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On 6/12/2022 at 4:23 PM, allanp said:

Hope you enjoy and any comments/constructive criticisms are of course welcome.

Looks great.

I would like to see more pictures. Also if possible STEP files to fully understand what's inside.

14 hours ago, allanp said:

@Gimmick not much force to shift. Should be easy to motorise. When I get more time (later this week hopefully) I shall show more of the parts and the indexing mechanism.

Thanks Kbalage 

Would be nice to see, especially under load :D

After thinking a bit about it still seems to be a very "one purpose" part combination - but nowdays with the supercar model...that does not seem like a real argument ^^. Would it be possible to make it extendable with male/female crossaxle connectors?

Some more detail....

The 24 tooth gear is the reverse idler gear.

You will see how I have printed the rotary cams. On the wavy part, I had that facing up in Cura so the wavy geometry was printed with the smooth X and Y axis movements of the printer, this was to minimise any Z layer lines in that area. However because it was printed this way the opposing side is really rough. But that's very simple geometry that just needed a quick rub of a needle file.

The drive rings were the most tricky parts to make as I wanted nice, smooth, accurate surfaces where the selector fork ridge mates with it, and where the clutch gears slot into it. Like the rotary cams, this wouldn't be an issue for proper injection moulded parts, but for this 3D printing noob I had to print them in 3 separate parts and glue them together, aligning them by eye as best as I could.

The drive rings are not very deep, only 1 stud, and much less than that where they engage with the axle extender. The selector forks have a ridge that engages with the drive rings, it's this ridge that helps keep them straight and not bind on the axle engenders.

The axle extenders would normally be a single 3 module long piece with centre stop, like any other 3M axle extender. However, again due to 3D printing, I split them into two 1.5 module halves and omitted the axle stop so they could be slid together onto a 16M long axle. 

The selector forks have a loose fitting cross axle hole. Originally they had a plain round hole but I found that they would slide much better if the sliding surfaces was on the flat sides of the axle as opposed to the rounded outer diameter of the axle. This also allowed me to have a cut out on the underside which provides clearance for the 24 tooth clutch gear. The pin that engages with the rotary cam looks quite small, but as it fully sits within the groove of the rotary cam it is plenty strong enough.

You can also see I made 2 new parts for the indexing mechanism. I wanted to have the rotary cams move to exactly the right place so these pieces allowed for a nice positive stop in exactly the right positions. I'm sure the indexing mechanism could have been done with pre-existing parts, but while I'm making new gearbox parts I thought, what the heck, might as well make things easy for myself. Besides, part of the motivation behind making this gearbox was to make it simpler than TLGs approach, and see how easy I could make it for people to design their own, and incorporate this gearboxes functionality into their own MOCs. While TLGs target audience might be okay with following the instructions for the Sian or the Ferrari, I think they would find it difficult to MOC there own sequential 8 speed gearboxes from the pieces they provide. So I wanted to see if these pieces would make the whole thing much more intuitive and easy to understand, making it much easier to incorporate such functionality into their own MOCs.

I think I succeeded in this regard. Whilst I tried to put a lot of thought and effort into the design of the individual elements, I really didn't have to put much thought into designing the whole gearbox. The parts made it very easy. I just built it while waiting for parts to print.

Hopefully you can get a sense of the force enquired to shift, it isn't very much at all.

This gearbox looks pretty cool.

may I please have the STL files to print this gearbox so I can have a tinker?

Edited June 16, 20222 yr by Jayden

This is great. I suggest you make some nice pictures and it gets frontpaged! It is not Lego Lego but I still would like to see it there :)

 

...and if you ever share the files please let the forum know ;)

Thanks for the detailed video, now I think I understand the whole system. And I have to say those pieces seem already nicely designed, hats off man! Some details are really required to make this work in a tight space, for example I like that the clutch gears have their clutch teeth on the outside, this way it can work for small gears as well. Also that the clutch gears sit on the 3L axle joiner instead of the bare axle, that probably also makes them run smoother. The fork piece is also a really interesting one, I can imagine that it could be sliding smoothly while firmly taking the driving ring with itself, though I am a bit afraid that this may be the weak spot of the system, as that adds an extra step of indirection to the mechanism compared to the Lego wave selector that directly slides the driving ring, and may have enough play that the clutch teeth could disengage under high torque, like in an RC build (though I understand that that indirection is required to make it work in a tight space). It would be great to know how much torque it can take without disengaging.

Also, I like that all the important distances fit onto a regular grid. I wonder if the selector mechanism could be folded downwards to be next to the lower line of gears (it seems that the wave selectors would be right where there are no gears), so the whole thing would fit on a 5x5 module space when viewed from the front (currently it's about 7x5 modules if I am right, not counting that the 24T gear needs slightly more space).

On 6/12/2022 at 10:33 PM, gyenesvi said:

It would be awesome to see only a 4-speed version of this (maybe with 24T, 20T, 16T and 12T gears), but strongly braced, I'd be interested if an XL motor could make its gears skip (which probably also depends on the amount of down-gearig after the gearbox towards the wheels).

Well, here you go! I also moved the shifting components around (so it's all in a 2x2 on centre grid) and made it way less tall than the previous demo.

This is a more compact 4 speed version, using the 12t, 16t, 20t and 24t gears. There is also a neutral position. I am testing it with 2 powered up XL motors with 9V duracell batteries. In 1st gear the gear ratio is a 3:1 reduction, so that's 2 powered up motors geared down 3:1, which is a lot of torque on the 24t clutch gear and drive ring. In 1st gear the piece I used to block rotation kept flying off! The last time it flew off I couldn't find it quickly so that's where the video ends . But yeah, this gearbox is a fully braced version and there's no skipping in any gear. 

I have also messed with the tolerances a little, and it's also not running at a few thousand RPM this time, so now it's very quiet also.

And here's a quick test of changing gears under load:

It works very reliably with a load of 2 white clutch gears. However with 3 white clutch gears it doesn't always want to shift without applying a bit more force that I would feel comfortable with. I suspect this would be improved though with higher quality injection moulded parts rather than FDM 3D printed parts.

Edited June 18, 20222 yr by allanp

6 hours ago, allanp said:

Well, here you go! I also moved the shifting components around (so it's all in a 2x2 on centre grid) and made it way less tall than the previous demo.

Thanks, that's exactly the layout I had in mind (if I am not mistaken, the fork pieces are now on the underside). I guess that's as compact as a 4-speed gearbox can ever get, and it seems solid enough! It would be amazing to test this with injection moulded parts. I wish TLG sometimes made a system based on fans' ideas, this could be a great candidate :) Great work!

35 minutes ago, gyenesvi said:

Thanks, that's exactly the layout I had in mind (if I am not mistaken, the fork pieces are now on the underside). I guess that's as compact as a 4-speed gearbox can ever get, and it seems solid enough! It would be amazing to test this with injection moulded parts. I wish TLG sometimes made a system based on fans' ideas, this could be a great candidate :) Great work!

Also it'd work great on your Jeep Bruiser MOC I guess! 

On 6/16/2022 at 11:34 AM, allanp said:

Some more detail....

THanks, now it's much more clear. I was afraid about selection forks to bend, but it can be seen that you've designed them properly. 

6 hours ago, Mikdun said:

THanks, now it's much more clear. I was afraid about selection forks to bend, but it can be seen that you've designed them properly. 

Yeah I think that was the 4th version of it or something.