tripletschiee

42056 - Porsche 911 GT3 RS - MODs and Improvements

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For the 90 degree limiter, is the 2L liftarm has "+o" holes or "oo" holes?

oo if you use a half pin to avoid the silicon bands from sliding off. I've also seen someone using o+ with a 2L axle running through the + to keep the silicon bands in place. Its important that the 2L liftarms can rotate freely. You should also not squeeze them too tight beteen the 3L perpendicular connectors, otherwise they won't fall back easily. The silicon band(s) should keep the liftarms in position.

Edited by Didumos69

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I have problems with the shifting sequence and the gear ratios ...

I modified the shifting sequence as mentioned by Jim and Crowkillers in Jim''s review, but somehow I think now it has the wrong shifting sequence.

To clearify for me: in first gear, when I push the car, the engine should rotate faster than in any other gear, and in fourth gear, the engine should rotate very slow. Correct? In my opinion, this would be realistic.

Can a gearbox expert tell me the different gear ratios?

Next question is, where is the first gear?

In Jim's review, and in a real car, the right paddle shifts up and the left paddle shifts down. But if I apply the mod for the infinite gear on the right side, I think I start in fourth gear and end in the third ... it would be correct, if I would add the small L-beam on the left side.

Same with Dimudos69 mod, which works really great.

Edited by MegaRoi

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First gear is the slowest, and 4th (in this model, some models have a 6 speed gearbox and others only 4) the highest. :classic:

I don't understand that ...

First gear is the slowest, lowest? Of course, but the engine should rotate more than the wheel axle, correct?

4th gear is the highest, in this model, obviously. But which clutch, left or right, and which position in this model?

Also the shifting sequence. Can someone tell me the correct gear ratios? Maybe with pictures to make it clear?

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MegaRoi check the ORANGE 2L liftarms with linkages. I put 1 in opposite way and became wrong shifting sequence...

Max

Edited by MaxSupercars

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To make it a bit more clear, I added four pictures. Please excuse my mistakes in embedding pictures, I'm still learning ...

In the pictures you can see, that I added the MOD mentioned by Jim to correct the shifting sequence. The red axle connector is the input, while it comes from the rear axle, and the yellow axle connector is the output, while it goes to the fake engine.

image.jpeg

Gear ratio is 1:1,5?

image.jpeg

Gear ratio is 1,33:1?

image.jpeg

Gear ratio is 1:1.

image.jpeg

Gear ratio is 1:1,25?

I'm not good in calculating gear ratios, that's why I'm asking.

In my opinion picture one is fourth gear, picture two, after using the right paddle shifter, is gear one, followed by sencond gear and finally third gear. As MaxsuperCars mentioned two posts later, I made a mistake (Aaarrrrrrrgh!!!), but now it should be correct.

Thanks a lot for the answers,

Robert

Edited by MegaRoi

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MegaRoi you made a mistake in gears left from gear clutches. Check the instructions... 20t and 8t gears are on wrong sides.

Max

Edited by MaxSupercars

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I know why my setup didnt shift properly, it was actually not enough resistance on the output axle.

Strange, but so be it.

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Hi MegaRoi,

Did you update your pictures in post #286 after you corrected the gears?

I asked because I am not able to find which 20t and 8t gear are on the wrong side, when I looked at your pictures and compared it with the instruction.

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I think I solved yet another - probably the last - severe friction problem in the Porsche gearbox.

After getting the gear switching mechanism to work smoothly, there was still one thing bothering me, especially after seeing schraubedrin's video's: The friction inside the gearbox. Just like in schraubedrin's case my build appeared to be especially sensitive to friction in 2nd gear. Even though I could push my build along without any grinding in all 4 gears, the amount of friction kept bothering me.

So yesterday - while I was out road cycling - I tried to get my head around it. I started analyzing and got to the following hypothesis:

Btw, before I got to the actual problem I arrived at a few basic conclusions, just to take away some confusion:

1. In each gear all axles rotate and all gears rotate.

2. In each gear the same number of gears is involved in transferring torque from input to output.

Hypothesis

The two red clutch gears that are not actually involved in one of the two clutches - the ones lined up between the other 16t gears just in front of the actual gearbox (left in the image below) - serve a completely different goal as compared to the 4 red clutch gears that are directly involved in a clutch. The latter ones - when not engaged - simply make dummy rotations, but without transferring drive. Not even to drive another unengaged axle. So even though they have different RPM compared to their axles, they will encounter only little friction. And when these clutch gears are engaged, they get forced to rotate along with the axle in order to transfer torque. So whether engaged or not, there will be hardly any, or even zero friction between the red clutch gear and its axle.

