9+N+R sequential transmission

[Luke_]

Earlier this year I heard about the Koenigsegg car that LEGO would be releasing, which got me interested in their Lightspeed transmission. 
The transmission I've made isn't quite the same, but still uses the concept of multiplying two 3-speed gearboxes together to achieve 9 gears.

There are three rows of gears. If you ignore the yellow clutch rings for the moment, the top row has a larger spread of ratios (1/2, 1/1 and 2/1) whilst the bottom row is more closely spaced (4/5, 1/1 and 5/4). The middle row of gears links all these ratios together. The input (connected to the engine) is the red clutch gear in the centre of the top row and the output (going to the differential) is the tan axle on the bottom so, in order to get power from the input to the output, one clutch gear from both the top and bottom rows need to be engaged simultaneously. The ratios thus achieved are 2/5 -> 1/2 -> 5/8 ----> 4/5 -> 1/1 -> 5/4 ----> 8/5 -> 2/1 -> 5/2. (The long arrows show when the top row changes to the next gear). This shifting logic is taken care of by the lime green shifter assembly.

The red central shaft is the input controlling the top and bottom shifter pairs with the grey universal joint going to the paddle shifters or similar. On this shaft the knob gear and towball (and the lime green bent liftarm) makes it so that the top shaft rotates one position each time the bottom shaft completes a full rotation. The bottom shaft has three positions, rotating 120 degrees each time in order to cycle through the closely-spaced gear ratios (4/5, 1/1/, 5/4). For the top shaft, the white 1x1 liftarm acts as a stop to prevent going past top gear.

Now I should mention the yellow clutch rings. They are the reverse gear train, only engaged when both ends are selected. You may have noticed that the top shaft of the shifter assembly has four positions, not three. The fourth position selects the reverse gear while the rest is in neutral. When the bottom shaft is in the middle position (as shown in the picture), the bottom row of gears engages both the 1/1 ratio and the reverse gear train. There is only one time both ends of the reverse gear train are engaged.
So the gear sequence is N -> R -> N -> 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9, with stops at both ends.

I feel like I've confused myself typing this out, but it does work in real life! It's as compact as I could make it while keeping the ratios evenly spaced. The engine can fit right above the transmission and it's short enough to be used in 1:8 scale cars. I decided to omit the frame from the pictures so that the function was clearer but I can take some more photos if you want. If you have any questions I'll do my best to answer.

Edited Thursday at 11:08 AM by Luke_
typo

[2GodBDGlory]

Nice work! It's always good to see some gearbox builds on here. I can't say I put in the mental effort to understand fully what's going on there, but I'm glad to see it!

Also, this has got to be one of the only sequential gearboxes I've seen in recent years with a non-wave selector shifting mechanism! Why did you choose to do it that way?

Am I correct in thinking that in some level it's two four-position gearboxes run in series to have sixteen possible positions, with a bunch of the theoretically possible positions blocked off because they aren't necessary?

[Jurss]

Cool.

2 hours ago, 2GodBDGlory said:

with a non-wave selector shifting mechanism! Why did you choose to do it that way?

I suppose, with wave selectors it would be bigger, this way it may be more compact. 

[ginger-snapped]

This is amazingly compact! Really great work. Gonna have to try and build it myself to see it in action and fully figure out how it works.

[JunkstyleGio]

That looks nice. Does it work irl?

[Luke_]

9 hours ago, 2GodBDGlory said:

Also, this has got to be one of the only sequential gearboxes I've seen in recent years with a non-wave selector shifting mechanism! Why did you choose to do it that way?

It's mostly because the lower row of gears needs to cycle through the same three positions, like 123123123. The wave selectors or the shifter drums can't do three evenly spaced positions but the pulley wheel with its 6 pinholes can.
Jurss is correct, I think this solution can be slightly shorter than if I used the wave selectors, also I don't own any!
I was considering using the newer shifter forks and drums but they quickly use up space and are quite expensive. The 12 tooth and 24 tooth clutch gears were pricey enough but I think they're essential enough to include in the design.

9 hours ago, 2GodBDGlory said:

Am I correct in thinking that in some level it's two four-position gearboxes run in series to have sixteen possible positions, with a bunch of the theoretically possible positions blocked off because they aren't necessary?

Hmm I think that's correct, I hadn't thought of it like that ... you're definitely right that I designed it around two gearboxes run in series.

5 hours ago, ginger-snapped said:

This is amazingly compact! Really great work. Gonna have to try and build it myself to see it in action and fully figure out how it works.

Yeah I'm not the best with words, it's probably easier to conceptualise if you build it yourself. I can't count the amount of variations I made trying to squeeze all the pieces in tighter. Over the weekend I'll rebuild it and try to figure out the best frame to post.

29 minutes ago, JunkstyleGio said:

That looks nice. Does it work irl?

It does, mostly dependent on how rigid the frame is. I could probably refine the mechanism that keeps the shifter shafts in position as sometimes it jams if it's rotated too slowly. Also the operation is slightly smoother if the 6L links are replaced with 9L links, but then the whole transmission is longer.

[SNIPE]

Fabulous!

Even trying to make a 6 or 8 speed gearbox makes my head spin

[Luke_]

I took some photos while I built the transmission.
Click on the image to go to the fullsize one on Brickshelf. The image at bottom right shows the makeshift steppers I made. They work surprisingly well! Hopefully it demonstrates visually how the gears are selected.

Edited 15 hours ago by Luke_
typo again