This page (https://www.roadrunnerconverters.com/blog/how-automatic-transmissions-work-with-pictures-videos.htm) (and the embedded video in particular) might help clear up how it works. The only thing that's not obvious is which shaft is rotating at the input end, watching it a few times should make it fairly obvious.Great video, explained a lot - thanks for that!
Making the clutches/brakes work properly would, I'd have thought, be the hardest bit, if using a 3D printer...
...Oh. My. That is some SERIOUS Meccano work!
Found this one: https://www.selmec.org.uk/article_0001_ravigneaux_planetary_transmission.aspx (https://www.selmec.org.uk/article_0001_ravigneaux_planetary_transmission.aspx)
Fig.3 shows the number of teeth of the gears, and that's pretty much all, that I need to draw a 3d-model of it.
...
Don, and all, on those old films, they really get to the point without any fuss :praise2:
I watched the M47 video, and there was so much good information, that at least for me, it takes some time to digest it.
What comes to the current gear set that I'm working on, I'm not sure yet, which sun gear is attached to the center axle, and therefore delivering torque from the motor to the rest of the gear sets.
What I suspect, is the 'K' one:
(http://www.elisanet.fi/kz1706/suspected_drive_gear.png)
I'll have to modify the drawings to make room for the'K' to have the grub screw. Not a big deal, as at the beginning, I just wanted to get the gear sets printed out, and while assembling, make changes as is necessary.
Some of the gear sets were way too tight to fit together, so I printed consisting planet gears with 0,1mm offset, to make them rotate more freely.
Hello sorveltaja
Congratulations for getting this far. A noisy three speed and reverse epicyclic gearbox using printed gears is a real achievement. With any Wilson gearbox, all the epicyclic stages spin at different speeds, The speed of the output shaft is dependant on which gear band brake is selected. First and Reverse gears will the worst as the overall reduction is the highest and reverse has a direction change as well. Some of the epicyclic stages will be spinning really fast.
What's you reasoning for going from 1.0 Mod to 1.5 Mod?
My instinctive reaction would be to increase the tooth count to reduce the tooth meshing noise, unfortunately reducing the tooth size also increases the precision required.
It is normal practice to have three planet wheels, instead of just the two. This will have the effect of increasing tooth count as well as improving the load distribution and concentricity of the sun and planets, as they spin inside annulus gears.
Do you have an end use for your epicyclic gearbox or is it simply an exercise in design and 3D printing?
My Merritt-Wilson transmission system was designed for use in a 45Kg 1/6 scale, all metal, model tank (AFV) driven by a 2HP four stroke petrol engine. The Sturmey-Archer bike gear hubs provided the epicyclics for both the Wilson gearbox and for the Merritt double differential track steering. The S-A bike hubs selflessly donated their internal organs for scientific purposes. They proved to be a strong and very robust solution. They were also quite noisy, but then, so is any tank.
Mike
Mike, the reason for going to 1.5 mod was simply to see, how much more there is room to play with offsets. When printing gears, they will not be as accurate as machined ones.
So all kinds of eccentric defects are always present. To overcome that, I increased the tooth size, so there is bit a better chance to avoid the collision of one gear's teeth's outer diameter(slightly eccentric), with other gear's root diameter(also slightly eccentric). I wish I could explain that better.
Instead of just two planet gears, I have added two more. With 21 teeth ring gear, and 7 teeth planet gears, to my surprise, four planet gears seem to fit, or mesh together with sun gear and ring gear.
But I'll have to confirm that, by printing them out first. I have even drawn 1.5 mod helical gearsets, but wouldn't hold my breath for them to be less noisier.
What comes to my take on epicyclic gearbox, It's more like an exercise to realise a model, that could hopefully end up as a usable project for others, that are interested of planetary gearbox, and its magical movements.
Of course, the gear changing mechanism is an open question so far. But I'll get back to that, after I get the gearset problems sorted out.
And Mike, that tank project seems quite interesting :praise2:. What could be better, than putting the four cycle engine, coupled with an automatic transmission to actual use??
Do you have a build blog of that tank?
And thanks for the additional pictures of the Sturmey-Archer gears.
CMD M602 Received.
Control Release.
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Machine Type: Flashforge Finder
Machine Name: Flashforge Finder
Firmware: v2.2.7.299 F2.12.2 20181203
SN: FFF215029
X: 140 Y: 140 Z: 140
Tool Count:1
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~M601 S0
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