This is not the case for the two red gears lined up in front of the gearbox: There is always one of them involved in transferring drive, while its axle is rotating with different RPM. Now given the way these red gears are lined up between normal gears, the one that needs to transfer drive actually works as a kind of lever and will push itself up or down against its axle. Now taking into account the axle rotating at different RPM, it's easy to understand that this will cause friction.

Some observations: In 4th gear the RPM of the involved red gear is equal to the RPM of its axle (gear / axle RPM ratio is 1:1). However, in 2nd gear the gear / axle RPM ratio is 1:3, which confirms 2nd gear being the most troubled by friction. In 1st and 3rd gear the other red gear is involved. In 1st gear it has a gear / axle RPM ratio of 1:1 and in 3rd gear a gear / axle RPM ratio of 25:9, which is actually almost as severe as with 2nd gear. This aslo explains why 1st gear suffers from less friction than 2nd gear.

640x270.jpg

Resolution

The two red clutch gears not directly involved in one of the two clutches can actually be omitted quite easily. So that's what I did and guess what? It solves the issue completely!!! I don't know if you know how gears sound when they don't suffer from unintended friction. They make this light rattling sound. You can almost hear them being happy with their job. Well this is what I hear now. I even geared up the engine by 300% and it still operates fine. I summarized what I did with a short photo sequence below.

On a side note: As part of earlier modifications (90° limiter and drive train axle scheme) which eliminated double engaged gears I also removed the white clutch gear and surronding gears in front of the gearbox. The white clutch gear served to deal with a halting gearbox and was no longer needed. Due to that removal I had a spare 24t gear and a spare 8t gear left, which I used to gear up the engine. And I used the two 16t gears that came off the back of the engine in the fix below.

640x270.jpg

Photo sequence

Remove the 16t gears from the back of the engine:

800x450.jpg

Collect the extra parts needed (include the two 16t gears from the back of the engine). Also add a 24t gear and a 8t gear:

800x450.jpg?a=1

Take the back of the chassis off (remove two liftarms alongside the bottom of the rear axles) and take the mid-section out of the gearbox:

800x450.jpg

Refactor the mid-section of the gearbox as follows:

800x450.jpg

800x450.jpg

Put the 16t gears in place (make sure they are nicely centered along the 2L axles) and push the mid-section back in place:

800x450.jpg

Put the back of the chassis on again. Make sure each individual axle rotates with minimal friction and the clutch gears have enough play:

800x450.jpg

Gear up the engine:

800x450.jpg

These should be your left overs:

800x450.jpg

And you're Porsche is ready to rock!

Edited by Didumos69

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This seems to be a viable solution for my problem, thanks!

I always assumed this couldn't be the case because i could feel the lockup when applying the slightest force.

The critical point has to be the lower red gear, sitting on the axis of 4th gear. There's the greatest relative movement.

After confusing my friend with my paradoxical gearbox i'll apply your fix and tell you the outcome.

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I didn't plan to buy the Porsche, but I'm almost tempted to just to be able to compare before and after performance. I'm very impressed with all the fixes you guys have come up with!

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The critical point has to be the lower red gear, sitting on the axis of 4th gear. There's the greatest relative movement.

I think so too. My observation was that in 4th gear the RPM of the involved red gear is equal to the RPM of its axle (gear / axle RPM ratio is 1:1). However, in 2nd gear the gear / axle RPM ratio is 1:3, which confirms 2nd gear being the most problematic. In 1st and 3rd gear the other red gear is involved. In 1st gear it has a gear / axle RPM ratio of 1:1 and in 3rd gear a gear / axle RPM ratio of 9:25, which is actually almost as severe as with 2nd gear. This aslo explains why 1st gear suffered from less friction than 2nd gear.

After confusing my friend with my paradoxical gearbox i'll apply your fix and tell you the outcome.

Please do!

Edited by Didumos69

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Resolution

The two red clutch gears not directly involved in one of the two clutches can actually be omitted quite easily.

I think another way to solve this without removing the two red clutch gears is to attach them to the grey frictionless 2L pins.

The latter ones - when not engaged - simply rotate around an axle without doing anything.

I'm afraid that's not accurate. For one red clutch gear next to the changeover catch, even if it's not engaged, it still rotates, and with different speed from its axle, because movement from the engaged clutch gear is transferred back. Check the video, it's Sariel's review when he plugged the motor in.

