Hrafn

Thank you for this review. This will be the first new set I get in years - tons of functions and useful parts at a good price, and good looking if the stickers are left off.

Looking amazing! For the hatch, there is always the Technic ball joint (https://www.bricklink.com/v2/catalog/catalogitem.page?P=32474) and a connector like https://www.bricklink.com/v2/catalog/catalogitem.page?P=32174

This is an automatic drive-neutral-reverse gearbox. The input drives a rotary selector (via a clutch gear) so that drive is 1:1 and reverse is 1:4. When there is no input rotation, the output can rotate freely - or it would, if I had a spring or rubber band to get the selector axle back to a neutral position when the motor is off. Unfortunately the hockey spring is far too stiff so I will have to come up with a solution using rubber bands or coil springs. https://bricksafe.com/files/Hrafn/dnr-gearbox/20210712_220047.mp4

Nicely done! What scale is it?

Is there a reason you did it this way instead of putting in a changeover catch? I can't quite tell how all the gears are meshing but won't this tend to disengage on its own when the motor is on?

I love to see South Asian trucks in Lego! Such a wonderful, exuberant sense of color and fun.

Thanks! On further reflection, though, the use of the differential is not really helpful - a basic ratchet transmission achieves the same effect in less space.

Very clever! I love seeing manufacturing processes built in Lego - it makes you aware of how much thought has gone into designing real life manufacturing processes that we take for granted.

A thought occurred to me and I wanted to get it down in rough form to share with others (and see what refinements they come up with). I combined Sariel's two speed ratchet transmission with an old differential to create this drive+neutral+reverse automatic transmission. Input is on the axle running through the 16t gear with chain. Let me know if this has been done before - in retrospect it seems obvious so surely it occurred to someone else.

Thanks for sharing it! I am glad you were able to make it work. It must have been something about my particular prototype that made it lock up.

Looks like I will not get a chance to finish mine any time soon, unfortunately. The latest is here if anyone wants to use it as a jumping off point; it now just lacks a 180 degree limiter for the shift axle. The pictures show it in R; note you can only shift to 1 from here thanks to the blue cross blocks. I am curious to see your dual clutch solution. It seems like you will need separate clutches for both the input and the output, since the half-gearbox that has it's selector at 45 degrees will have two gears engaged simultaneously and will therefore lock up both the input and the output - or have I misunderstood your design? I certainly ran into that problem when I experimented with using 45 degree shifts.

I am still working on the 7+R, albeit very infrequently. How large is too large for use in a supercar? Right now the gearbox is about 15 studs long, 15 wide (11 without structure), and 3 tall, but it is missing the 90 and 180 degree limiters, and a motorized or manual shifter, so it will get bigger. FYI, gear ratios range from 5 (for reverse) to .7 (for 7) in a fairly smooth curve.

Thanks! Yes, that is what I meant by limiters - something to lock the sub gearbox control axles at 90 degree increments and the main control axle at 180 degrees. It occurs to me I could hard couple the sub gearbox control axles with a 45 degree offset (and switch gears by rotating both 45 degrees at a time) but then I would need a precise clutch mechanism to deal with the resulting double engagement during gear shifts.

Sure, but N is easily achieved by just turning the control shaft 90 degrees instead of 180. Controlling that would be tricky though. Thanks! Yes, the old driving rings do save some space. I need to get more old 16z clutch gears, though - the red ones do seem to generate some increased friction.

I am still working on my 7+r but here is an improved version. This is the top view. Red is control, input is green, output is white (barely visible below the red). Here is the bottom view. The shaft with two 20z gears next to each other is for reverse. The two outermost shafts (not counting the reversing one just mentioned) go all the way through the gearbox; the other shafts do not. Returning to the top view: The orange rotary drum on the left controls the R-2-4-6 gearbox, the one on the right controls 1-3-5+7. The gearbox is in reverse here (-12/20). Turning the control 180 degrees clockwise rotates the right rotary drum 90 degrees counter clockwise, and selects the 1-3-5-7 gearbox, so the whole thing is now in 1st gear. Turning the control another 180 degrees clockwise turns the left rotary drum 90 degrees counter clockwise and puts the gearbox in 2. R-2-4-6 has speeds of 12/20, 1, 36/20, 3. 1-3-5-7 has the same speeds except multiplied by 20/14. 20/16 would have given a smoother gear ratio curve but this is more compact, and the relative ratios end up reasonably near what, say, the real Veyron uses. The gearbox still needs limiters and something to prevent shifts from 7 to R, and the structure is still evolving, but hopefully you get the idea.

I don't. There are two layers of gears. The top picture shows the underside. The green input connects to the 24z and 16z, then that axle ends (poorly supported by the black 3x5 L liftarm). The 16 on the input drives half the gray clutch gears, while the 24 drives the 8 on top, which connects to a 16 driving the other half of gray clutch gears. The red clutch gears are all idlers. Each 4 speed half gearbox sends its output to one side of the final pair of clutch gears. In the second picture, which shows the top, the black L liftarms partly obscure the orange rotary drums that drive the half gearboxes. Does that help? I may be able to upload more photos later, hopefully tonight. I also redesigned the whole thing last night on paper (my high tech design tool is graph paper) but can't make any promises that I will get to build it soon - definitely not before mid week, probably later. Also, does anyone have a good 180 degree limiter design? I have ideas for finishing the rest of my gearbox but that part I don't yet have any ideas for. Edit: more photos are on Flickr now. https://www.flickr.com/photos/141598430@N08/ Further edit: now I see there is a superfluous red idler gear near reverse gear.

Here is my proof of concept of a 7+R dual clutch gearbox. It uses two standard 4 speed gearboxes (1, 1.66..., 3, 5), one multiplied by 20/14. The structure is garbage and needs to be overhauled to improve strength and reduce friction, and it needs 2 90 degree limiters, a 180 degree limiter, and two stops to prevent the sub gearbox rotary drums from going from gear 4 to gear 1. And of course it needs a 2L liftarm with a towball in it so the central control axle can trigger the knob wheels alternately as it moves 180 degrees for each gear shift. Ignore the white thin L shaped liftarms, they are holding the control axles steady for a test. Still, the gear arrangement should be correct. Green is input, white is output. The axle with the 14z gears is 4L. I would love to see any improvements you guys can make, especially since my Lego time is very limited at the moment.

I have a sequential 7+R dual-clutch design mostly completely designed, based on your 4-speed designs, but given other commitments I don't know when I will be able to finish and post it ?

Thanks, everyone. For my application space is at a premium and I need to keep everything in this part of the construction at integer-stud spacing, so the 3L worm won't work. I have other options fortunately.

If the 3L worm gear (15457) is placed parallel with and 1 stud above the 7L gear rack (87761), will the gear and rack mesh? Thanks!

Victor, Take a look at this shifter (not my design) with six positions separated by 60 degrees:

You might be able to adapt this one from DurianObried - it's a definite shifter with 6 positions: I've built it and it works very well. Piterx built some 4-position shifters using a shift drum:

Gorgeous and very impressive! I love the shot you have on your Flickr photostream of this with all the other minifig-scale functional vehicles you've built.

It could simply be that they were made in one batch, and the red for that batch was slightly off. Red isn't as bad as yellow or dark red in terms of inconsistent color, but there certainly is some variation in red parts.

I have 3, all different colors (yellow, orange, and black) and they are all very stiff.