential transmission, meaning that it is actually a pair of 2-speed transmissions (one with ratios of 3:1 and 1:1, the other with ratios of 1.67:1 and 1:1) which are shifted in sequence to produce 4 distinct, sequential speeds. It is very smooth and very reliable, the only potential concern being that it can slip under <b>extreme</b> stress situations; this can be remedied by added a gear reduction later in the drivetrain. It does also lack an auto-stop function, however I will be posting an appropriate stepper-motor shortly. Instructions are here: https://drive.google...XVFRGc. Before building, please read the following important notes: -Instructions are in *.lxf (LDD - Lego Digital Designer) format. Sorry, I am horrible with other Lego CAD programs. -Green marks the drive input, red marks the drive output, and purple/pink marks the transmission shifting input. -I do ask that if you use this in a model, you give me credit as the designer of the transmission. -Elastics have to be fastened like this: http://www.moc-pages.com/image_zoom.php?mocid=426942&id=/user_images/116595/1459193308m …so that the yellow part (orange in the instructions) is pulled on axis towards the shifting axle. -The yellow ribbed axle connectors in the instructions need to be replaced with the part below: http://www.moc-pages...595/1459193300m -Any questions, comments, or otherwise can be addressed to me in the comments and I will make an attempt to respond as quickly as possible. This thing won't accept pictures at the moment, so here's a full catalog of them: http://www.moc-pages.../moc.php/426942
  5. Link to MOCPages: http://www.moc-pages.../moc.php/426649 VIDEO FOUND HERE: Hello, this is my first post on Eurobricks. Anyway, here I present my custom supercar RHM (Rage Hobbit Motors) Wutzwerg. Note: this model is on Lego Ideas, the link for which is here: https://ideas.lego.com/projects/136011. I'm not really expecting the model to get either the necessary votes or to get turned into a set, but hey, I like to be surprised. Propulsion: 1 x L motor Steering: Front wheel with 1 x Servo motor and working steering wheel Drive Type: RWD Transmission: 4-speed sequential synchronized V2 Weight: 1.3 kg (2.87 lbs) Length: 41.5 cm (16.3 in, 52 studs) Width: 18 cm (7 in, 22.5 studs) Height: 10 cm (3.9 in, 12.5 studs) Power source: 7.4v 8878 Li-Po rechargeable battery box Estimated part count: 1800 pieces Suspension: All-wheel dual-wishbone independent Opening hood, doors, and engine V10 piston engine connected to drivetrain through transmission Build time: ~60 days Short Description This is my first vehicle to be built without a real subject vehicle in mind. It has less of a focus on performance than my other vehicles, with only a single L motor for propulsion. It also has front-wheel steering with a working steering wheel, a new version of my 4-speed sequential synchronized transmission (link here: http://www.moc-pages.../moc.php/422999), and a motorized rear wing. Introduction For this car I was trying something a little bit different. I had just designed a new version of my 4-speed sequential synchronized transmission (link here: http://www.moc-pages.../moc.php/422999) and I wanted to use it in a car, but I also wanted to build something a little less performance-oriented than usual and thus fit in more functions. This time, there is no original vehicle; make what comparisons you will, this car is entirely a product of my imagination. I think. Drive Train Part of my plan for this vehicle was to eliminate one of my customary 2 drive motors, leaving only a single L motor for propulsion. This freed up space for another M motor, as well as allowing room for the V10 piston engine. The V10 piston engine located behind the front seats, and was connected to the drive system through the transmission; as such, it varied with whatever gear the transmission was engaged into. Because of space restrictions, I had to replace the usual cylinder brackets with a custom rig, after spending a solid hour determining the exact geometry of the original brackets. The transmission used in this vehicle works off of the same principle as my previous 4-speed sequential synchronized transmission; this transmission is also a dual-sequential transmission. What this means is that the transmission actually contains TWO separate transmissions which are shifted in such a way as to produce 4 distinct speeds. What differentiated this transmission from the previous versions is that the switches were not hinged: instead, they moved back and forth in a straight line. This can be seen and understood better from the video above, and you can expect instructions sometime sort of soon-ish. The transmission itself was shifted by an M motor geared 10:1. Because of the lessened power from using a lone L motor, the motor had a gear reduction of 1.25:1 before being fed into the transmission, and then another reduction of 2:1 before the differential at the rear wheels. The car wasn’t fast, but it did pretty well for a single motor. Steering and Other Motorized Functions Steering was simple as usual - with a Servo motor and rack-and-pinion system - but this time I added a working steering wheel. That’s just about all there is to say for the steering system. The final M motor was for the rear wing. This was no fancy job, just a linear clutch and lever mechanism to raise the rear wing, but again space restrictions made the implementation of this system difficult. The rear aesthetics were somewhat compromised to make room for the rear wing & mechanism. Aesthetics With this being the first time I’ve ever come up with my own large-scale car, I didn’t really know where to start, and all the online comments saying “Making your own car is SO hard!” were not particularly encouraging. The front was actually the first area to be built (because of the awkward and inconvenient position of the battery box) and the rest of the car was built using the front as a reference point. Obviously, I can’t give my own unbiased opinion on the car’s aesthetics - many hours spent designing it have probably compromised my opinion as well - but I think the aesthetics turned out pretty well. Please, give me your honest opinions in the comments section! Reflections Not bad, I think, for a first attempt at making my own vehicle. Space was a little bit cramped because of the scale I chose to build it in, but everything mostly fit together in the end. It functioned really quite well: the transmission, rear wing, steering, and propulsion systems all worked without malfunctioning even once in the final vehicle, despite considerable use. That may be a first for me. Despite having fun crafting my own vehicle, I can’t see this as being something I’ll repeat frequently. That’s not to say I’ll never do it again, but I do enjoy recreating existing cars, and of course brand familiarity with my viewers gives people something to compare to. Enjoy the pictures!