Edited by nguyengiangoc

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I think another way to solve this without removing the two red clutch gears is to attach them to the grey frictionless 2L pins.

Maybe, but I think supporting gears with 2L frictionless pins is not a good idea in a gearbox. Especially not in a situation where there is a lot of up - or down force on the gear, which is the case in this setup. It's better to have an axle that is supported at both ends. So I would not advice doing that, but you could try of course :wink:

EDIT: Another reason why I would not advice using frictionless pins in this situation: When placed on a 2L pin, the up - and down force will make the gear and pin tilt slightly. Given the fact that the gear is enclosed by a liftarm on one side and a frame on the other side, this tilting will again cause unncessary friction. Especially when you take into account that the red gears measure exactly one stud whereas the normal 16t gears measure a little less than 1 stud, which gives them some play by default. So I wouldn't even bother trying.

Edited by Didumos69

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You know, at first I have no interest in the Porsche, and various reviews discourage me further. But this topic now makes me wanna own this set and apply all the mods to upgrade the set myself. Most of the time I just build models right according to the instructions, but this one really makes me wanna mod. Maybe that is what TLG is after? I mean the feeling of fiddling and finding out and upgrading by yourself.

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You know, at first I have no interest in the Porsche, and various reviews discourage me further. But this topic now makes me wanna own this set and apply all the mods to upgrade the set myself. Most of the time I just build models right according to the instructions, but this one really makes me wanna mod. Maybe that is what TLG is after? I mean the feeling of fiddling and finding out and upgrading by yourself.

That's called Tuning :laugh::thumbup:

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I'm afraid that's not accurate. For one red clutch gear next to the changeover catch, even if it's not engaged, it still rotates, and with different speed from its axle, because movement from the engaged clutch gear is transferred back.

You're right, but that was not what I meant. In fact all clutch gears rotate all the time, or even better, all gears rotate all the time. What I meant to say was that the 4 red gears sitting next to the change-over-catches - when not engaged - simply make dummy rotations, without transferring torque of any kind. Not even to drive another unengaged axle. So even though they have different RPM compared to their axles, they will encounter only little friction, simply because of the absence of the lever effect that the red gears in front of the gearbox are subject to. Hope this helps clarify.

You know, at first I have no interest in the Porsche, and various reviews discourage me further. But this topic now makes me wanna own this set and apply all the mods to upgrade the set myself. Most of the time I just build models right according to the instructions, but this one really makes me wanna mod. Maybe that is what TLG is after? I mean the feeling of fiddling and finding out and upgrading by yourself.

Join the club :wink:. The same happened to me when I was dragged into the speculation topic. I'm actually not into supercars :laugh:

Edited by Didumos69

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I love the work you did on this gearbox Didumos and I'll be sure to implement every single mod you made to this drivetrain. However I can't shake the feeling that with every improvement you make, especially in the short timeframe you actually had the set (have you even build the rest of the model yet? :laugh:), I can't help but return to the question: how come Lego didn't find this in the 3 years they "made" this model??? Was this version of the gearbox made so late in the design phase that they didn't even test it properly? The fact you removed the "use" of the clutch gear completely really makes me wonder if they were trying to reach a deadline and just "slapped that on" as a fix instead of figuring out a proper mechanism that you figured out in a couple of days. Boggles my mind.

Either way, good job making this set rock.

I love happy, frictionless gears as well and could watch that video for hours.

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...

Thank you Appie!

I don't get it either. Sometimes I think they gave us a puzzle on purpose, just to generate buzz and hopefully increased sales. But that would be too much of a gamble.

I did indeed not yet build the rest of the vehicle, haha. I simply can't build something that doesn't feel right, or in this case, feels wrong. I actually had some restless nights because of this.:wink:

This is the first set I bought since I'm out of my dark age and I want it to live up to the euros I spent on it. :wink:

Edited by Didumos69

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Seems to me it would have been better if TLG marketed this set as "incomplete" or something and prompting people who were interested in buying it to come up with solutions to fine-tune the friction problems etc.

At least you'd know what you got instead of buying a set marked as Ultimate only to find a set with numerous friction flaws.

Edited by Error404

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@Didumos69: You're a genius!

I just implemented your changes and it works, it simply works. :sweet:

I'll add the video when my phone and and youtube stopped resisting the inevitable :grin:

Having compared my paddle shifter to my friend's one it seems i'll have to work on this one too :sceptic:

[Edit:] and here's the video:

Edited by schraubedrin

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